Patent GB-763936-A (GB)
Title: Improved method for the recovery of sulphur from ores
IPC: C01G1/12
Filed: 1954-06-11
Abstract: Elemental sulphur is recovered from impure sulphur by dispersing the impure sulphur in water or dilute sulphuric acid solution to form a slurry, heating the slurry to above the melting point of sulphur to agglomerate the sulphur into liquid pellets, separating the sulphur pellets and dispersing them in water containing a surface modifying agent for the impurities associated with the sulphur, whereby the impurities are preferentially water wetted, heating the dispersion above the melting point of sulphur for a time sufficient to obtain optimum segregation of sulphur from the impurities and reagglomeration of the sulphur, and cooling to solidify sulphur which is separated. The impurities which may be metal sulphide values may be separately recovered as concentrates.  The agglomeration may be effected by dispersing 35-50 per cent solids in water, or dilute sulphuric acid preferably at pH 3.3-3.5, but not below 1, and heating to above the melting point of sulphur up to 290 DEG F., preferably 250-260 DEG F. with agitation.  Cooling is effected by dilution with water, or flashing off steam, and the pellets screened.  The agglomerated solids, which may include metal sulphides, may be subjected to a conventional froth flotation, in which case the large size pellets removed by screening may be recycled to agglomeration or subjected to separate treatment, e.g. by melting, to recover sulphur. The froth flotation is effected with a 15-25 per cent solids slurry at pH 3.3-3.5 with pine oil or sodium discresyldithiophosphate sulphur collector in three stages of two rougher cells and one cleaner cell.  The resultant solids, mainly iron oxide, after thckening tailings from the rougher cells, may be recovered, or recycled to the rougher cells, and water may also be recycled.  The agglomerated solid without flotation concentration, or the overflow concentrate of sulphur from the cleaner flotation cell, is dispersed as 35-50 per cent solids in water containing the surface modifying agent and heated with agitation to preferably, 260-290 DEG F. Surface modifying agents are froth flotation sulphide depressants, e.g. alkaline earth metal oxides or hydroxides, such as lime, alkali metal cyanides or silicates, such as sodium silicate, sodium carbonate or hydroxide, limestone, or organic depressants, such as tannin, quebracho, nigrosin, dextrin, or lignin sulphonates.  The reagglomerated sulphur is cooled and screened or subjected to further flotation concentration and examples refer to separate recovery of substantially pure sulphur, and a concentrate of nickel, copper, and iron sulphides.  The impure sulphur may be obtained from native sulphur-bearing ores, or pyrrhotitic or pyritic sulphide ores or concentrates from which sulphide sulphur has been released.  A number of minerals containing iron, arsenic, copper, cobalt, nickel, and antimony are named as suitable. Preferably pyrrhotitic sulphide ores, including sulphide material resulting from partial oxidation by roasting pyrites minerals, of size 35-325, Tyler screen are dispersed in water or an aqueous sulphuric acid solution.  Oygen, air, or oxygen enriched air is passed through the dispersion, which is agitated, at an oxygen partial pressure of preferably 25-100 p.s.i. The oxidation may be carried out at below the melting point of sulphur, when a pure sulphur product is required, in which case the dispersion is heated to above the melting point after oxidation for agglomeration.  Alternatively, when a concentrate of mineral sulphides and/or precious metals is also required, the oxidation is effected at above the melting point of sulphur, so that the mineral sulphides are occluded in the liquid sulphur, and agglomeration is effected at the same time.  Specifications 722,143 and 760,624 are referred to.ALSO:Elemental sulphur is recovered from impure sulphur by dispersing the impure sulphur in water or dilute sulphuric acid solution to form a slurry, heating the slurry to above the melting point of sulphur to agglomerate the sulphur into liquid pellets, separating the sulphur pellets and dispersing them in water containing a surface modifying agent for the impurities associated with the sulphur, whereby the impurities are preferentially water wetted, heating the dispersion above the melting point of sulphur for a time sufficient to obtain optimum segregation of sulphur from the impurities and reagglomeration of the sulphur, and cooling to solidify sulphur which is separated. The impurities which may be metal sulphide values may be separately recovered as concentrates. The agglomeration may be effected by dispersing 35-50 per cent solids in water, or dilute sulphuric acid preferably at pH 3.3-3.5, but not below 1, and heating to above the melting point of sulphur up to 290 DEG F., preferably 250-260 DEG F. with agitation.  Cooling is effected by dilution with water, or flashing off steam, and the pellets screened.  The agglomerated solids, which may include metal sulphides, may be subjected to a conventional froth flotation, in which case the large size pellets removed by screening may be recycled to agglomeration or subjected to separate treatment, e.g. by melting, to recover sulphur.  The froth flotation is effected with a 15-25 per cent solids slurry at pH 3.3-3.5 with pine oil or sodium discresyldithiophosphate sulphur collector in three stages of two rougher cells and one cleaner cell.  The resultant solids mainly iron oxide, after thickening tailings from the rougher cells may be recovered, or recycled to the rougher cells, and water may also be recycled.  The agglomerated solid without flotation concentration, or the overflow concentrate of sulphur from the cleaner flotation cell, is dispersed as 35-50 per cent solids in water containing the surface modifying agent and heated with agitation to preferably, 260-290 DEG F.  Surface modifying agents are froth flotation sulphide depressants, e.g. alkaline earth metal oxides or hydroxides, such as lime, alkali metal cyanides or silicates, such as sodium silicate, sodium carbonate or hydroxide, limestone, or organic depressants, such as tannin, quebracho, nigrosin, dextrin, or lignin sulphonates. The reagglomerated sulphur is cooled and screened or subjected to further flotation concentration, and examples refer to separate recovery of substantially pure sulphur, and a concentrate of nickel, copper, and iron sulphides.  The impure sulphur may be obtained from native sulphur-bearing ores, or pyrrhotitic or pyritic sulphide ores or concentrates from which sulphide sulphur has been released.  A number of minerals containing iron, arsenic, copper, cobalt, nickel, and antimony are named as suitable. Preferably pyrrhotitic sulphide ores, including sulphide material resulting from partial oxidation by roasting pyrites minerals, of size 35-325, Tyler screen are dispersed in water or an aqueous sulphuric acid solution.  Oxygen, air, or oxygen enriched air is passed through the dispersion, which is agitated, at an oxygen partial pressure of preferably 25-100 p.s.i. The oxidation may be carried out at below the melting point of sulphur, when a pure sulphur product is required, in which case the dispersion is heated to above the melting point after oxidation for agglomeration.  Alternatively, when a concentrate of mineral sulphides and/or precious metals is also required, the oxidation is effected at above the melting point of sulphur so that the mineral sulphides are occluded in the liquid sulphur and agglomeration is effected at the same time.  Specifications 722,143 [Group III] and 760,624 are referred to.