Zero Liquid Discharge (ZLD) Solutions
Uttamenergy offers ZLD solutions for molasses-based distilleries or ethanol plants by recovering water and renewable energy to conserve resources and protect the environment.
Normally the effluent from distilleries say spent wash/slop/vinasse are in proportionate to 9 to 12 times of daily ethanol production with around 11 to 14% solid content. A typical analysis of effluent is given below:
● Colour as deep reddish brown
● Aromatic odour
● Specific gravity as 1.05
● pH as 4.5
● BOD as 50000-55000
● COD as 80000-85000
● Total nitrogen as 927 mg/l
● Total phosphate as 45.6 mg/l
● Total potassium as 61.0 mg/l
ZLD solutions are provided either by bio methanation route or incineration route. Please refer to the schemes illustrated below.
Bio Methanation Route
Effluent vinasse/slop from distillery are subjected to bio methanation in a bio digestor which reduces the BOD/COD content substantially by generating bio gas with a concentration of 50–55% on a volume basis. This biogas may be utilized as per the three options mentioned below which are based on the economics prevailing in the market.
Option-1 : As a supplementary fuel in the boiler
Option-2 : To generate power through gas engines by purifying biogas to the needed extent
Option-3 : To refill CNG bottles by purifying biogas with methane content > 95%
The digestate post bio methanation process is subjected to concentration in a multiple effect evaporator to recover water. The concentrate will be further sent to either bio composting or dryer to produce manure.
Vinasse/Slop effluent from distillery are concentrated in a multiple effect evaporator up to 52–60% solids and directly fired in the incineration boiler in the combustion chamber above the grate. Supplementary fuel are always required for effective and sustainable combustion which may include fuels like bagasse, wood chips, rice husk or coal. Combustors with travelling grate stokers are preferred for fuel flexibility.