平流式多效真空膜蒸馏过程的实验研究

Experiment study on advection multi-effect vacuum membrane distillation(ME-VMD)process

利用疏水性聚四氟乙烯(PTFE)中空纤维膜和PTFE毛细管换热器耦合组成的四效平流式真空膜蒸馏系统(ME-VMD)进行实验研究,重点考察了进料温度、进料流速和透过侧绝对压强对各效的膜通量和热效率及系统的产水量和造水比(GOR)的影响.实验结果表明,ME-VMD系统的效间温差随进料温度的升高而增大,随效数的增大而减小,系统的最佳效数与料液进口温度有直接关系;较高的进料温度、较低的料液流速及尽可能低的透过侧绝对压强均有助于膜通量、产水量及造水比的提高;而热效率则随进料温度的升高而逐步升高,随透过侧绝对压强及料液流速的升高而降低.当进料为温度90℃时,可采用四效真空膜蒸馏;当进料流速为0.30m/s,透过侧绝对压强为3kPa时,其造水比可达到2.15.

An experimental investigation was carried out by using advection multi-effect vacuum membrane distillation （ME-VMD） system containing hydrophobic PTFE hollow fiber membrane and PTFE capillary heat exchanger. The effect of feed temperature, feed velocity and vacuum degree on the transmembrane flux, thermal efficiency and gained-output-ratio （GOR） were investigated. The experimental results show that the temperature difference loss increases with the increase of feed temperature, and decreases with the increase of the effect number. The best effect number has a direct relationship with the feed temperature. High feed temperature, low flow rate and the high vacuum degree contribute to the improvement of transmembrane flux, water yield and GOR. The thermal efficiency increases with the increase of feed temperature and vacuum degree and declines with the increase of feed velocity. When the feed temperature, the feed velocity and the absolute pressure at the permeate side is 90 ℃, 0. 30 m/s and 3 kPa, respectively, four effect ME-VMD can be used, and the GOR can get to 2. 15.