Search2023 Vol. 30, No. 2
Display Method:
2023, vol. 30, no. 2, pp.
193-208.
https://doi.org/10.1007/s12613-022-2537-x
Abstract:
Cemented paste backfill (CPB) technology is a green mining method used to control underground goaves and tailings ponds. The curing process of CPB in the stope is the product of a thermo–hydro–mechanical–chemical multi-field performance interaction. At present, research on the multi-field performance of CPB mainly includes indoor similar simulation experiments, in-situ multi-field performance monitoring experiments, multi-field performance coupling model construction of CPB, and numerical simulation of the multi-field performance of CPB. Because it is hard to study the in-situ multi-field performance of CPB in the real stope, most current research on in-situ multi-field performance adopts the numerical simulation method. By simulating the conditions of CPB in the real stope (e.g., maintenance environment, stope geometry, drainage conditions, and barricade and backfilling rates), the multi-field performance of CPB is further studied. This paper summarizes the mathematical models employed in the numerical simulation and lists the engineering application cases of numerical simulation in the in-situ multi-field performance of CPB. Finally, it proposes that the multi-field performance of CPB needs to strengthen the theoretical study of multi-field performance, form the strength design criterion based on the multi-field performance of CPB, perform a full-range numerical simulation of the multi-field performance of CPB, develop a pre-warning technology for the CPB safety of CPB, develop automatic and wireless sensors for the multi-field performance monitoring of CPB, and realize the application and popularization of CPB monitoring technology.
Cemented paste backfill (CPB) technology is a green mining method used to control underground goaves and tailings ponds. The curing process of CPB in the stope is the product of a thermo–hydro–mechanical–chemical multi-field performance interaction. At present, research on the multi-field performance of CPB mainly includes indoor similar simulation experiments, in-situ multi-field performance monitoring experiments, multi-field performance coupling model construction of CPB, and numerical simulation of the multi-field performance of CPB. Because it is hard to study the in-situ multi-field performance of CPB in the real stope, most current research on in-situ multi-field performance adopts the numerical simulation method. By simulating the conditions of CPB in the real stope (e.g., maintenance environment, stope geometry, drainage conditions, and barricade and backfilling rates), the multi-field performance of CPB is further studied. This paper summarizes the mathematical models employed in the numerical simulation and lists the engineering application cases of numerical simulation in the in-situ multi-field performance of CPB. Finally, it proposes that the multi-field performance of CPB needs to strengthen the theoretical study of multi-field performance, form the strength design criterion based on the multi-field performance of CPB, perform a full-range numerical simulation of the multi-field performance of CPB, develop a pre-warning technology for the CPB safety of CPB, develop automatic and wireless sensors for the multi-field performance monitoring of CPB, and realize the application and popularization of CPB monitoring technology.
2023, vol. 30, no. 2, pp.
209-224.
https://doi.org/10.1007/s12613-022-2544-y
Abstract:
Lithium is considered to be the most important energy metal of the 21st century. Because of the development trend of global electrification, the consumption of lithium has increased significantly over the last decade, and it is foreseeable that its demand will continue to increase for a long time. Limited by the total amount of lithium on the market, lithium extraction from natural resources is still the first choice for the rapid development of emerging industries. This paper reviews the recent technological developments in the extraction of lithium from natural resources. Existing methods are summarized by the main resources, such as spodumene, lepidolite, and brine. The advantages and disadvantages of each method are compared. Finally, reasonable suggestions are proposed for the development of lithium extraction from natural resources based on the understanding of existing methods. This review provides a reference for the research, development, optimization, and industrial application of future processes.
Lithium is considered to be the most important energy metal of the 21st century. Because of the development trend of global electrification, the consumption of lithium has increased significantly over the last decade, and it is foreseeable that its demand will continue to increase for a long time. Limited by the total amount of lithium on the market, lithium extraction from natural resources is still the first choice for the rapid development of emerging industries. This paper reviews the recent technological developments in the extraction of lithium from natural resources. Existing methods are summarized by the main resources, such as spodumene, lepidolite, and brine. The advantages and disadvantages of each method are compared. Finally, reasonable suggestions are proposed for the development of lithium extraction from natural resources based on the understanding of existing methods. This review provides a reference for the research, development, optimization, and industrial application of future processes.
2023, vol. 30, no. 2, pp.
225-235.
https://doi.org/10.1007/s12613-021-2397-9
Abstract:
Rod milling sand (RMS)—a coarse sand aggregate—was recycled for cemented paste backfill (CPB) for the underground mined area at the Jinchuan nickel deposit, named rod milling sand-based cemented paste backfill (RCPB). The adverse effects of coarse particles on the transportation of CPB slurry through pipelines to underground stopes resulting in weakening of the stability of the backfill system are well known. Therefore, sulfonated naphthalene formaldehyde (SNF) condensate was used for the performance improvement of RCPB. The synergistic effect of solid content (SC), lime-to-sand ratio, and SNF dosage on the rheological and physicomechanical properties, including slump, yield stress, bleeding rate, uniaxial compressive strength (UCS), as well as mechanism analysis of RCPB, have been explored. The results indicate that the effect of SNF on RCPB performance is related to the SNF dosage, lime-to-sand ratio, and SC. The slump of fresh RCPB with 0.1wt%–0.5wt% SNF increased by 2.6%–26.2%, whereas the yield stress reduced by 4.1%–50.3%, indicating better workability and improved cohesiveness of the mix. The bleeding rate of fresh RCPB decreased first and then rose with the increase of SNF dosage, and the peak decrease was 67.67%. UCS of RCPB first increased and then decreased with the increase of SNF dosage. At the optimal SNF addition ratio of 0.3wt%, the UCS of RCPB curing for 7, 14 and, 28 d ages increased by 31.5%, 28.4%, and 29.5%, respectively. The beneficial effects of SNF in enhancing the early UCS of RCPB have been corroborated. However, the later UCS increases at a slower rate. The research findings may guide the design and preparation of RCPB with adequate performance for practical applications.
