煤制烯烃含盐废水近零排放技术的应用

Application of near-zero liquid discharge technology of brine wastewater in coal to olefin industry

与石油、天然气相比,我国煤炭资源更加丰富,发展新型煤化工产业是大势所趋。煤炭和水资源的逆向分布导致煤化工企业所在地水环境问题尤为突出。常规处理工艺难以实现废水达标排放和资源回用目标,需通过特定的近零排放技术工艺,将浓盐水进一步浓缩至盐结晶,产水全部回用,结晶盐外排作为固废处置。本文结合工程实例,介绍了某煤化工项目针对生产过程中产生的含盐废水所采取的近零排放处理工艺技术路线,其主要由含盐废水膜处理单元和浓盐水蒸发结晶单元组成。采用机械蒸汽压缩循环、强制循环降膜蒸发、高效传热和盐种等技术,同时对蒸发结晶近零排放系统进行改进和优化。装置实际运行结果表明:各项工艺参数指标及药剂和能源消耗量均达到设计要求,产水水质达到优质再生水回用标准,实现整套装置长周期稳定运行及废水近零排放目标。

The development of new coal chemical industry is the general trend due to the richer coal resources comparing to oil and natural gas in China.The reverse distribution of coal and water resources results in significant water problems in the region of coal chemical enterprises,which is difficult to achieve the target of wastewater discharge and resource reuse.It’s necessary to further concentrate brine wastewater to salt crystals through specific near-zero liquid discharge process,recycling all produced water and discharging crystal salt as solid waste.This article introduced the general technical route of near-zero liquid discharge process for the brine wastewater treatment in a coal chemical industry project through a real engineering example that was mainly composed of the membrane treatment unit for the brine wastewater treatment and the evaporation crystallization unit for the concentrated brine wastewater treatment.Several techniques,for instance,mechanical vapor recompression(MVR),forced circulation falling film evaporation,high-efficient heat transfer,salt species were used to improve and optimize the evaporative crystallization near-zero discharge system.The results showed that all operational parameters and the consumption of chemicals and energy could meet the designing target.The produced water could meet the reuse standard of high-quality recycled water.The long-term stable operation and near-zero liquid discharge were achieved in this study.