| The main components of Blast Furnace (BF) dust are iron and carbon, at the same time it includes a few elements as silicon, aluminum, calcium, magnesium and so on. Also a part of blast furnace dusts contain harmful elements, such as lead, zinc, arsenic, etc. Generally, its property and content are in correlation with charge composition. In 1976, American Environmental Protection Association (EPA) legislated the law that the iron and steel plant dusts contained lead and zinc were listed K061 matters (virulent solid waste) and requested to recycle or deactivate lead, zinc and other harmful elements. Otherwise, they have to seal before piled at assigning location. Therefore, all countries extremely emphasized BFdust processing and comprehensive utilization, hoped to develop a practical technology, which can economically recycle the valuable metal resources and not pollute to environment.At present, our country approximately produces BFdust 10 million tons every year, gas ash and gas slimes respectively accounts for about 50%. Most domestic plants have not effectively used BF gas slimes, which generally used by returning sintering plant as mixture of sinters in the past. But the gas slimes granularity is very thin, much smaller than the fine ore, the permeability of bed of material will be greatly decreased, thus will affect the process efficiency, when adding the gas slimes to materials of sinter. The easy volatilization elements as Zn, Pb in gas slimes will recycle and concentrate in BF, resulting in the ZnO rising in gas, upper of BF heeling, gas pipe blocking, therefore BF cannot normally operate. Minority plants obtain secondary dusts containing Zn, Pb and charge containing Fe by separation or hydrometallurgy process. But the technological process is long and the process scale is small with extremely low recovery rate. The thesis adopts carbon-containing pellets roasting reduction method to obtain high grade zinc oxide powders and semi-metallic pellets, on the basis of Panzhihua steel blast furnace gas slimes characteristics containing higher iron, carbon and zinc.Firstly, physical-chemical property of BF gas slimes was analyzed in the thesis, then the reducing thermodynamics were calculated out, and the kinetics of BF gas slimes was studied. The research has shown that BF gas slimes is easyly reduced at high temperature, which proved that the reduction of BF gas slimes by roasting reduction method is possible in theory. In order to meet the experimental condition of carbon-containing pellets, the palletizing-property of BF slimes was researched. Experimental results shown that BF gas slimes of Panzhihua steel are very fine, the average size is 49.17μm, the size smaller than 10μm is above 50% among particles, which is very beneficial to be palletized.Based on the research of thermodynamics and kinetics, the efficient utilization of BF gas slimes research was carried in the laboratory. Through studying the effects of reduction temperature, reduction time, granularity of pellets on the process, the processing parameters were determined. The experimental results have shown that reduction effect is very satisfactory using carbon in the gas slimes as reductant. By analyzing, the better parameters of roasting reduction method are shown as follows: reduction temperature 1150℃, reduction time 45 min. The treated pellets are semi-metallic pellets, total ferrum content in the treated pellets is about 52%, the highest content of TFe will reach up to 65.2%; metal ferrum content is about 51%, the highest value is 64.73%; the compression strength of single pellet is about 2 kN; ZnO content of by-product zinc oxide powders is about 95%, the highest value is 97.97%. Zinc oxide content of by-product zinc oxide powders is little lower than that we expected, because of the limit of oxidizing-room in laboratory. The industrial process could improve the grade of zinc oxide powders through improving the oxidizability of oxidizing-room.Based on the success of laboratory research, the exploratory semi-industrial research was carried out,the purpose is to approve the feasibility of the equipment and heating-way which designed for the experiment. The effect of temperature, time on reduction of the BF slimes had been studied under the semi-industrial scale condition. Research results indicated that the equipment and heating-way which designed for the experiment was working well. By analyzing, the better parameters of roasting reduction method under semi-industrial scale condition are shown as follows: reduction temperature 1100℃~1150℃, processing time 300 min. The treated pellets are semi-metallic pellets, total ferrum content(TFe) in the treated pellets is about 55%; metal ratio is about 80%; ZnO content in by-product zinc oxide powders is higher than 90%.In order to further realize efficient utilization of BF gas slimes, the laboratory research adding the converter sludge to the BF gas slimes has carried on. The effect of carbon-oxygen ratio (C/O), temperature, time on reduction of the BF slimes had been studied under the lab condition, the processing parameters were determined. The experimental results shown that reduction effect is very satisfactory using redundant carbon in the gas slimes as reductant of converter sludge.By analyzing, the better parameters of roasting reduction method are shown as follows: reduction temperature 1200℃, reduction time 60 min. The treated pellets are semi-metallic pellets, total ferrum content in the treated pellets is about 58%, the highest content of TFe will reach up to 59.4%; metal ferrum content is about 55%, the highest value is 59.33%; metal ratio is about 95%, the highest value is 99.89%; ZnO content in by-product zinc oxide powders is about 94.5%. The purpose for BF gas slimes efficient utilization was further achieved. |
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