| 摘要 |
Coarse washery refuse, broken shale or slate, as tailings from coal mining, containing 7-10% by mass of coal bound in the grains, is to be utilised for the production of aggregate for the construction industry via a stepwise thermal reaction of the granular material. In the first stage of the heat treatment, from 400 to 450 DEG C, the volatile components of the intragranular coal are shed in the reducing atmosphere of the furnace in such a way that the coal present in the grains is converted into coke. In the second stage of the heat treatment, up to about 650 DEG C, the coal freed of the volatile components is, with an oxidising atmosphere in the furnace, completely converted into coke and ignited in the core of the grains. The heat-pretreated coarse grains of the washery refuse are, for the third stage of the thermal reaction, built up into a coarse-porosity layer up to 100 cm thick and automatically go over into an ignition process of the grain/coke material so that this glows from the core of the individual grains outwards and the clay/siliceous granular material reacts to form dense ceramic chips, grit or gravel of high strength and bulk density.
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