Liquid Phase Alkylation of Benzene with Ethylene

Dalhousie University

Department of Chemical Engineering

Liquid Phase Alkylation of

Benzene with Ethylene

Jeffrey MacDonald Richard Roda Michael Beresford CHEE 4842 Plant Design Date Submitted: April 22th, 2005

ii

Table of Contents List of Figures............................................................................................................................... iv

List of Tables ................................................................................................................................ iv

1 Introduction ....................................................................................................................... 1

1.1 Ethyl Benzene Reaction System.................................................................................... 1 1.2 Methods of Producing Ethyl Benzene............................................................................ 2

1.2.1 Gas-phase Production Using Zeolite Catalysts (Mobil/Badger) ................................ 2 1.2.2 Liquid Phase Production with AlCl3: Friedel-Crafts/Alcar Process.......................... 4 1.2.3 Liquid Phase Reaction Using Zeolite Catalyst in a Fixed Bed (Lummus/UOP EBOneTM)................................................................................................................................ 7 1.2.4 Process Selection ...................................................................................................... 11

2 Process Simulation .......................................................................................................... 12

2.1 HYSYS Simulation Fluid Property Package ............................................................... 12 2.2 Reaction Kinetics ......................................................................................................... 12 2.3 HYSYS Process Flow Diagram .................................................................................... 14 2.4 Section 1: Feed Preparation......................................................................................... 16 2.5 Section 2: Alkylation Reaction and Effluent Cooling.................................................. 19 2.6 Section 3: Benzene and Ethyl Benzene Separation .................................................... 22 2.7 Section 4: Transalkylation........................................................................................... 25 2.8 Section 5: Cooling Water System................................................................................. 27 2.9 Energy Requirement Summary................................................................................... 28

3 Market Survey ................................................................................................................. 29

3.1 UOP Process................................................................................................................. 29 3.2 Styrenics Industry (Nova Chemicals).......................................................................... 29 3.3 Plant Location .............................................................................................................. 30 3.4 Raw Material Availability ........................................................................................... 31

3.4.1 Ethylene20 ................................................................................................................. 32 3.4.2 Benzene .................................................................................................................... 33 3.4.3 Operating Results, 2003 versus 200220.................................................................... 34

3.5 Demand ........................................................................................................................ 35 3.6 Outlook ......................................................................................................................... 36

4 Costs................................................................................................................................. 37

4.1 Equipment Costs.......................................................................................................... 37 4.2 Capital Costs ................................................................................................................ 39 4.3 Direct Operating Costs ................................................................................................ 40 4.4 Profitability .................................................................................................................. 41

5 Environmental Considerations........................................................................................ 43

5.1 Plant Design Considerations ....................................................................................... 43 5.1.1 Greenhouse Gas Emissions...................................................................................... 43 5.1.2 Vapour Flaring ......................................................................................................... 44 5.1.3 Process and Waste Water Treatment: Oily Water Sewer ....................................... 45

5.2 Environmental Regulation: Plant Operation Considerations..................................... 45 5.2.1 Canadian Environmental Protection Act ................................................................ 46 5.2.2 National Pollutant Release Inventory ..................................................................... 47

5.3 ISO Certification .......................................................................................................... 48 5.4 Material Concerns........................................................................................................ 50 5.5 Case Study: Texas Nova Chemical Plant Explosion and Release............................... 51

6 Safety ............................................................................................................................... 52

6.1 Chemical Properties..................................................................................................... 52

iii

6.1.1 Ethylene ................................................................................................................... 53 6.1.2 Benzene .................................................................................................................... 54 6.1.3 Ethyl Benzene .......................................................................................................... 56 6.1.4 Di-ethyl Benzene and Tri-ethyl Benzene................................................................. 58 6.1.5 Toluene ..................................................................................................................... 58 Y-zeolite Catalyst ................................................................................................................. 59 6.1.6 Chemical Property Summary: Explosion Characteristics....................................... 60

6.2 Material Storage .......................................................................................................... 61 6.2.1 Compressed Gas Storage ......................................................................................... 61 6.2.2 Liquid Storage.......................................................................................................... 64 6.2.3 Catalyst Solids Storage............................................................................................ 65 6.2.4 Storage related hazards ........................................................................................... 65 6.2.5 Inherently Safer Material Storage .......................................................................... 66

6.3 Material Transportation .............................................................................................. 67 6.4 Hazard Analysis........................................................................................................... 69

6.4.1 Dow Fire & Explosion Index .................................................................................... 69 6.4.2 Chemical Exposure Index ........................................................................................ 70 6.4.3 Hazard Analysis: What-if......................................................................................... 72

6.5 Case Studies................................................................................................................. 73 6.5.1 Benzene and Ethylene Explosions........................................................................... 73 6.5.2 Short Term Ethyl Benzene Exposure ...................................................................... 75 6.5.3 Long Term Benzene Exposure ................................................................................. 75 6.5.4 Lessons to be learned ............................................................................................... 76

7 Conclusions ...................................................................................................................... 78

8 Recommendations ............................................................................................................ 80

8.1 Process Recommendations........................................................................................... 80 8.2 Safety and Environmental Recommendations ............................................................ 80 8.3 Economical Recommendations..................................................................................... 81

References.................................................................................................................................... 82

References.................................................................................................................................... 82

A. Economics Spreadsheet ................................................................................................... 86

B. Sample Equipment Cost Calculations............................................................................. 88

C. Glossary............................................................................................................................ 90

D. What-if? Analysis............................................................................................................. 91

E. F&EI Sample Calculations .............................................................................................. 94

F. CEI Sample Calculations............................................................................................... 102

G. HYSYS Workbook Output ............................................................................................. 105

iv

List of Figures Figure 1-1: Friedel-Crafts alkylation of Benzene to form EB. ..................................................... 4 Figure 1-5: EBOne process.3........................................................................................................ 10 Figure 2-2: Section 1 feed preparation........................................................................................ 17 Figure 2-3: Section 2 alkylation reactor assembly...................................................................... 19 Figure 2-4: Section 3 benzene and ethyl-benzene separation. ................................................... 22 Figure 2-5: Section 4 transalkylation. ........................................................................................ 25 Figure 2-6: Section 5 transalkylation of DEB............................................................................. 27 Figure 3-1: Styrene/EB plant location (Sarnia, Ont.)................................................................. 31 Figure 3-2: Alberta ethylene cost advantage (¢/lb).70 ................................................................. 32 Figure 3-3: Selling prices for ethylene, benzene, and styrene for 2003-2004.23 ......................... 34 Figure 3-4: Demand for ethyl benzene since 1998 (in millions of kg). ....................................... 36 Figure 4-1: Rate of return as a function of selling price............................................................. 41 Figure 4-2: Relationship of total capital cost and total operating cost as a function of EB

production. ........................................................................................................................... 42 Figure 4-3: Relationship of ROR as a function of EB production for various selling prices of EB

(current = $US 1.12/kg). ...................................................................................................... 42 Figure 6-1: Typical ethylene storage tank. ................................................................................. 63 Figure 2: CEI hazard distance map ............................................................................................ 71

List of Tables Table 2-1: Operation-section key ................................................................................................ 14 Table 2-2: Plant section description. ........................................................................................... 16 Table 2-3: Section 1 conditions.................................................................................................... 17 Table 2-4: Section 2 reactor conditions. ...................................................................................... 20 Table 2-5: Recycle 2 and E2 Inlet stream data. .......................................................................... 20 Table 2-6: Section 4 conditions.................................................................................................... 26 Table 2-7: Energy requirements summary. ................................................................................ 28 Table 3-1: Yearly North American production of EB.25 .............................................................. 36 Table 4-1: Equipment costs (all equipment is carbon steel)....................................................... 38 Table 4-2: Capital costs (EB = 156,000 tonne/yr). ...................................................................... 39 Table 4-3: Direct operating costs (EB = 156,000 tonne/yr)......................................................... 40 Table 4-4: Indirect operating costs (EB = 156,000 tonne/yr)...................................................... 41 Table 5-1: CEPA 200 regulatory limits.32 ................................................................................... 47 Table 6-1: NFPA codes for chemicals used in the production of EB. ......................................... 53 Table 6-2: Ethylene exposure limits.40 ........................................................................................ 53 Table 6-3: Benzene exposure limits data.45................................................................................. 55 Table 6-4: Ethyl benzene recommended exposure limits.49........................................................ 57 Table 6-5: PPE material and break through time.49................................................................... 58 Table 6-6: Important explosion chemical properties for design considerations......................... 61 Table 6-7: Dow F&EI for the EB plant. ...................................................................................... 69 Table 6-8: CEI calculated values................................................................................................. 71

v

Executive Summary

An ethyl benzene plant has been designed using a liquid phase alkylation of benzene

with ethylene. The process is to be implemented at the Nova Chemical styrene plant

in Sarnia, Ontario. Several EB synthesis processes were evaluated: the Mobil/Badger

gas-phase process, the Alcar/AlCl3 liquid phase process, and the Lummus/UOP

EBOneTM liquid phase process. The EBOneTM process was selected as a basis because

it uses a safe and less expensive fixed bed catalyst, moderate operating conditions, and

low benzene-to- ethylene feed ratio.

A benzene-ethylene feed is introduced into an alkylation reactor assembly forming EB

and undesired di-ethyl benzene. A distillation separation system composed of two

columns is used to separate benzene and EB from the main process stream. Benzene is

recycled to the alkylation feed and transalkylation section. The transalkylation reactor

is then used in conjunction with a recycled benzene feed to convert separated DEB to

additional EB. This stream is recycled to the entrance of the separations system. The

HYSYS 3.2 simulation software package was used to model the necessary unit

operations and processes in the EB synthesis process.

Based on the current simulation and a plant capacity of 18,000 kg/h (156,000 tonne/a)

of EB, the plant has a positive net present value of US$ 7.2 million, based on a MARR

of 20% with an IRR of 27%. The plant capital investment is estimated at US$ 23

million, with total operating costs at approximately US$ 160 million. Product revenue

is estimated at US$ 175 million in EB sales, at a current selling price of US$ 1.12/kg.

The vast majority of un-reacted benzene is recycled, and a negligible amount is purged

to tankage. Plant life is estimated at 20 years.

vi

The selling price of EB to turn a profit at a MARR of 20% is US$ 1.09/kg. This was

determined by calculating the effect of EB selling price on rate of return. The effect of

EB production with respect to equipment cost and operational costs was also

determined. The value-added increase in EB selling price is marginal compared to the

benzene cost of US$ 1.05/kg. It is difficult to predict benzene cost as the value has

oscillated in the past 8 months.

Plant capacity is currently at 156,000 tonne/a, comparable to that of the Nova

Chemical plant of 150,000 tonne/a. The benzene-ethylene ratio of 5:1 fed into the

alkylation assembly is too large. An excess of benzene is left un-reacted to cycle

through the recycle streams of the plant. Complications with the HYSYS 3.2 software

makes this change difficult, and other designs may be required to lower this ratio.

This benzene increases reboiler duty costs, column costs, and large amounts of

circulated benzene.

Dow F&EI and CEI analysis indicated the areas of highest risk in the plant. The most

notable area is the alkylation assembly feed, which had a CEI of 1120 and Dow F&EI

of 165. The design must be modified to minimize the amount of hazardous material in

this section of the plant. Decreasing the benzene-ethylene ratio should reduce the

amount of recycled benzene and decrease the overall flow rate into the reactor

assembly.

1

1 Introduction The reaction of benzene with ethylene produces ethyl benzene and by-product di-ethyl

benzene. Ethyl benzene is an intermediate in the production of styrene. Nova

Chemical Corporation has contracted to update their existing ethyl benzene synthesis

process at their styrene plant in Sarnia, Ontario. A declining trend of profitability

resulting from subsequent yearly losses prompted Nova Chemical to evaluate new

technology in the synthesis of ethyl benzene.

There are multiple technologies in current practice in the styrene industry. The

fundamental differences are related to the reaction phase and vessel system. In the

following sections, several methods of ethyl benzene production are explored to

determine which technologies offer the best combination of profitability and inherent

safety.

1.1 Ethyl Benzene Reaction System

The proposed plant design involves creating ethyl benzene from the raw components of

benzene and ethylene. The chemical reaction to create ethyl benzene is:

52564266 HCHCHCHC →+ (1.1)

Eq.(1.1) for the reaction of benzene and ethylene to form EB is accompanied by five

side reactions. Three of them are shown in Eq. (1.2), (1.3), and (1.4).

( )

252464266 HCHCH2CHC →+ (1.2)

( )25246425256 HCHCHCHCHC →+ (1.3)

( )6 6 6 4 2 5 6 5 2 52C H C H C H 2C H C H+ �

(1.4)

2

The reaction illustrated in Eq. (1.2) and (1.3) produces an undesired product, DEB.

Proper use of LeChatelier’s Principle can force the equilibrium reaction described by

Eq. (1.4) to yield as much desired product (EB) as possible. Eq. (1.5) and (1.6) show

two further side reactions, but are negligible for simulation purposes.

73463425256 HCHCCHHCHCHC →+ (1.5)

( ) 523623425256 HCHCCHHCHCHC →+ (1.6)

The kinetics for these two reactions were not found to be documented in literature.

However it has been shown that the reaction extents for both reactions are negligible

when simulating the process.1 As such, Eq. (1.1)-(1.4) shall be used for design in

HYSYS. Several process designs can be implemented to favour the production of EB.

Several methods for creating ethyl benzene are discussed in the proceeding section.

1.2 Methods of Producing Ethyl Benzene

Most production methods of creating ethyl benzene have approximately 95 mol%

conversion.1 The three methods discussed in this report include the creation of ethyl

benzene in the gas-phase reaction (Mobil/Badger), in the liquid phase using an AlCl3

acid catalyst, and a liquid phase reaction in fixed bed reactors using a zeolite catalyst.

1.2.1 Gas-phase Production Using Zeolite Catalysts (Mobil/Badger)

The gas-phase reaction to create ethyl benzene using a zeolite catalyst is referred to as

the Mobil/Badger process. The mechanism for creating EB differs from the AlCl3 and

Alcar process (see Section 1.2.2), since the zeolite catalyst produces a carbonium ion

which activates the ethylene to create an adsorbed electrophilic species which is

quickly attacked by benzene. This in turn causes a faster reaction; however, more by-

3

products are produced as well which have to be recycled and converted back to useful

product using a transalkylator.

Approximate operating conditions are 675-725 K and 200-400 psig. The operating

conditions are significantly higher than those for the liquid phase process, resulting in

higher risk and cost of operation. In addition, the benzene/ethylene ratio is

approximately 8-16 by mole fraction for the gas-phase reaction. Such a large ratio is

needed since the catalyst used is highly deactivated by the presence of ethylene as

more carbonaceous species are created.

Catalyst life using a gas-phase reaction is a major downfall of the gas-phase process.

The catalyst requires regeneration every two to four weeks. To maintain steady state

operation, it is typical to run two reactors in parallel. Because of this, the costs

associated with this process are high as shutdown costs, catalyst costs, and

deactivated catalyst disposal are high. In addition, because the B/E ratio is high, the

costs of operation are higher in order to retrieve and recycle the excess benzene.

The gas-phase reaction does have some positive aspects. The zeolite catalyst is safer

environmentally and disposal costs are not as high. Also, the catalyst is non-corrosive

and therefore special materials, which are required for the AlCl3 and Alcar process,

are not required. However, the catalyst life problem is a major issue with this process.

The AlCl3, Alcar, and liquid process using zeolite catalysts resolve this issue. Figure

1.1 illustrates the operation of a Mobil/Badger process.2

4

1.2.2 Liquid Phase Production with AlCl3: Friedel-Crafts/Alcar Process

One method of creating EB is through a Friedel-Crafts reaction of ethylene in the

presence of an aluminum chloride acid catalyst (AlCl3). This reaction occurs in the

liquid phase and is illustrated in Figure 1-1.

Figure 1-1: Friedel-Crafts alkylation of Benzene to form EB.

