摘要
本文从结构化学的观点出发,在分析了石油焦不同组织形态的生成来源及其和微观层次结构的联系的基础上,提出了石油焦结构形态的新分类法。用光学显微镜、X光衍射、比重和焦粒外形长宽比等方法实测了几个国产试验针状焦的各个层次的结构参数,论证了它们之间的联系。在此基础上提出了评价针状焦品质的实验室新方法。
Based on the modern concept about the mesophase transformation mechanisms in the liquid phase carbonization processes, the factors influencing the characteristics of optical structural morphologies of needle cokes were briefly analyzed.From the viewpoint of dynamic transformation of structural unit, the structural nature of needle cokes of various magnitudes, the correlation of structural parameters among various structural magnitudes——crystal structure, substructure and optical structure and the successive changes of their character in the course of transformation of various optical morphologies were studied. On these bases, White's classification were revised and a renewed classification including 8 typical optical morphologies was suggested.The pycnometric density, the lattice constants andcrystallite dimensions and degree of crystallite orientation of graphitized samples of petroleum cokes were determined. On the other hand, the shape factor of coke particles (i.e. the ratio of longitudinal to transverse axis) and optical quantification of various structural morphologies on the calcined samples were also measured. The experimental results shew that these cokes, namely DEN, DCN and D-1, and the Japanese Petro. Cokes Ltd. premium coke belonged to needle coke.Taking DEN as example, it was shown that the most important factors influencing the structural morphologies of the coke macerals were the molecular nature of the precursor oil residue, its chemical reactivity and the stability of planar polynuelear aromatic molecules thus formed. The action of external forces exerted by volatile hydrocarbons escaping in the temperature range of 460°—500℃ was only of secondary importance.Though the reduction of external forces causes the decrease in the content of fine fibrous mieroeonstituent and poor acieular shape of calcined coke particles, excellent molecular structure of parent oil residue, however, eventually led to graphitized coke particles with high crystallinity, high degree of crystallite orientation and high degree of unsymmetry.In view of the multiplicity of the optical structural morphologies it is difficult to recommend a comprehensive, single and quantitative parameter for the description of the optical morphologies hence the significance of the quantitative estimation of optical morphological constitution is limited. In order to achieve comprehensive evaluation of optical structures of needle cokes, not only quantitative estimation but also qualitative description of all micro-constituents would be necessary.The K-value (shape factor) of calcined coke particles is not the only parameter in determining the needle coke properties because only the apparent shape of calcined coke particles can be illustrated. The low K-value of a coke does not inevitably lead to high CTE or poor resistance to thermal shock of graphitized article.Among all the measuring parameters introduced, the height of I(002) in X-ray diffraction spectra is preferred as the most important parameter in characterizing needle coke properties. In addition, the crystal parameters of graphitized cokes, i.e.c./2, Lc and La, and qualitative description and quantitative estimation of optical microconstituents must be used when precise evaluation of needle coke properties is required.
出处
《燃料化学学报》
EI
CAS
1981年第2期105-122,共18页
Journal of Fuel Chemistry and Technology
