CFB烧结烟气脱硫灰亚硫酸钙热氧化条件优化

Thermal oxidation conditions optimization for calcium sulfite in desulfurization ash of CFB sintered flue gas

循环流化床(CFB)是一种常用的半干法烟气脱硫工艺,该工艺的副产物主要为脱硫灰。含有大量亚硫酸钙的脱硫灰较难被利用,致使大量脱硫灰堆积,给环境保护和企业生产带来了巨大的压力。亚硫酸钙的存在限制了脱硫灰在建材领域的应用,只有将其氧化为硫酸钙才能实现其资源化。脱硫灰热氧化主要采用了立式管式炉,分别考察了反应温度、反应状态、氧含量、水汽的含量对亚硫酸钙氧化的影响。结果表明:温度对脱硫灰氧化的影响最大,其次为气体流速、氧含量和水汽含量。反应温度与反应速率呈正相关;增加氧气含量可以提高反应速率,但当氧含量高于30%时,反应速率趋于稳定;反应器温度在350℃时,亚硫酸钙开始缓慢反应,在400℃、无预热气速为75 mL·min-1时,亚硫酸钙最大转化效率达到86%,预热处理后最大转化率达到90%;当水汽量<0.88 g·L-1时,水汽量的增加会抑制氧化的进行;当水汽含量>0.88 g·L-1时,则会促进反应的进行。以上结果对指导脱硫灰热氧化处理和节能环保具有理论与实践意义。

Circulating fluidized bed(CFB) is a commonly used semi-dry flue gas desulfurization process, in which desulfurized ash is the main by-product. Desulfurization ash containing a large amount of calcium sulfite is difficult to be utilized, which results in a large amount of desulfurization ash accumulation and brings a great pressure on environmental protection and enterprise production. The presence of calcium sulfite limits the application of desulfurization ash in the field of building materials, its resource utilization will be achieved only by the oxidation of calcium sulfite to calcium sulfate. In this study, the vertical tube furnace was mainly used in the desulfurization ash thermal oxidation experiments, and the effects of reaction temperature, reaction state,oxygen content and water vapor content on the oxidation of calcium sulfite were investigated. The results showed that the temperature had the greatest influence on the desulfurization ash oxidation, followed by the gas flow rate, oxygen content and water vapor content. The reaction temperature was positively correlated with the reaction rate. Increasing the oxygen content could raise the reaction rate, but the reaction rate reached stable when the oxygen content was higher than 30%. At the reactor temperature of 350 ℃, the reaction of calcium sulfite began slowly. At the heat speed of 75 mL·min-1 without 400 ℃ preheating, the maximum conversion efficiency of calcium sulfite reached 86%, while the maximum conversion rate after preheating treatment reached 90%. When the water vapor volume was greater than zero and less than 0.88 g·L-1, the increase of water vapor quantity could inhibit oxidation. However, at the water vapor content greater than 0.88 g·L-1, the reaction was promoted. The results of this study have important theoretical and practical significance for guiding thermal oxidation treatment of desulfurized ash, energy conservation and environmental protection.