An integrated de-carbonization supercritical coal-fired power plant incorporating a supplementary steam turbine, process heat recovery and a modified boiler structure

Abstract

Monoethanolamine (MEA) based CO2 capture in coal-fired power plants would consume a huge amount of the steam bleed from the steam turbines for the solvent regeneration. The unmatched steam bleed parameters for the solvent regeneration, as well as the huge amount of the process waste heat within the CO2 capture process, inevitably bringing about a significant efficiency penalty. In this study, a novel de-carbonization supercritical coal-fired power plant, which encompasses a supplementary steam turbine (SST), process heat recovery and a modified boiler heating exchangers configuration was proposed. In the proposed system, the steam bleeds for the reboiler and part of the regenerative heaters are coming from the SST, which is located in the upstream of the reheater (steam side), instead of the high and intermediate-pressure turbines (IPT), making the parameters of the steam bleed more matched with the solvent regeneration and feed water heating. In addition, part of the process heat within the CO2 capture/compression unit was efficiently recovered and beneficially used to heat the ambient air before its entering the air pre-heater. The saved flue gas can then be used to heat the feed/condensed water in the low-temperature economizer (LTE), saving part of the steam bleed from the turbines. The configuration of the superheaters/reheaters, as well as the air preheaters were also modified. The mass and energy balance as well as the system thermodynamic performance were determined by the developed models and process simulation. The economic performance of the proposed system was assessed by the cost of electricity (COE) and the cost of CO2 avoided (COA). Finally, the off-design performance of the proposed system was determined. Results showed that the energy efficiency penalty of the proposed system could decrease by 3.86%-points as compared to the reference system. The COE and COA of the proposed system without considering the CO2 transportation and storage cost were $86.11/MWh and $36.92/ton CO2, respectively, both less than those of the reference plant. The off-design operation analysis indicated that the proposed plant also featured a thermodynamics superiority in a wide range of power load variation.