焦化过程半焦孔隙结构时空变化规律的实验研究——孔结构的分形特征及其变化

应用分形理论的概念，结合压汞法测得的半焦孔隙结构数据，建立孔结构分形特征模型，考察了焦化过程中不同焦化温度、不同横向空间位置半焦孔隙结构分形特征及其变化规律。结果表明，孔径大于5μm 的孔不具有分形特征，孔径为20nm～5μm孔的孔隙结构具有分形特征，其分形维数为2.45～2.83，可以用分形维数定量表征孔隙结构；相同空间位置下，半焦孔结构分形维数低温时较高，随温度逐渐升高先减小，然后增大再减小；同一空间位置不同温度下分形维数的变化量较小(< 0.15)，表明温度对半焦孔隙结构复杂程度的影响不明显；相同焦化温度下，半焦中心和边缘处的孔结构分形维数大于中间部位，表明中心位置和边缘位置处的孔隙结构要比中间位置处的复杂。

Variation of pore structure of semi-coke with different temperature and spatial location during pyrolysis——Fractal dimension of pore structure

Using fractal theory as tool, coupling with inner pore structure of semi-coke by mercury intrusion method, the fractal characteristics of pore structure were studied. Through determining the fractal dimension of pore volume quantitatively, the change of fractal dimension of pore volume with different coking temperatures and different spatial positions during pyrolysis was investigated. The results show that there is no relationship between the fractal dimension and the pore structure with pore diameter >5μm. However, the pores with diameter of 20nm～5μm can be properly characterized by the fractal theory, and a fractal dimension range of 2.45～2.83 is obtained in this work. The fractal dimension of pore volume under identical spatial position is high at low temperature, then decreases and increases and finally decreases with the increasing temperature. But a small variation of the fractal dimension, less than 0.15, is observed under identical spatial position. It shows that the effect of coking temperature on the fractal dimension is not remarkable. Additionally, the fractal dimension of pore volume at the center and brim position of coke cake is greater than that of the middle position under identical coking temperature. It indicates that the pore structure at the center and brim of coke cake is more complex than that of the middle poison.