Continuous Sorbent Reactions in a High-Temperature Fabric Filter Following Convective Pass Ca(OH)2 Injection for SO2 Removal.
A specially designed two-stage reactor was used to study solid sorbent reactions in the filtration stage of a high-temperature fabric which follow convective pass Ca(OH)2 injection. Solid conversions during the progress of the sorbent reactions were thoroughly analyzed. It was found that, unlike the sorbent reactions in the injection stage, which proceed extremely fast with strong carbonation under high temperatures, the subsequent sorbent reactions in the filtration stage are much slower and residual sorbent is mainly utilized in removing sulfur dioxide (SO2). Two major reaction pathways are discovered in the filtration stage. The first route is through the decomposition of residual calcium hydroxide (Ca(OH)2), which is critical in inducing further sorbent reactions when there is sufficient residual sorbent. The second route is the sulfation of the carbonation product, calcium carbonate (CaCO3), which may become the principal reaction to remove SO2 after the residual sorbent is consumed. The con-vective pass and the fabric filter are found to be equally important reaction sites in the combined process of convec-tive pass sorbent injection with high-temperature filtration. The overall SO2 removal efficiency of the system is affected by both the sorbent injection and filtration conditions.
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 .
Design of a graphite element drop‐tube reactor system for study of SO2 removal by injected limestone sorbents
The design and operation of a graphite element drop‐tube reactor system for a study of the fundamental mechanisms and reaction rates of sulfur dioxide (SO2) removal by high‐temperature injection of limestone‐based sorbents is described. The reactor system is designed for laminar flow in an environment that allows for control of reaction temperature, sorbent particle residence time, and atmosphere composition. The sorbent injection system allows variable feed rates to as low as 1 mg/min for particles as small as 1 μm in diameter. The water‐cooled sorbent collection system arrests the high‐temperature reaction upon capture and allows analysis of the sorbent’s efficiency of SO2 capture and in situ particle‐size distribution. The results presented show the reactivity of different types of sorbents at varying conditions of system operation.