Design of Plant for the Production of 20,000 tons of Acetaldehyde per year by the Direct Oxidation of Ethylene.
Achira U. Anointing., Taiwo F. Ademiluyi, Akpa J. Gunorubon, and Kenneth K. Dagde
Department of chemical/Petro-Chemical Engineering, Rivers State University, Nkpolu, Port Harcourt, River State.
Email: [email protected] Abstract
Acetaldehyde is a volatile, flammable and colorless liquid, miscible in water, alcohol, ether, benzene and other common organic solvent, with a pungent fruity odor, that is widely used for the production of other chemicals which can be produced by many processes, such as partial oxidation of ethane, hydration of acetylene, oxidation of ethylene, oxidative dehydrogenation of ethanol, and dehydrogenation of ethanol. This work focuses on the design, model and simulation of a plant producing 20,000 tonnes of Acetaldehyde annually through direct oxidation of ethylene using Aspen Hysys.
KEYWORDS: Acetaldehyde, Ethylene, Oxygen, Design, Aspen HYSYS, Costing.
Cite This Paper: Achira U. Anointing., Ademiluyi, T. F., Gunorubon A.J. & Dagde, K. K. (2021). Design of Plant for the Production of 20,000 tons of Acetaldehyde per year by the Direct Oxidation of Ethylene. Journal of Newviews in Engineering and Technology. 2(3), 66 – 74.
1. INTRODUCTION
Acetaldehyde is a valuable chemical that is widely used for the production of other chemicals, such as acetic acid, acetic anhydride, ethyl acetate, n-butanol, pyridine, and vinyl acetate. It is an organic chemical compound with the formula CH3 CHO, sometimes abbreviated by chemists as MeCHO (Me = methyl). It is a mobile, low boiling, highly flammable, colourless liquid with a pungent, fruity odor. However, due to its high chemical reactivity, it is primarily used as a chemical intermediate principally for the production of acetic acid, pyridine and pyridine bases, peracetic acid, pentaerythritol, butylene glycol, and chloral (chlorinated acetaldehyde), 2-ethylhexanol, alkyl amines, acetic anhydride and other chemicals.
Acetaldehyde can be produced by many processes, such as partial oxidation of ethane, hydration of acetylene, oxidation of ethylene, oxidative dehydrogenation of ethanol, and dehydrogenation of ethanol. The oxidation of ethylene, which is also called the Wacker-Hoechst process, refers to the formation of polymerization and condensation products of acetaldehyde. This involves oxidation of ethylene using a homogeneous palladium/copper system, Smaller quantities can be prepared by the partial oxidation of ethanol in an exothermic reaction. It is one of the oldest routes for the industrial preparation of acetaldehyde. Though the oxidative dehydrogenation of ethanol is an alternative route, which is quickly gaining widespread interest, but the use of air for the reaction affects the production cost of this process. As compared with the above-mentioned synthesis processes, the production of acetaldehyde via the ethanol dehydrogenation route appears highly attractive due to its cleaner technology.
Acetaldehyde is a volatile and flammable liquid that is miscible with water, alcohol, ether, benzene, gasoline, and other common organic solvents. The first commercial application was the production of acetone via acetic acid. Acetaldehyde is an intermediate in the metabolism of plant and animal organisms, in which it can be detected in small amounts, larger amounts of acetaldehyde cab interfere with biological processes. As an
intermediate in alcoholic fermentation processes it is present in small amounts in all alcoholic beverages such as beer, wine and spirit. Acetaldehyde has also been detected in plant juices and essential oils, roasted coffee, and tobacco smoke.
In recent years, increasing amounts of acetaldehyde have been produced by the air oxidation of ethyl alcohol and now nearly equal the production from acetylene by hydration. Both processes result in a highly diluted gas reaction mixture involving a difficult recovery of acetaldehyde, in one instance from the nitrogen of the air, unreacted alcohol, and other oxidation products and in the other, from large amounts of unreacted acetylene. In contrast, the dehydrogenation of ethyl alcohol would simplify the problem of recovery, since only acetaldehyde and hydrogen are obtained as the products from the reaction (Church & Joshi, 1951). Direct dehydrogenation of ethanol to acetaldehyde is an economical and environmentally friendly alternative to conventional commercial processes (DeWilde et al., 2014; Freitas et al., 2014; Sato et al., 2012).
