PRODUCTION OF ETHYL ALCOHOL FROM MOLASSES USING ASPEN PLUS

A project report submitted in partial fulfillment for the award of degree of

BACHELOR OF TECHNOLOGY

IN

CHEMICAL ENGINEERING

SUBMITTED BY

T.P.RL.SINDHURI K.SURESH KUMAR

B.JOGENDRA KUMAR R.S.RAVI KISHORE

Under the Esteemed guidance of

Dr.ADITYA MUKHARJEE, PhD

PROFESSOR

Department of Chemical Engineering

Gayatri Vidya Parishad College of Engineering

(Affiliated to Jawaharlal Nehru Technological University, Kakinada, A.P.)

Madhurawada, Visakhapatnam – 530048

2007-2011

GAYATRI VIDYA PARISHAD COLLEGE OF ENGINEERING

DEPARTMENT OF CHEMICAL ENGINEERING

CERTIFICATE

This is to certify that the project work titled “PRODUCTION OF ETHYL ALCOHOL FROM

MOLASSES USING ASPEN PLUS” During the academic year (2010-2011) under the guidance of

Dr.ADITYA MUKHARJEE,PhD, professor is submitted in partial fulfillment for the award of

degree of Bachelor of Technology in Chemical Engineering.

Dr.ADITYA MUKHARJEE, PhD, Dr.B.Srinivas, M.Tech, PhD,

Professor, Head of the Department,

ACKNOWLEDGEMENT

It is our privilege to express our gratitude to our project guide Dr.Aditya Mukharjee, Professor, Department of Chemical Engineering, G.V.P. College of Engineering for his incessant co-operation and suggestions towards the completion of the technical report.

Heartfelt thanks to Prof. B.Srinivas, HOD and support provided by the all the faculty members of the department is greatly acknowledged.

T.P.R.L.Sindhuri

K.Suresh Kumar

Jogendra Behara

R.S.Ravi Kishore

INDEX

1. INTRODUCTION

2. DESCRIPTION

(I)BLOCK DIAGRAM

(II)RAW MATERIALS

(III)REACTION INVOLVED

(IV)PROCESS

(V)MATERIAL BALANCE

3. SIMULATION

(I)DESIGN

(II) ASSUMPTIONS

(III) DATA SUPPLIED

(IV) RESULTS

1. CONCLUSION

ABSTRACT

This project mainly deals with the production of “Ethyl alcohol” from

molasses using ASPEN Plus software where the entire process can be

simulated just by using it. Our aim is to produce 10tonne of ethanol/day

which is of 95% concentrated and this would help to know the conditions

that has to be applied practically and various conditions under which the

productivity could be increased and also to find many ways for troubleshoot

of many practical problems and how to decrease the adverse affects that are

encountered during the production process as ethanol is parental compound

for many processes. With actual operating conditions and reliable

thermodynamic data we could simulate actual plant behavior. Ethyl Alcohol

from molasses is the most familiar process industrially as it is very

economical because the raw materials used for this process are by-products

of sugar manufacturing process; hence they are cheaper and could be

handled easily. Moreover when compared to the other processes of ethanol

production like from starch etc., needs the raw materials to be pre-treated

like hydrolyzed to fermentable sugars by the action of malts and molds

before the process starts. But here, sugar can be directly converted into

ethanol. This project mainly with deals how to make this process more

effective and the results show the nearer values to the practical values that

are to be adopted in the plant.

INTRODUCTION

Ethanol or ethyl alcohol, CH3CH2OH, has been described as one of the

most exotic synthetic oxygen-containing organic chemicals because of its

unique combination of properties as a solvent, a germicide, a beverage, an

antifreeze, a fuel, a depressant, and especially because of its versatility as a

chemical intermediate for other organic chemicals. Ethanol is one of the

most important renewable fuels contributing to the reduction of negative

environmental impacts generated by the worldwide utilization of fossil

Fuels. However, the production of ethanol is a complicated process. The

transformation of such biological resources as energy-rich crops (like sugar

cane or corn) or lignocellulosic biomass requires the conditioning or

pretreatment of the feed stocks for fermenting organisms to convert them

into ethanol. Then, aqueous solutions of ethanol should be concentrated for

obtaining hydrous ethanol. This product has to be dehydrated in order to be

utilized as an oxygenate for gasoline, the trade form in which ethanol is

mostly employed in the transportation sector. The complexity of this process

partly explains why fuel ethanol has not played a leading role in comparison

to cheaper oil derived fuels. There are various processes in which ethanol

could be produced. But the major process in which it is produced

industrially is using molasses. This process is more economical when

compared to all other process as here ethanol is produced from the by-

product of sugar industry. Ethanol is made from a variety of agricultural

products such as grain, molasses, fruit, whey and sulfite waste liquor.

