New MED based desalination process for low grade waste heat

Abstract

We have developed a new distributed boosted multi-effect distillation (DBMED) process to effectively harness low-grade “waste heat” in the temperature range 65°C–90°C to address the problem of freshwater scarcity. Comparisons are made with multi-effect distillation (MED) and recently proposed advanced MED schemes, namely boosted MED (BMED) and flash boosted MED (FBMED) on the basis of waste heat performance ratio, normalised pumping power consumption (NPPC) and specific capital cost. The main advantage of DBMED compared to FBMED, is a 30.9% decrease in the average NPPC. Compared to FBMED, which has the highest waste heat performance ratio of systems described in the literature to date, DBMED has a similar average waste heat performance ratio and specific capital cost over the temperature range 65°C–90°C. For driving temperatures lower than 75°C, DBMED has a better waste heat performance ratio by up to 7.3% while also reducing NPPC by at least 22%. At temperatures above 75°C, the waste heat performance ratio of DBMED is greater than those of MED and BMED but less than that of FBMED by ≤4.5%, while having the advantage of up to 38% reduction in NPPC at 90°C.