Research on the characteristics of flue gas purification reaction in spouted bed

•Application of semi-dry flue gas purification in a fluidized bed reactor.•Nozzle expansion angle optimized and its effect on flue gas purification explored.•Large fluidized particles can obstruct the flow of flue gas within the spouted bed.•At Ca/S ratio of 2.5, the desulfurization and defluorination efficiency reach optimal.