Economic implications of oxyfuel application in a lignite-fired power plant

Abstract

Scope of the work presented in this paper is to examine and evaluate the application of the oxyfuel combustion CO2 capture technology in a lignite-fired power plant from an economic point of view. Results from simulations dealing with the most important features for CO2 reduction are performed. The operational characteristics, the efficiency penalties as well as the net efficiency reduction emerging from the Greenfield application of the oxyfuel technology are presented. CO2 capture costs and the energy requirements associated with the oxyfuel method affect significantly the cost of electricity. This paper focuses on the analysis of the techno-economic factors that result in the increase of the cost of electricity in comparison with the conventional air-fired power plant. For this reason a typical Greek lignite power plant is used as a reference case. Any technical, economic and financial assumptions applied provide a common basis for both power plants (i.e., conventional and oxyfuel) for the assessment of the change of the cost of electricity and the CO2 capture cost. The oxyfuel simulations are performed by taking into account the adoption of measures for the exploitation of heat that would otherwise be wasted. Such measures concern both the water/steam cycle and the gas flows (e.g., the oxygen flow). Heat integration from processes – such as the air separation, the CO2 compression and purification and the flue gas treatment – is adopted in order to lower as much as possible the efficiency penalty. The cycle calculations have been performed using the thermodynamic cycle calculation software ENBIPRO (ENergie-BIllanz-PROgram). ENBIPRO is a powerful tool for heat and mass balance solving of complex thermodynamic circuits, calculation of efficiency, exergetic and exergoeconomic analysis of power plants. The software code models all pieces of equipment that usually appear in power plant installations and can accurately calculate all thermodynamic properties (temperature, pressure, enthalpy) at each node of the thermodynamic circuit, power consumption of each component, flue gas composition, etc. The code has proven its validity by accurately simulating a large number of power plants and through comparison of the results with other commercial software (Stamatelopoulos GN. Calculation and optimisation of power plant thermodynamic cycles. VDI-Regulations. Series 6, No. 340. Braunchweig, Mechanical Engineering Department; 1996 [in German]).