Figure 1: Molecular structure of acetaldehyde PROPERTIES OF ACETALDEHYDE
Table 1: Acetaldehyde Properties
Property Value/ Remarks
Chemical formula Appearance
CH3CHO
Colourless, volatile Liquid
@ 25oC Smell
Molecular Weight
Pungent, sharp, fruity odour
44.053 g/mol Melting Point -123 OC Boiling Point 20.2 OC
Flash Point 39.00 °C; −38.20 °F;
234.15 K
Ignition Point 175.00 °C; 347.00 °F;
448.15 K Density
Solubility Water solubility
Explosive limit
0.784 g/mol
Very soluble in water 4.0–60%
Application of Acetaldehyde
Acetaldehyde is used in the manufacturing of various chemicals such as acetic acid, pyridine, peracetic acid, pentaerythritol, 1,3-butylene glycol, vinyl acetate resins, synthetic pyridine derivatives, perfumes, flavours, and chloral.
It is also used in the silvering of mirrors, leather tanning, and in fuel compositions, preservatives, paper processing,
glues, cosmetics, dyes, plastics, rubber, and as a flavouring agent.
Production Process
Generally, all processes based on acetylene, ethylene, and ethanol are more selective than the oxidation of saturated hydrocarbons.
This is because, in the latter case, other oxidation products are formed in addition to acetaldehyde. Because of the great expense of separating the product mixture, such processes are economical only in large units and when all main and secondary products
obtained in the process are utilized.
2. Materials and Methods 2.1. Materials
The materials used for this work includes Ethylene, Oxygen, Aspen HYSYS, separator, compressor, conversion reactor, Fluid Bed Reactor/PFR reboiler, condenser, mixer, storage tanks, expander, and distillation column.
2.2 Methods
The design of each units in the plant would use the materials and energy balance principle as stated:
Material Balance (Rate of accumulation
of material
wihtin the RDC ) = (Rate of input of material
into RDC ) − (Rate of output of material from RDC ) ±
( Rate of
deplection/generation of material
by chemical reactor in RDC ) (1)
Energy Balance
(Rate of accumulation of energy wihtin the RDC )
= (Rate of input of energy
into the RDC) − (Rate of output of energy out of the RDC)
± ( Rate of generation or deplection of energy
by chemical reactor within the RDC)
Figure 2: Process Flow Diagram for Acetaldehyde production 2.2.1. Development of Design Equation for the Process Plant Equipment
Design Assumptions:
i) The process is assumed to operate at steady state condition;
ii) The flow condition in the reactor is assumed as plug flow;
iii) Concentration of reactants vary along the length of the reactor from point to point;
iv) The composition of the reacting mixture is uniform;
v) Dispersion effects are neglected in the direction of flow;
vi) Balance can be made about the entire volume of reactor;
vii) The composition of the exist stream is the same as that within the reactor.
viii)The process is assumed to be isothermal;
ix) Ideal behaviour in separators;
x) Uniform mixing in mixer;
xi) No reaction occurs in the mixer and separator;
xii) No accumulation in the mixer;
xiii)No pressure drops in reactors and columns;
xiv)Thermal effect in the pump is negligible.
Process Description:
Figure 2 shows Acetaldehyde production plant, the raw materials for the process plant are ethanol and oxygen. Ethanol stream at 400
oC and 411.6kPa is dehydrated in a Conversion Reactor operating at 110oC and $11.6kPa. the Bottom Reactor Effluent containing water is stored in a storage tank. The pressure of the top Reactor effluent containing more of Ethylene is reduced to 101.3kPa and then cooled to -46.67oC for easy separation of ethylene and water in a separator. The crude ethylene is mixed with oxygen stream at 25oC and 101.3kPa in a mixer operating at -23.78oC and 101.3kPa before charged to a Plug flow reactor with pressure drop 0.0kPa and -23.78oC. The reactor effluent containing Acetaldehyde unreacted Ethylene and Oxygen was sent to an atmospheric distillation column that separates the mixture into unreacted ethylene, oxygen and acetaldehyde as distillate which was separated in a separator, the top product of the separator (containing oxygen and ethylene) was recycled to feed mixer and Acetaldehyde as bottom product (C2H4O) was mixed with the bottom product of the distillation column containing acetaldehyde.
Figure 2: Process Flow Diagram for Acetaldehyde production Plant
3. Results and Discussion
Below Figures and Tables shows design specification of the entire process (composition of material components balance, energy balance).
3.1. EQUIPEMENT DESIGN SPECIFICATIONS
Table 1: Calculated Design Parameters Around Reactor
Parameters Values
Molar flowrate of Acetaldehyde (FE)
57.3269 kmol/hr Molar flowrate of
Ethylene (FB)
36.5044 kmol/hr Molar flowrate of
oxygen (FD)
20.8225 kmol/hr Molar flowrate of
Ethanol (FA)
59.9557 kmol/hr
Parameters Values
Molar flowrate of Acetaldehyde (FE)
57.3269 kmol/hr Molar flowrate of Ethylene
(FB)
36.5044 kmol/hr Molar flowrate of oxygen
(FD)
20.8225 kmol/hr Molar flowrate of Ethanol
(FA)
59.9557 kmol/hr
Table 2: Conversion Reactor Specifications
Table 3: Expander specification EXPANDER Compressor Type Turboexpander
Function To decrease pressure of the separator product
Material Stream Flow rate (kg/hr.)
