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I tried to upload the attachment, but my account level isn’t high enough; I could only paste the text here. When the Ca/S ratio reaches around 2.0, the desulfurization rate can exceed 90%. Calcium oxide and sulfur dioxide combine to form calcium sulfite; the temperature in the boiler’s combustion chamber is maintained at around 850°C to optimize this reaction. In the initial stage, due to the low temperature of the particles, the rate of sulfur fixation by CaO in the ash layer and the rate of diffusion of SO2 into the particles are low; the favorable mass transfer conditions in the dry distillation furnace result in a higher SO2 concentration on the particle surface ； When the overall temperature of the particles rises to around 850°C, the sulfur fixation reaction at the surface proceeds vigorously, resulting in a sharp decrease in the SO2 concentration ； When the sulfate conversion rate of CaO in the surface layer approaches 1, although SO2 continues to diffuse into the interior of the ash layer, its rate is lower than the mass transfer rate outward from the fluidized bed, causing the SO2 concentration at the surface to increase gradually over time. In the initial stage, the SO2 concentration is low due to the sulfur fixation by CaO in the surface layer. As the sulfation rate of the surface layer approaches 1, the effect of the diffusion resistance in the ash layer causes the internal mass transfer rate to be lower than the external one, resulting in a gradual increase in the SO2 concentration at the surface layer. The SO2 concentration begins to increase gradually over time, indicating that the combined process of diffusion resistance in the ash layer and sulfur fixation by the ash is as follows: in the initial stage, less SO2 diffuses inward due to the sulfur fixation by the ash itself; as the sulfation degree of CaO in the outer layer increases, the rate at which SO2 is consumed during diffusion decreases, resulting in an increase in the amount of SO2 that reaches the center of the particles. With the same ash particle size of the shale, the higher the furnace temperature, the greater the sulfur fixation capacity of the shale ash. This is because the higher the temperature, the greater the effective diffusion coefficient of SO2 gas in the ash layer, and the faster is also the intrinsic rate of sulfur fixation by calcium oxide, which leads to an increased sulfur fixation rate in shale ash. Given a fixed time period, the degree of sulfur fixation in shale ash becomes higher. In fact, the higher the temperature, the greater the likelihood of ash sintering, which affects the diffusion of SO2 gas within the ash layer and, to some extent, influences the sulfur fixation rate of shale ash. At the same temperature, the larger the particle size of the shale ash, the lower its sulfur-fixing capacity. This is because when SO2 diffuses from the gas phase into the interior of the shale ash particles, the smaller the particle size of the shale, the less the total diffusion resistance in the ash layer, allowing SO2 to penetrate deeper into the particles of shale ash, which in turn helps to increase its sulfur-fixing capacity.