Production of ethanol from various feed stocks involves the following steps. I) Feed preparation 2) fermentation 3) distillation 4) dehydration and 5) denaturing. various organic acids. After fermentation, the liquid is subjected to distillation to separate alcohol from water.

1. ALCOHOL PRODUCTION

2. INTRODUCTION
• Organic compound in which the hydroxy functional
group (-OH) is bound to a carbon atom
• CnH2n+1OH
• Commonly used alcohol is ethanol, C2H5OH

3. PROPERTIES OF ALCOHOL
• Clear, colourless liquid with agreeable odour
• Commonly used to increase octane
• Improve the emissions quality of gasoline
• Their molecular structure includes an (OH), or
hydroxyl radical, which gives them certain
characteristics, high latent heat of vaporization and
solubility in water

4. PROPERTIES OF ALCOHOL
Property Methanol Ethanol Gasoline
Formula CH3OH CH3CH2OH C4-C12
Oxygen, percent by wt. 49.9 34.7 0.0
Density at 20C, Kg/M3 792.0 789.5 702.0
Boiling point, C 64.96 78.32 125.7
Heat of vaporization, KJ/Kg 1101.1 841.5 297.3
Gross heating value, KJ/Kg 22680 29770 47850
Net heating value, KJ/Kg 19930 26750 44380
Heating value of std. stoichiometric mixture, KJ/m3 3253 3528 3540
Stoichiometric air/fuel ratio (mass) 6.46 8.99 14.55
Flammability limits
a. Air/Fuel(percent volume) 6.7-36.5 4.0-13.7 1.4-7.3
b. Air/Fuel(percent mass) 1.6-121.6 2.7-14.0 6.0-22.0
Octane quality
a. Research octane number 110 106 80-95
b. Motor octane number 92 89 70-85
Heat capacity at 25C, J/mol K 81.6 111.5 239.3
Entropy at 25C, J/mol K 126.8 160.7 328.0

5. PROPERTIES OF ALCOHOL
• Gasoline contains no oxygen, alcohols do and less the
oxygen the less volatile the alcohol
• Preferably should be as little as possible
• Methanol : 50% oxygen, only half the heat value of
gasoline
• Ethanol : 35 % oxygen, about 60 % of the heat value of
gasoline
• Higher the alcohol in the series, the lower its oxygen
content and the closer the heat value to that of gasoline

6. PROPERTIES OF ALCOHOL
• Alcohols are pure substances, boiling at one
temperature while gasoline has a high range of
boiling point
• Gasoline requires 15 kg of air per kg of fuel, Ethanol
requires 9 kg of air per kg of fuel
• For a given cylinder volume of gaseous charge
derived from gasoline, 1/15 represents useful heat, for
ethanol – 1/9
• Since, ethanol has a calorific value of 60 % that of
gasoline

7. PROPERTIES OF ALCOHOL
• Internal total energy available from a fuel = final
volume of products of combustion
• Ratio of final to initial volume is 1.057 - gasoline. For
alcohols the value is higher, 1.065 for ethanol and
1.061 for methanol
• Thus alcohols produce a greater number of product
moles per mole of fuel burnt and applying these
correction factors to heat energy/m3, expressed as
percentages, gives the figures 100 for gasoline,98 for
ethanol and 99.5 for methanol

8. ETHANOL PRODUCTION
• Consequent to the petroleum crisis in the year 1973,
international attention was focused on alternate fuel
to automobile vehicles
• Alcohols have higher octane rating which enables
higher compression operation without engine knock
• Ethanol was found as substitute to fossil fuel, which
is depleting

9. ETHANOL PRODUCTION
 It is eco-friendly and renewable fuel
 Domestically produced and renewable energy
 Agro-based industry also helps for improvement of
rural economy
 Import of crude oil can be reduced thereby foreign
exchange outflow will be saved substantially
 It reduces air pollution, cleaner environment due to
cleaner combustion

