Abstract— This paper presents a conceptual design of the

combined processes of biodiesel production, glycerol steam

reforming, and hydrotreating of free fatty acid in order to utilize the

large amount of glycerol produced from biodiesel production to

produce alternative fuels. Hydrogen is obtained from glycerol steam

reforming, yielding high hydrogen moles produced per mole of

glycerol. Hydrogen is used as a reactant of hydrotreating of free

fatty acid to produce petrodiesel-like fuel. Furthermore, free fatty

acid as unsuitable feedstock in a biodiesel production is a very

favorable reactant for hydrotreating process as it demands lower

hydrogen consumption compared with vegetable oil.

Keywords—: Combined processes, Biodiesel, Glycerol steam

reforming, Hydrotreating of waste cooking oil.

I. INTRODUCTION

OWADAYS, the increasing of energy consumption in the

entire world is inversely proportional to the availability

of fossil energy as a base worldwide energy sources.

Thus, many researches are finding the alternative energy

which could be directly used in machines for transportation

sector. Biodiesel or free fatty acid methyl ester (FAME),

which is known as an alternative renewable and biodegradable

fuel, has been attracted because it can be directly used or

blended with petroleum diesel in compression–ignition

engines. However, production of 10 tons of biodiesel also

produces 1 ton of glycerol as a byproduct. Glycerol might be

an environmental concern because of a limit of glycerol

applications. Recently, hydrogen production using glycerol as

main reactant has been attractive for many reasons such as it

provides high hydrogen content within the economic aspect.

Hydrotreating oil is known as green diesel or renewable diesel

or second generation diesel or petrodiesel-like fuels which can

be obtained from vegetable oil or free fatty acids as biodiesel

raw materials and hydrogen. It requires a severe condition

(high temperature and high pressure) to produce a green

diesel. Thus, the combination of biodiesel, glycerol reforming,

and green diesel production processes could be a promising

choice for renewable fuel production.

Bamrung Sungnoen is with the Chulalongkorn University, Bangkok,

10330, Thailand (e-mail: aego8smith@gmail.com).

Kanokwan Ngaosuwan is with the Rajamangala University of Technology

Krungthep, Bangkok, 10120, Thailand (e-mail: kanokwanng@gmail.com).

Suttichai Assabumrungrat is with the Chulalongkorn University,

Bangkok, 10330, Thailand (corresponding author’s phone: +66022186868;

e-mail: suttichai.a@chula.ac.th).

II. THERMODYNAMIC MODELLS

The proposed processes were simulated using Aspen Plus

Program. Suitable thermodynamic models have been applied

for biodiesel, glycerol steam reforming, and green diesel as

follows: Non-Random Two Liquid model (NRTL), Soave–

Redlich–Kwong (PSRK), and Peng-Robinson equation of

state (PENG-ROB). Furthermore, UNIFAC was used for

predicting some binary interaction parameters which were not

available in the simulation databank and the pressure drop in

process for all equipment are neglected.

Fig 1. The biodiesel production process

Fig 2. The hydrogen production process via glycerol steam

reforming.

Fig 3. The green diesel production process

Combined Biodiesel, Glycerol Reforming and

Green Diesel Production Processes: Conceptual

Process Design

Bamrung Sungnoen, Kanokwan Ngaosuwan, and Suttichai Assabumrungrat

N

International Journal of Mining, Metallurgy & Mechanical Engineering (IJMMME) Volume 3, Issue 3 (2015) ISSN 2320–4060 (Online)

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III. PROCESS DESIGN AND SIMULATION

The proposed process combines the three main process

sections including biodiesel using soybean oil, glycerol steam

reforming, and hydrotreating of free fatty acid (using steric

acid as a free fatty acid model). In Fig. 1, the proposed

biodiesel production section, large amounts of 10 tonnes/hr of

mixture (soybean and methanol-sodium solution) are fed to

transesterification reactor (R- TRAN). The excessive

methanol is recycled from the top of the first distillation

column (DC-BD) to reuse while the bottom products are sent

to extraction column to separate fatty acid methyl esters

(FAMEs) from other products. Then, FAMEs are fed to the

second distillation column (DC-FAME) in order to achieve

>99 wt% of biodiesel purity. The glycerol from extraction is

neutralized by adding phosphoric acid (H3PO4) in the

neutralization reactor (R-NEUT). After salt removal step

(FILTER), the mixture of glycerol-methanol-water is used as

a raw material in glycerol steam reforming section.

In Fig. 2, the glycerol steam reforming section, the

mixture of glycerol-methanol-water from biodiesel section is

preheated to the operating condition of reformer

(REFORMER). The pressure swing absorption off-gas stream

is burnt in a furnace-combustor to supply heat in the process.

The product gases are also cooled to the operating condition

of high and low water-gas shift reactor (HWGS and LWGS).

