The development of high-performance distillation plants

Abstract

At present, MSF plants are the most reliable source for the production of fresh water from the sea and all major plants are built according to this principle. Compared to reverse osmosis, the specific prime energy consumption of MSF processes is high even if the plants are designed as dual purpose plants. Substantially lower prime energy consumptions in distillation can be achieved by the ME-principle. Despite its thermodynamical advantages, only few and small ME plants exist, mainly because the ME process in its conventional design is rather complex. Its stacked version however, which has been first introduced by Takada, can combine the low prime energy consumption of RO and the inherent simplicity of the MSF process. Multiple effect stack units can be operated with very small driving-forces. Consequently MES processes can be designed comprised of a very high number of effects without increasing the top brine temperature to figures above 115 – 120 °C. The paper reports the results of experiments with different evaporator designs and the influence of brine distribution and venting of non condensables on the performance of such MES-processes. Furthermore, conceptual design for waste heat utilisation and for vapor compression units will be discussed.