To study the combustion behavior of municipal solid waste(MSW)in blast furnace,the combustion process within the raceway was simulated using computational fluid dynamics.Based on the parameters of an actual blast furn...To study the combustion behavior of municipal solid waste(MSW)in blast furnace,the combustion process within the raceway was simulated using computational fluid dynamics.Based on the parameters of an actual blast furnace,a three-dimensional model including coal lance,blowpipe,tuyere,and raceway was established.The model was then used to compare the combustion characteristics of pulverized coal and MSW in the raceway and to investigate the effects of blast temperature and particle size on the combustion characteristics of MSW in the raceway.The results showed that MSW combusted more rapidly,achieving a maximum temperature of 3839 K in the raceway,comparing to 2974 K during pulverized coal injection.However,the average temperature during MSW injection was 1790 K,which was 73 K lower than that of pulverized coal injection.The maximum velocity during MSW injection was 120 m/s,lower than 188 m/s obtained during pulverized coal injection.MSW could be completely burned out in the middle of the raceway,while the burnout of pulverized coal at this position was only 50%.The combustion effect of MSW makes no difference when the blast temperature increased from 1273 to 1673 K,due to its excellent combustion characteristic.When the MSW particle size was increased from 0.074 to 2 mm,the burnout was 75%,which was still higher than that of pulverized coal injection with a particle size of 0.074 mm.However,injecting larger-sized fuel might increase the risk of tuyere wear.To ensure stable furnace conditions and great combustion,a blast temperature of 1473 K and a MSW particle size of about 1 mm will be better.展开更多
Pursuing green,low-carbon ironmaking technology primarily aims to reduce fuel ratios,especially coke ratios.Simultaneously,the reduction in coke ratios causes the coke layer in the blast furnace(BF)to become thinner,d...Pursuing green,low-carbon ironmaking technology primarily aims to reduce fuel ratios,especially coke ratios.Simultaneously,the reduction in coke ratios causes the coke layer in the blast furnace(BF)to become thinner,deteriorating the gas and liquid permeability of the burden column.This exacerbates coke degradation,significantly impacting the smelting process and increasing the demand for high-quality coke.To investigate the existence state of coke in the hearth,a 2500 m3 BF in China was taken as the research object,and three sets of samples at different heights of the hearth were obtained during planned outage.The results indicate that coke undergoes a significant degradation upon reaching the hearth.The proportion of coke particles smaller than 50 mm ranges from 81.22%to 89.50%.The proportion of coke particles larger than 20 mm decreases as the distance from the centerline of the tuyere increases,while the proportion of particles smaller than 10 mm increases with this distance.Additionally,the closer the bottom of the furnace is,the smaller the coke particle size becomes.The composition of slag filling the coke pores is similar to that of the final slag in the blast furnace,and the graphitization of coke is comparable to that of the final slag.The graphitization of coke starts from the surface of coke and leads to the formation of coke fines,and the graphitization degree of−74μm coke fines is the highest.The temperature has an effect on the reaction rate of coke solution loss,and the higher the temperature is,the faster the reaction rate is.展开更多
Iron nugget and boron-rich slag can be obtained in a short time through high-temperature reduction of boron- bearing iron concentrate by carbonaceous material, both of which are agglomerated together as a carbon compo...Iron nugget and boron-rich slag can be obtained in a short time through high-temperature reduction of boron- bearing iron concentrate by carbonaceous material, both of which are agglomerated together as a carbon composite pellet. This is a novel flow sheet for the comprehensive utilization of boron-bearing iron concentrate to produce a new kind of man-made boron ore. The effect of reducing agent species （i.e., carbon species） on the reduction and melting process of the composite pellet was investigated at a laboratory scale in the present work. The results show that, the reduction rate of the composite pellet increases from bituminite, anthracite, to coke at temperatures ranging from 950 to 1300~C. Reduction temperature has an important effect on the microstructure of reduced pellets. Carbon species also affects the behavior of reduced metallic iron particles. The anthracite-bearing composite pellet melts faster than the bituminite- bearing composite pellet, and the coke-bearing composite pellet cannot melt due to the high fusion point of coke ash. With anthracite as the reducing agent, the recovery rates of iron and boron are 96.5% and 95.7%, respectively. This work can help us get a further understanding of the new process mechanism.展开更多
The high-temperature tube furnace was applied to simulate the rotary hearth furnace （RHF） for the direct reduction of zinc-bearing dusts from steel plants. The removal mechanism of Zn, Pb and alkalis from cold bonde...The high-temperature tube furnace was applied to simulate the rotary hearth furnace （RHF） for the direct reduction of zinc-bearing dusts from steel plants. The removal mechanism of Zn, Pb and alkalis from cold bonded briquettes made by mixing metallurgical wastes, such as dust from bag house filter, OG sludge, fine converter ash and dust from the third electric field precipitator of the sinter strand, in various proportions was investigated. More than 70% of metallization rate, more than 95% of zinc removal rate, 80% of lead removal, as well as more than 80M of K and Na removal rates were achieved for the briquettes kept at 1473-1603 K for 15 min during the direct reduction process respectively. The soot generated in the direct reduction process was studied by chromatography, X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results suggested that the main phases of the soot were ZnO, KC1, NaC1 and 4ZnO · ZnC12 · 5H20. Furthermore, the content of Zn reached 64.2 %, which could be used as secondary resources for zinc making. It was concluded that KC1 and NaC1 in secondary dust resulted from the volatilization from the briquettes, whilst ZnO and PbO were produced by the oxidation of Zn or lead vapour from briquettes by direct reduction.展开更多
