Abstract:

Walnut shell has high yield, high fixed carbon content and low ash content. In this paper, the walnut shell was selected as the research object, the comprehensive pyrolysis characteristic index was proposed, the thermal dynamics analysis was carried out on it, and the carbonization process and principle were studied. Finally, the best carbonization process was obtained through experiments and response surface simulation analysis. It was found that the comprehensive characteristic index of pyrolysis first increased and then decreased with the increase of heating rate, and reached the peak at about 10℃/min^{since the pyrolysis reaction was more intense at this heating rate. The carbonization process of walnut shell was a multi-stage complex reaction process, which decomposed hemicellulose, cellulose and lignin in stages, and the activation energy of this process increased gradually. Finally, through simulation and experimental analysis, the optimal process was obtained as follows: heating time was 14.8min, final temperature was 324.7℃, soaking time was 60min, material particle size was about 5 mm and the optimal carbonization rate was 69.4%.}

Key words: carbonization, dynamic analysis, response surface analysis, optimal carbonization condition, agricultural and forestry waste

摘要：

核桃壳产量多，固定碳含量极高且灰分少。选取核桃壳作为研究对象，对其炭化过程的热动力学参数进行分析，探究其炭化进程及原理，最终通过实验和响应面模拟分析得到核桃壳炭化的最佳工艺。研究发现，综合炭化特性指数随着升温速率的增大呈先增大后减小的趋势，且在10℃/min左右时指数达到峰值，此升温速率下炭化反应更剧烈。核桃壳的炭化过程是一个多阶段的复杂反应过程，其分阶段进行半纤维素、纤维素和木质素的分解，该过程活化能总体逐渐升高。最后通过模拟和实验分析得出最佳工况为：升温时间为14.8min，最终温度为324.7℃，保温时间为60min，材料粒径为5mm左右，最佳炭保留率为69.4%。

关键词: 炭化, 动力学分析, 响应面分析, 最佳炭化工况, 农林废弃物