Conceptual design of an improved ammonia refining process for coal chemical wastewater

Abstract

A large amount of wastewater will be produced in the process of coal chemical production, which has always been one of the most challenging wastewaters to treat. In the actual industry, the phenol ammonia recovery process is mainly used to reduce the content of pollutants in wastewater, and ammonia is recovered as a by-product. Due to the high impurity content in the wastewater, the current process can only produce ammonia with a purity of 98 wt%, which does not meet industrial production requirements. Based on this, a new cascade purification process for by-product ammonia in coal chemical wastewater was proposed and conceptually designed. The results show that 99.8 wt% liquid ammonia can be produced by ammonia washing-ammonia distillation, and 20 wt% ammonia aqueous solution can be produced by ammonia washing-low temperature purification. Both refining methods can reduce inorganics, organics, and oils to <5 mg/L, 35 mg/L, and 10 mg/L, respectively, and the total content of impurities is <50 mg/L, which can produce ammonia products in line with actual industrial production. This work successfully solves the shortcomings of coal chemical wastewater's current ammonia recovery process and has a good application prospect.