Abstract
Evaluation methods of energy conservation for an evaporation process to desalt sea water was studied to cope with the trend of soaring energy cost and the warning of resource crisis.
By quoting a conceptual design of multistage flash (MSF) evaporator having a capacity of 35,520m3/d to desalt warm sea water wasted from a 700 MW power plant, the unit energy and the exergy balance were estimated for the purpose of evaluating the energy conservation. Estimation methods of unit energy were derived for a standard MSF evaporator (the maximum brine temperatureat 120°C) of both dual and single purpose. An exergy balance was also estimated for a standard MSF evaporator having a capacity of 50,000m3/d.
Unit energy indicated by heavy oil consumption (liter) per one cubic meter of fresh water production was 1.82 for the waste heat utilizing type, 2.54 for the dual purpose MSF and 5.44 for thesingle purpose. Exergy input per cubic meter of fresh water as a measure of conservation was 29.3 kW for the waste heat utilizing type and 14.1 kW for the standard MSF. The inferior evaluation for the waste heat utilizing type could be attributed to the account of exergy in waste heat.