The high-value utilization of low-rank coal would allow for expanding energy sources,improving energy efficiencies,and alleviating environmental issues.In order to use low-rank coal effectively,the hypercoals(HPCs)wer...The high-value utilization of low-rank coal would allow for expanding energy sources,improving energy efficiencies,and alleviating environmental issues.In order to use low-rank coal effectively,the hypercoals(HPCs)were co-extracted from two types of low-rank coal and biomass via N-methyl-2-purrolidinone(NMP)under mild conditions.The structures of the HPCs and residues were characterized by proximate and ultimate analysis,Raman spectra,and Fourier transform infrared(FT-IR)spectra.The carbon structure changes within the raw coals and HPCs were discussed.The individual thermal dissolution of Xibu(XB)coal,Guandi(GD)coal,and the biomass demonstrated that the biomass provided the lowest thermal dissolution yield Y1 and the highest thermal soluble yield Y2 at 280℃,and the ash content of three HPCs decreased as the extraction temperature rose.Co-thermal extractions in NMP at various coal/biomass mass ratios were performed,demonstrating a positive synergic effect for Y2 in the whole coal/biomass mass ratios.The maximum value of Y2 was 52.25wt% for XB coal obtained with a XB coal/biomass of 50wt% biomass.The maximum value of Y2 was 50.77wt% for GD coal obtained with a GD coal/biomass of 1:4.The difference for the optimal coal/biomass mass ratios between XB and GD coals could be attributed to the different co-extraction mechanisms for this two type coals.展开更多
Basic physicochemical properties of the dust from Laiwu Iron and Steel Co. Ltd. were studied. It is found that C, Zn, K, Na, etc. exist in the fabric filter dust, off gas （OG） sludge, fine ash in converter, and elec...Basic physicochemical properties of the dust from Laiwu Iron and Steel Co. Ltd. were studied. It is found that C, Zn, K, Na, etc. exist in the fabric filter dust, off gas （OG） sludge, fine ash in converter, and electrical field dust in sinter. Among these, OG sludge gives the finest particle, more than 90% of which is less than 2.51 mm. The dust can lead to a serious negative influence on the production of sintering and blast furnaces （BF） if it is recycled in sintering. The briquette and reduction experimental results showed that the qualified strength could be obtained in the case of 8wt% molasses or 4wt% QT-10 added as binders. Also, more than 75% of metallization ratio, more than 95% of dezincing ratio, as well as more than 80% of K and Na removal rates were achieved for the briquettes kept at 1250℃ for 15 min during the direct reduction process. SEM observation indicated that the rates of indirect reduction and carbonization became dominating when the bri-quettes were kept at 1250℃ for 6 min.展开更多
Four types of coals, KL, XB, ZS and GD with different coal ranks, were dissolved with the organic solvent N-methyl-2- pyrrolidone at 350 ℃ and around 3.0 MPa pressure to obtain thermal soluble constituents （TSCs）. ...Four types of coals, KL, XB, ZS and GD with different coal ranks, were dissolved with the organic solvent N-methyl-2- pyrrolidone at 350 ℃ and around 3.0 MPa pressure to obtain thermal soluble constituents （TSCs）. The yield, component and maceral group were investigated as well as their coking properties, including caking index and thermoplasticity. The results indicated that the yields of the four coals were of the following order： KL 〉 XB 〉 ZS 〉 GD. Based on the yield and the vitrinite content, coals were ranked from high to low. The ash contents of TSCs were significantly less than that of raw coals, and the TSCs contain more light components, leading to an increase in volatile matter. The patterns of Fourier transform infrared spectroscopy indicated that carbonyl was enriched in TSCs. Regarding the maceral group, TSCs were mainly composed of vitrinite which is the main reactive material and converts into binder phase in cokemaking process. Higher caking index values and fluidity were obtained in TSCs compared with the raw coals. The coking experiments with different amounts of TSCs addition were carried out. The results demonstrated that the proper TSCs addition could enhance the coke strength due to its high caking index and good fluidity.展开更多
CaO-containing carbon pellets(CCCP)were successfully prepared from well-mixed coking coal(CC)and calcium oxide(CaO)and roasted at different pyrolysis temperatures.The effects of temperature,pore distribution,and carbo...CaO-containing carbon pellets(CCCP)were successfully prepared from well-mixed coking coal(CC)and calcium oxide(CaO)and roasted at different pyrolysis temperatures.The effects of temperature,pore distribution,and carbon structure on the compressive strength of CCCP was investigated in a pyrolysis furnace(350-750℃).The results showed that as the roasting temperature increased,the compressive strength also increased and furthermore,structural defects and imperfections in the carbon crystallites were gradually eliminated to form more organized char structures,thus forming high-ordered CC.Notably,the CCCP preheated at 750℃exhibited the highest compressive strength.A positive relationship between the compressive strength and pore-size homogeneity was established.A linear relationship between the com-pressive strength of the CCCP and the average stack height of CC was observed.Additionally,a four-stage caking mechanism was developed.展开更多
The microstructure of coke has an important influence on its thermal properties.The solution loss reactions of coke in CO2 and H2O atmospheres were investigated by in situ observation.The results showed that the isotr...The microstructure of coke has an important influence on its thermal properties.The solution loss reactions of coke in CO2 and H2O atmospheres were investigated by in situ observation.The results showed that the isotropic components had a more vigorous reaction than the anisotropic components,and the solution loss reaction of the fine-grained mosaic structure was faster than that of the coarse-grained mosaic structure under the CO2 and H2O atmospheres.The coarse-grained mosaic structure and the flowing structure had a relatively higher anti-erosion ability in the CO2 atmosphere than in the H2O atmosphere,and there was no distinct difference in the solution loss of the isotropic structure under the CO2 and H2O atmospheres.The electron probe microanalysis showed that the Al-Si-Fe compounds in the carbon matrix had positive influence on the solution loss reaction of the anisotropic structure.The iron compounds were able to destroy the pore walls of coke and accelerate the solution loss rate of coke.展开更多
