DOWNSTREAM PROCESSING OF ETHANOL PRODUCTION

MEMBERS: RUCHIKA KUMAR(15MSB0001)HIMAJA .D (15MSB0034)

INTRODUCTION Ethanol  (EtOH), also commonly called alcohol, ethyl alcohol, and drinking

alcohol, is the principal type of alcohol found in alcoholic beverages, produced by the fermentation of sugars by yeasts.

It is a neurotoxic, psychoactive drug, and one of the oldest recreational drugs. It can cause alcohol intoxication when consumed in sufficient quantity and used as an additive to food and beverages and ethanol is used as a fuel

Ethanol is a volatile, flammable, colorless liquid with a slight chemical odor. It is used as an antiseptic, a solvent, a fuel, and due to its low freezing point, the active fluid in many alcohol thermometers

Globally, fuel ethanol accounts for 73% of production, with beverage ethanol at 17% and industrial ethanol at 10%

Corn and sugarcane are common feedstocks for fermentation ethanol, along with grain, and sugar beet, while synthetic ethanol’s primary feedstock is ethylene. Fuel grade or bioethanol is produced from fermentation ethanol sources. Synthetic ethanol cannot be used for fuel ethanol purposes.

DOWNSTREAM PROCESSING DSP encompasses all processes following the fermentation. In most cases

this means recovery of a product from a dilute aqueous solution. The complexity of DSP is determined by the required purity of the

product which is in turn determined by its application. Many of the steps in DSP are traditional unit processes used extensively

in the chemical industry. Downstream processing becomes very relevant in the area of bio process

as well as in chemical process technology. Downstream processing means that it refers to recovery and purification

of biosynthetic products, products coming out of a biological operation. The role of downstream processing is meant to separation, it is meant for

purification of a bio product from unwanted metabolites It becomes a big challenge to recover products in a very economical way

and try to recover it as much as possible

DISTILLATION

Ethylene hydration or brewing produces an ethanol–water mixture.

Fractional distillation can concentrate ethanol to 95.6% by volume (89.5 mole%)

Fractional distillation of this mixture at atmospheric pressure distills off the 95.6% azeotrope, leaving anhydrous ethanol at the bottom

This mixture is an azeotrope with a boiling point of 78.1 °C (172.6 °F), and cannot be further purified by distillation

This lower-boiling ternary azeotrope is removed preferentially, leading to water-free ethanol

Vacuum distillation of ethanol is not presently economical,

pressure-swing distillation is a topic of current research In this technique, a reduced-pressure distillation first yields

an ethanol-water mixture of more than 95.6% ethanol DESICCANTSApart from distillation, ethanol may be dried by addition of

a desiccant, such as molecular sieves, cellulose, and cornmeal. The desiccants can be dried and reused

Molecular sieves can be used to selectively absorb the water from the 95.6% ethanol solution

Synthetic zeolite in pellet form can be used, as well as a variety of plant-derived absorbents, including cornmeal, straw, and sawdust.

DISTILLATION METHOD

MOLECULAR SIEVE DEHYDRATION Dehydration with Molecular Sieve Process

The rectified spirit from the rectifier is superheated with steam in feed super-heater and passed to one of the pair of molecular sieve beds for several minutes. 

On a timed basis, the flow of superheated rectified spirit vapor is switched to the alternate bed of the pair. 

A portion of the anhydrous ethanol vapor leaving the fresh adsorption bed is used to regenerate the loaded bed. 

A moderate vacuum is applied by vacuum pump operating after condensation of the regenerated ethanol water mixture. 

This condensate is transferred from recycle drum to the Rectified Column in the hydrous distillation plant Via Recycle pump

The net make of anhydrous Absolute alcohol draw is condensed in product condenser and passed to product storage

The life of molecular sieve may be around five to seven years.  However, the operating cost is considerably less than azeotropic distillation

MOLECULAR SIEVE ETHANOL DEHYDRATION TECHNOLOGY FOR FUEL ETHANOL

Most of the ethanol dehydration plants for production of absolute alcohol are based on Azeotropic distillation. 

It is a mature and reliable technology capable of producing a very dry product.  

However, its high capital cost, energy consumption, reliance on toxic chemicals like benzene and sensitivity to feedstock impurities, has virtually eliminated the use of azeotropic distillation in modern ethanol plants.

 Benzene has been used as entrainer of choice of ethanol dehydration but it is now known to be a powerful carcinogen.

ADVANTAGES OF MOLECULAR SIEVE METHOD

Minimal LaborStable operationNear theoretical recovery Steam consumption minimized by multi-stage preheating to

permit substantial heat recovery and reuse.An advanced control system, developed through years of

experience, to provide sustained, stable, automatic operation.

MOLECULAR SIEVE DEHYDRATION METHOD

MEMBRANE AND REVERSE OSMOSIS

Membranes can also be used to separate ethanol and water.This process uses a pre-concentration distillation column as

first separating stepThe further separation is then accomplished with a membrane

operated either in vapor permeation or pervaporation mode.

PRODUCT RECOVERY

Ethanol is recovered from the fermentation broth by distillation or distillation combined with adsorption .

Distillation is a mature process for ethanol recovery. The first part is distilling the fermentation broth to

separate ethanol from water to reach an ethanol concentration of 95%

The ethanol dehydration plants for production of absolute alcohol are based on Azeotropic distillation.

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