Integrated supercritical water gasification combined cycle (IGCC) systems for improved performance and reduced operating costs in existing plants
A revolutionary hydrothermal heat recovery steam generator (HRSG) is being developed to produce clean fuels for gas turbines from slurries and emulsions of opportunity fuels. Water can be above 80% by weight and solids below 20%, including coal fines, coal water fuels, biomass, composted municipal refuse, sewage sludge and bitumen/Orimulsion. The patented HRSG tubes use a commercial method of particle scrubbing to improve heat transfer and prevent corrosion and deposition on heat transfer surfaces. A continuous-flow pilot plant is planned to test the HRSG over a wide range of operating conditions, including the supercritical conditions of water, above 221 bar (3,205 psia) and 374 C (705 F). Bench scale data shows, that supercritical water gasification below 580 C (1,076 F) and low residence time without catalysts or an oxidizer can produce a char product that can contain carbon up to the amount of fixed carbon in the proximate analysis of the solids in the feed. This char can be burned with coal in an existing combustion system to provide the heat required for gasification. The new HRSG tubes can be retrofitted into existing power plant boilers for repowering of existing plants for improved performance and reduced costs. A special condensing turbine allows final low-temperature cleaning and maintains quality and combustibility of the fuel vapor for modern gas turbine in the new Vapor Transmission Cycle (VTC). Increased power output and efficiency can be provided for existing plants, while reducing fuel costs. A preliminary computer-based process simulation model has been prepared that includes material and energy balances that simulate commercial-scale operations of the VTC on sewage sludge and coal. Results predict over 40% HHV thermal efficiency to electric power from sewage sludge at more than 83% water by weight. The system appears to become autothermal (no supplemental fuel required) at about 35% fixed carbon in the feed. Thus, bituminous and lignite coal slurries could be gasified at less than 25% coal and more than 75% water. Preliminary life cycle cost analyses indicate that disposal fees for sewage sludge improve operating economics over fuel that must be purchased, the cost and schedule advantages of natural gas-fired combined cycle systems are preserved. Sensitivity analyses show that increasing capital costs by 50% can be offset by an increase in sewage sludge disposal fees of $10/metric ton.
- Research Organization:
- Environmental Energy Systems Inc. (US)
- OSTI ID:
- 20013452
- Resource Relation:
- Conference: 24th International Technical Conference on Coal Utilization and Fuel Systems, Clearwater, FL (US), 03/08/1999--03/11/1999; Other Information: PBD: [1999]; Related Information: In: The proceedings of the 24th international technical conference on coal utilization and fuel systems, by Sakkestad, B.A. [ed.], 1091 pages.
- Country of Publication:
- United States
- Language:
- English
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