Specific exergy consumption as an index for steam extraction scheme selection for CO2capture systems in coal-fired power plants

Abstract

In coal-fired power plants, steam is extracted from steam turbine to supply the regeneration heat for chemical absorption carbon capture. This research analyses the steam and heat consumption of a CO2 capture system for different extracted steam, as well as the influences of different extracted steam on electricity production and power plant electric efficiency. Results show that specific steam consumption and specific heat consumption, which only reveal the quantity of the steam consumption, could not be used for evaluating the true energy savings of different steam extraction methods. Specific exergy consumption of the extracted steam (SEXCS), which focuses on both the quantity and quality of energy, is proposed and used as a main comprehensive evaluation index in the CO2 capture system. Compared with specific steam consumption and specific heat consumption, SEXCS can better evaluate the true energy saving of the different extracted steam. Compared with plant electric efficiency and specific primary energy consumption for carbon avoided (SPECCA), SEXCS is both simple in calculation and easy in acquiring the required data. SEXCS is thus recommended to be used as an important index for selection of steam extraction schemes for CO2 capture systems. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd