Utilization of waste heat in the desalination process

Several chemical, petroleum, and power plants emit water streams containing significant amounts of waste energy. A considerable amount of heat is developed in the sulphuric acid plant during sulphur burning, converting, drying and absorption stages. For example, one sulphuric plant produces cooling water at approximately 34°C. Approximately 65 MW of heat is created in a 1,000 t/d sulphur burning acid plant. This energy can be used to provide heat for desalination plants that are constructed near these sites. The most widely used desalination processes are membrane separation via reverse osmosis (RO) and three types of thermal desalination — multistage flash distillation, multiple-effect distillation, and multiple-effect distillation with thermal vapor compression. A detailed discussion on the technical developments and comparisons in the use of waste heat recovery for the three types of thermal desalination is presented. Various economic parameters used in calculating the unit production cost are presented as well as a comparative analysis of thermal desalination economics and the best utilization of waste heat.