Generally, most of the agricultural products mentioned above command

higher prices as foods, and others, e.g., potatoes, are uneconomical because

of their low ethanol yield have generated renewed interest in ethanol

fermentation, but its use still depends on the availability and cost of the

carbohydrate relative to the availability and cost of ethylene. Sugar and grain

prices, like oil prices, have risen dramatically since 1973. According to the

results that are obtained from the world’s utilization of ethanol records,

maximum ethanol used will be from molasses.

RAW MATERIAL(1 TON) ETHANOL YIELD(LITERS)

MOLASSES

SUGAR CANE

FRESH CASSAVA

SORGHUM

COCONUT JUICE

260

70

180

70

83

PHYSICAL PROPERTIES OF ETHANOL:

Ethanol is a volatile, colorless liquid that has a slight odor. It burns with a

smokeless blue flame that is not always visible in normal light. The

physical properties of ethanol stem primarily from the presence of

its hydroxyl group and the shortness of its carbon chain. 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. Ethanol is a versatile solvent, miscible with

water and with many organic solvents, including acetic acid,

acetone, benzene, carbontetrachloride, chloroform, diethyl ether, ethylene

glycol, glycerol, nitromethane, pyridine, and toluene. It is also miscible

with light aliphatic hydrocarbons, such as  pentane and hexane, and with

aliphatic chlorides such as trichloroethane and tetrachloroethylene.

Ethanol’s miscibility with water contrasts with that of longer-chain

alcohols (five or more carbon atoms), whose water miscibility decreases

sharply as the number of carbons increases. The miscibility of ethanol

with alkanes is limited to alkanes up to undecane, mixtures

with dodecane and higher alkanes show a miscibility gap below a certain

temperature (about 13 °C for dodecane). The miscibility gap tends to get

wider with higher alkanes and the temperature for complete miscibility

increases. Ethanol-water mixtures have less volume than the sum of their

individual components at the given fractions. Mixing equal volumes of

ethanol and water results in only 1.92 volumes of mixture. Mixing

ethanol and water is exothermic. At 298 K, up to 777 J/mol are set free

Mixtures of ethanol and water form an azeotrope at about 89 mole-%

ethanol and 11 mole-% water or a mixture of about 96 volume percent

ethanol and 4% water at normal pressure and T = 351 K. This azeotropic

composition is strongly temperature and pressure-dependent and vanishes

at temperatures below 303 K.

The graph shows the heat of mixing of mixture of ethanol and water. And

the graph which is drawn below gives the equilibrium curve of the

mixture of ethanol and water (including azeotrope).

FERMENTATION:

DEFINITION: In general there are 2 definitions for fermentation

(a) The anaerobic conversion of sugar to carbon dioxide and alcohol by yeast.

(b) Any of a group of chemical reactions induced by living or nonliving

ferments that split complex organic compounds into relatively simple

substances. Fermentation in food processing typically is the conversion

of carbohydrates to alcohols and carbon dioxide or organic acids

using yeasts, bacteria, or a combination thereof, under anaerobic conditions.

A more restricted definition of fermentation is the chemical conversion

of sugars into ethanol. The science of fermentation is known as zymurgy.

Fermentation usually implies that the action of microorganisms is desirable,

and the process is used to produce alcoholic beverages such as wine, beer,

and cider. Fermentation is also employed in the leavening of bread, and for

preservation techniques to create lactic acid in sour foods such

sauerkraut, dry sausages,kimchi and yogurt, or vinegar (acetic acid) for use

in pickling foods. Fermentation processes from any material that contains

sugar can derive ethanol. The many and varied raw materials used in the

manufacture of ethanol via fermentation are conveniently classified under

three types of agricultural raw materials: sugar, starches, and cellulose

materials. Sugars (from sugar cane, sugar beets, molasses, and fruits) can be

converted to ethanol directly. Starches (from grains, potatoes, root crops)

must first be hydrolyzed to fermentable sugars by the action of enzymes

from malt or molds. Cellulose from wood, agricultural residues, waste

sulfite liquor from pulp and paper mills) must likewise be converted to

sugars, generally by the action of mineral acids. Once simple sugars are

formed, enzymes from yeast can readily ferment them to ethanol.

