| With the increase in the use of hot-dip galvanized sheets in China's autos,home appliances,and other industries,the consumption of zinc ingots increases year by year,which has led to a sharp increase in the production of hot-dip galvanized slag.According to statistics,the dosage of hot-dip galvanizing in the country is as high as 800,000 tons per year,resulting in over 100,000 tons of hot-dip galvanizing slag.The 3,600 tons of hot-dip galvanized slag is produced by HBIS Group Hansteel Company each year.The horizontal vacuum furnaces were used to treat hot-dip galvanizing slag in Baosteel,Anshan Iron and Steel and Wuhan Iron and Steel.Nevertheless,they stopped running eventually due to the serious corrosion of galvanizing zinc and high maintenance rate.Moreover,the recycling effect of hot-dip galvanizing slag through double vacuum distillation method was also bad in Panzhihua Iron and steel company.In this paper,the research on the full efficient recycling of hot-dip galvanizing slag was carried out for the above problems,and a demonstration industrialized production line was established.Through the preliminary research in the laboratory,the vertical vacuum furnace was used for the pilot test and the rectification furnace was used for industrial production.At the same time,the preparation techniques of Mn-Zn ferrite,ultrafine zinc powder,and tetrapod nano-ZnO were studied.A process technology for directly preparing ultrafine zinc powder was studied by using hot-dip galvanizing slag as raw material.The method can avoid the secondary energy waste in the production of zinc powder by using crude zinc ingots which were prepared from hot-dip galvanizing slag to crude zinc ingots.In this work,the combination of fully enclosed nitrogen injection and rapid condensation method was applied,the related injection devices and condensing devices were exploited,and the schemes for solving the agglomeration of zinc powder and increasing the purity of zinc powder were proposed.The results show that the highest temperature control at 975?,the constant temperature time is 45min,the nitrogen flow rate is 11 L/min,and the small-scale zinc slag is controlled at about 70 g.The superfine zinc powder produced has a smooth surface,basically no zinc oxide,uniform particle size distribution,and good dispersion.In line with the requirements of the three level of the chemical composition of the superfine zinc powder enterprise and the requirement of 18 ?m particle size.The vertical vacuum furnace was used to prepare Zn metal from hot-dip galvanizing slag at the pilot test.The results show that the treatment of hot-dip galvanizing slag through vacuum distillation method is feasible,but there are still some problems that need to improve.The product of zinc block is an irregular shape,which needs to be remelted by ingot casting process before the production.However,it is difficult to adapt to large-scale industrial production due to the small handling capacity,intermittent operation,and simultaneous operation of multiple devices.The 990 type rectification furnace was used to deal with the hot-dip galvanizing slag at the industrialized production level.A new "three-bath" structure refining furnace was researched for the production of zinc ingots from hot galvanizing slag.A heat storage retorting furnace with new energy-saving technology through combustion of coke oven gas was studied.An automatic control system for rectifying furnace was developed for the disposition of hot-dip galvanizing slag.The hot-dip galvanizing slag can completely be dealt with rectification method,and the purity of zinc ingots product can reach more than 99.995%.By analyzing the factors and characteristics of rectification of Zn,the increasing recovery rate of the product,quality of the product,and the extension of distillation tower life were proposed.The direct preparation method of soft magnetic Mn-Zn ferrite precursor was studied by chemical co-precipitation method.The method includes the utilization of raw materials of secondary zinc slag,pickling waste liquid,and scrap iron,and simultaneous leaching and purification of impurity with the absence of Zn,Fe separation.Then,the comprehensive system of Mn-Zn ferrite preparation was carried out.Hence,the hot-dip galvanizing slag is completely recycled.The results show that after purification the secondary zinc slag content of impurity element<0.001 g/L and pickling waste liquor of impurity element<0.001 mol/L.The optimum process parameters for preparing MnZn ferrites are as follows:raw material solution formula is Fe2O3:52%,ZnO:23%,MnO:25%,and the excess coefficients are 1.06,1.09,1.09,respectively.Stirring speed is 500 r/min,feeding speed is 0.75?1 ml·s-1·cm-2,reaction temperature is 45?,aging time is 2 h,NH4HCO3/NH3·H2O is 2,feeding method is adopted,and the solution pH=10,dispersant SDBS dosage is 0.2 g/L,pre-sintering temperature 450?,sintering temperature 1300?.It can directly get the MnZn ferrite precursor powders with yield rates 92%and the particle size less then 2 ?m.The experimental data of ferrite technology confirmed that the magnetic properties of MnZn soft magnetic product are conform to CL10F ferrite industry standards.The low-cost high-performance Mn-Zn ferrite composite soft magnetic material was prepared and studied by using the purified solution.The composite soft magnetic particles were prepared by coating Mn-Zn ferrite on the surface of Fe-based amorphous nanocrystalline particles using a chemical sol-gel method.By adding the low melting point NiPCuSn alloy to bond finemet soft magnetic powder,a soft magnetic block with excellent soft magnetic properties was successfully prepared at low temperature.The secondary zinc slag was used for directly preparing tetrapod nano-ZnO whisker.The tetrapod nano-ZnO whisker was used as a photocatalyst to degrade organic contaminants in water.The photocatalytic degradation ability of tetrapod nano-ZnO whisker under UV light irradiation was investigated.The influence of the initial concentration of methylene blue solution,amount of catalyst,and reaction time on photocatalytic degradation was investigated.The results show that the best dosage of photocatalyst is 2 g/L,at this point after 25 min photocatalytic degradation,the degradation rate of 10 mg/L methylene blue is over 95%.Moreover,the smaller the size of the four needle ZnO whiskers,the higher the catalytic performance is,and the photocatalytic effect of four needle ZnO whiskers is better than that of flake ZnO whiskers. |
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