Production of Acetaldehyde

8/13/2019 Production of Acetaldehyde

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CHAPTER-1

INTRODUCTION

Acetaldehyde (systematically ethanal) is an organic chemical compound with

the formula CH 3CH O or MeCHO. It is one of the most important aldehydes,

occurring widely in nature and being produced on a large scale industrially.

Acetaldehyde occurs naturally in coffee, bread, and ripe fruit, and is produced

by plants as part of their normal metabolism. It is also produced by oxidation

of ethanol and is popularly believed to be a cause of hangovers. Pathways of

exposure include air, water, land or groundwater that can expose the human

subject directly if they inhale, drink, or smoke.

1.1 PHYSICAL PROPERTIES

Acetaldehyde is a colorless, mobile liquid having a pungent suffocating

odor that is somewhat fruity and pleasant in dilute concentrations. Some

physical properties of acetaldehyde are given in Table(1.1), the vapour pressure

of acetaldehyde and its aqueous solutions in Table(1.2 & 1.3) and the solubility

of acetylene, CO 2 and N 2 in liquid acetaldehyde in Table(1.4). The freezing points of aqueous solutions of acetaldehyde are as follows:

4.8 wt.% - 2.5 oC; 13.5 wt.% - 7.8 oC; & 31.0 wt.% - 23.0 oC

Acetaldehyde is miscible in all proportions with water and most common

organic solvents; acetone, benzene, ethyl alcohol, ethyl ether, gasoline,

paraldehyde, toluene, xylene, and acetic acid.
http://en.wikipedia.org/wiki/Organic_compoundhttp://en.wikipedia.org/wiki/Chemical_formulahttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Aldehydehttp://en.wikipedia.org/wiki/Coffeehttp://en.wikipedia.org/wiki/Breadhttp://en.wikipedia.org/wiki/Fruithttp://en.wikipedia.org/wiki/Planthttp://en.wikipedia.org/wiki/Metabolismhttp://en.wikipedia.org/wiki/Ethanolhttp://en.wikipedia.org/wiki/Hangoverhttp://en.wikipedia.org/wiki/Hangoverhttp://en.wikipedia.org/wiki/Ethanolhttp://en.wikipedia.org/wiki/Metabolismhttp://en.wikipedia.org/wiki/Planthttp://en.wikipedia.org/wiki/Fruithttp://en.wikipedia.org/wiki/Breadhttp://en.wikipedia.org/wiki/Coffeehttp://en.wikipedia.org/wiki/Aldehydehttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Chemical_formulahttp://en.wikipedia.org/wiki/Organic_compound


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Table-1.1: Physical Properties of Acetaldehyde

Formula weight 44.052

Melting point, C -123.5

Boiling point at 760 mm, C 20.16

Density, d 2o4 0.7730

Vapor density (air = 1) 1.52

Surface tension at 20 oC, dyne/cm 21.2

Absolute viscosity at 15 oC ( cgs units) 0.02456

Specific heat, cal/( oC)(g) at 0 oC 0.522at 25C 0.336

Latent heat of fusion, cal/g 17.6

Latent heat of vaporization, cal/g 139.5

Heat of combustion of liquid at constt.pr. Kcal/mol 279.2

Heat of formation at 273 oK 39.55

Free energy of formation at 273o

K, Kcal/mole -32.60Critical temp, C 181 .5

Critical pressure, atm. 63.2

Dissociation constant, K a, at 0oC 0.7 10 -14

Flash point, closed cup, C -38

Ignition temp. in air, oC 165

Explosive limits of mixtures with air, % acetaldehyde by vol. 4-57


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Table-1.2: Vapor Pressure of Acetaldehyde

Temperature oC Vapor Pressuremm Hg TemperatureoC Vapor pressuremm Hg

-50

-20

0

5

10

15

19

123

330

411

508

622

20

20.16

30

50

70

100

755

760

1069

3096

3696

3607

Table-1.3: Vapor Pressure of Aqueous solutions of Acetaldehyde

Temperature oC Vapor Pressuremm Hg Temperature oC Vapor pressuremm Hg

1010

20

20

4.910.5

5.4

12.9

4.910.5

5.4

12.9

74.5139.8

125.2

295.2

Table-1.4: Solubility of Gases in Liquid Acetaldehyde at 760 mmHg(volume of gas [NTP] dissolved in one volume of acetaldehyde)

Temperature oC Acetylene Carbon Dioxide Nitrogen

-6

0

12

16

27

17

7.3

5

11

6.6

2.45

1.50.15


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1.2 USES

About 95% of the acetaldehyde produced is used internally by themanufacturers as an intermediate for the production of other organic chemicals..

Table(1.5), gives an idea of the use pattern. Imports and exports of acetaldehyde

are negligible.

Acetic acid and anhydride are the major derivatives of acetaldehyde (45%

in 1970) followed by n-butanol (19%) and 2-ethylhexanol (17%). Twenty

percent of the acetaldehyde is consumed in a variety of other products, the most

important being pentaerythritol, trimethylolpropane, pyridines, peracetic acid,

crotonaldehyde, chloral, 1,3-butylene glycol, and lactic acid. The proportion of

acetaldehyde used in the manufacture of acetic acid and acetic anhydride will

tend to increase in the near future, and the proportion used in the synthesis of n-

butanol and 2-ethylhexanol will decrease. Acetaldehyde is competing with

propylene and -olefins as the raw material for the production of n-butanol and

higher alcohols (oxo route).

Other uses of acetaldehyde include: in the silvering of mirrors; in leather

tanning; as a denaturant for alcohol; in fuel mixtures; as a hardener for gelatin

fibres; in glue and casein products; as a preservative for fish and fruit; in the

paper industry; as a synthetic flavoring agent; and in the manufacture of

cosmetics, aniline dyes, plastics and synthetic rubber.

Acetaldehyde is also used in the manufacture of disinfectants, drugs,

perfumes, explosives, lacquers and varnishes, photographic chemicals, phenolic

and urea resins, rubber accelerators and antioxidants, and room air deodorizers;

acetaldehyde is a pesticide intermediate.


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Table-1.5 Acetaldehyde, United States Uses in 1970

Acetic acid and anhydride 45 %n-Butanol 19%

2-Ethylhexanol 17%

AH others 19%

The future growth of acetaldehyde will be mainly dictated by the acetic

acid and anhydride picture and the growth of the other minor derivatives

mentioned above.

1.3 FUTURE TRENDS

In the next decade the major change that will occur in the acetaldehyde

picture is a decrease in the use of acetaldehyde for the preparation of derivativesthat can be manufactured from alternative raw materials. This has already

happened in the production of butanol and 2-ethylhexanol in which

acetaldehyde raw material has been replaced by propylene and synthesis gas in

oxo-type processes. Acetic acid and anhydride are the major outlets for

acetaldehyde. Production of these chemicals from alternative processes (like

methanol carbonylation or saturated hydrocarbon oxidation) would also have an

adverse effect on acetaldehyde consumption in the future. Here again, the

energy crisis could accelerate the expansion of some of these processes that are

competing with acetaldehyde by-making synthesis gas and carbon monoxide

available through coal gasification. Long range, carbon monoxide and hydrogen

could become the new building blocks of the organic chemical industry.


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1.4 HANDLING

In handling acetaldehyde, one has to remember that it is an extremely

reactive compound that can be easily oxidized, reduced, or polymerized, and is

highly reactive with oxygen. It has to be treated as a volatile, flammable, and

toxic material. The following is a list of precautions recommended when

handling acetaldehyde:

Nitrogen or other inert gases should be used as a blanketing

material whenever exposure to air is a possibility

Safety goggles should be used Transfers should be made in open-air structures or using suitable

gas mask or self-contained breathing equipment .

Drums should be stored out-of-doors, avoiding direct exposure to

sunlight

Acetaldehyde should be-chilled before transferring and a nitrogen

blanket should be used.

1.5 SHIPPING AND STORAGE

Acetaldehyde is shipped insulated tank trucks, and insulated tank cars.

Acetaldehyde in, the liquid state is non-corrosive to most metals, but it can be

easily oxidized to acetic acid. Suitable materials of construction are stainlesssteel and aluminum. Drums coated with phenolic resins have also been used. If

a darker color and some iron contamination are not objectionable, carbon steel

may be used. Because acetaldehyde is classed as a flammable liquid, it requires

a red DOT (Department of Transportation) shipping table.

Bulk storage held at low temperature and pressure is recommended over

storage in a pressure vessel.


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CHAPTER-2

MANUFACTURING PROCESSES

The economics of the various processes for the manufacture of acetaldehyde are

strongly dependent on the price of the feed stock used. Since 1960 the liquid

phase oxidation of ethylene has been the process of choice. However, there is

still commercial production by the partial oxidation of ethyl alcohol and the

hydration of acetylene.

Acetaldehyde is also formed as a co-product in the high temperature

oxidation of butane. A recently developed rhodium catalyzed process producesacetaldehyde from synthesis gas as a co-product with ethyl alcohol and acetic

acid.

2.1 HYDRATION OF ACETYLENE

In this process high pricing acetylene is fed with steam to a rubber lined

vertical reactor which contains a catalyst solution of mercury salt (0.5 to 1

wt.%) sulfuric acid (15 to 20 wt.%) ferrous and ferric iron (2 to 4 wt/%) and

water. Minute particles of free mercury are suspended in the catalyst solution.

The temperature and pressure are controlled at 90 to 95 oC and 1 to 2 atm,

respectively. The acetylene conversion per pass is about 55%.


