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化学学报
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化学学报 ›› 2003, Vol. 61 ›› Issue (9): 1410-1415. 上一篇    下一篇

研究论文

CaO固硫过程中Ca~(2+)在CaSO_4产物层内扩散的研究

杨海波;武增华;邱新平;王军民;刘金权;郭峰   

  1. 清华大学化学系
  • 发布日期:2003-09-15

Ca~(2+) Cation Diffusion through CaSO_4 Product Layer during Sulfur Retained Reaction with CaO

Yang Haibo;Wu Zenghua;Qiu Xinping;Wang Junmin;Liu Jinquan;Guo Feng   

  1. Department of Chemistry, Tsinghua University
  • Published:2003-09-15

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应用标记实验技术，研究CaO固硫反应过程中产物层扩散控制阶段的反应机理 。利用扫描电镜和反射式光学显微镜，对压制烧结并带有Pt标记的CaO样品在固硫 反应前后的形貌变化观察，结果表明：经过较长时间的固硫反应后，在Pt标记层外 表面形成一层覆盖物，XRD分析结果证明该覆盖物是CaSO_4。利用电化学综合测试 仪测量了CaO及CaSO_4在高温下的电导率，结果表明在1000 ℃时CaSO_4的电导率达 到了10~(-3)数量级，说明在高温下CaSO_4内Ca~(2+)有较高的离子迁移特性。根据 标记实验、电导率测试的结果和CaO掺杂体系的固硫动力学数据的分析认为：CaO固 硫反应在后期的扩散层控制阶段的主要反应是Ca~(2+)通过CaSO_4产物层扩散至 CaSO_4外表面与SO_2和O_2进行反应，生成CaSO_4，而不是SO_2和O_2气体通过 CaSO_4产物层向内扩散，在颗粒内部与CaO发生固硫反应。

关键词: 氧化钙, 硫, 离子扩散, 电导率, 反应机理, 扫描电子显微镜, X射线衍射分析

Sintered CaO tablets covered with platinum marker on the surface were exposed to simulated coal gas containing SO_2 at 1200 ℃ in a tube reactor. The SEM micrograph and reflex optical micrograph were used to observe morphology changes of the tablets. After the CaO tablet covered with platinum marker being reacted for 120 h, a thick layer of product CaSO_4 formed on the surface of the platinum marker. The layer of product CaSO_4 is compact. At high temperature, the conductivity of CaSO_4 reached 3.5 * 10~(-3) S·cm~(-1). This means that Ca~(2+) ions in CaSO_4 have higher mobility. A new reaction mechanism of sulfur retained by CaO is suggested as follows: In the diffusion stages of GaO desulphurization, Ca~(2+) ion in CaO diffuses outward through the sulfate product layer to the interface of CaSO_4 and gas to form GaSO_4 with O~(2-) , O_2 and SO_2, rather than that SO_2, O_2 diffuse through the sulfate product layer into the interface of CaSO_4 and CaO to react with CaO.

Key words: CALCIUM OXIDE, SULFUR, ionic diffusion, ELECTRICAL CONDUCTIVITY, REACTION MECHANISM, SEM, XRD

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