Patent GB-342318-A (GB)
Title: Improvements in or relating to the treatment of ammoniacal liquors obtained in scrubbing gases and the recovery of fertilizers and other products therefrom
IPC: C05B7/00
Filed: 1929-08-20
Abstract: A manure is produced by treating with phosphoric acid used ammoniacal liquors from the scrubbing of gases, e.g. coal distillation gases, with liquors containing sulphites and/or thionates.  The reaction is preferably carried out with heating and under pressure.  The manures are recovered from the treated liquors by evaporation and crystallization.  A used liquor containing only sulphites treated with phosphoric acid in this way gives ammonium phosphate and sulphur dioxide.  When the used liquor contains thionates, ammonium phosphate, sulphur dioxide and sulphur are the main products with excess phosphoric acid whereas when the amount of phosphoric acid is limited substantial amounts of ammonium sulphate are also formed and no sulphur dioxode is liberated.  Liquors containing cyanogen compounds removed from the gases in a preliminary scrubbing operation may be mixed with the used sulphite or thionate liquors and the mixture treated with phosphoric acid; the quantity of phosphoric acid added is preferably such that as much of the sulphite or thionate remains undecomposed as is required for combining the sulphur dioxide liberated by the phosphoric acid.  Alternatively, these liquors containing cyanogen compounds may be treated with phosphoric acid and the product obtained mixed with the product obtained by treating the used sulphite and thionate liquors with phosphoric acid.  Ammonia contained originally in the gases and removed in a prior scrubbing operation may be added to the phosphoric acid containing reaction liquors.  Sulphur dioxide produced in the decomposition of the used liquors with phosphoric acid may be used for regenerating the wash liquors.  When a metal salt is used in the washing solution, the metal is eliminated before treating with phosphoric acid by precipitating the metal as sulphide with hydrogen sulphide and filtering off the metal sulphide. Specification 309,116, [Class 55 (ii), Gas manufacture &c.], is referred to.ALSO:A manure is produced by treating with phosphoric acid used ammoniacal liquors from the scrubbing of gases, e.g. coal distillation gases, with liquors containing sulphites and/or thionates.  The reaction is preferably carried out with heating and under pressure.  The manures are recovered from the treated liquors by evaporation and crystallization.  A used liquor containing only sulphites treated with phosphoric acid in this way gives ammonium phosphate and sulphur dioxide.  When the used liquor contains thionates, ammonium phosphate, sulphur dioxide and sulphur are the main products with excess phosphoric acid whereas when the amount of phosphoric acid is limited substantial amounts of ammonium sulphate are also formed and no sulphur dioxide is liberated.  Liquors containing cyanogen compounds removed from the gases in a preliminary scrubbing operation may be mixed with the used sulphite or thionate liquors and the mixture treated with phosphoric acid; the quantity of phosphoric acid added is preferably such that as much of the sulphite or thionate remains undecomposed as is required for combining the sulphur dioxide liberated by the phosphoric acid.  Alternatively, these liquors containing cyanogen compounds may be treated with phosphoric acid and the product obtained mixed with the product obtained by treating the used sulphite and thionate liquors with phosphoric acid.  Ammonia contained originally in the gases and removed in a prior scrubbing operation may be added to the phosphoric acid containing reaction liquors.  Sulphur dioxide produced in the decomposition of the used liquors with phosphoric acid may be used for regenerating the wash liquors.  When a metal salt is used in the washing solution, the metal is eliminated before treating with phosphoric acid by precipitating the metal as sulphide with hydrogen sulphide and filtering off the metal sulphide. Specification 309,116, [Class 55 (ii), Gas manufacture &c.], is referred to.