Where R = Ethylene group X = Chlorine atom

With this process, the AlCl3 is injected as fine particles into the alkylator reactor

where the ethyl benzene is formed. The AlCl3 is quite often promoted with HCl or

ethylene chloride to reduce the amount of AlCl3 required for the reaction. Once

through the reactor, the AlCl3 is filtered out of the product by water washing and then

sent for disposal or regeneration. To recover the unwanted di-ethyl benzene and other

unwanted products, a transalkylator is commonly used. Here, the unwanted products

are reconverted to EB, hence increasing feed conversion.2

The liquid phase process has several advantages over the gas-phase process because

temperatures and pressures are reduced which lead to saving in operating costs. In

addition, the operation is safer since operating conditions are not as severe. Typical

running conditions for temperature and pressure are between 420-470 K and 70-150

psig for the alkylation and transalkylation processes. In addition, the

benzene/ethylene (B/E) ratio is lower at approximately 1.5-2.5 by mole ratio.

RAlCl3 (cat) R X

-HX

5

Fig

ure 1

-2: M

ob

il/B

ad

ger P

ro

cess

.2

6

Having a lower B/E ratio reduces the operation costs associated with removing the un-

reacted benzene and provides a more economical plant operation.2 Another positive

aspect of the liquid phase reaction is that the catalyst is not subjected to high

deactivation rates. However, this type of catalyst does have some downfalls.

The catalyst used in the AlCl3 process is an acid, which tends to corrode the operating

equipment unless the internals of the equipment are lined with special materials

(such as brick or glass). The use of such materials increase construction costs and may

be expensive to maintain as some are quite fragile. In addition, the catalyst is injected

and removed from the process on a continuous basis, leading to higher operation costs

in water and filtration when the catalyst is separated from the process stream.

Finally, the AlCl3 catalyst is hazardous to the environment and there are relatively

high costs involved in assuring that it is stored and disposed of properly.

Further process designs, such as the Alcar Process from Universal Oil Products (UOP)

resolved some of the downfalls of the AlCl3 process. It used a fixed bed of BF3 catalyst

which had reduced corrosion concerns and eliminated the need for continuous catalyst

removal. However, the Alcar process did require much higher operating pressures of

approximately 500 psig and therefore increasing operating costs. Also, the problem of

the AlCl3 catalyst disposal was also present when using the BF3 catalyst. The AlCl3

and Alcar processes are shown in Figures 1-3 and 1-4, respectively.

Research continues for the use of a zeolite catalyst in a fixed bed for a liquid phase

reaction of ethylene and benzene to create ethyl benzene.2

7

1.2.3 Liquid Phase Reaction Using Zeolite Catalyst in a Fixed Bed (Lummus/UOP EBOneTM)

Similiar to the Mobil/Badger process, the liquid phase reaction uses a zeolite catalyst

which does not require special material for reactor internals, piping, or in other parts

of the process. In addition, the zeolite catalyst is not as harmful to the environment

which saves in disposal costs. There are several patents for this type of reaction,

however, the Lummus/UOP EBOne is the most recent and provides the most benefits.3

This process, like the preceding AlCl3 and Alcar process, requires an alkylator and a

transalkylator. In addition, the operating temperature and pressures are similar to

that of the AlCl3 process. The B/E alkylator feed ratios range from 1.5-2.0 on a molar

basis. Since temperatures and pressures are not extreme and B/E ratios are relatively

low, there are large savings available in operational costs when compared to the

Mobil/Badger process. Further, since the catalyst is contained in fixed beds there are

reduced operational costs when compared to the AlCl3 and Alcar process because the

catalyst does not have to be continuously removed from the process using a filter and

washing.

8

Fig

ure

1-3

: P

ro

du

cti

on

of

EB

usi

ng

AlC

l 3 p

ro

cess

.2

9

Fig

ure 1

-4: P

ro

du

cti

on

of

EB

usi

ng

th

e A

lca

r p

ro

ce

ss.2

10

The most positive aspect of the EBOne process is that catalyst life is claimed to be at

least five years for the alkylator and the transalkylator when using the EBZ-500™

and EBZ-100™ as the fixed bed catalyst, respectively. Also, these catalysts may be

regenerated for at least three cycles. Therefore, they constitute a more economical

alternative to conventional catalyst. Further savings are realized since shutdowns are

less frequent to change out the catalyst in the fixed beds of the reactors. A diagram of

the EBOne process is shown below in Figure 1-5.

Figure 1-5: EBOne process.3

As Figure 1-5 shows, the main reaction takes place in the “Alkylation Section” in the

presence of the EBZ-500™ catalyst in fixed beds. The ethylene and benzene react to

form the product ethyl benzene and other unwanted products. The top product of this

reactor flows to the “Benzene Column” where the excess benzene is removed from the

product stream and then sent back as recycle with “Fresh Benzene”. The remaining

gas is then sent to a “Lights Removal Column” where any un-reacted ethylene is sent

11

to a flaring system. Any un-separated benzene is also combined with the recycled

benzene stream.

The bottoms of the “Benzene Column” are sent to the midsection of the “Ethyl Benzene

Column”. The ethyl benzene product is separated from the other unwanted products

as distillate and then sent to storage. The bottoms of the “Ethyl Benzene Column” are

sent to the mid section of the “Poly-ethyl Benzene Column”. The distillate of this

column is condensed and combined with some recycle benzene and then sent to the

“Transalkylation Section”.

In the “Transalkylation Section” the side reaction (DEB and TEB) products are

reacted in the presence of the EBZ-100™ catalyst in fixed beds to form more ethyl

benzene. The top product of “Transalkylation Section” is then combined with the top

product of the “Alkylation Section”, where it repeats the process loop. The bottom

product of the “Poly-ethyl Benzene Column” is mostly a viscous tar material which is

disposed of as a waste material.

1.2.4 Process Selection

The EBOne process offers the best economical benefits, operating conditions, safety,

and environmental considerations. The EBOne process has been successfully used in

15 fully operational plants with capacities ranging from 65,000 tonne/yr to 200,000

tonne/yr. Five more plants are in the construction phase licensing the EBOne process.

The first plant has being operating at full capacity for 12 years.3 Low operating

conditions, liquid phase reactions, and the environmentally friendly zeolite catalyst

were the primary determinants in selecting this process for a design basis.

12

2 Process Simulation

2.1 HYSYS Simulation Fluid Property Package

The Peng-Robinson property fluid package was used for this simulation. It utilizes the

Peng-Robinson (PR) equation of state model which can be seen in the HYSYS help

manual. It was chosen because the PR model gives good results for non-polar systems,

and has a wide range of materials that can be used for accurate results. All the

components used in the production of EB are either non-polar or contain very weak

dipole moments. It was also noted that HYSYS contained all the necessary interaction

parameters for the PR EOS model, which sharply improves accuracy.

2.2 Reaction Kinetics

Kinetics for the “Alkylation Section” are taken from Qi and Zhang (2004)1. The

kinetics takes into account the use of zeolite catalyst. The reaction of benzene with

ethylene to produce the product ethyl benzene is as follows:

52564266 HCHCHCHC →+ -5 1.0 0.32

1 E B-45.8r =8.4×10 exp( )C C

RT (2.7)

The reaction of benzene with two moles of ethylene to produce di-ethyl benzene is as follows:

252464266 )H(CHCH2CHC →+ -4 1.3 0.33

2 E B-61.6r =6.03×10 exp( )C C

RT (2.8)

The reaction of ethyl benzene with ethylene to produce di-ethyl benzene is as follows:

25246425256 )H(CHCHCHCHC →+ -7 1.77 0.35

3 E EB-86.4r =8.5×10 exp( )C C

RT (2.9)

The three kinetic equations above have the units of kgmole/m3s. The activation

energies given in Qi and Zhang (2004) did not contain information on units. A second

source indicated that the units were kcal/mol.7 The results of a conversion of the

activation values into kJ/kgmol are shown above in Eq. (2.7)-(2.9). The equilibrium

13

reaction of benzene with di-ethyl benzene to form two moles of ethyl benzene is as

follows:

( )6 6 6 4 2 5 6 5 2 52C H C H C H 2C H C H+ �

( )EQ

276.6ln K = -0.3599

T (2.10)

The reactions for the “Transalkylator Section” were modeled using the equilibrium

expression in Eq. (2.10). These were derived using thermodynamic assumptions

described in literature.8 The equilibrium constant can be related to temperature using

the following expression:

( )o

�H 1 1Kln =- -K R T T

� �� ′ ′� �

(2.11)

Where

K = Equilibrium constant at temperature T

K′ = Reference Equilibrium constant at temperature T’

�H° = Standard enthalpy change of reaction

T = Arbitrary temperature T′ = Reference temperature at value of Equilibrium constant K

The reference temperature and equilibrium constant were given in Qi and Zhang

(2004). These values had a K value of 0.883 and a T value of 571 K.1 The standard

reaction enthalpy was determined using HYSYS as -2.4x103 J/mol. Manipulation of

Eq. (2.11) and substituting the appropriate values in for variables yields Eq. (2.10).

In the following section, a detailed description of the simulation in HYSYS will be

presented discussing each major unit operation with its function, parameters such as

height, diameter, required work/duty, etc.

14

2.3 HYSYS Process Flow Diagram

Figure 2-1 shows the HYSYS process flow diagram in its entirety. There are 14 main

process operations contained in five sections of the plant. Table 2-1 summarizes the

PFD labels of these operations with descriptions of the equipment and the section of

the plant in which they are contained. Table 2-2 shows a summary of each of the five

sections of the plant.

Table 2-1: Operation-section key

PFD Label Operation Description Plant Section

P-1 Fresh benzene feed pump to Alkylator

Section 1

E-1 Alkylation Feed Cooling Water Heat Exchanger

Section 1

P-2 C-1 Recycle Pump Section 1 R-1-1A/R-1-2A Train One Alkylation Section Section 2 R-2-1A/R-2-2A Train Two Alkylation Section Section 2 R-1-1B/R-1-2B Train One Equilibrium Reactor Section 2 R-2-1B/R-2-2B Train Two Equilibrium Reactor Section 2

VLV-100 Alkylation Effluent Pressure Reducer

Section 2

E-2 R-1 Assembly Effluent Cooling Water Heat Exchanger

Section 3

C-1 Benzene Separation Column Section 3 C-2 EB Separation Column Section 3 C-3 Flash Drum Section 3 E-3 C-2 Bottoms Cooling Water

Heat Exchanger Section 4

R-3-1A Transalkylation Alkylator Section 4 R-3-1B Transalkylation Equilibrium

Reactor Section 4

15

Fig

ure 2

-1: H

YS

YS

sim

ula

tio

n P

FD

.

16

Table 2-2: Plant section description.

Section Number

Brief Description

Section 1 Feed preparation section of the plant. Its purpose is to prepare the feed components for the reactions in Section 2.

Section 2 Alkylation section of the plant which is divided into two trains of reactors. The purpose of this section is to form ethyl benzene from ethylene and benzene raw components. It contains four real reactors, a reducing valve and an effluent cooling water heat exchanger.

Section 3 Benzene and ethyl benzene separation section of the plant. It contains two distillation columns and a flash drum.

Section 4 Transalkylation section of the plant. Converts some of the diethyl benzene to ethyl benzene using C-1 benzene recycle

Section 5 Cooling water section of the plant. It provides the plant with the required cooling water needed in the distillation columns, reactor cooling jackets, and the three cooling water heat exchangers.

A detailed description of each section is discussed in the following sections.

Operating conditions, performance, design specifications are discussed in

further detail.

2.4 Section 1: Feed Preparation

The purpose of this section of the ethyl benzene plant is to prepare the feed

components for processing in Section 2 of the plant where the alkylation

reaction occurs. This section handles a large recycle benzene stream which is

combined with the raw feed components.

Section 1 of the EB plant includes the fresh feed streams of benzene and

ethylene, the benzene feed pump (P-1), the benzene recycle pump (P-2), and

17

the R-1/R-2 assembly feed heat exchanger (E-1). The raw ethylene arrives on

site from a pipeline which operates at approximately 4 MPa and is reduced to

1.8 MPa before entering the main plant. The feed and recycle are mixed then

cooled using a cooling water shell and tube heat exchanger (E-1). The tube

side of the exchanger contains the cooled product which then proceeds to

Section 2 for alkylation. A HYSYS schematic of this section is shown in

Figure 2-2.

Figure 2-2: Section 1 feed preparation.

Table 2-3 summarizes the composition, operating conditions, and flow rates

for the important streams.

Table 2-3: Section 1 conditions.

Fresh

Benzene

Ethylene Raw Feed

E-1-Inlet Train-Feed

Recycle Feed

Temperature [°C] 25 268 90 40 83

Pressure [kPa] 101 1800 1800 1780 1800

Mass Flow Rate [kg/h]

14,500 4769 78,530 78.530 59,260

Benzene Mole Frac. 0.99 0.0 0.83 0.83 0.98

Ethylene Mole Frac. 0.00 1.0 0.17 0.17 0.02

18

To pump the fresh benzene to the reactor conditions of 1.8 MPa, the pump

requires 10.5 kW of power when running at 75% efficiency. In order to

prevent catalyst deactivation, the feed ratios of the benzene/ethylene (B/E

ratio) are adjusted using a spreadsheet (Feed Ratios and Reactor

Calculations) to a value of 5.5 on a molar basis. This ratio may be reduced

further to approximately 1.4 by the addition of more ethylene. However the

HYSYS simulation became unstable for any attempts to decrease the ratio. If

this ratio is decreased any further than 1.4, the deactivation of the zeolite

catalysts in the R-1 assembly becomes a major issue requiring the shutdown

of the R-1 reactor for catalyst re-activation or worse, replacement.1 It should

be noted that increasing this ratio in HYSYS drastically improved the

benzene conversion, however HYSYS does not take catalyst deactivation into

account, and as such, the simulation is bound to this constraint.9 The desired

B/E ratio from the reactor inlet steam (Train Feed) is controlled in the

HYSYS simulation through a spreadsheet (“Feed Ratios and Reactor

Calculations”).

The E-1 heat exchanger is simulated with a complex shell and tube heat

exchanger. The process stream flows on the tube side of the exchanger and

the cooling water passes through the shell side. Heat integration was not

possible however, since no heating is required in the simulation other then

the re-boilers in the distillation columns (where heat integration is not used).

19

2.5 Section 2: Alkylation Reaction and Effluent Cooling

Section 2 of the ethyl benzene plant consists of a benzene/ethylene alkylation

reactor assembly which forms the product compound of ethyl benzene and

other by-products such as diethyl benzene. The assembly is divided into two

trains, Train 1 and Train 2. Each train consists of two CSTR reactors and two

equilibrium reactor models to simulate the non-reversible and equilibrium

reactions, respectively, represented in Eq. (2.7)-(2.10). The overall purpose of

this section of the plant is to facilitate a reaction to produce ethyl benzene at

the highest yield and level of safety as possible. A schematic of this section of

the plant is illustrated in Figure 2-3.

Figure 2-3: Section 2 alkylation reactor assembly.

The two trains are identical to each other in terms of mass flow rate,

pressure, temperature, and composition. Table 2-4 summarizes the process

20

details for each reactor while the conditions for the Recycle 2 and E2 Inlet

stream can be seen in Table 2-5.

Table 2-4: Section 2 reactor conditions.

R-1-1-A/ R-2-1

R-1-1B-Liq/ R-2-1B

R-1-2A/ R-2-2A

R-1-2B R-2-2B

Temperature (°C) 125 125 138 138 Pressure (kPa) 1700 1700 1700 1700 Mass Flow Rate (kg/h)

39,210 39,210 39,210 39,210

Benzene Mole Frac. 0.870 0.822 0.837 0.821 Ethylene Mole Frac. 0.073 0.073 0.021 0.021 EB Mole Frac 0.00 0.096 0.107 0.14 DEB Mole Frac. 0.056 0.0081 0.034 0.017

Table 2-5: Recycle 2 and E2 Inlet stream data. Recycle 2 E2 In

Temperature (°C) 20 115

Pressure (kPa) 500 500

Mass Flow Rate (kg/h) 22,540 100,000

Benzene Mole Frac. 0.846 0.826

Ethylene Mole Frac. 0.007 0.018

EB Mole Frac 0.135 0.016

DEB Mole Frac. 0.012 0.016

The volume of each CSTR model is approximately 35m3 , which are ordered in

series for both trains as illustrated in Figure 2-3. Realistically, a reactor

reaches its size limit around 250 m3. The reactor volume had a negligible

effect on the benzene conversion. HYSYS encountered some difficulties in

performing accurate case studies to optimize the reactor volumes. However,

21

35m3 was the smallest volume to which HYSYS would converge without

giving inappropriate results.

