Thermodynamic and Economic Assessment of Oxy-Combustion CCS System Applied to Gas Turbine-Driven Compressor Stations

Government policies currently in place or in development will require the reduction of greenhouse gas emissions from industry, including gas transmission systems. Most of the natural gas transmission systems are powered by gas turbines of sizes up to 30 MW per unit. A typical gas turbine of this size can emit 6 ktonnes of CO₂ per MW-year, equivalent to about 180 ktonnes per year. Reduction in greenhouse gas emissions can be accomplished through post-combustion systems (separation of CO₂ from flue gases through chemical absorption, physical adsorption, membrane or cryogenic systems) or through oxy-fuel combustion, where fuel is combusted in pure O₂ leading to sequestration of CO₂ by compression and dehydration of the exhaust gases. The purpose of the current work is to explore the application of the latter concept, simplify and enhance the cycle, and to provide an economic valuation of the cost per tonne of CO₂ abated. Innovations explored for enhancement include elimination of excess power production, simplification of capital equipment requirements, and optimization of the power to the booster produced from the gas turbine and steam turbine. The paper presents various innovation options arrived at, detailed thermodynamic parameters, and a cost and economic evaluation of these options. Particular emphasis was placed on the application of this technology to a typical compressor station on a natural gas transmission system as this application is vastly different than a typical power plant contemplating or employing carbon capture and storage (CCS) systems, most notably from the small power size, the remote location, and the self-containment perspectives.