10. RAW MATERIALS
In general, ethanol can be extracted from every sort of
carbohydrate material (CH2O)N. These are divided into
main groups: sugar, starch and cellulose.
Sugars: Sugarcane, sugar beet, sweet sorghum, cheese
whey, fruits (surplus), confectionary industrial waste
Starch: Grains (maize, wheat, corn), root crops (potato,
cassava)
Cellulose: Wood, agricultural residues (straws, stover),
waste paper, paper pulp, etc

11. RAW MATERIALS

12. ETHANOL PRODUCTION PROCESS

13. ETHANOL PRODUCTION PROCESS

14. ETHANOL FROM SUGAR
Distillation Ethanol
Drying
Co-product
recovery
animal feed
chemicals
Sugar cane process
Ferment-
ation
Sugar Distillation Drying
Ferment-
ation
Sugar
Sugar
cane

15. ETHANOL FROM SUGAR
1. Crushing and concentration of sugar juice from the
sugar crop and its fermentation to ethanol
2. Pretreatment of the crushed residue to increase its
susceptibility to enzyme attack and then its
enzymatic saccharification to ethanol
3. Conversion of molasses - the dark viscous residual
syrup left after crystallization of sucrose from sugar
crop to ethanol

16. ETHANOL FROM SUGAR
• Sugars already available in degradable form
• The main reaction involved is fermentation
• This is usually done using molasses
• Molasses is a thick dark syrup produced by boiling
down juice from sugarcane; specially during sugar
refining
C6H12O6
sugar (glucose)
yeast
2 C2H5OH
ethanol
+ 2 CO2
carbon dioxide

17. ETHANOL FROM MOLASSES AND JUICE
MASH
JUICE FOR SUGAR
FACTORY
SUGAR
ETHANOL
FROM
SUGARS
SUGARCANE
MILLING
FERMENTATION
DISTILLATION
MOLASSES
ETHANOL
FROM
MOLASSES
ETHANOL
Sugars = Suc + Glu + Fru
JUICE FOR ETHANOL
DISTILLERY

18. ETHANOL FROM MOLASSES
• Molasses is first diluted to 14-18% sugar
concentration and then acidified with sulphuric acid
to form a mash
• Yeast culture (Saccharomyces cerevisiae) is added to
the mash until 3-5% yeast concentration is obtained
• Yeast contains the enzymes invertase and zymase

19. ETHANOL FROM MOLASSES
• Invertase catalyses the hydrolysis of sucrose in the
mash to invert sugar
Invertase
C12H22O11 + H2O ---------> C6H12O6 + C6H12O6
Glucose Fructose
• Invert sugars are subsequently converted into about
equal parts of ethanol and carbon dioxide by action of
zymase
Zymase
C6H12O6 ----------------> 2CH3CH2OH +2CO2
Invert sugar Ethanol
• Fermentation efficiency - 95% sugar

20. ETHANOL FROM MOLASSES

21. PRODUCT ETHANOL
• Ethanol produced has strength not exceeding 95%
• It can be dehydrated to ethanol containing less than
0.1% water
• This dehydration is achieved by using solid or liquid
drying agents and/or azeotropic methods
• Trichloroethylene, benzene etc can be used as
dehydration agents with azeotropic distillation to
produce 100% ethanol from 'mash’

22. PRODUCT ETHANOL
• Estimated availability of cane 'molasses' in India is of
the order of 2 million tonnes annually
• An average yield of 280-300 litres of 95% ethanol
can be obtained per tonne of molasses

23. MICROORGANISM AND CULTURE
CONDITION
• The strain of yeast used is Saccharomyces
cerevisiae
• Isolates are maintained on slants of malt-extract
agar composed of malt extract, dextrose peptone
and agar
• The slants are incubated at 37C for 48 hours, then
stored at 4C

