Control strategy optimization for wet flue gas desulfurization system during load cycling dynamic processes: Energy saving and environmental impact

To accommodate high penetration of fluctuating renewable power within the power grid, thermal power plants often engage in load cycling dynamic processes. When thermal power plants operate under low loads and load cycling dynamic processes, large ratio of auxiliary power is consumed in wet flue gas desulfurization (WFGD) system, because the slurry flowrate cannot be regulated appropriately. In this study, dynamic models of SO₂ generation and WFGD system were developed, and coupled with the dynamic model of a thermal power plant. An optimization control strategy for slurry pumps under fixed-speed mode was presented. Then, model to determine the optimal slurry flowrates with changing parameters of flue gas and slurry was derived, and a control strategy to regulate inverter slurry pumps was proposed. The auxiliary power consumption during load cycling dynamic processes decreases significantly with optimization control strategies, although the cumulative SO₂ emissions increases. When the control strategy optimization for slurry pumps under fixed-speed mode was implemented, the energy-saving potential is 19.00%, 20.39%, 22.06% and 23.05% during load decreasing processes under load cycling rate of 0.5%, 1.0%, 1.5%, and 2.0% Pe0 min⁻¹, and that value under the control strategy to regulate inverter slurry pumps is 33.20%, 34.45%, 35.04% and 37.07%, respectively.