Effect of dolomite and kaolin on pollutant emissions and ash agglomeration during pressurized oxy-fuel co-firing of chicken manure and lignite

Against the background of carbon neutrality, chicken manure is a promising animal-derived biomass for cleaner energy recovery, but its high ash and alkali contents cause pollutant-control and agglomeration problems during fluidized-bed utilization. This study compared dolomite and kaolin during lignite/CM co-firing in a laboratory-scale pressurized bubbling fluidized bed under 30% O 2 /70% CO 2 . Gas monitoring, thermogravimetry, XRF/XRD, SEM/EDS, and FactSage were combined to relate emissions to ash transformation. At 0.3 MPa and 50% CM, dolomite and kaolin decreased energy-normalized SO 2 emissions by 52.4% and 19.1%, respectively, but increased CO by 98.8% and 28.3%. After correction for additive-derived oxides, ash K 2 O decreased by 27.8% with dolomite and 50.8% with kaolin under the same condition. Both additives eliminated visible agglomeration. Dolomite promoted sulfur retention and refractory Ca/Mg silicates, whereas kaolin immobilized alkali metals in stable aluminosilicates. Accordingly, dolomite is preferable when in-bed desulfurization is the primary constraint, while kaolin provides stronger alkali immobilization with a smaller CO penalty. These results clarify the coupled gas-phase and ash-phase effects of mineral additives in pressurized oxy-fuel co-firing.