机械蒸汽再压缩技术在石化废水处理系统中的应用研究

摘要

According to properties of petrochemical wastewater, the mechanical vapor recompression (MVR) process using plate evaporator with forced circulation was proposed to recycle wastewater resources. Considering the influence of the boiling point elevation and forced circulation, the complete mathematical model of MVR process was developed for process optimization and analysis, and the influence of evporation temperature, wastewater temperature and compression ratio on the MVR system performance was analyzed. The results show that, the method of atmospheric evaporation can be used to reduce the energy consumption; higher waste water temperature can result in a slight decrease in specific heat transfer area; and when compression ratio increases, specific power consuption increases, but specific heat transfer area decreases. So the compression ratio is the controlling factor that determines the heat transfer temperature difference, specific power consumption and specific heat transfer area of the MVR system, and the compression ratio plays a key role in controlling investment and operation cost of the MVR system. When waste water temperature is 45 ℃, concentrated liquid recirculated flow rate is 10 m3/h, the economical compression ratio is 1.4 to 1.6.%针对某石化废水的水质特点，提出了采用板式蒸发强制循环机械蒸汽再压缩工艺回收废水资源。在考虑浓缩液沸点升高及强制循环对系统影响的条件下，建立了 MVR 系统工艺计算数学模型，分析了蒸发温度、废水温度及压缩比对 MVR 系统的影响。模型求解结果表明：该废水采用常压蒸发，可降低系统能耗，同时高温进料有利于降低系统的总比传热面积；随着压缩比的增加，压缩机比电耗增加，而系统总比传热面积减小，且其减少的速率减缓，压缩比是控制系统传热温差、压缩机比电耗和总比传热面积的主要因素，压缩比对MVR 系统的投资和运行成本的控制起关键性作用，在废水进料温度45℃、浓缩液循环10 m3/h 的情况下，废水常压蒸发的适宜操作压缩比为1.4~1.6。