The recovery of metal oxides from stainless steel dust using C（graphite）, SiFe, and Al as reductants was investigated under various conditions. The apparent distribution ratio of Cr（L Cr ′^m/s ） in the recovered ...The recovery of metal oxides from stainless steel dust using C（graphite）, SiFe, and Al as reductants was investigated under various conditions. The apparent distribution ratio of Cr（L Cr ′^m/s ） in the recovered metal and residual slag phases was defined as the major performance metric. The results show that the recovery ratio of metals increases as the ratio of CaO ：SiO2 by mass in the residual slag increases to 1.17. The residual content of metals in the slag decreases as the Al2O3 content of the slag is increased from approximately 8wt% to 10wt%. The recovery ratio of Cr increases with increasing L Cr ′^ m/s , and a linear relationship between L Cr ′^m/s and the activity coefficient ratio of CrO in the slag and the recovered metal phase is observed. The combination of C and SiFe or Al as the reducing agents reveals that Si is the more effective coreductant.展开更多
To efficiently recycle valuable metals such as chromium and nickel in stainless steel dust, self-reduction ex- periments were carried out to study the reduction mechanism of metal oxides in coal composite stainless st...To efficiently recycle valuable metals such as chromium and nickel in stainless steel dust, self-reduction ex- periments were carried out to study the reduction mechanism of metal oxides in coal composite stainless steel dust hot briquette, which is defined as a CCSB here. Self-reduction of CCSB is proceeded by volatile matter and fixed carbon contained within CCSB. Experiments were performed to study the effects of temperature and carbon to oxygen （C/OCoal） ratio on self reduction of CCSB. At 1400 and 1450℃, volatile matter in coal used for experiment could take the place of about 40℃ of fixed carbon in coal. Under the present experimental conditions, reduction product of chromium appears as FeCr2O2, Cr2O3, Cr7C3 , and [Cr] in turn during reduction. To evaluate the formation of met al nuggets in self reduction process of CCSB, metal nuggets containing chromium and nickel were observed in outside of reduction products under various conditions, and thermodynamic equilibrium calculation was carried out for possi hie products and formation of molten metal by fixed carbon. SEM and EDS analyses were made for metal nugget and slag in reduced product. The results reveal that it is reasonable to achieve the metal nuggets at 1450℃, 0.8 of C/OCoal ratio and 20 min of reduction time. The nugget formation can indicate one innovative process for comprehensive utilization of stainless steel dust.展开更多
The leaching of chromium from stainless steel dust （SSD） is deleterious to the environment. To address this issue, the reduction of SSD briquettes can be employed to effectively extract chromium. The recovery rates ...The leaching of chromium from stainless steel dust （SSD） is deleterious to the environment. To address this issue, the reduction of SSD briquettes can be employed to effectively extract chromium. The recovery rates of iron, chromium, and nickel via ironbath reduction of SSD briquettes were determined using X-ray fluorescence spectroscopy, X-ray diffraction, and scanning electron microscopy measurements. First, the effects of basicity and contents of silicon, iron, CaF2, and carbon on the recovery rates of the three metals were analyzed using the slag amount prediction model, which was originally established from the A1203 balance of corundum crucible erosion behavior. Second, the effect of feeding mode, i.e., whether steel scrap and SSD briquettes were simultaneously added, on the recovery rates was discussed in detail. Third, the iron-bath reduction of SSD briquettes was thermodynamically analyzed. The results indicated that the recovery rates of the three metals are greater than 95% those of using a basicity of 1.5 and 6.0% CaF2, 15% carbon, and 7% ferrosilicon. The recovery rate of chromium increases twofold with the addition of ferrosilicon. The feeding mode of adding briquettes and steel scrap simultaneously is better for recovery of metals and separation of the metal and slag than the feeding mode of adding steel scrap firstly and then briquettes.展开更多
The volatilization of zinc and lead from the stainless steel making dust pellets in the direct recycling procedure was conducted by using a thermo-gravimetric analyzer and a Tamman furnace in the nitrogen atmosphere r...The volatilization of zinc and lead from the stainless steel making dust pellets in the direct recycling procedure was conducted by using a thermo-gravimetric analyzer and a Tamman furnace in the nitrogen atmosphere respectively. The results show that the temperature has a significant effect on the volatilization rates of zinc and lead, and the carbon content in the pellets has no effect on the volatilization process. The volatilization of zinc is controlled by the chemical reaction between zinc oxide and carbon monoxide, while the volatilization of lead is controlled by the evaporation from liquid phase to the atmosphere. The volatilization of zinc and lead mainly happen at about 1 000 ℃ according to non-isothermal experiment.展开更多