Inlet 2,136
Outlet 2,136
Operating condition Pressure Drop Temperature Drop Duty (kJ/hr) Power
Produced (kW) Nozzle
Diameter (m)
310.3 kPa 110oC 2.667e0.005 74.09 5.0e-0.002
Material Isentropic Efficiency Power source Purchase cost Total direct cost
Carbon steel 75%
Electricity 5,373,200USD 8,415,700USD
Table 4: cooler Specification
Table 5: Separator 1 specification
COLUMN Type two phase separator Function To Purify Ethylene
Operating Conditions
Pressure 101.3kpa Temperature 25oC Material Stream
Flow rate (Kg/hr) Composition C2H4
H2O O2
C2H5OH C2H4O
Feed Str 2,136 0.6411 0.3589 0.0000 0.0000 0.0000
Top Str 1,6050 0.9679 0.0321 0.0000 0.0000 0.0000
Bottom str 531.20 0.0000 1.0000 0.0000 0.0000 0.0000 Design Data
Volume Diameter Height Thickness Material Purchase Cost Total Direct Cost
247.5m3 5.945m 8.917m 6.35mm Stainless Steel 16, 500USD 134,200USD
Table 7: Reactor 2 specification REACTOR II
Reactor Type Plug flow Reactor Function To Produce Acetaldehyde Operating Conditions
Pressure 101.3kpa Temperature 25oC Reaction phase Vapour
REACTOR I
Reactor Type Conversion Reactor
Function: To Produce Ethylene
Operating Conditions
Pressure 411 kpa Temperature 400oC Reaction phase Vapour Material
Stream Flow rate (Kg/Hr) Composition C2H4
H2O O2
C2H5OH C2H4O
Feed Stream
2,580
0.0000 0.0000 0.0000 1.0000 0.0000
Top Product
2,136
0.6411 0.3589 0.0000 0.0000 0.0000
Down Product
4,44.2
0.000 1.000 0.000 0.000 0.000 Design Data
Volume Diameter Height Space Time Space velocity Heat Load Thickness Material Material Purchase Cost Total Direct Cost
16.3 m3 1.73 m 6.92 m 4.65 hr 0.22 hr-1 132,260. 3647 kJ/m3
6..350 mm 1 Carbon Steel
34,600 USD 269,500 USD
COOLER Cooler Type Cooler
Function To reduce temperature Utility Refrigerant
Operating Conditions Inlet Outlet
Pressure 101.3kpa 101.3KPa
Temperature 71.67oC 25oC
Material Stream
Flowrate (Kg/Hr) Composition C2H4
H2O O2
C2H5OH C2H4O Purchase cost Equipment cost
inlet 2,136
0.6411 0.3589 0.0000 0.0000 0.0000
outlet 2,136
0.6411 0.3589 0.0000 0.0000 0.0000
Material Stream Flow rate (Kg/hr) Composition C2H4
H2O C2H5OH O2
C2H4O
Feed Str 2,560
0.0702 0.0000 0.0000 0.9076 0.0199
Vent str 2,560
0.0004 0.0024 0.0000 0.9043 0.0930 Design Data
Volume Diameter Length Space Time Space velocity Heat Load Thickness Void fraction Number of Tubes Material
Purchase Cost Total Direct Cost
6.64m3 1.28m 5.12m 7.64hr 0.13 hr-1
-352,076.2433 kJ/m3 5mm
1.00 1
Stainless Steel 42,600USD 202,900USD
Table 6: mixer 1 specifications MIXER I MIXER Type three Stream mixer
Function To mix Oxygen, Ethylene and Recycle streams
Operating Condtxn Inlet Oxygen Recycle Pressure(kPa) 101.3 101.3 405.3 Temperature(oC) 71.67 25 -32
Mixer out 101.3 -23.78oC Material Stream
Flow rate (Kg/hr) Composition C2H4
H2O C2H5OH O2
C2H4O
Ethylene 1,605 0.9678 0.0321 0.0000 0.0000 0.0000
Oxygen 832.0 0.0000 0.0000 0.0000 1.0000 0.0000
recycle 2,316 0.0000 0.0000 0.0000 0.9774 0.0222
Mixer Out 2,560 0.0702 0.0023 0.0000 0.9076 0.0199
Table 8: Acetaldehyde column specification
ACETALDEHYDE COLUMN Column Type Tray Column
Function To purify Acetaldehyde
Material stream Flow rate (kg/hr) Composition C2H4
H2O C2H5OH O2
C2H4O
Feed 2,560 0.0004 0.0024 0.0000 0.9043 0.0930
Distillate 2,483 0.0004 0.0000 0.0000 0.9265 0.0731
Bottom 770.8 0.0000 0.1000 0.0000 0.0000 0.9000
Operating Conditions Pressure Temperature Reflux ratio Number of stages Feed stage
101.3KPa
Min. -182OC and Max. 22.240C 3.00 kmol/kmol
7 4
Design Parameter DIAMETER HEIGHT OF COLUMN MATERIAL THICKNESS POWER SOURCE PURCHASE COST
TOTALDIRECT COST
1.3447m 3.5m
Stainless steel 3mm
Electricity 65,600 USD 402,800 USD
Table 9: Heater Specification
