Ethanol Production Process Analysis

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ETHANOL production
Line
No. Team Name Seat No.
1 Alaa Refaay Ghareeb 2
2 Aya Hassaneen Madny 6
3 Aya Atef Hussein 8
4 Aya Abdalla Ali 9
5 Ahmed Ismail Ali 19
6 Ahmed Elsayed Abdelsalam 24
7 Aslam Amgd Gaber 94
8 Hassan Farag Mohamed 142
9 Riham Osama Mohamed 167
10 Abdelrahman Ashraf Mosaad 198
11 Mohamed Khames Mohamed 337
12 Mohamed Reda Tablia 339
13 Mohamed Tarek Mohamed 353

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Table of Contents
Table of Contents ......................................................................................................................... 2
Table of Figures ............................................................................................................................ 7
1 INTRODUCTION..................................................................................................................... 11
1.1 Physical properties ......................................................................................................... 11
1.2 Chemical properties........................................................................................................ 12
1.3 Manufacture................................................................................................................... 12
1.4 Uses of Ethanol............................................................................................................... 13
2 CHAPTER 2: FERMENTATION SECTION.................................................................................. 17
2.1 INTRODUCTION............................................................................................................... 17
2.2 Ethanol Fermentation with Yeast................................................................................... 18
2.3 What is a Fermentor?..................................................................................................... 18
2.4 Classification of Fermentation Processes....................................................................... 22
2.5 The Main Fermenter Layout........................................................................................... 24
2.5.1 Nutrient Feed Tanks................................................................................................. 24
2.5.2 Sterile Filters ............................................................................................................ 25
2.5.3 Air Compressors....................................................................................................... 26
2.5.4 Valves....................................................................................................................... 26
2.5.5 Pumps ...................................................................................................................... 27
2.5.6 Cooling Equipment................................................................................................... 27
2.5.7 Environmental Control............................................................................................. 27
2.5.8 General design data................................................................................................. 28
2.6 Fermentation section ..................................................................................................... 28
2.6.1 Process Control........................................................................................................ 30
2.7 Fermentation process..................................................................................................... 31
2.7.1 Fermentors............................................................................................................... 31
2.8 Centrifugation................................................................................................................. 33
2.8.1 Biomass Separation (centrifuges) (F-011, F-012)..................................................... 35
2.8.2 Yeast sterilization Tank (A-011) ............................................................................... 35
2.8.3 Ethanol Purification ................................................................................................. 35
3 CHAPTER 3: DISTILLATION AND DEHYDRATION.................................................................... 36
3.1 INTRODUCTION............................................................................................................... 36
3.2 Distillation terminology .................................................................................................. 37
3.3 Types of Distillation ........................................................................................................ 41
3.3.1 Simple Distillation .................................................................................................... 41
3.3.2 Fractional Distillation............................................................................................... 41
3.3.3 Steam Distillation..................................................................................................... 42
3.3.4 Vacuum Distillation.................................................................................................. 42
3.3.5 Azeotropic Distillation.............................................................................................. 43
3.4 System components ....................................................................................................... 47
3.4.1 Column shells........................................................................................................... 47

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3.4.2 Column internals...................................................................................................... 48
3.4.3 Auxiliary equipment................................................................................................. 53
3.5 The fractionating column design.................................................................................... 56
3.5.1 The fractionating process ........................................................................................ 56
3.5.2 Number of plates required in a distillation column................................................. 58
3.5.3 Factors affecting distillation column operation....................................................... 65
3.5.4 Total plate pressure drop......................................................................................... 68
3.6 Dehydration.................................................................................................................... 69
3.6.1 Theory of adsorption ............................................................................................... 70
3.7 Calculations of distillation unit ....................................................................................... 72
4 CHAPTER 4: WATER AND WASTEWATER TREATMENT ......................................................... 80
4.1 INTRODUCTION............................................................................................................... 80
4.2 Water treatment............................................................................................................. 80
4.2.1 Treatment steps....................................................................................................... 81
4.3 Wastewater treatment (process condensate)................................................................ 81
4.4 ETP (Effluent Treatment Plant)....................................................................................... 82
4.4.1 Available treatment options.................................................................................... 83
4.5 Dosing pumps ................................................................................................................. 85
4.5.1 Digital dosing pumps................................................................................................ 85
4.5.2 Mechanical diaphragm dosing pumps..................................................................... 86
4.6 Biological treatment ....................................................................................................... 87
4.6.1 Equalization tank...................................................................................................... 87
4.6.2 Anaerobic tank......................................................................................................... 90
4.6.3 Decanter room......................................................................................................... 92
4.6.4 Decanter Centrifuges............................................................................................... 93
4.6.5 Aeration tank ........................................................................................................... 94
4.7 Membrane system........................................................................................................ 101
4.8 Calculations................................................................................................................... 102
4.8.1 Flow calculations.................................................................................................... 102
4.8.2 Velocity calculation................................................................................................ 102
4.8.3 Chlorine dosage ..................................................................................................... 104
4.8.4 Hypochlorite dosage.............................................................................................. 104
4.8.5 Anaerobic Digestion............................................................................................... 105
4.8.6 Decanter................................................................................................................. 109
4.8.7 Aeration ................................................................................................................. 110
.84.8 Reverse osmosis calculations................................................................................. 112
4.9 References.................................................................................................................... 114
5 CHAPTER 5: EVAPORATION (VINASSE CONCENTRATION UNIT) ......................................... 116
5.1 INTRODUCTION............................................................................................................. 116
5.1.1 Process description................................................................................................ 116
5.1.2 Purposes of Evaporation........................................................................................ 118
5.1.3 Industrial Applications ........................................................................................... 118
5.2 Thermodynamics of Evaporation.................................................................................. 118

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5.2.1 What happens during Evaporation?...................................................................... 118
5.2.2 Mechanism of evaporation.................................................................................... 118
5.2.3 Processing factors – liquid characteristic............................................................... 119
5.2.4 Effect of processing variables ................................................................................ 120
5.3 Thermal design of evaporator ...................................................................................... 120
5.4 Classification of evaporators ........................................................................................ 121
5.4.1 Rising-film Evaporator............................................................................................ 121
5.4.2 Falling Film Evaporators......................................................................................... 121
5.4.3 Forced circulation evaporators.............................................................................. 122
5.5 Evaporator configuration.............................................................................................. 123
5.5.1 Single stage evaporators........................................................................................ 123
5.5.2 Multi-effect evaporators........................................................................................ 124
5.5.3 Optimization of Multiple Effect Evaporators......................................................... 126
5.6 Quadrable effect evaporator........................................................................................ 127
5.7 Plate evaporator........................................................................................................... 127
5.7.1 working modes....................................................................................................... 129
5.7.2 AlfaFlash................................................................................................................. 131
5.7.3 Plate technology .................................................................................................... 131
5.7.4 Patterns.................................................................................................................. 131
5.7.5 Plate Types............................................................................................................. 132
5.7.6 Plate condensers.................................................................................................... 136
5.7.7 Counter vs co counter............................................................................................ 136
5.7.8 Arrangement of a plate heat exchanger................................................................ 137
5.7.9 Plate materials ....................................................................................................... 138
5.7.10Plate geometry....................................................................................................... 139
5.7.11Gaskets................................................................................................................... 139
5.7.12Frames materials.................................................................................................... 141
5.7.13Plate Evaporator Manufacturer:............................................................................ 141
5.8 AlfaVap.......................................................................................................................... 141
5.9 Separators..................................................................................................................... 144
5.9.1 Selection Criteria for Vapor-Liquid Separators...................................................... 144
5.9.2 Feed Inlet ............................................................................................................... 145
5.10 Theory of Vertical Separators....................................................................................... 146
5.10.1Orientation of the Vessel....................................................................................... 146
5.10.2Theory of Separators Applied To V-L Systems....................................................... 147
5.10.3Separator Sizing Principles..................................................................................... 149
5.10.4Sizing Demister Pads.............................................................................................. 151
5.10.5Control facilities..................................................................................................... 153
6 CHAPTER 6: CARBON DIOXIDE LIQUEFACTION UNIT .......................................................... 166
6.1 INTRODUCTION............................................................................................................. 166
6.2 Air pollution.................................................................................................................. 167
6.3 Carbon dioxide.............................................................................................................. 168
6.3.1 Discovery of carbon dioxide................................................................................... 169

