GB515608A - Improvements in the preparation of cement raw materials - Google Patents

Abstract

515,608. Concentrating ores ; cements. SMIDTH & CO. AKTIESELSKABET, F. L. Sept. 12, 1938, No. 26600. Convention date, Sept. 10, 1937. Drawings to Specification. [Class 82 (ii)] [Also in Group V] To render more suitable for use in cement manufacture an argillaceous limestone, marl, chalk, or similar ore which contains an excess of one or more minerals such as aluminium and magnesium silicates, the whole or part of the ore is subjected to froth flotation with a collecting agent which yields a concentrate of increased calcite content and tailings of reduced calcite content, and the tailings are then subjected to froth flotation with a collector which concentrates the siliceous materials leaving tailings of increased calcite content. These tailings may then be combined with the concentrates from the first flotation and with any part of the original ore not subjected to the flotation treatments, free silica being added to the mixture if required. The ore need only be ground sufficiently to free sufficient of the minerals present in excess to enable the desired corrections to be made ; according to the constitution of the ore either the coarser fraction, the intermediates, the fines, or the whole ore is then subjected to the flotations. In treating an ore containing graphite carbon, the carbonaceous matter may either be removed by a preliminary flotation using a frothing agent only, or it may be depressed during the flotation by the addition of a lignin sulphonate, as described in Specification 515,592. A lignin sulphonate may also be added to the pulp as dispersing agent, as described in Specification 515,601. In the first flotation in which calcite is concentrated in the froth the collecting agent used is of the fatty acid type, e.g., oleic acid or fish oil fatty acids, emulsions of fatty acids, e.g., stabilized emulsions, such as are described in Specification 515,606 and 515,607, or saponified tall oil which may be used in conjunction with mineral oil, e.g., as an emulsion. The frothing agent may be cresylic acid or a mixture of aliphatic alcohols obtained, with methanol. by the catalytic hydrogenation of carbon oxides. Stage oiling is usually desirable and the concentrate may be cleaned by flotation with further additions of reagents. In the second flotation a collector is used which gives in solution a positively charged surface-active ion containing an aliphate hydrocarbon group of at least 8 carbon atoms, e.g., quaternary ammonium compounds, particularly those containing a hydrocarbon group of 12-18 carbon atoms. Salts of higher aliphatic amines are suitable, e.g., dodecylamime hydrochloride or a mixture of the hydrochlorides of the aliphatic amines corresponding to the fatty acids in cocoanut oil. The amount of collector, which is preferably added in stages in solution in water, is regulated according to the nature of the minerals it is desired to remove, the collectors having preferential affinity for micas, feldspars, silica, iron oxides, and calcite, in that order. Iron oxides and calcite may be removed from the concentrate by a cleaning flotation with or without additional reagents. The air supply in both flotation operations is preferably reduced below normal. The various products obtained may be combined in different ways according to the type of cement required. Specifications 463,261 and 478,275, and U.S.A. Specification 2,132,902 also are referred to.