In-situ study of fractal properties of coal char particles during catalytic gasification
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摘要: 通过高温热台原位研究气化阶段钾基催化剂对神府煤焦的催化气化作用。考察了气化温度（800−900 ℃）和催化剂负载量（4.4%、10%（质量分数））对煤焦反应性能的影响。通过热台显微镜对煤焦颗粒催化气化过程进行可视化研究并引入分形理论对煤焦颗粒表面结构进行分析，揭示分形维数所表征的气化反应性。实验结果表明，煤焦颗粒的分形维数与之碳转化率呈正相关性，即催化剂负载量一定，改变气化温度，分形维数愈大，煤焦颗粒的碳转化率越大；气化温度一定，改变催化剂负载量，分形维数愈大，煤焦颗粒的碳转化率越大；煤焦颗粒的初始气化反应速率与分形维数关系与碳转化率一致；煤焦颗粒的分形维数与煤焦球度、角度间相关性较大，存在指数关系；即分形维数随煤焦颗粒角度的增加而增大；煤焦颗粒分形维数指标可用于煤焦催化气化过程的研究。Abstract: Interactions of potassium-based catalysts with Shenfu (SF) char during catalytic gasification was observed by an in-situ heating stage microscope. The effects of the gasification temperature (800−900 °C) and the catalyst loading (4.4%, 10%) on the reactivity of coal char were investigated. The heating stage microscopy was used to visualize the catalytic gasification process of coal char particles and the fractal theory was introduced to analyze the surface structure of coal char particles to reveal the gasification reactivity. The experimental results show that the fractal dimension of coal char particles is positively correlated with the carbon conversion rate, and the fractal dimension increases by increasing the gasification temperature and the catalyst loading. The relationship between the initial gasification reaction rate and the fractal dimension of coal char particles is consistent with that between the carbon conversion rate and the fractal dimension of coal char particles. There is an exponential relation between the fractal dimension of coal char and the char angle; the fractal dimension increases with the increase of coal char particle angle; and the fractal dimension of coal char particles can be used in the study of coal char catalytic gasification process.
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图 1 气化温度对气化反应性能的影响
Figure 1 Effect of gasification temperature on gasification reactivity
图 3 气化温度对煤焦催化气化的影响
Figure 3 Effect of gasification temperature on the catalytic gasification of coal char
图 4 4.4%催化剂负载量与不同气化温度的lgP-lgA关系
Figure 4 Curves of lgP-lgA at different gasification temperatures (catalyst loading = 4.4%)
图 5 分形维数与碳转化率、初始气化反应速率的关系
Figure 5 Relationship between fractal dimension and carbon conversion or initial gasification reaction rate
图 6 分形维数和球度、角度之间的关系
Figure 6 Relationship between fractal dimension and sphericity or angle
表 1 样品的工业分析和元素分析
Table 1 Proximate and ultimate analyses of tested samples
Proximate analysis w/% Ultimate analysis wd/% Mad Ad Vd FCd C H N O* S 1.09 6.60 33.17 60.23 74.13 4.89 0.96 12.51 0.94 *: by difference; ad: air dried basis; d: dry basis 
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表 2 气化温度和催化剂负载量对分形维数的影响
Table 2 Effects of gasification temperature and catalyst loading on fractal dimension
Gasification temperature/℃ Catalyst loading 0.0 4.4% 10.0% 800 0.803 0.993 850 0.852 0.876 1.107 900 0.904 0.947 1.329
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