Study On Zinc Removal From Waste Tire Rubber Powder

With the rapid development of automobile industry,the production of waste tires is increasing year by year.It has great value in heat energy utilization and can replace pulverized coal as blast furnace fuel.It will lead to waste of resources if it is stacked in large quantities for a long time.However,the waste tire contains a small amount of zinc,which will harm the blast furnace in the combustion process and shorten the service life of the blast furnace.If effective methods can be found to remove zinc from waste tire rubber powder,it can be used as fuel for blast furnace,which is of great significance for the resource utilization of waste tires.In this paper,the zinc removal of waste tire rubber powder was studied by different methods,and the condition parameters were optimized.The surface morphology,phase composition and element valence of waste tire rubber powder before and after reaction were characterized by scanning electron microscopy?SEM-EDS?,X-ray diffraction?XRD?and X-ray photoelectron spectroscopy?XPS?to study the reaction mechanism of zinc removal.Finally,the calorific value of waste tire rubber powder after zinc removal and the morphology of zinc after reaction were studied,which showed that the process of recycling waste tire rubber powder after zinc removal was feasible.The conclusions are as follows:?1?The zinc content in waste tire rubber powder was determined by tetraacid digestion combined with hydrochloric acid-sulphuric acid-perchloric acid-hydrofluor-ic acid and EDTA titration.Compared with the national standard method,the method has higher accuracy and accuracy.The method is reliable,simple and easy to operate.?2?Different acid and alkali leaching methods were used to remove zinc from waste tire rubber powder?particle size ranged from 3 mm to 5 mm?.The results showed that when hydrochloric acid,sulfuric acid and NaOH were used as leaching agents,the zinc removal rate was about 5%,which was far below the target value?zinc content of rubber powder was less than 0.5%?.When nitric acid was used as leaching agent,the zinc removal rate was as high as 81.29%,but nitric acid would decompose the structure of waste tire rubber powder and influence its combustion calorific value.The removal rates of zinc by alkali fusion were 12.52%and 7.57%respectively,which were far lower than the target value?zinc content of rubber powder<0.5%?.?3?Different acid-base leaching agents were used to extract refined waste tire rubber powder.The optimum leaching conditions of waste tire rubber powder were as follows:particle size less than 150 um rubber powder+0.1 mol/L sulfuric acid solution+liquid-solid ratio 20:1+reaction temperature 90 C+leaching time 60 min,the leaching rate could reach 75.65%,which was higher than the target value?zinc content of rubber powder<0.5%?.Kinetic analysis of the leaching reaction of waste tire rubber powder showed that the activation energies of the leaching reaction in 0-20min and 20-90 min were 41.39 kJ/mol and 49.49 kJ/mol respectively,which were within the range of 40-300 kJ/mol controlled by interfacial chemical reaction,so the whole leaching process was controlled by interfacial chemical reaction.?4?The mechanism of sulfuric acid leaching of waste tire rubber powder was studied.The results show that zinc mainly exists in the form of ZnO and ZnS on the surface of rubber powder,and a small amount of cordierite((Fe²⁺,Mg)₂Al₄Si₅O₁₈)is distributed on the surface of rubber powder.In addition to Zn,Al,Mg,Fe,S,Si and other elements also participate in the leaching process of sulfuric acid.?5?The calorific value of waste tire rubber powder after leaching was determined.It was found that the low calorific value of waste tire rubber powder before and after leaching was 32.83 MJ/kg and 36.02 MJ/kg,respectively.Therefore,the scrap tire rubber powder after zinc removal as blast furnace fuel has great feasibility.At the same time,the theoretical analysis results show that zinc can be recovered by electrolysis from the leaching solution obtained by zinc removal process of waste tire rubber powder.It is concluded that the whole process of acid leaching and electrolytic zinc recovery from waste tire rubber powder is feasible.