Some aspects of structural transformations taking place in organic mass of Ukrainian coals during heating. Part 1. Study of structural transformations when heating coals of different caking capacity

The structure of the plastic layer in coals of different caking capacity was studied using the X-ray method and the influence of the plastic layer structure on the mechanism of coke formation was determined. It is shown that the transportation of the plastic mass in the gas-saturated zone of the plastic layer has a decisive influence on the decrease in volume of the coal charge and on obtaining a denser residue during carbonization. When heating poorly caking and non-caking coals an increase in the charge volume takes place.Using the quantitative X-ray phase analysis an ordered phase amount (C_cryst) was found in solid residues of carbonization and the parameters d₀₀₂, L_c and L_a were determined. It is shown that the gas-saturated zone is generated in the plastic layer only when structural transformations in coals take place at the pre-plastic stage without changing the ratio between the number of carbon atoms in the ordered and non-ordered phases. The transition of well caking coal into the plastic state is accompanied by the activation of segmental and conformal movement of side chains and separate macromolecular fragments of the coal organic mass. In the course of grain swelling of non-caking coal its crystallites degrade. The conclusions drawn on the basis of X-ray studies were confirmed by the EPR-spectroscopy of residues corresponding to plastic zones in coals of different caking capacity.     

X-ray investigation of transformation in coal organic mass during heating. Part 2. Influence of coal charge density and heating rate on structural transformation in organic mass of poor caking coals

The influence of density and heating rate on the processes occurring during carbonization of low rank and high rank coals was investigated using X-ray technique. X-ray pictures have shown that an increase in charge density has no or little effect on decreasing its volume during carbonization. A rapid heating results in increasing the volume of solid residues obtained after carbonization.The results of X-ray analyses have shown that the increase in charge density tends to increase the quantity of the ordered phase largely due to growth of the crystallites present. During rapid heating processes of crystallite growth also take place, however, the main contribution to the increase in the ordered phase is made by the processes of occurrence and growth of new crystallites.