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2.2 ETHYLENE OXIDATION PROCESS

The process is essentially based on three chemical reactions.

C2H4 + 2CuCl 2 + H 2O CH 3CHO + Pdo + 2HCl

Pdo + 2CuCl 2 PdCl 2 + 2CuCl (Pd oxidation)

2CuCl + 2HCl + 1/2O 2 2CuCl 2 + H 2O (CuCl oxidation)

C2H4 + O 2 CH 3CHO (Overall reaction)

In this process, the palladium chloride is required only in very small

concentration, and the copper salts are continuously regenerated with oxygen. In

this way direct oxidation of ethylene take place.

In this process fresh oxygen and ethylene are fed independently to a

vertical ceramic lined reactor containing a water solution of catalyst (PdCl 2 and

CuCl 2). The reactor is operated to 120 to 130o

C and about 3 atm. The heat ofvaporization is removed by evaporating acetaldehyde and water from the

catalyst solution. The ethylene conversion per pass is 75%.

2.3 OXIDATION OF SATURATED HYDROCARBONS

Acetaldehyde is formed as a co-product in the vapor-phase oxidation of

saturated hydrocarbon such as butane. Oxidation of butane yields acetaldehyde,

formaldehyde, methanol acetone and mixed solvents as major products, other

aldehydes, alcohols, ketones, glycols acetals, epoxides and organic acids are

formed in smaller concentrations. This is of historic interest unlike the acetylene

rout; it has almost no chance to be used as a major process.


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2.4 SYNTHESIS GAS PROCESS

A rhodium catalyzed process capable by converting synthesis gas directly

into acetaldehyde in a single step was reported in 1974.

CO + H 2 CH 3CHO + other products

The process comprises synthesis gas over 5% rhodium on SiO 2 at 300oC

and 2.0 MPa(20 atm). The principle co products are acetaldehyde 24% are

acetaldehyde 24% acetic acid 20%, and ethanol 16%. If there is a substantialdegree of coal gasification, the interest in the use of synthesis gas as a raw

material for acetaldehyde production will increase.

2.5 ETHYL ALCOHOL PROCESSES

There are two commercial processes for the production of acetaldehyde

from ethyl alcohol. These are vapor phase oxidation of ethanol.

AgCH 3CHCH 2OH + O 2 CH 3CHO + H 2O

550 oC

In this process a mixture of ethyl alcohol vapors and oxygen are passed over

silver catalyst filled in tubes of multi-tubular fixed bed reactor. The reaction iscarried out at 550 oC and conversion of ethyl alcohol to acetaldehyde is 50-55%

per pass.

The second process is vapor phase dehydrogenation of ethanol.

Cr and CuC2H5OH CH 3CHO + H 2

260 to 290 oC


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In this process vapors of ethanol are reacted over a chromium copper

catalyst at atmospheric pressure and 260 to 290 oC temperature. The alcohol

conversion is 30 to 50% depending upon reaction temperature and alcohol flow

rate.

Out of these processes we have selected Ethylene Oxidation Process.

Process description is given below.

2.6 PROCESS DESCRIPTION


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CHAPTER-3

MATERIAL & ENERGYBALANCE

3.1 MATERIAL BALANCE

BASIS: 1000 Kg/hr production of acetaldehyde

REACTOR-R1Material entering with stream-8

C2H5OH = 863.26 Kg/hr = 18.766 Kgmol/hr

H2O = 45.43 Kg/hr = 2.524 Kgmol/hr

O2 = 635.28 Kg/hr = 19.852 Kgmol/hr

N2 = 2090.82 = Kg/hr = 74.62 Kgmol/hr

Chemical reaction involved isC2H5OH + O 2 CH 3CHO + H 2O

As conversion of C 2H5OH is 50% so

C2H5OH converted = 9.383 Kgmol/hr

C2H5OH unvonverted = 9.383 Kgmol/hr

O2 = converted = 9.383/2 = 4.692 Kgmol/hr

O2 = unconverted = 15.16 Kgmol/hr


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CH 3CHO formed = 9.383 Kgmol/hr

H2O = formed = 9.383 Kgmol/hr

Total water leaving = 2.524 + 9.383 = 11.907 Kgmol/hr

So material leaving with strea-9

C2H5OH = 9.383 Kgmol = 431.6 Kg

CH 3CHO = 9.383 Kgmol = 412.85 Kg

H2O = 11.907 Kgmol = 214.33 Kg

O2 = 15.16 Kgmol = 485.12 Kg

N2 = 74.67 Kgmol = 2090.82 Kg

Total material leaving = 3634 Kg/hrTotal material entering = 3634 Kg/hr

ABSORBER-A1

In first absorber 95% entering acetaldehyde will be absorbed

Material entering with stream-9

CH 3CHO = 422.85 Kg/hr

1110

149


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C2H5OH = 431.6 Kg/hr

H2O = 85.33 + 129 = 214.35 Kg/hr

O2 = 485.12 Kg/hr

N2 = 2090.82 Kg/hr

Material with stream-10


C2H5OH = 17.1 Kg/hr

O2 = 485.12 Kg/hr

N2 = 2090.82 Kg/hr

Material entering with stream-11H2O = 4064 Kg/hr

CH 3OHO = 20.43 Kg/hr

C2H5OH = 17 Kg/hr

Material leaving with stream-14


C2H5OH = 431.5 Kg/hrH2O = 4278.6 Kg/hr

Total material entering = 7736 Kg/hr

Total material leaving = 7736 Kg/hr


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DISTILLATION COLUMN-D1

Product Specifications

Top product

CH 3CHO = 99%

C2H5OH = 0.8%

H2O = 0.2%

There should be no CH 3CHO in bottomsMaterial entering with stream-14

CH 3CHO = 412.6 Kg/hr = 8.05%

C2H5OH = 431.58 Kg/hr = 8.4%

H2O = 4278.6 Kg/hr = 83.52%

Total = 5122.78 Kg/hr

So CH 3CHO balance

0.0805 (5122.78) = 0.99 (D)

D = 416.55 Kg/hr

So top product is = 416.55 Kg/hr

Bottom product = 4706.2 Kg/hr

C2H5OH in top product = 0.008 416.55

= 3.33 Kg/hr

H2O in top product = 0.002 416.55

15

16

14


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= 0.833

CH 3CHO in top product = 412.00 Kg/hr

Material leaving in bottom product

C2H5OH = 431.58 3.33 = 428.25 Kg/hr

H2O = 4278.6 0.833 = 4277.76 Kg

Total material leaving = 5122 Kg/hr

Total material entering = 5122 Kg/hr


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3.2 ENERGY BALANCE

VAPORIZER

Temperature of stream-A = 25 oC

Mass flow rate = 503 Kg/hr

Cp of 95% ethyl alcohol = 0.64 Kcal/Kg oC

So heat with stream-A = 503 0.64 25

= 8048 Kcal/hr.

Similarly, heat ith stream-B = 27263 Kcal/hr

So, heat with stream-C = 27263 + 8048

= 35311 Kcal/hr

Flow rate of stream-C = 908.7

C p = 0.73 Kcal/KgoC

Temperature of stream-C = Q/mC p

Separator

Vaporizer

G

A C

E

D

F

B


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=73.07.908

35311

= 53 oC

Stream-G is saturated liquid at 2.3 atmHeat with stream-G = Q = mC p T

= 227.1 0.92 112

= 23400 Kcal/hr

Heat with stream-D = 23400 + 35311

= 58711 Kcal/hr

Flow rate of stream-D = 1135.8 Kg/hr

Temperature of stream-D =78.08.1135

58711

= 66 oC

at 2.3 atm ethyl alcohol (95%) will be vaporized at 112 oC, so, we have to

supply heat to ethyl alcohol in vaporizer.

In vaporizer

Sensible heat

Q1 = mC p T

= 1135.8 0.87 (112 66)

= 45454.7 Kcal/hr

Latent heat

As only 80% ethyl alcohol (95%) is being vaporized so 908.7 Kg/hr of ethyl

alcohol will be vaporized.

Water vaporized = 0.05 908.7

= 45.43 Kg/hr

Latent heat of vaporization of water = 500 Kcal/hr

OH2

Q = 22717.5 Kcal/hr

Ethyl alcohol evaporated = 863.2 Kg/hr


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Latent heat of vaporization = 175 Kcal/kg

OHHC 52Q = 175 863.2 = 151071

Total heat to be supplied = 45454.7 + 22717.5 + 151071

= 219243.5

If steam is used at 130 oC latent heat of steam at 130 oC = 519.8 Kcal/kg

So, flow rate of steam = 219243.5/519.8

= 421 Kg/hr

Reactor

Standard heat of reaction = - 43 Kcal/hr

Heat of reaction at given conditions = 401860 Kcal/hr

So,

401860 Kcal/hr heat should be removed from reactor by cooling water.

Inlet temperature of cooling water = 25 oC

Outlet temperature of cooling water = 45 oC

Mass flow rate of water = m = ?

m =TC

Q

p

=201

401860 = 20093 Kg/hr

DISTILLATION COLUMN

Input = Output

WFHF + Q R = Q C + W BHB(l) + + W DHD(l)

WF = 256.4595 Kg-mol/hr

WB(l) = 246.9015 Kg-mol/hr

WD(l) = 9.5412 Kg-mol/hr

HF = 3145495 J/Kg-mol. hr

HB(l) = 3169709 Kg-mol/hr


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HD(l) = 1473400 Kg-mol/hr

QC = 111507000 J/hr

QR = 1105043000 J/hr

Putting in eq.