At steady state, the R-1 assembly runs at 125°C and 1700 kPa in which there

is a 13°C exotherm in the second R-1 of each train. These process conditions

are based on U.S. Patent 6,504,071 and most conditions fall within the

proposed ranges.10 To improve heat efficiency of the plant, the reactors were

allowed to provide more exotherm instead of using large amounts of energy to

cool the reactant contents. The reactor outlets are cooled just enough to

maintain them in the liquid phase. As a result, the reactant outlets do not

require heating to become a saturated liquid before entering C-1. Since

cooling water is cheaper then steam this more economical.

E-2 was simulated using a complex shell and tube heat exchanger. The

process stream flows in the tube side of the exchanger and is cooled by water

passing through the shell side of the exchanger. Again heat integration was

not possible as there are no process streams that require heating other than

the re-boilers of the distillation columns.

In order to obtain a respectable life of the EBZ-500TM catalyst, the B/E ratio

must be maintained as high as possible in order to keep ethylene as a

limiting reagent, and therefore limiting its interaction with the catalyst and

22

causing deactivation. As previously stated, the deactivation of the catalyst

increases operational costs in the forms of increased shutdowns and catalyst

replacement and regeneration. However, this ratio must also be kept as low

as possible to prevent high separation cost of benzene in C-1.

2.6 Section 3: Benzene and Ethyl Benzene Separation

Section 3 of the ethyl benzene plant consists of two distillation columns (C-1

and C-2) and a flash drum (C-3). This section of the plant is used to separate

benzene and ethyl benzene from the main process stream. A schematic of this

section of the plan is shown in Figure 2-4.

Figure 2-4: Section 3 benzene and ethyl-benzene separation.

23

The benzene separation occurs in C-1 in which the distillate stream is 99.7%

benzene (m.f.). A portion of the distillate proceeds to C-3 for flaring and to

provide benzene to the transalkylation section. This is accomplished by

invoking a 40 kPa pressure drop allowing some of the process stream to flash

off. The remainder is recycled back to the feed section of the plant for further

reaction in the R-1 assembly. The bottoms of the column proceed to C-2 for

further separation. Process details of C-1 inlets and outlets are detailed in

Table 2-6 and the process details of C-3 can be seen in Table 2-7.

Table 2-6: Section 3 C-1 process data.

C-1-Feed C-1-Distillate C-1-Liquid

Temperature [°C] 107 83 194

Pressure [kPa] 470 400 400

Mass Flow Rate [kg/h] 101,000 79,470 21,470

Benzene Mole Frac. 0.083 0.976 0.051

Ethylene Mole Frac. 0.018 0.022 0.001

EB Mole Frac. 0.139 0.002 0.848

DEB Mole Frac. 0.016 0.0 0.100


Out-4 Benzene to

Tankage

Benzene to Transalk

Temperature [°C] 83 82 82

Pressure [kPa] 400 360 360

Mass Flow Rate [kg/h] 19,820 47 19,770

Benzene Mole Frac. 0.977 0.311 0.991

Ethylene Mole Frac. 0.022 0.689 0.007

EB Mole Frac. 0.002 0.00 0.002

DEB Mole Frac. 0.00 0.00 0.00

24

C-1 is approximately 16.3 m high, has a diameter of approximately 3.4 m,

and contains 27 actual trays (assuming a tray efficiency of 60%). The feed

stage is on tray number 19, where the column is numbered from top to

bottom. C-1 removes 99.5% of the benzene from the process stream. The

reflux ratio is 15.8 and the column has a pressure drop of 70 kPa.

The bottoms of C-1 are sent to C-2 where ethyl benzene is separated from

diethyl benzene. C-2 is approximately 20.3 m high, has a diameter of 2.3 m,

and contains 33 trays assuming 60% tray efficiency. C-2 removes 99.9% of the

ethyl benzene from the process stream. Table 2-8 illustrates the process

details of C-2. The distillate stream of C-2 is the product stream of ethyl

benzene while the bottoms of the column are mainly diethyl benzene which is

transalkylated to produce more diethyl benzene product.


C-2-Distillate C-2-Liq

Temperature [°C] 185 240

Pressure [kPa] 360 360

Mass Flow Rate [kg/h] 18,770 2700

Benzene Mole Frac. 0.042 0.0

Ethylene Mole Frac. 0.0 0.0

EB Mole Frac. 0.978 0.007

DEB Mole Frac. 0.0 0.993

Table 2-8 shows a summary of the design specifications of C-1 and C-2.

25

Table 2-8: Section 3 C1 and C2 design summary.

C-1 C-2

Height (m) 16.3 20.3

Width (m) 3.4 2.3

Number of Actual Trays (60% Efficiency)

27 33

Reflux Ratio 0.7 2.1

Re-boiler Duty (kW) 16 5

Condenser Duty (kW) 16 5

Feed Stage 11 19

2.7 Section 4: Transalkylation

Section 4 of the EB plant design is the transalkylation reaction section. A

diagram of this section is shown in Figure 2-5.

Figure 2-5: Section 4 transalkylation. Approximately 23,000 kg/h enters the transalkylator. A breakdown of the

stream components are shown in Table 2-6.

26

Table 2-6: Section 4 conditions. Component E-3-Out (mol %) R-3-1B-Liq (mol %)

Benzene 90.7 80.4

Ethylene 1.7 0.3

EB 0.2 17.4

DEB 7.2 1.9

Toluene <0.0001 <0.0001

The Transalkylator (R-3-1A & R-3-1B) makes use of the equilibrium and

CSTR models. Equilibrium kinetics were described in Eq. (2.11).

Approximately an 83% conversion of EB to DEB was obtained. Conditions for

the transalkylation section were not described in the supporting

documentation for EB production. However, a paper documenting the

transalkylation reaction of EB to form benzene and DEB operates their

transalkylator at high temperatures (400-600 K).11 Since the reverse is

required for this plant design, it is logical that lower temperatures are

required for the reaction to produce EB. This is supported by inspection of

Eq. (2.10). The transalkylation process is independent of pressure, and as

such there is no reason to lower the pressure when it will need to be

increased again for the recycle loop.12

The reactor has been sized at 30 m3. The simulation did not converge at lower

volumes, and the conversion achieved at higher volumes was negligible. The

bottoms of C-2 is mixed with the benzene recycle and cooled to 25°C and

maintained at 360 kPa. A larger proportion of DEB is desired to increase the

27

amount of EB formed, however this is related to the high benzene-ethylene

ratio entering the R-1/R-2 assembly. There is too much unreacted benzene

circulating the recycle streams, and not enough ethylene is present to

increase the amount of EB and DEB formed.

2.8 Section 5: Cooling Water System

Section 5 of the EB plant consists of the upper and lower cooling water

headers for the plant. Figure 2-6 shows the upper header inlet and lower

header.

Figure 2-6: Section 5 transalkylation of DEB.

Cooling water at 22°C and 100 psig enters the upper header and exits the

plant at 55°C and 100 psig. Approximately 633,000 kg/h of cooling water is

required. The outlet temperature was determined to be below 60-70°C to

avoid scaling issues. An inlet temperature of 22°C was selected based on an

average seasonal temperature.

28

2.9 Energy Requirement Summary

The energy requirements for the plant are summarized in Table 2-7. It is

readily apparent that the largest utility costs are the condenser and re-boiler

of the columns C-1 and C-2. Steam is used for the re-boiler requirements as

the temperatures are not unrealistically large. Relatively low pressures are

used in the plant resulting in low pump costs.

Table 2-7: Energy requirements summary.

Energy Stream Unit Power Req. [kW]

P-1-D P-1 10

P-2-D P-2 40

E-1 E-1 -2,150

R-1-1A-D R-1-1A -110

R-1-1B-D R-1-1B -34

R-1-2A-D R-1-2A 490

R-1-2B-D R-1-2B -10.5

R-2-1A-D R-2-1A -110

R-2-1B-D R-2-1B -34

R-2-2A-D R2-2A 490

R-2-2B-D R-2-2B -10.5

E-2 E-2 -415 C-1-CD C-1 16,000 C-1-RD C-1 16,000 C-2-CD C-2 5,000 C-2-RB C-2 5,000

E-3 E-3 853 R-3-1A-D R-3-1A -128 R-3-1B-D R-3-1B -25

P-3-D P-3 1.5

29

3 Market Survey

Over 99.9% of the ethyl benzene produced in the world is used in the

manufacture of styrene. Therefore, the demand for ethyl benzene is

determined primarily by styrene production.16 EB is also used in the

manufacturing of industrial solvents and, on occasion, in the production of

diethyl benzene, acetophenone and ethyl anthrax-quinone.

3.1 UOP Process

In 1996, UOP and Lummus successfully commercialized a new zeolitic EBZ-

500 catalyst for the alkylation of benzene with ethylene to produce EB.19 The

first commercial plant to use the liquid-phase process began production in

1990 by the Nippon Styrene Monomer Corporation (Japan). The plant used

the UOC-4120 zeolite catalyst manufactured by UOP for both the alkylation

and transalkylation reactors. Two subsequent plants were constructed in

Japan in 1994, this time, using the newly developed EBZ-100 transalkylation

catalyst. By 1997, full-scale plants were using EBZ-500 (the catalyst proposed

for the current project) in South-East Asia, Japan, and Germany.

3.2 Styrenics Industry (Nova Chemicals)

Styrene is produced from ethyl benzene, which in turn, is made from benzene

and ethylene. All of the ethylene and a significant portion of the benzene

requirements for the styrene facility in Sarnia are supplied from the

30

Corunna, Ontario olefins facility. The remaining benzene feedstock is

purchased from nearby petroleum refineries.20

Nova’s global styrenic polymer feedstock requirements are presently met

through internal styrene monomer production and long-term supply

arrangements. For locations in Europe requiring styrene, Nova uses a series

of trans-Atlantic arrangements with other producers (at local-producer

economics). Three separate acquisitions of styrenics assets from ARCO

Chemical Company, Huntsman Corporation and Shell Petroleum Company

Limited in 1996, 1998 and 2000, respectively, resulted in Nova being net

sellers of styrene monomer.20

Current styrene monomer production capacity, together with long-term

supply contracts, exceeds Nova’s annual requirements for styrenic polymer

production by 500 million kg. In a tight market, this allows for maximum

styrenic polymer sales. It also allows for the sale of scarce monomer at high

prices in the spot market. However, when demand for styrene and

polystyrene diminish, excess styrene monomer must be sold at low spot

prices, straining profit margins.

3.3 Plant Location

The geographical location of a plant can play a pivotal role in the design of a

plant. When considering a location, many variables must be considered before

31

a conclusion can be drawn on the best site. Although, there can be major

environmental aspects to be concerned with, the major factor is for the most

economical location such as the availability of raw materials and ambient

temperatures. 13

The Nova Chemicals styrene plant is located in Sarnia-Lambton's Chemical

Valley, about 230 km west of Toronto, Ontario. Figure 3-1 depicts a map of

the location with respect to several of the Great Lakes and Detroit, Michigan.

The Sarnia site supplies styrene to Nova Chemicals' Montreal, Quebec and

Springfield, Massachusetts polystyrene operations as well as other

commercial operations in North America and Europe.21

Figure 3-1: Styrene/EB plant location (Sarnia, Ont.).

3.4 Raw Material Availability

As discussed in Section 3.2, all ethylene feedstock is obtained from Corunna,

as does the majority benzene feed. Both arrive on-site via pipeline. The

balance benzene is purchased from local plants.

32

3.4.1 Ethylene20

Nova Chemical owns two ethylene facilities in Canada. The major plant is

located in Joffre, Alberta and accounts for 75% of their total ethylene

production. The remaining 25% is manufactured at the Corunna, Ontario

olefins plant in a flexi-cracker. All ethylene plants at Joffre use ethane as

their primary feedstock. Natural gas is purchased to replace the energy loss

due to the extracted ethane from the gas stream.

The Joffre site is the largest ethylene complex in the world and runs more

economically than its similar counterparts in the US. In 2003 and 2002, this

advantage was approximately $0.09/kg, down from about $0.11/kg in 2001,

and down from a 14-year historical average of $0.13/kg (Figure 3-2). In 2002

and for most of 2003, excess supply reduced the price for ethane relative to

natural gas on the U.S. Gulf Coast (USGC) and caused the cost advantage to

decline. In the second half of 2004, demand for ethane began to improve on

the USGC and for 2004, the average ethylene advantage increased to

$0.15/kg. This results in a feedstock cost of $0.48/kg.

Figure 3-2: Alberta ethylene cost advantage (¢/lb).70

33

The ethylene plant in Corunna has the flexibility to switch part of its

feedstock slate between natural gas liquids and crude oil derivatives,

depending on market conditions. Feedstock decisions are made by using a

model that calculates the most profitable mix of end products that can be

produced from the optimal feedstock slate.

3.4.2 Benzene

A worldwide shortage of benzene, combined with strong demand for the key

raw material has sent prices skyrocketing in 2004. Prices have more than

doubled to record highs of $4.25 per US gallon for spot product and $3.95 per

US gallon for contract benzene earlier this year. Current benzene price is

approximately $3.50 per US gallon ($1.05/kg).

Rapidly increasing benzene pricing (see Figure 3-3) could hurt the US styrene

market, however, exports have been strong enough to maintain production.

Export pricing on styrene monomer does support these higher benzene levels,

especially since ethylene and natural gas prices have moderated. Currently,

US styrene demand has been unremarkable.22

34

Ethylene (US contracts; cts/lb)

0

5

10

15

20

25

30

35

40

45

Oct-03 Nov-03 Jan-04 Mar-04 Apr-04 Jun-04 Aug-04 Sep-04 Nov-04 Dec-04

Styrene (US spot; cts/lb)

0

10

20

30

40

50

60

70


Benzene (US spot; $/gal)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5


Methanol (US spot;cts/gal)

0

10

20

30

40

50

60

70

80

90

100


Figure 3-3: Selling prices for ethylene, benzene, and styrene for 2003-

2004.23

3.4.3 Operating Results, 2003 versus 200220

Nova’s styrenics business results declined in 2003, bringing their net loss to

$130 million from a $102 million loss in 2002. Price increases implemented

throughout 2003 kept pace with rapidly rising feedstock costs but were more

than offset by higher natural gas-based utilities and distribution costs, as

well as the negative impact of the outage on the Bayport, Texas styrene

monomer facility. As feedstock costs increased in the fourth quarter of 2003,

and continued to rise in early 2004, styrene prices continue to increase. These

price increases were announced for styrene monomer and the full slate of

styrenic polymers in both North America and Europe. The price increased by

$0.07-$0.13/kg between December 2003 and March 2004. Implementation of

announced price increases depends on many factors, including market

conditions, the supply/demand balance for each particular product and

feedstock costs. Price increases have varying degrees of success. They are

35

typically phased in and can differ by product or market. Benchmark price

indices sometimes lag behind price increase announcements due to the

timing of publication. Revenues increased $274 million, or 21%, from $1,305

million in 2002 to $1,579 million in 2003 due to pricing improvement and

strong styrene monomer sales.

3.5 Demand

The current global market is stable for styrene, but is poised to tighten

considerably, owing to a significant number of turnarounds planned for the

first two quarters of 2004. A possible roadblock to any run-up in styrene is its

main feedstock benzene, which has seen its price rise because of higher

energy costs (as discussed in Section 3.4.2).24

North American demand for ethyl benzene is shown in Figure 3-4. The

market is still recuperating from the substantial decrease in demand in 2001,

but is expected to increase to six billion kg by 2007.15 Current North

American production is shown in Table 3-1, and speculates that there is

presently more ethyl benzene being produced than the market can support.

36

$5,858

$6,119 $6,128

$4,819

$5,554$5,434

4000

4500

5000

5500

6000

6500

1998 1999 2000 2001 2002 2003

Dem

an

d (

mil

lion

s of

kg)

Figure 3-4: Demand for ethyl benzene since 1998 (in millions of kg).

