Analysis And Optimization Of Large-scale CO₂Capture In The Coal-fired Power Plant

The global warming caused by the greenhouse gas like CO2, has become one of the worst environmental problems. China is a country which emits huge amounts of CO2annually. Among the total CO2emission, the CO2emitted from the coal-fired power plant plays a most important part. Thus, it is of great significance for China to reduce the CO2emission from the coal-fired power plant.The CO2Capture and Storage (CCS) technology has the potential to directly reduce CO2emission and is highly researched all over the world. Among all the CCS technologies, the MEA-based chemical absorption method is considered as one of the most feasible technologies because it is mature and suitable for the coal-fired power plant. However, due to its high energy consumption, this technology is still under development and can’t be widely used.Based on Aspen Plus software, this paper selects350MW and1000MW coal-fired power plants as the research objectives. Combined with MEA-based CO2capture process, the steam-water cycle in the coal-fired power plant is retrofitted and optimized to reduce the energy consumption caused by the CO2capture process.First, after deeply analyzing the energy balance in the MEA-based CO2capture process, this paper proposes a new integrated system. The integrated system fully utilize the low-temperature heat in the CO2capture process, to heat the condensed water in the steam-water cycle in the power plant and the circulating water in the radiant floor heating system, which improves the thermal performance and economic benefits.Then, focused on the root reason of the high energy consumption in the MEA-based CO2capture, this paper propose a new design idea for the coal-fired power plant based on a1000MW unit with double-cylinder&four exhaust characteristics in the LP steam turbines. A new back-pressure steam turbine is used to replace the original condensing steam turbine, which resolves the operating and safe problems caused by the CO2capture. The thermal analysis and techno-economic analysis results show that the new design idea of the coal-fired power plant is superior to the conventional design idea.Finally, the two technique routes for CO2capture proposed in this paper are different. The integrated system is suitable for the existing coal-fired power plants while the new design idea is suitable for future coal-fired power plants with lager-scale CO2 capture. Both the two schemes greatly reduce the energy consumption of CO2capture process and provide a new route for the CO2capture in the coal-fired power plant.