Study On Thermodynamics System Optimization Of Double Reheat Coal-fired Power Plant With Post-combustion Carbon Capture

The CO₂ emission rate of conventional coal-fired units can be obviously decreased by integrating carbon capture system in these units.However,large quantities of steam from thermodynamic system will be fed into carbon capture system,leading to the deviation of operation parameters and significant reduction of unit efficiency.It is an urgent problem to solve that how to maintain the unit efficiency after integration of carbon capture system.In this paper,the 660 MW double reheat unit is taken as the reference unit,optimal integration of carbon capture system in coal-fired unit is then further studied.The extraction steam from thermodynamic system is feed into post-combustion carbon capture system with chemical absorption using monoethanolamine?MEA?.The conventional integration scheme of carbon capture system in reference unit is established,and the cycle thermal efficiency of this unit is calculated.An improved integration scheme which introduces a back pressure turbine named carbon capture turbine is established according to the shortcomings of the conventional integration scheme.The steam water distribution matrix equation and cycle thermal efficiency calculation formula is derived in order to optimize the parameters of the improved integration scheme by the use of dynamic adaptive particle swarm optimization.Results indicate that thermal economy,energy saving and emission reduction effect of newly-designed unit are much better than these of conventional retrofitted unit under both full load and 75% part load.The standard coal consumption rate has reduced 10.32 g/?kW·h?and the CO₂ emission rate has reduced 4.07 g/?kW·h?compared with the conventional retrofitted unit under full load.The use of carbon capture turbine can effectively reduce exergy loss of the thermodynamic system and lower the energy consumption level of newly-designed unit after comparison of superheat degree of extraction steam and exergy losses of each equipment.The trough solar collector system which indirectly generates steam is introduced into coal-fired unit with carbon capture system.Two integration schemes are developed,one is integrating solar collector system in carbon capture system,the other is integrating the system in regenerative system of thermodynamic system,suitable structures of each integration schemes are established,too.The general steam water distribution matrix equation with different auxiliary flows is derived.The integration scheme that solar energy feed NO.1 high pressure regenerative heater of newly-designed unit is chosen as the best scheme after comparison of thermal economy and techno-economy.The standard coal consumption rate has reduced 21.89g/?kW·h?and the CO₂ emission rate has reduced 8.64g/?kW·h?compared with newly-designed unit.