Table 3-1: Yearly North American production of EB.25

Producer Capacity

[millions of kg/yr]

BP Chemicals, Texas City, TX 500

Chevron, St. James, LA 800

Cos-Mar, Carville, LA 1,000

Dow, Freeport, TX 850

Huntsman, Odessa, TX 150

Lyondell Chemical, Channelview, TX 1,350

Nova, Bayport, TX 650

Sterling, Texas City, TX 900

Westlake, Lake Charles, LA 150

Nova Chemicals, Sarnia, Ont. 430

Total 6,780

3.6 Outlook

Ethyl benzene’s market growth depends highly on the demand for styrene. At

current rates, the demand for styrene is growing globally at about 5%

annually.15 However, growth in North America is only expected to increase by

37

2% in the long term. Accordingly, ethyl benzene is only expected to increase

by 2%.

World demand for ethyl benzene in 2001 was about 23 million metric tons.

Overall ethyl benzene demand will increase at an average annual rate of

4.6% from 2001 to 2006 (or 3.4% from 2000 to 2006), resulting in global ethyl

benzene demand of about 29 million metric tons in 2006. Consumption is

expected to grow the fastest in the Middle East and South America.16

4 Costs

The current NPV of the plant is US$ 7 million. This value is based on the

assumed 20-year life of the plant and a MARR of 20%. A new process

technology is considered a medium level of risk, which corresponds to an

MARR between 16-24%.14 The discounted rate of return (ROR) was

determined to be 27%.

4.1 Equipment Costs

Equipment costs have been calculated for the current plant design based on

available data from Peters and Timmerhaus.14 Estimated purchasing and

installation costs are shown in Table 4-1. For economical reasons, carbon

steel was selected for equipment construction. Carbon steel has suitable

corrosion resistance for the chemicals used in the production of EB.14

38

Total purchasing costs in 2004 amount to US$ 3.6 million and total

installation costs are US$ 2.3 million. The two distillation columns (C-1 and

C-2) account for the largest portion (60%) of the equipment costs.

Table 4-1: Equipment costs (all equipment is carbon steel). EB = 156,000 tonne/yr

Equipment Description Purchase

Cost, US $

Install Cost, US $

Cost Formula Ref

(P&T)

CSTR (R-1) 35 m3; CS jacketed; 300 psia

121,800 54,800 21,000(V)0.529 p. 628

CSTR Motor (R-1) 35 m3 2,600 1,200 30.08(V)P =

380(P)0.53

p. 520


121,800 54,800 21,000(V)0.529 p. 628

CSTR Motor (R-1) 35 m3 2,600 1,200 30.08(V)P =

380(P)0.53

p. 520


121,800 54,800 21,000(V)0.529 p. 628

CSTR Motor (R-1) 35 m3 2,600 1,200 30.08(V)P =

380(P)0.53

p. 520

Pump (P-1) 16 m3/h 5,600 2,400 0.36)v2,048( � p. 519

Pump Motor (P-1) 10 kW 1,300 600 380(P)0.53 p. 520

Pump (P-2) 68 m3/h 9,300 4,000 0.36)v2,048( � p. 519

Pump Motor (P-2) 39 kW 2,600 1,100 380(P)0.53 p. 520

Pump (P-3) 26 m3/h 6,600 2,800 0.36)v2,048( � p. 519

Pump Motor (P-3) 2 kW 500 200 380(P)0.53 p. 520

Separator 3.3 m3 33,400 15,000 0.6715,000(V) p. 864

Heat Exchanger (E-1) 26.9 m2 8,279 3,312 1,290(A)0.565 p. 682



Dist Col (C-1) 3.4 m diameter; 27 trays; 16.3 m height, � = 0.6

1,051,200 788,400 1,230(D)1.39 × Ntray 4,050(D)1.39 × H

p. 794

Condenser (C-1) 59E6 kJ/h; 212 m2

104,800 78,600 )�TQ/(1500A L×=

7,400(A)0.70

p. 682

Reboiler (C-1) 59E6 kJ/h; 713 m2

245,100 110,300 �T)Q/(4000A ×=

7,400(A)0.70

p. 682

39

Dist Col (C-2) 2.3 m diameter; 33 trays; 20.3 m height, � = 0.6

977,300 733,000 1,230(D)1.39 × Ntray 4,050(D)1.39 × H

p. 794

Condenser (C-2) 18E6 kJ/h; 242 m2

115,100 86,300 )�TQ/(1500A L×=

2,470(A)0.70

p. 682

Reboiler (C-2) 18E6 kJ/h; 368 m2 154,100 69,400

�T)Q/(4000A ×=

2,470(A)0.70 p. 682

Totals (2002) 3,345,000 2,178,000 M&S = 1117 Totals (3Q 2004) 3,576,000 2,328,000 M&S = 1194

4.2 Capital Costs

The capital costs for the preliminary plant design are shown in Table 4-2.

The capital cost includes equipment, materials, labour, indirect construction

costs, engineering, and contingencies. The total capital investment was

estimated at US$ 23.7 million or $US 150/tonne-yr.

Table 4-2: Capital costs (EB = 156,000 tonne/yr).

Item Factor Cost, US $ Reference

Equipment - 3,576,100 - Installation - 2,328,100 P&T, p. 244 Instrumentation 0.36 (E) 1,287,400 P&T, p. 251 Piping 0.68 (E) 2,431,700 P&T, p. 251 Electrical 0.11 (E) 393,400 P&T, p. 251 Building 0.18 (E) 643,700 P&T, p. 251 Yard 0.10 (E) 357,600 P&T, p. 251 Service facilities 0.70 (E) 2,503,200 P&T, p. 248 (Land) 0.06 (E) 214,600 P&T, p. 176 Total Direct Plant Cost (excl. _land)

13,521,100

-

Engineering 0.33 (E) 1,180,100 P&T, p. 251 Construction 0.41 (E) 1,466,200 P&T, p. 251 Legal Expenses 0.04 (E) 143,000 P&T, p. 251 Contractors Fees 0.22 (E) 786,700 P&T, p. 251 Contingency 0.44 (E) 1,573,500 P&T, p. 251

Total Indirect Plant Cost 5,149,500 - Fixed-Capital Investment 18,670,700 - Start-Up Expense 0.10 (FCI) 1,867,100 P&T, p. 340 Working Capital 0.89 (E) 3,182,700 P&T, p. 251 Total Capital Investment 23,720,000

($150/tonne-yr) -

40

4.3 Direct Operating Costs

The projected direct operating costs are summarized in Table 4-3. Since

catalyst is purchased once every five years, an annual equivalent rate was

calculated. Approximately 96% of the annual cost is associated with the raw

material; 83% of which is benzene.

The indirect operating costs, or fixed costs, are represented in Table 4-4. The

projected total operating costs (direct and indirect) for the EB plant is

estimated at US$ 160.2 million, or US$ 1,030/tonne.

Table 4-3: Direct operating costs (EB = 156,000 tonne/yr).

Item Rate Basis Cost ,

US $/yr Reference

Benzene 14,200 kg/yr 1.05 129,717,000 Ref 23 Ethylene 4,770 kg/yr 0.484 20,081,900 Ref 23 Catalyst 43,500 kg/5yr 0.05 12,400 Ref 26 Power 50 kW $0.055/kwh 24,000 Ref 27 Water 633,000kg/yr $8E-6/kg (20°C) 44,100 P&T, p. 266 Steam

4,160 kg/yr $7.70E-3/kg (P=100psia) 2,769,000 P&T, p. 266

Labour - $25/h 2,175,000 P&T, p. 265 Supervision 0.15 (L) - 326,300 P&T, p. 270 Maint. & repair 0.07 (FCI) - 1,306,900 P&T, p. 266 Oper. Supplies 0.15 (M&R) - 196,000 P&T, p. 268 Labour supplies 0.15 (L) 326,300 P&T, p. 204

41

Table 4-4: Indirect operating costs (EB = 156,000 tonne/yr).

Item Basis Cost, US $/yr Reference

Taxes 0.015 (FCI) 280,100 P&T, p. 269 Insurance 0.01 (FCI) 186,700 P&T, p. 269 Overhead 0.60 (L+S+M) 2,284,900 P&T, p. 270 Administration 0.20 (L) 435,000 P&T, p. 270 Indirect Operating Costs 3,186,700 - Total Operating Costs 160,165,700

($1,030/tonne) -

4.4 Profitability

The current plant design is economically viable. Figure 4-1 shows the

expected rate of return as a function of the selling price of ethyl benzene at

the current EB selling price of $1.12/kg.71 Note that all other variables (e.g.

purchasing price of raw material) are held constant in the calculation. Figure

4-1 indicates that EB can be sold for $1.02/kg to break even and $1.09/kg to

meet the MARR of 20% based on the current production.

0

10

20

30

40

50

60

70

80

90

100

0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8

Selling Price of EB ($)

Ra

te o

f R

etu

rn (

%)

Current = $1.12/kg

ROR = 27%

Figure 4-1: Rate of return as a function of selling price.

Figure 4-2 shows the relationship of total capital cost (TCI) in $/tonne-year

and total operating cost (TOC) in $/tonne as a function of EB production. At

42

the current production rate of 156,000 tonne/yr, the TCI and TOC are

approximately $US 150/tonne-year and $US 1,030/tonne, respectively.

50.0

70.0

90.0

110.0

130.0

150.0

170.0

190.0

210.0

110,000 120,000 130,000 140,000 150,000 160,000 170,000 180,000

EB Production (tonne/yr)

$ T

CI/

ton

ne-y

ea

r

0.0

200.0

400.0

600.0

800.0

1,000.0

1,200.0

$ T

OC

/to

nn

e

Total Capital Investment Total Operating Cost

Total Capital Investment

Total Operating Cost

Figure 4-2: Relationship of total capital cost and total operating cost as a function of EB production.

Figure 4-3 shows the relationship between ROR and ethyl benzene

production for various selling prices of EB.

0

5

10

15

20

25

30

35

40

45

50

50,000 70,000 90,000 110,000 130,000 150,000 170,000 190,000 210,000 230,000 250,000EB Production (tonne/yr)

RO

R (

%)

Current Rate = 156,000 tonne/yr

$1.20/kg

$1.15/kg

$1.12/kg (Current Price)

$1.10/kg

$1.05/kg

Figure 4-3: Relationship of ROR as a function of EB production for various selling prices of EB (current = $US 1.12/kg).

43

5 Environmental Considerations

The following sections discuss general environmental considerations that

should be made during the design phase of the EB process.

5.1 Plant Design Considerations

There are two main concerns that should be taken into consideration for the

plant design and costing: green house gas emissions and waste water

treatment.

5.1.1 Greenhouse Gas Emissions

It is expected that steam shall be generated from the combustion of natural

gas. This natural gas shall be bought within Nova Chemical’s pipeline near

Sarnia. Combustion of the natural gas will produce greenhouse gas emissions

that will have to be treated or separated if emissions do not meet the

regulation guidelines. Two possibilities for managing CO2 emissions are CO2

sequestration versus CO2 capture and storage.

Carbon dioxide sequestration is the natural act of CO2 storage in nature in a

sink. A sink, defined by the United Nations Framework on Climate Change,

is a process, activity, or mechanism which removes a greenhouse gas from the

atmosphere. There are three main sinks: biospheres (oceans and forests),

44

geological formations (coal beds and active or depleted oil and gas reservoirs),

and material sinks (wood products, chemicals, and plastics).

Carbon dioxide capture and storage is an industrial process to capture CO2

from a waste stream and either direct it to a natural sink or store it for

industrial use. Modern industry dictates that the safest and most reliable

sink is to store CO2 in natural gas and oil reservoir. Based on the current

steam requirements for the plant, it is possible that a significant amount of

natural gas will be needed to supply the energy requires for the process.28

The greenhouse gasses released from combustion must be either captured or

sequestered.

5.1.2 Vapour Flaring

The vent gas from column C-1 that cannot be recovered will have to be

vented. An alternative is to flare the gas. Flaring the gas will burn the

released ethylene and benzene, producing CO2. While this may increase the

amount of CO2 exiting the plant, a high efficiency flare can reduce or

eliminate the release of benzene and ethylene through the stack.

It is important to ensure that the flare gas does not contain liquid droplets,

as they will not necessarily combust upon exit from the plant. The release of

benzene is of most concern, as it may exit as liquid droplets in the vent gas. It

must be ensured that a high efficiency flare system is designed, along with

45

other preventative measures such as a scrubbing section to eliminate other

vent gas impurities. A centralized vent system could be designed around the

plant equipment such that vent gases exit a common flare system. This could

work barring any unforeseen chemical issues, such as unwanted reactions in

the vent system or explosion concerns.29

5.1.3 Process and Waste Water Treatment: Oily Water Sewer

Design of a waste treatment facility integrated into the plant design is

extremely important for both environmental and safety reasons. Rainwater

run off, waste water, process water, and sewage from the plant must all be

specially treated. Dumping this into a municipal sewer without treatment is

illegal. Process water used for heating and cooling must be treated before

release into the environment. This includes temperatures and concentrations.

One hazard associated with oily water sewers is H2S release. Hot process

water containing dissolved H2S enters the sewer system, and as the

temperature drops, H2S gas is released as a result of a decrease in solubility.

This can poison plant employees and release into the environment. Design

must take this into consideration.30

5.2 Environmental Regulation: Plant Operation

Considerations

Environmental regulations govern many aspects of a plant design.

Regulations put restrictions on effluent concentrations of hazardous

46

substances, enforce penalties for environmental misconduct, and enforce

equipment design constraints. Environmental regulation is a hot topic in

Canada. The ultimate governing body for Canadian environmental issues is

Environment Canada.

5.2.1 Canadian Environmental Protection Act

CEPA is a legal document describing the environmental regulations enforced

by Environment Canada.31 It covers a wide range of topics from emission

guidelines to hazardous chemical inventories to procedural safety

requirements. While analysis of the document in its entirety is not required

at this time, the most notable guideline from the act is outlined in CEPA 200.

CEPA 200 is a regulation that requires companies to report to Environment

Canada concerning the chemicals outlined in the act that break concentration

and storage threshold limits proposed by CEPA 200.32 For the purposes of

this plant design, it will be necessary to establish this relationship with

Environment Canada. Regulation thresholds are detailed in Table 5-1 for the

chemicals present in the production of EB.

It is interesting to note that DEB was not present in the regulatory list. This

may be because it is generally considered an undesirable byproduct. It is

expected that the threshold limits will be breached and as such, detailed

reporting will be required as prescribed by CEPA 200.

47

Table 5-1: CEPA 200 regulatory limits.32

CAS # UN # Molar Conc.

[%]

Threshold Storage Quantity [tonnes]

Benzene 71-43-2 1114 1.0 10

Ethylene 100-41-4 1175 1.0 7000

EB 74-85-1 1038 & 1962 1.0 4.5

Toluene 108-85-3 1294 1.0 2500

5.2.2 National Pollutant Release Inventory

The National Pollutant Release Inventory (NPRI) is a standardized method

of facilitating the documentation and reporting of pollutant release. It is a

legal requirement for companies to follow the NPRI reporting system subject

to a specific detailed list of criteria33:

• Facility size, capacity

• Employee hours, conditions (over 20,000 h per year threshold)

• Substance criteria subject to NPRI chemical listings

o Part 1A Substances – Core substance list since inception

o Part 1B Substances – Includes mercury, arsenic, cadmium, lead

etc. (Toxic metals concentrated by human interaction with the

environment)

o Part 2 Substances – 17 Polycyclic aromatic hydrocarbons

(PAH’s)

o Part 3 Substances – Dioxins/ furans and hexachlorobenzene

(HCB)

48

o Part 4 Substances – Criteria air contaiminants (CAC’s)

o Part 5 Substances – Special volatile organic compounds VOC’s

If any one of the criteria is met, then an NPRI report is required. The NPRI

also provides a standard for reporting substance releases. The legal basis for

the NPRI reporting is covered under Section 46(1) of the Canadian

Environmental Protection Act (CEPA).31 Further CEPA requirements involve

the creation of emergency action and prevention plans, procedural safety

plans, and occupational health and safety committees / systems. An example

of such a program standard is the NFPA 1600 Standard form emergency

disaster management.34

All main process chemicals used in this plant fall under Part 1A. The

threshold limits outlined in CEPA 200 determine whether reporting is

required. It is expected that NPRI reporting will be required for this plant

once in operation.

