Harmless Treatment And Recycling Of Sedimentary Planing Materials At The Bottom Of The Furnace

With the development of society,aluminum is playing an increasingly important role in people’s lives.In 2018,China’s total electrolytic aluminum output was 35.8 million tons.The increase in output means increased pollution.Aluminum electrolytic tanks will probably produce 38898.3.Tons of hearth sedimentation planer charge.These planer materials cannot be returned to the electrolytic cell for use,and most of them are accumulated in situ,which will cause environmental pollution and waste of resources.This thesis intends to use sulfuric acid roasting-water immersion technology to achieve the removal of fluorine and the recovery of alumina in the bottom of the furnace.The main ingredients in the furnace bottom precipitation planer are alumina and some fluorides,of which the alumina content is 50.53%,and the fluoride component is mainly cryolite.In this paper,a sulfuric acid roasting-water immersion process is designed for the harmless treatment of planer charge.The harmless treatment is mainly to convert the fluoride in the planer charge to hydrogen fluoride through sulfuric acid roasting,and recover alumina that does not participate in the reaction.Considering that the main fluoride in the planer charge is cryolite,the process research is first performed on cryolite.The orthogonal test design shows that the acid-material ratio has a significant effect on the roasting effect.The roasting temperature has a certain effect on the roasting effect.The effect on the roasting effect is small.The best process conditions obtained by single factor analysis are that the reaction acid-material ratio is 5:1,the reaction temperature is 250℃,and the reaction time is 2 h.It was found that the final product of cryolite after calcination and immersion in sulfuric acid was a mixture of hypocryolite and aluminum fluoride.It was judged that the reaction between sulfuric acid and cryolite was a process of gradually reacting with sodium fluoride in cryolite.Cryolite,aluminum fluoride,aluminum sulfate.The process of sulfuric acid roasting-water immersion furnace bottom precipitation planer was investigated.The orthogonal experiment design showed that the acid-material ratio and the roasting temperature had a significant effect on the roasting effect.The optimal process conditions are a reaction acid-to-material ratio of 4:1,a reaction temperature of 250℃,and a reaction time of 2 h.The final product is roasted by sulfuric acid-water immersion,the final product is relatively pure alumina.Because the products of cryolite and planer are different after roasting and water immersion treatment,the mechanism of roasting of cryolite and sulfuric acid is explored.The control experiments of industrial electrolyte and the addition of alumina are obtained.Effect,without adding alumina,the conversion rate of fluorine during the roasting process of pure cryolite and concentrated sulfuric acid is 81.12%.When cryolite and alumina are mixed in a 1:1 mass ratio with concentrated sulfuric acid and roasted,the fluorine conversion rate in the roasting process Up to 99.91%.