负压—气隙式和多级膜蒸馏装置及其于含盐水蒸发过程的研究

发布时间：2018-02-08 19:00

  本文关键词： 气隙式膜蒸馏 真空膜蒸馏 过程优化 多级能量回收 PTFE中空纤维膜　出处：《浙江大学》2016年博士论文　论文类型：学位论文

【摘要】：膜蒸馏(MD)是正在发展中的一种新型膜技术,在浓海水的淡化、含盐水的浓缩、高盐水的资源化处理等方面具有潜在应用前景。本研究使用具有高孔隙率、高疏水特性PTFE中空纤维膜,设计并研制出渗透侧负压气隙式膜蒸馏(V-AGMD)装置。通过考察在负压条件下的气隙式膜蒸馏性能、在不同进料温度、流速、盐浓度及冷凝液温度条件下,V-AGMD和AGMD的运行性能比较,以及通过正交试验,进行V-AGMD和AGMD的最优运行条件的考察等,所得结论如下：1.研究使用具有高孔隙率、高疏水性的PTFE中空纤维膜,并设计出新型的膜元件,此膜元件以多孔的中空纤维膜内腔为待蒸发含盐溶液的流道,用无孔的中空纤维内腔为冷凝水的流道,用于构建气隙式膜蒸馏(AGMD)装置,该装置最大程度避免了膜的亲水化现象发生,提高了膜元件使用寿命,为膜蒸馏过程的稳定运行、过程放大应用奠定基础。2.通过在渗透侧辅加真空泵,所设计的负压-气隙式膜蒸馏装置,用于膜蒸馏的蒸发实验。在进料液温度为80℃,盐浓度为0.0253%,冷凝液温度为20℃时,随进料液流速由2增加到4 L/min, PR和η分别提高了15.25%和11.99%；在进料液流速4 L/min,温度50℃下,PF和GOR分别增加了24.96%和14.29%。该结果说明有效地提升了AGMD的运行性能。该试验结果表明,负压-气隙式膜蒸馏装置能有效提高膜蒸馏过程的蒸发通量(PF)、热效率(η),增益膜蒸馏的输出比率(GOR)和性能比(PR)。3.通过正交实验,获得了不同操作条件下的最优值。在进料液温度80℃,流速4 L/min,盐浓度0.0253%。在此条件下,获得了最高的PF和η。在进料液温度为70℃,流速2 L/min,盐浓度1.6335%的条件下,获得了AGMD过程最高的PR和GOR值。对于V-MEMD过程,在80℃、4 L/min、0.0253%的条件下获得了最优的PF、η和PR的值,而最优的GOR则在80℃、2L/min、4.4825%的条件下获得。进一步设计出的具有多级能量回收功能的多效膜蒸馏(MEMD)装置,用于对含盐水溶液的膜蒸馏试验研究。试验结果表明：在高能耗的V-MEMD过程中辅加一级能量回收单元,能有效地提高V-MEMD的渗透流量并降低能耗；同时设计了具有三级能量回收单元的V-MEMD装置,并进行二种装置运行性能的比较,所得结论如下：1.所设计的具有一级能量回收单元的V-MEMD膜蒸馏过程,试验结果表明：PF, PR和GOR均有所提升,能耗(EC)/m3有所下降。与一级的V-MEMD过程相比,三级的V-MEMD过程,具有更高的运行性能并降低能耗,有效地提高了V-MEMD过程的效率。2.对于具有三级能量回收单元的V-MEMD膜蒸馏过程,当进料流速400L/hr,渗透侧真空度0.085MPa,进料温度80℃和盐浓度为5.71%时,其V-MEMD过程的PF, PR和GOR均有明显提高。3.对于具有三级能量回收单元的V-MEMD膜蒸馏过程,当进料盐浓度由5.71%上升到19.60%时,V-MEMD过程对潜热明显提高,热能回收率在17.32%与34.92%之间,电能回收率则提高到86.85%到91.50%之间。4.实验结果表明,与一级的V-MEMD过程相比,三级的V-MEMD过程有更高性能和更低的能耗,且引入能量回收过程有效地提高了V-MEMD过程的效率。
[Abstract]:Membrane distillation (MD) is a new type of membrane technology is being developed and in the desalination of sea water, concentrated salt, has potential application prospects of saline water resource treatment. This study has high porosity, high hydrophobic properties of PTFE hollow fiber membrane, designed and developed the permeate side pressure gas gap membrane distillation (V-AGMD) apparatus. Through the investigation of air gap membrane distillation performance under the condition of negative pressure, at different feed temperature, flow rate, salt concentration and condensate temperature conditions, comparison of performance of V-AGMD and AGMD, and through the orthogonal test, the optimum operating conditions for V-AGMD and AGMD inspection etc. the conclusions are as follows: 1., research with high porosity, high hydrophobic PTFE hollow fiber membrane, and the design of a new membrane element and the membrane element with hollow fiber porous cavity for passage to vaporize the salt solution, with empty holes Fiber lumen for condensate flow, for the construction of air gap membrane distillation (AGMD) device, the device maximum avoid the phenomenon of hydrophilic membrane, improve the service life of the membrane element, for the stable operation of membrane distillation process, amplification.2. lay the foundation by adding the permeate side vacuum pump, negative pressure the design of air gap membrane distillation device for evaporation experiment of membrane distillation. The feed liquid temperature