Experimental study on vacuum membrane distillation system of hollow fiber coupled with mechanical vapor recompression

Abstract

In order to solve the problems of low separation efficiency and high energy consumption in the industrial wastewater treatment, a combined system of mechanical vapor recompression and hollow fiber vacuum membrane distillation was constructed. The operational characteristics of the coupled system were investigated, and experimental studies were conducted on the evaporation of ammonium chloride solution under different feed conditions and long-term operation. The results indicated that as ammonium chloride mass concentration, feed temperature, feed flow rate and vacuum side pressure were 5%, 75 ℃, 10 m3/h and 24 kPa, the freshwater production ratio, freshwater conductivity, separation efficiency and specific heating energy consumption(SHEC) were obtained as 45.9 kg/h, 11.9 μS/cm, 99.9% and 118.5 kW·h/t. In addition, the increase of ammonium chloride mass concentration decreased the freshwater production ratio and increased the SHEC, while the increase of feed temperature and feed flow rate increased the freshwater production ratio and decreased the SHEC. After 240 h of long term operation, membrane fouling did not significantly affect the freshwater quality, but reduced the freshwater production ratio. The water production rate was restored to 96.1% of the original through membrane cleaning. The system can separate the ammonia chloride solution with high efficiency and has a broad application prospect.

Keywords

• mechanical vapor recompression
• hollow fiber
• vacuum membrane distillation
• freshwater production ratio
• separation efficiency
• specific heating energy consumption