24. PREPARATION OF YEAST INOCULUM
• To initiate yeast growth, inocula from 3 day old slants
are transferred to a flask containing 50 ml of a
medium composed of (g/litre) glucose 10, peptone 5,
yeast extract 3, malt extract 3
• The flasks are incubated at 30±2C for 48 hours on a
rotary shaker 200-250 rpm
• Standard inocula (2 ml each) from such liquid
cultures are used to inoculate 100 ml of the
fermentation medium

25. Raw material
Blackstrap molasses containing 48 to 55% sugar after
recovery of crystalline sugar from sugarcane juice, is the
principal source of industrial alcohol
CONCENTRATION OF SUGAR
A sugar concentration of 10 to 18% is usually
satisfactory. Four parts of water by weight would be
added to one part of molasses containing 60% sugar, by
weight to reduce the sugar concentration to
approximately 12%

26. NUTRIENTS
Although molasses contain most of the nutrients
required for fermentation, ammonium sulphate or
phosphates may be added to the mash to supply
deficiencies in nitrogen and phosphorous
pH OF THE MASH
Fermentation proceeds satisfactorily when the
mash has been adjusted to a pH value of 4 to 4.5.
Though sulphuric acid is commonly used to adjust the
pH of mash, lactic acid is preferable

27. OXYGEN TENSION
Oxygen is necessary at the early stages for optimum
reproduction of yeast cells, but, it is not required for the
production of alcohol. During fermentation, CO2 is
evolved and anaerobic conditions are soon established.
Mash is at a temperature of 21 to 26C
TIME FOR FERMENTATION
Fermentation is usually complete in 50 hrs or less
depending on the temperature, sugar concentration and
other factors

28. TYPICAL SUGAR ETHANOL PLANT IN
BRAZIL
Bagasse
Sugar cane field
Distillery Sugar plant
Ethanol storage
tanks

29. ETHANOL FROM SUGAR CROPS
Ethanol yield from sugar crop juice (Basis: 1000 kg of crop
biomass)
Sugar crop Total fermentable
solids (Kg)
Ethanol yield
(Kg)
Sugarcane 112.0 54.3
Sweet sorghum
including starch
96.0 46.0
Sugar-beet 66.7 32.0

30. ETHANOL FROM STARCH
1. Milling to free the starchy material from grain
kernals
2. Dilution
3. Cooking to dissolve and gelatinize the starch
4. Conversion of starch to fermentable sugars by
malting, enzymes or acid hydrolysis in addition to the
steps of fermentation and distillation

31. STARCH BASED FEEDSTOCKS FOR
ETHANOL PRODUCTION
Feedstock Starch (%)
Corn 60-68
Sorghum 75-80
Rye 60-63
Cassava 25-30
Rice 70-72
Barley 55-65
Potato 10-25

32. ETHANOL FROM STARCH
Distillation Ethanol
Drying
Co-product
recovery
animal feed
chemicals
Corn process
Ferment-
ation
Sugar
Corn
kernels
Starch
conversion
(cook or
enzymatic
hydrolysis)
Sugar cane process
Sugar
cane

33. MILLING OF STARCH FEEDSTOCK
Wet milling
• The process of separating the corn kernel into starch,
protein, germ and fiber in an aqueous medium prior
to fermentation
• The primary products starch and starch-derived
products (high fructose corn syrup and ethanol) corn
oil and corn gluten)

34. MILLING OF STARCH FEEDSTOCK

35. MILLING OF STARCH FEEDSTOCK
Dry milling
• The entire corn kernel is first ground into flour and
the starch in the flour is converted to ethanol via
fermentation
• Other than ethanol, carbon dioxide - carbonated
beverage industry distillers dried grain with solubles
(DDGS) - animal feed
Malting
• Steep the corn in water, start germination, stop
germination at a particular by drying to stop further
growth

36. MILLING OF STARCH FEEDSTOCK

37. MILLING OF STARCH FEEDSTOCK
0
10,000
20,000
30,000
40,000
50,000
60,000
70,000
Btu/Gallon
Wet Mill Dry Mill
1980s
2000s

