Basic Research On The Co-Preparation Of Zinc-Containing Dust By Hydrogen Reduction Dezincification And Iron-Carbon Micro-Electrolysis Materials

Iron and steel industry is an important basic industry in China,and its CO₂ emissions account for about 33%of the total industrial emissions.At the same time,it is also a large solid waste emitter,among which the annual output of zinc containing dust solid waste up to 20 million tons.The traditional zinc dust fire process mainly uses solid carbon as reducing agent,which has many problems such as high reaction temperature,high energy consumption,high carbon emission,poor quality of secondary zinc oxide and low added value of metallized charge.It cannot adapt to the new trend of green and low-carbon development in China,and seriously restricts the high-quality development of iron and steel industry.It is of great significance to develop a new process for green and high value utilization of zn-containing dust.In this paper,the basic physical and chemical properties and process mineralogical characteristics of zinc dust pellets in iron and steel mills were systematically investigated.The thermodynamic behavior and kinetic mechanism of direct hydrogen reduction of zinc-bearing dust pellets were elucidated.The phase and microstructure evolution law of carbon pellets（ICME materials）during hydrogen reduction were revealed.The structure-activity relationship between the structure of ICME material and the degradation performance of organic wastewater was established.A new process for the co-preparation of ICME material and zinc containing dust by hydrogen reduction was developed.The main conclusions of this paper are as follows:（1）The physical and chemical properties of the zinc dust showed that the content of iron and zinc in the secondary ash of blast furnace was 34.76%and2.11%,and zinc mainly existed in the form of zinc oxide and zinc ferrite,with carbon content as high as 26.37%,which could provide carbon source for ICME materials.The content of iron in blast furnace ash,LT ash and OG mud is up to62.86%,56.38%and 59.46%,respectively,which can provide iron source for ICME materials.In addition,the four zinc dust slime have very fine particle size and very high specific surface area,which can improve the contact area between the anode and cathode,accelerate the electrochemical reaction speed,and improve the performance of ICME materials.（2）Thermodynamic studies show that zinc ferrite can be reduced to Zn O at lower temperatures.When the system temperature is higher than 780℃,zinc oxide is easier to reduce than iron oxide.In the process of hydrogen reduction,the H₂/（H₂+H₂O）ratio required for zinc oxide reduction is only 45.56%at800℃.The temperature and H₂ concentration of zinc oxide reduction volatilization and iron reduction to metal iron are easy to achieve,which can realize the coordination of zinc oxide reduction and zinc reduction volatilization of zinc dust based on hydrogen metallurgy.（3）Kinetics of direct hydrogen reduction of zn-containing dust pellets showed that:Under the condition of 800℃～950℃,the limiting link of iron oxide and zinc oxide reduction is controlled by interfacial chemical reaction,and the apparent activation energy is 16.42KJ·mol^-1and 71.39 KJ·mol^-1,respectively,which is far less than the apparent activation energy of carbon thermal reduction,indicating that iron and zinc oxides are easily reduced in hydrogen reduction system.（4）The study on the new process of hydrogen reduction dezincification of zinc-containing dust and co-preparation of iron-carbon micro-electrolysis material shows that the dezincification rate and lead rate are 96.8%and 71.1%respectively under the reduction temperature of 950℃,reduction time of 30min and H₂ flow rate of 10L/min.Meanwhile,Fe/C of 15:1,specific surface area of6.728m²/g and porosity of 65.49%were prepared.（5）Studies on the relationship and application of ICME microelectrolysis effect show that compared with commercial ICME materials,the ICME materials prepared in this paper have higher specific surface area,more developed pore structure and tighter iron-carbon bonding mode.In the case of slightly larger Fe/C,they have similar sewage treatment effect to commercial ferrocarbon materials.