Direct reduction of dust composite pellets containing zinc and iron was examined by simulating the conditions of actual production process of a rotary hearth furnace （RHF） in laboratory. A mathematical model was con...Direct reduction of dust composite pellets containing zinc and iron was examined by simulating the conditions of actual production process of a rotary hearth furnace （RHF） in laboratory. A mathematical model was constructed to study the reduction kinetics of iron oxides and ZnO in the dust composite pellets. It was validated by comparing the calculated values with experimental results. The effects of furnace temperature, pellet radius, and pellet porosity on the reduction were investigated by the model. It is shown that furnace temperature has obvious influence on both of the reduction of iron oxides and ZnO, but the influence of pellet radius and porosity is much smaller. Model calculations suggest that both of the reduction of iron oxides and ZnO are under mixed control with interface reactions and Boudouard reaction in the early stage, but only with interface reactions in the later stage.展开更多
The softening and melting behavior of sinter, pellet and mixed burden was researched through high tem- perature reaction tests under load simulating traditional blast furnace （T-BF） and oxygen blast furnace （OBF） ...The softening and melting behavior of sinter, pellet and mixed burden was researched through high tem- perature reaction tests under load simulating traditional blast furnace （T-BF） and oxygen blast furnace （OBF） condi- tions. The results indicated that compared with T-BF, the softening zone of sinter and pellet became wide, but the melting zone became narrow in OBF. The permeabilities of both sinter and pellet were improved in OBF. Under the condition of OBF, the temperature of softening zone of mixed burden was increased by 63 K, but the temperature of melting zone was decreased by 76 K. Therefore, the permeability of material layer was significantly improved. This was mainly caused by the change of the melting behavior of pellet. In addition, the quality Of dripping iron in OBF was much better than that of T-BF.展开更多
Ludwigite is a kind of complex iron ore containing boron, iron, and magnesium, and it is the most promising boron resource in China. Selective reduction of iron oxide is the key step for the comprehensive utilization ...Ludwigite is a kind of complex iron ore containing boron, iron, and magnesium, and it is the most promising boron resource in China. Selective reduction of iron oxide is the key step for the comprehensive utilization of ludwigite. In the present work, the reduction mechanism of ludwigite was investigated. The thermogravimetry and differential scanning calorimetry analysis and isothermal reduction of ludwigite/coal composite pellet were performed. Ludwigite yielded a lower reduction starting temperature and a higher final reduction degree compared with the traditional iron concentrates. Higher specific surface area and more fine cracks might be the main reasons for the better reducibility of ludwigite. Reducing temperature highly affected the reaction fraction and microstructure of the reduced pellets, which are closely related to the separation degree of boron and iron. Increasing reducing temperature benefited the boron and iron magnetic separation. Optimum magnetic separation results could be obtained when the pellet was reduced at 1300°C. The separated boron-rich non-magnetic concentrate presented poor crystalline structure, and its extraction efficiency for boron reached 64.3%. The obtained experimental results can provide reference for the determination of the comprehensive utilization flow sheet of ludwigite.展开更多
Blast furnace ironmaking process is the most mature and highly effective process for producing liquid iron.Blast furnace is a gas-solid and gas-solid-liquid countercurrent reactor,and maintaining gas permeability is t...Blast furnace ironmaking process is the most mature and highly effective process for producing liquid iron.Blast furnace is a gas-solid and gas-solid-liquid countercurrent reactor,and maintaining gas permeability is the precondition of smooth production.Therefore,improving the gas permeability throughout the blast furnace remains a hot issue which is concerned by many metallurgical scholars.According to the research results of many scholars,the dominant factors influencing the gas permeability of different locations in the blast furnace(locations are distinguished according to the morphology change of the burdens)were reviewed.And the strategies for improving the gas permeability of different locations in the blast furnace were summarized based on these dominant influencing factors,such as suppressing the low-temperature reduction degradation of sinter in the lump zone,improving the indirect reduction degree and suppressing the interaction between different burdens.It is hoped to provide both theoretical and practical values for guiding the blast furnace so as to improve smooth operation and smelting efficiency.展开更多
The softening-melting characteristics of ferrous burden play a crucial role in the thickness and position of the cohesive zone.The influence of the basicity and experimental atmosphere on the softening-melting behavio...The softening-melting characteristics of ferrous burden play a crucial role in the thickness and position of the cohesive zone.The influence of the basicity and experimental atmosphere on the softening-melting behavior of primary slag under slag-coke interaction was investigated using in situ visualization method.The mechanism was analyzed using the FactSage software,X-ray diffraction,and electron probe microanalysis.The softening and melting temperatures of the samples increased with increasing basicity under different atmospheres.The difference between softening and melting temperatures is smaller in a H_(2) atmosphere than in a CO atmosphere;in H_(2) atmosphere,the range of softening zone in the cohesive zone was significantly thinner.The formed low-melting-point FeO-bearing phases decrease when H_(2) was used as the reducing agent.In addition,according to FactSage calculations,the high content of metallic iron reduced in the H_(2) atmosphere raised the softening temperature of the primary slag.It also narrowed and moved downward the cohesive zone due to an increase in softening and melting temperatures.Meanwhile,the increase in basicity promoted the decrease in liquid ratio and improved the permeability of cohesive zone.展开更多
