煤气化废水处理中双侧线汽提塔的应用

Application of double side-draw stripper process in coal-gasification wastewater treatment

针对具有较高pH值的煤气化废水,采用酸性气饱和煤气化废水能降低废水pH值,改善萃取条件后进行萃取。但萃取后的萃余液中存在大量的酸性气、氨和萃取剂。为了回收氨和萃取剂,并脱除酸性气,在原有工作基础上,采用双侧线汽提塔处理萃余液,该塔塔顶分离酸性气,上侧线回收萃取剂,下侧线回收氨。文中是这一建议流程的后续研究工作。通过流程模拟,对影响双侧线汽提塔分离效果的因素,如热进料位置和塔顶采出量、冷热进料比和冷进料温度、上侧线采出位置和采出量、下侧线采出位置和采出量等进行模拟优化。模拟结果显示:双侧线汽提塔可满足塔釜水净化的要求,且有效地分离酸性气、氨和萃取剂,最大程度地回收氨和萃取剂,初步证明了双侧线汽提塔工艺的可行性。

In order to improve the extraction condition of coal-gasification wastewater with a higher pH value, acid gas saturation was used to reduce the pH value. However, there were lots of sour gas, ammonia and extractant in the raffinate after extraction. For recycling ammonia and extractant, meanwhile removing acid gas, the process of double side-draw stripper was employed on that basis of existing work. The basic steps involved in this process are separation of acid gas from the tower top, recycling of extractant from the upper side-draw, and ammonia from the down side-draw. The follow-up of this proposal process was studied. The factors that affect the separation of double side-draw stripper, such as hot feed location, tower top distillation, cold/hot feed ratio, cold feed temperature, location and production of the upper side-draw, location and production of the down side-draw were optimized by process simulation. The results show that the process of double side-draw stripper can not only meet the waterpurification requirements of tower kettle, but also effectively separate the acid gas, ammonia and extractant. Besides, the process can achieve the maximum recovery degree of ammonia and extractant. The process feasibility of double side-draw stripper was preliminarily evidenced.