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6.3.2 Properties of carbon dioxide ................................................................................. 169
6.4 Sources of carbon dioxide ............................................................................................ 171
6.5 Source of carbon dioxide in the project ....................................................................... 175
6.6 Applications of Carbon Dioxide .................................................................................... 177
6.6.1 Gas CO2 .................................................................................................................. 177
6.6.2 Liquid CO2............................................................................................................... 182
6.6.3 Solid CO2 (dry ice) .................................................................................................. 184
6.6.4 Supercritical CO2 .................................................................................................... 185
6.6.5 Future Thrusts of CO2 in Food and Processing Industries..................................... 188
6.7 Process equipment's..................................................................................................... 189
6.7.1 Major Equipment & How the process occurs........................................................ 191
7 CHAPTER 7: AUXILIARY EQUIPMENT’S................................................................................ 197
7.1 Cooling tower ............................................................................................................... 197
7.1.1 INTRODUCTION...................................................................................................... 197
7.1.2 Cooling Tower Types.............................................................................................. 197
7.1.3 Components of Cooling Tower .............................................................................. 197
7.1.4 Tower Materials..................................................................................................... 199
7.1.5 Cooling tower for fermentation section................................................................ 200
7.1.6 Cooling tower of rest all section............................................................................ 203
7.2 Boiler Selection............................................................................................................. 206
8 CHAPTER 8: FIREFIGHTING.................................................................................................. 220
8.1 Detectors ...................................................................................................................... 220
8.1.1 Heat Detector......................................................................................................... 220
8.2 Foam............................................................................................................................. 222
8.2.1 How foam extinguishes a flammable liquid fire .................................................... 222
8.2.2 Alcohol resistant-aqueous film forming foam (ar-afff).......................................... 223
9 CHAPTER 9: TANKS.............................................................................................................. 224
9.1 INTRODUCTION............................................................................................................. 224
9.2 Types of storage tanks.................................................................................................. 224
9.2.1 Fixed-Roof Tank ..................................................................................................... 225
9.2.2 External Floating Roof Tank................................................................................... 225
9.2.3 Internal Floating Roof Tank.................................................................................... 226
9.2.4 Domed External Floating Roof Tank ...................................................................... 226
9.2.5 Horizontal Tank...................................................................................................... 227
9.2.6 Variable Vapor Space Tank .................................................................................... 227
9.2.7 LNG Storage Tank................................................................................................... 227
9.3 Floating Roof Tanks ...................................................................................................... 228
9.3.1 History and Introduction........................................................................................ 228
9.3.2 Principles of the Floating Roof............................................................................... 228
9.3.3 Advantages of the floating roof storage tank........................................................ 229
9.3.4 Process Description and Requirements................................................................. 230
9.4 Shell Design................................................................................................................... 232
9.5 Fixation ......................................................................................................................... 237

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9.5.1 Types of pipe support ............................................................................................ 238
9.5.2 Details of drain tube C1 R1 pdf:............................................................................. 241
9.6 Welding......................................................................................................................... 242
9.6.1 Types of welding .................................................................................................... 242
9.6.2 Weld Size................................................................................................................ 242
9.6.3 Welding Symbols.................................................................................................... 243
10 APPENDIX I: HYSYS REPORTS............................................................................................... 247
10.1 Fermentation hysys report........................................................................................... 247
10.2 Carbon dioxide hysys report......................................................................................... 258
10.2.1Streamlines composition ....................................................................................... 259
10.2.2Process equipment: ............................................................................................... 269
10.2.3Important functions............................................................................................... 277
1 APPENDIX II: TANK DRAWINGS ........................................................................................... 278
2 APPENDIX III: P AND ID........................................................................................................ 282
11 References........................................................................................................................... 286

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Table of Figures
Figure 1-1 Structure of ethanol.................................................................................................. 11
Figure 1-2 Molasses.................................................................................................................... 13
Figure 2-1 Fermentor ................................................................................................................. 19
Figure 2-2 Multistage continuous separation: Multiple separate addition is our case ............. 23
Figure 2-3 level controller .......................................................................................................... 23
Figure 2-4 single stage continuous system................................................................................. 23
Figure 2-5 Domnick -hunter sterile air filter............................................................................... 25
Figure 2-6 Disk-bowl centrifuge ................................................................................................. 34
Figure 2-7 Theory of centrifugation ........................................................................................... 34
Figure 3-1 Distillation unit.......................................................................................................... 36
Figure 3-2 Fractional column...................................................................................................... 41
Figure 3-3 Steam distillation....................................................................................................... 42
Figure 3-4 Schematic drawing of vacuum distillation ................................................................ 43
Figure 3-5 Azeotropic distillation for the separation of ethanol from water using benzene as
entrainer..................................................................................................................................... 44
Figure 3-6 Azeotropic Distillation Without an Entraining Agent................................................ 45
Figure 3-7 Azeotropic Distillation Using Pressure Swings .......................................................... 46
Figure 3-8 Tray column............................................................................................................... 48
Figure 3-9 Sieve tray................................................................................................................... 48
Figure 3-10 Tray column............................................................................................................. 48
Figure 3-11 Dual flow tray......................................................................................................... 50
Figure 3-12 Valve tray................................................................................................................. 51
Figure 3-13 Bubble cap tray ....................................................................................................... 51
Figure 3-14 Packings................................................................................................................... 52
Figure 3-15 Vertical reboiler....................................................................................................... 54
Figure 3-16 Kettle type reboiler ................................................................................................. 54
Figure 3-17 Internal reboiler ...................................................................................................... 54
Figure 3-18 Vent condenser ....................................................................................................... 55
Figure 3-19 Fractional distillation column.................................................................................. 56
Figure 3-20 Mass balance a cross distillation column................................................................ 60
Figure 3-21 Operating line for the rectification section............................................................. 61
Figure 3-22 Operating Line for the Stripping Section................................................................. 62
Figure 3-23.................................................................................................................................. 62
Figure 3-24 tray number using graphical solution ..................................................................... 63
Figure 3-25 Feed line.................................................................................................................. 64
Figure 3-26 Dehydration section................................................................................................ 72
Figure 4-1 Block flow diagram.................................................................................................... 83
Figure 4-2 Block flow diagram.................................................................................................... 83
Figure 4-3 P and ID ..................................................................................................................... 84
Figure 4-4 Schematic view of equalization-homogenization tank ............................................. 88
Figure 4-5 Process condensate treatment plant........................................................................ 89
Figure 4-6 Equalization tank....................................................................................................... 89
Figure 4-7 Anaerobic hybrid reactor .......................................................................................... 91

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Figure 4-8 Anaerobic digestor.................................................................................................... 92
Figure 4-9 Process condensate tank........................................................................................... 93
Figure 4-10 Flottweg decanter................................................................................................... 93
Figure 4-11 Decanter................................................................................................................. 94
Figure 4-12 Aeration tank........................................................................................................... 96
Figure 4-13 Aeration tank real view........................................................................................... 96
Figure 4-14 Types of Aeration .................................................................................................... 97
Figure 4-15 Types of Diffuser ..................................................................................................... 97
Figure 4-16 Aeration blowers..................................................................................................... 98
Figure 4-17 Aeration Diffusers ................................................................................................... 99
Figure 4-18 Aeration blowers..................................................................................................... 99
Figure 4-19 Block flow diagram................................................................................................ 101
Figure 4-20 Reverse osmosis.................................................................................................... 101
Figure 4-21 RO skid................................................................................................................... 101
Figure 4-22 Reverse osmosis vessel ......................................................................................... 101
Figure 4-23 Schematic drawings of septic tanks ...................................................................... 109
Figure 4-24 Flottweg decanter................................................................................................. 109
Figure 5-1 General description of how Vinasse can be treated and processed....................... 117
Figure 5-2 Schematic drawing of evaporator........................................................................... 117
Figure 5-3 Rising vs Falling Film evaporator............................................................................. 122
Figure 5-4 Forced circulation evaporator................................................................................. 123
Figure 5-5 Simplified diagram of single –effect evaporator..................................................... 124
Figure 5-6 Backward-feed, triple-effect ................................................................................... 125
Figure 5-7 Forward -feed, triple effect..................................................................................... 125
Figure 5-8 Quadrable effect evaporator .................................................................................. 127
Figure 5-9 Comparison between multi-effect plate and tubular evaporator .......................... 127
Figure 5-10 Plate evaporator.................................................................................................... 128
Figure 5-11 Comparison of plate and sht heat exchanger ....................................................... 129
Figure 5-12 Once through Mode.............................................................................................. 129
Figure 5-13 Forced circulation with boiling.............................................................................. 130
Figure 5-14 Thermo siphon mode............................................................................................ 130
Figure 5-15 Forced circulation with flashing ............................................................................ 131
Figure 5-16 Typical cathegories of plate corrugations. (a) washboard, (b) zigzag, (c) chevron or
herringbone, (d) protrusions and depressions (e) washboard with secondary corrugations, e (f)
oblique washboard [3]. ............................................................................................................ 132
Figure 5-17 Wide gap plate ...................................................................................................... 132
Figure 5-18 gap between plates............................................................................................... 133
Figure 5-19 double wall plate................................................................................................... 133
Figure 5-20 laser welding ......................................................................................................... 134
Figure 5-21 Semi welded plate................................................................................................. 134
Figure 5-22 Semi welded plate................................................................................................. 134
Figure 5-23 semi-welded plate................................................................................................ 135
Figure 5-24 Plate evaporator.................................................................................................... 135
Figure 5-25 Leakage detection hole ......................................................................................... 135
Figure 5-26 plate condenser..................................................................................................... 136

