Process Development, Simulation, and Industrial Implementation of a New Coal-Gasification Wastewater Treatment Installation for Phenol and Ammonia Removal

Coal-gasification wastewater poses serious problems in the Lurgi process. It cannot be easily purified, as the high pH value of the wastewater limits the dephenolization efficiency of extraction. This work proposes a new process to remove ammonia and sour gas in order to reduce the pH value of the wastewater from 9 to below 7, and next to remove phenol with solvent extraction under acidic conditions. This new process consists of a wastewater stripper with side-draw to remove ammonia and sour gas, an extractor to remove phenol, and two distillation columns to recover extractant. Process simulation was conducted to study the performance of the new process and to perform a detailed design. The complex multicomponent system NH3-CO2-H2S-NaOH-phenol-H2O was analyzed when simulating the wastewater stripping. The new process has been successfully implemented in ail industrial installation for coal-gasification wastewater treatment with a capacity of 2000 tons/day. Satisfactory agreement was obtained between the simulation results and the industrial implementation of the new process. The new process, when compared with the old one, recovers phenols more efficiently and produces a wastewater stream acceptable for later biological treatment.