ASSESSMENT OF MSF-EVAPORATOR DESIGN WITH REDUCED COOLING WATER REQUIREMENTS.

The effect of reducing cooling water flow to a multi-stage-flash (MSF) evaporator on the required heat transfer areas, the heat input, temperature distributions and power requirements, was investigated. Case studies were made by computer simulation of plants with 10,000 t/d capacity and performance ratios 6 and 10. Any reduction of seawater demand achieved by modifications in the heat rejection section will raise the cold-end temperature of the evaporator. The benefits of a reduction lie in size and cost savings for the intake structure, transfer pumps, feed and discharge piping, settling basins, screening, filtration and chlorination. Intake reductions to 60% of the recirculation rate will raise either the heat input or heat transfer areas, as well as the costs for some accessory components, by roughly 5%. Further reductions are penalized by very rapid degradation of plant characteristics.