To support the development of technology to utilize low-grade Ti-Nb-bearing Fe concentrate, the reduction of the concentrate by coal was systematically investigated in the present paper. A liquid phase formed when the...To support the development of technology to utilize low-grade Ti-Nb-bearing Fe concentrate, the reduction of the concentrate by coal was systematically investigated in the present paper. A liquid phase formed when the Ti Nb-bearing Fe concentrate/coal composite pel- let was reduced at temperatures greater than 1100℃. The addition of CaCO3 improved the reduction rate when the slag basicity was less than 1.0 and inhibited the formation of the liquid phase. Mechanical milling obviously increased the metallization degree compared with that of the standard pellet when reduced under the same conditions. Evolution of the mineral phase composition and microstructure of the reduced Ti-Nb-bearing Fe concentrate/coal composite pellet at 1100~C were analyzed by X-ray diffraction and scanning electron microsco- py-energy-dispersive spectroscopy. The volume shrinkage value of the reduced Ti-Nb-bearing Fe concentrate/coal composite pellet with a basicity of 1.0 was approximately 35.2% when the pellet was reduced at 1100℃ for 20 min, which enhanced the external heat transfer to the lower layers when reduced in a practical rotary hearth furnace. The present work provides key parameters and mechanism understanding for the development of carbothermic reduction technology of a Ti-Nb-bearing Fe concentrate incorporated in a pyrometallurgical utilization flow sheet.展开更多
A novel process for boron enrichment and extraction from ludwigite based on iron nugget technology was proposed. The key steps of this novel process, which include boron and iron separation, crystallization of boron-r...A novel process for boron enrichment and extraction from ludwigite based on iron nugget technology was proposed. The key steps of this novel process, which include boron and iron separation, crystallization of boron-rich slag, and elucidation of the boron extraction be- havior of boron-rich slag by acid leaching, were performed at the laboratory. The results indicated that 95.7% of the total boron could be en- riched into the slag phase, thereby forming a boron-rich slag during the iron and slag melting separation process. Suanite and kotoite were observed to be the boron-containing crystalline phases, and the boron extraction properties of the boron-rich slag depended on the amounts and grain sizes of these minerals. When the boron-rich slag was slowly cooled to 1100℃, the slag crystallized well and the efficiency of ex- traction of boron （EEB） of the slag was the highest observed in the present study. The boron extraction property of the slow-cooled bo- ron-rich slag obtained in this study was much better than that of szaibelyite ore under the conditions of 80% of theoretical sulfuric acid amount, leaching time of 30 min, leaching temperature of 40℃ ,and liquid-to-solid ratio of 8 mL/g.展开更多
Aiming at the current characteristics of blast furnace （BF） process, carbon saving potential of blast furnace was investigated from the perspective of the relationship between degree of direct reduction and carbon c...Aiming at the current characteristics of blast furnace （BF） process, carbon saving potential of blast furnace was investigated from the perspective of the relationship between degree of direct reduction and carbon consumption. A new relationship chart between carbon consumption and degree of direct reduction, which can reflect more real situation of blast furnace operation, was established. Further- more, the carbon saving potential of hydrogen-rich oxygen blast furnace （OBF） process was ana- lyzed. Then, the policy implications based on this relationship chart established were suggested. On this basis, the method of improving the carbon saving potential of blast furnace was recycling the top gas with removal of CO2 and H2O or increasing hydrogen in BF gas and full oxygen blast. The results show that the carbon saving potential in traditional blast furnace （TBF） is only 38 56 kg · t ^-1 while that in OBF is 138 kg · t ^-1. Theoretically, the lowest carbon consumpt!on of OBF is 261 kg · t ^-1 and the corresponding degree of direct reduction is 0.04. In addition, the theoretical lowest carbon consumption of hydrogen-rich OBF is 257 kg · t ^-1. The modeling analysis can be used to estimate the carbon savings potential in new ironmaking process and its related CO2 emissions.展开更多
Realizing the boron and iron separation through selective reduction and melting separation of boron-bearing iron con- centrate is of great significance for the utilization of crude ludwigite. The reduction and melting...Realizing the boron and iron separation through selective reduction and melting separation of boron-bearing iron con- centrate is of great significance for the utilization of crude ludwigite. The reduction and melting separation mechanism of boron-bearing iron concentrate/coal composite pellet was systematically investigated. The reduction and melting separation test of small size pellet was performed to reveal the evolution of slag and iron in the melting separation process. The isothermal reduction experiment showed the relationship between reduction stage and melting separation stage, and the step reduction and melting separation was perfectly achieved. Coal particles existed through the reduction and melting separation process and finally formed brown residue around the separated product. The pellet could not realize melting separation when the B2O3 content in the concentrate was lower than 6.00 wt%.展开更多
The reduction behavior of pellet was researched through the programming apparatus under simulated con- ditions of oxygen blast furnace （OBF） and traditional blast furnace （T-BF）. The results indicated that compare...The reduction behavior of pellet was researched through the programming apparatus under simulated con- ditions of oxygen blast furnace （OBF） and traditional blast furnace （T-BF）. The results indicated that compared with traditional blast furnace, the reduction starting temperature of pellet decreased by 60 ℃ under oxygen blast furnace condition. The reduction degree of pellet could almost reach 100% under oxygen blast furnace condition when the temperature reached 1100 ℃, whereas it was only 82.49% in traditional blast furnace. The content of carbon in pel- let of oxygen blast furnace was about 5 times more than that of traditional blast furnace. In addition, the microstruc- ture at the periphery and core of pellets after reaction was characterized by means of SEM and EDS.展开更多
基金supported by the National Natural Science Foundation of China(Nos.51804024 and 52474342)the Fundamental Research Funds for the Central Universities(No.FRF-IC-20-09)the State Key Laboratory of Advanced Metallurgy of University of Science and Technology Beijing(No.41621002).
