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Membrane distillation for desalination and removal of volatile organic compounds from water.

机译：膜蒸馏用于脱盐和从水中去除挥发性有机化合物。

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Membrane distillation, a process in which vapor from a liquid feed passes through the pores of a hydrophobic membrane, was investigated as a possible technique for desalination and for the removal of ethanol, acetone and benzene from water. Three different membrane modules were used in the experiments examining the impact of operating variables upon permeate flux and quality. A mathematical model was developed and validated for the membrane distillation process.;In the desalination study, two modules with built-in condensing surfaces were used for conducting experiments on flat membrane sheets. The quality of the permeate, quantified by conductivity measurements, and the permeate flux were monitored as feed concentration, feed temperature, feed flow rate, cooling temperature, and cooling water flow rate were varied. The effect of the distance between the membrane and condensing surface was investigated by adjusting the air gap within one of the modules. The feed streams tested included sodium chloride solutions and artificial seawater. The membrane materials used were PVDF and PTFE. At optimal conditions, fluxes as high as 26 kg/m;A flat-sheet cross-flow module was used to study the separation of dilute solutions of ethanol and acetone. The same operating parameters tested in the desalination experiments were varied for ethanol and acetone feeds. The upper feed concentrations tested were limited by the risk of membrane wetting to 10 wt% ethanol and 6 wt% acetone. Within the feed temperature range of ;A mathematical model, based on first principles of heat and mass transfer, was developed and validated on the desalination, ethanol, and acetone experimental data. Good agreement between experimental and predicted values was obtained with the model version incorporating temperature and concentration polarization.;The possibility of using vacuum membrane distillation for treating water contaminated with volatile organic compounds was investigated by using benzene as a model compound. An experimental unit with polypropylene membrane tubes fitted within a polypropylene shell was used in the tests. Dilute benzene solutions were pumped through the lumen of tubular membranes while vacuum was applied to the shell side. The data obtained by varying operating conditions was analyzed in terms of the overall mass transfer coefficient based on the film theory. A comparison between the effectiveness of membrane distillation and air-stripping was drawn based on a published case study. The experimental unit with tubular membranes failed to compete but extrapolations to higher membrane contact areas showed promise for hollow fiber modules.
机译：膜蒸馏是一种使液体进料中的蒸气通过疏水膜孔的工艺，它被研究为一种脱盐以及从水中除去乙醇，丙酮和苯的可行技术。实验中使用了三种不同的膜组件，以检查操作变量对渗透通量和质量的影响。为膜蒸馏过程开发了一个数学模型并进行了验证。；在脱盐研究中，使用两个带有冷凝表面的模块在平坦的膜片上进行实验。随着进料浓度，进料温度，进料流速，冷却温度和冷却水流速的变化，通过电导率测量定量的渗透物质量和渗透通量被监测。通过调节模块之一内的气隙，研究了膜与冷凝表面之间距离的影响。测试的进料流包括氯化钠溶液和人造海水。使用的膜材料是PVDF和PTFE。在最佳条件下，通量高达26 kg / m；使用平板错流模块研究乙醇和丙酮稀溶液的分离。对于乙醇和丙酮进料，在脱盐实验中测试的相同操作参数有所不同。测试的最高进料浓度受到膜润湿至10 wt％乙醇和6 wt％丙酮的风险的限制。在进料温度范围内；基于传热和传质的首要原理，建立了数学模型，并根据脱盐，乙醇和丙酮的实验数据进行了验证。使用结合了温度和浓度极化的模型版本，在实验值和预测值之间取得了良好的一致性。；以苯为模型化合物，研究了使用真空膜蒸馏法处理被挥发性有机化合物污染的水的可能性。在试验中使用了具有安装在聚丙烯壳内的聚丙烯膜管的实验装置。将稀苯溶液泵送通过管状膜的内腔，同时在壳侧施加真空。根据膜理论，根据总传质系数分析了通过改变操作条件获得的数据。基于已发表的案例研究，对膜蒸馏和空气汽提的有效性进行了比较。带有管状膜的实验装置无法竞争，但外推至更高的膜接触面积显示出中空纤维组件的前景。

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