Kinetic Evaluation of Lime for Medium-Temperature Desulfurization in Oxy-Fuel Conditions by Dry Sorbent Injection

With increasing emphasis on the control of greenhouse gases, power plants may move towards oxy-fuel technologies rather than air-fired plants. This move leads to a change in the feed to the desulfurization unit, which also needs to be adapted along with the power plant. Most existing plants already have functioning desulfurization units, which need to be retrofitted for the new conditions. In the present study, three different limes have been examined as sorbents for sulfur capture in oxy-fuel conditions with varying residence times at medium temperature (150–450 ∘ C). Parameters indicative of the kinetics and competition between SO 2 and CO 2 , like SO 2 breakthrough time, total lime conversion, yield for sulfur capture and sulfur selectivity have been evaluated. The results of this study lead to the recommendation that medium temperature desulfurization should be used for moderate SO 2 capture, in combination with already existing sulfur capture systems. The effects of CO 2 and water vapor have also been analyzed. In addition, the performance of the unit irrespective of temperature strongly depends on the lime type. In addition, absence of water vapor strongly favored the desulfurization process when there was high concentration of CO 2 .

The Influence of Cr2O3 on the Sulfur Capture Efficiency of CaO in Pulverized Coal Combustion Process

The effects of Ca-based sulfur catcher on sulfur fixing were investigated by experiments. The results indicate that sulfur capture efficiency of CaO is the maximum when n(CaO)/n(S) ratio is equal to 2.5. Moreover, the influences of Cr2O3 on sulfur-fixing of CaO were studied when n(CaO)/n(S) ratio is equal to 2.5. The results indicate that addition of Cr2O3 can improve the sulfur capture efficiency of CaO, and efficiency of CaO is the best when Cr2O3 is added to 0.5%. This is because that Cr2O3 can be oxidized to CrO2. On the one hand, the oxides of chromium can catalyze the reaction of sulfur-fixing. On the other hand, CrO2 can react with SO2 to form Cr2(SO4)3. These also can improve the sulfur capture efficiency of Ca-based sulfur catchers.