The off-gas mainly consisting of H2, CO2 and CO from the

first phase separation unit (SEP1) flows to PSA where the

mean concentration of carbon dioxide can be less than 10

ppm. The PSA is the most mature application for CO removal

from the product gas mixture. Moreover, PSA is able to

remove other product gases to achieve high purity of H2 in

the stream outlet from PSA. The hydrogen utilization is

divided into three major streams: (1) the hydrogen-tail gas

mixture is fed to supply heat for furnace; (2) the high purity

of hydrogen is prepared for the next hydrotreating of free

fatty acid section; (3) the high purity of hydrogen is stored for

other applications, but this stream is not included in this

consideration. Thus, the overall hydrogen production is

served for green diesel production.

In the last section (Fig. 3), the multiple reactions such as

hydrodeoxygenation and decarbonylation reaction can be

occurred simultaneously over catalyst bed in hydrotreating

reactor (R-HDO). The main hydrocarbon products of HDO of

steric acid consists of n-pentadecane, n-hexadecane, n-

heptadecane, n-octadecane, and l-octadecanol. The gaseous

portion of the stream (FLUE-GAS) comprising a residue of

hydrogen, carbon monoxide, methane, ethane and propane

are removed from a stream by the second phase separator

(SEP2) and sent to mix with hydrogen-tail gases as a furnace

fuel gas (TGIN). The crude green diesel mainly consisting of

liquid hydrocarbon can be obtained in the second phase

separator. These liquid mixtures are prepared for the other

processes such as isomerization which it is not a main

consideration in this work. The detailed specification such as

equipment and operating condition using in this simulation

are summarized in Table I.

In additional, all local proposed processes were validated

as following: (1) biodiesel process produced the methyl ester

yield corresponding to simulation result of Noureddini, and

Zhu work [1]; (2) H2 production from glycerol reforming

process was in agreement with the simulation result of Hajjaji

et al. work [2]; and (3) stearic acid conversion was found to

be 14.37% error as comparing with the experimental result of

Kumar et al work [3] due to its complicated reaction pathway.

TABLE I

UNITS SPECFICATIONS FOR THE CONCEPTUAL DESIGN OF THE COMBINED PROCESSES

Code name Equipment Design specification

MIX1-MIX4 Mixers Pressure drop: 0.0 atm

SPLT1 Splitter Pressure drop: 0.0 atm

Split fraction: variable parameter (zero value for no H2

storage)

P1-P4 Pumps Discharge pressure: 1.1 atm

Pump efficiencies: 0.75

P5 Pumps Discharge pressure: 29.6 atm

Pump efficiencies: 0.75

P6 Pumps Discharge pressure: 14.31 atm

Pump efficiencies: 0.75

HX1-HX2 Heaters Pressure drop: 0.0 atm

Outlet temperature: 60˚C

HX3 Heaters Pressure drop: 0.0 atm

Temperature: 950 ˚C

TABLE II

UNITS SPECIFICATIONS FOR THE CONCEPTUAL DESIGN OF THE COMBINED PROCESSES (CONTINUE).

Code name Equipment Design specification

HX4-HX5 Heaters Pressure drop: 0.0 atm

Outlet temperature: 289.85˚C

C1 Coolers Pressure drop: 0.0 atm

Outlet temperature: 60˚C

C2 Coolers Pressure drop: 0.0 atm

Outlet temperature: 350˚C

C3 Coolers Pressure drop: 0.0 atm

Outlet temperature: 200˚C

C4-C5 Coolers Pressure drop: 0.0 atm

Outlet temperature: 35˚C

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V1-V2 Adiabatic valves Discharge pressure: 1.1 atm

V3 Adiabatic valves Discharge pressure: 14.31 atm

FAN1 Fans Discharge pressure: 1.1 atm

Isentropic efficiency: 0.72

R-TRAN Transesterification reactor Adiabatic reactor (heat duty = 0)

Pressure drop: 0 atm

DC-BD Distillation column Number of stages: 7 stages

Column pressure: 0.98 atm

Distillate rate: 1130 kg/hr

Mass reflux ratio: 2

BD-WASH Liquid-liquid extraction column Number of stages: 6 stages

Column pressure: 0.98 atm

DC-FAME Distillation column Number of stages: 7 stages

Column pressure: 0.098 atm

Distillate rate: 800 kg/hr

Mass reflux ratio: 2

Biodiesel capacity: 9,244.10 kg/hr

R-NUET Neutralization reactor Isothermal operation: 50˚C

Pressure: 1 atm

FILTER Filter Na3PO4 removal (split fraction = 1)