文摘To study the combustion behavior of municipal solid waste(MSW)in blast furnace,the combustion process within the raceway was simulated using computational fluid dynamics.Based on the parameters of an actual blast furnace,a three-dimensional model including coal lance,blowpipe,tuyere,and raceway was established.The model was then used to compare the combustion characteristics of pulverized coal and MSW in the raceway and to investigate the effects of blast temperature and particle size on the combustion characteristics of MSW in the raceway.The results showed that MSW combusted more rapidly,achieving a maximum temperature of 3839 K in the raceway,comparing to 2974 K during pulverized coal injection.However,the average temperature during MSW injection was 1790 K,which was 73 K lower than that of pulverized coal injection.The maximum velocity during MSW injection was 120 m/s,lower than 188 m/s obtained during pulverized coal injection.MSW could be completely burned out in the middle of the raceway,while the burnout of pulverized coal at this position was only 50%.The combustion effect of MSW makes no difference when the blast temperature increased from 1273 to 1673 K,due to its excellent combustion characteristic.When the MSW particle size was increased from 0.074 to 2 mm,the burnout was 75%,which was still higher than that of pulverized coal injection with a particle size of 0.074 mm.However,injecting larger-sized fuel might increase the risk of tuyere wear.To ensure stable furnace conditions and great combustion,a blast temperature of 1473 K and a MSW particle size of about 1 mm will be better.
基金supported by the National Natural Science Foundation of China(Grant No.U1960205)China Baowu Low Carbon Metallurgy Innovation Foundation(Grant Nos.BWLCF202101 and BWLCF202104)China Minmetals Science and Technology Special Plan Foundation(Grant No.2020ZXA01).
文摘Pursuing green,low-carbon ironmaking technology primarily aims to reduce fuel ratios,especially coke ratios.Simultaneously,the reduction in coke ratios causes the coke layer in the blast furnace(BF)to become thinner,deteriorating the gas and liquid permeability of the burden column.This exacerbates coke degradation,significantly impacting the smelting process and increasing the demand for high-quality coke.To investigate the existence state of coke in the hearth,a 2500 m3 BF in China was taken as the research object,and three sets of samples at different heights of the hearth were obtained during planned outage.The results indicate that coke undergoes a significant degradation upon reaching the hearth.The proportion of coke particles smaller than 50 mm ranges from 81.22%to 89.50%.The proportion of coke particles larger than 20 mm decreases as the distance from the centerline of the tuyere increases,while the proportion of particles smaller than 10 mm increases with this distance.Additionally,the closer the bottom of the furnace is,the smaller the coke particle size becomes.The composition of slag filling the coke pores is similar to that of the final slag in the blast furnace,and the graphitization of coke is comparable to that of the final slag.The graphitization of coke starts from the surface of coke and leads to the formation of coke fines,and the graphitization degree of−74μm coke fines is the highest.The temperature has an effect on the reaction rate of coke solution loss,and the higher the temperature is,the faster the reaction rate is.
基金supported by the National Key R&D Program of China (No. 2019YFC1905703)Provincial Science and Technology Plan Projects in Guangdong Province, China (No. GDKJ2020002)。
基金support by the National Natural Science Foundation of China(No.51274033)
文摘Iron nugget and boron-rich slag can be obtained in a short time through high-temperature reduction of boron- bearing iron concentrate by carbonaceous material, both of which are agglomerated together as a carbon composite pellet. This is a novel flow sheet for the comprehensive utilization of boron-bearing iron concentrate to produce a new kind of man-made boron ore. The effect of reducing agent species （i.e., carbon species） on the reduction and melting process of the composite pellet was investigated at a laboratory scale in the present work. The results show that, the reduction rate of the composite pellet increases from bituminite, anthracite, to coke at temperatures ranging from 950 to 1300~C. Reduction temperature has an important effect on the microstructure of reduced pellets. Carbon species also affects the behavior of reduced metallic iron particles. The anthracite-bearing composite pellet melts faster than the bituminite- bearing composite pellet, and the coke-bearing composite pellet cannot melt due to the high fusion point of coke ash. With anthracite as the reducing agent, the recovery rates of iron and boron are 96.5% and 95.7%, respectively. This work can help us get a further understanding of the new process mechanism.
