The direct reduction process can reduce carbon emissions by over 50%compared to traditional blast furnace ironmaking.Carbon deposition and carburization are critical for ensuring process stability and economic viabili...The direct reduction process can reduce carbon emissions by over 50%compared to traditional blast furnace ironmaking.Carbon deposition and carburization are critical for ensuring process stability and economic viability.Thermodynamic phase diagrams were developed to intuitively represent carbon deposition and carburization preferences in CH4-CO-H_(2) ternary atmospheres.High carbon potential and low oxygen potential significantly enhance carbon deposition and carburization.Increasing temperature from 500 to 1000℃ shifts the dominant reactions from CO-based to CH_(4)-based,increasing maximum carbon deposition from 0.55 to 0.80 mol and carburization from 0.25 to 0.80 mol per mole of reducing gas.Increasing pressure suppresses CH4-based reactions while promoting CO-based reactions,reducing maximum carbon deposition from 0.8 to~0.7 mol and increasing maximum carburization from 0.80 to 0.85 mol per mole of reducing gas.Equilibrium phase diagrams for various carbides were also developed,revealing preferences for Fe_(3)C_(2),Fe_(7)C_(3),Fe_(5)C_(2),and Fe_(3)C as the Fe/C ratio increases.Higher temperatures and CH_(4) concentrations favor the formation of carbides with higher carbon content.Carburization preferences under typical Energiron ZR and Midrex atmospheres were highlighted,and the higher carbon content in direct reduction iron produced by the Energiron ZR process was thermodynamically confirmed.展开更多
Phosphorus tends to migrate into metallic iron during the direct reduction of high-phosphorus oolitic iron ore,leading to undesirable phosphorus enrichment in metallic iron.However,the underlying reduction and migrati...Phosphorus tends to migrate into metallic iron during the direct reduction of high-phosphorus oolitic iron ore,leading to undesirable phosphorus enrichment in metallic iron.However,the underlying reduction and migration mechanisms remain poorly understood.Phosphorus behavior during coal-based reduction was systematically investigated through theoretical modeling and experimental approaches.Thermodynamic analysis revealed that the carbon reduction of solid Ca_(3)(PO_(4))_(2)to gaseous P_(2)requires temperatures exceeding 1400℃.Notably,this threshold significantly decreases to 1130.5℃in the presence of SiO_(2)and Al_(2)O_(3).Further investigations demonstrated that Ca_(3)(PO_(4))_(2)co-reduces with Fe_(x)O_(γ)in the presence of SiO_(2)-Al_(2)O_(3)-Fe_(x)O_(γ),forming Fe_(3)P(instead of gaseous P_(2))at a markedly lower temperature of 778.7℃.Mechanistic studies indicate that the inherent thermal stability of Ca_(3)(PO_(4))_(2)inhibits the generation of reactive[P_(2)O_(5)].However,SiO_(2)-Al_(2)O_(3)coexistence destabilizes Ca_(3)(PO_(4))_(2)while exponentially enhancing[P_(2)O_(5)]activity.This synergistic effect dramatically promotes the phosphorus mineral reduction.Characterization confirmed that Ca_(3)(PO_(4))_(2)migrated into the slag phase(4FeO·Al_(2)O_(3)·3SiO_(2)·CaO·P_(2)O_(5)).Subsequently,the reactive P_(2)O_(5)in slag is reduced with metallic iron to form Fe_(3)P,which further dissolves into theα-Fe matrix through solid-state diffusion,ultimately generating Fe-P solid solutions.展开更多