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Figure 5-27 plate vs sht counter flow comparision.................................................................. 137
Figure 5-28 U arrangement and Z arrangement...................................................................... 138
Figure 5-29 Multi-pass PHE ...................................................................................................... 138
Figure 5-30 Four possible 4-1 arrangements ........................................................................... 138
Figure 5-31 Four possible 3-2 arrangements ........................................................................... 138
Figure 5-32 AlphaVap Models .................................................................................................. 141
Figure 5-33 Comparison between space of sht and plate....................................................... 143
Figure 5-34 Alignment of demister pad ................................................................................... 152
Figure 6-1 Carbon dioxide levels in the atmosphere................................................................ 168
Figure 6-2 Molecule of carbon dioxide..................................................................................... 170
Figure 6-3 Phase diagram of carbon dioxide............................................................................ 170
Figure 6-4 Carbon dioxide from fossil fuel combustion ........................................................... 172
Figure 6-5 Human sources of carbon dioxide........................................................................... 172
Figure 6-6 Natural sources of carbon dioxide .......................................................................... 173
Figure 6-7 Industrial carbon dioxide emissions in different countries..................................... 174
Figure 6-8 CO2 Produced from Brewing................................................................................... 177
Figure 6-9 Demister ped........................................................................................................... 191
Figure 6-10 Screw compressor structure ................................................................................. 191
Figure 6-11 Oil lubrication compressor.................................................................................... 192
Figure 6-12 After cooler ........................................................................................................... 192
Figure 6-13 High pressure scrubber ......................................................................................... 193
Figure 6-14 Twin tower drayer................................................................................................. 193
Figure 6-15 Condenser ............................................................................................................. 194
Figure 6-16 Gas- liquid separator............................................................................................. 194
Figure 6-17 Reflux condenser................................................................................................... 195
Figure 6-18 Stripping column ................................................................................................... 196
Figure 7-1 Cooling water system.............................................................................................. 197
Figure 7-2 Cooling tower types ................................................................................................ 198
Figure 7-3 Cooling Tower and chiller plant piping.................................................................... 201
Figure 8-1.................................................................................................................................. 220
Figure 8-2.................................................................................................................................. 221
Figure 9-1 Breather Valve (pressure-vacuum Valve)................................................................ 225
Figure 9-2 Storage tank capacities levels ................................................................................. 230
Figure 9-3 Tank bottom Plate................................................................................................... 230
Figure 9-4 conical bottom with sluice point device ................................................................. 231
Figure 9-5 Rotational of the shell to bottom connection ........................................................ 232
Figure 9-6 Longitudinal Stress .................................................................................................. 233
Figure 9-7 Circumferential stress ............................................................................................. 234
Figure 9-8.................................................................................................................................. 236
Figure 9-9 Tank Shell Testing.................................................................................................... 237
Figure 9-10 Rigid springs .......................................................................................................... 238
Figure 9-11 Variable spring hanger .......................................................................................... 238
Figure 9-12 Variable spring hanger .......................................................................................... 238
Figure 9-13................................................................................................................................ 239
Figure 9-14................................................................................................................................ 239

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Figure 9-15................................................................................................................................ 240
Figure 9-16................................................................................................................................ 240
Figure 9-17................................................................................................................................ 240
Figure 9-18 Drain tube.............................................................................................................. 241
Figure 9-19 Details of drain tube.............................................................................................. 241
Figure 9-20 Sheet clamping...................................................................................................... 241
Figure 9-21 Welding symbols ................................................................................................... 243
Figure 9-22 Horizontal shell joints............................................................................................ 244
Figure 9-23 Method for Preparing Lap-Welded Bottom Plates under Tank Shell ................... 244
Figure 9-24 Spacing of Three-Plate Welds at Annular Plates................................................... 245

INTRODUCTION
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1 INTRODUCTION
Ethyl Alcohol (Ethanol) C2H5OH is an Aliphatic hydrocarbon containing hydroxyl
group (-OH), Its name is the systematic name defined by the International Union of
Pure and Applied Chemistry (IUPAC) for a compound consisting of alkyl group with
two carbon atoms (prefix “eth-”), having a single bond between them (infix “-an-”),
attached functional group −OH group (suffix “-ol”). With Chemical formula of
C2H6O or better be CH3-CH2-OH.
The physical and chemical properties of ethanol stem primarily from the presence
of its hydroxyl group and the shortness of its carbon chain.
This group imparts polarity to the molecule and gives rise to intermolecular
hydrogen bonding. These two properties account for the differences between the
physical behavior of lower molecular weight alcohols and that of hydrocarbons of
equivalent weight.
1.1 Physical properties
Ethanol under ordinary conditions is a volatile, flammable, clear, colorless liquid.
Its odor is pleasant, familiar, and characteristic, as is its taste when suitably diluted
with water. The most amazing property of ethanol is the volume shrinkage that
occurs when it is mixed with water, or the volume expansion that occurs when it is
mixed with gasoline. It burns with a smokeless blue flame that is not always visible
in normal light. Ethanol's hydroxyl group is able to participate in hydrogen bonding,
rendering it more viscous and less volatile than less polar organic compounds of
similar molecular weight, such as propane.
Molar Mass 46.069 gm/mol
Density at 20 °C 789.3 kg/cm3
Boiling point at 1 Bar 78.32 °C
Viscosity at 20 °C 1.17 mPa.s
Heat combustion at 25 °C 29686.69 J/gc
Melting point −114.14 °C
Figure 1-1 Structure of ethanol

INTRODUCTION
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1.2 Chemical properties
Reactions of dehydration, dehydrogenation, oxidation, and esterification.
The hydrogen atom of the hydroxyl group can be replaced by an active metal, such
as Sodium, to form a metal ethoxide (ethylate) with the evolution of hydrogen gas.
Barbiturates (Verona, Barbital, Luminal, Amytal), ethyl orthoformate, and other
chemicals are produced commercially from sodium ethoxide.
Aluminum and magnesium also react to form ethoxides, but the reaction must be
catalyzed by amalgamating the metal (adding a small amount of mercury).
1.3 Manufacture
Industrial ethyl alcohol can be produced synthetically from ethylene, as a by-
product of certain industrial operations, or by the fermentation. There are two main
processes for the synthesis of ethyl alcohol from ethylene. The earliest to be
developed was the indirect hydration process and the other is direct hydration
process.
1. Indirect hydration (Esterification–Hydrolysis) process
Preparation from ethylene by the use of sulfuric acid is a three-step
process:
1. Absorption of ethylene in concentrated sulfuric acid to form
monomethyl sulfate (ethyl hydrogen sulfate) and diethyl
sulfate
2CH2=CH2 + H2SO4 (CH3CH2O)2SO2
2. Hydrolysis of ethyl sulfates to ethanol:
(CH3CH2O)2SO2 + 2 H2O 2 CH3CH2OH + H2SO4
3. Re-concentration of the dilute sulfuric acid.
1. Direct hydration process
Hydration of ethylene to ethanol via a liquid-phase process catalyzed
by dilute sulfuric acid, the passage of an ethylene-steam mixture over
alumina at 300◦C was found to give a small yield of acetaldehyde, and
it was inferred that this was produced via ethanol. Then, several
industrial concerns have expressed interest in producing ethanol
synthetically from ethylene over solid catalysts.
There are two main process categories for the direct hydration of
ethylene to ethanol. Vapor-phase processes contact a solid or liquid
catalyst with gaseous reactants. Mixed-phase processes contact a
solid or liquid catalyst with liquid and gaseous reactants.

INTRODUCTION
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3. Fermentation
It is one of the oldest chemical processes known, it is used to make a variety
of products, including fuel, foods, flavorings, beverages, chemicals and
pharmaceuticals.
Fermentation processes was accounting for 83% of total production and by
2001 fermentation increased to 90%. Ethanol can be derived by
fermentation processes from any material that contains sugar or compounds
that can be converted to sugar mostly corn even though before World War II
molasses was the chief feedstock. Other agricultural products such as grains,
sugar cane and beets, fruit, whey, and sulfite waste liquor. Studies are
underway to ferment garbage to ethanol.
➢ Sugar Beet Molasses
Only the syrup left from the final crystallization stage is called
molasses. Beet molasses is 50% sugar by dry weight, predominantly
sucrose. Molasses is a microbiological energy source that helps in the
process of growing yeast and bacteria. Beet molasses is limited in
biotin for cell growth; hence, it may be supplemented with a biotin
source important for growth of bacteria and yeasts accelerating
fermentation for ethanol production.
1.4 Uses of Ethanol
➢ Medical
✓ Antiseptic
Used as antibacterial, antiseptic for its bactericidal and anti-fungal
effects. Ethanol kills organisms by denaturing their proteins and
dissolving their lipids and is effective against most bacteria and fungi,
and many viruses but not bacterial spores. 70% ethanol is the most
effective concentration, particularly because of osmotic pressure.
Absolute ethanol may inactivate microbes without destroying them
because the alcohol is unable to fully permeate the cellular membrane.
Ethanol can also be used as a disinfectant and antiseptic because it
Figure 1-2 Molasses