Glycerol capacity: 942.28 kg/hr

REFORMER Glycerol reforming reactor 3 8 3 2 2 2C H O +3H O 3CO +7H

3 2 2 2CH OH+H O CO +3H

Operating temperature = 950˚C

Pressure drop: 0.0 atm

HWGS High water gas shift reactor 2 2 2CO+H O CO +H

Operating temperature = 350˚C

Pressure drop: 0.0 atm

LWGS Low water gas shift reactor 2 2 2CO+H O CO +H

Operating temperature = 200˚C

Pressure drop: 0.0 atm

Hydrogen capacity: 75.55 kg/hr

SEP1 Separators (Two-outlet flash) Heat duty: 0

Pressure drop: 0.0 atm

PSA Pressure swing absorption unit 80% of H2 from the other gases

Pressure drop: 0.0 atm

FURNACE Furnace burner Fuel gas combustor supply heat duty Operating temperature:

1000˚C

Operating pressure: 1 atm

R-HDO Hydrodeoxygenation reactor Operating temperature: 289.85˚C

Pressure drop: 0.0 atm

SEP2 Separators (Three-outlet flash) Heat duty: 0

Pressure drop: 0.0 atm

Green diesel capacity: 4,048.93 kg/hr

IV. OPTIMIZATION STRATEGY

Table 2 shows the comparison of main number of

individual units required in each process. In the conventional

biodiesel production process, glycerol will be a problem

because it is used a small amount in industrial such as

cosmetics, food and pharmaceutical applications. The

purification of glycerol remains expensive. The glycerol

containing unreacted alkali catalyst and soap must be

neutralized with acid. Then, the water and alcohol were

removed in order to obtain 50-80% of crude glycerol.

However, 99% or higher purity is required for feeding in

pharmaceutical and cosmetics. Thus, this glycerol purification

generates a huge of cost in the conventional biodiesel. In

contrast, the proposed process is unnecessary to require the

high purity of glycerol. The glycerol-methanol-water mixture

can be directly used as a feed in the glycerol reforming

section. Therefore, the distillation column for glycerol

purification step can be reasonably neglected from the

combined processes as presented in Table II.

The conventional reforming process suffers in energy

consumption because this process requires a high energy for

reforming reaction although the heat integration is applied. In

this work, a furnace is installed as heat provider where the fuel

gases are oxidized with air as combustion reaction. The fuel

gases comprise with two major sources: (1) tail gas is obtained

from the glycerol steam reforming and (2) residual hydrogen,

carbon monoxide, methane, ethane and propane come from the

hydrotreating process.

Using fuel gas from the hydrotreating process as an energy

source in the furnace combustor for the combined processes

can reduce the total heat energy requirement of 2.45 MW.

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TABLE III

THE COMPARISON OF MAIN NUMBER OF INDIVIDUAL UNITS REQUIRED IN EACH PROCESS

Individual units The conventional local process The propose process

Biodiesel Steam reforming Hydrotreating Combination process (This work)

Reactors 2 3 1 6

Distillations 3 0 0 2

Heaters 3 1 2 6

Coolers 1 3 1 5

Flash 0 1 1 2

Centrifuges 4 1 1 6

Furnace 0 0 0 1

Total 28 28

Total heat energy requirement (MW) 10.72 8.27

Total cooling energy requirement (MW) 5.11 5.11

Total work requirement (MW) 6.13 ×10-03 6.13×10-03

V. CONCLUSION

In this work, we proposed a novel process by combination

of three processes of biodiesel production, hydrogen

production via glycerol reforming and hydrotreating. The large

amount of crude glycerol is fed to reforming process in order

to convert to hydrogen. All hydrogen was fed to hydrotreating

process. Free fatty acids and hydrogen as main feedstocks of

green diesel are fed to the hydrotreating process to produce

green diesel. The nature of reforming and hydrotreating is

highly endothermic so they are favorable at high temperatures.

Therefore, both processes consume high energy to drive

processes. In the future work, the heat integration can be also

applied to increase the efficiency of overall energy

consumption. The valuable final products achieved from this

novel process are FAME, hydrogen, and petrodiesel-like fuels

(green diesel) which offer a different fuel grade and high

purity of hydrogen.

ACKNOWLEDGMENT

The authors would like to acknowledge the supports from

the Thailand Research Fund.

REFERENCES

[1] H. Noureddini, and D. Zhu, ―Kinetics of Transesterification of Soybean

Oil,‖ J. Am. Chem. Soc., vol. 74, pp. 1457-1463, 1997.

[2] N. Hajjaji, A. Chahbani, Z. Khila, and M.-N. Pons, ―A comprehensive

energy-exergy-based assessment and parametric study of a hydrogen

production process using steam glycerol reforming,‖ Energy, vol. 64,

pp. 473–483, Jan. 2014.

[3] P. Kumar, S. R. Yenumala, S. K. Maity, and D. Shee, ―Kinetics of

hydrodeoxygenation of stearic acid using supported nickel catalysts:

Effects of supports,‖ Appl Catal A: General, vol. 471, pp. 28-38, Feb.

2014.

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