基金Item Sponsored by China Postdoctoral Science Foundation(2012M510320)Demonstration Project about Recycling Economy in2007of National Development and Reform Commission of China([2007]3194)
文摘The high-temperature tube furnace was applied to simulate the rotary hearth furnace （RHF） for the direct reduction of zinc-bearing dusts from steel plants. The removal mechanism of Zn, Pb and alkalis from cold bonded briquettes made by mixing metallurgical wastes, such as dust from bag house filter, OG sludge, fine converter ash and dust from the third electric field precipitator of the sinter strand, in various proportions was investigated. More than 70% of metallization rate, more than 95% of zinc removal rate, 80% of lead removal, as well as more than 80M of K and Na removal rates were achieved for the briquettes kept at 1473-1603 K for 15 min during the direct reduction process respectively. The soot generated in the direct reduction process was studied by chromatography, X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results suggested that the main phases of the soot were ZnO, KC1, NaC1 and 4ZnO · ZnC12 · 5H20. Furthermore, the content of Zn reached 64.2 %, which could be used as secondary resources for zinc making. It was concluded that KC1 and NaC1 in secondary dust resulted from the volatilization from the briquettes, whilst ZnO and PbO were produced by the oxidation of Zn or lead vapour from briquettes by direct reduction.
基金financially supported by the National Natural Science Foundation of China (No. 51574023)
文摘The high-value utilization of low-rank coal would allow for expanding energy sources,improving energy efficiencies,and alleviating environmental issues.In order to use low-rank coal effectively,the hypercoals(HPCs)were co-extracted from two types of low-rank coal and biomass via N-methyl-2-purrolidinone(NMP)under mild conditions.The structures of the HPCs and residues were characterized by proximate and ultimate analysis,Raman spectra,and Fourier transform infrared(FT-IR)spectra.The carbon structure changes within the raw coals and HPCs were discussed.The individual thermal dissolution of Xibu(XB)coal,Guandi(GD)coal,and the biomass demonstrated that the biomass provided the lowest thermal dissolution yield Y1 and the highest thermal soluble yield Y2 at 280℃,and the ash content of three HPCs decreased as the extraction temperature rose.Co-thermal extractions in NMP at various coal/biomass mass ratios were performed,demonstrating a positive synergic effect for Y2 in the whole coal/biomass mass ratios.The maximum value of Y2 was 52.25wt% for XB coal obtained with a XB coal/biomass of 50wt% biomass.The maximum value of Y2 was 50.77wt% for GD coal obtained with a GD coal/biomass of 1:4.The difference for the optimal coal/biomass mass ratios between XB and GD coals could be attributed to the different co-extraction mechanisms for this two type coals.
文摘Basic physicochemical properties of the dust from Laiwu Iron and Steel Co. Ltd. were studied. It is found that C, Zn, K, Na, etc. exist in the fabric filter dust, off gas （OG） sludge, fine ash in converter, and electrical field dust in sinter. Among these, OG sludge gives the finest particle, more than 90% of which is less than 2.51 mm. The dust can lead to a serious negative influence on the production of sintering and blast furnaces （BF） if it is recycled in sintering. The briquette and reduction experimental results showed that the qualified strength could be obtained in the case of 8wt% molasses or 4wt% QT-10 added as binders. Also, more than 75% of metallization ratio, more than 95% of dezincing ratio, as well as more than 80% of K and Na removal rates were achieved for the briquettes kept at 1250℃ for 15 min during the direct reduction process. SEM observation indicated that the rates of indirect reduction and carbonization became dominating when the bri-quettes were kept at 1250℃ for 6 min.
基金This work was financially supported by the National Natural Science Foundation of China （Grant No. 51574023） and National Key Research and Development Program of China （2016YFB0600701）.
文摘Four types of coals, KL, XB, ZS and GD with different coal ranks, were dissolved with the organic solvent N-methyl-2- pyrrolidone at 350 ℃ and around 3.0 MPa pressure to obtain thermal soluble constituents （TSCs）. The yield, component and maceral group were investigated as well as their coking properties, including caking index and thermoplasticity. The results indicated that the yields of the four coals were of the following order： KL 〉 XB 〉 ZS 〉 GD. Based on the yield and the vitrinite content, coals were ranked from high to low. The ash contents of TSCs were significantly less than that of raw coals, and the TSCs contain more light components, leading to an increase in volatile matter. The patterns of Fourier transform infrared spectroscopy indicated that carbonyl was enriched in TSCs. Regarding the maceral group, TSCs were mainly composed of vitrinite which is the main reactive material and converts into binder phase in cokemaking process. Higher caking index values and fluidity were obtained in TSCs compared with the raw coals. The coking experiments with different amounts of TSCs addition were carried out. The results demonstrated that the proper TSCs addition could enhance the coke strength due to its high caking index and good fluidity.
基金This work was financially supported by the National Key R&D Program of China(No.2018YFB0605900).
文摘CaO-containing carbon pellets(CCCP)were successfully prepared from well-mixed coking coal(CC)and calcium oxide(CaO)and roasted at different pyrolysis temperatures.The effects of temperature,pore distribution,and carbon structure on the compressive strength of CCCP was investigated in a pyrolysis furnace(350-750℃).The results showed that as the roasting temperature increased,the compressive strength also increased and furthermore,structural defects and imperfections in the carbon crystallites were gradually eliminated to form more organized char structures,thus forming high-ordered CC.Notably,the CCCP preheated at 750℃exhibited the highest compressive strength.A positive relationship between the compressive strength and pore-size homogeneity was established.A linear relationship between the com-pressive strength of the CCCP and the average stack height of CC was observed.Additionally,a four-stage caking mechanism was developed.
基金This study was conducted with financial support from the National Natural Science Foundation of China(No.51574023).
