Ethanol From Molasses

Keikhosro KarimiKeikhosro Karimi

Department of Chemical EngineeringIsfahan University of Technology

What is molasses?

Molasses is a by-product of the sugar industry, defined as the end

product of sugar manufacture or refining from which no more sugarproduct of sugar manufacture or refining from which no more sugar

may be economically crystallised by conventional means.

About 75% of the world’s molasses comes from sugar cane and the g

majority of the remainder comes from sugar beet. Other sources of

molasses include citrus, corn and sorghum. Sugar cane is grown in

tropical climates (Asia, South America), whereas sugar beet has its

origin in the temperate climates (Europe and North America). The most

important constituent of molasses is sugar, being predominantly sucrose

with some glucose and fructose.

Cane Extraction

Sugar is extracted by crushing sugar cane stems to extract juice Lime (CalciumSugar is extracted by crushing sugar cane stems to extract juice. Lime (Calcium Hydroxide) is added to the juice, which is then heated and filtered in order to remove impurities. The juice is then evaporated, to concentrate the sugar and several crystallisation processes follow to extract as much sugars as possible. Centrifugal y p g p gmachines then separate the sugar and syrup. The residual syrup is often called blackstrap cane molasses.

Beet ExtractionSugar Beets are washed and sliced before undergoing a diffusion process to extract the juice. Once the juice is extracted it is processed in the same way as cane sugar In general, world molasses production is approximately one third that of the sugar production. For every 100 tonnes of sugar cane processed, 3 to 4 tonnes of molasses is produced and for every hundred tonnes of sugar beet 4 to 6 tonnes of molasses isproduced and for every hundred tonnes of sugar beet 4 to 6 tonnes of molasses is produced. The quantity of molasses produced is influenced by the market price of sugar. The higher the sugar price the more sugar extraction’s the molasses is put through to get as much sugar out as possible.

Major world producers of molasses

Country Quantity (000 tons)

Brazil 8,900

India 6,700

China 2 500China 2,500

Thailand 2,400

Pakistan 1,900

Major world exporters and importers of molasses

Fermentation of molasses

Reactions:Reactions:

Di-saccharide ---------------> Mono-saccharide

YeastMono-saccharide -----------> Ethanol + CO2

Organic matter composition of g pbeet and cane molasses

Beet molasses Cane Molasses

Sucrose 66 44

Fructose 1 13

Glucose 1 10

Betaine 6 -

Amino acids 8 3

Other substances 18 30

DistillationDistillation

Characteristics of WastewaterCharacteristics of Wastewater

The wastewater generated by molasses based di ill i h f ll i h i idistilleries has following characteristics:

- Volume: 9 to 12 L per L of alcohol producedVolume: 9 to 12 L per L of alcohol produced.

- B.O.D.: 40,000 to 60,000 ppm.

C O D 80 000 t 120 000- C.O.D.: 80,000 to 120,000 ppm.

- Total solids: 7 to 12 % w/w.

- Organic solids: 4 to 8 % w/w

Wastewater treatment

- Anaerobic Bio-Methanation followed by aerobic,

activated sludge treatment

- Aerobic, Biological Composting.

- Concentration and usage in Animal Feed.

- Concentration and Incineration, with and without,

Steam Generation.

-Disposal in water bodies like river lake or sea!!!-Disposal in water bodies like river, lake or sea!!!

-…

17

Evaporation of Vinasse by ‘FLUBEX’

- Deposition and scaling in falling film evaporators

due to presence of calcium salts in vinasse is thedue to presence of calcium salts in vinasse is the

major problem in evaporation of vinasse.

Self cleaning fl idi ed bed FLUBEX e aporators of- Self-cleaning fluidized bed FLUBEX evaporators of

PRAJ employs metal wire-bits which get fluidized

in the exchanger and gently scour the tube-walls

- FLUBEX enables use of vinasse evaporator for a

18

longer duration of 30-90 days without cleaning.

FLUBEX Mash/Vinasse Evaporator

19

20