USES OF ETHANOL:

Ethanol is the parent compound for many products that we use daily. Some

of its uses are as follows.

AS A FUEL:

The largest single use of ethanol is as a motor fuel and fuel additive.

Brazil has the largest national fuel ethanol industry. Gasoline sold in Brazil

contains at least 25% anhydrous ethanol. Hydrous ethanol (about 95%

ethanol and 5% water) can be used as fuel in more than 90% of new cars

sold in the country. Brazilian ethanol is produced from sugar cane and noted

for high carbon sequestration. The U.S. uses Gasohol (max 10% ethanol)

and E85 (85% ethanol) ethanol/gasoline mixture. Ethanol may also be

utilized as a rocket fuel, and is currently in light weight rocket-powered

racing aircraft.

ALCOHOLIC BEVERAGES:

Ethanol is the principal psychoactive constituent in alcoholic beverages,

with depressant effects on the central nervous system. It has a complex mode

of action and affects multiple systems in the brain, the most notable one

being its agonistic action on the GABA receptors. Similar psycho actives

include those that also interact with GABA receptors, such as gamma-

hydroxybutyric acid (GHB).  Ethanol is metabolized by the body as an

energy-providing nutrient, as it metabolizes into acetyl CoA, an intermediate

common with glucose and fatty acid metabolism that can be used for energy

in the citric acid cycle or for biosynthesis. Alcoholic beverages vary

considerably in ethanol content and in foodstuffs they are produced from.

Most alcoholic beverages can be broadly classified as fermented beverages,

beverages made by the action of yeast on sugary foodstuffs, or distilled

beverages, beverages whose preparation involves concentrating the ethanol

in fermented beverages by distillation. The ethanol content of a beverage is

usually measured in terms of the volume fraction of ethanol in the beverage,

expressed either as a percentage or in alcoholic proof units.

FEED STOCK:

Ethanol is an important industrial ingredient and has widespread use as a

base chemical for other organic compounds. These include ethyl halides,

ethyl esters, diethyl ether, acetic acid, ethyl amines, and to a lesser

extent butadiene.

ANTISEPTIC:

Ethanol is used in medical wipes and in most common antibacterial hand

sanitizer gels at a concentration of about 62% v/v as an antiseptic. Ethanol

kills organisms by denaturing their proteins and dissolving their lipids and is

effective against most bacteria and fungi, and many viruses, but is

ineffective against bacterial spores.

TREATMENT FOR POISONING BY OTHER ALCOHOLS:

Ethanol is sometimes used to treat poisoning by other, more toxic alcohols,

in particular methanol  and ethylene glycol. Ethanol competes with other

alcohols for the alcohol dehydrogenase enzyme, lessening metabolism into

toxic aldehyde and carboxylic acid derivatives, and reducing one of the more

serious toxic effects of the glycols, their tendency to crystallize in

the kidneys.

SOLVENT:

Ethanol is miscible with water and is a good general purpose solvent. It is

found in paints, tinctures, markers, and personal care products such as

perfumes and deodorants. It may also be used as a solvent in cooking, such

as in vodka sauce.

DESCRIPTION:

1. BLOCK DIAGRAM:

2. RAW MATERIALS:

 MOLASSES: The most widely used sugar for ethanol fermentation is

blackstrap molasses which contains about 35 – 40 wt% sucrose, 15 – 20 wt

% invert sugars such as glucose and fructose, and 28 – 35 wt% of non-sugar

solids. Blackstrap (syrup) is collected as a by-product of cane sugar

manufacture. The molasses is diluted to a mash containing ca 10 –20 wt%

sugar. After the pH of the mash is adjusted to about 4 – 5 with mineral acid,

it is inoculated with the yeast, and the fermentation is carried out non-

aseptically at 20 – 32°C for about 1 – 3days. The fermented beer, which

typically contains ca 6 – 11 wt% ethanol, is then set to the product recovery

in purification section of the plant.

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 theorectical. 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 leaser 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) is sufficient to retard microbial growth and at 10% (w/v)

alcohol, the growth rate of the organism is nearly halted. To be specific yeast

is a eukaryotic micro-organism. Not all yeasts are suitable for brewing.

 WHY YEAST?

According to P.Gunasegaram (1999), the yeast Saccharomyces

cerevisiae and facultative bacterium Zymomonas mobilis are better

candidates for industrial alcohol production. Z. mobilis possesses advantages

over S. cerevisiae with respect to ethanol productivity and tolerance. But the

bottlenecks in Z. mobilis are:

i)  its inability to convert complex carbohydrate polymers like

cellulose, hemicellulose, and starch to ethanol,

ii)  its resulting in byproducts such as sorbitol, acetoin, glycerol

and acetic acid,

iii)  Formation of extracellular levan polymer.