文摘The microstructure of coke has an important influence on its thermal properties.The solution loss reactions of coke in CO2 and H2O atmospheres were investigated by in situ observation.The results showed that the isotropic components had a more vigorous reaction than the anisotropic components,and the solution loss reaction of the fine-grained mosaic structure was faster than that of the coarse-grained mosaic structure under the CO2 and H2O atmospheres.The coarse-grained mosaic structure and the flowing structure had a relatively higher anti-erosion ability in the CO2 atmosphere than in the H2O atmosphere,and there was no distinct difference in the solution loss of the isotropic structure under the CO2 and H2O atmospheres.The electron probe microanalysis showed that the Al-Si-Fe compounds in the carbon matrix had positive influence on the solution loss reaction of the anisotropic structure.The iron compounds were able to destroy the pore walls of coke and accelerate the solution loss rate of coke.
基金financially supported by the National Basic Research Program of China (No. 2012CB720401)the National Key Technology Research and Development Program of China (No. 2011BAC01B02)
文摘Direct reduction of dust composite pellets containing zinc and iron was examined by simulating the conditions of actual production process of a rotary hearth furnace （RHF） in laboratory. A mathematical model was constructed to study the reduction kinetics of iron oxides and ZnO in the dust composite pellets. It was validated by comparing the calculated values with experimental results. The effects of furnace temperature, pellet radius, and pellet porosity on the reduction were investigated by the model. It is shown that furnace temperature has obvious influence on both of the reduction of iron oxides and ZnO, but the influence of pellet radius and porosity is much smaller. Model calculations suggest that both of the reduction of iron oxides and ZnO are under mixed control with interface reactions and Boudouard reaction in the early stage, but only with interface reactions in the later stage.
基金Item Sponsored by National Basic Research Program of China(2012CB720401)National Natural Science Foundation of China and Baosteel(51134008)
文摘The softening and melting behavior of sinter, pellet and mixed burden was researched through high tem- perature reaction tests under load simulating traditional blast furnace （T-BF） and oxygen blast furnace （OBF） condi- tions. The results indicated that compared with T-BF, the softening zone of sinter and pellet became wide, but the melting zone became narrow in OBF. The permeabilities of both sinter and pellet were improved in OBF. Under the condition of OBF, the temperature of softening zone of mixed burden was increased by 63 K, but the temperature of melting zone was decreased by 76 K. Therefore, the permeability of material layer was significantly improved. This was mainly caused by the change of the melting behavior of pellet. In addition, the quality Of dripping iron in OBF was much better than that of T-BF.
基金financially supported by the China Postdoctoral Science Foundation(No.2018T110046)the National Natural Science Foundation of China(No.51274033)
文摘Ludwigite is a kind of complex iron ore containing boron, iron, and magnesium, and it is the most promising boron resource in China. Selective reduction of iron oxide is the key step for the comprehensive utilization of ludwigite. In the present work, the reduction mechanism of ludwigite was investigated. The thermogravimetry and differential scanning calorimetry analysis and isothermal reduction of ludwigite/coal composite pellet were performed. Ludwigite yielded a lower reduction starting temperature and a higher final reduction degree compared with the traditional iron concentrates. Higher specific surface area and more fine cracks might be the main reasons for the better reducibility of ludwigite. Reducing temperature highly affected the reaction fraction and microstructure of the reduced pellets, which are closely related to the separation degree of boron and iron. Increasing reducing temperature benefited the boron and iron magnetic separation. Optimum magnetic separation results could be obtained when the pellet was reduced at 1300°C. The separated boron-rich non-magnetic concentrate presented poor crystalline structure, and its extraction efficiency for boron reached 64.3%. The obtained experimental results can provide reference for the determination of the comprehensive utilization flow sheet of ludwigite.
基金National Key Research and Development Program of China(No.2016YFB0601304).
文摘Blast furnace ironmaking process is the most mature and highly effective process for producing liquid iron.Blast furnace is a gas-solid and gas-solid-liquid countercurrent reactor,and maintaining gas permeability is the precondition of smooth production.Therefore,improving the gas permeability throughout the blast furnace remains a hot issue which is concerned by many metallurgical scholars.According to the research results of many scholars,the dominant factors influencing the gas permeability of different locations in the blast furnace(locations are distinguished according to the morphology change of the burdens)were reviewed.And the strategies for improving the gas permeability of different locations in the blast furnace were summarized based on these dominant influencing factors,such as suppressing the low-temperature reduction degradation of sinter in the lump zone,improving the indirect reduction degree and suppressing the interaction between different burdens.It is hoped to provide both theoretical and practical values for guiding the blast furnace so as to improve smooth operation and smelting efficiency.
基金The authors gratefully acknowledge the financial support of the National Natural Science Foundation of China(Nos.U1960205 and 51804024).
文摘The softening-melting characteristics of ferrous burden play a crucial role in the thickness and position of the cohesive zone.The influence of the basicity and experimental atmosphere on the softening-melting behavior of primary slag under slag-coke interaction was investigated using in situ visualization method.The mechanism was analyzed using the FactSage software,X-ray diffraction,and electron probe microanalysis.The softening and melting temperatures of the samples increased with increasing basicity under different atmospheres.The difference between softening and melting temperatures is smaller in a H_(2) atmosphere than in a CO atmosphere;in H_(2) atmosphere,the range of softening zone in the cohesive zone was significantly thinner.The formed low-melting-point FeO-bearing phases decrease when H_(2) was used as the reducing agent.In addition,according to FactSage calculations,the high content of metallic iron reduced in the H_(2) atmosphere raised the softening temperature of the primary slag.It also narrowed and moved downward the cohesive zone due to an increase in softening and melting temperatures.Meanwhile,the increase in basicity promoted the decrease in liquid ratio and improved the permeability of cohesive zone.
