GB744131A - Process for the production of high-grade products from raw material containing pit coal or brown coal - Google Patents

Abstract

A process for the removal of the ash content and for the dewatering of raw material containing pit coal or brown coal, such as sludges, dusts, intermediate material and impure coals, comprises mixing the raw material in fine or ultra-fine particle form with oil-containing substances, such as oil, tar or bituminous substances, such admixture being effected in the presence of a quantity of liquid, preferably water, sufficient to form a dispersion of the waste particles and of the oil-wetted coal particles and the conditions of mixing being such that little or no aggregation of the coal particles takes place, such dispersion then being mechanically, preferably centrifugally, separated, with simultaneous dewatering of the coal concentrate, into coal concentrate and waste liquid containing the bulk of the waste components of the raw material. Diffusion may be effected in a beater mill or centrifugal mill, and, during admixture, the mass may be subjected to pressure, centrifugal action or suction by passage through high speed baffle plate mills having a delivery slot, or high-speed or high-pressure pumps having attached nozzles or venturi tubes. Separation is preferably effected in a sifting centrifuge. The process may be carried out at elevated temperature and the pH value of the solution may be adjusted: froth flotation reagents may also be added. The water content of the raw material may be adjusted by the addition, or extraction, of water or by adding dry coal, sifter dust or breeze. The process may be repeated on the concentrates or on the waste, or may be combined with other known processes e.g. flotation, cyclonic separation, and particularly with processes for the preparation of ultra-pure coal such as flotation methods, heavy liquid processes and electrostatic processes, the tailings or concentrates from which may be subjected to the present process. Alternatively, by using a very small quantity of oil, the process may be used as the first stage in the preparation of ultra-pure coal, the concentrates and tailings being then separately retreated by the same process. In a further alternative, coal is separated by a heavy liquid process and the components of finest grain size separated from the sinks and floats, these components being subjected separately or in common to the present process: the waste particles obtained form a suitable loading medium for the heavy liquid and the latter may be regenerated by the use of the present process. Specification 183,430, [Class 82(ii)], is referred to.