Ethanol production from various feed-stocks in sugar process | Yield of Ethanol

Calculating Yield of Ethanol from Sucrose and  its Process Intermediate Products

This Article explained about calculation of ethanol yield from various feed stocks (Intermediate products) in sugar manufacturing process like sugarcane juice, secondary juice, syrup, A-molasses, B- heavy molasses and final molasses .. etc.

Calculating theoretical yield of ethanol from sucrose

The chemical equation from sucrose to ethanol can be written as ( Stoichiometric Equation )

C12 H22O11 + H2O    \overset{Invertage \ (or) \ \ H^+}{\rightarrow} C6 H12 O6 +  C6 H12 O6 \overset{Zymase}{\rightarrow}  4 C2H5 OH + 4 CO2

Sucrose   \rightarrow  Glucose + Fructose  \rightarrow   Ethanol (Ethyl Alcohol)

  • Molecular weight of sucrose                – 342.30 gm/mol or kg/kmol
  • Molecular weight Glucose/Fractrose – 180.16 gm/mol or kg/kmol
  • Ethyl Alcohol Molecular weight           – 46.07 gm/mol or kg/kmol
  • Molecular weight of carbon dioxide     – 44.01 gm/mol or kg/kmol

Molar mass balance (kmol x kg/kmol)

1 x 342.30 \rightarrow 4 x 46.07 + 4 x 44.01

Mass balance percentage of the above equation

100% of Sucrose  \rightarrow  53.84% ethanol + 51.43 % carbon dioxide

The density of anhydrous ethanol (100%) is 0.78934 Kg/L at 20°C

So Theoretical ethanol production from sucrose (100 kg) = 53.84 / 0.78934 = 68.2 Liters

Calculating theoretical yield of ethanol from glucose/Fructose (Reducing Sugars)

The chemical equation from reducing sugars to ethanol can be written as ( Stoichiometric Equation )

C6 H12 O6  \overset{Zymase}{\rightarrow}  2 C2H5 OH + 2 CO2

Glucose/Fructose  \rightarrow   Ethanol (Ethyl Alcohol)

  • Molecular weight Glucose/Fractrose – 180.16 gm/mol or kg/kmol
  • Ethyl Alcohol Molecular weight           – 46.07 gm/mol or kg/kmol
  • Molecular weight of carbon dioxide     – 44.01 gm/mol or kg/kmol

Molar mass balance (kmol x kg/kmol)

1 x 180.16 \rightarrow 2 x 46.07 + 2 x 44.01

Mass balance percentage of the above equation

100% of Glucose  \rightarrow  51.14% ethanol + 48.86 % carbon dioxide

The density of anhydrous ethanol (100%) is 0.78934 Kg/L at 20°C

So Theoretical ethanol production from sucrose (100 kg) =51.14 / 0.78934 = 65 Liters

Fermentation Efficiency:

Fermentation is bio chemical process in which organic compounds converted in to simple organic compound by enzymes which is secreted by micro-organism.

The ratio between Practical yield to Theoretical yield

Theoretical Yield  = (Molasses consumed x  Fermentable sugar % * 650) / 100

Hence One ton Fermentable sugar will give 650 Liters of Absolute alcohol.

Practical Yield = (Total wash production x  Alcohol percentage in wash) / 100

Fermentation Efficiency = \ \frac{ Practical \ \ Yield}{Theoretical \ \ Yield} \ \times \ 100

Distillation efficiency :

The distillation efficiency is the ratio of the mass of ethanol in the final product to the mass of ethanol in the feed (wash) to the distillery.

Distillation Efficiency is the ration of Actual Alcohol production to  Alcohol in wash distilled

Actual Alcohol Production = \frac{ Alcohol \ \ production \ \times \ Alcohol \ \ proof}{175}

Hence 175 proof is equal to 100 percentage alcohol (Absolute Alcohol)

Alcohol in Wash Distilled     = \frac{ Wash \ \ Distilled \times \ Alcohol \ percentage \ in \ wash} {100} )

Distillation Efficiency  = \frac{ Actual \ Alcohol \ Production} {Alcohol \ in \ Wash \ Distilled} \ \times \ 100

Overall Efficiency

Fermentation efficiency * = \frac{ Fermentation \ Efficiency \ \ \times \ Distillation \ \ Efficiency}{100}

Various feed stocks in sugar process for ethanol production

The yields of ethanol from various feed-stocks available in a cane sugar process

  • Primary Juice / Mixed juice / Secondary juice
  • Clarified juice/ Concentrated clear juice (Syrup)
  • B Heavy Molasses / Final Molasses
Ethanol production from sugarcane juice (Mixed juice / Clarified Juice/ Secondary juice )

Taken one example:

