The rheological properties of an innovative coal-based colloidal composite binder(3Co-Binder)prepared via alkaline–oxygen excitation and mechanochemical synthesis are revealed.Derived from low-rank coal,3Co–Binder i...The rheological properties of an innovative coal-based colloidal composite binder(3Co-Binder)prepared via alkaline–oxygen excitation and mechanochemical synthesis are revealed.Derived from low-rank coal,3Co–Binder is applied in iron ore pelletization as a replacement for traditional bentonite,with the aim of improving the iron grades of the pellets.Cryoscanning electron microscopy revealed that 3Co-Binder exhibits a densely populated,porous network structure.It was determined to be a pseudo-plastic fluid with yield stress and shear-thinning characteristics.The stability of 3Co-Binder was influenced by the humic acid extraction rate,temperature,and static placing time.An extraction rate of humic acids above 96%was found to prevent sedimentation of 3Co-Binder,while lower temperatures and prolonged static placing time increased its apparent viscosity.A storage duration of less than 2 weeks and a temperature range of 25–35℃ were found to be optimal for maintaining the stability of 3Co-Binder.The viscous flow activation energy of 3Co-Binder remained stable at approximately 60 kJ mol^(-1) as the shear rate increased from 0.5 to 5 s^(-1).However,at higher shear rates,up to 100 s^(-1),the viscous flow activation energy decreased to 46.48 kJ mol^(–1).To ensure stability and dispersibility during storage,the rheological parameters of 3Co-Binder must meet the following criteria:yield stress below 10 Pa,consistency coefficient below 1.5 Pa s,non-Newtonian index below 1,and apparent viscosity below 10,000 mPa s at a shear rate of 1 s^(–1).展开更多
Roasting experiments were carried out with pure reagents as raw materials.The self-sintering behaviors of molybdenite(MoS_(2))during oxidation were investigated by thermodynamic calculation,XRD,SEM-EDS and high-temper...Roasting experiments were carried out with pure reagents as raw materials.The self-sintering behaviors of molybdenite(MoS_(2))during oxidation were investigated by thermodynamic calculation,XRD,SEM-EDS and high-temperature in situ analysis.The results indicate that the desulfurization efficiency of MoS_(2)pellet decreases with the increase of roasting temperature from 600 to 700℃,owing to the expansion of sintered area.At the very beginning of roasting,sintered layer can be rapidly formed and cover the pellet surface on the windward side,and meanwhile,MoO_(2)and Mo_(4)O_(11)intensively appear and constitute the sintered layer together with MoO_(3).Moreover,it is proven that MoO_(3)-rich products containing low-valence molybdenum oxides have low melting points,thus easy to be melted during the occurrence of exothermic reaction between MoS_(2)and O_(2),which leads to the sintering of materials.展开更多
Poor permeability and low sintering productivity restrict the development of high-bed sintering.An efficient method of the double-layer sintering process(DLSP)was proposed to achieve high-bed sintering and solve the a...Poor permeability and low sintering productivity restrict the development of high-bed sintering.An efficient method of the double-layer sintering process(DLSP)was proposed to achieve high-bed sintering and solve the aforementioned problems.Theoretical calculation and sintering pot experiments were implemented to investigate the double-layer sintering process.Traditional sintering process and DLSP were compared in terms of sintering indices,metallurgical properties and morphology characterization.Under the condition of traditional sintering process,DLSP successfully realized fast velocity and highly productive sintering of 1000-mm high bed.After the sintering bed is charged and ignited twice,the air permeability of the bed has been greatly improved.Sintering time is shortened significantly by simultaneous sintering of the upper and lower feed layers.Under the condition of bed height proportion of 350/650 mm and pre-sintering time of 20 min,the yield,tumbler strength,productivity and solid fuel consumption are 69.96%,65.87%,1.71 t(m^(2)h)^(-1)and 56.71 kg/t,respectively.Magnetite,hematite,calcium ferrite and complex calcium ferrite are the main phases of DLSP products.The metallurgical properties of DSLP products meet the requirement of ironmaking.It indicates that DLSP is an effective method to solve the disadvantages of bad permeability and low sintering productivity in high-bed sintering.展开更多
