Study On Recovery Of Sulfur From Zinc-Oxygen Pressure Direct Leaching Residue

Zinc-oxygen pressure leaching residue is a smelting waste residue produced in the oxygen pressure leaching process of sphalerite.Because the leaching residue contains a large amount of elemental sulfur,it has high recycling value.However,the mineral phase in the leaching residue is seriously wrapped,and the existing flotation process is difficult to completely recover the elemental sulfur.In order to realize the efficient recovery of sulfur in leaching residue,this study first systematically studied the occurrence state and dissociation characteristics of elemental sulfur and other main components in leaching residue by process mineralogy,and then proposed a new process of separation and recovery of elemental sulfur by n-decane.The process parameters of separation and recovery of elemental sulfur by atmospheric distillation and vacuum distillation were compared and explored,which provided a certain reference for the recovery of elemental sulfur in leaching residue.The process mineralogy analysis of zinc-oxygen pressure leaching residue was carried out,and the element content,phase composition and inter-component embedding characteristics of the residue were clarified.The total sulfur in the leaching residue was 42.77%,of which the sulfur in the form of elemental sulfur was 24.36%,accounting for 56.95% of the total sulfur.Other sulfur-containing minerals are sulfate minerals mainly composed of iron sulfate,lead alum,calcium sulfate,barite,sulfide minerals mainly composed of marmatite,pyrite,chalcopyrite,arsenopyrite,galena,and gangue minerals such as quartz,chlorite,feldspar,talc,muscovite.There is a complex symbiotic relationship between the elemental sulfur of the target mineral and other minerals,which are mutually coated or closely embedded,which has a certain adverse effect on the recovery of elemental sulfur.The results of separation and recovery of elemental sulfur from n-decane show that elemental sulfur is dissolved in n-decane in the form of complex,and the solubility increases with the increase of temperature.Washing and grinding the leaching residue before n-decane sulfur extraction can significantly improve the extraction rate of elemental sulfur.The optimum conditions for the extraction of elemental sulfur from n-decane were obtained: temperature130 °C,liquid-solid ratio 10:1 m L/g,reaction time 5 min,stirring speed 300 rmp.Under the optimal process conditions,the extraction rate of sulfur in the leaching residue can reach99.15%,and the separation of elemental sulfur in the leaching residue is realized.The analysis results of the desulfurization slag show that the spherical elemental sulfur in the slag is removed,and the granular and lamellar sulfate and gangue components become the main phase.The results of sulfur recovery experiments show that although the sulfur recovery rate of evaporation crystallization is higher than that of cooling crystallization,the recovery rate of cooling crystallization sulfur also increases significantly with the increase of cycle times.When using distillation to separate and recover elemental sulfur,the optimum process parameters under normal pressure are: temperature of 280 °C,holding time of 90 min,and material layer thickness of <1.0 cm.Under this optimal condition,99.65% of elemental sulfur in the leaching residue can be volatilized.The optimal process parameters of vacuum distillation:residual pressure <50 Pa,temperature 180 °C,holding time 90 min,material layer thickness<1.3 cm.Under this optimal condition,99.98% of elemental sulfur in the leaching residue can be volatilized.The analysis results of the distillation residue showed that the phase of the finishing residue changed and the iron sulfate phase disappeared at atmospheric pressure.The main reason was that the iron sulfate and elemental sulfur reacted at high temperature to form an amorphous substance,and some minerals melted and adhered.Under vacuum conditions,the phase did not change due to the lower temperature,and most of them existed in lamellar small particles.