热泵驱动井下原位制冷与膜蒸馏水处理系统性能分析

Performance analysis of combined system for underground in-situ cooling and mine water membrane distillation driven by heat pump

  • 摘要: 机械制冷降温是目前现场实施效果最佳且应用最广泛的矿井热害治理技术,然而由于井下制冷负荷大、冷凝热排放量高,仅依靠矿井排水及矿井回风等方式,难以实现低能耗、大规模的冷凝热排放。为实现制冷系统冷凝热的原位利用,结合膜蒸馏处理高矿化度矿井水技术,设计了热泵驱动井下原位制冷与膜蒸馏水处理系统。基于热力学第一定律及传热传质理论,建立了热泵系统及膜蒸馏组件的数学模型,编写了计算程序,并通过与试验结果对比,验证了模型的准确性。结果表明:随着膜蒸馏组件热流体进口温度的增加,可处理矿井水流量呈先减小后增大的趋势,能效比呈下降现象;随着压缩机入口工质过热度的增加,可处理矿井水流量及能效比基本保持不变。基于非支配排序遗传算法Ⅱ(NSGA-Ⅱ),在给定的膜蒸馏组件结构参数下,获得了最佳的系统性能,在满足3.5 MW制冷量的前提下,可处理矿井水流量为0.92 kg/s,能效比为5.81。同时,随着制冷量的增加,系统可处理矿井水流量呈线性增长趋势,而能效比基本保持不变。结合潘三矿现场情况分析,相比于井下原位制冷与蒸馏法处理矿井水方法,以及井下原位制冷与井上热泵驱动膜蒸馏处理矿井水方法,设计的方法在满足相同制冷量与可处理矿井水流量条件下,可节约至少50%的压缩机耗能,年运行成本可节省32%。

     

    Abstract: Mechanical refrigeration for mine cooling is currently the most effective and widely used heat hazard control method. However, the cooling load of mine is remarkably huge, and the condensation heat discharge is significantly high. At present, it is difficult to achieve low energy consumption and large-scale condensation heat discharge with methods such as mine drainage and return air. To achieve the efficient in-situ utilization of condensation heat of mechanical refrigeration system, membrane distillation for the treatment of highly mineralized mine water was considered, and a combined system for underground in-situ cooling and mine water membrane distillation driven by heat pump was designed. Based on the first law of thermodynamics and the theory of heat and mass transfer, the mathematical models of the heat pump system and the membrane distillation system were established, the calculation program was written, and the accuracy of the model was verified by comparison with experiments. Through the analysis of the operating parameters of the designed combined system, the following conclusions were drawn: With the increase of the inlet temperature of the hot fluid, the flow rate of treated mine water shows a trend of first decreasing and then increasing, and the Coefficient of Performance shows a downward trend. With the increase of the superheated temperature of working fluid at the inlet of compressor, the flow rate of treated mine water and coefficient of performance remain unchanged. Based on the Non-dominated Sorting Genetic Algorithm II (NSGA-Ⅱ) optimization algorithm, under the given structural parameters of the membrane distillation system, the optimal performance is obtained. On the premise of meeting the cooling capacity of 3.5 MW, the flow rate of treated mine water is 0.92 kg/s, and the value of εR is 5.81. Meanwhile, with the increase of cooling capacity, the flow rate of treated mine water shows a linear growth trend, while the value of coefficient of performance remains unchanged. For the case of Pansan Mine, compared with the in-situ refrigeration and distillation method and the in-situ refrigeration and ground membrane distillation method, the designed system can save at least 50% of the energy consumption of the compressor while achieving the same cooling capacity and the flow rate of treated mine water, which could cut down the annual operating cost by around 32%.

     

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