CaO固硫反应机理研究的新进展

DEVELOPMENT OF MECHANISM OF CaO SULFATION REACTION

CaO固硫反应的机理研究一直是高温钙基固硫的难点,最近研究认为CaO固硫反应分为两个阶段:前期为表面化学反应阶段,后期为产物层扩散控制阶段。前期反应生成的CaSO4不仅堵塞了CaO颗粒之间的微孔,也逐渐包覆了CaO颗粒,致使后阶段固硫反应转化率明显降低。传统上认为是SO2和O2通过CaSO4产物层向内扩散与CaO进行反应,依此机理提出了核收缩模型和等效粒子模型。新的研究结果认为,固硫反应后期的产物层扩散控制阶段,主要发生的反应是Ca2+通过产物层CaSO4扩散至表面与SO2和O2进行反应,而与传统的机理不同。本文主要介绍了两种实验技术在CaO固硫机理研究中的应用,并在实验现象基础上,对固硫机理提出了新认识。最后对在CaO中添加了不同添加剂能明显提高固硫率的试验数据作了新的机理解释。

There are two stages in the overall CaO Sulfation process: The initial stage of sulfation is chemical reaction control and its speed is faster The second stage reaction proceeds under the productlayerdiffusion control regime after CaSO4 buildup The later rate of sulfation is slower It is very important how to improve the rate of the second stage of sulfation The major process is that Ca2+ ions outward diffuse through the sulfate product layer to the surface of CaSO4 and react with O2-, O2 and SO2 other than they move inward to react with CaO covered by CaSO4, when the solid product layer CaSO4 of sulfation reaction is dense and not cracked The CaSO4 covering and the pores in the CaO particles being plugged resist the further sulfation reaction Hence, how to increase the rate of the further sulfation reaction is largely investigated Several kinds of experiment technologies are performed to identify the mechanism of the Ca2+ diffusion And a new mechanism greatly supports the result that the additives can obviously increase the overall conversion of CaO