Process Technology

1] FEED PREPARATION AND WEIGHING

Molasses Stored in a storage tank is first weighed in a tank with load cells so that accurate quantity can be fed to the fermentation section. The weighed molasses then transferred from tank to the dilutor in fermentation section where it is diluted with water and fed to the Fermenter.

2] YEAST PROPAGATION AND FERMENTATION

The Yeast from Slant is transferred to Shaker Flasks and grown to the required volume. This “genetically marked” yeast strain is then further propagated, under aseptic conditions, in yeast culture vessel. These vessels are equipped with eductors which are designed to achieve enhanced efficiencies through better sugar / yeast contact by shearing and mixing, efficient oxygen transfer etc.

The ready yeast “seed” is then transferred from culture vessel to fermenter. The molasses is diluted by process water. The glucose in the Feed media gets converted to ethanol, in each of the 4 Fermenters operating in Batch mode. A plate heat exchanger and a circulation pump are provided to each fermenter, which will continuously re‐circulate the Fermenting Wash through PHE for maintaining the Fermenters at 30 deg C.

The nutrients, biocide, acid and anti‐foam agents are fed to the fermenters as per process requirement. The CO2 liberated during fermentation is sent to CO2 Scrubber for recovery of ethanol otherwise being lost in vent. The Fermented Wash is then sent to the Clarification Tank equipped with Lamella Separator. The settled sludge is sent to Sludge Washing Tank for recovery of alcohol.

3] MULTIPRESSURE DISTILLATION (RS)

The fermented wash is fed to CO2 stripper column to remove CO2 gas present in wash.

Alcohol is stripped off water in stripper column. The top vapours [alcohol + water] are fed to Beer Heater & Condenser. Distillate from Beer Heater & Condenser is pre‐heated by steam condensate and spent leese before being fed to rectifier column. In rectifier column RS is taken out from top tray. The impure spirit from top of CO2 stripper column, rectifier column, fed to fusel oil column. The final impure spirit cut is taken out from the fusel oil column and partly alcohol is recycled to rectifier column. The alcohol containing fusel oil from rectifier column is fed to fusel oil column.

Rectification column works under pressure. The CO2 stripper, stripping column, works under vacuum and fusel oil column works under atmospheric condition.

The top vapours from rectifier column are condensed in Stripper Reboiler. The alcohol water vapours from stripping column are partly sent to CO2 stripper bottom for heating.

The Rectifier column and fusel oil column gets heat from steam.

The Distillation process is operated through PLC.

5] PROCESS DESCRIPTION FOR FA (DEHYDRATION)

Molecular sieve technology works on the principle of pressure swing adsorption. Here water is removed by adsorbing on surface of `molecular sieves’ and then cyclically removing it under different conditions (steaming).

Molecular sieves are nothing but synthetic zeolites typically 3A zeolite. Zeolites are synthetic crystalline aluminosilicates. This material has strong affinity for water. They adsorb water in cold condition and desorb water when heated. This principle is used to dehydrate ethanol. The crystalline structure of zeolites is complex and gives this material the ability to adsorb or reject material based on molecular sizes. Water molecule can enter the sieve and be adsorbed, but larger alcohol molecule will not be retained and will go through the bed. There can be two to three beds in parallel. Once a particular bed is saturated with water, it is heated with steam so that adsorbed water is desorbed from the bed. Till that time, other bed is used for dehydration.

This type of system is characterized by Low steam consumption and low power consumption as compared to distillation. The only disadvantage of molecular sieves is the high attrition rates of sieves in case of small plants. Hence, typically, some amount of sieve material needs replacement periodically, thereby resulting in higher cost of production in case of small capacity plants. In case of large capacity plants, the molecular sieve is the most optimum both in terms of initial investment & operating cost.

What is Zero liquid discharge ? About Zero Liquid Discharge (ZLD) For Distillery Industry
  • Distillery sector is one of the 17 categories of major polluting industries identified by Ministry of Environment and Forest, Govt of India.
  • There are > 300 distilleries in the country.
  • Total installed capacity of about 2500 million kilo litres of ethanol per annum.
INCINERATION

Incineration processes are based on the concept that concentrated distillery spent wash (60% w/w) will burn on its own without any external input of energy. In other words, the incineration process of 60% (w/w) concentrated spent wash is considered to be self-sustaining. There are two basic approaches for concentrating spent wash :

  • Concentration and incineration with steam generation, and
  • Direct contact evaporation and incineration.

The concentrated spent wash is subsequently incinerated in a specially designed boiler. One of the alternatives for recovering heat from flue gases would be to send the flue gases to a waste-heat boiler. Steam generated there could be used to concentrate raw spent wash to 60% w/w concentration in a multiple effect evaporator system.