INTRODUCTION
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causes cell dehydration by disrupting the osmotic balance across cell
membrane, so water leaves the cell leading to cell death.
✓ Antidote
Used as an antidote to methanol and ethylene glycol poisoning.
✓ Medicinal solvent
Used in high concentrations to dissolve many water-insoluble
medications and related compounds.
✓ Medication
Used as main central nervous system depressant drug.
➢ As a fuel
✓ Engine fuel
The largest single use of ethanol is as an engine and fuel additive. In
Brazil gasoline sold contains at least 25% anhydrous ethanol while
hydrous ethanol can be used as fuel in more than 90% of new gasoline
fueled cars.
✓ Rocket fuel
Ethanol was commonly used as fuel in early bipropellant rocket (liquid
propelled) vehicles, in conjunction with an oxidizer such as liquid
oxygen.
✓ Fuel cells
Commercial fuel cells operate on reformed natural gas, hydrogen or
methanol. Ethanol is an attractive alternative due to its wide
availability, low cost, high purity and low toxicity.
✓ Household heating
Ethanol fireplaces can be used for home heating or for decoration.
➢ Feedstock
Ethanol is an important industrial ingredient. It has widespread use as a
precursor for other organic compounds such as ethyl halides, ethyl esters,
diethyl ether, acetic acid, and ethyl amines.
➢ Solvent
Ethanol is considered a universal solvent, as its molecular structure allows
for the dissolving of both polar, hydrophilic and nonpolar, hydrophobic
compounds allowing easy extraction of botanical oils.

INTRODUCTION
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As ethanol also has a low boiling point, it is easy to remove from a solution
that has been used to dissolve other compounds and also as a post-
processing solvent to remove oils, waxes, and chlorophyll from solution in a
process known as winterization. Ethanol is found in paints, tinctures,
markers, and personal care products such as mouthwashes, perfumes and
deodorants. However, polysaccharides precipitate from aqueous solution in
the presence of alcohol, and ethanol precipitation is used for this reason in
the purification of DNA and RNA.
➢ Low-temperature liquid
Because of its low melting point (−114.14 °C) and low toxicity, it is used in
laboratories as a cooling bath to keep vessels at temperatures below the
freezing point of water.
For the same reason, it is also used as the active fluid in alcohol
thermometers.

CAPTER 2: FERMENTATION SECTION
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2 CHAPTER 2: FERMENTATION SECTION
2.1 INTRODUCTION
Fermentation is a bio-chemical reaction where the substrate is converted into
desired product with the help of micro-organism which may be yeast, Mould or
bacteria and the enzyme present in the Microorganism actually acts in the reaction.
Reaction: C6 H12 O6 ------> 2 C2 H5 OH + 2 CO2
(sugar) (alcohol)
The yeast Saccharomyces cerevisiae that is used for the culture for Alcohol
fermentation is having two kinds of enzymes, one’s INVERTASE and other is
ZYMASE. Invertase converts sucrose to invert sugar and Zymase converts invert
sugar into Ethyl Alcohol. Fermentation is a dynamic process involving a series of
reactions. These are:
1. Enzymes added after cooling continuous to convert the gelatinized starch
to dextrin’s and fermentable sugars.
2. The yeast metabolizes sugar to acetaldehydes and then to ethanol. The cycle
is known as Glycolysis. The lactic acid bacteria produce small amounts of a
variety of products, some of which are volatile and contribute to the
congeners in the distillate.
Molasses is transported in the cells via specific carrier proteins called Permeases
where it is hydrolyzed into 2 molecules of glucose. The Permeases are substrate
and require metabolic energy for operation.
C6H12O6 --> 2 C2H5OH +2 CO2 + 2 ATP + heat
Two moles of ATP (Adenosine Triphosphate) are also produced which are used to
supply energy for cell maintenance and growth. Theoretically conversion of 1gm of
glucose via fermentation yields 0.511grms of ethanol. This theoretical value is
never obtained due to carbohydrate utilization for cell maintenance, growth and
formation of small amounts of glycerol's and higher alcohols.
Fermentation efficiency also depends upon factors such as yeast strain and
environmental parameters. In practice efficiency is 60-80%. An increase in temp
within a certain range increases activity. The condition in Fermentation vats are
such obtained so as to avoid bacterial action. During a normal Fermentation heat is
produced from active yeast growth and metabolism which causes a rise in temp.
Then this temp rise can drastically affect yeast metabolism and ethanol. An average
upper limit temp for growth is around 40’ C with an optimum temp of about 30’C.
Increased heat tolerances are obtained with media containing oleic acid. The
maximum concentration of ethanol that yeast can produce depends upon the yeast
strain used. In general, yeast cell growth is inhibited around 10 to 12% wt/vol.
ethanol while 20% ethanol will terminate cellular metabolism.

Page | 18
2.2 Ethanol Fermentation with Yeast
The organisms of primary interest to industrial operations in fermentation of
ethanol include Saccharomyces cerevisiae, S. uvarum, Schizosaccharomyces pombe,
and Kluyueromyces sp. Yeast, under anaerobic conditions, metabolize glucose to
ethanol primarily by way of the Embden-Meyerhof pathway. The overall net
reaction involves the production of 2 moles each of ethanol, but the yield attained
in practical fermentations however does not usually exceed 90 – 95% of theoretical.
This is partly due to the requirement for some nutrient to be utilized in the synthesis
of new biomass and other cell maintenance related reactions.
A small concentration of oxygen must be provided to the fermenting yeast as it is a
necessary component in the biosynthesis of polyunsaturated fats and lipids. Typical
amounts of O2 maintained in the broth are 0.05 – 0.10 mm Hg oxygen tension. The
relative requirements for nutrients not utilized in ethanol synthesis are in
proportion to the major components of the yeast cell. These include carbon oxygen,
nitrogen and hydrogen. To lesser extent quantities of phosphorus, sulfur,
potassium, and magnesium must also be provided for the synthesis of minor
components. Minerals (i.e. Mn, Co, Cu, Zn) and organic factors (amino acids, nucleic
acids, and vitamins) are required in trace amounts. Yeast are highly susceptible to
ethanol inhibition. Concentration of 1-2% (w/v) are sufficient to retard microbial
growth and at 10% (w/v) alcohol, the growth rate of the organism is nearly halted.
Fermentation at PDM is done through two ways:
1. Grain spirit plant (From wheat or rice flour).
2. Fermentation from Molasses.
PROCESS PARAMETERS
a. NUTRIENTS: Generally, di ammonium phosphate (DAP) and urea are
used as nutrients. These are used so as to form amino acid to give energy
and to carry out propagation faster.
b. TEMPERATURE: Temperature of the material in the fermenter is 32 to
34 °C.
c. PRESSURE: The process is carried out at Normal Pressure.
d. ANTIFOAM: 25% Silicon antifoam was prepared to control the foam
formation in the pre-fermenter and the fermenter.
2.3 What is a Fermentor?
A Fermentor can be defined as a vessel in which sterile nutrient media and pure
culture of micro-organism are mixed and fermentation process is carried out under
aseptic and optimum condition.
Fermentor provides a sterile environment and optimum condition that are
important for growth of micro-organisms and synthesis of desired product.

Page | 19
A fermentor should be constructed in such a way that it can make provisions for the
below activities:
▪ Sterilization.
▪ Temperature control.
▪ pH control.
▪ Foam control.
▪ Aeration and agitation.
▪ Sampling point.
▪ Inoculation points for micro-organisms, media and supplements.
▪ Drainage point for drainage of fermented media.
▪ Harvesting of product.
▪ Cleaning.
▪ Facility of providing hot, cold water and sterile compressed air.
Figure 2-1 Fermentor

Page | 20
Here one by one we will be studying major parts of fermentor and their function.
▪ Material used for fermentor
▪ Impellers
▪ Baffles
▪ Inoculation port
▪ Sparger
▪ Sampling point
▪ pH control device
▪ Temperature control system
▪ Foam control device
▪ Bottom drainage system
1. Material used for fermentor
The material used for designing of a fermentor should have some important
functions.
▪ It should not be corrosive
▪ It should not add any toxic substances to the fermentation media.
▪ It should tolerate steam sterilization process.
▪ It should be able to tolerate high pressure and resist pH changes.
The fermentor material used is also decided on type of fermentation process.
For example, in case of Beer, Wine, Lactic acid fermentation, the fermentor
tanks are made up of wooden material. Whereas material such as iron,
copper, glass and stainless steel can be used in some cases. Most of the time,
304 and 316 stainless steel is used for designing of a fermentor and these
fermentors are mostly coated with epoxy or glass lining.
A fermentor should provide the facility to control and monitor various
parameters for a successful fermentation process.
2. Impellers
▪ Impellers are an agitation device. They are mounted on the shaft and
introduced in the fermentor through its lid.
▪ They are made up of impeller blades and the position may vary
according to its need.
▪ These impellers or blades are attach to a motor on lid.
▪ The important function of an impeller is to mix micro-organisms,
media and oxygen uniformly.
▪ Impeller blades reduce the size of air bubbles and distributes these
air bubbles uniformly into the fermentation media.
▪ Impellers also helps in breaking foam bubbles in the head space of
fermentor. This foam formed during fermentation process can cause
contamination problem and this problem is avoided by the use of
impellers.