Effect of distribution of iron concentrates between pelletized and matrix feed on the preparation of blast furnace burdens from two different kinds of fine iron concentrates (magnetite and hematite) by composite agglo...Effect of distribution of iron concentrates between pelletized and matrix feed on the preparation of blast furnace burdens from two different kinds of fine iron concentrates (magnetite and hematite) by composite agglomeration process (CAP) was explored. It was found that when the mass ratio of iron concentrate A (magnetite) to iron concentrate B (hematite) in the mixed feed was constant, the proportion of iron concentrate A in the pelletized and matrix feed significantly affected the quality of CAP products. Particularly, as the proportion of iron concentrate A in the pelletized feed increased from 0 to 100%, the yield decreased from 82.11% to 79.19% and the tumbler index decreased from 71.33% to 68.27%. The mineralization characterization results indicated that when 100% iron concentrate A was used as the pelletized feed, the crystallization styles of the outer layer and the inner layer of the pellet were different, and a lot of pores exist around hematite and magnetite phases in the pelletized part, with the weak connection of pelletized and matrix part, resulting in poor strength of agglomeration product.展开更多
In pyrometallurgical process, Al-and Si-bearing minerals in iron and aluminum ores are easily transformed into sodium aluminosilicates in the presence of Na_2O constituents, which alters the leaching behaviors of Al_2...In pyrometallurgical process, Al-and Si-bearing minerals in iron and aluminum ores are easily transformed into sodium aluminosilicates in the presence of Na_2O constituents, which alters the leaching behaviors of Al_2O_3 and SiO_2. It was confirmed that sodium aluminosilicates with different phase compositions synthesized at various roasting conditions were effectively digested in the alkaline digestion process. Under the optimum conditions at temperature of 100–120°C, liquid-to-solid ratio(L/S) of 10:2 mL/g, caustic ratio of 4, and Na_2O concentration of 240 g/L, the actual and relative digestion ratio of Al_2O_3 from the synthesized sodium aluminosilicates reached maximums of about 65% and 95%, respectively, while SiO_2 was barely leached out. To validate the superior digestion property of sodium aluminosilicate generated via an actual process, the Bayer digestion of an Al_2O_3-rich material derived from reductive roasting of bauxite and comprising Na_(1.75) Al_(1.75) Si_(0.25)O_4 was conducted; the relative digestion ratio of Al_2O_3 attained 90% at 200°C.展开更多
基金supported by National Natural Science Foundation of China(No.52204302)Young Elite Scientist Sponsorship Program by CAST(No.YESS20220533)+1 种基金China Postdoctoral Science Foundation(No.2022M713519)Graduate Research Innovation Project of Central South University(No.1053320210230).
文摘The rheological properties of an innovative coal-based colloidal composite binder(3Co-Binder)prepared via alkaline–oxygen excitation and mechanochemical synthesis are revealed.Derived from low-rank coal,3Co–Binder is applied in iron ore pelletization as a replacement for traditional bentonite,with the aim of improving the iron grades of the pellets.Cryoscanning electron microscopy revealed that 3Co-Binder exhibits a densely populated,porous network structure.It was determined to be a pseudo-plastic fluid with yield stress and shear-thinning characteristics.The stability of 3Co-Binder was influenced by the humic acid extraction rate,temperature,and static placing time.An extraction rate of humic acids above 96%was found to prevent sedimentation of 3Co-Binder,while lower temperatures and prolonged static placing time increased its apparent viscosity.A storage duration of less than 2 weeks and a temperature range of 25–35℃ were found to be optimal for maintaining the stability of 3Co-Binder.The viscous flow activation energy of 3Co-Binder remained stable at approximately 60 kJ mol^(-1) as the shear rate increased from 0.5 to 5 s^(-1).However,at higher shear rates,up to 100 s^(-1),the viscous flow activation energy decreased to 46.48 kJ mol^(–1).To ensure stability and dispersibility during storage,the rheological parameters of 3Co-Binder must meet the following criteria:yield stress below 10 Pa,consistency coefficient below 1.5 Pa s,non-Newtonian index below 1,and apparent viscosity below 10,000 mPa s at a shear rate of 1 s^(–1).
