石灰石高温快速煅烧分解反应动力学研究

Kinetics study on decomposition reaction of limestone under ultra-high temperature

采用热重分析技术,研究了石灰石在超高温条件下分解的动力学机理。利用大功率高温碳管炉,将粒径为15~20 mm的石灰石颗粒在1 350~1 500℃下快速煅烧,煅烧后的试样断口在扫描电镜下观察发现存在明暗交替的反应界面。据此,用随机成核模型对CaCO_3向CaO相变进行动力学分析。研究结果表明:试验条件下的石灰石热分解反应符合随机成核和随后生长机理模型,机理函数方程为G(α)=[-ln(1-α)]~n。温度在1 350~1 425℃和1 450~1 500℃石灰石分解反应级数n分别为1/2和1/3,前者受界面化学反应控制,反应活化能为110.81 k J/mol;后者受扩散控制,反应活化能为25.33 k J/mol。

The thermal decomposition kinetics of limestone was investigated by thermogravimetric analysis technology at ultra-high temperature. The limestone particle sizes were distributed in the range of 15-20 mm,and the calcination temperature was controlled at 1 350- 1 500 ℃ during the experiments. It was found that the interface was light and dark alternately while observing the morphology of the calcined lime samples under the condition by SEM. The reaction kinetics analysis of CaCO3 phase transforming to CaO phase should be in accordance with random nucleation model. The results revealed that the thermal decomposition reaction of limestone under ultra-high temperature was regarded as a randomly nucleation and growth model,obtaining the mechanism function G（ α） =[- ln（ 1- α） ]n. The reaction order n was 1 /2 at1 350- 1 425 ℃ and 1 /3 at 1 450- 1 500 ℃ respectively. The reaction controlling mechanism of the former in CaCO3 decomposition was interface reaction,while the activation energy was 110. 81 k J / mol.Meanwhile the reaction controlling mechanism of the latter was diffusion,of which the activation energy was25. 33 k J / mol.