An innovative pressure swing adsorption cycle

Over the last century, fresh water and cooling demand have been increased tremendously due to improved living standard, industrial and economic development. The conventional air-conditioning and refrigeration processes consume 15% of total global electricity and it is expected to increase any fold due to harsh weather conditions. In terms of fresh water supplies, the current 38 billion m3 per year desalination capacity is projected to increase to 54 billion m3 per year by 2030, 40% more compared to 2016. The current business as usual trend of cooling and desalination is not sustainable due to high energy consumption and CO2 emissions. In contrast, the adsorption (AD) cycle operate at low-grade waste heat or renewable energy and produce fresh water and cooling simultaneously. The major bottleneck of conventional thermally driven AD cycle is its large foot print and capital cost due to complex packed bed arrangements. We proposed pressure swing adsorption cycle (PSAD) that can utilize low-pressure steam (2-5 bar) for regeneration using thermal vapor compressor (TVC). The proposed system has best thermodynamic synergy with CCGT plants where low-pressure bleed steam can be utilized more efficiently to produce cooling and water. In this paper, a preliminary experimental investigation on PSAD has been presented. It is successfully demonstrated that 2 bar primary steam can regenerate silica gel at less then 0.5 kPa through TVC with compression ratio 3-4 and entrainment ratio around 1-1.5. The discharge steam can be re-utilized to operate the desalination cycle, maximizing the bleed steam exergy. The proposed system will not only reduce footprint but also CAPEX and OPEX due to simple design and operation.