Absorption Behavior of Chlorine and Sulfur by Ca(OH)_2 in a Fluidized Bed Reactor

摘要

Refuse derived fuel (RDF) and sewage sludge contain significant amounts of chlorine and sulfur respectively. HC1 and SO_2 are released from their co-combustion in a fluidized bed combustor (FBC). Calcium compounds such as Ca(OH)_2 added in RDF before producing it can minimize the emission of HC1 and SO_2 in the flue gases. This work was carried out to investigate the absorption reaction of chlorine and sulfur with Ca(OH)_2 under simulated conditions related to co-combustion of RDF and sewage sludge in a FBC with respect to high temperature, moisture and mixing of samples. The combustion experiments were carried out in an electrical furnace and PVC and sulfur powders were only used as test feed materials. High purity slaked lime powder was also used to capture chlorine and sulfur compounds. The experimental results showed that the removal efficiency for both chlorine and sulfur was over 90% when Ca/0.5Cl or Ca/S molar ratio was more than 2.5. The simultaneous absorption of chlorine and sulfur also improved the removal efficiency of the individual elements. In particular, the presence of chlorine markedly plays a role increasing the removal efficiency of sulfur. The removal efficiency was the highest at 700℃ in both individual and simultaneous absorption of chlorine. The removal efficiency of sulfur increased as the temperature increased. The removal efficiency of chlorine sharply decreased from 95% to 83% when the moisture content in gases increased from 0 to 20 vol%. The presence of moisture has a significant effect on decreasing the removal efficiency of chlorine.