Integrated treatment processes for coal-gasification wastewater with high concentration of phenol and ammonia

Abstract

Coal gasification wastewater treatment process, especially for the wastewater produced by pressurized fixed bed gasification, has already become one of the key factors which restrict the development of coal chemical industry. This wastewater has all along been regarded as one of the most difficult to be treated with because of the high concentration of phenol and ammonia in it. The most efficient treatment method is distillation and extraction. Phenols and ammonia are recovered as products. However, energy consumption, in the form of low-pressure steam and mid-pressure steam, is relatively high in this process. Technological and economic performance of the wastewater treatment process developed by South China University of Technology (SCUT) was analyzed in this paper. Two integration processes based on SCUT wastewater treatment process are proposed in which solvent recovery system is thermally integrated. The results indicate that the energy consumption via these integrations is decreased by approximately 18% compared with the conventional SCUT process. The cost of wastewater treatment can be reduced to 0.2 CNY/ton of wastewater. An on-site trial-plant is constructed to test the feasibility of the processes. The competitiveness of the technology for wastewater treatment is improved.