WASTE HEAT EVAPORATOR (WHE)
A & S THAI WORKS CO., LTD
The only purpose of the WHE is to save energy by lowering the steam consumption.
The WHE can reduce the steam consumption for drying by up to 50 %, this is important as the boiler fuel is expensive, like diesel oil, heavy fuel oil or natural gas.
The WHE is used for OFP (Oily Fish Fishmeal Plants) and LTR (low temperature) rendering plants using cooker and twin screw press and disc dryer that produces the waste heat vapor.
The WHE come in 1-stage (effect) or 2 or 3 stage. Every higher stage increases the saving effect.
The stick water coming from decanter and separator contains 8 to 12% protein (like sugar dissolved in water)
This protein is valuable and must be recovered to get higher protein % in the meal and better price. If the stick water is thrown away it is very polluting.
When the WHE has run for a while, the stick water will concentrate to a thick syrup that is pumped into the drier and mixed with the finished meal.
The WHE does not use steam from the boiler, but use the wasted vapor from the disc drier that would normally be thrown away.
The disc drier will evaporate water at normal boiling point 100 deg C. The WHE will evaporate water under vacuum where the boiling point is only 70 deg C.
The design of a WHE is basically a stainless heat exchanger with tubes, a circulation pump for the stick water which is pumped around and around, a vacuum pump plus feed pumps, and a condenser.
WHE requires skilled operators and good maintenance and must often be cleaned by flushing with hot water (daily), caustic soda and acid solutions (weekly) using a CIP – automatic cleaning in place system
