| Coals with low ash, low sulfur, high calorific value in North Shannxi cause much attention at home and abroad, but the ash melting temperature is low. When used in solid-state discharge of boiler, coals are easy slagging and difficult to flush off. In coal exports, the ash melting temperature is an important quality index. The ash melting temperature of the northern Shaanxi coal is low, which not only directly affects the scope of application, also limits the export of coal ash. Therefore, a research to increase the ash melting temperature of the northern Shaanxi coal has an important practical significance.Coal slime is a kind of waste which produces in the process of coal washing. It has high moisture, high viscosity, high water, low calorific value and many other adverse conditions and it is difficult to achieve the industrial application. With the rapid development of the depth and breadth of coal processing, the output of the coal slime has obviously increased and the comprehensive utilization of it has become an urgent problem to solve.This thesis selected the four coal sample of the low ash fusion in North Shannxi and coal slime as additives were added to them. Using X-ray diffraction(XRD) analyzed the change of the mineral composition of the coal ash under the different temperature and different content. And then the influences were learned by the coal slime. The following conclusions are drawn:(1) As the amount of coal slime increased, ST and FT gradually increased for Xigou coals. They have differently changed with the different amount. When coal slime content was below 2.5%, ST and FT increased slowly, and more than 2.5%, ST and FT grew larger. For Shenmu hepan coal, ST and FT increased gradually with the increase of content of the peat, but ST was faster and FT was slow. When the content of coal slime was equal to 2.5% or more than 2.5%, the growth of ST and FT tended to be gentle. For Zichang hecaogou coal, when the amount of coal slime was from 0% to 3%, the biggest increase of DT can be up to 30℃. When the amount of coal slime was between 1% and 1.5%, the change of ST, HT and FT reached the maximum. For the gulf of Shenmu coal, when the amount of coal slurry was between 0% and 1.0%, the change of FT was the biggest. When the amount of coal slurry was between 0.5% to 1.0%, the change of DT, HT and FT were relatively greater. The biggest gain reached 12°C, 10°C and 15°C. These show coal slurry can effectively improve the ash melting temperature and just coal slime content will improve coal ash melting point.(2) By XRD analysis, peat can change the ash melting temperature. A reason is that the mineral in the coal ash has changed, and this change contains contents and species. That the ash melting temperature will be increased as the mullite, quartz and other mineral content relatively increase and the ash melting temperature will be decreased as calcite, feldspar, anhydrite and other mineral content relatively increase can be concluded by the images. The morphology of coal ashes were analyzed by electron microscope scanning. At 815℃, the ash particles are fine, and mainly are the floc. At deformation temperature, they are mainly composed of much debris, and not of uniform size. After joining oxides, they irregularly fused larger particles, it occurred congruent melting between the minerals in coal ash, appeared the melting phenomenon.(3) Coal slime, as a kind of waste generated in the process of coal washing is used for the change of the coal ash fusion temperature, which provides a new way of thinking to solve the problem of a secondary use of coals. |
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