机械蒸汽再压缩蒸发系统的性能分析

机械蒸汽再压缩（MVR）蒸发系统是一种新型高效节能蒸发技术。它有多个单元设备组成，每个操作节点的控制都对系统运行的稳定性和节能效率至关重要，其中包括进料温度、蒸发压强、蒸汽压缩比、冷凝液温度等。若操作条件不当，不仅会大大降低蒸发效率而且会对设备和管路造成损害。本文建立了一套充分利用能源的MVR蒸发工艺流程，并通过理论分析对每个操作节点进行了质量和能量衡算，同时利用Aspen Plus模拟软件建立了系统的流程模拟图。通过对操作单元的变量控制，研究了循环蒸汽量、补充水的量与进料温度、冷凝液温度、蒸汽压缩比以及蒸发压强等之间的变化关系。由数据分析可得：原料在饱和液体时进料最佳，冷凝液的温度应保持与蒸发温度的有效温差在5～8 ℃时较好，压缩机的蒸汽压缩比控制在1.8～2.2较为合理。同时可利用冷凝液和浓缩液的余热对原料预热，补充水也可从冷凝液中直接取用。

Performance analysis of mechanical vapor recompression evaporation system

Mechanical vapor recompression (MVR) evaporation system is a new energy efficient evaporation technology. It has several unit devices，the system stability and energy efficiency depend on each node control，such as feed temperature，evaporation pressure，the ratio of vapor compression and condensation temperature. If the operational conditions are not appropriate，the evaporation efficiency will be reduced，and the equipment and piping will be damaged. This paper established a MVR evaporation process flow that can fully use energy. Quality and energy of each operation node were calculated，and a system of simulation process was establish using the Aspen Plus software. This research investigated the mass flow of cyclic steam and the mass flow of added water under different feed temperatures，condensation temperatures，the ratio of vapor compression and evaporation pressure，by analyzing controlling unit operations. The results showed that raw materials reached the optimal conditions in saturated liquids，temperature of the condensate to the evaporation temperature at 5—8℃ was most effective for the system，and the vapor compression ratio of compressor in the 1.8—2.2 was more reasonable. The heat from condensate and the concentrate can be used to preheat the raw material，and the added water can be drawn directly from the condensate.