蒸汽活化改善中温烟气脱硫的机理

MECHANISM OF IMPROVING THE MEDIUM TEMPERATURE FGD PROCESS BY REACTIVATING SORBENTS BY STEAM

用蒸汽处理用于中温烟气脱硫的失去反应活性的脱硫剂可以显著提高钙利用率和脱硫效率。为了探明蒸汽活化机理,借助于成分分析和表观形貌检测,分析了蒸汽处理后的脱硫剂理化特性的变化,用CaO迁移的新观点揭示了中温蒸汽活化提高脱硫剂固硫能力的机理。经过蒸汽活化后,乏脱硫剂颗粒除了发生破碎外,其内部未反应的CaO会与蒸汽水合成Ca(OH)2,继而在体积膨胀作用下迁移到颗粒表面,并在分解温度以上还原和与SO2发生反应。迁移过程还改变了颗粒表层的孔隙结构,改善了SO2与CaO扩 散、接触和反应。

It has been verified that the calcium conversion rate of calcium-based sorbents and the sulfur removal rate of the medium temperature FGD process can be enhanced remarkably by reactivating the spent sorbents by using steam. In order to better understand the mechanism of steam reactivation, the physical and chemical characteristics of sorbents has been studied through analyzing the composition and the apparent construction of the sorbent before and after steam treatment. A new phenomenon - CaO transfer from the inside of sorbent particles to the surface - has been found, i.e. unreacted CaO in sorbent core is converted to Ca(OH)2 by hydration reaction with steam and then transferred to the sorbent surface due to expansion effects. During the sulfation reaction Ca(OH)2 is decomposed and reduced to CaO at its decomposition temperature, which encourages reactions with SO2. In addition, the improvement of the pore structure on the surface of sorbent particles and the SO2 diffusion to sorbents, which are caused by CaO transfer process, has been realized.