Page | 21
3. Baffles
▪ Baffles are mounted on the walls of a fermentor.
▪ The important function of baffles is to break the vortex formed during
agitation process by the impellers.
▪ If this vortex is not broken, the fermentation media may spill out of
fermentor and this may result in contamination as well as can lead to
different problems. So, it is important to break the vortex formed by
using a barrier.
▪ Baffles acts as a barrier which break the vortex.
4. Inoculation Port
▪ Inoculation port is a device from which fermentation media,
inoculum and substrate are added in the fermentation tank.
▪ Care should be taken that the port provides aseptic transfer.
▪ The inoculation port should be easy to sterilize.
5. Spargers
▪ A Sparger is an aeration system through which sterile air is
introduced in the fermentation tank.
▪ Spargers are located at the bottom of the fermentation tank.
▪ Glass wool filters are used in a sparger for sterilization of air and
other gases.
▪ The sparger pipes contain small holes of about 5-10 mm. Through
these small holes pressurized air is released in the aqueous
fermentation media.
▪ The air released is in the form of tiny air bubbles. These air bubbles
helps in mixing of media.
6. Sampling point
▪ Sampling point is used for time to time withdrawal of samples to
monitor fermentation process and quality control.
▪ This sampling point should provide aseptic withdrawal of sample.
7. pH Control device
▪ The pH controlling device checks the pH of media at specific intervals
of time and adjusts the pH to its optimum level by addition of acids or
alkalis.
▪ Maintaining pH to its optimum level is very important for growth of
micro-organism to obtain a desired product.

Page | 22
8. Temperature control
▪ Temperature control device generally contains a thermometer and
cooling coils or jackets around fermentor.
▪ During the fermentation process, various reactions take place in the
fermentor. Heat is generated and released in the fermentation media.
This increase in temperature is detrimental to the growth of micro-
organisms, which may slow down the fermentation process.
▪ So, it is necessary to control this rise in temperature. This is done by
passing cool water through the coils or jackets present around
fermentor.
9. Foam controlling device
▪ A Foam controlling device is placed on the top of fermentor with an
inlet into fermentor. This device contains a small tank containing
anti-foaming agent.
▪ Foam is generated during fermentation. It is necessary to remove or
neutralize this foam with the help of anti-foaming agents, lest the
media may spill out of fermentor and lead into contamination and a
mess.
10.Bottom drainage system
▪ It is an aseptic outlet present at the bottom of fermentor for removal
of fermented media and products formed.
2.4 Classification of Fermentation Processes
1. Batch process
2. Fed-batch process (semi-batch process)
3. Repeated fed-batch process (cyclic fed-batch process)
4. Repeated fed-batch process (semi-continuous process or cyclic batch
process)
5. Continuous process
The continuous operations are three types of operations. without feedback control,
the feed medium containing all the nutrients is continuously fed at a constant rate
(dilution rate) and the cultured broth is simultaneously removed from the
fermenter at the same rate. A. This type is quite useful in the optimization of media
fonnulation and to investigate the physiological state of the microorganism, with
feedback control is a continuous process to maintain the cell concentration at a
constant level by controlling the medium feeding rate, with feedback control is a
cultivation technique to maintain a nutrient concentration at a constant level, an
extended nutristat which maintains the pH value of the medium in the fermenter at
a preset value.

Page | 23
Figure 2-2 Multistage continuous separation: Multiple separate addition is
our case
Figure 2-3 level controller
Figure 2-4 single stage continuous system

Page | 24
2.5 The Main Fermenter Layout
For simplicity of piping, especially the utility piping, the fermenters are usually
placed in a straight line, sometimes two or more parallel lines . In this manner the
plant is easily expanded, and other tank layouts do not seem as convincing. It is
desirable to have the working platform extend completely around the
circumference of the top dish, and to have enough room between tanks for
maintenance carts (1 to 1.5 meters). Good lighting and ventilation on the working
platform should not be overlooked. Using water from hoses for cleaning is common
so care must be taken to have nonskid floors with adequate drains, especially at the
top of stairs. Open floor grating is not desirable.
All structural steel should be well primed to prevent corrosion from the very humid
atmosphere. Electronic instrumentation and computers must be placed in control
rooms which run at constant (HVAC) temperature. Most fermenter buildings are
between 40 and 100 feet high, making it possible to have one or more floors
between the ground floor and the main fermenter working platform. The
intermediate floors can be used for the utility and process piping, sterile air filters,
the sterile anti-foam system, instrumentation sensors (temperature, pH, DO, etc.),
heat exchangers, motor control center, laboratories and offices. Buildings 40 feet or
more high frequently have elevators installed.
Fermenters can be located outdoors in most countries of the world. The working
platforms usually are enclosed and heated in temperate zones, and only shaded in
more tropical zones. In more populated areas, open fermenter buildings make too
much noise for local residents. The environmental awareness, or the tolerance of
the public, could preclude open fermenter buildings in the future. Odor is also
offensive to the public. The environmental authorities are demanding that
equipment be installed to eliminate the offensive odor of the off gases. (Noise levels
inside a fermenter building will be greater than 90 dB if no preventive measures are
taken.) Harvest tanks can be justified as the responsibility of the fermentation or
recovery department. They are economical (carbon or stainless steel) and should
be insulated and equipped with cooling coils and agitator(s).
2.5.1 Nutrient Feed Tanks
Essential equipment to a productive fermentation department are sterilizable
tanks for nutrient feeds. Multiproduct plants usually require several different sizes
of feed tanks:
1. A small volume to be transferred once every 12 or 24 hours such as a
nitrogen source.
2. A large volume carbohydrate solution fed continuously, perhaps varying
with the fermenter volume.
3. A precursor feed fed in small amounts relative to assay data; (iv) anti-foam
(Some companies prefer a separate anti-foam feed system for each
fermenter.
4. Other tanks for acids, bases, salts, etc. Many companies prefer to batch
sterilize a known quantity and transfer the entire contents quickly.
Sometimes, the feeds require programming the addition rate to achieve
high productivity.

Page | 25
In this latter case, large volume tanks are used, and the contents are presterilized
(batch or continuous) or the feed is continuously sterilized between the feed tank
and the fermenter. Usually feed tanks are not designed as fermenters, even though
they are sterilizable, and there is no need for high volume air flow, but only
sufficient air pressure for the transfer. For solvable nutrients the agitator and anti-
foam system are not required. Since the air requirements are needed only to
transfer the feed, the air piping design is different, and the sterile air filter is
proportionately smaller. Instrumentation is usually limited to temperature,
pressure and volume. The HID ratio of the vessel can be near one for economy and
need not be designed for the aeration/agitation requirements of a fermenter.
2.5.2 Sterile Filters
Sterile air filtration is simple today with the commercial units readily available.
However, some companies still design their own to use a variety of filter media such
as carbon, cotton, glass staple, etc.
The essential method to obtain sterile air, whether packed-bed or cartridge filters
are used, is to reduce the humidity of the air after compression so that the filter
material always remains dry. The unsterilized compressed air must never reach
100% relative humidity. Larger plants install instrumentation with alarms set at
about 85% relative humidity. Careful selection of the cartridge design or the design
of packed-bed filters will result in units that can operate in excess of three years
without replacement of filter media. If a fiber material is used in a packed-bed type
filter, the finer the fiber diameter the shallower the bed depth needs to be for
efficient filtration. Other filter media are less common and tend to have special
problems and/or shorter life. The bed depth of filters is only 10 to 18 inches for
fibers of less than 10 microns. These filters run "clean" for 2 weeks or longer before
being resterilized.
Some plants have a separate filter for each sterile vessel. Others place filters in a
central group which feeds all the vessels. In this case, one filter, for example, might
be taken out of service. each day sterilized and put back into service. If there were
ten filters in the group, each one would be sterilized every tenth day. This system
has the advantage that the filter can be blown dry after sterilization with sterile air
before it is put into service again.
Figure 2-5 Domnick -hunter sterile air filter

