Improving cyanide removal from coke plant wastewaters by optimizing the operation conditions of an ammonia still tower

摘要

Ammonia still tower for residual ammonia wastewater pretreatment has gained considerable application due to its high efficiencies. However, the low cyanide removal in this process is a serious environmental problem. In this paper, experiments involving full-scale studies were conducted to evaluate the stripping process for ammonia and total cyanide (TCN) removal. The optimal operating conditions of ammonia still tower were studied. Flow of alkalic solution significantly influenced the removal efficiency of cyanide. With the increase of steam flow, ammonia removal could be enhanced, but TCN removal has negligible effect. Increasing the bottom pressure of the tower proved good for improving the stripping efficiency. After combined treatment by the stripping and biological processes, the TCN concentration in the final effluent can be stable at 0.1-0.2 mg/L, which satisfies the standard.