917196375 J/hr = 917196375 J/hr


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REACTOR DESIGN

FIXED BED CATALYTIC REACTORS

4.1 INTRODUCTION

Fixed-bed catalytic reactors have been aptly characterized as the

workhorses of me process industries. For economical production of largeamounts of product, they are usually the first choice, particularly for gas-phase

reactions. Many catalyzed gaseous reactions are amenable to long catalyst life

(1-10 years); and as the time between catalyst change outs increases, annualized

replacement costs decline dramatically, largely due to savings in shutdown

costs. It is not surprising, therefore, that fixed-bed reactors now dominate the

scene in large-scale chemical-product manufacture.

4.2 TYPES OF FIXED BED REACTOR

Fixed-bed reactors fall into one of two major categories:

Adiabatic or Non-adiabatic.

A number of reactor configurations have evolved to fit the unique

requirements of specific types of reactions and conditions. Some of the more

common ones used for gas-phase reactions are summarized in Table(4.1) and

the accompanying illustrations. The table can be used for initial selection of a

given reaction system, particularly by comparing it with the known systems

indicated.


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Table 4.1: Fixed-Bed Reactor Configurations for Gas-Phase Reactions

Classification Use Typical ApplicationsSingle adiabatic bed Moderately exothermic

orendothermic non-equilibriumlimited

Mild hydrogenation

Radial flow Where low AP isessentialand useful wherechangein moles is large

Styrene fromethylbenzene

Adiabatic beds in serieswith intermediatecooling or heating

High conversion,equilibriumlimited reactions

SO 2 oxidationCatalytic reformingAmmonia synthesisHydrocracking Styrenefrom ethylbenzene

Multi-tabularnon-adiabatic

Highly endothermic orexothermic reactionsrequiringclose temperaturecontrol toensure high selectivity

Many hydrogenationsEthylene oxidation toethylene oxide,formaldehyde

by methanol oxidation, phthalic anhydride production

Direct-firednon-adiabatic

Highly endothermic,high temperaturereactions

Steam reforming

4.4 SELECTION OF REACTOR TYPE

After analyzing different configuration of fixed bed reactors we have

concluded that for our system the most suitable reactors is multi tube fixed bed

reactor. Because oxidation of ethyl alcohol is highly exothermic reaction, so

cooling will be required otherwise the temperature of reactor will rise and due to

rise in temperature the catalyst activity and selectivity will be affected and in


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greater than that which can be transferred to the cooling fluid. Hence the

temperature of the reaction mixture will rise, causing an increase in the rate of

reaction. This continues as the mixture moves up the tube, until the

disappearance of reactants has a larger effect on the rate than the increase in

temperature. Farther along the tube the rate will decrease. The smaller amount

of heat can now be removed through the wall with the result that the

temperature decreases. This situation leads to a maximum in the curve of

temperature versus reactor-tube length.

Cooling(or Heating)fluid out

Cooling(or Heating)fluid in

Feed Stream

Product Stream


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Figure-4.1: Multi-tubular fixed bed reactor

4.6 EFFECT OF VARIABLES ON MULTI-TUBE FIXEDBED REACTOR

4.6.1 Particle Diameter

The overall heat transfer coefficient declines with decrease in particle size

in the usual practical range. Redial gradients increase markedly with decrease in

particle size. Small size, however, may improve rate or selectivity in some case

by making catalyst inner surface more accessible.

4.6.2 Tube Diameter

Reducing tube diameter reduces the radial profile. Heat transfer area per

unit volume is inversely proportion al to the tube diameter and reaction

temperature is affected by a change in this area.


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4.6.3 Outside Wall Coefficient

Improvement up to the point where this resistance becomes negligible

is worthwhile. Boiling liquids are advantageous because of the high heat

transfer coefficient.

4.6.4 Heat of Reaction and Activation Energy

Accurate values should be used since calculated temp. is sensitive to

both of these, particularly to the value of energy of activation. This roust bedetermined carefully over the range of interests, but calculated results should

be obtained based on different activation energies over the probable range of

accuracy for the data so that final equipment sizing can be done with a feel

for uncertainties.

4.6.5 Particle Thermal Conductivity

One of the mechanisms of radial heat transfer in a bed, conduction

through the solid packing which must quite logically depend on the thermal

conductivity of the bed, can be reasoned to have some dependence on the

thermal conductivity of the solid. But since it only affects one of the several

mechanisms, the proportionally cannot be direct. Differences in effective

conductivity and the wall heat transfer coefficient h between beds of packing

having high and low solid conductivity may be in the range of a factor of

2-3. The largest difference will occur at lower Reynolds numbers. Most catalyst

carriers have low conductivities, but some such as carbides have high

conductivities.


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4.7 DESIGN PROCEDURE FOR MULTI TUBE FIXEDBED REACTOR

To calculate weight of catalyst required

2

1AoFW A

A

X

X A

A

r dX

If space time is know then space time =rateflowVolumetric

reactor of Volume

By the knowledge of bulk density of catalyst and weight of catalyst

Calculate volume of reactor

Volume of reactor =catalystof density bulk

catalystof weight

Decide the dimensions of tube; keeping in mind that

particlecatalystof Dia tubeof Dia

> 30

Calculate volume of one tube and then number of tubes required


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SPECIFICATION SHEET

Identification

Item ReactorItem No. R-1

No. required 1

Function: Production of acetaldehyde by air oxidation of ethyl alcohol.

Operation: ContinuousType: Catalytic

Multi tube, fixed bed

Chemical Reaction:C2H5OH + O 2 CH 3CHO + H 2O

H298 = - 43 Kcal

Catalyst: Silver, coated on aluminaShape: SphericalSize: 1.25 mm

Tube side:Material handled Feed Product

(kg/hr) (kg/hr)C2H5OH 86326 432.58H2O 45.44 214.35CH3CHO ----- 412.8O2 635.28 484.96

N2 2090.82 2090.82Temp ( oC) 550 550

Tubes: No. 709Length 2.438 mO. D 63.5 mmPitch 79.37 mm patternMaterial of construction = copper


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Shell sideFluid handled = cooling waterTemperature 25 oC to 45 oC

ShellDia = 2.66 mMaterial of construction = Carbonsteel

Heat transfer area required = 77.67 m2

Overall heat transfer coefficient = 10.77 W/m 2 oC

CHAPTER-5

DESIGN OF ABSORBER

5.1 ABSORPTIONS

The removal of one or more component from the mixture of gases by

using a suitable solvent is second major operation of Chemical Engineering that

based on mass transfer.

In gas absorption a soluble vapours are more or less absorbed in the

solvent from its mixture with inert gas. The 'purpose of such gas scrubbing

operations may be any of the following;

a) For Separation of component having the economic value.

b) As a stage in the preparation of some compound.

c) For removing of undesired component (pollution).

5.2 TYPES OF ABSORPTION

1) Physical absorption,

2) Chemical Absorption.


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5.2.1 Physical Absorption

In physical absorption mass transfer take place purely by diffusion and

physical absorption is governed by the physical equilibria.

5.2.2 Chemical Absorption

In this type of absorption as soon as a particular component comes in

contact with the absorbing liquid a chemical reaction take place. Then by

reducing the concentration of component in the liquid phase, which enhances

the rate of diffusion.

5.3 TYPES OF ABSOR5SRS

There are two major types of absorbers which are used for absorption

purposes:

Packed column Plate column

5.4 COMPARISON BETWEEN PACKED AND PLATECOLUMN

1) The packed column provides continuous contact between vapour and

liquid phases while the plate column brings the two phases into contacton stage wise basis.

2) SCALE: For column diameter of less than approximately 3 ft. It is more

usual to employ packed towers because of high fabrication cost of small

trays. But if the column is very large then the liquid distribution is

problem and large volume of packing and its weight is problem.

3)

PRESSURE DROP: Pressure drop in packed column is less than the platecolumn. In plate column there is additional friction generated as the


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vapour passes through the liquid on each tray. If there are large No. of

Plates in the tower, this pressure drop may be quite high and the use of

packed column could effect considerable saving.

4) LIQUID HOLD UP: Because of the liquid on each plate there may be a

Urge quantity of the liquid in plate column, whereas in a packed tower

the liquid flows as a thin film over the packing.

5) SIZE AND COST: For diameters of less than 3 ft. packed tower require

lower fabrication and material costs than plate tower with regard to

height, a packed column is usually shorter than the equivalent plate

column.

From the above consideration packed column is selected as the absorber,

because in our case the diameter of the column is approximately 0.8 meter

which is less than 3 ft. As the solubility is infinity so the liquid will absorb as

much gases as it remain in contact with gases so packed tower provide more

contact. It is easy to operate.

5.5 PACKING

The packing is the most important component of the system. The packing

provides sufficient area for intimate contact between phases. The efficiency of

the packing with respect to both HTU and flow capacity determines to a

significance extent the overall size of the tower. The economics of theinstallation is therefore tied up with packing choice.

The packings are divided into those types which are dumped at random

into the tower and these which must be stacked by hand. Dumped packing

consists of unit 1/4 lo 2 inches in major dimension and are used roost in the

smaller columns. The units in stacked packing are 2 to about 8 inches in size,

they are used only in the larger towers.


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32

The Principal Requirement of a Tower packing are:

1) It must be chemically inert to the fluids in the tower.

2) It must be strong without excessive weight.

3) It must contain adequate passages for both streams without excessive

liquid hold up or pressure drop.

