Grains in various forms, broken or damaged grains, are procured from various sources and stored in Grain Silos or in open grain yards covered with tarpaulin. All types of grains like broken rice, damaged wheat, Jowar, and Maize / Corn are used in the plant.
The grain is lifted in bucket elevators and screened, followed by the removal of stones and iron matter. Cleaned Grains are then milled using a dry milling process in Hammer Mills. The flour is fed through the bucket elevator and conveyed to the Batch Tipping Machine through a Screw Conveyor. The flour addition is metered through the Batch Tipping Machine with load cell arrangement before transferring the flour to the Slurry Tank through another Screw Conveyor (pre-masher) for the slurry preparation process.
Grain flour and process water are fed at a controlled rate to Slurry Tank. Mixed slurry is taken to the Initial Liquefaction tank, where the additional quantity of water is added as per requirement. Viscosity reduction Enzyme and stabilizing chemicals and a portion of the liquefying enzyme are also added at this stage. The slurry is then “cooked” in the jet cooker. The slurry is continuously pumped to a steam jet cooker, where high-pressure steam at 3.5 bar (g) rapidly raises the slurry temperature. The mixture of slurry and steam is then passed through the Retention loop. The retention loop has several “U” bends in series with sufficient capacity to provide the desired retention time at a given flow rate. The cooked mash is discharged to a Flash Tank.
The cooking process, accomplished in the above manner, converts the slurry into a hydrated, sterilized suspension and is, therefore, susceptible to enzyme attack for liquefaction.
The gelatinized mash from the Flash Tank is liquefied in the initial and final liquefaction tank, where liquefying enzyme (alpha-amylase) is added. The liquefied mash is cooled in Mash Cooler and transferred to the Saccharification cum fermentation section. This process initiates the formation of sugar. The gelatinized mash from the Flash Tank is liquefied in the Final Liquefaction Tank, where liquefying enzyme (alpha-amylase) is added. The liquefied mash is cooled in Mash Cooler and transferred to the Saccharification cum Fermentation section.
Yeast seed material is prepared in a water-cooled Yeast Activation Vessel by inoculating a sterilized mash with active dry yeast. The optimum temperature is maintained by cooling water. The contents of the Yeast Activation Vessel are then transferred to Fermenter.
The purpose of fermentation is to convert the fermentable substrate into alcohol. To prepare the mash for fermentation, it may have to be diluted with water. The pH of the mash is adjusted by the addition of acid. Yeast is available in sufficient quantity to initiate fermentation rapidly and complete it within the cycle time.
At the start of the cycle, the Fermenter is charged with mash and contents of the Yeast Activation Vessel. Significant heat release takes place during fermentation.
This is removed by passing cooling water through the Fermenter PHEs to maintain an optimum temperature. The recirculating pumps also serve to empty the fermenters into the wash charger. After the fermenters are emptied, they are cleaned with water and caustic solutions and sterilized for the next batch. The carbon dioxide evolved during the process is sold after the recovery of alcohol in a scrubber.
The fermented mash contains about 10-14% percent Ethanol. The rest of the mixture is water and organic solids that couldn't be fermented. To separate the Ethanol, the mixture is heated once again with the help of steam in the distillation column - this time to a temperature at which Ethanol vaporizes, but the remaining materials do not. The Ethanol vapour is collected and cooled, and where it condenses to its liquid form; after that, the purification process is done to achieve the 96 % strength of the alcohol.
The major energy required for the distillation is the low-pressure steam which is supplied by the co-generation plant.
Distillation is a separation technique for the liquid mixture. It is an operation where the vaporization of a liquid mixture yields a vapour phase containing more than one constituent in a nearly pure state. Thus the separation of mixtures of alcohol and water into its component is called distillation.