S.NO Particulars UOM Mixed Juice Remarks
1 Brix of the Material oC 14.5 13 to 16
2 Purity of the material % 81 78 to 84
3 Reducing Sugars (RS) % 0.6 0.5 to 0.7
4 Un Fermentable Sugars (UFS) % 0.1 0.1 to 0.2
5 Fermentation Efficiency (FE) % 90 88 to 91
6 Distillation Efficiency (DF) % 98.5 98 to 99%
7 Sucrose % (Pol) % 11.745 (Brix) x (Purity ) / 100
8 Total Reducing sugars (TRS) % 12.345 Sucrose % + Reducing Sugars%
9 Fermentable sugars (FS ) % 12.245 TRS – UFS
10 Yield of Ethanol Ltrs/MT 71  FS x 0.65  x FE x DF x 10)
Ethanol production from sugarcane molasses (B Heavy and Final Molasses)

Taken one example  for B-Heavy molasses

S.NO Particulars UOM B – Heavy Molasses Remarks
1 Brix of the Material oC 83 78 to 85
2 Purity of the material % 49 45 to 55
3 Reducing Sugars percent (RS) % 12 10 to 14%
4 Un Fermentable Sugars (UFS) % 1.2 1 to 1.5%
5 Fermentation Efficiency (FE) % 90 88 to 91
6 Distillation Efficiency (DF) % 98.5 98 to 99%
7 Sucrose % (Pol) % 40.67 (Brix) x (Purity ) / 100
8 Total Reducing Sugars (TRS) % 52.67 Sucrose % + Reducing Sugars%
9 Fermentable Sugars (FS ) % 51.47 TRS – UFS
10 Yield of Ethanol Ltrs/MT 297  FS x 0.65  x FE x DF x 10)
Approximate values of Various Feed Stocks in sugar process
Name of Feed Stock  Purity Brix% Pol% (sucrose) Reducing sugars % by weight Unfermentable sugars by Weight Approx.Sp. Gravity
Primary juice 80 to 86 16 to 22 12 to 18 0.5 to 0.8 0.2 to 0.5 1.071
Secondary juice 78 to 86 10 to 14 7 to 12 0.2 to 0.5 0.2 to 0.4 1.043
Mixed juice 78 to 86 12 to 15 9 to 13 0.4 to 0.8 0.2 to 0.4 1.056
Clarified juice 78 to 86 12 to 15 9 to 13 0.4 to 0.8 0.2 to 0.4 1.061
B Heavy Molasses 48 to 55 78 to 84 36 to 47 10 to 14 1 to 1.5 1.4
Final Molasses 28 to 34 88 to 92 25 to 32 12 to 18 1.2 to 2 1.4

Online Calculator for Yield of Ethanol

Advantages while using Clear juice as a feed stock of Ethanol production:

1. Clean substrate as compared to molasses therefore juice fermentation gets good fermentation rate & efficiency.

2. Biochemical Oxygen Demand (BOD) & Chemical Oxygen Demand (COD) of the effluent will be much less as compared to molasses; therefore effluent treatment cost is very less.

3. Quality of the alcohol from clear juice is better than the alcohol drawn from molasses.

4. Cane does not have high content of dissolved solids and therefore there is no scaling and blocking in distillation column as it forms with the use of molasses.

5. Fermentation time less than the fermentation time taken by the molasses.

6. Colour of the effluent is less compared to spent wash from molasses based alcohol production.

Some Disadvantages while using Juice as a feed stock of production of Alcohol :

1 . The cane juice cannot be stored in bulk for any considerable length of time as it is highly contaminated with bacteria & yeast starts to ferment spontaneously very rapid.

2. This means the distillery unit must be located in close proximity to the cane mill

3. Cane juice normally becomes quickly infected with bacteria and yeast in the crushing process. So Mixed juice not preferable to directly take fermentation. It is better to go first effect or second effect juice

 

Ethanol production articles | ethanol production from sugarcane juice and molasses | Theoretical yield of ethanol from glucose | yield of ethanol from sugar

 

 

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Post Author: siva alluri

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2 thoughts on “Ethanol production from various feed-stocks in sugar process | Yield of Ethanol

    Amresh

    (September 1, 2018 - 5:37 pm)

    100% of Sucrose = 53.84% ethanol + 51.43 % carbon dioxide

    How possible elaborate please.

      siva alluri

      (September 2, 2018 - 3:26 pm)

      According to Stoichiometric Equation
      C12 H22O11 + H2O = 4 C2H5 OH + 4 CO2

      1 x 342.30 = 4 x 46.07 + 4 x 44.01

      Now consider sucrose 1 gm then
      1 = (4 x 46.07/ 342.30 ) + ( 4 x 44.01 / 342.30) = 0.5383 + 0.5143

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