38. ETHANOL FROM STARCH
• Steamed for 1 or 2 hours at 2 to 3 atmospheric
pressure to gelatinize the starch present
• In the case of potato, the resultant pulp is cooled to
about 50C and an equal volume of water and 10%
malt is added
• In the case of grain as raw material, an enzyme
known as amylase is used (amylase is produced from
the growth of mold on a small quantity of grain)
• Amylase converts the starch in the grain pulp into
sugar

40. ETHANOL FROM STARCH
• When ethanol has reached its optimum percentage
corresponding to 50% conversion of the starch, the
'mash' is distilled, so that ethanol water mixture is
separated from the 'mash' residue
• The ethanol water mixture is sent through additional
distillation columns where ethanol concentration is
increased to 95 per cent ethanol

41. ETHANOL FROM STARCH
• 1 tonne of potato yields around 100 litres of ethanol
• 10 bushes of corn yield around 117 litres of ethanol
• Starches are polymers of anhydroglucose, linked by
alphaglucosidic bonds
• They contain two types of polymers, amylose and
amylopectin
• There are two methods for hydrolyzing starch - the
enzymatic hydrolysis and the acid hydrolysis

42. ENZYMATIC HYDROLYSIS
• Two main groups of enzymes are involved in the
enzymatic degradation of starch
• The first amylase consists of enzymes which split the
(1-4) bond between glucose residues
• This group can be further classified into endo - enzymes
which produce random or internal breaks exo-enzymes
which act from chain ends
• The second group of enzymes catalyzes the specific
hydrolysis of (1-6) interchain linkages of amylopectin
using the enzyme amyloglucosidase [(1,4) (1,6)
(1,6)]

43. ACID HYDROLYSIS OF STARCH
• In acid hydrolysis, the breakdown of starch to glucose
is accompanied by further degradation of the sugar to
5-hydroxymethyl furfural, levulinic acid and formic
acid
• Acid concentration and type, temperature and starch
concentration have been shown to be key factors in the
relative yields
• Although acid hydrolysis of starch has been shown,
the procedure is not recommended because of low
alcohol yields (approximately 75% of theoretical) due
to presence of non-fermentable and inhibitory by
products

44. ETHANOL FROM STARCH

45. ETHANOL FROM CELLULOSE
Distillation Ethanol
Drying
Co-product
recovery
animal feed
chemicals
Cellulose
conversion
hydrolysis
Cellulose
pretreatment
Cellulose
•Crop residues: corn stover, rice straw, wheat straw, etc.
•Forestry residues/slash
•Energy crops: switchgrass, poplar, Miscanthus, many others
•Municipal & construction wastes, etc
Ferment-
ation
Sugar
Sugar
cane
Corn
kernels
Starch
conversion
(cook or
enzymatic
hydrolysis)
Distillation Drying
Sugar cane process
Corn process
Cellulose process
Ferment-
ation
Sugar

46. ETHANOL FROM CELLULOSE
Distillation Ethanol
Drying
Co-product
recovery
animal feed
chemicals
Sugar cane process
Cellulose
Conversion
Hydrolysis
Corn process
Cellulose process
Thermochemical
conversion
• Heat and Power
• Fuels and Chemicals
Cellulose
Pretreatment
Cellulose
•Corn stover
•Switch grass
•MSW
•Forest residues
•Agro residues
•Wood chips
Ferment-
ation
Sugar
Sugar
cane
Starch
Conversion
(Cook or
Enzymatic
Hydrolysis)
Cellulose
conversion
hydrolysis
• Heat and power
• Fuels and chemicals
Cellulose
pretreatment
Cellulose
Corn
kernels
Starch
conversion
(cook or
enzymatic
hydrolysis)

47. ETHANOL FROM CELLULOSE
• The three main components present generally in plant
cell are cellulose, hemicellulose and lignin. They are
present in the ratio 4:3:3 respectively
• Vegetable waste, tropical grass, straw etc is chopped to a
convenient size in chopping machine
• Chopping are soaked in dilute sulphuric acid and kept at
a certain temperature. After the optimum time of
soaking and agitation the steeped material is passed
through rollers to remove the excess acid
• The residual mass is steamed for a couple of hours to
convert the insoluble hemicellulose into fermentable
sugar

