Experimental Study Of A Novel Composite Membrane Distillation Module With Heat Recovery

China is one of the thirteen countries identified by the United Nations thatlacking fresh water most. Confronting with the situation that fresh water resources arescarce, unevenly distributed and partly polluted, seawater desalination has gained highgovernment support and been developed as an effective way to obtain fresh water.As one of the four basic types of membrane distillation configurations, vacuummembrane distillation technology has gained researchers’ great concentration due toits advantages such as high membrane flux and less heat loss compared to directcontact membrane distillation. This paper focuses on the design of a new type ofcomposite membrane module used for membrane distillation that assembles with bothflat sheet membrane and heat exchanger hollow fibers and has the function of heatrecovery inside. The effects of operating parameters such as feed temperature, feedflow rate and vacuum degree on permeate flux, salt rejection and GOR areinvestigated. The experimental results reveal that permeate flux and salt rejectionbetween level one and level two VMD distillation systems show good consistency ofthe influence of three operation parameters. The permeate flux increased with theincrease of feed temperature; feed flow rate and vacuum degree abide by differentincreasing curve rules. Compared with level one system, total distillate water outputof level two system increased while the permeate flux of which decreased. Underdifferent experimental conditions, excellent results of salt rejection higher than99.97%are obtained in both level one and level two VMD systems. The experimental resultsreveal that under certain operating parameters, compared with the temperature of feedafter flowing between the flat sheet membranes, temperature of feed arises afterflowing through the hollow fibers in the membrane modules, which demonstrate thatcomposite membrane modules designed in this paper can effectively recycle thestream latent heat in vacuum membrane distillation process. GOR is investigated toevaluate the effects of the parameters on vapor latent heat recovery of membranemodules in level one and level two VMD systems.A novel composite membrane module with heat recovery is designed in thisthesis and effective heat recovery is obtained which laid the foundation for thedevelopment of energy-saving membrane distillation technology.