As reported in batch fermentation, sugar concentrations as high as 223

g/l could be fermented to 105 g/L ethanol in 70 hours. The percentage

theoretical yield was 92%. Whereas in a continuous fermentation using

mixed cultures of Z. mobilis and S. cerevisiae, production of 54.3 g/L of

ethanol was observed within 3 days. A high ethanol productivity of 70.7

g/L/hr was obtained with a final ethanol concentration of 49.5 g/L and yield

of 0.5 g/g. this amount to 98% of the theoretical yield and 99% substrate

conversion.

WATER:

Molasses when introduced into the fermenter is first diluted because

molasses is basically a thick syrup which cannot be fermented easily as

choking of materials takes place and this thick liquid may stick to the walls

of the reactor and disturbs the entire section. To avoid this molasses is first

diluted hence water also takes a part among raw materials.

REACTION INVOLVED:

The main reaction involved in this process is molasses containing 20-25% of

glucose will be decomposing into ethanol molecules and carbon dioxide

molecules. This process takes place in the fermentation cell where yeast

being the catalyst.

C6H12O6 ----yeast------> 2 C2H5OH + 2 CO2

Thus from the above reaction we can deduce that 1 molecule of glucose

decomposes into 2 molecules of ethanol and 2 molecules of carbon dioxide

in the presence of yeast. A small amount of oxygen also supplied for the

yeast to get multiplied inside the reactor.

PROCESS:

As it was already mentioned that molasses is the by-product of sugar

industry, molasses is first diluted with water. For the sugar content of nearly

20-25% (w), 75-80%(w) is added and will be sent into fermenter and allow

them to react or ferment for 1-3days. In the fermenter, the formation of ethyl

alcohol takes place. In brewing, alcoholic fermentation is the conversion of

sugar into carbon dioxide gas (CO2) and ethyl alcohol. This process is

carried out by yeast cells using a range of enzymes. This is in fact a complex

series of conversions that brings about the conversion of sugar to CO2 and

alcohol. To be specific yeast is a eukaryotic micro-organism. Not all yeasts

are suitable for brewing. In brewing we use the sugar fungi form of yeast.

These yeast cells gain energy from the conversion of the sugar into carbon

dioxide and alcohol. The carbon dioxide by-product bubbles through the

liquid and dissipates into the air. In confined spaces the carbon dioxide

dissolves in the liquid making it fizzy. The pressure build up can be quite

immense. Certainly enough to cause the explosion of a sealed glass bottle.

The other by-product alcohol, remains in the liquid which is great for us but

not for the yeast, as the yeast dies when the alcohol exceeds its tolerance

level. Wine yeast is more tolerant at a range of 10-15%. Specially cultured

strains of yeast with the correct environment can withstand alcohol levels up

to 21% alcohol. Then the beer stream which consists of alcohol (10-15%)

and water mixture and CO2 will be separated into two different streams

where CO2 will be sent into the beer column where the CO2 stream will be

separated by varying temperature or pressure conditions. In general pressure

would be increased to separate the gas stream because if temperature is

increased, the quality of alcohol is affected. Much of the CO2 that is

generated during the fermentation process can be captured and converted

into marketable products, such as dry ice, liquid CO2 for soft drinks, fire-

fighting foams, filtration products and various industrial uses. After

separating CO2, the ethanol-water mixture will be sent into distillation

column and the ethanol will separated and collected at the top and water at

the top. In practice, maximum of 95% of ethanol can be recovered. This

mixture is often referred to as “hydrous sugarcane ethanol” because it

contains 5% water. 

SIMULATION:

Now we simulate the process using Aspen Plus and the basic flow chart of

simulation procedure will be as follows:

Fig: Design of ethanol production process

INPUT:

GLOBAL:

TITLE-PROJECT

UNITS OF MEASUREMENT:

INPUT DATA-ENG

OUTPUT RESULTS-ENG

DESRIPTION- PRODUCTION OF ETHANOL

ACCOUNTING:

USER NAME-CHEMICAL

ACCOUNT NUMBER-07842

PROJECT ID-1

PROJECT NAME-ETHANOL

FLOW SHEET:

SECTION-GLOBAL

STREAM CLASS-CONVEN

STREAM CLASS:

