EVAPORATION AND DRYING - A NECESSITY FOR HANDLING DISTILLERY WASTE WATER

摘要

The zero liquid discharge distillery effluent treatment system is based on the principle of concentrating the effluent and subsequently drying it to a powdered form which can be used as an alternative fuel for boilers and as an organic/ inorganic fertilizer for plant growth. Pre bio-methanated or bio-methanated distillery waste water is fed to the vacuum evaporator to concentrate it up to 50-60% total solids. The total process is under vacuum and the vapours generated in the system are re-used to economize steam consumption through thermal vapours recompression system. The resultant slurry is passed through a spray drying unit where it is converted into fine powder/granules. This powder can be used as an alternative fuel to steam boilers or by combining with other fuels. The ash generated out of burning this powder contains over 21% potassium in the form of potassium oxide. This ash has a potential to be used as a raw material to manufacture fertilizers. The dried powder from spray drying unit has a calorific value of over 3500 - 3600 kcal per kg. The emission from the spray dryer is within the norms specified by the Central Pollution Control Board. The plant operates continuously trouble free without chocking and froth formation in evaporator. Condensate recovered from evaporator is colourless liquid with BOD 80 -130 mg/l and can be reused in the plant for various applications.