PRAYOG LABS LLC — Department of Energy SBIR Phase II: C45-20a

Description

Water scarcity continues to affect people in the USA and around the globe. This scarcity is exacerbated by the dramatic increase in water usage due to urbanization and industrialization. The volume of high salinity wastewater, like those generated by hydraulic fracking, continues to grow and its treatment is a major environmental challenge. The recycling and reuse of water and salts from high salinity waste streams would help the environment as well as provide economic incentives. The purpose of this program is to commercialize an advanced supercritical water treatment (SCWT) process by further reducing the cost and energy consumption. By pressurizing and heating water to its supercritical state (sH2O), salts and metal inorganics are removed through precipitation and biological matter is rendered harmless. Additionally, the high energy density of the SCWT process makes the equipment compact and transportable. While these advantages of sH2O processing are known, several technical problems, including the high cost of heating and pressurizing water, have prevented the process from becoming commercial. In Phase I and II, the focus was on overcoming technical problem like salt plugging, corrosion, and energy usage, and then implementing the solutions into a continuous SCWT system. The SCWT system was operated extensively collecting data on the effect of operational settings on sweet water properties, energy usage, and cost. System parameters were optimized to make the process technically viable and commercially feasible. The SCWT system uses a novel, highly efficient, and compact heat exchanger to reduce energy consumption and has shown efficacy in producing potable water, by removing salt from high salinity streams, ranging from 3.5wt% to 18wt%. The SCWT system was operated for over 1200 hours. The data was used to upgrade system components for stable operation, without salt plugging, using materials that minimize the impact of corrosion. The technical focus of Phase IIB is to achieve additional energy saving by recovering compression energy used to pressurize the water to the supercritical conditions. During the program, the team will design, fabricate, and test a novel energy recovery device (ERD) capable of recovering 95% of the SCWT system’s compression energy. This is a similar approach to that used in reverse osmosis systems, but at significantly higher pressures. The ERD will first be built and tested at a lab prototype scale to optimize the design and performance.