Pressure driven adsorption cycle integrated with thermal desalination

Abstract

The canned food market is growing at an annually average rate of 3.6% due to easy access and awareness of dietary requirements, leading to a surge in water withdrawal and an estimated supply-demand gap of 40% by 2030. The conventional desalination processes are not sustainable due to high energy requirements and chemicals injection. The adsorption cycle is an emerging technology for desalination due to its temperature operation. It has many advantages over conventional desalination processes including integration synergy to improve overall performance. The conventional AD cycle processes, however, have lower performance due to inefficient packing of adsorbent in the beds and heat transfer losses to their massive heat exchangers. In this article, we propose an innovative pressure driven adsorption (PDAD) cycle to overcome conventional AD cycle limitations. In PDAD, firstly, low pressure steam is used to regenerate the adsorbent which eliminates the huge infrastructure requirement of water circulation and secondly, steam selectively extracts water vapours from pores, reducing energy consumption. We have tested the PDAD pilot and showed successful regeneration of silica gel at motive steam pressure of 2–5 bar. We also demonstrate that discharge steam from the PDAD at 65 °C can be used as a heat source for a multi effect desalination system when operating in hybrid mode to overcome its operational limitations. Our experiments show that the MED + PDAD cycle increases water production by up to 22% as compared to an earlier hybrid MEDAD cycle. The proposed system has excellent thermodynamic synergy with the combined CCGT power and desalination plant, where low-pressure bleed steam can be utilized more efficiently.

Keywords

• Pressure driven AD cycle
• Hybrid desalination
• Sustainable water supplies
• Solar desalination
• Multi effect desalination