HEATER Cooler Type Cooler
Function To increase temperature of distillate Utility Steam
Operating Conditions Inlet Outlet Pressure 101.3kpa 405.3KPa Temperature -182.8oC -32oC Material Stream
Flowrate (Kg/Hr) Composition C2H4
H2O C2H5OH O2
C2H4O
HEAT DUTY (kJ/hr)
inlet 2,483 0.0004 0.0000 0.0000 0.9265 0.0731 8.741e+006
outlet 2,483 0.0004 0.0000 0.0000 0.9265 0.0731
Table 10: separator 2 specification
COLUMN Type two phase separator Function To Purify Acetaldehyde in the distillate
Operating Conditions
Pressure 405.3kpa Temperature -32oC Material Stream
Flow rate (Kg/hr) Composition C2H4
H2O C2H5OH O2
C2H4O
Feed 2,483
0.0004 0.0000 0.0000 0.9265 0.0731
Top 2,308
0.0004 0.0000 0.0000 0.9774 0.0222
Bottom 1,745
0.0000 0.0000 0.0000 0.0009 0.9900 Design Data
Volume Diameter Height Thickness Material Purchase Cost Total Direct Cost
247.5m3 5.945m 8.917m 6.35mm Stainless Steel 16, 500USD 134,200USD
Table 5.12: Mixer II Specification MIXER II MIXER Type two Stream mixer
Function To mix Acetaldehyde streams
Operating Conditions Inlet 1 Inlet 2 Mixer out Pressure(kPa) 101.3 405.3 101.3 Temperature (oC) 22.11 -32 -14.82oC
Material Stream Flow rate (Kg/hr) Composition C2H4
H2O C2H5OH O2
C2H4O
Inlet 1 770.8
0.0000 0.1000 0.0000 0.0000 0.9000
Inlet 2 1,745
0.0001 0.0000 0.0000 0.0099 0.990
Mixer out 2,516
0.0000 0.0319 0.0000 0.0068 0.9613
DESIGN SIMULATION (ASPEN HYSYS)
Figure 4. Component specification
Figure 5: PFD for the Process Plant
Figure 6: Ethanol Feed
Figure 7: Oxygen Feed
Figure 8: Balance Around the Conversion Reactor (Reactor I)
Figure 9: Fractional conversion around Reactor I
Figure 10: Balance Around the Expander
Figure 11: Balance Around the Cooler
Figure 12: Balance Around Separator I
Figure 13: Balance Around Mixer I
Figure 14: Fractional conversion around Reactor II
Figure 15: Balance Around the PFR (Reactor II)
Figure 16: Mole Fractions of Components Around the Column
Figure 17: Balance Around the Column
Figure 18: Graphs of Temperature, Pressure and Net Flow against Tray Number
Figure 19: Distillation column Specifications
Figure 20: Balance Around the Heater
Figure 21: Balance Around Mixer II
Figure 22: Balance Around Separator II
Figure 23: Balance on the Recycle Stream
Figure 24: Economic Analysis Summary
4. CONCLUSION
The objectives of designing a plant that produces 20,000 tonnes of acetaldehyde annually using direct Oxidation of Ethylene was achieved. A detailed material balances, energy balances and equipment design of major units was upheld during the design process. The processes involved within the plant operations such as chemical reactions, separation process, mixing and column operation were clearly stated with emphases on the health safety, equipment / risk analysis and the environmental impact were taking into consideration. Adequate control systems were also specified for installation in sensitive units as human errors are liable to bring about deviation in specifications. An elucidative cost and economic analysis of the plant`s total cost of installation was estimated to be about 1,317,100USD (#507,083,500).The nearness of raw materials, marketable areas, availability of labors and some principal factors of plant location and layout for both the
products and by-products were put into consideration and are accessible.
Emphasis was laid on the safety and equipment, risk analysis, system controls and environmental impact of the plant. The motive of designing a chemical processing plant is to maximize profit and minimize cost which was also achieved by running the economic analysis of the plant.
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