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Optimisation of the connection of membrane CCS installation with a supercritical coal-fired power plant

Kotowicz, Janusz, Bartela, Łukasz
Energy 2012 v.38 no.1 pp. 118-127
carbon dioxide, coal, compressors, cooling, electricity costs, greenhouse gas emissions, heat transfer, power plants, steam, system optimization, vacuum pumps
In this paper, the methods of the integration of a supercritical coal-fired power plant with membrane CCS installation are shown. In addition to membrane modules, the CCS installation also consists of two vacuum pumps and two CO₂ compressors. In this paper, the relationship between the auxiliary power required to drive these machines and the recoverable amount of heat is shown. This relationship is the reason for the integration of the supercritical coal unit with the CCS installation, which is used for cooling compressed CO₂ in the CCS installation by use of condensate (or feed water) from the supercritical coal unit cycle. This cooling process causes both a reduction of the auxiliary power required to drive the compressors and vacuum pumps and increase of power ratio of a steam turbine. In this paper, the optimisation method for minimising the decrease of overall efficiency of the power plant connected with its integration with CCS installation is shown. This results in choosing the optimal pressure ratios in the applied compressors and vacuum pumps under the condition of sufficient heat transmission to the steam turbine cycle. For investigated units, the cost of CO₂ emission avoidance and the break-even price of electricity were also calculated.