The European stainless steel producers generate 20 -30 kg dust per ton of produced stainless steel.The dust formed during various stages of the production process contains valuable metals such as Cr,Ni and Mo.In gener...The European stainless steel producers generate 20 -30 kg dust per ton of produced stainless steel.The dust formed during various stages of the production process contains valuable metals such as Cr,Ni and Mo.In general this dust is considered as a hazardous waste.If not taken care of the dust will be an environmental risk causing potential problems such as leaching of heavy metals into groundwater and pollution of land and air.By applying techniques for recycling the dust the problem is minimized and valuable metals are recovered and re-used as raw material in the steel making process,leading to a significant reduction of the consumption of natural resources to decelerate the climate change and ensure a sustainable development.One of the business segments of Befesa Zinc S.L.U.,a subsidiary company of Abengoa,is the recycling of dusts and other residues containing nickel,chromium and molybdenum from the stainless steel industry.The technologies applied are submerged arc reduction smelting(Befesa Valera S.A.S.,Gravelines,France) and plasma reduction smelting(Befesa ScanDust AB,Landskrona,Sweden).Stainless steel plant dusts,mill scale and other residues are delivered in closed containers and big bags by ship,rail or truck and stored.After a preparation of the residues and charging into the pyrometallurgical furnace,the metal compounds contained in the charge are reduced to metals in the presence of the carbon added.At Befesa ScanDust,the regularly tapped liquid metal is cast in the form of granules via the Granshot^(?) granulation process.The granulated product has many advantages such as excellent preheating properties and fast melting when added to a metallurgical process.The granules size and shape also makes it very suitable to handle with most raw material handling systems.By granulating the so-called alloyed pig iron(API) a high metallic yield is achieved ensuring maximum recovery of metal and less new dust generation compared to a crushed material.The granules are redelivered to the stainless steel producers or sold on the open market.展开更多
The leachability and fractionation of the selected heavy metals （Cr, Cd, Pb and Zn） in the stainless steelmaking plant dusts were studied by the modified HJ/T299-2007 method, the modified TCLP test and a seven-step ...The leachability and fractionation of the selected heavy metals （Cr, Cd, Pb and Zn） in the stainless steelmaking plant dusts were studied by the modified HJ/T299-2007 method, the modified TCLP test and a seven-step sequential extraction procedure. The results show that the stainless steelmaking plant dusts are considered as hazardous materials since at least one of the leachable heavy metals exceeds the corresponding limit levels of State Environmental Protection Administration of China. Pb is the most extractable heavy metals by the sequential extraction procedure, while Cr, Cd and Zn mainly presents in the residual fraction bound to spinel phase and silicates. The mobile heavy metals in the dusts, which present as the species of water soluble, exchangeable species and the species bounded to carbonates and hydroxides, can be estimated as 0.08 1.2% of Cr, 7.6% 31.8% of Cd, 34.1% of Pb, 0.052-0.4% of Zn, respectively.展开更多
基金financially supported by the National Natural Science Foundation of China (No. 51474021)the Fundamental Research Funds for the Central Universities of China (No. FRF-SD-12-009A)
文摘The recovery of metal oxides from stainless steel dust using C（graphite）, SiFe, and Al as reductants was investigated under various conditions. The apparent distribution ratio of Cr（L Cr ′^m/s ） in the recovered metal and residual slag phases was defined as the major performance metric. The results show that the recovery ratio of metals increases as the ratio of CaO ：SiO2 by mass in the residual slag increases to 1.17. The residual content of metals in the slag decreases as the Al2O3 content of the slag is increased from approximately 8wt% to 10wt%. The recovery ratio of Cr increases with increasing L Cr ′^ m/s , and a linear relationship between L Cr ′^m/s and the activity coefficient ratio of CrO in the slag and the recovered metal phase is observed. The combination of C and SiFe or Al as the reducing agents reveals that Si is the more effective coreductant.
基金Item Sponsored by Fundamental Research Funds for the Central Universities of China(N110202001)
文摘To efficiently recycle valuable metals such as chromium and nickel in stainless steel dust, self-reduction ex- periments were carried out to study the reduction mechanism of metal oxides in coal composite stainless steel dust hot briquette, which is defined as a CCSB here. Self-reduction of CCSB is proceeded by volatile matter and fixed carbon contained within CCSB. Experiments were performed to study the effects of temperature and carbon to oxygen （C/OCoal） ratio on self reduction of CCSB. At 1400 and 1450℃, volatile matter in coal used for experiment could take the place of about 40℃ of fixed carbon in coal. Under the present experimental conditions, reduction product of chromium appears as FeCr2O2, Cr2O3, Cr7C3 , and [Cr] in turn during reduction. To evaluate the formation of met al nuggets in self reduction process of CCSB, metal nuggets containing chromium and nickel were observed in outside of reduction products under various conditions, and thermodynamic equilibrium calculation was carried out for possi hie products and formation of molten metal by fixed carbon. SEM and EDS analyses were made for metal nugget and slag in reduced product. The results reveal that it is reasonable to achieve the metal nuggets at 1450℃, 0.8 of C/OCoal ratio and 20 min of reduction time. The nugget formation can indicate one innovative process for comprehensive utilization of stainless steel dust.