48. PRE-TREATMENT FOR CELLULOSIC
ETHANOL
• Methods by which one could increase the surface area
of cellulose to allow free access of the degradation
would also enhance susceptibility of this polymer to
hydrolysis
• Number of physical or chemical methods which serve
to separate cellulose from its protective sheath of
lignin and increase the surface area of the cellulose
crystallite by size reduction and swelling process

49. PHYSICAL METHODS OF PRETREATMENT
Milling
• Hammer mill, ball mill and compression mill
• Produces size reduction thereby increases surface
area
Steam explosion
• Steam heating of green wood chips to approximately
180-200C for 5-30 min. in a continuous operation or
at higher temperatures 245C for a shorter time (0.5 -
2 min) in the batch mode

50. CHEMICAL METHODS OF PRE-TREATMENT
Solvents
• With the use of appropriate solvents - remove either
lignin or cellulose from the native matrix
• Not only serves to dissociate cellulose from its
protective lignin covering but also destroys the
crystalline structure of native cellulose by successive
dissolution and regeneration to a highly active form
• Cadoxen an aqueous alkaline solution of ethylene
diamine and cadmium oxide

51. CHEMICAL METHODS OF PRETREATMENT
Swelling agents
• Pretreatment agents have been studied for their ability
to swell the cellulose matrix and thus open the interior
of the fibril to easy attack by enzymes
• Concentrated NaOH, organic bases (amines) and
certain metal salts such as SnCl4
• Drawback - the treated product is at a very low bulk
density and as such, suspensions of 4-5% are too thick
to agitate or transport

52. MISCELLANEOUS METHODS OF
PRETREATMENT
Pulping
• Delignification process is done utilizing pressurized SO2
gas cooking for 2-3 hrs at 120C with this pretreatment,
subsequent hydrolysis has been found to reach nearly
100% for hardwoods and slightly less for soft wood
Heat
• On heating cellulose at 200C for 3 hrs in a non-polar
liquid, greatly enhanced the rate of subsequent rate of
acid hydrolysis
Freezing
• It is shown that repeated freezing and thawing cycles of
cellulose in water suspensions (dropping to - 75C)

53. MISCELLANEOUS METHODS OF
PRETREATMENT
High energy irradiation
• Electron irradiation at levels greater than 106 rad have
been found to enhance the rate of hydrolysis and
maximum yield of free sugar when cellulosic materials
had been exposed.
Lignin-consuming microbes
• There are a number of microorganisms which produce
enzymes required for lignin degradation
Fungi Bacteria
Paecilomyces sp. Nacardia sp.
Allescheria sp. Streptomyces sp.
Presussia sp. Pseudomonas sp.
Chaetomium sp. Flavabacterium sp.
Poria sp.

54. ACID HYDROLYSIS
• Breaking down of the glycosidic bonds in cellulose
and hemicellulose
• Sugars made after acid hydrolysis get converted into
furfural in the acidic medium which can act as
fermentation inhibitors
• Reaction should be rapid
• Sugars should be rapidly removed

55. CONCENTRATED ACID HYDROLYSIS
• Crystalline cellulose is completely soluble in 72%
H2SO4 or 42% HCl solutions at relatively low
temperatures (10-45C)
• Done in one reaction chamber
• Provides a complete and rapid conversion of cellulose
and hemicellulose to C6 and C5 sugars
• Advantages
Optimize sugar recovery
 Cost effectively recover the acid for recycling

56. CONCENTRATED ACID HYDROLYSIS
• The main drawback in the use of concentrated acids is
that the acid must be recovered and recycled
economically
• Additional expenses arise due to requirement for
corrosive resistant vessels