Page | 26
2.5.3 Air Compressors
It is ideal to have oil-free compressed air. Centrifugal machines generally are
available up to 40,000 cfm. "Oil free" screw air compressors are available in smaller
sizes. Regarding oil-free screw type compressors, it is necessary to read the fine
print of the manufacturer. For example, one manufacturer uses no lubricant on the
screws and other claims to be oil free but does use a non-hydrocarbon liquid
lubricant. Carbon ring reciprocating compressors are available and used, but
maintenance is annoying. For small plants, non-lubricated screw compressors with
two-speed motors and constant pressure control will provide versatility. For large
plants, centrifugal air compressors, driven by non-condensing steam turbines with
50 psig steam extraction for process requirements, are suitable. In all cases, extra
considerations include locating the intake 20 feet or more above the ground level
and installing filters on the intake to the compressors to prevent dirt accumulation
on the sterile filters. Occasionally, the noise levels measured at the suction inlet
exceed OSHA regulations and bother the neighbors of the plant. The air from the
compressors requires heat exchangers to lower the air temperature below the dew
point, plus additional heat exchangers to reheat and control the air to have the
relative humidity at about 85%.
2.5.4 Valves
Most companies have tried gate, diaphragm, ball, and plug valves, to name a few.
Some have designed and patented special valves for the bottom or sample positions.
Some companies will disassemble all fermenter valves after an infected run. No
companies use threaded nipples or valves on a fermenter because the threads are a
site of potential infection. In general, valves are less of a sterility problem when a
continuous sterilizer is used for the substrate than fermenters which batch sterilize
the substrate. This is because, in the former case, the vessel is sterilized empty, and
all valves are opened and sterilized in an outward direction so that a steam plume
can be seen. The temperature of the valves during sterilization can be checked.
Batch sterilizing requires all valves below the liquid level to be sterilized with steam
passing through the valve into the substrate. This depends upon steam pressure and
how much the valve is opened (which might affect the PIT conditions of
sterilization). This is much more subject to human error and infection. Most plants
drill and tap the body of the valve near the valve seat in order to drain the
condensate away from all sections of pipe where a steam seal is required for
sterility. In general, diaphragm and ball valves require considerable maintenance,
but tend to be popular in batch sterilizing operations, while plug type valves are
more typical on fermenters where continuous sterilizers are used. Plug or
diaphragm valves are commonly used for inoculum transfer and sterile feed piping.
All the process valves and piping today are 316 SIS. Utility piping remains carbon
steel up to the first SIS valve on the fermenter. Valves used in non-process piping
are selected for the best type of service and/or control. Butterfly valves have been
used in applications where perfect closure is not essential, such as a vent valve. In
summary, the valves which maintain a sterile environment on one side and a non-

Page | 27
sterile environment on the other side are the essential valves. They must be devoid
of pockets, easily sterilized, maintained, and occasionally replaced.
2.5.5 Pumps
Apart from continuous sterilizers, pumps are a minor concern in the fermentation
department. A simple way to transfer inoculum from a large laboratory flask to a
fermenter, without removing the back pressure on the vessel, is to use a peristaltic
pump. Connect the sterile adapter (which is attached to the flask) to the fermenter
by sterile technique. Install the gum rubber tubing in the pump, open the hose clamp
and start the pump. Inoculum from sterile feeds are transferred to the fermenter by
air pressure. Centrifugal pumps (316 SIS) are used to pump non sterile raw
materials, slurries, harvested broth, etc. The centrifugal pumps and piping should
be cleaned immediately after a transfer has been completed. Occasionally a
specialty pump may be required.
2.5.6 Cooling Equipment
Cooling is required to cool media from sterilizing temperatures, to remove the
exothermic heat of fermentation, to cool broth before harvesting, and to cool the
compressed air. Some portion of the heat can be cleaned to produce hot water for
the preparation of new substrate, and for general cleaning of equipment, platforms
and floors, however, the excess heat must be disposed to the environment. Cooling
water is provided from cooling towers, but chilled water (5 15°C) is produced by
steam vacuum, or refrigeration units.
In any case, the fermentation department should always be concerned about its
cooling water supply, i.e., the temperature and chloride content. Chloride ions
above 150 ppm when stainless steel is above 80°C (while sterilizing) will cause
stress corrosion cracking of stainless steel.
A conductivity probe should be in the cooling water line. When the dissolved solids
(salts) get too high, it may indicate a process leak, or that the salt level is too high
and some water must be discharged and fresh water added. If cooling water is
discharged to a stream, river, etc., an NPDES permit may be needed and special
monitoring required. The chloride content should be determined analytically every
two weeks to control the chloride to less than 100 ppm. This is done by draining
water from the cooling tower and adding fresh water.
2.5.7 Environmental Control
Stack odors have to be avoided. Certain raw materials smell when sterilized. Each
fermentation process tends to have its own unique odor ranging from mild to strong
and from almost pleasant to absolutely foul. Due to the high volume of air
discharged from a large fermenter house, odor is neither easy nor cheap to
eliminate. Carbon adsorption is impractical.

Page | 28
Normally, more air is exhausted than required for steam production from the
boilers which eliminates that route of disposal. Wet scrubbing towers with sodium
hypochlorite are expensive ($1.50/yr. cfm), and discharge Na+ and Cl2 to the waste
system which may preclude this method. Ozone treatment can be effective. A very
tall exhaust stack for dilution of the off gas with the atmosphere before the odor
reaches the ground is possible in some cases but is not considered an acceptable
solution by U. S. Authorities.
The fermentation department should monitor and control the CODI BOD of its liquid
waste to the sewer. Procedures for cleaning up spills and reporting should be
Standard Operating Procedure. A primary aeration basin will reduce the COD to 80-
90 ppm. Secondary aeration lagoons will reduce the BOD to acceptable levels which
have no odor.
Noise levels are very difficult to reduce to Federal standards. Hearing protection for
employees is essential. The move towards greater automation has resulted in
operators having less exposure to noisy work areas.
2.5.8 General design data
Most companies produce more than one product by fermentation simultaneously.
It is not necessary to have separate fermenter buildings to isolate products. Well-
designed fermenters which are operated properly, not only keep infection out, but
prevent cross contamination of products. Over the years, most fermentation plants
have been enlarged by the addition of new fermenters despite major yield
improvements. Therefore, as plants grow, the engineer must always keep in mind
there will be a need for further expansions. The layout of labs, fermenter buildings,
the media preparation area and warehousing must be able to be expanded. Utilities
and utility piping must also be installed with spare capacity to handle average and
peak loads as well as future growth.
The fermentation department can consume up to 2/3 of the total plant electrical
requirements (depending upon the recovery process), which includes mechanical
agitation (usually 15 HP/l000 gal) and electrically driven air compressors.
There is no relationship between the cubic feet of compressed air for large
fermenters and their installed capacity. The compressed air required for fermenters
is calculated by linear velocity through the fermenter and the square feet of cross-
sectional area of a vessel, not its volume. Therefore, if volume is constant, short
squat vessels require more compressed air than tall slender vessels.
2.6 Fermentation section
The molasses from molasses storage is mixed with sucrose and Di ammonium
phosphate and Sodium hypochlorite. The temperature of the combined stream is
96 ºC and is to be cooled to fermentation temperature. The cooling of the broth is
carried through in two stages: the hot broth is passed through an heat exchanger
(E-1) in countercurrent with the cold mixing broth, where the mixing broth is
warmed and the broth for distillery is cooled.

Page | 29
Final cooling, approximately 30 Cº, is carried out in the fermenter (BR-1) During the
fermentation, sugar is converted to ethanol with 0.92 of the theoretical yield which
corresponds to 0.46-0.47 g ethanol/g sugar. The remaining substrate is utilized by
the microorganisms for maintenance, cell growth and production of by products
such as succinic acid, glycerol, acetic acid, higher alcohols and acetaldehyde. Also,
0.44-0.48 g CO2 / g sugar is produced during the ethanol fermentation.
Saccharomyces species is used as the ethanol fermenting microorganism. The
fermentation is carried out anaerobically to decrease cell growth and increase the
ethanol productivity.
The fermentation is carried out in 10 vessels to maintain a continuous operation
and to prevent requirement of extra storage tanks for broth and recycle biomass.
The biomass is recycled to maintain high cell concentrations in the fermenters. The
biomass is separated from the broth using continuous disc type centrifuges (S-1)
and sent to biomass sterilization vessel (V-1), which are stirred vessels to blend the
biomass with pH 2 acid solution (sulfuric acid). The residence time in the vessels
are set to 15 minutes. After the sterilization vessel, the biomass is separated from
the acid solutions using centrifuge (S-2). The sulfuric acid is taken outside the
battery limit without treatment, but the cost of waste treatment is included in the
cash flows.
The sulfuric acid requirement for this step is approximately 0.013 kg per kg ethanol
produced. Since, yeast functions at low pH values they are not affected by the pH
treatment. The biomass is recycled to fermenters. By recycling the cells, the long lag
growth phase is eliminated, and high cell concentrations are obtained in fermenters.
Very short fermentation times (6-10 h) allows yeast to be recycled up to three times
a day.
The carbon dioxide rich gas from the fermenters are passed through the ethanol
scrubber column (C-1) to absorb the ethanol in the gas to lower the volatile organic
emissions to atmosphere and to recover the lost ethanol. This column is not only
feed with the gas from the fermenter, but, also with the carbon dioxide rich vapor
distillate from the beer column. The absorption water is recycling water form the
evaporators and boiling pans. The water and ethanol content of the vent gas is 1-2
w/w %. Carbon dioxide can be sold either to beverage and food industries or to dry
ice production facilities.
The water scrubber can remove 99.5% of ethanol in carbon dioxide stream. The
environmental legislations set the upper limit of total volatile components to the
atmosphere as 36.3 T/year. Therefore, the total ethanol released will be set
accordingly.

