Cooling and recycling acid effluents - with recovery of heat in useable form

摘要

Acid effluents, e.g. from the extraction of zinc, are cooled to recover heat produced by exothermic reaction. The acid is passed through a liquid/liquid heat exchanger, the acid side plates anodically protected. The entry temperature is between 100 and 130 deg.C, and the exit between 84 and 114 deg.C. Cooled acid is recycled. Water from the other side passes to a separator sphere, and is evaporated under partial vacuum. Vapour passes to a multistage compressor, with water injection to saturate it after each stage. It emerges at 2.7 bar pressure, and 134 deg.C made-up residual water from the separator is returned to the heat exchanger. (8pp) Typically these effluents are passed through a cooling tower, wasting the heat extracted. In this installation, it is recovered and converted into a form where it provides a useful auxiliary heat source.