GB758170A - Process and production of granular, non-caking ammonium sulphate-ammonium nitrate - Google Patents

Abstract

Granular non-caking ammonium sulphate-ammonium nitrate is obtained by subjecting after granulation a slightly acid ammonium sulphate-ammonium nitrate mixture which contains an added iron salt to treatment with gaseous ammonia to produce iron hydroxide and/or oxide substantially only on the surface of the granules. According to an example an ammonium sulphate-ammonium nitrate melt was produced in a saturator by introducing nitric and sulphuric acids and gaseous ammonia and adding about 0.8 per cent of phonolite and 0.8 per cent of iron sulphate. During the cooling and solidification of the melt it was granulated in a worm followed by a rotary drum whereby a white granular sulphate nitrate mixture containing 0.4 to 0.5 per cent Fe2O3 as ferric sulphate and 0.1 per cent or less of free acid was obtained. Gaseous ammonia and small amounts of water vapour were passed into the rotary drum whereby about 0.1 per cent of Fe2O3 in the form of brown iron hydroxide was formed on the surface of the granules. The treated fertilizer was further cooled by passing it over louvred surfaces through which cooled air was passed upwardly. Alternatively gaseous ammonia may be blown directly into the cold air used for cooling the material in which case small amounts of water vapour are supplied through nozzles to the sulphate-nitrate granules as they are transferred from the rotary drum to the cooling device, in which case the apparatus of Specification 665,032 [Group XIII] may be used.ALSO:Granular non-caking ammonium sulphate-ammonium nitrate is obtained by subjecting after granulation a slightly acid ammonium sulphate-ammonium nitrate mixture which contains an added iron salt to treatment with gaseous ammonia to produce iron hydroxide and/or oxide substantially only on the surface of the granules. According to an example, an ammonium sulphate-ammonium nitrate melt was produced in a saturator by introducing nitric and sulphuric acids and gaseous ammonia and adding about 0.8 per cent of phonolite and 0.8 per cent of iron sulphate. During the cooling and solidification of the melt it was granulated in a worm followed by a rotary drum whereby a white granular sulphate nitrate mixture containing 0.4 to 0.5 per cent Fe2O3 as ferric sulphate and 0.1 per cent or less of free acid was obtained. Gaseous ammonia and small amounts of water vapour were passed into the rotary drum whereby about 0.1 per cent of Fe2O3 in the form of brown iron hydroxide was formed on the surface of the granules. The treated fertilizer was further cooled by passing it over louvred surfaces through which cooled air was passed upwardly. Alternatively, gaseous ammonia may be blown directly into the cold air used for cooling the material in which case small amounts of water vapour are supplied through nozzles to the sulphate nitrate granules as they are transferred from the rotary drum to the cooling device, in which case the apparatus of Specification 665,032 [Group XIII] may be used.