4) It must provide good contact between liquid and gas.

5) It must be reasonable in cost.

Thus most packing are made of cheap, inert, fairly light materials such as

clay, porcelain, or graphite. Thin-walled metal rings of steel or aluminum are

some limes used.

Common Packings are:

a) Berl Saddle.

b) Intalox Saddle.

c) Rasching rings.d) Lessing rings.

e) Cross-partition rings.

f) Single spiral ring.

g) Double - Spiral ring.

h) Triple - Spiral ring.

5.6 DESIGNING STEPS FOR ABSORPTION COLUMN

Determining the approximate dia of the column Selection of column. Selection of packing and material Calculating the size of packing

Calculating the actual dia of column


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33

Calculating the flooding velocity

a) Finding loading velocity with the knowledge the flooding velocity

b) Calculating actual dia of column

Finding the no. of transfer units (No G) Determining the height of packing Determining the height of the column Determining the pressure drop.

by equation P =G

2F

b

g10a

[in. water /ft of packing]

SPECIFICATION SHEET

Identification

Item: Packed Absorption ColumnItem No. A1

No. required 01

Function: To absorb acetaldehyde and ethyl alcohol in water.

Operation: Continuous

MaterialHandled

Entering gasKg/hr

Exit gasKg/hr

LiquidenteringKg/hr

LiquidleavingKg/hr

CH 3CHO 412.8 20.64 20.43 412.6C2H5OH 431.58 17.1 17 414.48


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34

H2O 85.35 ------- 4064 4278.6O2 484.96 484.96 ------- ------

N2 2090.82 2090.82 ------- ------

Design Data No. of transfer units = 7Height of transfer units = 0.2 ft (0.06 m)Height of packing section = 6.44 ft (1.96 m)Total height of column = 15 ft (4.5 m)Inside diameter = 2.62 ft (0.8 m)Flooding velocity = 2.36 m/secMaximum allowable gas velocity = 1.416 m/secPressure drop = 20 mmH 2O/m of packing

InternalsSize and type = 66 mm, intalox saddleMaterial of packing: CeramicMethod of packing: (wet) float into tower filled with water.Packing arrangement: dumpedType of packing support: gas injection supportType of liquid distributor: Weir flow distributor


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DESIGN OF DISTILLATIONCOLUMN

In industry it is common practice to separate a liquid mixture by distillating the

components, which have lower boiling points when they are in pure condition

from those having higher boiling points. This process is accomplished by partial

vaporization and subsequent condensation.

6.1 CHOICE BETWEEN PLATE AND PACKED COLUMN

Vapour liquid mass transfer operation may be carried either in plate

column or packed column. These two types of operations are quite different. A

selection scheme considering the factors under four headings.

i) Factors that depend on the system i.e. scale, foaming, fouling factors,

corrosive systems, heat evolution, pressure drop, liquid holdup.

ii) Factors that depend on the fluid flow moment.

iii) Factors that depends upon the physical characteristics of the column

and its internals i.e. maintenance, weight, side stream, size and cost.

iv) Factors that depend upon mode of operation i.e. batch distillation,

continuous distillation, turndown, intermittent distillation.

The relative merits of plate over packed column are as follows:

i) Plate column are designed to handle wide range of liquid flow rates

without flooding.


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36

ii) If a system contains solid contents, it will be handled in plate column,

because solid will accumulate in the voids, coating the packing

materials and making it ineffective.

iii) Dispersion difficulties are handled in plate column when flow rate of

liquid are low as compared to gases.

iv) For large column heights, weight of the packed column is more than

plate column.

v) If periodic cleaning is required, man holes will be provided for

cleaning. In packed columns packing must be removed before

cleaning.vi) For non-foaming systems the plate column is preferred.

vii) Design information for plate column are more readily available and

more reliable than that for packed column.

viii) Inter stage cooling can be provide to remove heat of reaction or

solution in plate column.

ix) When temperature change is involved, packing may be damaged.

For this particular process, Acetaldehyde, ethyl alcohol and water system, I

have selected plate column because:

i) System is non-foaming.

ii) Temperature is high (91 o C).

6.2 CHOICE OF PLATE TYPE

There are four main tray types, the bubble cap, sieve tray, ballast or valve

trays and the counter flow trays. I have selected sieve tray because:

i) They are lighter in weight and less expensive. It is easier and cheaper

to install.

ii) Pressure drop is low as compared to bubble cap trays.


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37

iii) Peak efficiency is generally high.

iv) Maintenance cost is reduced due to the ease of cleaning.

6.3 DESIGNING STEPS OF DISTILLATION COLUMN

Calculation of Minimum Reflux Ratio R m. Calculation of optimum reflux ratio. Calculation of theoretical number of stages. Calculation of actual number of stages.

Calculation of diameter of the column. Calculation of weeping point. Calculation of pressure drop. Calculation of thickness of the shell. Calculation of the height of the column.

SPECIFICATION SHEET

Identification:Item Distillation column

Item No. DC1

No. required 1

Tray type Sieve tray

Function : Recovery of Acetaldehyde

Operation: Continuous


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38

Material handled

Feed Top Bottom

Quantity 256.4595 Kgmol/hr 9.5412 Kgmol/hr 246.9015

Kgmol/hr

Composition of

acetaldehyde

3.66% 98.2% 0

Temperature 91 oC 20 o C 96 oC

Design Data

No. of trays = 12 hole area/active area = 0.10Pressure = 1 atm weir length = 0.5867 m

Height of column = 4.3 m weir length = 25.4 mm

Diameter of column = 0.762 m reflux ratio = 3.5:1

Hole size = 3.175mm tray spacing = 0.3048 m

Tray thickness = 3mm Down comer area = 4.56912 . 10 -2 m2

Flooding = 53 % Hole area = 0.045576 m 2

Active area = 0.34638 m 2

CHAPTER-7

DESIGN OF HEATEXCHANGERS

7.1 INTRODUCTION

A heat exchanger is a heat-transfer devise that is used for transfer of

internal thermal energy between two or more fluids available at different


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39

temperatures. In most heat exchangers, the fluids are separated by a heat-

transfer surface, and ideally they do not mix. Heat exchangers are used in the

process, power, petroleum, transportation, air conditioning, refrigeration,

cryogenic, heat recovery, alternate fuels, and other industries. Common

examples of heat exchangers familiar to us in day-to-day use are automobile

radiators, condensers, evaporators, air pre-heaters, and oil coolers.

In our project a number of heat exchangers are used . Here we will

discuss heat exchanger used as

Condenser Vaporizer Preheater

All of these are shell and tube heat exchangers.

Selection Guide To Heat Exchanger Types

Type Significant feature Applications bestsuited

Limitations

Approximaterelative cost

in carbonsteel

construction

Fixed tubesheet Both tube sheets fixed toshell.

Condensers; liquid-liquid; gas-gas; gas-liquid; cooling and

heating, horizontal orvertical, reboiling.

Temperature difference

at extremes of about 200oF Due to differentialexpansion.

1.0

Floating heador tubesheet(removable

andnonremovable

bundles)

One tubesheet floats inshell or with shell, tube bundle may or may not

be removable from shell, but back cover can beremoved to expose tube

ends.

High temperaturedifferentials, above

about 200 oF extremes;dirty fluids requiringcleaning of inside as

well as outside of shell,horizontal or vertical.

Internal gaskets offerdanger of leaking.

Corrosiveness of fluidson shell-side floating

parts. Usually confinedto horizontal units.

1.28

U-tube;U-Bundle

Only one tube sheetrequired. Tubes bent in

U-shape. Bundle isremovable.

High temperaturedifferentials, which

might require provisionfor expansion in fixed

Bends must be carefullymade, or mechanical

damage and danger ofrupture can result. Tube

0.9-1.1


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40

tube units. Easilycleaned conditions on

both tube and shell side.

side velocities can causeerosion of inside of

bends. Fluid should befree of suspended

particles.

Double pipe

Each tube has own shellforming annular space

for shell side fluid.Usually use externally

finned tube.

Relatively small transferarea service, or in banksfor larger applications.Especially suited for

high pressures in tube(greater than 400 psig).

Services suitable forfinned tube. Piping-up a

large number oftenrequires cost and space.

0.8-1.4

Pipe coil

Pipe coil for submersionin coil-box of water orsprayed with water is

simplest type ofexchanger.

Condensing, orrelatively low heat loads

on sensible transfer.

Transfer coefficient islow, requires relativelylarge space if heat load

is high.

0.5-0.7

Plate andframe

Composed of metal-formed thin plates

separated by gaskets.Compact, easy to clean.

Viscous fluids, corrosivefluids, slurries, high heat

transfer.

Not well suited for

boiling or condensing;limit 350-500 oF by

gaskets. Used for liquid-liquid only; not gas-gas.

0.8-1.5

Spiral

Compact, concentric plates; no bypassing,

high turbulence.Cross-flow, condensing,

heating.Process corrosion,

suspended materials.0.8-1.5

7.2 SHELL AND TUBE HEAT EXCHANGER

In process industries, shell and tube exchangers are used in greatnumbers, far more than any other type of exchanger. More than 90% of heat

exchangers used in industry are of the shell and tube type. The shell and tube

heat exchangers are the work horses of industrial process heat transfer. They

are the first choice because of well-established procedures for design and

manufacture from a wide variety of materials, many years of satisfactory

service, and availability of codes and standards for design and fabrication. Theyare produced in the widest variety of sizes and styles. There is virtually no limit

on the operating temperature and pressure.

