Supercritical water fuel cleaning for improved combined cycle performance

A revolutionary hydrothermal heat recovery steam generator (HRSG) is being developed by a federal, state university and industry partnership to produce clean fuels for gas turbines. The patented hydrothermal HRSG will accept solutions and emulsions without corrosion and deposition on heat transfer surfaces. An advanced continuous-flow pilot plant is being designed to test the HRSG over a wide range of operating conditions, including the supercritical conditions of water, above 221 bar (3205 psia) and 374 C (705 F). Water at these conditions can be used to clean emulsions of crude oil, composted refuse derived fuel, coal fines, and coal water fuels. Data shows that fuel nitrogen will be converted to nitrogen gas. Inorganic materials, such as sulfur, chlorine, alkali metals, ash, vanadium and other metals can be separated and removed for recycle or disposal. Carbon can be sequestered in char for decreased carbon dioxide emissions and activated for use as an adsorbent. Combining the new HRSG with a special condensing turbine and a modern gas turbine promises to increase power output, efficiency, availability and reliability in a new Vapor Transmission Cycle (VTC). The condensing turbine reduces the pressure of steam and fuel vapor to the gas turbine combustor inlet pressure,more » driving a generator and high-pressure feed pump. The condensing turbine reduces the temperature for final removal of contaminants while maintaining combustibility of the vapor for high turbine inlet temperature. Water is condensed for recycling to the process, eliminating water treatment costs and effluents. An Engineering Study is being prepared at the University of North Dakota Energy and Environmental Research Center (EERC). An Aspen Technology, Inc. computer-based process simulation model has been prepared in collaboration with a consultant from the Los Alamos National Laboratory and EERC. The process simulation model includes materials and energy balances that simulate commercial-scale operations for system optimization, using test data. Preliminary bench-scale test data at subcritical conditions for lignite, refuse derived fuel, and tire rubber are presented, including yield data incorporated in the process model. The model has been used to compare the VTC to commercially available technologies. These results are presented, with conclusions affecting the design of the pilot plant.« less