煤焦分形维数及其对比热容的影响研究

比热容是煤炭热物理性质之一，在煤矿的矿井防火、防止煤与瓦斯突出、井下降温设计及煤炭加工利用(如煤炭的燃烧、气化、焦化、液化等)等方面是关键参数之一，对提高煤炭热能利用率、提高经济效益、减少环境污染等，具有非常重要的意义。比热容的影响因素很多，如煤化程度、水分质量分数、热解温度等，煤焦微观结构的影响也是其中很重要的一方面。分形几何由Mandelbrot 1982年创立，是定量描述自相似或自相关等不规则形体的工具。研究表明，煤焦微观结构具有分形特征。在煤焦分形的研究中，常用的实验技术方法为吸附法、小角度X射线散射法和孔度法，采用扫描电子显微镜和数字图象处理方法研究煤焦的分形结构，能更加深入地理解其分形维数与性能的关系。

Study of fractal dimension and its effect on specific heat capacity of coal or chars

The specific heat capacity is one of the thermo-physical properties of coal, which is an important parameter in utilization of coal. The microstructure of coals and their chars produced at the different pyrolysis temperature were studied by a scanning electron microscope, and the specific heat capacity was measured by DTA and DSC method. The microstructure of 4 coals with higher rank and their chars are well statistically self-similar and have been expressed by the fractal dimension. The results show that the fractal dimension is related to coal rank and pyrolysis temperature. The microstructure and the fractal dimension of coals have a good relationship with their specific heat capacities. For coals with different rank or chars produced at different pyrolysis temperature, the specific heat capacity increases with the increase of fractal dimension. The mechanism of the fractal dimension and the specific heat capacity are correlated with fractal dimension and statistical-thermodynamics theory. The more compacted and ordered the microstructure is, the less the number of pores, cracks and defect center is and the smaller the specific heat capacity is; on the contrary, the specific heat capacity changes greatly.