Energy Efficient Waste Heat Coupled Forward Osmosis for Effluent Water Management at Coal-Fired Power Plants

Abstract

This project sought to evaluate the technical and economic viability of the Aquapod © , a transformational low energy (<200 kJ/kg water) waste heat coupled forward osmosis (FO) technology, to manage effluents, meet cooling water demands, and achieve water conservation in a coal-fired power plant environment.The Aquapod © process is innovative because it is heat-driven, avoids the evaporation of water, and uses no toxic chemicals such as ammonia or amines. The Aquapod © process accomplishes this using an aqueous two-phase system (ATPS) coupled FO process.The evaluation revealed that the Aquapod © process offers a pathway to exploit waste heat resources within a power plant to achieve flue-gas desulfurization (FGD) wastewater volume reduction and water recovery with minimal pretreatment. Water recovery of 80% from FGD wastewater was achieved with minimal pretreatment, exceeding the project target of 50%. The estimated electrical energy of 2.16 kWh/m 3 of water produced for the Aquapod © process met the project target of < 3.6 kWh/m 3 . The heat required for the process operation was approximately 186 kJ/kg of produced water, which was slightly lower than the project target of 200 kJ/kg.The estimated treatment cost for installing and operating the Aquapod © process in conjunction with a spray dryer evaporator to achieve zero-liquid discharge (ZLD) of the 100 gpm FGD wastewater was $13.24/m 3 over a 30-year lifetime. As a point of reference, this study's host power plant currently incurs a cost of $3.70/m 3 -$8.87/m 3 on a discharged volume basis to discharge its wastewater into the publicly owned treatment works (POTW) after physicalchemical treatment. Therefore, the Illinois power plant would incur an incremental cost increase of $4.37/m 3 -9.54/m 3 to achieve ZLD using the Aquapod © and spray dryer combination.