基金This research was supported by the National Natural Science Foundation of China （Grant No. 51304053）, Jiangxi University of Science and Technology Doctoral Start-up Fund （No. 3401223181）.
文摘The leaching of chromium from stainless steel dust （SSD） is deleterious to the environment. To address this issue, the reduction of SSD briquettes can be employed to effectively extract chromium. The recovery rates of iron, chromium, and nickel via ironbath reduction of SSD briquettes were determined using X-ray fluorescence spectroscopy, X-ray diffraction, and scanning electron microscopy measurements. First, the effects of basicity and contents of silicon, iron, CaF2, and carbon on the recovery rates of the three metals were analyzed using the slag amount prediction model, which was originally established from the A1203 balance of corundum crucible erosion behavior. Second, the effect of feeding mode, i.e., whether steel scrap and SSD briquettes were simultaneously added, on the recovery rates was discussed in detail. Third, the iron-bath reduction of SSD briquettes was thermodynamically analyzed. The results indicated that the recovery rates of the three metals are greater than 95% those of using a basicity of 1.5 and 6.0% CaF2, 15% carbon, and 7% ferrosilicon. The recovery rate of chromium increases twofold with the addition of ferrosilicon. The feeding mode of adding briquettes and steel scrap simultaneously is better for recovery of metals and separation of the metal and slag than the feeding mode of adding steel scrap firstly and then briquettes.
文摘The volatilization of zinc and lead from the stainless steel making dust pellets in the direct recycling procedure was conducted by using a thermo-gravimetric analyzer and a Tamman furnace in the nitrogen atmosphere respectively. The results show that the temperature has a significant effect on the volatilization rates of zinc and lead, and the carbon content in the pellets has no effect on the volatilization process. The volatilization of zinc is controlled by the chemical reaction between zinc oxide and carbon monoxide, while the volatilization of lead is controlled by the evaporation from liquid phase to the atmosphere. The volatilization of zinc and lead mainly happen at about 1 000 ℃ according to non-isothermal experiment.
文摘The European stainless steel producers generate 20 -30 kg dust per ton of produced stainless steel.The dust formed during various stages of the production process contains valuable metals such as Cr,Ni and Mo.In general this dust is considered as a hazardous waste.If not taken care of the dust will be an environmental risk causing potential problems such as leaching of heavy metals into groundwater and pollution of land and air.By applying techniques for recycling the dust the problem is minimized and valuable metals are recovered and re-used as raw material in the steel making process,leading to a significant reduction of the consumption of natural resources to decelerate the climate change and ensure a sustainable development.One of the business segments of Befesa Zinc S.L.U.,a subsidiary company of Abengoa,is the recycling of dusts and other residues containing nickel,chromium and molybdenum from the stainless steel industry.The technologies applied are submerged arc reduction smelting(Befesa Valera S.A.S.,Gravelines,France) and plasma reduction smelting(Befesa ScanDust AB,Landskrona,Sweden).Stainless steel plant dusts,mill scale and other residues are delivered in closed containers and big bags by ship,rail or truck and stored.After a preparation of the residues and charging into the pyrometallurgical furnace,the metal compounds contained in the charge are reduced to metals in the presence of the carbon added.At Befesa ScanDust,the regularly tapped liquid metal is cast in the form of granules via the Granshot^(?) granulation process.The granulated product has many advantages such as excellent preheating properties and fast melting when added to a metallurgical process.The granules size and shape also makes it very suitable to handle with most raw material handling systems.By granulating the so-called alloyed pig iron(API) a high metallic yield is achieved ensuring maximum recovery of metal and less new dust generation compared to a crushed material.The granules are redelivered to the stainless steel producers or sold on the open market.
基金supported by the National Natural Science Foundation of China(No.50804037)
文摘The leachability and fractionation of the selected heavy metals （Cr, Cd, Pb and Zn） in the stainless steelmaking plant dusts were studied by the modified HJ/T299-2007 method, the modified TCLP test and a seven-step sequential extraction procedure. The results show that the stainless steelmaking plant dusts are considered as hazardous materials since at least one of the leachable heavy metals exceeds the corresponding limit levels of State Environmental Protection Administration of China. Pb is the most extractable heavy metals by the sequential extraction procedure, while Cr, Cd and Zn mainly presents in the residual fraction bound to spinel phase and silicates. The mobile heavy metals in the dusts, which present as the species of water soluble, exchangeable species and the species bounded to carbonates and hydroxides, can be estimated as 0.08 1.2% of Cr, 7.6% 31.8% of Cd, 34.1% of Pb, 0.052-0.4% of Zn, respectively.