基金financial support of the Fundamental Research Funds for the Central Universities (FRF-TP-16-019A1)the State Key Laboratory of Advanced Metallurgy (41617007), University of Science and Technology Beijing
文摘To support the development of technology to utilize low-grade Ti-Nb-bearing Fe concentrate, the reduction of the concentrate by coal was systematically investigated in the present paper. A liquid phase formed when the Ti Nb-bearing Fe concentrate/coal composite pel- let was reduced at temperatures greater than 1100℃. The addition of CaCO3 improved the reduction rate when the slag basicity was less than 1.0 and inhibited the formation of the liquid phase. Mechanical milling obviously increased the metallization degree compared with that of the standard pellet when reduced under the same conditions. Evolution of the mineral phase composition and microstructure of the reduced Ti-Nb-bearing Fe concentrate/coal composite pellet at 1100~C were analyzed by X-ray diffraction and scanning electron microsco- py-energy-dispersive spectroscopy. The volume shrinkage value of the reduced Ti-Nb-bearing Fe concentrate/coal composite pellet with a basicity of 1.0 was approximately 35.2% when the pellet was reduced at 1100℃ for 20 min, which enhanced the external heat transfer to the lower layers when reduced in a practical rotary hearth furnace. The present work provides key parameters and mechanism understanding for the development of carbothermic reduction technology of a Ti-Nb-bearing Fe concentrate incorporated in a pyrometallurgical utilization flow sheet.
基金financially supported by the National Natural Science Foundation of China (No. 51274033)
文摘A novel process for boron enrichment and extraction from ludwigite based on iron nugget technology was proposed. The key steps of this novel process, which include boron and iron separation, crystallization of boron-rich slag, and elucidation of the boron extraction be- havior of boron-rich slag by acid leaching, were performed at the laboratory. The results indicated that 95.7% of the total boron could be en- riched into the slag phase, thereby forming a boron-rich slag during the iron and slag melting separation process. Suanite and kotoite were observed to be the boron-containing crystalline phases, and the boron extraction properties of the boron-rich slag depended on the amounts and grain sizes of these minerals. When the boron-rich slag was slowly cooled to 1100℃, the slag crystallized well and the efficiency of ex- traction of boron （EEB） of the slag was the highest observed in the present study. The boron extraction property of the slow-cooled bo- ron-rich slag obtained in this study was much better than that of szaibelyite ore under the conditions of 80% of theoretical sulfuric acid amount, leaching time of 30 min, leaching temperature of 40℃ ,and liquid-to-solid ratio of 8 mL/g.
基金National Key Research and Development Program (No.2016YFB0601304)the State Key Laboratory of Advanced Metallurgy,University of Science and Technology Beijing(No.41616005)
文摘Aiming at the current characteristics of blast furnace （BF） process, carbon saving potential of blast furnace was investigated from the perspective of the relationship between degree of direct reduction and carbon consumption. A new relationship chart between carbon consumption and degree of direct reduction, which can reflect more real situation of blast furnace operation, was established. Further- more, the carbon saving potential of hydrogen-rich oxygen blast furnace （OBF） process was ana- lyzed. Then, the policy implications based on this relationship chart established were suggested. On this basis, the method of improving the carbon saving potential of blast furnace was recycling the top gas with removal of CO2 and H2O or increasing hydrogen in BF gas and full oxygen blast. The results show that the carbon saving potential in traditional blast furnace （TBF） is only 38 56 kg · t ^-1 while that in OBF is 138 kg · t ^-1. Theoretically, the lowest carbon consumpt!on of OBF is 261 kg · t ^-1 and the corresponding degree of direct reduction is 0.04. In addition, the theoretical lowest carbon consumption of hydrogen-rich OBF is 257 kg · t ^-1. The modeling analysis can be used to estimate the carbon savings potential in new ironmaking process and its related CO2 emissions.
基金The authors would like to express their gratitude for the financial support of the China Postdoctoral Science Foundation （No. 2016M600919） and National Natural Science Foundation of China （No. 51274033）.
文摘Realizing the boron and iron separation through selective reduction and melting separation of boron-bearing iron con- centrate is of great significance for the utilization of crude ludwigite. The reduction and melting separation mechanism of boron-bearing iron concentrate/coal composite pellet was systematically investigated. The reduction and melting separation test of small size pellet was performed to reveal the evolution of slag and iron in the melting separation process. The isothermal reduction experiment showed the relationship between reduction stage and melting separation stage, and the step reduction and melting separation was perfectly achieved. Coal particles existed through the reduction and melting separation process and finally formed brown residue around the separated product. The pellet could not realize melting separation when the B2O3 content in the concentrate was lower than 6.00 wt%.
基金Sponsored by National Basic Research Program of China(2012CB720401)Natural Science Foundation of China and Baosteel(51134008)
文摘The reduction behavior of pellet was researched through the programming apparatus under simulated con- ditions of oxygen blast furnace （OBF） and traditional blast furnace （T-BF）. The results indicated that compared with traditional blast furnace, the reduction starting temperature of pellet decreased by 60 ℃ under oxygen blast furnace condition. The reduction degree of pellet could almost reach 100% under oxygen blast furnace condition when the temperature reached 1100 ℃, whereas it was only 82.49% in traditional blast furnace. The content of carbon in pel- let of oxygen blast furnace was about 5 times more than that of traditional blast furnace. In addition, the microstruc- ture at the periphery and core of pellets after reaction was characterized by means of SEM and EDS.