57. DILUTE ACID HYDROLYSIS
• Using 2% H2SO4 at 190C for a period of 20 min
• Two reaction chambers
Chamber1- hydrolysis of hemicellulose (mild
conditions)
Chamber2- hydrolysis of cellulose (harsh
conditions)
 High temperatures and pressures
• Disadvantages – low sugar yield, high energy
consumption due to hydrolysis at elevated
temperatures and pressures - the need for corrosion
resistant materials

58. ENZYMATIC HYDROLYSIS
• Bacteria and fungi are used as sources of cellulases,
hemicellulases that could be used for the hydrolysis of
pretreated lignocelulosics
• The cellulose complex is found to consist of three
basic components which may be present in multiple
forms, often as isoenzymes
• Endo-(1,4) glucanases
• Exo- glucanases
• (1-4) glucosidase
• There are two technological developments
Enzymatic conversion
Direct microbial conversion (DMC)

59. CELLULOSE DEGRADING MICROBES
Fungi (mesophilic) Trichoderma reesei
T.koningii
T.Lignorium
Penicillium funiculosum
P.Variable
P.iriensis
Aspergillus wentii
A.Niger
A.Foetidas
Fungi (Thermophilic) Chaetomium thermophile
Humicola sp.
Sporotrichum thermophile
Thermoascus aurantiacus
Talaromyces emersonii
Bacteria (mesophilic) Cellvibrio Fulvus
C.gilvus
C.Vulgarus
Pseudomonas fluorescens
Acetovibrio cellulolyticus
Streptomyces flavogrisens
Ruminococcus sp.
Cellulomonas sp.
Bacteria (thermophilic) Clostridium thermocellum
Actinomycetes (mesophilic) Streptomyces sp.
Actinomycetes (Thermophilic) Thermomonospora sp
Thermo actinomycete sp.

60. ENZYMATIC CONVERSION
• The enzymes are extracted from microorganisms and
are modified genetically to increase efficiencies
• For enzymes to work efficiently, they must obtain
access to the molecules to be hydrolyzed
• This further asserts the necessity of pretreatment
process to remove crystalline structure of cellulose to
expose the molecules to the microorganisms

61. DIRECT MICROBIAL CONVERSION
• A single microorganism does both hydrolysis and
fermentation
Advantage
• Cellulose enzyme production or purchase is a
significant cost in enzymatic hydrolysis under
development. With DMC, a dedicated step for
production of cellulase enzyme is not necessary
• Disadvantage
• Currently available microbes cannot do both
processes at the required efficiencies

62. FERMENTATION
• Fermentation is a biochemical process in which
enzymes produced by microorganisms transform an
organic substance (substrate) into ethanol
• Substrate - six-carbon sugar
• Microorganisms - yeasts, molds or bacteria - contain
no chlorophyll - can not produce their own food
through photosynthesis.
• Rather, they produce enzymes that act as catalysis to
convert carbohydrates from organic material into
energy

63. TYPES OF FERMENTATION
• Batch fermentation
• Continuous fermentation

64. BATCH FERMENTATION
• The sugar solution supplemented with yeast nutrients is
added to the fermenter and fermenter is inoculated with a
rapidly growing culture of yeast from the seed tank
• Usually the time required to completely utilize the
substrate is 36-48 hrs
• The over all productivity from this process is about 1.8 -
2.5 kg of ethanol produced per M3 fermenter volume per
hr
• After completion of fermentation the cells are removed
from the broth medium before distillation

65. BATCH FERMENTATION
Advantages
• Control of microbial contaminants
• Control of ethanol quality per batch
Disadvantages
• High capital requirement for large scale production
because of the number of fermenters required
• Decrease in volumetric efficiency of fermenters,
based on time used
• Possible variations from batch to batch, requiring
homogenization

66. CONTINUOUS FERMENTATION
•Sugars and nutrient mediums are continuously added to
the reactor
•Reaction proceeds progressively as the beer rises, but
yeast tends to settle back and be retained
•High cell densities of 50 to 80 g/h are achieved with
out an auxiliary mechanical separator
•Residence times of below 4 hrs have been possible
with sugar concentration upto 12% sucrose giving 90%
conversion of ethanol
•This process is called continuous tower process