Page | 30
2.6.1 Process Control
1. Flow Controllers (FC)
▪ Raw materials: sulfuric acid, di ammonium phosphate and sodium
hypochlorite should be weighted to maintain the process
specifications before being send to system.
▪ Air Stream: to prevent heat losses by excess air or incomplete
combustion with less air flow, the air streams flowing into the
furnace and dryer are to be controlled with flow controller to
maintain the required air.
▪ Distillate: bottoms and side products of the distillation columns.
2. Level Controllers (LC)
All the vessels with continuous inflow require a level controller to prevent
any flooding in case of any problem with pumping in/out. The level
controllers are operated based on the liquid height in the vessel and the
manipulated variable is the output flow from the vessel. The controller type
is to be “fail-on” to prevent the overflow of the vessels in case of controller
failure.
3. Ratio Controllers (RC)
The ratio controllers are necessary when the stream split into two or more
streams.
4. Temperature Controllers (TC)
The equipment involving heat transfer are to be supplied with temperature
controller to maintain constant operation conditions. The equipment and
streams that require temperature controller are listed below.
▪ Evaporators and boiling pans.
▪ reactors: The temperature is manipulated by steam input of the
pretreatment. The controller should be fail-close control valve to
prevent steam inflow in case of controller failure.
▪ All Heat exchangers
▪ Re boilers and condensers.
▪ Molecular sieve column.
5. Pressure Controllers (PC)
The equipment that requires a certain operation pressure other than
atmospheric requires pressure controller.
6. pH Controller (pHC)
The pH of the cellulose hydrolysis and fermentation bio reactors should be
monitored to maintain the pH in optimal value.

Page | 31
2.7 Fermentation process
2.7.1 Fermentors
In continuous fermenters, sucrose in juice is hydrolyzed to glucose and
glucose is fermented to microbial biomass, ethanol, carbon dioxide and
fermentation by-products. The fermentation by-products are assumed as
acetic acid, Iso amyl alcohol, glycerol and succinic acid. There are several by-
products of fermentation, but for simplicity only the dominating
components are considered. Fusel oil which is a side product of ethanol
distilleries composes of various organics such as, methanol, ethyl acetate, n-
propanol, iso-butanol, ethyl butyrate, 2-butanol, iso-amyl alcohol, n butanol,
n-propanol and isopropanol. Iso-amyl alcohol is reported as the dominant
component for fusel oil. The growth conditions in the vessel are 30ºC
temperature and pH 4.5.
Fermenter Cooling
When designing a fermenter, one primary consideration is the removal Of
heat. There is a practical limit to the square feet of cooling surface that can
be achieved from a tank jacket and the number of coils that can be placed
inside the tank. The three sources of heat to be removed are from the cooling
of media after batch sterilization, from the exothermic fermentation process,
and the mechanical agitation.
The preceding topic about the design of a continuous sterilizer emphasized
reduced turnaround time, easier media sterilization, higher yields and one
speed agitator motors. The reduced turnaround time is realized because the
heat removal after broth sterilization is two to four times faster in a
continuous sterilizer than from a fermenter after batch sterilization. The
cooling section of a continuous sterilizer is a true countercurrent design.
Cooling a fermenter after batch sterilization is more similar to a co-current
heat exchanger. Assuming that all modem large scale industrial fermentation
plants sterilize media through a continuous sterilizer, the heat transfer
design of the fermenter is only concerned with the removal of heat caused
by the mechanical agitator (if there is one) and the heat of fermentation.
These data can be obtained while running a full-scale fermenter. The steps
are as follows:
1. Heat Loss by Convection and Radiation
a. u = 1.8 Btu/hr/F/ft2
(No insulation; if tank is insulated determine proper constant.)
b. Calculate tank surface area = A
c. Temp. of Broth = T1
d. Ambient Air Temp. = T2
Ql = UA (T1 – T2) = Btu/hr

Page | 32
Convection and radiation depend upon whether the tanks are
insulated or not, and the ambient air temperature, especially during
the winter. Measurements of convection and radiation heat losses
are, on average, 5% or less of total heat of fermentation (winter and
uninsulated tanks).
2. Heat Loss by Evaporation
a. If fermenters have level indicators, the average evaporation per
hour is easily determined.
b. Calculate pounds of water/hour evaporated from psychometric
charts based on the inlet volume and humidity of air used, and at
the broth temperature. The exhaust air will be saturated. Determine
heat of vaporization from steam tables at the temperature of the
broth = HEV = Btu/lb.
Q2 =HEV x (lb water evap/hr) = Btu/hr
Evaporation depends upon the relative humidity of the compressed
air, temperature of the fermentation broth and the aeration rate. It
is not uncommon that the loss of heat by evaporation is 15 to 25%
of the heat of fermentation. Modem plants first cool the compressed
air then reheat it to 70-80% relative humidity based on summertime
air intake conditions. Consequently, in winter the air temperature
and absolute humidity of raw air are very low and the sterile air
supply will be much lower in relative humidity than summer
conditions. Therefore, in the winter more water is evaporated from
the fermenters than in the summer. (Water can be added to the
fermenter or feeds can be made more dilute to keep the running
volume equal to summer conditions and productivity in summer and
winter equal).
3. Heat Removed by Refrigerant
a. This is determined by cooling the broth as rapidly as possible 5°F
below the normal running temperature and then shutting of fall
cooling. The time interval is then very carefully measured for the
broth to heat up to running temperature (AT and time).
b. Assume specific heat of broth = 1.0 Btu/lb-°F.
c. Volume of broth by level indicator (or best estimate) =gal
Q3 = Sp.Ht. x broth vol. x 8.345 x ΔT ÷ time (hr)
4. Heat Added by Mechanical Agitation
a. Determine or assume motor and gear box efficiency (about 0.92).
b. Measure kW of motor.
Q4 = kW x 3415 x efficiency = Btu/hr
5. Heat of Fermentation = ΔHF
Q1 + Q2 + Q3 - Q4 = ΔHF

Page | 33
The heat of fermentation is not constant during the course of the fermentation.
Peaks occur simultaneously with high metabolic activity. Commercial fermentation
is not constant during the course of the fermentation. Commercial fermentations
with a carbohydrate substrate may have peak loads of 120 Btu/hr/gal. The average
ΔHf for typical commercial fermentations is about 60 Btu/hr/gal. The average loss
of heat due to evaporation from aeration is in the range of 10 to 25 Btu/hr/gal.
Fermentations with a hydrocarbon substrate usually have a much higher ΔHf than
carbohydrate fermentations. Naturally, most companies determine the ΔHf for each
product, especially after each major medium revision. (Typically, data are collected
every eight hours throughout a run to observe the growth phase and production
phase. Three batches can be averaged for a reliable ΔHf.) In this manner, the
production department can give reliable data to the engineering department for
plant expansions.
If mechanical agitation is used and a jacket is desired, then additional internal coils
are required. The internal coils can be vertical, like baffles, or helical. Agitation
experts state that helical coils can be used with radial turbines if the spaces between
the coil loops are 1 to 1.5 pipe diameters. Once helical coils are accepted, Why use a
jacket at all? Reasons in favor of coils (in addition to the better heat transfer
coefficient) are:
1. Should stress corrosion cracking occur (due to chlorides in the cooling
water), the replacement of coils is cheaper than the tank wall and jacket.
2. The cost of a fermenter with helical coils is cheaper than a jacketed tank with
internal coils.
3. Structurally, internal coils present no problems with continuous
sterilization. However, if batch sterilization is insisted upon, vertical coils are
one solution to avoiding the stress between the coil supports and tank wall
created when cooling water enters the coils while the broth and tank wall
are at 120°C. Notice that the method of media sterilization, batch or
continuous, is related to the fermenter design and the capital cost.
2.8 Centrifugation
The solids-liquid separation process can be accomplished by filtration or
centrifugation. Centrifuges magnify the force of gravity to separate phases, solids
from liquids or one liquid from another. There are two general types of centrifuges
1. Sedimentation Centrifuges-where a heavy phase settles out from a lighter
phase, therefore requiring a density difference.
2. Filtering Centrifuges-where the solid phase is retained by a medium like a
filter cloth, for example, that allows the liquid phase to pass through.