is 80 DEG C, the concentration of salt is 0.0253%, the condensate temperature is 20 degrees centigrade with feed liquid velocity increased from 2 to 4 L/min, PR and N were increased by 15.25% and 11.99%; in the liquid flow rate was 4 L/min, the temperature of 50 DEG C, PF and GOR were increased by 24.96% and the results show that 14.29%. effectively improve the performance of AGMD. The test results show that the negative pressure air gap membrane distillation device can effectively improve the evaporation flux of membrane distillation (PF), thermal efficiency (ETA). Increase The output rate of benefit of membrane distillation (GOR) and the performance ratio (PR).3. by the orthogonal experiment, the optimal under different operating conditions. The value of feed liquid at 80 degrees Celsius temperature, flow rate of 4 L/min, the salt concentration of 0.0253%. under this condition, obtained the highest PF and ETA. In the feed temperature is 70 C, a flow rate of 2 L/min, the concentration of salt under the condition of 1.6335%, PR and GOR got the highest AGMD value for the V-MEMD process. In the process, 80 C, 4 L/min, 0.0253% under the condition of optimum PF, ETA and PR values, and the optimum GOR at 80 DEG C, 2L/min, 4.4825% conditions. Further designed with multistage energy recovery function of multi effect membrane distillation (MEMD) device for experimental research on membrane distillation of aqueous solution containing salt. The experimental results show that adding a level of energy recovery unit in the V-MEMD process, high energy consumption, can effectively improve the penetration of V-MEMD flow at the same time and reduce energy consumption; The V-MEMD device has a three energy recovery unit, and compared two kinds of device performance, the conclusions are as follows: 1. the design of a energy recovery unit V-MEMD membrane distillation process, the results show that PF, PR and GOR have improved, energy consumption (EC) decreased. Compared to /m3 with the V-MEMD level, V-MEMD level three, with higher operating performance and reduce energy consumption, improve the efficiency of.2. V-MEMD process for V-MEMD membrane distillation process with three levels of energy recovery unit, when the feed rate of 400L/hr penetration side vacuum 0.085MPa, feed temperature and 80 DEG C when salt concentration was 5.71%, the V-MEMD PF, PR and GOR were significantly increased in.3. V-MEMD membrane distillation process with three levels of energy recovery unit, when the feed concentration increased from 5.71% to 19.60%, V-MEMD of latent heat is obviously improved, the heat energy The recovery rate is between 17.32% and 34.92%, energy recovery rate is increased to 86.85% to 91.50%.4.. The experimental results show that compared with the V-MEMD level, V-MEMD level three has higher performance and lower power consumption, and the energy recovery process can effectively improve the efficiency of the V-MEMD process.

【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TQ028.8
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本文编号：1496042