Synthesis of water capture technologies for gas fired power plants in Qatar

Abstract

Flue gas from gas fired power plants contains 10-16% (w/w) water vapor with considerable amount of latent heat. Although CO2 capture and utilization have received great attention, water capture from power plant has received limited attention. The power plants in Qatar exhaust 33 Million m3 of water per year. This paper explores selected alternative technologies namely absorption, compression & cooling, and quenching, to enable the recovery of water vapor contained in a base case 750 MW power plant flue gas streams. The alternatives for water capture were modeled and optimized over a wide range of operating conditions (pressure, temperature, and flow rate). Using data from an actual gas fired power plant in the state of Qatar, simulation studies were carried out and optimized for all modeled technologies to minimize production cost using Aspen HYSYS V8.6. The results show that the quench unit, operated at pertinent water circulation temperature (50 C), pressure (6 atm), and flowrate of 3500 m3/h (recyclable), can extract up to 80.7% of the water in the flue gas. Apart from production cost and water capture percentage, criteria used to screen the alternative technologies were payback period, CO2e emission and brine reduction rate. The research work determined that the quench alternative had the lowest payback period (8.8 years), lowest CO2 emission rate (13 kg CO2/m3 H2O) and highest brine reduction (3.44%) among all the tested alternatives. The proposed quench water-recovery technology will have added value to Qatar and other nations with limited water resources, specifically those with access to natural gas resources. 2019