This paper contains the final results of a research project to demonstrate the evaporative concentration of liquid wastes using energy-efficient heat pump technologies. The project focused on the feasibility and energy efficiency of replacing the heating and cooling utilities of a conventional steam-driven flash evaporation system with a closed-cycle heat pump. The evaporator was tested with water and fertilizer scrubber liquor at operating pressures ranging from 2 to 4.0 psia. A high-temperature, 40-ton water-to-water heat pump was used to provide heat input to the evaporator steam chest and recover heat from the evaporator condenser. The effectiveness of the steam chest was a poor 0.05 when used as a water-to-water heat exchanger and gave an approach of 37degC higher than would a heat exchanger with an effectiveness of 0.6 typically selected for energy-efficient design. The evaporator operated with an efficiency of about 78%, a value that could be improved to about 90% by insulating the vessel and lines. Using water as the feed, the heat pump coefficient of performance (COP) was a respectable 4.76 with one compressor and 4.19 with two compressors operating. Overall energy consumption was 68% less than that with a steam heat source.

KEYWORDS: Heat pumps, feasibility, high temperature, evaporation, liquids, industrial, waste, water water heat pumps, efficiency, coefficient of performance, energy consumption.