基金financially supported by the Basic Science Center Program of the National Natural Science Foundation of China(No.72088101)the General Program of the National Natural Science Foundation of China(No.51874355)the Special Funding of China Postdoctoral Science Foundation(No.2020T130730)。
文摘Roasting experiments were carried out with pure reagents as raw materials.The self-sintering behaviors of molybdenite(MoS_(2))during oxidation were investigated by thermodynamic calculation,XRD,SEM-EDS and high-temperature in situ analysis.The results indicate that the desulfurization efficiency of MoS_(2)pellet decreases with the increase of roasting temperature from 600 to 700℃,owing to the expansion of sintered area.At the very beginning of roasting,sintered layer can be rapidly formed and cover the pellet surface on the windward side,and meanwhile,MoO_(2)and Mo_(4)O_(11)intensively appear and constitute the sintered layer together with MoO_(3).Moreover,it is proven that MoO_(3)-rich products containing low-valence molybdenum oxides have low melting points,thus easy to be melted during the occurrence of exothermic reaction between MoS_(2)and O_(2),which leads to the sintering of materials.
基金the National Key Research and Development Program of China(2017YFB0304301)the Fundamental Research Funds for the Central Universities of Central South University(No.202044016).
文摘Poor permeability and low sintering productivity restrict the development of high-bed sintering.An efficient method of the double-layer sintering process(DLSP)was proposed to achieve high-bed sintering and solve the aforementioned problems.Theoretical calculation and sintering pot experiments were implemented to investigate the double-layer sintering process.Traditional sintering process and DLSP were compared in terms of sintering indices,metallurgical properties and morphology characterization.Under the condition of traditional sintering process,DLSP successfully realized fast velocity and highly productive sintering of 1000-mm high bed.After the sintering bed is charged and ignited twice,the air permeability of the bed has been greatly improved.Sintering time is shortened significantly by simultaneous sintering of the upper and lower feed layers.Under the condition of bed height proportion of 350/650 mm and pre-sintering time of 20 min,the yield,tumbler strength,productivity and solid fuel consumption are 69.96%,65.87%,1.71 t(m^(2)h)^(-1)and 56.71 kg/t,respectively.Magnetite,hematite,calcium ferrite and complex calcium ferrite are the main phases of DLSP products.The metallurgical properties of DSLP products meet the requirement of ironmaking.It indicates that DLSP is an effective method to solve the disadvantages of bad permeability and low sintering productivity in high-bed sintering.
基金supported by the National Natural Science Foundation of China under Grant U1960114,51774337,and U1660206the Open Sharing Fund for the Large-scale Instruments and Equipments of Central South University under Grant CSUZC201905the Fundamental Research Funds for the Central Universities of Central South University under Grant 2018zzts220.
文摘Effect of distribution of iron concentrates between pelletized and matrix feed on the preparation of blast furnace burdens from two different kinds of fine iron concentrates (magnetite and hematite) by composite agglomeration process (CAP) was explored. It was found that when the mass ratio of iron concentrate A (magnetite) to iron concentrate B (hematite) in the mixed feed was constant, the proportion of iron concentrate A in the pelletized and matrix feed significantly affected the quality of CAP products. Particularly, as the proportion of iron concentrate A in the pelletized feed increased from 0 to 100%, the yield decreased from 82.11% to 79.19% and the tumbler index decreased from 71.33% to 68.27%. The mineralization characterization results indicated that when 100% iron concentrate A was used as the pelletized feed, the crystallization styles of the outer layer and the inner layer of the pellet were different, and a lot of pores exist around hematite and magnetite phases in the pelletized part, with the weak connection of pelletized and matrix part, resulting in poor strength of agglomeration product.
基金financially supported by the National Natural Science foundation of China (Nos. 51234008 and 51174230)the Program for New Century Excellent Talents in University of Ministry of Education of China (No. NCET-11-0515)
文摘In pyrometallurgical process, Al-and Si-bearing minerals in iron and aluminum ores are easily transformed into sodium aluminosilicates in the presence of Na_2O constituents, which alters the leaching behaviors of Al_2O_3 and SiO_2. It was confirmed that sodium aluminosilicates with different phase compositions synthesized at various roasting conditions were effectively digested in the alkaline digestion process. Under the optimum conditions at temperature of 100–120°C, liquid-to-solid ratio(L/S) of 10:2 mL/g, caustic ratio of 4, and Na_2O concentration of 240 g/L, the actual and relative digestion ratio of Al_2O_3 from the synthesized sodium aluminosilicates reached maximums of about 65% and 95%, respectively, while SiO_2 was barely leached out. To validate the superior digestion property of sodium aluminosilicate generated via an actual process, the Bayer digestion of an Al_2O_3-rich material derived from reductive roasting of bauxite and comprising Na_(1.75) Al_(1.75) Si_(0.25)O_4 was conducted; the relative digestion ratio of Al_2O_3 attained 90% at 200°C.