67. CONTINUOUS FERMENTATION
Advantages
• High volumetric efficiency
• Yeast recycling
• Establishment of a flow growth-rate equilibrium
• A more consistent product than can be obtained from
batch fermentation
• Lower capital and labour cost
• Reduced time requirements
Disadvantages
• High potential for serious microbial contamination
• Inspite of providing a more consistent product,
homogenization is still required

68. DISTILLATION
• Distillation is a separation process of two or more
liquids in solution that is based on their relative
volatilities and take advantage of this different boiling
temperatures
• The process takes place in a column and two heat
exchangers
• In the column two phases, liquid and gas, are
distributed to enrich the vapour in more volatile
compounds and enrich the liquid phase on less volatile
compounds
• Mass transfer is the key to a successful distillation

69. DISTILLATION

70. TYPES OF DISTILLATION
• Continuous distillation
• Batch distillation
• Semi-batch distillation

71. CONTINUOUS DISTILLATION
• The mixture which is to be
separated is fed to column at one
or more points
• Liquid mixture runs down the
column while vapour goes up
• Vapour is produced by partial
vaporisation of the mixture
which is heated in reboiler
• Then vapour is partially
condensed to earn back the less
volatile compounds to the
column to separate as bottom
product (reflux)

72. BATCH DISTILLATION
• The oldest operation used
for separation of liquid
mixtures
• Feed is fed from bottom,
where includes reboiler, to
be processed
• Numbers of accumulator
tanks are connected to
collect the main and the
intermediate distillate
fractions

73. SEMI-BATCH DISTILLATION
• Semi batch distillation is
very similar to batch
distillation
• Feed is introduced to
column in a continuous or
semicontinous mode
• It is suitable for
extractive and reactive
distillations

74. DISTILLATION EQUIPMENT DESIGN
• Plate columns (Tray columns)
• Packed beds

75. PLATE COLUMNS (TRAY COLUMNS)
• It is the most widely used kind of distillation column
• Trays are shaped to maximize the liquid-vapour
contact and increase the mass transfer area
• Tray types include sieve, valve and bubble cap

76. PLATE COLUMNS (TRAY COLUMNS)

77. PLATE COLUMNS (TRAY COLUMNS)
Advantages
• Least expensive column for
diameters greater than 0.6 m
• The liquid-vapour contact in
the cross-flow of plate
columns is more effective
than counter-current flow in
packed columns
• Cooling coils can be easily
added to the plate column
• Can handle high liquid flow
rates
Disadvantages
• Higher pressure drops than
packed columns
• Foaming can occur because
the liquid is agitated by the
vapour flowing up through it

78. PACKED BEDS
• Packing can be provided either as dumped or stacked
• Dumped packing constitutes of bulk inert materials
• Stacked packing is includes meshwork which has the
same diameter with the column
• Important criteria for packing are efficient contact
(liquid-vapour), resistance to flow, flow capacity,
resistance of packing against corrosion

79. PACKED BEDS

80. PACKED BEDS
Advantages
• When the diameter is less than
0.6m it is less expensive than
the plate column
• Packing is able to handle
corrosive materials
• Lower pressure drop than in
plate columns.
• Good for thermally sensitive
liquids
Disadvantages
• Can break during installation or
due to thermal expansion
• Not cost efficient for high liquid
flow rates
• Contact efficiencies are
decreased when the liquid flow
rate is too low

81. AZEOTROPIC DISTILLATION
• Initially the separation of ethanol – water is increasingly
difficult
• Azeotrope - the concentration at which the ethanol and
water vapourize at the same temperature
• The azeotropic mixture has 95.57 wt% ethanol and a
minimal boiling point of 78.15C
• Boiling at this point gives a vapour of the same
composition as the boiling liquid and no further
concentration of ethanol can be achieved by simple
distillation
• Lowering of distillation pressure pushes the azeotropic

