Manufacturing process for distillery industry
Batch Process:
From the molasses storage tank molasses is taken to the automatic weighing tank. The exact quantity of molasses to be used in the process is determined hear. Concentration is diluted with water to reduce sugar from 40-45% to 10-15%.
Sugar concentration more than 10-15% is not employed as it is detrimental to yeast. In the pre-fermenters the yeast culture is added and here the pH of the medium is maintained around 4-4.5. For this purpose sulphuric acid or Lactic acid is used. Urea is added as substrate to the yeast culture. The detention period in the pre-fermenters is 4-6 hours. This fully developed culture is then mixed with the remaining molasses and kept in fermentation tank. Here the detention time is 34-36 hours.
The temperature is maintained at around 35-37 0C.
After fermentation is completed the yeast sludge removed from the bottom. The fermenter wash is pumped to the boiling column for distillation.
The temperature of the wash is maintained at 75-78 0C by passing it through beer heater and heat exchanger.
Then the wash is fed to the top of the boiling column and the steam is applied at the bottom. Alcohol gets evaporated at about 78 0C.
The mixture of alcohol steam is collected at the top of the column. The alcohol free spentwash is collected at the bottom.
The impure alcohol is then taken to the rectification column. In this column alcohol vapors move upwards and the water vapors remain down. These are collected at the exhaust column. This is termed as spentleese. The purified alcohol vapors are trapped at the top of the analyzer column. This is called rectified spirit.
This passed through spirit cooler to the tester to check the concentration etc. from time to time. This is then collected in rectified spirit chamber.
The various wastes generated are taken for further treatment.
CONTINUOUS FERMENTATION PROCESS:-
Raw molasses is stored in the Molasses Day Tank. The molasses is pumped to the Molasses Receiving Tank by Molasses Day Pump till the prefixed amount of raw molasses is filled in Molasses Receiving Tank with the help of ON-OFF valve operation and later the weighed amount of raw molasses flows under gravity to Weighed Molasses Tank. The amount of molasses is weighed in the batches and total no. of batches are counted to estimate daily consumption of the molasses in the plant.
Molasses from the Weighed Molasses Tank is continuously pumped by Weighed Molasses Pumps to the Fermentors.
To start the fermentation, initially yeast cell mass is required. The required yeast cell mass is inoculated in various stages of cell mass propagation which is started from the laboratory and completed in the Culture Vessels.
Initially Yeast Cell Mass from the last stage of Cell Mass Propagation is transferred to first Fermentor. Molasses and Process Water are fed to the Fermentor for maintaining required sugar concentration through Molasses Broth Mixer.
To feed the Molasses in the Fermentor on continuous basis, Fermentor Feeding System is provided which includes Molasses Broth Mixers, Fermented Wash Re-Circulation Pumps and Connecting Pipe Line. Fermentor liquid i.e. Fermented Wash is circulated at high flow rate through Molasses Broth Mixer, where molasses ( highly viscous) is mixed with the circulating liquid and gets diluted.
Homogeneity of Fermented Wash in the Fermentor is maintained by the Sparger fitted in each Fermentor. Sparging ensures the suspension of yeast cells in the Fermentor Liquid uniformly.
During fermentation, which is a exothermic reaction, heat is generated. To maintain desired Fermentor Temperature Fermentor Cooling System which includes Fermented Wash Coolers, Fermented Wash Re-Circulation Pumps (common for Feeding System also) are provided for this system. Fermentor Liquid is circulated through Fermented Wash Coolers where heat of fermentation reaction is removed by using cooling water on the other side of the coolers.
Fermented Wash at the end of the fermentation reaction is pumped to Yeast Settling Tank, which works on the principal of gravity settling. Live Yeast cells which coagulate to form granules become heavier than Fermented Wash Liquid as well as sludge present in the Wash. Due to this gravity difference granulating yeast cells are separated from the Fermented Wash from bottom of the Yeast Settling Tank. Overflow of the Yeast Settling Tank goes to wash Holding Tank for the recovery of the alcohol.