7.2.1 Classification of Shell and Tube Heat Exchangers

There are four basic considerations in choosing a mechanical

arrangement that provides for efficient heat transfer between the two fluids

while taking care of such practical matters as preventing leakage from one intothe other.


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41

1) Consideration for differential thermal expansion of tubes and shell.

2) Means of directing fluid through the tubes.

3) Means of controlling fluid flow through the shell.

4) Consideration for ease of maintenance and servicing.

Heat exchangers have been developed with different approaches to these

four fundamental design factors. Three principal types of heat exchangers

2) Fixed tube-sheet exchangers

3) U-tube exchangers and

4) Floating head exchangers satisfy these design requirements.

Design procedure for shell-and-tube heat exchangers


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7.3 VAPORIZERS

Vaporizers are heat exchangers which are specially designed to supply

latent heat of vaporization to the fluid. In some cases it can also preheat the

fluid then this section of vaporizers will be called upon preheating zone and the


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43

other section in which latent heat is supplied; is known as vaporization zone but

he whole assembly will be called a vaporizer.

Vaporizers are called upon to fulfill the multitude of latent-heat serviceswhich are not a part of evaporative or distillation process.

There are two principal types of tubular vaporizing equipment used in

industry: Boilers and Vaporizing Exchangers. Boilers are directly fired tubular

apparatus, which primarily convert fuel energy into latent heat of vaporization.

Vaporizing Exchangers are unfired and convert latent or sensible heat of one

fluid into the latent heat of vaporization of another. If a vaporizing exchanger is

used for the evaporation of water or an aqueous solution, it is now fairly

conventional to call it an Evaporator, if used to supply the heat requirements at

the bottom of a distilling column, whether the vapor formed be steam or not, it

is a Re-boiler; when not used for the formation of steam and not a part of a

distillation process, a vaporizing exchanger is simply called a vaporizer. So any

unfired exchanger in which one fluid undergoes vaporization and which is not a

part of an evaporation or distillation process is a vaporizer.

7.4 TYPES OF VAPORIZERS

Some common types of vaporizers are

Vertical vaporizer

Indirect fluid heater Tubular low temperature vaporizer Electrical resistance vaporizer Cryogenic vaporizer

The commonest type of vaporizer is the ordinary horizontal 1-2

exchanger or one of its modifications, and vaporization may occur in the shell

or in the tubes. If steam is the heating medium, the corrosive action of air in the


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44

hot condensate usually makes it advantageous to carry out the vaporization in

the shell.

In the case of vaporizer, however, operation is often at high pressure, andit is usually too expensive to provide disengagement space in the shell, since the

inclusion of disengagement space at high pressures correspondingly increases

the shell thickness. For this reason vaporizers are not usually designed for

internal disengagement. Instead some external means. Such as an inexpensive

welded drum, is connected to the vaporizer where in the entrained liquid is

separated from the vapor.

When a 1-2 exchanger is used as a vaporizer, it is filled with tubes and

cannot be adapted for blow down, since all the feed to a vaporizer is usually of

value and a rejection as blow down is prohibitive. If the feed were completely

vaporized in the vaporizer, it would emerge as a vapor and any dirt which a was

originally present would be left behind on the tube surface over which total

vaporization of occurred, fouling it rapidly, If the 1-2 exchanger (vaporization)

were over-designed, that is, if it contained too much surface, disengagement

would have to occur on the tubes and due to the excess surface the vapor would

superheat above its saturation temperature.

The feed to a vaporizer should not be vaporized completely. The value of

this rule is apparent. If less that 100 percent to the feed is vaporized in 1-2exchangers, the residual liquid can be counted on to prevent the accumulation of

dirt directly on the surface of the heating element. A maximum of about 80

percent vaporization appears to provide favorable operation in 1-2 exchanges,

although higher percentages may be obtained in vessels having interval

disengagement space.


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45

Forced and Natural circulation Vaporizer. When liquid is fed to is fed

by forced circulation. The circuit consists of a 1-2 exchanger serving as the

vaporizer and a disengaging drum from which the un-vaporized liquid is

withdrawn and recombined with fresh feed. The generated vapor is removed

form the top of the drum.

The vaporized may also be connected with a disengaging drum without

the use of a reticulating pump. This scheme is natural circulation. It requires

that the disengaging drum be elevated above the vaporizer. The advantages of

forced circulation or natural circulation are in part economics and a part dictated

by space. The forced-circulation arrangement requires the use of a pump with its

continuous operating cost and fixed charges. As with forced-circulation

evaporators, the rate of feed recirculation can be controlled very closely. If the

installation is small, then use of a pump preferable. If a natural-circulation

arrangement is used pump and stuffing box problems are eliminated but

considerably more headroom must be provided and recirculation rates cannot be

controlled so readily.

The vaporization of a cold liquid coming from storage, the liquid may not

be at its boiling point and may require preheating to the boiling point. Since the

shell of a forced-circulation vaporizer is essentially the same as any other 1-2

exchangers, the preheating can be done in the same shell as the vaporization. If

the period of performance of a vaporizer is to be measured by a single overall

dirt factor, it is necessary to divide the shell surface into two successive zones,

one for preheating and one for vaporization.

The true temperature difference is the weighted temperature difference

for the two zones, and the clean coefficient is the weighted clean coefficient.

Vaporizers tend to accumulate dirt, and for his reason higher circulation

rates and large dirt factors will often be desirable. Preference should be given to


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46

the use of square pitch and a removable tube bundle. Although it may reduce

the possibility of using a 1-2 vaporizing exchanger for other services, the baffle

spacing can be increased or staggered form inlet to outlet to reduce the pressure

drop of the fluid vaporizing in the shell.

SPECIFICATION SHEET FOR VAPORIZER

Identification

Unit Vaporizer

Item No. V-1

Type Forced Circulation

No. of Item 1

Function To vaporize the alcohol

Operation Continuous

Heat duty 905318.7 Btu/hr

Heat transfer area 260.7 ft 2

Overall heat transfer coefficient 88 Btu/hr-ft 2 oF

Dirt factor 0.003hr-ft 2 oF/Btu


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47

Shell side Tube sideFluid circulated Ethyl alcohol SteamFlow rates 2501.76 lb/hr 966.7 lb/hrTemperature Inlet = 150.8 oF

Outlet = 233.6o

F

266 o F

Pressure 44.1 psi 39 psiPressure drop 1.3 psi 0.035 psiMaterial of construction Carbon steel Carbon steelSpecifications I.D = 17.25 in

C = 0.25 inB = 4 in

OD = in 16 BWGPitch = 1 inSquare arrangement,Length = 8 ft

N t = 166

7.5 CONDENSERS

Introduction

A condenser is a two-phase flow heat exchanger in which heat is generated from

the conversion of vapor into liquid (condensation) and the heat generated is

removed from the system by a coolant. Condensers may be classified into twomain types: those in which the coolant and condensate stream are separated by a

solid surface, usually a tube wall, and those in which the coolant and

condensing vapor are brought into direct contact.

The direct contact type of condenser may consist of a vapor which is

bubbled into a pool of liquid, a liquid which is sprayed into a vapor, or a

packed-column in which the liquid flows downwards as a film over a packing

material against the upward flow of vapor. Condensers in which the streams are

separated may be subdivided into three main types: air-cooled, shell-and-tube,

and plate. In the air-cooled type, condensation occurs inside tubes with cooling

provided by air blown or sucked across the tubes. Fins with large surface areas

are usually provided on the air side to compensate for the low air-side heat

transfer coefficients. In shell-and-tube condensers, the condensation may occur


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48

inside or outside the tubes. The orientation of the unit may be vertical or

horizontal. In the refrigeration and air-conditioning industry, various types of

two-phase flow heat exchangers are used. They are classified according to

whether they are coils or shell-and-tube heat exchangers. Evaporator and

condenser coils are used when the second fluid is air because of the low heat

transfer coefficient on the air side.

In the following sections, the basic types of condensers are shown:

Four Condenser Configuration are Possible

1) Horizontal with condensation is shell side and cooling medium in the

tubes.

2) Horizontal with condensation in tube side cooling medium in shell

side.

3) Vertical with condensation in the shell.

4) Vertical with condensation in the tubes.

Horizontal shell side and vertical tube side are the most commonly used

types of condensers.

In this process we have used the normal mechanism for heat transfer in

commercial condenser which film wise condensation.

Since vapor-liquid heat transfer changes usually occur at constant or

really constant pressure in industry, the vaporization or condensation of a single

compared normally occurs isothermally.

If a mixture of vapors instead of a pure vapor is condensed at constant

pressure, the change does not take place isothermally in most instances.


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50

Utilities: Cold water

Ud assumed = 100 Btu/hr-ft - oF Ud calculated 109 Btu/hr-ft - oF

Uc calculated = 163 Btu/hr-ft - oF Allowed dirt factor = Rd = 0.003

CHAPTER-8

PUMP AND COMPRESSOR

SELECTION

8.1 FACTORS AFFECTING CHOICE OF A PUMP

Many different factors can influence the final choice of a pump for a

particular operation. The following list indicates the major factors that govern

pump selection..

1) The amount of fluid that must be pumped. This factor determines the size

of pump (or pumps) necessary.

2) The properties of the fluid. The density and the viscosity; of the fluid

influence the power requirement for a given set of operating conditions,

corrosive properties of the fluid determine the acceptable materials ofconstruction. If solid particles are suspended in the fluid, this factor

dictates the amount of clearance necessary and may eliminate the

possibility of using certain types of pumps.

