MVR并联双效蒸发结晶系统设计及研究

利用蒸发法处理工业废水，能够实现废水的资源化利用。本文针对不同类型蒸发器适用范围受限问题，将降膜式蒸发器与强制循环蒸发器联用，提出了机械蒸汽再压缩（MVR）并联双效蒸发结晶系统。首先设计了系统的工艺循环流程并建立数学模型，对该系统及其设备进行质量和能量衡算，并对模型的可行性进行核算。随后建立系统性能的?分析模型，对常压下质量分数为5%的硫酸钠溶液蒸发结晶进行实例计算，并将其与传统三效蒸发结晶系统进行比较。通过综合能量分析与?分析，MVR并联双效蒸发结晶系统的节能程度更大，其效能系数（COP）值为21.4，相同工况下高于传统三效蒸发结晶系统82.2%，而单位能耗仅为传统三效蒸发结晶系统的17.6%；其?效率高于传统三效蒸发结晶系统51.5%，?损失则低于传统三效蒸发结晶系统24.7%，这表明MVR并联双效蒸发结晶系统热力学完善程度更高，在节能方面有较大的推广应用潜力。

Design and research of MVR parallel double-effect evaporation crystallization system

In the field of industrial waste water treatment, evaporation crystallization technology can recover raw materials for industrial production while carrying out deep treatment. It can realize resource utilization of waste water. The applicability of different types of evaporators is limited in existing research. In response to the above issue, mechanical vapor recompression(MVR) parallel double-effect evaporation crystallization system was proposed, which combined a falling film evaporator with a forced circulation evaporator. After designing the process flow, thermodynamic state of medium in each pipe segment of the system was analyzed. On this basis, mathematical model of the target system was established. It can be used to calculate mass and energy balance of the whole system and related equipment. Energy analysis of the system can also be carried out. In addition to energy analysis, exergy analysis model was also established. Taking sodium sulfate solution with a concentration of 5% at atmospheric pressure as an example, the model calculation was carried out by Matlab software. A three-effect evaporation crystallization system was introduced as a reference system. Results showed that MVR parallel double-effect evaporation crystallization system is much more energy-efficient. Its coefficient of performance(COP) is 21.4 and 82.2% higher than that of the reference system under same working condition. Its unit energy consumption is only 17.6% of the reference system. Meanwhile MVR parallel double-effect evaporation crystallization system has a higher degree of thermodynamic perfection. Its exergy efficiency is 51.5% higher than that of the reference system, and exergy loss is 24.7% lower than that of the reference system. MVR parallel double-effect evaporation crystallization system has great application potential in energy saving.