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Abstract

A method for producing a lightweight ceramic aggregate, particularly from coal ash, according to the invention is characterized in that the raw material mixture of the total moisture content preferably below 20% by weight consisting of power station ashes originating from combusting coal, or ashes from combusting coal in a mixture with biomass ash, or ashes from co-combusting biomass with coal and phosphogypsum in an amount of up to 50% by weight, taken from dumps and/or from direct dump from a power station or a heat and power station, the raw materials from the dumps preferably being heated up in winter by a mixture of atmospheric air and exhaust gases from the step of burning and sintering, with a content of non-burnt coal above 6% by weight, agglomeration promoting agents like silty non-organic materials, preferably bentonite, preferably in an amount of up to 4% by weight, clay preferably up to 6% by weight, organic waste materials like used paints and lacquers, after-fermentation sludge in an amount preferably of up to 10% by weight, and after-coal mining waste materials in an amount preferably of up to 50% by weight, the mixture being completed with dust separated from exhaust gases produced during the step of burning and sintering, is fed to preferably at least one of two or more granulating disks, or in a cascade-type manner to at least two granulating disks, where it is sprayed with water, preferably in a form of a mist, to the total moisture content preferably below 30% by weight. Next, the screened fraction of grains of the granularity of preferably 6-30 mm, is subjected to counterflow drying in the heat of a mixture of the atmospheric air and cooled exhaust gases from the step of burning and sintering, the cooled exhaust gases having the temperature below the ignition temperature of the granulated material. The dried granulated material is subjected to burning and sintering in a co-flow rotary oven with radial air supply, with filling the oven with the granulated material preferably above 50% of its volume without adding any external fuel. Next, the burnt granulated material is subjected to a non-membrane atmospheric air cooling process in a crossed arrangement in a cooling bed, preferably of a transporter or grate type, the cold air being fed to the cooling bed into its specific cooling zone in such an amount that its mixture with the exhaust gases led out from the oven is suitable for drying the granulated material in the drier, for heating up, particularly in the winter, the raw materials taken from the dumps, and for feeding the nozzles radially delivering hot gases into the rotary oven. Finally, the granulated material cooled down preferably to a temperature below 100° C. is transported to the storage yard for the final product, where the aggregate is sorted into trade fractions, round aggregate, and the overgrains, which, after crushing and re-sorting is a crushed aggregate.

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First Claim