Study of graphitization of coking coal and changes and migration of coal-series minerals

In order to bring to light the law governing the variation and migration of coal-series minerals in the coal to graphite process, an analysis is made of the occurrence patterns and distribution of coal-series minerals through float-and-sink, petrographic and XRD analysis. Study results indicate that the low-density components in coal are predominantly clay minerals which are distributed in banded form, and the organic constituents are mostly vitrinite; the medium-density components are chiefly clumpy clay minerals and authigenic quarts of disseminated structure; and the high-density components consist principally of monomer quartz particles, lump carbonate minerals and strawberry-lime pyrite. The components in three densities as described above are graphitized at high temperature. As indicated by test results, the degree of graphitization of the test samples is noticeably increased with the increase of the ash content of the samples; indicating more or less that vitrinite and inert components exhibit different graphitization characteristic; and the high-density components with a graphitization degree as high as 94.68% belongs to a highly-ordered graphite with microcrystalline layered texture, It is also observed that the coal-measure minerals tend to gradually dehydrate and escape out of the cracks as polyoxide mixture in either liquid or gas form at a temperature of 1 500～2 200 ℃; the iron and silicon elements play a catalytic role in the graphitization process; when the temperature reaches above 2 400 ℃ there exists only tiny amount of silicon carbide in graphitized product, and the rest ash-forming minerals either escape in gaseous form or get separated out as glassy molten mixture with the drop of the temperature in the exhaust pipe of graphitization furnace.