气隙式膜蒸馏在溴化锂吸收式制冷系统中的应用

doi:10.16085/j.issn.1000-6613.2019-0576

摘要/Abstract

摘要：

以1H, 1H, 2H, 2H-全氟癸基三乙氧基硅烷（PFDTES）为改性剂，采用表面接枝方法制备疏水性PFDTES-Al₂O₃管式复合膜，并将其应用于溴化锂吸收式制冷系统。通过LiBr/H₂O溶液的气隙式膜蒸馏实验，测试管式复合膜对溶液的分离性能。结果表明：通过PFDTES成功制备出疏水性PFDTES-Al₂O₃管式复合膜；膜蒸馏渗透通量随着操作压力、进料温度及进料流量的增大而增大，随着进料浓度的增大而减小；对于LiBr的截留率始终保持在99.99%以上。在膜蒸馏实验结果的基础上，进一步利用Aspen Plus软件模拟了基于PFDTES-Al₂O₃复合膜的新型溴化锂吸收式制冷系统的换热过程，研究该复合膜应用于溴化锂吸收式制冷系统的可行性。结果表明：性能系数（COP）随着LiBr/H₂O稀溶液浓度及流量的增大而减小，随着LiBr/H₂O稀溶液温度的升高而增大；并且LiBr/H₂O稀溶液温度及流量是主要的影响因素。在操作压力0.08MPa、LiBr/H₂O稀溶液流量86L/h、质量分数50%、温度＞70℃、冷侧流量120L/h和温度20℃的条件下，COP＞0.7，说明将PFDTES-Al₂O₃复合膜用于溴化锂吸收式制冷系统，不仅可以减小设备的体积，还能降低运行成本，具有较高的可行性。

关键词: Al₂O₃陶瓷膜, 膜蒸馏, 溴化锂吸收式制冷, Aspen Plus模拟, 性能系数

Abstract:

Hydrophobic PFDTES-Al₂O₃ tubular composite membrane was prepared by grafting with 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTES) and applied to lithium bromide absorption refrigeration system. The separation performance of the tubular composite membrane for LiBr/H₂O solution was tested by the air gap membrane distillation (AGMD) experiment. The results showed that hydrophobic PFDTES-Al₂O₃ tubular composite membranes were successfully prepared with PFDTES. The permeation flux of membrane distillation increased as the operating pressure, feed temperature and feed flow rate increased and decreased with the increase of feed concentration. The rejection rate of LiBr remained above 99.99%. Based on the results of AGMD, the heat transfer process of a novel lithium bromide absorption refrigeration system including PFDTES-Al₂O₃ tubular composite membrane was simulated by Aspen Plus, and the feasibility of applying PFDTES-Al₂O₃ composite membrane to lithium bromide absorption refrigeration system was studied. The results showed that the coefficient of performance (COP) decreased with the increase of concentration and flow rate of LiBr/H₂O solution and increased with the increase of temperature of LiBr/H₂O solution. Moreover， the temperature and flow rate of LiBr/H₂O solution were the main influencing factors. When the operating pressure was 0.08MPa, the flow rate of LiBr/H₂O solution was 86L/h, the mass fraction was 50%, the temperature of LiBr/H₂O solution was more than 70℃, the flow rate of cold side was 120L/h and the temperature was 20℃, the COP was more than 0.7. It was shown that the application of PFDTES-Al₂O₃ tubular composite membrane in lithium bromide absorption refrigeration system not only reduces the volume of the equipment but also reduces the cost and has high feasibility.

Key words: Al₂O₃ ceramic membrane, membrane distillation, lithium bromide absorption refrigeration, Aspen Plus simulation, COP

中图分类号:

TQ02

李恋,陈志,杨进飞,王计辉,李建明. 气隙式膜蒸馏在溴化锂吸收式制冷系统中的应用[J]. 化工进展, 2020, 39(1): 80-88.

Lian LI,Zhi CHEN,Jinfei YANG,Jihui WANG,Jianming LI. Application of air-gap membrane distillation in lithium bromide absorption refrigeration system[J]. Chemical Industry and Engineering Progress, 2020, 39(1): 80-88.

图/表 18

图1 AGMD实验装置

图2 LiBr/H2O溶液浓度与电导率的关系

图3 传统单效溴化锂吸收式制冷系统流程

图4 PFDTES疏水改性Al2O3陶瓷膜过程

图5 Al2O3陶瓷膜改性前后红外光谱图

图6 2000倍率Al2O3陶瓷内膜表面的SEM图

图7 改性后的Al2O3陶瓷膜表面EDS元素分析

图8 Al2O3陶瓷膜改性前后纯水通量

图9 操作压力对渗透通量以及LiBr截留率的影响

图10 进料浓度对渗透通量以及LiBr截留率的影响

图11 进料温度对渗透通量以及LiBr截留率的影响

图12 进料流量对渗透通量以及LiBr截留率的影响

图13 新型单效溴化锂吸收式制冷系统

图14 Aspen Plus中新型单效溴化锂吸收式制冷系统模拟流程图

表1 制冷循环模拟参数

循环参数	数值
发生温度	60～90℃
蒸发温度	5℃
吸收器温度	38℃
冷却水进口温度	20℃
稀溶液流量	86～138L·h^-1

图15 LiBr/H2O稀溶液浓度对蒸发器冷负荷及COP的影响

图16 LiBr/H2O稀溶液温度对蒸发器冷负荷及COP的影响

图17 LiBr/H2O稀溶液流量对蒸发器冷负荷及COP的影响

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