Abstract: I Abstract: In view of the variation of dry heat oxidation of CaSO3 in sintering semi-dry desulfurization ash under different reaction conditions, the effects of temperature, O2 content and flow rate in gas, calcium compounds, iron oxide (Fe2O3), water vapor content and flow rate on CaSO3 oxidation were studied. It was concluded that: The reaction follows the Aarhenius equation. Under the condition that the temperature rising rate is 10 ℃·min-1 in air atmosphere, the gas flow rate of 450℃ and 75 ml·min-1 is the optimal process condition for the economic dry heat oxidation. Water vapor has two sides to the CaSO3 oxidation reaction. The oxidation of CaSO3 by calcium oxides was inhibited by inhibiting the generation of "O" _"2" ^"-" " and S" "O" _"3" ^"-" free radicals. The order of the inhibition of CaSO3 oxidation by the three calcium oxides from weak to strong was CaCO3 < Ca(OH)2 < CaCl2; When the temperature is less than 450℃ and the Fe2O3 content is more than 0.2%, the oxidation reaction plays a catalytic role. When the catalyst concentration is less than 0.2%, the reaction is mainly controlled by the catalyst concentration. When the temperature is more than 450℃, the temperature is dominant. SEM characterization shows that with the oxidation of CaSO3 to CaSO4, the morphology changes from cluster to column. CaCl2 not only inhibits the oxidation reaction, but also inhibits the crystal form of CaSO4. Fe2O3 promotes the formation of CaSO4 crystals. When the temperature is higher than 400℃, the internal temperature of desulphurized ash is higher than 500℃ for 5 min. At this time, the conversion rate of CaSO3 is more than 85%, and the pilot test temperature is slower, which does not have this feature. The Gibbs free energy calculation results show that the most likely reaction is the oxidation of CaSO3, and the oxidation and decomposition of calcium below 600℃ is impossible. The number of active sites in the process of CaSO3 oxidation is related to temperature. When the temperature is between 350℃ and 450℃, the reaction is a first-order reaction. When the temperature is higher than 450℃, the reaction will be completed quickly in about 5 min, and the reaction order cannot be determined.