The novel process of hydrogen-based shaft furnaces(HSFs)has attracted considerable attention because of their significant reduction of CO_(2)emissions.In this study,the interaction of H_(2)and CO with Fe_(tet1)-and Fe...The novel process of hydrogen-based shaft furnaces(HSFs)has attracted considerable attention because of their significant reduction of CO_(2)emissions.In this study,the interaction of H_(2)and CO with Fe_(tet1)-and Fe_(oct2)-terminated Fe_(3)O_(4)(111)surfaces under HSF conditions,including their adsorption and reduction behaviors,was investigated using the density functional theory method.The results indicated that the H_(2)molecule adsorbed onto the Fe_(tet1)-terminated surface with an adsorption energy(AE)of-1.36 eV,whereas the CO molecule preferentially adsorbed on the Fe_(oct2)-terminated surface with an AE of-1.56 eV.Both H_(2)and CO can readily undergo reduction on the Fe_(tet1)-terminated surface(corresponding to energy barriers of 0.83 eV and 2.23 eV,respectively),but kinetically the reaction of H2is more favorable than that of CO.With regard to the thermodynamics at 400-1400 K,the H_(2)was easy to be adsorbed,while the CO would like to react on the Fe_(tet1)-terminated surface.These thermodynamically tendencies were reversed on the Fe_(oct2)-terminated surface.The thermodynamic disadvantage of the reaction of H_(2)on the Fe_(tet1)-terminated surface was offset by an increase in the temperature.Furthermore,the adsorption of H2 and CO on the Fe_(tet1)-terminated surface was competitive,whereas the adsorption of them on the Fe_(oct2)-terminated surface was synergistic.Therefore,iron ores with a higher proportion of Fe_(tet1)-terminated surface can be applied for the HSF process.In conjunction with the increases in the reduction temperature and the ratio of H_(2)in the reducing gas would promote efficient HSF smelting.These observations provide effective guidance for optimizing the practical operation parameters and advancing the development of the HSF process.展开更多
基金the financial support from the National Key R&D Program of China(No.2024YFC2910800)National Natural Science Foundation of China(52404336)+6 种基金China Postdoctoral Science Foundation(2024M750176)Postdoctoral Fellowship Program of CPSF(GZC20240109)the Young Elite Scientist Sponsorship Program by CAST(YESS20210090)Beijing Natural Science Foundation(J210017)the Project of SKLAM(No.KF24-14)China Baowu Low Carbon Metallurgical Technology Innovation Fund under Grant No.20210901Anhui Major Industrial Innovation Program under Contract No.AHZDCYCX-LSDT2023-01.
文摘The direct reduction process can reduce carbon emissions by over 50%compared to traditional blast furnace ironmaking.Carbon deposition and carburization are critical for ensuring process stability and economic viability.Thermodynamic phase diagrams were developed to intuitively represent carbon deposition and carburization preferences in CH4-CO-H_(2) ternary atmospheres.High carbon potential and low oxygen potential significantly enhance carbon deposition and carburization.Increasing temperature from 500 to 1000℃ shifts the dominant reactions from CO-based to CH_(4)-based,increasing maximum carbon deposition from 0.55 to 0.80 mol and carburization from 0.25 to 0.80 mol per mole of reducing gas.Increasing pressure suppresses CH4-based reactions while promoting CO-based reactions,reducing maximum carbon deposition from 0.8 to~0.7 mol and increasing maximum carburization from 0.80 to 0.85 mol per mole of reducing gas.Equilibrium phase diagrams for various carbides were also developed,revealing preferences for Fe_(3)C_(2),Fe_(7)C_(3),Fe_(5)C_(2),and Fe_(3)C as the Fe/C ratio increases.Higher temperatures and CH_(4) concentrations favor the formation of carbides with higher carbon content.Carburization preferences under typical Energiron ZR and Midrex atmospheres were highlighted,and the higher carbon content in direct reduction iron produced by the Energiron ZR process was thermodynamically confirmed.
