Desalination of Brine and Produced Water by Direct Contact Membrane Distillation At Lower As Well As Higher Temperatures and Pressures

NAMS, Annual Meeting 2012, New Orleans, LA

 

Desalination of brine and produced water by direct contact membrane distillation at lower as well as higher temperatures and pressures

Dhananjay Singh and Kamalesh K. Sirkar

Otto H. York Department of Chemical, Biological and Pharmaceutical Engineering

New Jersey Institute of Technology

Newark, NJ-07102

 

Abstract. Direct contact membrane distillation (DCMD)-based desalination process is a thermally-driven separation process where a hydrophobic microporous membrane separates a hot brine feed and a cold distillate which condenses the water vapor from the hot brine passing through the membrane pores. So far, DCMD has been explored for hot brines and other aqueous solutions below 100^oC. For feed solutions above 100^oC, DCMD has an extra advantage over other conventional separation processes like reverse osmosis (RO) which requires cooling of the feed solution costing additional energy; further RO can not utilize the heat available in the feed solution. Produced water obtained from steam assisted gravity drainage (SAGD) process is one such example where DCMD can potentially be a very useful process. In this work, the DCMD technique is explored in the range of 80-130^oC for brine solutions containing 10000 ppm sodium chloride with porous flat sheet polytetrafluoroethylene (PTFE) membranes. The pressure of solution went up to 2-3 atm. There was no leakage of salt under any conditions. The highest water vapor flux achieved was 195 kg/m²-hr, which is a few times larger than that for seawater RO process. The performance of this membrane has also been explored with a saline feed containing 3000 ppm NaCl, 45 ppm phenol, 45 ppm cresol and 10 ppm naphthenic acid, simulating the composition of hot produced water obtained from the SAGD process. Different types of hollow fiber modules were also fabricated and explored with 1% NaCl solution and produced water at lower as well as higher temperatures. The water generated by the DCMD process may be used for steam generation in the SAGD process.