LOW GRADE WASTE HEAT DRIVEN DESALINATION AND SO2 SCRUBBING

By 2015, nearly half the world's population will live in "water stressed" areas. Production of fresh water utilizing waste heat from industrial processes has been identified globally as a research priority. About 15% of die electricity required to produce aluminum is lost as waste heat in the off-gas. However, the low temperature ( low grade) of the heat limits reuse The off-gases contain 50-150 ppm SO2; tightening regulations coupled with increasing coke sulfur levels are motivating SO2 control, for which seawater scrubbing is attractive for smelters with suitable access. We describe a process that produces fresh water, utilizing the waste heat while scrubbing SO2. It uses direct contact between seawater and off-gas to humidify the off-gas. The vapor is subsequently condensed. In smelter trials, a unit treating a slip stream produced high quality water in the anticipated quantity, attaining over 95% SO2 scrubbing. Future work involves scaling the process to be economically attractive.