Abstract
The focus of this work is on the modeling and the thermodynamic evaluation of an integrated gasification combined cycle (IGCC) for the co-production of electricity and substitute natural gas (SNG). At first, an IGCC with CO2 capture for electricity generation is analyzed. Coal-derived syngas is conditioned in a water gas shift unit (WGS), and cleaned in an acid gas removal system including carbon capture. Eventually, the conditioned syngas is fed to a combined cycle. A second case refers to a complete conversion of syngas to SNG in an integrated commercial methanation unit (TREMP™ process, Haldor Topsøe, Kgs. Lyngby, Denmark). Due to the exothermic reaction, a gas recycling and intercooling stages are necessary to avoid catalyst damage. Based on a state-of-the-art IGCC plant, an optimal integration of the synthetic process considering off-design behavior was determined. The raw syngas production remains constant in both cases, while one shift reactor in combination with a bypass is used to provide an adequate H2/CO-ratio for the methanation unit. Electricity has to be purchased from the grid in order to cover the internal consumption when producing SNG. The resulting heat and power distributions of both cases are discussed.
Highlights
The global energy use is rapidly increasing in all forms, including electrical power, liquid fuels and natural gas
The focus of this work is on the modeling and the thermodynamic evaluation of an integrated gasification combined cycle (IGCC) for the co-production of electricity and substitute natural gas (SNG)
Coal-derived syngas is conditioned in a water gas shift unit (WGS), and cleaned in an acid gas removal system including carbon capture
Summary
The global energy use is rapidly increasing in all forms, including electrical power, liquid fuels and natural gas. A serial arrangement is favored based on the exothermic nature of the methanation process in conjunction with insufficient axial and radial heat dissipation when using multiple fixed bed reactors at pressures between 25 and 40 bar. Few studies focused on integrated concepts for the co-production of SNG and electricity The integration in these systems is limited to heat integration by recovering heat from the methanation reactors, to produce power as a by-product. These studies consider a coproduction only under design conditions. Based on a low-cost IGCC concept producing only electricity, the TREMP is implemented to convert syngas coming from the gas-cleaning unit to high-quality SNG. Steam cycle Steam-turbine isentropic efficiency HP, IP, LP [30] Isentropic efficiency of pumps Condenser pressure Pinch-point temperature difference for gas/gas, gas/liquid, liquid/liquid heat transfer
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