Energy Efficiency Analysis And Optimization On Solar Assisted Post-combustion Carbon Capture System For Coal-fired Power Plant

To desorb CO₂ by steam extraction will contribute to a power plant output decrease of about 10%.Fortunately,low and medium temperature solar collectors,which have a thermal energy collecting temperature matching the temperature of reboiler and a relatively low cost,can be used as heat source for carbon dioxide desorption in a reboiler.Solar-assisted CO₂ capture system uses low and medium temperature solar collectors instead of high temperature extracted steam from power plant for CO₂ desorption,and the initially expected extracted steam can continue to do work,thus,CO₂ emission reduction is achieved together with little influence of steam extraction on generator output.The main content of this project is to analyze the energy characteristics of solar-assisted post-combustion CO₂ capture system of a Coal-fired power plant and to optimize the system.Firstly,the solar thermal energy collecting system model and the CO₂ absorption-desorption system model were used to simulate the thermal energy collecting characteristics of solar collectors and the regenerative energy characteristics of CO₂ absorption and desorption,respectively.The simulation results indicated that when the mass fraction of MEA was 30wt% and the pressure of desorption of was 1bar,1.4bar and 1.7bar,the CO₂ load of lean liquid at which the heat load capacity of the reboiler was minimum is 0.28molCO₂/molMEA,and CORresponding heat load of the reboiler was 3.508MJ/kgCO₂,3.337MJ/kgCO₂ and 3.255MJ/kgCO₂ respectively.Thirdly,the system energy characteristics of the proposed four coupling schemes when desorbed CO₂ by stream extraction and desorbed CO₂ with solar assistance were simulated for different thermal energy collecting temperature size and price of solar collector,as well as different weather conditions.The results showed that when the type of solar collectors was not taken into consideration,the net system power outputs of scheme 1,2,3 and 4 were 508.59 MW,513.83 MW,513.48 MW and 526.98 MW,respectively;when the solar energy collecting areas of different solar collector types were made the same,the net power output of the system using PTC of 512.42 MW was the highest one;when the investment costs were made the same,the net power output of the system using FPC of 536.35 MW was the highest one.And then the technical and economic characteristics of the four coupling schemes were simulated and analyzed under weather conditions in different regions.It was concluded that for systems with thermal energy storage,the solar fraction?SF?of the system increased linearly with the increase of the solar collector area;for systems without thermal energy storage,when the solar collector area reached the first solar collector boundary area,the increase rate of the SF became slow,and when the solar collector area reached the second solar collector boundary area,the SF stopped to increase and kept at the CORresponding value,and the CORresponding values of the SF for the weather conditions of Lhasa,Xi'an and Tianjin were 40.97%,36.23% and 29.81%,respectively.There was a great variation in the critical solar collector price which could make the LCOEs of the solar-assisted CO₂ capture system equal to the LCOEs of the CO₂ capture system that only takes the extracted steam as the heat source.Take the coupling scheme 2 under the weather condition of Tianjin for example,the critical solar collector prices for LFC?CPC and PTC were 118.8USD/m2,65.6USD/m2 and 155.9USD/m2,respectively.