5.3 ISO Certification

Nova Chemical is an ISO 9001:2000 company. Most ISO (International

Standards Organization) standards are designed for specific engineering

applications. The ISO 9000 and 14000 standards families are generic

management system standards. They deal with customer quality

requirements, complying with regulations, and environmental objectives.

49

The ISO 9000 standard family is a standard centered on quality

management, and provides a standard definition for product quality. It

removes the subjective nature of company policy and quality control by

creating a set of standards and definitions. It also describes in detail a

general quality management system that can be incorporated into any

process.35 This management system, already in place at Nova Chemical

Corporation, is an important model for ethyl benzene quality control and

plant condition quality. It will be the basis for the quality control team

stationed at the Sarnia styrene plant.

The ISO 14000 environmental management standards family is designed to

minimize the harmful effects of a plant or company on the environment. It

encompasses standards based on the fundamental principles of Plan, Do,

Check, Act. These are:36

• Prioritizing environmental aspects (Plan)

• Integration of environmental aspects in design and development (Plan,

Do)

• Communicating environmental performance (Do)

• Monitoring environmental performance (Check)

• Monitoring system performance (Check)

50

• Program improvement (Act)

Both ISO 9000 and 14000 are designed around the principles of Plan, Do,

Check, and Act. These methods are generic to all business practices and are

not specific to any one process. Since Nova Chemical is an ISO 9001:2000

certified company, business practices and quality control should already be a

company standard, and as such, focus should be directed to the

implementation of ISO 14000. It is recommended that these standards should

be used to design plant environmental management systems in conjunction

with NPRI reporting and company procedural safety techniques.

The health and explosion hazards presented by the aromatic compounds and

ethylene warrant the formulation of a strict environmental control policy,

which will include procedural safety measures for materials reception,

storage, and handling; emergency response protocol, employee training and

educational programs; and environmental testing protocol. These represent a

fraction of the necessary programs required to satisfy the ISO 14000

standards family criteria.

5.4 Material Concerns

As mentioned in the Plant Safety section, the chemicals used in this process

present significant human health hazards. Benzene, EB, DEB, and toluene

are also toxic to plants and animals. Furthermore, benzene can contaminate

51

ground water and soil. EB and DEB degrade over a span of three days;

however benzene takes a much longer time to degrade in soil. Through

implementation of ISO 9000 and 14000, programs shall be created for

material control and environmental protocol regarding material safety and

environmental policy.

5.5 Case Study: Texas Nova Chemical Plant Explosion and

Release

On June 11th 2003, a fire broke out at the Nova Chemical plant in Bayport,

Texas. The heat from the fire ruptured pipes carrying EB. The EB ignited,

causing an explosion that sent EB soaring into the air and damaged

surrounding equipment.

The limited knowledge available concerning the effects of EB on the human

body made remediation difficult. Several workers were exposed to high levels

of EB, causing skin irritation, redness, and swelling. The surrounding area,

close to several residential complexes, was contaminated with low levels of

EB.

Late testing done by Nova Chemical indicated that there was no EB soil

contamination. Independent testing indicated that not only were there levels

of 34 ppb above the regulation soil contamination limit, but the soil also

52

contained significantly higher levels of benzene, which is much more

dangerous. Nova Chemical failed to comment on these findings.37,38

The Nova Chemical explosion illustrates the need for proper substance

reporting and appropriate environmental management. Failure to provide

information on soil sampling in the allotted time cost Nova Chemical $25,000

per day until they were released. Legal costs and losses in production

contribute to losses in revenue. Proper reporting and hazardous inventory

accounting could have prevented the release of benzene into the surrounding

community. An environmental management system, such as that proposed by

the ISO 14000 standard, could be useful in conjunction with NRPI reporting

to act as management related loss prevention and mitigation.

6 Safety

The following sections address health and safety concerns associated with the

inherent properties of all process chemicals, chemical storage hazards, and

chemical transportation.

6.1 Chemical Properties

The chemicals involved in the production of EB carry safety and health

concerns intrinsic to their properties. Descriptions of each chemical and their

role in the process are outlined in the following section.

53

6.1.1 Ethylene

Ethylene is a colorless gas with a sweet odor at standard temperature and

pressure, and a chemical formula of C2H4. Ethylene is extremely flammable,

with lower and upper explosion limits of 3.1% to 32.0%, lower and upper

flammability limits of 2.7% and 36.0%39, and is considered a simple

asphyxiant. Its boiling point is -103.0°C. Table 6-1 shows NFPA hazard codes

for the chemicals used in the plant.

Table 6-1: NFPA codes for chemicals used in the production of EB.

Hazard Codes NFPA Hazard

Category Ethylene40 Benzene42 EB47 DEB51 Toluene53 Rating Key

Health 0 2 2 2 2

Flammability 4 3 3 2 3

Reactivity 0 0 0 0 0

0 = No Hazard 1 = Slight 2 = Moderate 3 = Serious 4 = Severe

A summary of exposure limits from various organizations are outlined in

Table 6-2.

Table 6-2: Ethylene exposure limits.40

Exposure Limit Value / Description

OSHA-PEL Simple Asphyxiant

ACGIH-TLV-TWA (8h) Simple Asphyxiant

Carcinogen? No

LD50/LC50 No Effect Ethylene is not toxic nor is it carcinogenic. There are no minimum

concentrations to report other than to ensure that an oxygen concentration of

54

19.5% is maintained to prevent asphyxiation. There are three main safety

concerns with ethylene:

• Flammability

• Gas compression

• Asphyxiation

This raises issues of fire prevention and suppression, explosion protection,

compressed gas storage, and health concerns in the event that there is an

ethylene leak. Ethylene gas leaks could cut off oxygen to plant workers,

causing severe injury or death. Compressed gas requires specific storage and

handling procedures, while fire fighting systems must be installed that can

effectively deal with an ethylene explosion or fire.40 Water spray and fog

techniques supported by alcohol resistant foam, dry chemical, and CO2 are

acceptable as fire suppression media.

6.1.2 Benzene

Benzene is a clear liquid at standard temperature and pressure, and

produces an aromatic signature odor.41 It has an aromatic ring structure with

a chemical formula of C6H6. Benzene vapours are flammable and will ignite

at lower and upper explosion limits of 1.0% to 6.7%, and a flammability range

of 1.3% to 7.1%. It has a boiling point of 80.9°C, so vapourization can occur if

the temperature becomes too high. The NFPA hazard codes for benzene are

displayed in Table 6-1.

55

Benzene poses extreme health hazards to plant workers if not properly

contained. It is carcinogenic and attacks the central nervous system.43

Moderate periods of exposure can cause cancer (leukemia). It can enter the

body through inhalation, ingestion, and skin absorption. Benzene has a very

high absorption rate through the skin.44 Table 6-3 outlines the exposure

limits and classifications for various occupational health and safety

organizations.

Table 6-3: Benzene exposure limits data.45

Exposure Limit Value/ Description

OSHA-TLV-TWA (8h) 1.6 mg/m3 (0.5 ppm) A1-Skin

OSHA-STEL 8 mg/m3 (2.5 ppm) LDLo 50 mg/kg (oral/man) LD50 930 mg/kg (oral/rat) LC50 10,000 ppm / 7 hour (inhalation/ rat) LD50 2,890 µg/m3 (intraperitoneal / rat) Dose: 20 mg/ 24h/ Skin/ Rabbit – moderate irritation

Dose: 2 mg/ 24h/ Eye/ Rabbit – Severe Irritation

ACGIH Group A1 Carcinogen

IARC Group 1 Carcinogen

NTP Group 1 Carcinogen

IRIS EPA Class A Carcinogen

OSHA Group X Carcinogen It should be noted that the odor threshold for benzene is 12 ppm, much

higher than the recommended exposure limits. 46 An employee could work in

an environment above the recommended exposure limit without knowing that

hazardous quantities of benzene were in the atmosphere. Benzene raises two

major safety concerns:

• Flammability

• Worker exposure / health risks

56

Fire prevention and suppression techniques will be important as flames can

travel along the vapour trail above liquid benzene to the source, such as a

storage tank. Dry chemical, alcohol resistant foam and CO2 extinguishing

media should be used. Water is only effective for cooling the source. The

severe impact of benzene on the human body means that strict procedures,

proper PPE, and minimizing exposure will be extremely important when

handling the chemical.42

6.1.3 Ethyl Benzene

Ethyl benzene is a clear colorless liquid at standard temperature and

pressure, and produces an aromatic smell, similar to benzene. Its chemical

formula is C6H5C2H5. Apart from a higher boiling point of 136°C, it has very

similar properties to benzene. It is insoluble in water and has similar

flammability limits of 1.0% to 6.7%. EB, like benzene, is stable and non-

reactive. The NFPA hazard codes for EB are displayed in Table 6-1.

EB is extremely hazardous to human health from prolonged exposure. It is

carcinogenic, attacking the central nervous system.48 Aspiration may cause

pulmonary edema and hemorrhage. Skin absorption rate is high, causing

skin irritation, reddening, blistering, and dermatitis. EB can also cause sister

chromatid exchange. Table 6-4 outlines some occupational health and safety

exposure limits. It is important to note that the odor threshold is well below

57

the recommended exposure limits. The level at which one can detect the odor

is much less than the recommended threshold limit, so employees can detect

leaks before they reach harmful levels.

Table 6-4: Ethyl benzene recommended exposure limits.49

Exposure Limit Value/ Description

ACGIH-TLV-TWA (8h) 100 ppm (434 mg/m3) ACGIH-STEL (15min) 125 ppm (543 mg/m3) NIOSH REL (10 h TWA): 100 ppm

STEL (15 min): 125 ppm

OSHA-PEL-TWA (8h) 100 ppm

Air Odor Threshold 2.3 ppm EB poses similar identifiable hazards to benzene:

• Flammability


Fire suppression techniques should be installed in the event of an EB fire. EB

fire suppression requires CO2, alcohol-resistant foam, or dry chemical

extinguishers. Water may be used to cool the area near the source of the fire.

Larger fires may also be controlled using water spray or fog techniques.

Proper PPE must be worn. Specific materials must be used for PPE, as

degradation can occur rapidly. The table below shows various materials and

approximate time for degradation of PPE material. EB should be kept away

from heavy oxidizers to prevent violent reaction. EB shall be handled in a

similar fashion to benzene within the plant.

58

Table 6-5: PPE material and break through time.49

Material Breakthrough Time

[h]

Barricade >8

Viton >8

Teflon >4

Butyl Rubber <1

Natural Rubber <1

Neoprene <1

Nitrile Rubber <1

Polyethylene <1

Polyvinyl Alcohol <1

Polyvinyl Chloride <1

Saranex <1

6.1.4 Di-ethyl Benzene and Tri-ethyl Benzene

DEB and TEB chemical properties are similar to EB. Both are flammable and

can cause serious health problems to humans.50 Their boiling points

marginally increase as more ethyl groups are added to the benzene ring.

Fire hazards and health risks shall be handled in a similar fashion to EB and

benzene. The hazards of adding more ethyl groups to the benzene ring to

create EB, DEB, and TEB seem to decrease slightly, while boiling points

increase.

6.1.5 Toluene

Toluene is an aromatic compound with similar characteristics to benzene. It

has similar LFL-UFL limits (1.0%-7.0%) and a wider LEL-UEL range (3.3%-

19.0%). Due to the added functional group attached to the benzene ring, it

59

has a higher boiling and flash point (111°C and 7°C).52 The NFPA hazard

codes for toluene are displayed in Table 6-1.

The most notable risks associated with toluene are the same as benzene:

• Flammability


Mitigation of toluene fires requires similar strategies to benzene fires.

Carbon dioxide, alcohol-resistant foam, and dry chemical extinguishers are

all required for smaller fires. Water will not be useful for direct fire

extinguishing, however it can be used to cool the fire source to augment

suppression techniques. A water mist or fog can be used for larger fires to

suppress vapours.54

Toluene presents the same health risks as benzene. The IARC warns that

toluene has cancer causing properties. The carcinogenic properties of toluene

attack the central nervous system of the body, with multiple points of entry.43

Toluene is present in minimal amounts within the plant, as it is considered

an impurity in an almost pure benzene mixture. As such, it does not pose a

large hazard relative to benzene in the mixture.

Y-zeolite Catalyst

The Y-zeolite catalyst used for the alkylator and transalkylator are the EBZ-

500 and EBZ-100 catalysts, respectively. The nominal diameter of the

60

spherical catalyst particles is 2.2 mm. It has a density of 740 kg/m3 and does

not contain any precious metals. The catalyst does not pose any safety

hazard. It is inert in storage and the dust explosion risk is minimal. The

catalyst is stored in 210 L steel drums in a cool dry area. Substances such as

water, oxygenates, olefins, chlorides, and sulfur poison the catalyst. The

catalyst has a long cycle length of 3 to 5 years per regeneration, and can last

for three regeneration cycles.55 The y-zeolite catalysts from UOP are safe and

environmentally friendly, thus the risk associated with storage and use is

minimal.

6.1.6 Chemical Property Summary: Explosion Characteristics

Certain chemical properties have a direct impact on process planning and

design. Table 6-6 shows a summary of explosion-related properties of the

major chemicals present in ethyl benzene production. Table 6-6 is useful for

identifying chemicals that may require significant safety allowances due to

the likelihood of an explosion or fire. For all practical purposes in the

production of EB, ethylene is a gas. In conjunction with a wide explosion limit

range, ethylene has the greatest explosion risk.

61

Table 6-6: Important explosion chemical properties for design considerations.

Substance

Boiling Point [°C]

Flash Point [°C]

LFL-UFL [%]

LEL-UEL [%]

Vapour Pressure [mmHG] @ 20°C

Ethylene -103.7 - 2.7-36.0 3.1-32.0 -a

Benzene 80.1 -11.0 1.3-7.1 1.0-6.7 166.5

Ethyl benzene 136.2 18.056 1.0-6.7 1.0-6.7 7.1

Di-ethyl benzene

180.0 58.0 0.8-6.0 0.8-6.0 1.1b

Toluene57 111.0 7.0 1.0-7.0 3.3-19.0 22.0 a…above critical pressure b…value determined at 25°C

Storage will also be an issue, as there are requirements for compressed gas

storage, which has its own set of problems, as outlined in Section 6.2. The

properties in Table 6-6 and the health risks associated with each substance

shall be used to design material storage and transportation schemes.

6.2 Material Storage

Substance storage is divided into three major groups: compressed gas

storage, liquid storage, and catalyst solids storage.

6.2.1 Compressed Gas Storage

Ethylene is non-corrosive, so most building materials are acceptable for

storage tanks, provided they are non-combustible in the event of an explosion

or fire. The construction should be designed such that not only could the tank

store ethylene under high pressure, but could reduce risk in the event of

explosion though an inherently safer and stronger design. The electrical

62

system should be non-sparking and explosion proof. All lines associated with

the ethylene system should be earth grounded and bonded to minimize the

risk or leaks or pipeline ruptures leading to explosion. Check valves or traps

should be installed in the discharge line to prevent backflow of unwanted

materials.40 This may eliminate the possibility of oxygen entering the tank,

increasing the possibility of ignition or fire.

Ethylene should be stored in a well ventilated, cool, dry area. Storage in

excess of 54°C is not recommended, and a pressure regulator should be used

when connecting to systems or piping below 2000 psig.40 Smaller gas

cylinders should be stored in areas of low traffic, and appropriately chained

to a fixed structural element in the event of yoke or valve rupture. Cylinder

valves should be designed to break at an opening of no more than 0.75 cm.

This limits gas leak velocity and reduces the likelihood a gas cylinder will

become airborne.58

Based on material properties, ethylene is stored as a compressed gas or in

cryogenic storage. An industrial storage tank designed by Universal

Industrial Gases, Inc., is seen below in Figure 6-1.

63

Figure 6-1: Typical ethylene storage tank.