3) The increase in pressure of the fluid due to the work input of the pumps.

The head change across the pump is influenced by the inlet and

downstream reservoir pressures, the change in vertical height of the


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51

delivery line, and frictional effects. This factor is a major item in

determining the power requirements.

4) Type of flow distribution. If nonpulsating flow is required, certain types

of pumps, such as simplex reciprocating pumps, may be unsatisfactory.

Similarly, if operation is intermittent, a self-priming pump may be

desirable, and corrosion difficulties may be increased.

5) Type of power supply. Rotary positive-displacement pumps and

centrifugal pumps are readily adaptable for use with electric-motor or

internal-combustion-engine drives; reciprocating pumps can be used withsteam or gas drives.

6) Cost and mechanical efficiency of the pump.

PUMP P-1

The duty of P-I is to pump ethyl alcohol from 1 atm to 2.3 atm with a flow rareof 1135.8 Kg/hr. for this purpose the best choice is centrifugal pump because

the required pressure is not so high.

PUMP P-2

The duty of pump-2 is to pump a mixture of water, ethyl alcohol and

acetaldehyde with slight pressure development and the flow late required is

5122.78 Kg/hr. Centrifugal pump is most suitable pump for such a service i.e.

high flow rate and low pressure development.


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52

8.2 COMPRESSOR SELECTION

Compressor C-1

The duty of compressor is to compress the air from 1 atm to 2.3 atm and to

made the air flow with flow rate 2726 Kg/hr/

As compression ratio is less than 5 so, single stage compressor will be

sufficient and type of compressor suitable for this situation is centrifugal

compressor, because our objective is to develop just 2.3 at m pressure with

relatively high flow rate.

CHAPTER-9


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54

Like temperature pressure is a valuable indication of material state and

composition. In fact, these two measurement considered together are the

primary evaluating devices of industrial materials.

Pumps, compressor and other process equipment associated with pressure

changes in the process material are furnished with pressure measuring devices.

Thus pressure measurement becomes an indication of energy increase or

decrease.

Most pressure measurement in industry are elastic element devices, either

directly connected for local use or transmission type to centralized location.

Most extensively used industrial pressure element is the Bourderi Tube or a

Diaphragm or Bellows gauges.

9.3 FLOW MEASUREMENT AND CONTROL

Flow-indicator-controllers are used to control the amount of liquid. Alsoall manually set streams require some flow indication or some easy means for

occasional sample measurement. For accounting purposes, feed and product

stream are metered. In addition utilities to individual and grouped equipment are

also metered.

Most flow measures in the industry are/ by Variable Head devices. To a

lesser extent Variable Area is used, as are the many available types as special

metering situations arise. .

9.4 CONTROL SCHEMES OF DISTILLATION COLUMNGENERAL CONSIDERATION

9.4.1 Objectives


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55

In distillation column control any of following may be the goals to

achieve

1. Over head composition.

2. Bottom composition

3. Constant over head product rate. .

4. Constant bottom product rate.

9.4.2 Manipulated Variables

Any one or any combination of following may be the manipulated

variables

1. Steam flow rate to reboiler.

2. Reflux rate.

3. Overhead product withdrawn rate.

4. Bottom product withdrawn rate

5. Water flow rate to condenser.

9.5 LOADS OR DISTURBANCES

Following are typical disturbances

1. Flow rate of feed

2. Composition of feed.

3. Temperature of feed.

4. Pressure drop of steam across reboiler

5. Inlet temperature of water for condenser.


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56

9.6 CONTROL SCHEME

Overhead product rate is fixed and any change in feed rate must be

absorbed by changing bottom product rate. The change in product rate is

accomplished by direct level control of the reboiler if the stream rate is fixed

feed rate increases then vapor rate is approximately constant & the internal

reflux flows must increase.

ADVANTAGE

Since an increase in feed rate increase reflux rate with vapor rate beingapproximately constant, then purity of top product increases.

DISADVANTAGE

The overhead reflux change depends on the dynamics of level control system

that adjusts it.


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57

Figure: Control scheme

CHAPTER-10

HAZOP STUDY


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58

INTRODUCTION

A HAZOP survey is one of the most common and widely accepted methods of

systematic qualitative hazard analysis. It is used for both new or existing

facilities and can be applied to a whole plant, a production unit, or a piece of

equipment It uses as its database the usual sort of plant and process information

and relies on the judgment of engineering and safety experts in the areas with

which they are most familiar. The end result is, therefore reliable in terms

of engineering and operational expectations, but it is not quantitative and may

not consider the consequences of complex sequences of human errors.

The objectives of a HAZOP study can be summarized as follows:

1) To identify (areas of the design that may possess a significant hazard

potential.

2) To identify and study features of the design that influence the

probability of a hazardous incident occurring.

3) To familiarize the study team with the design information available.

4) To ensure that a systematic study is made of the areas of significant

hazard potential.

5) To identify pertinent design information not currently available to the

team.

6) To provide a mechanism for feedback to the client of the study team's

detailed comments.

A HAZOP study is conducted in the following steps:


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60

Equipment, piping, and instrument specifications Process control logic diagrams Layout drawings

Operating procedures Maintenance procedures

Emergency response procedures

Safety and training manuals


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61

Table-10.2: HAZOP Guide Words and Meanings

Guide Words Meaning

No

Less

More

Negation of design intent

Quantitative decrease

Quantitative increase


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62

Part of

As well as

Reverse

Other than

Qualitative decrease

Qualitative Increase

Logical opposite of the intent

Complete substitution

4) Conduct the study. Using the information collected, the unit is divided

into study "nodes" and the sequence diagrammed in Figure , is

followed for each node. Nodes are points in the process where process

parameters (pressure, temperature, composition, etc.) have known andintended values. These values change between nodes as a result of the

operation of various pieces of equipment' such as distillation columns,

heat exchanges, or pumps. Various forms and work sheets have been

developed to help organize the node process parameters and control

logic information.

When the nodes are identified and the parameters are identified, each

node is studied by applying the specialized guide words to each parameter.

These guide words and their meanings are key elements of the HAZOP

procedure. They are listed in Table(10.1).

Repeated cycling through this process, which considers how and why

each parameter might vary from the intended and the consequence, is thesubstance of the HAZOP study.

5) Write the report. As much detail about events and their consequence

as is uncovered by the study should be recorded. Obviously, if the

HAZOP identifies a not improbable sequence of events that would

result in a disaster, appropriate follow-up action is needed. Thus,


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64

Figure-10.2: Piping and instrumentation diagram

Deviationsfrom

operating

conditions

What event could causethis deviation

Consequences of thisdeviation on item of

equipment under

consideration

Processindications

Ethyl AlcoholStorage Tank


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65

Level:

Less

More

Temperature:

Less

More

Tank runs dry

Rupture of discharge line

V-3 open or broken

V-1 open or broken

Tank rupture (busting of

vessel)

Unload too much fromcolumn

Reverse flow from

process

Temperature of inlet is

colder than normalTemperature of inlet is

hotter than normal

External fire

Pump cavitates

Reagent released

Reagent released

Reagent released

Reagent released

Tank overfills

Tank overfills

Possible vacuum

Region released

Tank fails

LIA-1

FICA-1

LIA-1,

FICA-1

LIA-1

LIA-1

LIA-1

LIA-1

LIA-1

CHAPTER-11


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66

ENVIRONMENTAL IMPACTASSESSMENT

HEALTH HAZARD INFORMATION

Acute Effects:

The primary acute (short-term) effect of inhalation exposure to acetaldehyde is

irritation of the eyes, skin, and respiratory tract in humans. Erythema, coughing,

pulmonary edema, and necrosis may also occur and, at extremely high

concentrations, respiratory paralysis and death.

Acute inhalation of acetaldehyde resulted in a depressed respiratory rate

and elevated blood pressure in experimental animals.

Tests involving acute exposure of animals, such as the LC 50 and LD 50

tests in rats, rabbits, and hamsters, have demonstrated acetaldehyde to have low

acute toxicity from inhalation and moderate acute toxicity from oral or dermal

exposure.

Chronic Effects (Noncancer)

In hamsters, chronic (long-term) inhalation exposure to acetaldehyde has

produced changes in the nasal mucosa and trachea, growth retardation, slight

anemia, and increased kidney weight.


67/124

Appendix-A

67

Symptoms of chronic intoxication of acetaldehyde in humans resemble

those of alcoholism.

The RfC for acetaldehyde is 0.009 mg/m3 based on degeneration of

olfactory epithelium in rats.

EPA has medium confidence in the principal studies because appropriate

histopathology was performed on an adequate number of animals and a no-

observed-adverse-effect level (NOAEL) and a lowest-observed-adverse-effect

level (LOAEL) were identified, but the duration was short and only one specieswas tested; low confidence in the database due to the lack of chronic data

establishing NOAELs and due to the lack of reproductive and developmental

toxicity data; and, consequently, low confidence in the RfC.

EPA has not established an RfD for acetaldehyde

Reproductive/Developmental Effects

No information is available on the reproductive or developmental effects of

acetaldehyde in humans. Acetaldehyde has been shown, in animals, to cross the

placenta to the fetus.

Data from animal studies suggest that acetaldehyde may be a potential

developmental toxin. In one study, a high incidence of embryonic resorptions

was observed in mice injected with acetaldehyde. In rats exposed to

acetaldehyde by injection, skeletal malformations, reduced birth weight, and

increased postnatal mortality have been reported.

