Control strategy optimization and energy saving analysis for slurry circulation pumps in fixed-frequency mode of desulfurization system in coal-fired power units
To accommodate grid-connected large-scale renewable power,coal-fired power plants need to undertake more peak shaving and frequency regulation tasks,so it will engage in the processes of deep peak shaving and load cycling for a long time.In this situation,the performance of wet flue gas desulfurization system(WFGD)will degradation and the auxiliary power consumption will increase significantly.To solve this problem,the dynamic model of an ultra-supercritical 660 MW coal-fired power unit and the dynamic model of the WFGD system based on the double-membrane theory are established.The performance of the desulfurization system is simulated when the slurry circulation pumps are switched under different operating conditions during the load cycling processes.It is found that the precise matching of slurry and flue gas during load cycling processes can achieve the minimum power consumption of the desulfurization system while meeting the SO2 emission standard.Furthermore,when the slurry circulation flowrate changes stepwise during load cycling processes,the prediction model of changes in SO2 mass concentration at the WFGD system outlet is obtained.An optimization control strategy for the slurry circulation pumps in fixed-frequency mode is proposed,which can achieve the best match between the slurry and flue gas during load cycling processes.Finally,the energy saving potential for the proposed control strategy is analyzed.When the load cycling rates are 1.0%,1.5%and 2.0%Pe/min,the energy saving potential is 20.12%,21.52%and 22.82%during loading down processes from 75%THA to 50%THA conditions,and that value will be 10.04%,9.90%and 8.66%during loading up processes,respectively.The difference in flue gas flowrate during load cycling processes is found as a key factor causing the disparate of energy saving potential during loading down and loading up processes.
wet flue gas desulfurizationslurry circulation pumpscoal-fired power unitcontrol strategy optimizationenergy saving analysis
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