This vessel can store between 6,000 to 80,000 gallons, and stores ethylene

between 75 and 175 psig59. Industrial ethylene is cryogenically stored as a

liquid60. It should be noted that at 175 psig, ethylene must be kept below -

43.0°C to be stored as a liquid.

Cryogenic ethylene storage systems designed by Larsen & Toubro Limited

store ethylene at atmospheric pressure and -104°C (saturation temperature)

using R-22 as a refrigerant. Tanks are insulated and double walled using

concrete and other non-combustible materials. A water-foam fire fighting

system can be installed for fire suppression. A flare can be installed for the

proper incineration of escaping vapours. A DCS (Distributive Control System)

is generally implemented for control over tank operations such as tank

loading, discharge, and conditions such as temperature and pressure. An

64

explosion barrier was installed as an engineered safety device to help protect

surroundings against explosion.61

For this project, an ethylene system would be designed or subcontracted to

companies such as Larsen & Toubro Limited or Universal Industrial Gases

Limited. Tank construction cost, inert gas material costs, and energy costs for

the cryogenic refrigeration system would have to be taken into account.

6.2.2 Liquid Storage

Benzene and ethyl benzene are both liquids at room temperature. While

specific information on industrial storage of benzene could not be obtained,

general considerations for designing a benzene storage system shall be

discussed.

Benzene and ethyl benzene must be stored in a cool, dry area. It is important

that the area is well ventilated to decrease the likelihood that vapours could

accumulate. It is extremely easy for benzene vapours to accumulate into an

explosion air mixture. Inerting a storage tank with nitrogen can be used to

decrease oxygen concentrations in the tank and reduce the likelihood of

explosion or fire.62

Another common problem with benzene is accumulation of static charge.

Agitated benzene and EB mixtures can accumulate static charge. This

65

charge, if allowed to increase, can ignite benzene vapours and cause an

explosion. Lower temperatures or chemical additives to increase conductivity

can be used to dissipate charge. Minimal agitation also helps to prevent

charge build up. Reducing the flow rate in transfer operations as well as

incorporating longer residence times in piping can make the process

inherently safer by reducing static charge build up.63

6.2.3 Catalyst Solids Storage

Data on catalyst properties and storage was difficult to obtain as most of the

information is highly proprietary. It is known however that the Y-zeolite

catalyst used in this process is generally obtained in drums of dry catalyst.

Based on this information, it is assumed that they should be kept in a dry

cool place. The consumption of catalyst is minimal compared to that of the

raw materials benzene and ethylene, and as such storage will be on a much

smaller scale.

6.2.4 Storage related hazards

The following points are hazards that arise from the storage of the raw

materials for the process. They shall only be mentioned here, and expanded if

they become significant in economic analysis.

• Cryogenic expansion leading to explosion

66

• Extreme cold from cryogenic gas

• Evaporated cryogenic gas can cause asphyxiation (denser than air)

• R-22 refrigeration system hazards, storage of R-22

Cryogenic expansion of a liquefied gas is when a gas evaporates so quickly

that the pressure relief systems cannot handle the overpressure from

expansion. This is generally due to an increase in storage temperature.

6.2.5 Inherently Safer Material Storage

A storage area could be made safer through use of the principles of inherent

safety. They can be applied to several areas of material storage.

Ethylene poses the greatest explosion risk. It may be prudent to design the

storage system to use several smaller storage tanks. This will minimize the

amount of ethylene available for combustion in the event of a fire. This can be

extended to the storage of benzene and the product, ethyl benzene.

R-22 is used as a refrigerant for the cryogenic storage of ethylene. It may be

wise to limit the amount of R-22 stored at the facility. There is no sense in

storing enough R-22 to last several years when it would be safer to store

enough for a few months of operation. R-22 is generally recycled, so

optimization of the R-22 refrigeration system could reduce the amount of new

R-22 required for storage. If a safer refrigerant is available, the alternatives

67

could be studied to measure profitability whether the increase in safety is

justified in the cost. This is an example of material substitution.

Benzene and EB must be stored in well ventilated areas. Design of the

ventilation systems should be such that natural heat convection and plant

layout maximizes plant ventilation characteristics while minimizing cost.

Heat from reactors and boilers creates a natural convection air current,

which could be utilized to aid in ventilation of the plant. Since much of the

equipment is outside, ventilation is not as great a problem. Design of the

plant should be such that confined spaces and areas where vapours could be

trapped is at a minimum.

Storage conditions are such that it is not practical to move storage conditions

closer to standard conditions. Moderating temperatures and pressures for the

storage of ethylene is not practical. Cryogenic storage is safe such that the

risk justifies its use. Furthermore, it is much more economical to store

ethylene as a liquid, increasing density and storing more ethylene in the

same space than a gas.

6.3 Material Transportation

Ethylene can be transported in large shipping tankers overseas. However,

Nova Chemical has an ethylene plant in Joffre, Alberta, and another plant in

Corunna, Ontario, that also produces ethylene. The Sarnia plant receives

68

both benzene and ethylene feed stocks from the Corunna plant directly via

pipeline.64

Pipelines are covered under many regulatory bodies, such as the Office of

Pipeline Safety for the Department of Transport in the U.S. The TPSSC

(Technical Pipeline Safety Standards Committee) and THLPSSC (Technical

Hazardous Liquids Pipeline Safety Committee) outline standards for pipeline

safety for the U.S. Such standards include codes for areas of high residential

growth and environmental regulations.65 No information on pipeline

regulation could be found on the Environment Canada website, however

further research is required.

Basic considerations for pipeline design include:

• Length

• Material fluid

• Throughput

• Geography and climate

• Construction material

Temperatures in the pipeline can affect fluid flow and pipeline integrity. The

length of the pipeline can in part reflect the energy requirements for

pumping. Fluid properties affect what type of pipeline construction material

is needed, and pumping requirements. The size of the pipeline depends on the

flow rate that is desired as well as the velocity of the fluid through the pipe.

69

Higher velocities can put unnecessary forces on the pipeline. The pipeline

must be designed to minimize leaks, climate effects, and environment

hazards.

6.4 Hazard Analysis

6.4.1 Dow Fire & Explosion Index

The Dow Fire and Explosion indices were used to identify the areas of highest

fire and explosion potential in the plant design. An index was created for the

major unit operations: each R-1/R-2 assembly reactor, R-3, C-1, and C-2. A

summary of the calculated Dow F&EI values is shown in Table 6-7.

Table 6-7: Dow F&EI for the EB plant.

Unit Dow F&EI

R-1/R-2 165

R-3 102

C-1 60

C-2 69

It is clear that the feed into the main alkylation section R-1/R-2 has the most

potential for explosion and fire. The main contributing factor to the high

value calculated for each reactor in the R-1/R-2 assembly is the large volume

of benzene flowing, mainly from the C-1 recycle. The R-1/R-2 assembly also

contains the largest amount of ethylene, which requires the use of a higher

material safety factor than R-3, which contains very little ethylene.

70

The columns have a low index. This is partly due to the fact that the columns

are outside, designed with proper drainage control systems, and do not

contain any reactions. These traits minimize the general process hazard

penalty. The large volume of material holdup in the columns, primarily

benzene, contributes a significant penalty; however it is to be expected given

the operation and the size of the columns. The moderate pressures contribute

a minor penalty in comparison.

It should be noted that although C-1 and C-2 have the lowest indices,

business interruption costs the plant $US 10 million as opposed to $US 2.9

million from the R-1/R-2 assembly. C-1 and C-2 contain more product. Fires

and explosions from C-1 or C-2 would result in loss of product and a much

more expensive unit operation.

It can be concluded from the Dow F&EI that the R-1/R-2 assembly will

require further hazard analysis. Detail of the Dow F&EI can be seen in

Appendix E.

6.4.2 Chemical Exposure Index

A Chemical Exposure Index was calculated for each of the major units and

flow intersections. A summary of the results is shown in Table 6-8.

71

Table 6-8: CEI calculated values.

Hazard Distances (ft) CEI Min Mid Max

Benzene Feed Recycle 940 21,000 30,000 39,000 Benzene into C-1 1090 25,000 35,000 46,000 Benzene out of R-1/R-2 Assembly 960 22,000 31,000 40,000 Benzene into R-1/R-2 Assembly 1120 25,000 36,000 47,000 Benzene into R-3 540 12,000 17,000 22,000 Benzene Flash Drum Inlet 540 12,000 17,000 23,000

The CEI values calculated were extremely high. This can be partially

attributed to the large volumes of benzene, the chemically hazardous

component, in the system. The majority of process units handle benzene as a

liquid, but at a temperature above its boiling point. Any loss in pressure

would cause the benzene to vaporize. A worst case scenario of benzene

exposure is shown in Figure 2.

Figure 2: CEI hazard distance map

72

The concentric circles represent increasing hazard distances for the R-1/R-2

assembly feed in the event of a worst cast exposure. The prevailing wind for

the area and direction of flow of the nearby St. Clair River is also shown72.

Benzene exposure concentrations of 1.5 ppm, 2.5 ppm, and 5 ppm correspond

to the maximum, middle, and minimum exposure distances, respectively. The

amount benzene in each unit is directly related to the CEI, where a higher

amount of benzene yields a large CEI. It was determined that the R-1/R-2

assembly will require further hazard analysis.

6.4.3 Hazard Analysis: What-if

A what-if analysis was used to identify potential hazards and appropriate

actions required for a variety of scenarios that can take place around the R-1/

R-2 assembly. The what-if analysis can be seen in Appendix D. The following

cases were considered:

• Liquid benzene spill • Benzene human exposure • Fire near R-1/R-2 assembly • R-1/R-2 assembly explosion • Reactor pressure loss • Reactor temperature increase • Feed system malfunction

It was determined that all forms of fire prevention and mitigation

equipment/systems are required, such as CO2/dry chemical/water

extinguishers, water curtains, alarms, and valve shut-off system. Proper

ventilation systems, spill protection systems such as absorbents, chemical

73

sewers, and chemical level sensor systems should be implemented. Fire

barricades, reactor materials of construction, and explosion venting should be

sufficient for a worst case scenario. Procedural safety measures such as

training and emergency action plans should be properly implemented and

practiced. Lastly, PPE should be available at appropriate locations for the

hazards involved, such as a benzene spill.

It is recommended that a what-if analysis should be conducted for other areas

of the plant, as well as a HAZOP once chemical data and design becomes

finalized.

6.5 Case Studies

The following case studies demonstrate the hazards associated with handling

the chemicals in the EB plant, and illustrate instances where proper

industrial safety and loss management principles could have been used to

prevent or mitigate consequences.

6.5.1 Benzene and Ethylene Explosions

On November 24th, 2001, a Louisiana polymer plant exploded. The source was

from a failed safety valve. A controlled release of ethylene and propylene

caused the safety valve to rupture, causing the leak. The vapours found an

ignition source and exploded. Action was quickly taken to stop further vapour

leak, and the fires burnt out once the leak was stopped.66

74

On November 4th, 1985 at Petroleum Stripping Inc., two employees were

stripping a benzene barge that was not bonded to prevent static sparking. A

spark ignited the vapours, causing an explosion. Both employees were killed

as a result of burning and trauma.67

These case studies point out the severity of a leak leading to an explosion for

both ethylene and benzene. The ethylene explosion was deemed an accident.

The safety valve may not have been properly sized for the operation. It is

important to finalize a design and to ensure that it is not changed during

construction. Changes can cause a butterfly effect of problems around the

plant. The benzene explosion was due to employee negligence, and it is a

possibility that they were not informed of the hazards of a flammable vapour

and static charge.

To prevent problems such as these from happening, ensuring a consistent

design and construction phase of the plant will avoid incorrect equipment

sizing. Incorporating employee training programs and procedures for

handling chemicals such as benzene will go a long way to improving employee

and plant safety.

75

6.5.2 Short Term Ethyl Benzene Exposure

On March 18th 1993 at Automotive Switch Co., a contractor was using

concrete sealant containing significant quantities of EB to apply to a floor

space. A plastic enclosure was used to control dust in the work area.

Employees of the plant began to complain about smells and respiratory

difficulty. The contractor workers and plant employees began to evacuate the

building as more and more people began to suffer the effects of exposure to

the leaking sealant. A strong negative pressure within the plant forced

sealant vapours through holes in the plastic enclosure and into the plant

stock room, which circulated vapours throughout the plant. No MSDS sheet

was provided to properly treat the illnesses on site.68

Such an accident is difficult to predict. Better measures to control sealant

vapours and provide MSDS sheets should have been considered. This is an

example of a deficiency in a loss prevention program and procedural safety. A

procedure for controlling vapours should have been implemented. This

hazard would have been identified using any of the appropriate hazard

identification techniques, such as a What-If analysis or Checklist.

6.5.3 Long Term Benzene Exposure

On April 11th 1988, an employee of C.F. Hoekel Company died of cancer as a

result of long term exposure to benzene. The employee was a pen-ruler for the

print shop. He used different dyes and inks for custom orders such as county

76

ledgers. The pen-ruling machines were old, dating back to the early 1900’s.

He used a mist sprayer apply to benzene, alcohol, and other solvents to clean

the ink pens. He did not make use of proper PPE. There was no local exhaust

system, nor was he trained in the proper use and handling of benzene. A

drum of benzene had be left near the work area for years. No labeling or

monitoring was done to ensure employee exposure or safety. The employee

was diagnosed with a plastic anemia in early 1988, and died April 11th 1988

as a result of the cancer.69

This is a prime example of the effect of long term benzene exposure. The

worker was unaware that benzene posed a significant hazard to his health.

The company was either unaware or negligent in providing the proper

training and procedures for handing benzene and properly cleaning

equipment. It would have been inherently safer to use a cleaning product

that was less hazardous. This is a principle of inherent safety known as

substitution.

6.5.4 Lessons to be learned

These cast studies document accidents that could have been avoided. They

place emphasis on the importance of implementing the following loss

management principles:

77

• It is important to incorporate as many effective inherently safer

designs and engineered safety devices as possible in the design stage

process. An update in a design may impact a section that had already

been completed. Proper sizing considerations may not be taken into

account, and as such valves, piping, and other equipment may not be

large or strong enough.

• Hazard identification techniques should be used as early as possible to

determine the hazards associated with all plant systems, from loading

to processing to transport of products. What-if analyses, checklists,

HAZOP, DOW F&EI and Chemical Exposure Indices can be used to

find hazards and perform risk assessment.

• Implement proper procedures for all aspects of a plant, in areas such

as receiving raw materials, material storage and local transport,

processing, maintenance, emergency procedures, to name a few. This

also includes workplace inspections.

• Provide training for plant employees to ensure they understand the

scope of the operation and the hazards associated with their job.

These are a handful of all the considerations that must be looked at to

properly design an industrial safety and loss management program in the EB

plant. Many of these shall be considered in the design stage of the EB plant.

78

7 Conclusions

Ethyl benzene is primarily a reaction intermediate in the production of

styrene and styrene derived products. The Lummus/UOP EBOneTM process is

one such method to synthesize EB from the reaction of benzene with

ethylene. It has been successfully implemented globally at various styrene

production plants.

Ethyl benzene plants are generally uneconomical; however gains are made in

the production of ethyl benzene derivatives, such as styrene and polystyrene.

Given the small relative price difference between benzene and EB, large

quantities of EB must be produced to turn a profit. The proposed production

(based on Nova Chemicals’ current yearly rate), is approximately 156,000

tonne/yr.

The current NPV of the plant is US$ 7 million, based on the assumed 20-year

life of the plant and a MARR of 20%. An MARR of 20% was selected since a

new process technology is considered a medium level of risk, which

corresponds to an MARR between 16-24%.14 The discounted rate of return

(ROR) was determined to be 27%.

The R-1/R-2 reactor assembly contains two trains of reactors, each consisting

of two alkylation reactors. Running the reactors in this fashion reduces the

79

volumetric flow rate through each reactor, allowing for reasonably sized

reactors of 35 m3. Operating temperatures and pressures range between

120°C-135°C and 1800 kPa.

The largest operational cost in the plant is the amount of raw benzene being

used in the process. A recycle system has been implemented in the simulation

in order to reduce the amount of purged benzene from 24,000 kg/h to 26 kg/h.