Cancer Risk


68/124

Appendix-A

68

Human data regarding the carcinogenic effects of acetaldehyde are inadequate.

Only one epidemiology study is available that several limitations including

short duration, small number of subjects, and concurrent exposure to other

chemicals and cigarettes.

An increased incidence of nasal tumors in rats and laryngeal tumors in

hamsters has been observed following inhalation exposure to acetaldehyde.

EPA has classified acetaldehyde as a Group B2, probable human

carcinogen.

EPA uses mathematical models, based on human and animal studies, to

estimate the probability of a person developing cancer from breathing air

containing a specified concentration of a chemical. EPA calculated an inhalation

unit risk estimate of 2.2 H 10-6 (m g/m3)-1. EPA estimates that, if an individual

were to breathe air containing acetaldehyde at 0.5 m g/m3* over his or her

entire lifetime, that person would theoretically have no more than a one-in-a-million increased chance of developing cancer as a direct result of breathing air

containing this chemical. Similarly, EPA estimates that breathing air containing

5.0 m g/m3 would result in not greater than a one-in-a-hundred thousand

increased chance of developing cancer, and air containing 50.0 m g/m3 would

result in not greater than a one-in-ten thousand increased chance of developing

cancer.

EPA's Office of Air Quality Planning and Standards, for a hazard ranking

under Section 112(g) of the Clean Air Act Amendments, has ranked

acetaldehyde in the nonthreshold category. The 1/ED10 value is 0.033 per

(mg/kg)/d and this would place it in the low category under Superfund's ranking

for carcinogenic hazard.


69/124

Appendix-A

69

ATMOSPHERIC PERSISTENCE

Acetaldehyde exists in the atmosphere in the gas phase. It also can be formed in

the atmosphere as a result of photochemical oxidation of organic pollutants in

urban atmospheres. The dominant atmospheric loss process for acetaldehyde is

by reaction with the hydroxyl radical. Based on this reaction, the atmospheric

half-life and lifetime is estimated to be 15 hours and 22 hours, respectively. The

products of this reaction include formaldehyde and peroxyacetyl nitrate (PAN).

CHAPTER-12

COST ESTIMATION

An acceptable plant design must present a process that is capable of operating

under conditions which will yield a profit.0^ Since, Net profit total income-all

expenses

It is essential that chemical engineer be aware of the many different types

of cost involved in manufacturing processes. Capital must be allocated for direct


70/124

Appendix-A

70

plant expenses; such as those for raw materials, labor, and equipment. Besides

direct expenses, many other indirect expenses are incurred, and these must be

included if a complete analysis of the total cost is to be obtained. Some

examples of these indirect expenses are administrative salaries, product

distribution costs and cost for interplant communication.

12.1 ESTIMATION OF EQUIPMENT COST

Equipment Cost (Rs.)

Vaporizer V-I 290436

Exchanger E-I 154427

Exchanger E-2 183702

Heater E-3 175501

Heater E-4 279200Cooler E-5 193459

Pre-heater E-6 61770

Condenser E-7 70890

Condenser E-8 1283730

Re-boiler E-9 938765

Re-boiler E-10 1415840


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Appendix-A

71

Distillation Column D-1 7748874

Distillation Column D-2 11069820

Absorber A-1 7431117

Absorber A-2 9085370

12.2 ESTIMATION OF TOTAL CAPITAL INVESTMENT

Direct Cost (Rs)

Purchased equipment cost = Rs. 40382901

Purchased equipment installation = 0.47 40382901 = Rs. 18979963

Instrumentation & Process Control = 0.12 40382901 = Rs. 2277595

Piping (installed) = 0.66 40382901 = Rs. 26652714

Building (Including Services) = 0.18 40382901 = Rs. 7268922

Yard improvements = 0.1 40382901 = Rs. 4038290

Service facilities (installed) = 0.7 40382901 = Rs. 5088245

Land = 0.06 40382901 = Rs. 305294

Total direct plant cost = Rs. 104993924

Indirect Cost

Engg & Supervision = 0.33 40382901 = Rs. 13326357

Construction expenses = 0.41 40382901 = Rs. 16556989


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Appendix-A

72

Total Indirect Cost = Rs. 29883346

Total Direct & Indirect Cost = Rs. 134877270

Contractors fee = 0.05 134877270 = Rs. 6743863

Contingency = 0.1 134877270 = Rs. 13487727

Fixed Capital Investment = Total direct + indirect cost + contigency +

Contractors fee

= Rs. 155108860

Total Capital Investment = F.C.I + W.C.

Now

W.C = 0.15 (T.C.I)

= 0.15 (155108860 + W.C)

W.C = Rs. 27372151

T.C.I = 155108860 + 27372151

= Rs. 182481011


73/124

Appendix-A

73

APPENDIX-AA-1) DESIGN CALCULATIONS OF MULTI-TUBULAR

FIXED BED REACTOR

PRODUCTCH 3CHO = 412.8 Kg/hrC2H5OH = 431.58 Kg/hrH2O = 214.35 Kg/hrO2 = 484.96 Kg/hr

N2 = 2090.8 K /hr

Cooling Water in

Cooling Water Out


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Appendix-A

74

Volume of Reactor

Volumetric flow rate of feed to reactor = V o = 63.84 m3/min

Space velocity = S = 15 min -1

as we know that

S = V o/V where, V = Volume of reactor.

V = V o/ S

= 63.84/15 = 4.256 m 3

Weight of Catalyst

(Silver Catalyst on Alumina Support of size 1.25 mm is used)

volume of reactor = 4.256 m 3

porosity = 0.4

so volume of catalyst = 0.6 4.256 = 2.5536 m 3

particle Density of catalyst = 2250 Kg/m 3

mass of catalyst = 2250 2.553 b= 5746 Kg

Number of Tubes

Length of tube = 8 ft = 2.439 m

To calculate tube dia

As we know that to prevent deviation from plug flow assumption


75/124

Appendix-A

75

D t/D p > 30

Where D t = dia of tube

D p = dia of particle

Let inside dia of tube = 2.204 in = 55.98 mm

D t/D p = 55.98/1.25 = 44.78 which is satisfactory

Volume of one tube = /4 D t2 L t

= 3.14/4 (55.98/1000) 2 2.439

= 0.785 0.00313 2.439

= 0.006 m 3

As total volume = 4.256 m 3

So number of tubes required = 709 tubes

Diameter of Shell

To calculate shell dia eq. (from Ludwig)

2t

431st22

1s

TP1.223

K nK K -DP-K 4

K -D N

where N T = number of tubes = 709

Ds = shell dia = ?

PT = pitch = 1.25 0.1 of tube

= 1.25 2.5

= 3.125 in. (76.2 mm)

for this pitch

K 1 = 1.08 K 2 = - 0.9

K 3 = 0.69 K 4 = - 0.8

n = 1 ( 1 tube pass)

By solving above eq.

Ds = 104.72 in.


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Appendix-A

76

= 8.72 ft = 2.66 meter

Shell Height

Length of tube = 2.439 m

Leaving 20 % spacing above and below

So height of shell = 2 (0.2 2.439) + 2.439

= 3.415 m

Pressure Drop

GD

1GD

G1L

P

Pf P3

= porosity = 0.4

DP = particle dia = 1.25 mm = 0.125 cm

Lf = feed density = 0.000948 g/cm3

G = mass velocity = 0.0579 g/cm 2 Sec

= viscosity of feed = 0.000343 g/cm. Sec

C1 = 981.46 cm/sec2

For smoth particles

= 180 = 1.8

L = length = 2.439 m = 243.9 cm

Putting values in above eq. givesP = 210.83 gm/cm 2

And 1033.074 g/cm 2 = 1 atm

So P = 0.204 atm


77/124

Appendix-A

77

Calculations of Heat Transfer Co-efficients

Shell Side

For water a simplified equation for heat transfer co-efficient

0.2

0.8 b

oD

V0.011t1150h

t b = average water temperature;oF

=2

4525 = 35 o C = 95 o F

D = Diameter, in

Equivalent diameter = perimeter heated

areaflow4

Flow area = 2ott2s D ND4

Ds = 104.72 in

N t = 709

Dot = 2.5 in

Flow area = 5130 in 2

Heated perimeter = N t Dot

= 709 2.5 3.14

= 5565 in.

De =5565

51304 = 3.68 in

Now to calculate V = velocity of water in fps

Mass velocity = G = W/a s

W = flow rate of water = 2009.9 Kg/hr

= 44237 lb/hrs

flow area = as = 5130 in 2 = 35.625 ft 2

G = 44257/35.625 = 1242 lb/hr. ft2


78/124

Appendix-A

78

Also G = V

= density of water = 62.5 lb/ft 3

so velocity V = G/ = 1242/62.5

= 19.87 ft/hr

= 0.00552 fps

so h o

2.08.0

3.68

00552.0850.0111150

= 3.691 Btu/ hr. ft 2 oF

Tube Side

An equation proposed by LEVA to find heat transfer co-efficient inside

the tubes filled with catalyst particles.

ddp

e

dpG3.5

k

h 4.60.7

p

d

G = 420 lb/hr. ft 2

= 0.0829 lb/hr. ft

k = 0.0315 Btu/hr. ft oF

D p = dia of particle = 0.0041 ft

D = dia of tube = 0.1836 ft

Putting values in above eq.

