Patent GB-967578-A (GB)
Title: Curing salt composition and method of manufacturing it
IPC: A23B4/023
Filed: 1963-05-14
Abstract: A curing salt composition made from a granular mixture of substantially uniform composition of a major proportion of homogeneous sodium chloride crystals and a minor proportion of alkali-metal nitrite and/or alkali-metal nitrate or such nitrite and nitrate mixed as crystals or combined by fusion, all with or without a small amount, e.g. up to 4%, of water, and in which the individual particles essentially each contain all the ingredients of the starting mixture in substantially the same proportions as in the starting mixture, is produced by compacting a quantity of such a mixture by effective mechanical pressure to bonded cake form and a mass of such caked forms is reduced in size while substantially dry to form heterogeneous crystalline particles much coarser than the starting mixture.  When a granular free-flowing product is desired the caked agglomerated material is comminuted to a desired fineness coarser than a particle size which cakes on standing and also coarser than that of the starting material before compaction. The compacting may be done by passing a mass of the original crystals through the nip of heavy compression rolls exerting pressures of the order 5,400-14,500 pounds per linear inch of roll so that sheet-like forms are produced of between 1/16 th and 1/8 th inch thickness, by mechanically compressing into cake, pellet or briquette form or by extruding a rod-like form and chopping pellets as they are extruded. The size reduction, which is effected on caked material that is dry or contains not more than 2% moisture, is effected by passing the cake several times through a bank of three sets of grinding rolls, each following set of rolls being more closely spaced.  Examples are directed to producing curing salt compositions from a fine-ground caking mixture of 90% by weight sodium chloride crystals with 6% sodium nitrite and 4% sodium nitrate by compacting the mixture dry or with up to 4% added moisture, drying to not more than 1% moisture and then grinding to a size coarser than the original mass; the product contained the ingredients of the initial mixture in the same proportions within 2% deviation from the theoretical content. Rejected fractions from the grinding may be recycled through the compaction procedure.  According to a further example, a solid fusion of 6 parts of sodium nitrite and 4 parts sodium nitrate is mixed with 90 parts of sodium chloride.  The two components may be separately ground, or the mixture may be ground so that all passes a 100-mesh U.S. Standard screen.  The fine ground mass is then compacted to cake form.  When the irregular caked forms are desired in a granular free-flowing state, they are so ground that all passes a 30-mesh screen, 50% remains on a 50-mesh screen, and about 10% passes a 200-mesh screen.  Such fractions are substantially uniform in nitrite content.  Potassium nitrite and/or nitrate may be substituted for the corresponding sodium salts.ALSO:A curing salt composition made from a granular mixture of substantially uniform composition of a major proportion of homogeneous sodium chloride crystals and a minor proportion of alkali-metal nitrite and/or alkali-metal nitrate or such nitrite and nitrate mixed as crystals or combined by fusion, all with or without a small amount, e.g. up to 4%, of water, and in which the individual particles essentially each contain all the ingredients of the starting mixture in substantially the same proportions as in the starting mixture, is produced by compacting a quantity of such a mixture by effective mechanical pressure to bonded cake form and a mass of such caked forms is reduced in size while substantially dry to form heterogeneous crystalline particles much coarser than the starting mixture.  When a granular free-flowing product is desired the caked agglomerated matarial is comminuted to a desired fineness coarser than a particle size which cakes on standing and also coarser than that of the starting material before compaction.  The compacting may be done by passing a mass of the original crystals through the nip of heavy compression rolls exerting pressures of the order 5,400-14,500 pounds per linear inch of roll so that sheet-like forms are produced of between 1/16th and 1/8th inch thickness, by mechanically compressing into cake, pellet or briquette form or by extruding a rod-like form and chopping pellets as they are extruded. The size reduction, which is effected on caked material that is dry or contains not more than 2% moisture, is effected by passing the cake several times through a bank of three sets of grinding rolls, each following set of rolls being more closely spaced.  Examples are directed to producing curing salt compositions from a fine-ground caking mixture of 90% by weight sodium chloride crystals with 6% sodium nitrite and 4% sodium nitrate by compacting the mixture dry or with up to 4% added moisture, drying to not more than 1% moisture and then grinding to a size coarser than the original mass; the product contained the ingredients of the initial mixture in the same proportions within 2% deviation from the theoretical content. Rejected fractions from the grinding may be recycled through the compaction procedure.  According to a further example, a solid fusion of 6 parts of sodium nitrite and 4 parts sodium nitrate is mixed with 90 parts of sodium chloride.  The two components may be separately ground, or the mixture may be ground so that all passes a 100-mesh U.S. Standard screen.  The fine ground mass is then compacted to cake form.  When the irregular caked forms are desired in a granular free-flowing state, they are so ground that all passes a 30-mesh screen, 50% remains on a 50-mesh screen, and about 10% passes a 200-mesh screen.  Such fractions are substantially uniform in nitrite content.  Potassium nitrite and/or nitrate may be substituted for the corresponding sodium salts.