82. AZEOTROPIC DISTILLATION
• Another method of breaking the azeotrope is addition
of an extraneous liquid influencing the vapour liquid
equilibrium so that pure alcohol may be produced
• If the extraneous material is less volatile than the
feed, it is called a solvent and the operation is called
extractive distillation
• When the extraneous material is more volatile than
the feed it is withdrawn with the overhead product
and the operation is called azeotropic distillation

83. ANHYDROUS ALCOHOL
• 99.5 - 99.9% alcohol (ethanol) is popular to be fuel
for cars
• Azeotropic alcohol is preheated and fed into the
dehydrating column where it is contacted with
dehydrating salt brine flowing downwards.
• Water free ethanol leaves the column at the top. The
water solution is collected at the bottom and salt
separated in another small distillation column

84. ANHYDROUS ALCOHOL
• In extractive distillation method, hygroscopic liquids,
such as glycerin and ethylene glycol have been
employed
• The near azeotropic alcohol is introduced at an
intermediate tray of the ethanol dehydration tower
and glycerin fed in near its top
• Anhydrous ethanol is drawn-off as the overhead
products where as, the glycerine with picked up water
leaves at the bottom of the tower

85. ANHYDROUS ETHANOL PRODUCTION PROCESS

86. VACUUM DISTILLATION
• As the pressure over ethanol water is decreased the
composition of the corresponding azeotrope shifts
towards purer ethanol, until it disappears at 9.3 kPa
entirely and pure ethanol can be obtained.
• The 'one-step' distillation is uneconomical; the lower the
tower pressure, the larger its diameter must become and
the energy requirement is also very high.
• However a two-step distillation can be used where as
atmospheric concentration removes the bulk of water
followed by a second still operating under vacuum.
• The advantage of this system is that since ethanol - water
mixture boils at lower temperature under vacuum, lower

87. BY PRODUCTS IN ETHANOL
FERMENTATION
Waste Biomass
• 10% substrate feed with 95% conversion to alcohol
will yield 5.0 g/L of dried cell mass
Stillage
• Stillage is the waste water produced after ethanol has
been removed by distillation from a fermented mash
Fusel Oil
• Fusel oil is the mixture of volatile, pungent-tasting
alcohol produced during alcoholic fermentation
Carbon dioxide
• For every cubic meter of ethanol formed about 760 kg
of CO2 is liberated from the fermentation system.

88. ETHANOL YIELDS
Boyle, Renewable Energy, Oxford University Press (2004)

89. ETHANOL PRODUCTION

90. COUNTRIES IN ETHANOL PRODUCTION

91. BRAZIL
• World leader in production and export of ethanol
• Ethanol produced per day equivalent to 200,000
barrels of gasoline
• 24% blend ethanol mandatory Competitiveness

92. USA
• Ethanol : a big boost to economy
• E85 sells cheaper than gasoline
• Currently production aimed at 4.5 Billion gallons/yr

93. SIGNIFICANT OTHER COUNTRIES
• China: 3rd largest producer of ethanol producing
220,000 tons of ethanol, exporting 90,000 tons in
2000
• Malaysia and Indonesia are starting pilot-scale
production from palm oil

94. INDIA
• Sources of ethanol
• Sugarcane
• Molasses
• Agricultural waste
• Low average cost of Rs.18/litre projected
• Annual production capacity of 1.5 Billion litres

95. ECONOMICS OF ETHANOL
PRODUCTION FROM MOLASSES
• The cost of molasses in India varies widely across
different states
• In past years it has been as low as Rs. 50/ton and as high
as Rs. 2,000/ton
• A sizeable part of the cost is central excise duty, sales
tax, transportation cost, etc and the statutory controlled
sugarcane and sugar prices
• The international price of molasses, which was $50/ton,
has doubled to $100/ton. Assuming a molasses price of
Rs 3,000/ton and a yield of 220 litres of ethanol per ton,
the feedstock cost would be Rs. 13.64/litre ethanol

96. Title