基金supported by the National Key Research and Development Program of China(Nos.2023YFC3903900 and 2023YFC3903904)the National Natural Science Foundation Youth Foundation of China(No.52404356)the China Baowu Low Carbon Metallurgy Innovation Foundation(No.BWLCF202216)。
文摘Phosphorus tends to migrate into metallic iron during the direct reduction of high-phosphorus oolitic iron ore,leading to undesirable phosphorus enrichment in metallic iron.However,the underlying reduction and migration mechanisms remain poorly understood.Phosphorus behavior during coal-based reduction was systematically investigated through theoretical modeling and experimental approaches.Thermodynamic analysis revealed that the carbon reduction of solid Ca_(3)(PO_(4))_(2)to gaseous P_(2)requires temperatures exceeding 1400℃.Notably,this threshold significantly decreases to 1130.5℃in the presence of SiO_(2)and Al_(2)O_(3).Further investigations demonstrated that Ca_(3)(PO_(4))_(2)co-reduces with Fe_(x)O_(γ)in the presence of SiO_(2)-Al_(2)O_(3)-Fe_(x)O_(γ),forming Fe_(3)P(instead of gaseous P_(2))at a markedly lower temperature of 778.7℃.Mechanistic studies indicate that the inherent thermal stability of Ca_(3)(PO_(4))_(2)inhibits the generation of reactive[P_(2)O_(5)].However,SiO_(2)-Al_(2)O_(3)coexistence destabilizes Ca_(3)(PO_(4))_(2)while exponentially enhancing[P_(2)O_(5)]activity.This synergistic effect dramatically promotes the phosphorus mineral reduction.Characterization confirmed that Ca_(3)(PO_(4))_(2)migrated into the slag phase(4FeO·Al_(2)O_(3)·3SiO_(2)·CaO·P_(2)O_(5)).Subsequently,the reactive P_(2)O_(5)in slag is reduced with metallic iron to form Fe_(3)P,which further dissolves into theα-Fe matrix through solid-state diffusion,ultimately generating Fe-P solid solutions.
基金financially supported by the Key Program of National Natural Science Foundation of China(No.U23A20608)the Liaoning Province Science and Technology Plan Joint Program(Key Research and Development Program Project),China(No.2023JH2/101800058)+3 种基金the Science&Technology Plan Project of Hebei Province,China(No.23314601L)the Project of Hydrogen-Based Shaft Furnace Reduction-Electric Furnace Melting And Separation Technology Research and Application for High-Titanium Magnetite Iron Ore(No.HG2023239)the General Program of National Natural Science Foundation of China(No.52274253)the Special Project for Major Scientific and Technological Achievements Transformation in Hebei Province,China(No.23284101Z)。
文摘The novel process of hydrogen-based shaft furnaces(HSFs)has attracted considerable attention because of their significant reduction of CO_(2)emissions.In this study,the interaction of H_(2)and CO with Fe_(tet1)-and Fe_(oct2)-terminated Fe_(3)O_(4)(111)surfaces under HSF conditions,including their adsorption and reduction behaviors,was investigated using the density functional theory method.The results indicated that the H_(2)molecule adsorbed onto the Fe_(tet1)-terminated surface with an adsorption energy(AE)of-1.36 eV,whereas the CO molecule preferentially adsorbed on the Fe_(oct2)-terminated surface with an AE of-1.56 eV.Both H_(2)and CO can readily undergo reduction on the Fe_(tet1)-terminated surface(corresponding to energy barriers of 0.83 eV and 2.23 eV,respectively),but kinetically the reaction of H2is more favorable than that of CO.With regard to the thermodynamics at 400-1400 K,the H_(2)was easy to be adsorbed,while the CO would like to react on the Fe_(tet1)-terminated surface.These thermodynamically tendencies were reversed on the Fe_(oct2)-terminated surface.The thermodynamic disadvantage of the reaction of H_(2)on the Fe_(tet1)-terminated surface was offset by an increase in the temperature.Furthermore,the adsorption of H2 and CO on the Fe_(tet1)-terminated surface was competitive,whereas the adsorption of them on the Fe_(oct2)-terminated surface was synergistic.Therefore,iron ores with a higher proportion of Fe_(tet1)-terminated surface can be applied for the HSF process.In conjunction with the increases in the reduction temperature and the ratio of H_(2)in the reducing gas would promote efficient HSF smelting.These observations provide effective guidance for optimizing the practical operation parameters and advancing the development of the HSF process.
