Basic Research On Production Of Sulphoaluminate Cement By Cyanidation Tailings

Since the cyanide leaching process was used in industrial production in 1887,the process has been the main way of gold and silver production with high leaching efficiency,lower cost and better adaptability to different minerals.The highly toxic cyanide makes cyanide in the tailings and cannot be directly discharged.Therefore,cyanide tailings accumulation becomes a problem.In this paper,the cyanide residue was used as a substitute for iron and sulfur materials in sulphoaluminate cement clinker.The effects of component design,raw material selection,sintering temperature and holding time on the sintering process,sulfur fixation rate and f-CaO content were studied,and the influence of gypsum addition on the hydration performance of clinker was also explored.The research results show that when using cyanide tailings instead of cement S and Fe materials,CaO should be used as calcium raw material,and the material design should be designed according to C4A3S,C4AF and C2S.When CaCO3 is used as the calcium raw material,which commonly used in industry,the f-CaO content in the clinker after sintering is high,the reaction of the material is not sufficient,and the loss of S in the raw material is more,reaching 26.63%.The use of CaO as a raw material can well solve the problem of insufficient reaction in the clinker sintering process.Adding a slight excess of CaO can reduce the loss of S.Clinker firing can be roughly divided into three processes.The first process is pyrite oxidation and preliminary sulfur fixation process below 1000℃.During this process,S is effectively retained in CaSO4,Fe is oxidized to Fe2O3,The second process is a rapid reaction zone from 1100～1200 ℃.In this temperature range,C4A3S is rapidly and mass-produced,and CaO reacts rapidly with other phases.The third process is the perfection of the phase above 1200℃.The main phase C4A3S and the iron phase are perfected,and the impurity phase is reduced.The optimum sintering temperature is 1300℃ in the experimental selected temperature range,and the suitable holding time is 20～60 min.The heat preservation contributes to the reaction of the phase.When the sintering temperature is low,the clinker contains more f-CaO,the reaction is incomplete,and when the sintering temperature is too high,part of C4A3S is decomposed,which increases the loss of S.When holding for 20～60 min,the phase of the clinker basically does not change,and it is in the state of forward firing.The time continues to extend,and the clinker is in the state of overheating.The addition of gypsum promotes the hydration of the cement,and the compressive strength of the cement increases significantly after the addition of the gypsum.Experiments on different gypsum dosage conditions found that the optimum gypsum content selected for the experiment was 25%.The excessively high and low gypsum content was not conducive to the development of cement clinker strength.Adding a small amount of limestone on the basis of adding gypsum has a regulating effect on hydration,which can increase the compressive strength of the cement block,effectively solve the problem of shrinkage of the compressive strength of the clinker,and make the cement strength grow steadily.