In addition, this approach provides the transalkylation section with the

benzene it requires for its transalkylation reaction thus eliminating the

requirement of raw benzene to the R-2 reactor assembly.

80

8 Recommendations

The following sections outline recommendations made to improve the plant

design.

8.1 Process Recommendations

• The underlying problem affecting many areas of the plant is the high

benzene-ethylene feed ratio entering the R-1/R-2 assembly. Insufficient

ethylene is introduced into the system. As a result, excess benzene is

circulating through the recycle loops. It is desired that more benzene be

reacted with ethylene by decreasing this ratio to as low as 1.4:1 to limit

the amount of benzene in the large recycle streams.

8.2 Safety and Environmental Recommendations

The following recommendations outline what should be considered for the

plant design:

• Further hazard analysis should be conducted on other areas of the

plant, including a full HAZOP and What-if/Checklist.

• The R-1/R-2 assembly feed should be reworked to minimize the amount

of material present in a given unit or pipe. Currently, the recycle and

feed streams are mixed before being cooled to the appropriate reaction

temperature. It is desired that the mixing be redesigned such that no

pipe or unit contains the entire flow into the assembly.

81

• Plant layout should be considered using supporting data from Dow

F&EI, CEI, and unit sizing.

8.3 Economical Recommendations

Current economic values are based on estimated values from literature.

However, to determine a more accurate representation of the actual cost,

contractors must be consulted for equipment pricing. Detailed drawings for

each piece of equipment will also be necessary for a full economic analysis.

82

References

1. Qi, Zhiwen and Zhang, Reishang. Alyklation of benzene with ethylene

in a packed reactive distillation column, Ind. Eng. Chem. Res. v.43 (15), 4105-4111, 2004.

2. Encyclopedia of Chemical Processing Design, v.20, 77-78, 1984. 3. UOP: Petrochemical. Lummus/UOP EBOneTM Process,

http://www.uop.com/objects/EBOne 20Process.pdf 4. Qi, Zhiwen and Zhang, Reishang. Alyklation of benzene with ethylene

in a packed reactive distillation column, Ind. Eng. Chem. Res. v.43 (15), 4105-4111, 2004.

5. Encyclopedia of Chemical Processing Design, v.20, 77-78, 1984. 6. UOP: Petrochemical. Lummus/UOP EBOneTM Process.

http://www.uop.com/objects/EBOne%20Process.pdf 7. Tokmakov, I.V. and Lin, M.C., J. Phys. Chem. A 2004, 108, 9697-9714 8. Smith, J.M. et al., Introduction to Chemical Engineering

Thermodynamics. New York, McGraw-Hill Higher Education, 2001. 9. Sardina, H.H et al., Manufacture of Alkylbenzenes, 1991, U.S. Patent

5,003,119 10. Zhang, J et al., Process and apparatus for preparation of ethyl benzene

by alkylation of benzene with dilute ethylene contained in dry gas by

catalytic distillation, 2000, U.S. Patent 6,504,071 11. Standard Reaction for acidity Characterization Ethyl Benzene

Disproportionation, IZA Catalysis Comission, 2002. http://www.iza-catalysis.org/EB_Disprop.html

12. Catalysis and Reaction Engineering, http://thor.tech.chemie.tu-muenchen.de/~tc2/eng/teaching/industr_chem_process2/5.3_alkylation_etbenzene.pdf

13. Peters, M.S. and Timmerhaus, K.D., Plant Design and Economics for Chemical Engineers, McGraw-Hill, 4th Ed., 1991

14. Peters, M.S. and Timmerhaus, K.D., Plant Design and Economics for Chemical Engineers, McGraw-Hill, 5th Ed., 2002

15. Chemical Market Reporter; Jun 14, 2004; 265, 24; ABI/INFORM Global pg. 27

16. http://ceh.sric.sri.com/Public/Reports/645.3000/ 17. Manufacturing Sites,

http://www.novachem.com/03_locations/03_m_sarnia.html 18. http://www.apme.org/media/public_documents/20010821_120531/58.pd

f 19. Narsolis, F., et al., High Performance Catalyst for Liquid Phase EB

Technology, Petrochemicals And Gas, 2001 20. http://www.novachem.com/AnnualReport03/pdfs/MgmtDiscussion.pdf 21. http://www.novachem.com/03_locations/03_m_sarnia.html 22. articles.findarticles.com/ p/articles/mi_m0FVP/is_6_264/ai_107254269

83

23. CW price report, Chemical Week; Nov 17, 2004; 166, 38; ABI/INFORM Global, pg. 27

24. Brown. R., Styrene Poised for Tight First Half of 2004, Chemical

Market Reporter; Dec 1, 2003; 264, 19; ABI/INFORM Global, pg. 1 25. http://www.the-innovation-group.com/ChemProfiles/Ethyl benzene.htm 26. http://www.ars.usda.gov/research/publications/Publications.htm?seq_n

o_115=137352 27. Green Power Suppliers,

http://www.electricitychoices.org/greenpower.html 28. Environment Canada: Greenhouse Gas Emissions:

http://www.ec.gc.ca/energ/oilgas/co2/co2_general_e.htm 29. Environment Canada: Vapour Flaring:

http://www.ec.gc.ca/energ/oilgas/flaring/flaring_general_e.htm 30. Local Hazardous Waste Management in King County: Oily Water:

http://www.govlink.org/hazwaste/business/wastedirectory/wastedetails.cfm?wasteid=142

31. Department of Justice, Canada: Canadian Environmental Protection Act: http://laws.justice.gc.ca/en/C-15.31/

32. Environment Canada: CEPA 200 Substance Reporting: http://www.ec.gc.ca/CEPARegistry/guidelines/impl_guid/x4.cfm

33. Environment Canada: National Pollutant Release Inventory: http://www.ec.gc.ca/pdb/npri/2003Guidance/Guide2003/NPRI_Guide_2003.pdf#page=104

34. NFPA 1600 Standard: Disaster Emergency Planning & Business Continuity Standard: http://www.cheminst.ca/divisions/psm/CEPA200/MacKay%20CEPA%20200%20Preparedness%20%20Response%20Feb.%2004.ppt#262,12,NFPA%201600

35. ISO (International Standards Organization) http://www.iso.org 36. ISO 14000 Environmental Management System:

http://www.iso.org/iso/en/prods-services/otherpubs/iso14000/model.pdf 37. Nova Chemical Explosion Bayport, Texas:

http://www.texasbucketbrigade.org/newsletter/june%20newsletter.html 38. Nova Chemical Explosion Bayport, Texas: Release Information:

http://kpft.igc.org/news/070203story5.html 39. Engineering Tool Box - http://www.engineeringtoolbox.com/9_423.html 40. BOC Gases – MSDS – Ethylene – http://www.vngas.com/pdf/g33.pdf 41. Physical and Theoretical Chemistry Laboratory

http://physchem.ox.ac.uk/MSDS/BE/benzene.html 42. MSDS - Benzene -

http://www.ril.com/cmshtml/msdsben.pdf?page_id=516 43. International Agency for Research on Cancer - http://www-

cie.iarc.fr/monoeval/crthall.html

84

44. MSDS – Ethyl benzene - http://www.osha.gov/SLTC/healthguidelines/ethyl benzene/recognition.html

45. Petro Canada – Benzene MSDS Sheet 46. MSDS Benzene -

http://www.ejnet.org/plastics/polystyrene/benzene.html 47. CHEMREST – Comprehensive guide to Chemical Resistant Best

Gloves http://www.chemrest.com/Toxicity%20and%20Risk%20Codes/Ethyl%20Benzene.htm

48. International Agency for Research on Cancer - http://www.iarc.fr/ 49. MSDS - Ethyl benzene -

http://www.osha.gov/SLTC/healthguidelines/ethyl benzene/recognition.html

50. MSDS – DEB - https://fscimage.fishersci.com/msds/38247.htm 51. CPChemTM MSDS – Chevron Phillips Chemical Company LP 52. Mallinckrodt Chemicals -

http://www.jtbaker.com/msds/englishhtml/t3913.htm 53. ScienceStuff.com - http://www.sciencestuff.com/msds/C2881.html 54. Mallinckrodt Chemicals -

http://www.jtbaker.com/msds/englishhtml/t3913.htm 55. UOP – http://www.uop.com 56. International Training Organization -

http://www.itcilo.it/actrav/actrav-english/telearn/osh/ic/100414.htm 57. Mallinckrodt Chemicals -

http://www.jtbaker.com/msds/englishhtml/t3913. 58. Canadian Center for Occupational Health & Safety -

http://www.ccohs.ca/oshanswers/chemicals/compressed/compress.html 59. Universal Industrial Gases Inc. -

http://www.uigi.com/lng_eth_tanks.html 60. Larsen & Toubro Limited -

http://www.lntenc.com/lntenc/services/industries/chemical/cryogenic.htm 61. Larsen & Toubro Limited -

http://www.lntenc.com/projects/chemical/cryogenicprojects.htm 62. Petro Canada – Benzene MSDS Sheet 63. Canadian Center for Occupational Health and Safety -

http://www.ccohs.com/oshanswers/chemicals/chem_profiles/benzene/working_ben.html

64. Nova Chemical, http://www.novachem.com/03_locations/03_manufacturing_f.html

65. USDOT – Office of Pipeline Safety - http://ops.dot.gov/ 66. Louisiana polymer plant explosion: http://www.acusafe.com

85

67. Petroleum Stripping Inc. benzene explosion: http://www.osha.gov/pls/imis/accidentsearch.accident_detail?id=14498463

68. Automotive Switch Co.: EB employee exposure: http://www.osha.gov/pls/imis/accidentsearch.accident_detail?id=675231

69. C.F. Hoekel Company: Long term benzene exposure: http://www.osha.gov/pls/imis/accidentsearch.accident_detail?id=14506059

70. Nova Chemicals 2004 Annual Report, http://www.novachem.com/AnnualReport04/nova.htm

71. Viswanathan, P., ACN: Asian Chemical News, Mar 14-Mar 20, 2005. Vol.11, Iss. 482; pg. 25

72. Sarnia Prevailing Winds, http://www.theweathernetwork.com

86

Appendices

A. Economics Spreadsheet ITEM VALUE ITEM VALUE $/kg

Labour (4 operators) $25/h Project Start Sept 2006Plant Start-up Sept 2007 Ethylene ($/lb) 0.22 0.484

Plant life 20 a Income Tax 60.0% Benzene ($/gal) 3.5 1.05Hours/year 8700 Styrene ($/lb) 0.64Feed water $0.008/kg Ethylbenzene ($/lb) 0.5104 1.12288

Equipment Costs (M&S Index = 1117)EQUIPMENT TYPE SIZE IMPORTED SPECS UNITS PURCHASE COST, $000INSTAL (%) INSTALL COST, $000

CSTR (R-1-1A) Reactor Volume 35.0 122 45.00$ 55CSTR Motor (R-1-1A) R_Motor Volume 35.0 3 45.00 1CSTR (R-1-2A) Reactor Volume 35.0 122 45.00 55

CSTR Motor (R-1-2A) R_Motor Volume 35.0 3 45.00 1CSTR (R-2-1A) Reactor Volume 35.0 122 45.00 55CSTR Motor (R-2-1A) R_Motor Volume 35.0 3 45.00 1CSTR (R-2-2A) Reactor Volume 35.0 122 45.00 55

CSTR Motor (R-2-2A) R_Motor Volume 35.0 3 45.00 1CSTR (R-3-1A) Reactor Volume 30.0 111 45.00 50CSTR Motor (R-3-1A) R_Motor Volume 30.0 2 45.00 1

Pump (P-1) Pump Vol. Flow Rate 16.1 6 42.50 2Pump Motor (P-1) P_Motor Power (Duty) 10.2 1 42.50 1Pump (P-3) Pump Vol. Flow Rate 25.6 7 42.50 3

Pump Motor (P-3) P_Motor Power (Duty) 1.5 0 42.50 0Pump (P-2) Pump Vol. Flow Rate 67.8 9 42.50 4Pump Motor (P-2) P_Motor Power (Duty) 38.5 3 42.50 1DIST COL (C-1) Diameter 3.4

DC_Trays Ntray 26.7 397 75.00 298DC_H Height 16.3 654 75.00 491

Condenser (C-1) Q 5.89E+07TLout 82.6

TLin 132.1Delta TL 49.5

Cond Area 211.7 105 75.00 79Reboiler (C-1) Q 5.92E+07

TLout 193.8TLin 214.6Delta TL 20.7

Reb Area 713.4 245 45.00 110

DIST COL (C-2) Diameter 2.3DC_Trays Ntray 33.3 369 75.00 277DC_H Height 20.3 608 75.00 456

Condenser (C-2) Q 1.80E+07

TLout 184.7TLin 188.5Delta TL 3.9

Cond Area 242.3 115 7.50E+01 86Reboiler (C-2) Q 1.79E+07

TLout 241.2TLin 253.4

Delta TL 12.2Reb Area 367.6 154 45.00 69

Separator (V-100) Sep Volume 3.3 33,399 45.00$ 15,0290

HX1 HX Area 26.9 8,279 40.00 3,312HX2 HX Area 35.4 9,684 40.00 3,873HX2 HX Area 34.6 9,546 40.00 3,818

Total cost (2002) 3,345,443$ 2,177,942$

M&S cost index for 2002 1117 111715.4 335 M&S cost index for 3Q 2004 1194 1194

152.0538 Total cost (2004) 3,576,060$ 2,328,077$

87

To

tal

Pla

nt

Co

st

23,7

20

,43

4.2

2$

FC

I$

18,6

70

,67

3P

rod

uc

tsP

rod

uc

ts

EB

($

/kg

)1

.12

$

E

B (

kg

/hr)

17

,95

6.7

0

To

tal

Wo

rkin

g C

ap

ita

l

Inte

res

t

Inte

rest

Ra

te (

%)

20

%P

&T

(p.

32

2)

Me

diu

m L

evel o

f R

isk

Yea

rC

harg

eP

aym

en

tB

ala

nc

e

Ta

x R

ate

(%

)60

%0

836

652

.54

98

87

,11

6,1

30

.27

E

co

no

mic

lif

e (

# Y

ea

rs)

20

18

36

652

.54

98

87

,64

8,7

68

.14

H

ou

rs/y

ea

r87

00

28

36

652

.54

98

88

,22

4,0

17

.04

Yea

r0

12

34

56

7

Wo

rkin

g c

ap

ita

l$3

,182

,69

3.7

1C

ap

ital

(ex

cl.

