Patent GB-426423-A (GB)
Title: Manufacture of cement
IPC: B03D1/02
Filed: 1933-11-24
Abstract: Lime and silica-containing raw materials used for cement manufacture are treated by froth flotation to separate lime from siliceous constituents.  It is preferred to form a pulp with an excess of water so that impurities are removed with the overflow. A suitable flotation agent consists of equal parts of oleic acid and cresol. Calcite is floated off and the residue separated by means of a concentration table.  A second flotation may be effected and the residue concentrated to give a pure silica.ALSO:In preparing a mixture of cement-forming raw materials from original materials all or a lime-bearing component of which contains lime and siliceous constituents, one of which is present in undesirable quantity, part of the original material is treated by froth flotation to separate the lime from the siliceous constituent, the excess is discarded, and the remaining treated material combined with the untreated part. Where the original materials contain silica in excess or in a form unsuitable for burning, at least part of said materials is subjected to classification to separate fine and coarse particles, and the latter treated by froth flotation to separate lime and silica, the latter being discarded.  A micaceous limestone deficient in lime, after preliminary grinding is passed to finish mills adjusted to give a coarser product than the normal.  Owing to the greater hardness of the quartz present, the fines produced have an increased proportion of calcium carbonate.  The discharge from the mills is separated by air or hydraulic classification and part of the tailings, the amount depending on the quantity of silica it is desired to discard, is treated by froth flotation.  It is preferred to form a pulp with an excess of water so that deleterious materials are removed with the overflow, the flotation agent being equal parts of oleic acid and cresol, present in an amount of about 1 1/2 lbs. per ton of tailings. The calcite is floated off and the deposit in the cells may be separated by a concentration table to obtain the iron if its addition to the final cement mixture is necessary.  In some cases, a second flotation operation is effected and, by concentrating the residue, pure silica is obtained as a byproduct.  The calcite is dried, if necessary, and returned to the finish mills with the other constituents.  In a modification, the separation is effected before the materials are fed to the finish mills.  Where the original materials comprise at least two components, for example, a marl or chalk and a clay or shale, it may be necessary to treat one component only, if the other does not contain coarse silicas. This component is classified, the coarse particles treated by flotation, and the silica discarded.  Alternatively, both components may contain coarse silicas in which case relative quantities thereof are treated such that the excess silica is equal to the total amount of coarse silicas.ALSO:In producing a cement-forming mixture from natural lime and silica-containing rocks, or from a mixture of components such as marls or chalks and clays or shales, the materials containing one constituent in undesirable amount, the materials are treated by froth flotation to float off the calcium carbonate from the silica, the excess constituent then being discarded.  A pulp may be formed with an excess of water so that impurities such as graphite and alkalies are removed with the overflow.  A suitable flotation agent consists of equal parts of oleic acid and cresol, used in an amount of about 1 1/2 lbs. per ton treated.  The deposit in the cells may be separated by a concentration table to obtain the iron if its addition to the final cement mixture is required.