Yeast Cell Mass collected from bottom of Yeast settling tank is taken to the Prefermentor. Yeast cells which are generated during fermentation process are recycled back to the fermentation process. Before recycling back to the process, it is separated from the Fermented Wash and treated with concentrated Sulfuric acid for killing unwanted bacteria. After acidification of Yeast cells, necessary nutrients like DAP, Urea, MgSo4 etc. are fed continuously to Prefermentor. Molasses is fed in the Activation Vessel to provide required sugar for the growth of yeast cells. Required amount of process water for maintaining desired sugar concentration is fed directly to it. Air is sparged continuously to supply necessary Oxygen required for the growth of yeast cells. This also helps to keep the cell mass in suspension. Activated yeast cell mass is pumped back to first Fermentor continuously.
Overflow of Fermented Wash from Yeast Settling Tank is fed to Wash Holding Tank. Sludge coming along with Fermented Wash settles down by gravity at the bottom of the Wash Holding Tank. Clear overflow from Wash Settling Tank is sent to the Distillation Section. Sludge from bottom of the Wash Holding Tanks is collected in Sludge Trough. This sludge carries some contents of Alcohol in the form of Wash. Sludge in Sludge Trough is diluted with water and is fed to the Sludge Settling Tank. Sludge Settler also works on the principle of gravity settling. Clear overflow from Sludge Settler is transferred to the Wash Holding Tank. While sludge from the bottom of the Sludge Settling Tank withdrawn for disposal.
Possible losses of Alcohol along with generated Carbon Di-Oxide from Fermented Wash are recovered in CO2 Scrubber. Alcohol from Carbon Di-Oxide is scrubbed with water in Gas Scrubber.
Nutrients and Biocides are added to the Fermentor intermittently depending upon the requirement.(i.e. yeast dry condition and its condition). Sulfuric acid also added to Fermentor( as and when required) to adjust the pH of Fermentor Liquid. Excess foaming in the Fermentor is controlled by antifoam solution. These chemicals are dosed in the Fermentors from Dosing System.
Air Blowers are provided for sparging air to the Prefermentor.While CO2 Blowers are provided to sparge CO2 to the Fermentor.
DISTILLATION SECTION:-
Fermented Wash from the Fermentation Section is preheated in Fermented Wash Preheateer against the spent wash from Analyser Column. This Wash is then fed to the Analyser Column. The column operates under vacuum. The vapour from Analyser Column is fed to Prerectifier Column, which also operates under vacuum. The bottom of Analyser Column is heated by circulating the wash through Analyser Column Reboiler by using latent heat of condensation of vapours from the Rectifier cum Exhaust Column. The Condensate from the Reboiler and its Vent Condenser is collected in the Rectifier Reflux Tank and is pumped back to Rectifier cum Exhaust Column as reflux. The wash depleted of Alcohol is removed from the bottom of the Analyser Column as Spentwash.
In Prerectifier Column the light ends such as Acetone, Acetaldehyde, Esters are separated in the form of an Impure Spirit. The bottoms are fed to the Rectifier cum Exhaust Column.
The Rectifier cum Exhaust Column operates under pressure and is being heated by Steam. The vapours from this column are used to heat the bottom of Analyser Column. This column concentrates the Ethanol to 95% v/v . Spirit is drawn from one of the upper trays of the column. The heads cut is removed from the overheated stream as Impure Spirit. Cut to withdraw impurities. The Spentlees is removed from the bottom of the column. Fusel Oil Streams are taken from the lower trays of the column to avoid Fusel Oil build up in the column. These streams are then fed to the Fusel Oil Concentration Column after cooling it in Fusel Oil Cooler.
The Fusel Oil Concentration Column operates under atmospheric pressure and is heated by Live Steam. This column concentrates the dilute streams of Ethanol containing Esters and Fusel Oil to approximately 95% v/v of ethanol. The Impure Spirit Cut is removed from the top of the column. Side draw streams are taken from the lower trays of the column to avoid fusel oil build up in the column. The streams are taken to the Fusel Oil Decanter after cooling in Fusel Oil Cooler. Process water is added for dilution to the Fusel Oil Decanter. Fusel oil separates from this mixture in the Fusel Oil Decanter and being lighter floats on the top. This layer is continuously removed as fusel oil draw. The washings from the Fusel Oil Decanter bottom is fed back to the column.
The Impure Spirit, Rectified Spirit and Fusel Oil is sent to Receiver and finally to Storage.