0.7 p

0.08294200.0041

3.50.0315

1836.0h

5.828 hp = 3.5 (8.36) (0.9023)

hp = 4.53 Btu/hr. ft 2 oF

hio = 4.53DODI

4.53 =2.5

204.24.53 = Btu/hr. ft 2

Dirt FactorAssume dirt factor = 0.003


79/124

Appendix-A

79

Over all H.T. Coefficient

DoioD

R h1

h1

U1

003.03.691

141

U1

D

= 0.5273

UD = 1.896 Btu hr. ft2

Area required for Heat Transfer

Q = 1519488 Btu/hr

LMTD = 515o

C = 959o

FUD = 1.896 Btu/hr. ft

2

A =9591.896

1519488LMTDU

D = 835 ft 2 = 77.67 m 2

Area Available for Heat Transfer

Length of tube = L t = 2.439 m

Outer Dia of tube = D ot = 0.0635 mSurface area of one tube = tot LD

= 3.14 0.0635 2.439

= 0.486 m 2

Total surface area available = 709 0.486

= 344.9 in 2

so sufficient area is available for heat transfer.A-2) DESIGN CALCULATIONS OF ABSORBER-A1

H2O = 4064 Kg/hrCH 3CHO = 20.43 Kg/hrC2H5OH = 17 Kg/hr

CH 3CHO = 20.64 Kg/hrC2H5OH = 17.1 Kg/hrO2 = 484.96 Kg/hr

N2 = 2090.82 Kg/hr


80/124


81/124

Appendix-A

81

We want to scrub 412.59Kg acetaldehyde and 431.48kg/hr ethyl alcohol.

This duty is done by two absorbers .In fist absorber 95% of acetaldehyde is

absorbed and about 99.96% of alcohol is absorbed.

The solvent used for this purpose is water.

Compositions of Components in Gas Mixture at Enterance

Components Kg Kg mol Mol %

CH 3CHO 412.8 9.38 8.27

C2H5OH 431.58 9.38 8.27

H2O 85.35 4.78 4.18

O2 484.96 15.15 13.37

N2 2090.82 74.67 65.89

Total G = 3505 Gm = 113.32

Composition of Components in Liquid Components Kg Kg mol Mol %

H2O 4064 225.7 0.996

CH 3CHO 20.43 0.464 0.002

C2H5OH 17 0.37 0.0016

Total L = 4101.43 Lm = 226.534

Temperature of entering gas = 30 oC

Pressure = 1.1 atm

Average molecular weight of Gas = 3505/113.32

= 30.93 Kg/Kg-mol

G = PM/RT (where, R = 0.08205)


82/124

Appendix-A

82

G =30308205.093.301.1

= 1.36 g/L = 1.36 Kg/m 3

water = L = 997 Kg/m3 (at 25 oC)

Approximation of column dia

Approximate column dia from figure

Dia 1 meter = 3.28 ft

When the dia of column less than 3ft or near about 3ft use packed columns.

Because it is always economical to use packed column when the dia is about 1

m or less 1 m.

Selection of Packing

We have selected ceramic Intalox saddle.

Intalox saddle and pall rings are most popular choices. We have selected

ceramic intalox saddle because they are most efficient. We have selected theceramic material of packing because in our system oxygen and water are present

and they can cause corrosion and ceramic material will prevent corrosion.

Size of the Packing

Now we will find the maximum size of intalox saddle which would be used for

this particular dia of the column.

Packing size =15

1115

D1 = 0.0666 m = 66 mm

Although the efficiency of higher for small packings, it is generally

accept that it is economical to use these small sizes in an attempt to improve the

performance of a column. It is preferable to use the largest recommended size of

a particular type of packing and to increase the packed height to compensate for

small loss of efficiency.


83/124

Appendix-A

83

Flooding Velocity

liquidG

GL

where,

L = 4101.43 Kg/hr

G = 3505 Kg/hr

L = 997 Kg/m3

. G = 1.36 Kg/m3

Let superficial velocity should be 60% of flooding velocity.

Superficial velocity = 0.6 2.36 = 1.416 m/sec

Note: This velocity is near the loading velocity.

Mass velocity of gas = density velocity

= 6932.73 Kg/hr-m 2

As flow rate of gas = 3505 Kg/hr

Mass velocity flow rate of gas/cross sectional area

A = 2D4

= 3505/6932.74 = 0.5055-m 2

D2 = 0.64

D = 0.80 m

This the actual diameter of column.

Number of Transfer Units (N OG )

y1 = mole fraction of acetaldehyde in entering gas = 0.0828

y2 = mole fraction of acetaldehyde in exit gas = 0.0052

As gas is dilute mixture of acetaldehyde.

So by Fig-25 of Appendix-B.

y1/y

2 = 15.945


84/124

Appendix-A

84

LmGm

m = ?

where m = slop of equilibrium curve and it is straight line because system is

dilute one.Let m = 1.6

LmGm

m =226.24

3.1131.6 = 0.8

where

Lm = optimum liquid flow rate. It has been optimized before the liquid enters

the 2 nd column.

Optimum value for termLmGm

m will lie between 0.7 to 0.8

So by using Fig.25

NOG = 7

Height of Packing(Z)

For ceramic intalox saddle:

HOG = 315.0

316.0

Lm

Gm1.14

Where

Gm = gas flow rate, lb moles/hr. ft2

Lm = liquid flow rate, lbmol/hr.ft2

We have,

Gm = 113.3 Kgmol/hr

Since cross-section area = A = 0.502 m 2

Gm = 113.3/0.502 Kg mol/m2hr = 225.69 Kgmol/m 2hr

Similarly,

Lm = 226.24/0.502 Kgmol/m2hr = 450.67 Kgmol/hr. m 2

Gm = 225.69 Kgmol/hr.m2


85/124

Appendix-A

85

= 46.15 lbmol/hrft 2

Similarly,

Lm = 92.15 lbmol/hr.ft2

HOG = 315.0

316.0

92.15

46.151.14

HOG = 0.92 ft

Where

HOG = height of a transfer unit

Z = H OG NOG

Z = 0.92 7 = 6.44 ft

Z = 1.96 m

Where Z is the height of packing.

Allow 2.0 ft for good liquid distribution through the packing from top.

Allowance for supports

= (2 ft) (2 sections) = 4 ft

Total packing height required = Z = 6.44 + 2 + 4 = 12.44 ft

use 15 ft of packing.

Degree of wetting

LP = packingof areSpecific

rateLiquid

Liquid rate = 2.27 m 3/m2sec

And

Specific area of packing = 118 m 2/m3

LP = 2.27 10-3/118 = 1.92 10 -5 m3/m.sec


86/124


87/124

Appendix-A

87

A-3) DESIGN CALCULATIONS OF DISTILLATION

COLUMN (DC-1)

FEEDCH 3CHOH = 3.66 %C2H5OH = 3.66 %H2O = 92.69 %

TOP PRODUCTCH 3CHOH = 98.2 %C2H5OH = 0.75 %H2O = 0.97 %


88/124

Appendix-A

88

Process Design

Temperature of feed = 91 o C

Temperature of top product = 20 o C

Temperature of bottom product = 99 o C

P = 1 atm

Minimum Reflux Ratio

Component FeedF X f Top

D X d BottomW X w

RelativeVolatility

CH3CHO

C2H5OH

H2O

0.0366

0.0366

0.9269

0.982

0.0075

0.0097

0

0.0377

0.962

10.87

2.27

1.00

Light key component = CH 3CH 2OH = B

Heavy key component = H 2O = C


89/124

Appendix-A

89

Lighter than light key component = CH 3CHO = A

Using underwood equation

q1

C

fCC

B

fBB

A

fAA x x x

As feed is at its bubble point so q = 1

Bt trial = 3.5

Using eq. of min. reflux ratio,

1R

m

C

fCC

B

fBB

A

fAA x x x

putting all values R m = 2.62 No. of plates at total reflux

Using Fenskes equation

aveBC

sXX

XX

m log

dlog1 N B

C

C

B

log2.27log

N 0.03770.962

0.0097

0.0075

m

Relative Volatility Method for Plate to Plate Calculations

Above feed plate:

Ln = RD = 3.5 9.5412 = 33.3942 Kg mol/hr

Vn = (R+1) D = 4.5 9.5412 = 429354 Kgmol/hr

Below feed plate:

Lm = L n + F = 33.3942 + 256.4595 = 289.8537 Kgmol/hr

Vm = L m W = 289.8537 246.9015 = 42.9522 Kgmol/hr

Operating lines above feed point:


90/124

Appendix-A

90

dn

1nn

nm V

DX

VL

y x

yn CH 3CHO = 0.7778 X n+1 + 0.2806

yn C 2H5OH = 0.7778 X n+1 + 0.0021

yn H 2O = 0.7778 X n+1 + 0.0028

Operating lines below feed plate:

wm

1mm

mm XV

WX

VL

y

ym CH 3CHO = 6.748 X m+1

ym C2H 5OH = 6.748 X m+1 0.2167

ym H2O = 6.748 X m+1 5.5269

Starting from top plate:

Component

Xd =

yt Y t/

X t =

t

t

t y

y

X

Y1 Y1/

X1 =

y

y

X 1

1

1

CH 3CHO

C2H5OH

H2O

10.8

7

2.27

1.00

0.782

0.007

5

0.009

7

0.90

3

0.01

7

0.00

9

0.8739

0.032

0.0939

0.96

0

0.02

7

0.07

5

0.20

0.02

7

0.17

0

0.0794

0.0680

0.4282

Y2 X 2 X3 Below feed

plate Y8

0.342

0.055

0.336

------

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Production of Acetaldehyde

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