Research On The Technology Of Wet Treatment And Comprehensive Utilization Of Aluminum Electrolysis Overhaul Sla

Aluminum electrolysis Spent potlining belongs to hazardous waste,China produces more than 1 million tons of Spent potlining every year,and its treatment is difficult and costly,which brings greater environmental and economic pressure to enterprises,how to achieve low-cost treatment and comprehensive utilization of Spent potlining is a problem that needs to be solved in China’s aluminum industry.This thesis is aimed at the Spent potlining harmless and resourceful application of the key issues such as the separation of components is difficult,cyanide treatment is difficult,the comprehensive utilization rate of resources is low,carried out Spent potlining wet leaching,oxidation cyanide,leach solution preparation cryolite and liquid-solid-phase resourceful utilization of experimental research,the development of a wet leaching-ultrasonic synergistic cyanide breaking-carbon neutralization transformation of cryolite-the whole components of the resourceful utilization of the technical program,to achieve F in the Spent potlining.It realizes efficient leaching of F in Spent potlining and harmless treatment of cyanide,and prepares cryolite,anode carbon block,anti-seepage material,slag beating agent and other products,realizing harmless treatment and comprehensive utilization of resources of aluminum electrolysis Spent potlining.Specific research contents and results are as follows:（1）Analysis and testing by means of XRF and XRD show that the cathode carbon block is mainly composed of graphite,amorphous carbon,alumina,metallic aluminum,cryolite and other substances,of which carbon,alumina and electrolyte account for the main part;the refractory material is mainly composed of quartz,sodium aluminosilicate and other substances;and the cathode mixture is mainly composed of electrolyte,alumina,carbon,aluminosilicate and other substances.The carbon material,alumina and fluoride in the cathode charcoal briquette are wrapped or hyphenated with each other,which is difficult to separate,and it is necessary to crush the cathode charcoal briquette to separate it effectively.（2）The leaching principle under different conditions was studied,and the leaching reaction was analyzed thermodynamically,on the basis of which experiments on water leaching,acid leaching and alkaline leaching of Spent potlining were carried out,and the effects of particle size,temperature,liquid-solid ratio,time,reactant concentration and other factors on the leaching effect were investigated.The best normal pressure alkaline leaching process was obtained,the F leaching rate was>85%,but the time of normal pressure leaching was longer;Pressurized alkaline leaching can improve the leaching rate while significantly shortening the leaching time,the optimal leaching conditions were as follows:alkali concentration of 100 g/L,temperature of 120℃,pressure of 0.3Mp,time of 60 min,liquid-solid ratio of 5:1,particle size of 120 mesh,F leaching rate reach 87.5%,Na leaching rate reach 90%,leaching residue of arsenic,beryllium and other 15 toxicity detection factors do not exceed the GB/T5085.3-2007"Hazardous Waste Identification Standards-Leaching Toxicity Identification"concentration limit,fluoride test results for 63.4 mg/L,cyanide test results for<0.004 mg/L,leaching residue fully meet the requirements of harmless,belongs to the general Solid waste.Among several leaching processes,pressurized alkaline leaching will not precipitate toxic and harmful gases,and has the best leaching effect and the highest leaching efficiency.（3）Carried out experimental research on cyanide breaking by oxidation of Spent potlining leach solution,and obtained the optimal process conditions for cyanide breaking by ultrasonic synergistic oxidation,with an average cyanide removal rate of99.98%,and an average concentration of cyanide in cyanide-breaking solution of 0.010mg/L.Compared with conventional cyanide breaking by hydrogen peroxide,the ultrasonic synergistic oxidation of cyanide breaking can reduce the dosage of hydrogen peroxide from 16 times of the theoretical amount of hydrogen peroxide to 6 times of the theoretical amount of hydrogen peroxide and shorten the reaction time at the same time.The reaction time was shortened.The mechanism of ultrasonic synergistic oxidation for cyanide breaking was explored:the cavitation effect generated by ultrasonic waves produced cavitation bubbles,which collapsed to produce transient high temperature and high pressure,and the energy provided by transient high temperature and high pressure strengthened the breakage of the C-N chemical bond to produce C⁴⁺and N^5-,which were combined with O₂^2-,reactive oxygen species（ROS）[O],and H⁺to produce HCO^3-,and N^5-was oxidized by ROS,ROS to N₂ and escaped from the solution as a gas.（4）The experimental study of carbon neutralization and transformation of cryolite has been carried out,and the optimal process conditions for carbon neutralization and precipitation of cryolite have been obtained,and the addition of ultrasonic waves in the process of carbon neutralization can improve the purity of cryolite.The mechanism of ultrasonic synergistic carbon fraction neutralization and transformation of cryolite was explored:ultrasonic intensification can promote the migration of carbon dioxide into the liquid phase,enhance the mass transfer effect of sodium,fluorine,aluminum and other ions,and provide energy for the chemical reaction,and at the same time,the role of the mechanical effect of ultrasonic waves can dissociate the impurities from the surface of cryolite crystals,which can improve the purity of cryolite;experimental research on desilication treatment was carried out on the product of carbon fraction and obtained the The optimal process conditions were obtained,and the silicon removal rate reached more than 97.07%,which meets the standard requirements of industrial cryolite products.（5）According to the nature of various materials produced in the process of overhauling slag,we have developed five waste channel lining resource utilization technologies,prepared aluminum and aluminum alloy melt slagging agent,energy-saving and environmentally friendly pre-roasted anode,electrolysis tank corner roasting carbon particles,regenerated seepage-proof material,electrolysis tank artificial leg extension,and new type of electrolysis tank start-up heat preservation material,which have been popularized and applied in the electrolytic aluminum plant,realizing the comprehensive utilization of the Spent potlining resourceization.The first domestic production line of harmless and high-value comprehensive utilization of 5,000 tons and above waste tank lining hazardous waste residue has been built,with an average treatment cost of 754.49 RMB/ton,realizing a direct economic benefit of RMB8,912,800 yuan.This thesis reveals the mechanism of wet leaching of Spent potlining,ultrasonic synergistic cyanide breaking,carbon fraction neutralization and transformation of cryolite,develops the technology of alkaline leaching of Spent potlining-ultrasonic synergistic cyanide breaking-carbon fraction neutralization and transformation of cryolite,realizes the resourceful and comprehensive utilization of Spent potlining,and carries out the industrial test,which provides a new idea and method for the harmless treatment of the Spent potlining and the resourceful and comprehensive utilization of the Spent potlining.