Controllable Evolution Of Coal-based Mesophase Spherule And Mechanism Analysis

Coal dense medium component from the coal all-components group separation servedas the material. By adjusting carbonization tempreture, holding time, flow rate of N2,packing form of materal and content of additives, the effects of these factors oncarbonization yield, optical micromorphology and size distribution of mesophase spheruleswere investigated. Based on that, the controllability in the evolution process of mesophasespherule was discussed and the mechanism of generation and evolution of mesophasespherule was analyzed.The results show that of all those factors, the controllability of the carbonizationtemperature, the holding time and the packing forms of material is remarkable. It suggeststhat when the temperature is below400oC or the hoding time is below0.5h, the mesophasespherule cannot be obtained; when the temperature is in the range of400~410oC lasting2hand the material is feeded in crucible in bulk or when the temperature is425oC lasting0.5hand the material is feeded in crucible in bulk or when the tempreture is425oC lasting2hand the materal is feeded in crucible in the form of tabletting under10MPa pressure, themesophase spherule with the size of1~2μm can be obtained; when the temperature is420oC lasting2h and material is feeded in crucible in bulk or the tempreture is425oC lasting2h, the material is feeded in the crucible in the form of tableting under20MPa pressure or inthe tiled form, the mesophase spherule with the size of2~3μm can be obtained; when thematerial is feeded in crucible in bulk, by adjusting the temperatue to425oC lasting1~2h,the mesophase spherule with the size above3μm can be obtained; when the temperature isabove440oC or the holding time is above3h, only mosaic bulk mesophase can beobtained.Under lower temperature or shorter holding time, aromatic structures cannot formnuclear, so no mesophase spherules occur. When the temperature is higher or the holdingtime is longer, the thermal reaction of resource material moleculars is strengthened. Withthe increase of nuclears, they transfer and gather into spherical masses. Some of thosemasses transfer and get closer because of the interaction and eventully fuse into a fewmesophase spherules. With the temperature and holding time is improved, more sphericalmasses become more mesophase spherules. Then by inclusion of different spherules, thesize of spherules increases. When the size is too much to keep the sphere, the spherulesbreak up to form bulk mesophase, so the spherule number decreases. The packing form of material can influce the generation and growth of nuclears by influcing the escape ofvolatile gas and the thermal transmission efficiency among the material particles andeventully influce the size distribution of mesophase spherules.