AVAILABLE STREAMS- CISOLID, NC, NCPSD, CIPSD

SELECTED SUBSTRAMS-MIXED

SPEICIFICATIONS:

SUBSTREAM NAME: MIXED

TEMPERATURE-250C

PRESSURE-1atm

COMPOSITION-MASS FLOW (TONNE/DAY)

COMPONENT VALUE

DEXTRO-01

WATER

CARBO-01

ETHAN-01

21

79

0

0

FLASH OPTIONS:

MAXIMUM NUMBER OF ITERATIONS: 100

VALID PHASES-VAPOR-LIQUID

ERROR TOLERANCE-0.0001

OPERATING CONDITIONS:

PRESSURE- 2atm

TEMPERATURE- 300C

HOLD UP:

VALID PHASES: VAPOR-LIQUID

SPECIFICATION TYPE: REACTOR VOLUME

REACTOR: 8KL

SEPERATOR SPECIFICATIONS:

STREAM SPECIFICATION: SPLIT FRACTION

SUB STREAM:MIXED

OUTLET STREAM: CO2

COMPONENT ID SPLIT FRACTION

CARBO-01 1

ETHAN-01 0

WATER 0

DEXTR-01 0

COLUMN SPECIFICATIONS:

NO. OF STAGES-20

PRESSURE:

CONDENSER-1atm

REBOILER-1.5atm

KEY COMPONENT RECOVERY:

LIGHT KEY

COMPONENT-ETHAN-01

RECOVERY-0.95

HEAVY KEY

COMPONENT-WATER

RECOVERY: 0.05

REACTION:

TYPE-EQUILIBRIUM

R-1:

DEXTRO-01 2ETHAN-01 + 2 CARBO-01

RESULTS:

ASSUMPTIONS:

1. Let the ethanol content in the beer stream be 11%.

2. As there is no large difference in temperature through out the process,

let it be an isothermal process.

3. Let negligible amount of CO2 is present in ethanol stream and

negligible amount of ethanol in CO2.

DATA SUPPLIED:

INLET STREAM:

Mass flow of glucose=21tonne/day

Mass flow of water=79tonne/day

Temperature=250C

Pressure=1atm

OPERATING CONDITIONS:

P=2atm

T=300C

Volume of reactor=8kl

GAS-LIQUID SEPARATOR:

Split-fraction of CO2=1

DISTILLATION COLUMN:

No. of stages=20

Condenser pressure=1atm

Re-boiler pressure=1.5atm

Key Component recoveries:

Light key component=ethanol

Recovery=0.95

Heavy key component=water

Recovery=0.05

MATERIAL BALANCE:

Mass flow of glucose in=21tonne/day

Mass flow of water in=79tonne/day

Moles of glucose in=W (in g)/GMW = 0.116×106

Moles of water in= 4.388×106

Mole fraction of ethanol=92/180=0.5111

Mole fraction of CO2=88/180=0.4889

Let the weight % of ethanol present in the outlet stream =11

Thus the amount of ethanol present is=100×11/100=11tonne

Mass of ethanol present in the outlet stream =21×0.511=10.731tonne

Mass of CO2 present in the outlet stream=21-10.731=10.269tonne

No. of moles of ethanol=0.2332×106

No. of moles of CO2=0.2333×106

No. of moles of H2O=4.388×106

After the separation of CO2 stream,

the mole fraction of ethanol in the inlet stream to the distillation column

is=0.05042

the mole fraction of water=0.98864

Our aim is to produce 95% of ethanol of weight nearly 10 tonne/day

Writing the material balance to the distillation column,

F=feed=79+10.731=89.731

W=bottom product

D=distillate (or) top product=10.731×0.95=10.19

XF=mole fraction of the feed=0.05042

XD=mole fraction of the distillate=0.95

XW=mole fraction of bottom product

Overall mass balance of the column is

F=D+W

89.731=10.19+W

W=79.541tonne

Writing component balance taking ethanol as basis,

FXF=DXD+WXW

(89.731)(0.05042)=10.19(0.95) +79.541XW

XW=0.0646

Thus the amount of ethanol produced is=10.19tonne/day

Amount of water produced is=74.58tonne/day

Mole fraction of ethanol=0.511

Mole fraction of water=0.488

From the results obtained from Aspen simulation,

The amount of ethanol produced is=10.2tonne/day

The amount of water produced is=75.50tonne/day

Mole fraction of ethanol produced is =0.502

Mole fraction of water produced is =0.49

Hence we can deduce that the results obtained are true and valid.