Continuous Sorbent Reactions in a High-Temperature Fabric Filter Following Convective Pass Ca(OH)₂ Injection for SO₂ Removal

ABSTRACT

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.