Wo

rkin

g c

ap

)$

20

,537

,74

0.5

1

Op

era

tin

g C

os

ts$1

56

,97

9,0

35

.63

$15

6,9

79

,03

5.6

3$

156

,979

,03

5.6

3$

156

,97

9,0

35.6

3$

15

6,9

79,0

35.6

3$

15

6,9

79,0

35.6

3$

15

6,9

79,0

35

.63

Pro

du

ct

sa

les

$1

75

,42

0,0

23

.54

$1

75

,420

,024

$1

75,4

20

,02

4$1

75

,42

0,0

24

$1

75

,42

0,0

24

$17

5,4

20

,02

4

Gro

ss R

ev

en

ue

-$23

,720

,43

4.2

2$

0.0

0$

18,4

40

,98

7.9

1$1

8,4

40

,98

7.9

1$

18,4

40

,98

8$

18

,44

0,9

88

$1

8,4

40

,98

8$

18

,44

0,9

88

De

pre

cia

tio

n$9

33

,53

3.6

6$

93

3,5

33

.66

$9

33

,53

3.6

6$

93

3,5

33.6

6$

93

3,5

33.6

6$

93

3,5

33.6

6G

ros

s P

rofi

t-$

23

,720

,43

4.2

2$

0.0

0$1

7,5

07

,454

$17

,507

,45

4$

17,5

07

,45

4$

17

,50

7,4

54

$1

7,5

07

,45

4$

17

,50

7,4

54

Ta

x$

10,5

04

,47

2.5

5$1

0,5

04

,47

2.5

5$

10

,504

,47

2.5

5$

10

,50

4,4

72.5

5$

10,5

04,4

72.5

5$

10,5

04,4

72.5

5$

10,5

04,4

72

.55

Ne

t P

rofi

t-$

23

,720

,43

4.2

2$

0.0

0$

7,9

36

,51

5$7

,936

,51

5$

7,9

36,5

15

$7

,93

6,5

15

$7

,93

6,5

15

$7

,93

6,5

15

PV

-$23

,720

,43

4.2

2$

0.0

0$

5,5

11

,46

9.0

0$

4,5

92

,89

0.8

3$3

,827

,40

9.0

3$3

,18

9,5

07.5

2$

2,6

57,9

22.9

4$

2,2

14,9

35

.78

NP

V$7,2

02,0

33

152

777

.77

78

00

00

61

39

7.9

623

9

NP

V f

or t

he

firs

t 7

yea

rs

88

B. Sample Equipment Cost Calculations The cost equation is in the form of: n(size)CC o= (B.1)

Where: C = cost of equipment

Co = a constant n = cost exponent

Co and n are found knowing two values of cost and size. Taking the natural log (ln) of Eq. (B.1.): )ln(Csize)ln(ln(C) o+= n (B.2)

And with two values, one gets: ( )

( ) ��

�

�=��

�

��

�

1

2

1

2

size

sizeln

C

Cln n

(B.3)

Cost of stirred reactor Description: Carbon steel, 300 psia (2070 kPa) {current process is at 260 psia} From Fig 13-15, p. 628 (P&T, 2002) 6.0 m3 = $40,000 0.2 m3 = $5,000 So,

��

�

�=��

�

��

�

2.0

6ln

000,5

40,000ln

1

n

(B4)

Solve for n:

n = 0.611

then from Eq. B.2,

Co = 13,880

0.611ume)13,880(Volcost =∴

89

Cost of Heat Exchanger Description: Fixed-tube-sheet heat exchanger; Material adjustment factor: 1.0 (Carbon steel) From Fig 14-18, p. 682 (P&T, 2002) 5 m2 = $3,000 400 m2 = $30,000 So,

��

�

�=��

�

��

�

5

400ln

000,3

30,000ln

1

n

(B.6)

Solve for n:

n = 0.525

then from Eq. B.2,

Co = 12,900

0.525a)12,900(Arecost =∴

90

C. Glossary ACGIH-TLV

American Conference of Governmental Industrial Hygienists Threshhold Limit Value

DEB Di-ethyl benzene

EB Ethyl benzene

IARC International Agency for the Research on Cancer

IRIS Integrated Risk Information System

IRR Internal rate of return

LD50/LC50 Lethal Dose/ Concentration Kill 50%

LDLo/LCLo Lowest published lethal dose

LEL-UEL Lower and upper explosive limits

LFL-UFL Lower and upper flammability limits

NFPA National Fire Prevention Association

NIOSH-REL

National Institute for Occupational Health and Safety Recommended Exposure Limit

NTP National Toxicology Program

OSHA-PEL Occupational Health and Safety Association Permissible Exposure Limit

ROR Rate of return

STEL Short Term Exposure Limit (15 min) TEB Tri-ethyl benzene

TWA Time weighted average

91

D. What-if? Analysis

WHAT-IF CONSEQUENCE(S) EXISTING SAFE-

GUARDS RECOMMENDATIONS

1) What if there is a Benzene spill from a surge drum in the R-1 assembly?

• Flammable vapors within 1.3 vol% or below or 8 vol% high may ignite off the surge drum pumps or other ignition source. Causing Harm or loss to process, personnel and/or environment. • Human exposure to a carcinogenic chemical

• Safety shower, fire blankets, and CO2/Dry Chemical extinguishers are present near the surge drum and every 20 meters thereafter. • Level controls present on the surge drum with operator alarms and control options via a remote source. • Chemical sewers and proper treatment of sewage.

• Ensure that safety devices such as safety showers, extinguishers, and remote control are operational and maintained. • Safety courses (WHMIS) to ensure employees are aware of the hazards. • Inspection of process to minimize benzene or other chemical spill from unit operations. • Ensure the process controller is functioning properly or calibrated correctly on a regular basis. • Investigate and control the amount of raw benzene contained in the plant site.

2) What if there is human exposure to benzene near the R-1 assembly?

• Exposure to a carcinogenic substance which may result in burns to the eyes and face and increase potential of cancer.

• See existing safeguards for surge drum spill. • PPE such as safety glasses, coveralls and safety gloves. • Safety procedures for cleanup and evacuation.

• Ensure that PPE is in good working condition. • Ensure that procedures for evacuation and cleanup are up to date and in practices.

3) What if there is a fire near the R-1 assembly? (includes: benzene, ethylbenzene, and ethylene)

• Possible loss to property, process, people and environment.

• Fire codes enforced, and practiced by fire hall or department. • Safety awareness by management to employees regarding fire hazards of chemicals used on plants. • Fire alarms on site • Fire retardant construction and materials.

• Ensure codes are in practice • Ensure MSDS’s of flammable components are on site (for hazard awareness) • Quarterly fire drill improvement plans by fire hall and management

92

4) What if a reactor in the R-1 assembly explodes?

• Property Damage • Injury/death • Halted production • Fire can spread to other parts of the plant

• Explosion barricades • Proper plant layout where reactors are outside minimum range for explosion (Dow F&EI) • Sprinkler/ CO2/ Chemical Extinguishers • Water curtain • Emergency shut-off valve system • High strength materials construction for the reactors

• Proper emergency procedural training practices regularly • Ensure adequate PPE is readily accessible in the event of an explosion (for Benzene exposure, smoke etc.) • Install Properly functioning explosion venting to direct explosive force

5) What if the reactor section looses pressure (pressure decrease)?

• Ethylene/ benzene flash • Possible leak of gas into plant / atmosphere • Vapors enter downstream operations / pumps • Heat exchanger efficiency will decrease as a result of vapors in tubes (poor contact, heat transfer properties of vapor)) • Distillation column operating conditions will be affected

• None currently present in simulation • Water curtain to contain any large vapor release

• Redundant compressors and pumps • Vapor collection and recycle systems

6) What-if reactor pressure/ temperature increases well above desired operational values? (exothermic reaction)

• Reactor pressure causes explosion • Temperature runway degrades tubes • Temperature and pressure damages reactor internals • Temperature causes coking (fine particles degrades catalyst) • Possible loss to People • Loss to process during shutdown. • Possible loss to environment due to

• Pressure Safety Release/ Valve • temperature controlled jacket around reactor • appropriate unit operations upstream to control reactor feed • appropriate process control in place to control reactor conditions

• Ensure engineered safety items are incorporated into process, and ensure all are in proper working condition • Update or create more rigorous safety inspections and protocols for reactor maintenance • Inspect process control to ensure it is properly tuned. • Follow proper maintenance schedule and equipment strategies

93

reactor spillage or vapors released into air.

7) What if there is an Ethylene feed system complication? (explosion, fire, etc.)

• process shut down • non-sparking or ignition components installed (unit operations) • Storage tanks ignite and exploding, causing damage to the property and halting process. People and environment may also be harmed.

• Properly labeled storage area and tanks • NO SMOKING signs appropriately placed • Explosion barricades protecting existing equipment • Chemical monitoring and alarm systems both portable and fixed. • Fire retardant construction and materials.

• investigate whether non-sparking or ignition unit operations are used • Incorporate a maintenance schedule to ensure tight seals on fittings and assess degradation of storage area. • Reduce the amount of Ethylene stored in one place. • Install proper ventilation system to avoid gas buildup. • Possible redundant feed system design

94

E. F&EI Sample Calculations R-1/R-2 Assembly Material Factor: Ethylene 24.00

1 General Process Hazards

Penalty Factor Range

Penalty Factor Used

Base Factor 1.00 1.00

A. Exothermic Chemical Reactions 0.30 - 1.25 0.50

B. Endothermic Processes 0.20 - 0.40 0.00

C. Material Handling and Transfer 0.25 - 1.05 0.00

D. Enclosed or Indoor Process Units 0.25 - 0.90 0.45

E. Access 0.25 - 0.35 0.00

F. Drainage and Spill Control (gallons) 305,000 0.25 - 0.50 0.00

General Process Hazards Factor (F1) 1.95

2 Special Process Hazards


A. Toxic Material(s) 0.20 - 0.80 0.40

B. Sub-Atmospheric Pressure (<500 mmHG) 0.50 0.00

C. Operation in or near flammable range 0.00

1 Tank farms storage flammable liquids 0.50 0.00

2 Process upset of purge failure 0.30 0.30

3 Always in flammable range 0.80 0.00

D. Dust explosion (See Table 3) 0.25 -2.00 0.00

E. Pressure (See Figure 2) (psig) Operating Pressure 244 0.48

Relief Setting 300 0.53 0.52

F. Low Temperature 0.20 - 0.30 0.00

G. Quantity of Flammable/Unstable Material

Quantity (lb) 43000

Hc (BTU/lb) 18,000

1 Liquids or Gasses in Process (Fig. 3) 1.32

2 Liquids or Gasses in Storage (Fig. 4) 0.00

3 Combustible Solids in Storage,

Dust in Process (Fig. 5) 0.00

H. Corrosion and Erosion 0.10 - 0.75 0.00

I. Leakage 0 Joints and Packing 0.10 - 1.50 0.00

J. Use of Fired Equipment (Fig. 6) 0.00

K. Hot Oil Heat Exchange System 0.15 - 1.15 0.00

L. Rotating Equipment 0.50 0.00

Special Process Factor (F2) 3.53

Process Unit Hazards Factir (F1 x F2) = F3 6.89

Fire and Explosion Index (F3 x MF = F&EI) 165.25

95

1. Process Control Credit Factors (C1)

Feature

Credit Factor Used Feature

Credit Factor Used

a. Emergency Power 0.98 f. Inert Gas 1.00

b. Cooling 0.97 g. Operating Instructions/Procedures 0.91

c. Explosion Control 0.84 h. Reactive Chemical Review 0.91

d. Emergency Shutdown 0.98 i. Other Process Hazard Analysis 0.94

e. Computer Control 0.93

C1 Value 0.57

2. Material Isolation Credit Factor (C2)

Feature


Credit Factor Used

a. Remote Control Valves 0.96 c. Drainage 0.91

b. Dump/Blowdown 0.98 d. Interlock 0.98

C2 Value 0.84

3. Fire Protection Credit Factor (C3)

Feature


Credit Factor Used

a. Leak Detection 0.94 f. Water Curtains 0.97

b. Structural Steel 0.98 g. Foam 0.94

c. Fire Water Supply 0.94 h. Hand Extinguishers/Monitors 0.98

d. Special Systems 0.91 i. Cable Protection 0.94

e. Sprinkler Systems 0.81

C3 Value 0.54

Loss Control Credit Factor = C1 x C2 x C3 0.25

1. Fire & Explosion Index (F&EI)…………………………………… (See Front) 165.25

2. Radius of Exposure (ft)……………………………………………….… (Figure 7) 138.81

3. Area of Exposure (ft2)………………………………………………………………… 60535.58

4. Value of Area of Exposure……………………………………………………….…. $112,088.00

5. Damage Factor………………………………………………………….. (Figure 8) 6.50

6. Base Maximum Probable Property Damage……………………………. (4x5) $728,572.00

7. Loss Control Credit Factor………………………………………... (See Above) 0.25

8. Actual Maximum Probable Property Damage…………………………. (6x7) $185,650.33

9. Maximum Probable Days Outage………………………………….. (Figure 9) 8.00

10. Business Interruption……………………………………………………………. $2,908,888.89

96

R-3 Material Factor: Benzene 16.00

1 General Process Hazards Penalty Factor Range

Penalty Factor Used






E. Access 0.25 - 0.35 0.00
















Quantity (lb) 44000

Hc (BTU/lb) 18,000













97


Feature


Credit Factor Used






C1 Value 0.57


Feature


Credit Factor Used



C2 Value 0.84


Feature


Credit Factor Used






C3 Value 0.54







6. Base Maximum Probable Property Damage……………………………. (4x5) $538,895.50


8. Actual Maximum Probable Property Damage…………………………. (6x7) $137,318.11



98

C-1 Material Factor: Benzene 16.00



Penalty Factor Used






E. Access 0.25 - 0.35 0.00










3

Always in flammable range 0.80 0.00






Quantity (lb) 80,000

Hc (BTU/lb) 20,000



3 Combustible Solids in Storage










99


Feature


Credit Factor Used






C1 Value 0.57


Feature


Credit Factor Used



C2 Value 0.84


Feature


Credit Factor Used






C3 Value 0.54







6. Base Maximum Probable Property Damage……………………………. (4x5) $5,058,487.50


8. Actual Maximum Probable Property Damage…………………………. (6x7) $1,288,973.32



100

C-2 Material Factor: Benzene 16.00



Penalty Factor Used






E. Access 0.25 - 0.35 0.00
















Quantity (lb) 400,000

Hc (BTU/lb) 20,000













101


Feature


Credit Factor Used






C1 Value 0.57


Feature


Credit Factor Used



C2 Value 0.84


Feature


Credit Factor Used






C3 Value 0.54





4. Value of Area of Exposure……………………………………………………….…. $1,345,347.00


6. Base Maximum Probable Property Damage……………………………. (4x5) $7,399,408.50


8. Actual Maximum Probable Property Damage…………………………. (6x7) $1,885,472.71



102

F. CEI Sample Calculations A sample calculation for the CEI is shown below, using the feed to the R-1/R-2 assembly. The Chemical Exposure Index (CEI) was calculated using the procedure on page 3 of the “Chemical Exposure Index Guide, September 1993, 2nd edition. Step One: Define the chemical being investigated and the conditions at

which the scenario is taking place. In our case this is not a scenario, it is a real event.

The chemical properties are as follows. Chemical Name: Benzene (Gas): Assume that all the liquid vaporized Temperature: 83°C Pressure: 400 kPa at C-1 assembly Rate of Release: 60,000 kg/hr 1 hr/60 min=1,000 kg/min=2,200 lb/min×

Step Two: Find the ERPG-2/EEPG-2 data from Table 1 on page 6. In

addition find the Molecular Weight from this table as well. The data is as follows: ERPG-1 (ppm) = 1.5 ERPG-2 (ppm) = 2.5 ERPG-3 (ppm) = 5 Molecular Weight = 78.1 g/mol Step Three: Determine the Airborne Quantity (AQ) using a gas relationship

and US/BRIT Units. The equation for calculating AQ is as follows: 2

a(AQ)=3.751D P MW/(T+459) (1)

Where: AQ is the Airborne Quantity D is the diameter of the hole (inches) Pa is the absolute pressure (Pg +14.7) Pg is the gauge pressure (PSIG)

103

The result of the AQ calculation is as follows:

2 o(AQ)=3.751(1 in.) (190 psia) 70.9/(180.5 F+459)=2,140

Step Three (Alternate):

AQ(Alternate)=130,000 lb/hr/1 hr 1 hr/60 min=2,170 lb/min×

Step Four: Calculate the CEI using the following formula: CEI=281.8 AQ/(ERPG-2×MW) (2)

Where:

CEI is the Chemical Exposure Index ERPG-2 is the Emergency Exposure Planning Guideline (ppm)

The result of the CEI calculation is as follows:

CEI=281.8 2,200/(2.5)(78.1)=936

The value of this CEI is quite high. The guide states on page i, a CEI greater then 200 for a facilities will require further risk analysis. The calculation of the Hazard Distance (HD) using US/Brits units is done using the following expression. HD=9,243 AQ/ERPG(MW)

Where: HD is the Hazard Distance (ft) AQ is the Airborne Quantity (ppm) ERPG is the Emergency Exposure Planning Guideline MW is the molecular weight The result for the HD expression for ERPG-1 is as follows:

HD=9,243 2,167/1.5(78.1)=39,800 ft

104

The result for the HD expression for ERPG-2 is as follows:

HD=9,243 2,167/2.5(78.1)=30,800 ft

The result for the HD expression for ERPG-3 is as follows:

HD=9,243 2,167/5(78.1)=21,800 ft

105

G. HYSYS Workbook Output

Date post:	28-Oct-2014
Category:	Documents
Upload:	ahmed-ali
View:	1,397 times
Download:	86 times

Liquid Phase Alkylation of Benzene with Ethylene

Documents