Page | 34
Theory
Centrifuges operate on the principle that a mass spinning about a central axis at a
fixed distance is acted upon by a force. The force exerted on any mass is equivalent
to the, weight of the mass times its acceleration rate in the direction of the force.
Figure 2-6 Disk-bowl centrifuge
Figure 2-7 Theory of centrifugation

Page | 35
2.8.1 Biomass Separation (centrifuges) (F-011, F-012)
The fermentation broth from the fermenters is sent to centrifuge (S-1) to separate
the biomass from broth to be recycled to fermenters. The centrifuge S-2 is utilized
to remove the biomass from acid solution before being sent to fermentation.
Sedimentation type disc bowl centrifuges are widely used in industry for this
purpose.
The performance of the sedimentation centrifuges are described by sigma factor (Σ)
which is equal to the cross-sectional area of sedimentation tank giving the same
clarification. the disc type centrifuges proved to be more suitable for this operation.
2.8.2 Yeast sterilization Tank (A-011)
The cell culture should be kept at low pH conditions, to prevent any microbial
contamination in yeast culture during the recycling process. For this purpose, cells
are separated from the fermentation broth by means of continuous centrifugation,
transferred into stirred vessels and sulfuric acid solution is added into vessel to
lower the pH to 2. Approximately 13 g or sulfuric acid is required per kg of ethanol
produced. The cell flow rate is 172 m3/h. The ethanol flow out of the fermenter is
39.4 Mt/h therefore the required sulfuric acid is 512 kg/h. The required acid will
be 694 m3/h. using the residence time of 15 minutes the required vessel volume is
calculated as 190 m3 including 10% safety.
2.8.3 Ethanol Purification
Ethanol Scrubber (S-012)
The ethanol scrubber is utilized to absorb the evaporated ethanol from the carbon
dioxide effluent of the fermentation and top product of beer column. The
environmental regulations limit the emission of volatile organics to atmosphere
with total of 36.4 ton/year. This is why the ethanol scrubber is designed
accordingly.

CHAPTER 3: DISTILLATION AND DEHYDRATION
Page | 36
3 CHAPTER 3: DISTILLATION AND DEHYDRATION
3.1 INTRODUCTION
The separation of liquid mixtures into their various components is one of the major
operations in the process industries, and distillation, the most widely used method
of achieving this end, is the key operation in any oil refinery. In processing, the
demand for purer products, coupled with the need for greater efficiency, has
promoted continued research into the techniques of distillation. In engineering
terms, distillation columns have to be designed with a larger range in capacity than
any other types of processing equipment, with single columns 0.3–10 m in diameter
and 3–75 m in height. Designers are required to achieve the desired product quality
at minimum cost and also to provide constant purity of product even though there
may be variations in feed composition. A distillation unit should be considered
together with its associated control system, and it is often operated in association
with several other separate units. The vertical cylindrical column provides, in a
compact form and with the minimum of ground requirements, a large number of
separate stages of vaporization and condensation. In this chapter the basic
problems of design are considered, and it may be seen that not only the physical and
chemical properties, but also the fluid dynamics inside the unit, determine the
number of stages required and the overall layout of the unit.
The separation of ethanol from a mixture with water, for example, requires only a
simple single unit, and virtually pure products may be obtained. A more complex
arrangement where the columns for the purification of crude styrene formed by the
dehydrogenation of ethyl benzene are. It may be seen that, in this case, several
columns are required and that it is necessary to recycle some of the streams to the
reactor.
In this chapter consideration is given to the theory of the process, methods of
distillation and calculation of the number of stages required for both binary system,
and discussion on design methods is included for plate and packed columns
incorporating a variety of column internals.
Figure 3-1 Distillation unit

Page | 37
3.2 Distillation terminology
To provide a better understanding of the distillation process, the following briefly
explains the terminology most often encountered.
SOLVENT RECOVERY
The term “solvent recovery” often has been a somewhat vague label applied
to the many different ways in which solvents can be reclaimed by industry.
One approach employed in the printing and coatings industries is merely to
take impure solvents containing both soluble and insoluble particles and
evaporate the solvent from the solids. For a duty of this type, APV offers the
Para flash evaporator, a compact unit which combines a Para flow plate heat
exchanger and a small separator. As the solvent laden liquid is recirculated
through the heat exchanger, it is evaporated, and the vapor and liquid are
separated. This will recover a solvent, but it will not separate solvents if two
or more are present.
Another technique is available to handle an air stream that carries solvents.
By chilling the air by means of vent condensers or refrigeration equipment,
the solvents can be removed from the air stream.
Solvents also can be recovered by using extraction, adsorption, absorption
and distillation methods.
SOLVENT EXTRACTION
Essentially a liquid/liquid process where one liquid is used to extract
another from a secondary stream, solvent extraction generally is performed
in a column somewhat similar to a normal distillation column. The primary
difference is that the process involves the mass transfer between two liquids
instead of a liquid and a vapor. During the process, the lighter (i.e., less
dense) liquid is charged to the base of the column and rises through packing
or trays while the denser liquid descends.
Mass transfer occurs and one or more components is extracted from one
stream and passed to the other.
Liquid/liquid extraction sometimes is used when the breaking of an
azeotrope is difficult or impossible by distillation techniques.
CARBON ADSORPTION
The carbon adsorption technique is used primarily to recover solvents from
dilute air or gas streams. In principle, a solvent laden air stream is passed
over activated carbon and the solvent is adsorbed into the carbon bed. When
the bed becomes saturated, steam is used to desorb the solvent and carry it

Page | 38
to a condenser. In such cases as toluene, for example, recovery of the solvent
can be achieved simply by decanting the water/solvent two phase mixture
which forms in the condensate.
Carbon adsorption beds normally are used in pairs so that the air flow can
be diverted to the secondary bed when required.
On occasion, the condensate is in the form of a moderately dilute miscible
mixture. In this case, the solvent must be recovered by distillation. This
would apply especially to water miscible solvents such as acetone.
ABSORPTION
When carbon adsorption cannot be used because certain solvents either
poison the activated carbon bed or create so much heat that the bed can
ignite, absorption offers an alternate technique. Solvent is recovered by
pumping the solvent laden air stream through a column counter currently
to a water stream, which absorbs the solvent. The air from the top of the
column essentially is solvent free, while the dilute water/solvent stream
discharged from the column bottom usually is concentrated in a distillation
column. Absorption also can be applied in cases where an oil rather than
water is used to absorb certain organic solvents from the air stream.
AZEOTROPES
During distillation, some components form an azeotrope at a certain stage of
the fractionation, requiring a third component to break the azeotrope and
achieve a higher percentage of concentration. In the case of ethyl alcohol and
water, for example, a boiling mixture containing less than 96% by weight
ethyl alcohol produces a vapor richer in alcohol than in water and is readily
distilled. At the 96% by weight point, however, the ethyl alcohol composition
in the vapor remains constant (i.e., the same composition as the boiling
liquid). This is known as the azeotrope composition and further
concentration requires use of a process known as azeotropic distillation.
Other common fluid mixtures which for azeotropes are formic acid/water,
isopropyl alcohol/water, and iso butanol/water.
AZEOTROPIC DISTILLATION
In a typical azeotropic distillation procedure, a third component, such as
benzene, isopropyl ether or cyclohexane, is added to an azeotropic mixture,
such as ethyl alcohol/water, to form a ternary azeotrope. Since the ternary
azeotrope is richer in water than the binary ethyl alcohol/water azeotrope,
water is carried over the top of the column. The ternary azeotrope, when
condensed, forms two phases. The organic phase is refluxed to the column
while the aqueous phase is discharged to a third column for recovery of the

Page | 39
entraining agent. Certain azeotropes such as the n-butanol/water mixture
can be separated in a two-column system without the use of a third
component. When condensed and decanted, this type of azeotrope forms
two phases. The organic phase is fed back to the primary column and the
butanol is recovered from the bottom of the still. The aqueous phase,
meanwhile, is charged to the second column with the water being taken from
the column bottom. The vapor streams from the top of both columns are
condensed and the condensates run to a common decanter.
EXTRACTIVE DISTILLATION
This technique is somewhat similar to azeotropic distillation in that it is
designed to perform the same type of task. In azeotropic distillation, the
azeotrope is broken by carrying over a ternary azeotrope at the top of the
column. In extractive distillation, a higher boiling compound is added and
the solvent to be recovered is pulled down the column and removed as the
bottom product. A further distillation step is then required to separate the
solvent from the entraining agent.
STRIPPING
In distillation terminology, stripping refers to the removal of a volatile
component from a less volatile substance. Again, referring to the ethyl
alcohol/water system, stripping is done in the column below the feed point,
where the alcohol enters at about 10% by weight and the resulting liquid
from the column base contains less than 0.02% alcohol by weight. This is
known as the stripping section of the column. This technique does not
increase the concentration of the more volatile component, but rather
decreases its concentration in the less volatile component.
A stripping column also can be used when a liquid such as water
contaminated by toluene cannot be discharged to sewer. For this pure
stripping duty, the toluene is removed within the column, while vapor from
the top is decanted for residual toluene recovery and refluxing of the
aqueous phase.
RECTIFICATION
For rectification or concentration of the more volatile component, the top
section of a column above the feed point is required. By means of a series of
trays and with reflux back to the top of the column, a solvent such as ethyl
alcohol can be concentrated to over 95% by weight.

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