Rod milling sand (RMS)—a coarse sand aggregate—was recycled for cemented paste backfill (CPB) for the underground mined area at the Jinchuan nickel deposit, named rod milling sand-based cemented paste backfill (RCPB). The adverse effects of coarse particles on the transportation of CPB slurry through pipelines to underground stopes resulting in weakening of the stability of the backfill system are well known. Therefore, sulfonated naphthalene formaldehyde (SNF) condensate was used for the performance improvement of RCPB. The synergistic effect of solid content (SC), lime-to-sand ratio, and SNF dosage on the rheological and physicomechanical properties, including slump, yield stress, bleeding rate, uniaxial compressive strength (UCS), as well as mechanism analysis of RCPB, have been explored. The results indicate that the effect of SNF on RCPB performance is related to the SNF dosage, lime-to-sand ratio, and SC. The slump of fresh RCPB with 0.1wt%–0.5wt% SNF increased by 2.6%–26.2%, whereas the yield stress reduced by 4.1%–50.3%, indicating better workability and improved cohesiveness of the mix. The bleeding rate of fresh RCPB decreased first and then rose with the increase of SNF dosage, and the peak decrease was 67.67%. UCS of RCPB first increased and then decreased with the increase of SNF dosage. At the optimal SNF addition ratio of 0.3wt%, the UCS of RCPB curing for 7, 14 and, 28 d ages increased by 31.5%, 28.4%, and 29.5%, respectively. The beneficial effects of SNF in enhancing the early UCS of RCPB have been corroborated. However, the later UCS increases at a slower rate. The research findings may guide the design and preparation of RCPB with adequate performance for practical applications.
2023, vol. 30, no. 2, pp.
236-249.
https://doi.org/10.1007/s12613-022-2557-6
Abstract:
For mines with poor ore bodies and surrounding rocks, the general mining method does not allow the ore to be extracted from underground safely and efficiently. For these mines, the downward layered filling mining technique is undoubtedly the most suitable mining method. The downward filling mining technique may eliminate the troubles relating to poor ore deposit conditions, such as production safety, ore loss rate, and depletion rate. However, in this technique, the safety of the artificial roof of the next stratum is of paramount importance. Cementitious tailings backfilling (CTB) that is not sufficiently cemented and causes collapses could threaten ore production. This paper explores a diamond-shaped composite structure to mimic the stability of a glued false roof in an actual infill mine based on the recently emerged three-dimensional (3D) printing technology. Experimental means such as three-point bending and digital image correlation (DIC) techniques were used to explore the flexural characteristics of 3D construction specimens and CTB combinations with different cement/tailings weight ratios at diverse layer heights. The results show that the 3D structure with a 14-mm ply height and CTB has strong flexural characteristics, with a maximum deflection value of 30.1 mm, while the 3D-printed rhomboid polymer (3D-PRP) structure with a 26-mm ply height is slightly worse in terms of flexural strength characteristics, but it has a higher maximum flexural strength of 2.83 MPa. A combination of 3D structure and CTB has more unique mechanical properties than CTB itself. This research work offers practical knowledge on the artificial roof performance of the downward layered filling mining technique and builds a scientific knowledge base regarding the successful application of CTB material in mines.
For mines with poor ore bodies and surrounding rocks, the general mining method does not allow the ore to be extracted from underground safely and efficiently. For these mines, the downward layered filling mining technique is undoubtedly the most suitable mining method. The downward filling mining technique may eliminate the troubles relating to poor ore deposit conditions, such as production safety, ore loss rate, and depletion rate. However, in this technique, the safety of the artificial roof of the next stratum is of paramount importance. Cementitious tailings backfilling (CTB) that is not sufficiently cemented and causes collapses could threaten ore production. This paper explores a diamond-shaped composite structure to mimic the stability of a glued false roof in an actual infill mine based on the recently emerged three-dimensional (3D) printing technology. Experimental means such as three-point bending and digital image correlation (DIC) techniques were used to explore the flexural characteristics of 3D construction specimens and CTB combinations with different cement/tailings weight ratios at diverse layer heights. The results show that the 3D structure with a 14-mm ply height and CTB has strong flexural characteristics, with a maximum deflection value of 30.1 mm, while the 3D-printed rhomboid polymer (3D-PRP) structure with a 26-mm ply height is slightly worse in terms of flexural strength characteristics, but it has a higher maximum flexural strength of 2.83 MPa. A combination of 3D structure and CTB has more unique mechanical properties than CTB itself. This research work offers practical knowledge on the artificial roof performance of the downward layered filling mining technique and builds a scientific knowledge base regarding the successful application of CTB material in mines.
2023, vol. 30, no. 2, pp.
250-259.
https://doi.org/10.1007/s12613-022-2503-7
Abstract:
CaCl2·6H2O/expanded vermiculite shape stabilized phase change materials (CEV) was prepared by atmospheric impregnation method. Using gold mine tailings as aggregate of cemented paste backfill (CPB) material, the CPB with CEV added was prepared, and the specific heat capacity, thermal conductivity, and uniaxial compressive strength (UCS) of CPB with different cement−tailing ratios and CEV addition ratios were tested, the influence of the above variables on the thermal and mechanical properties of CPB was analyzed. The results show that the maximum encapsulation capacity of expanded vermiculite for CaCl2·6H2O is about 60%, and the melting and solidification enthalpies of CEV can reach 98.87 J/g and 97.56 J/g, respectively. For the CPB without CEV, the specific heat capacity, thermal conductivity, and UCS decrease with the decrease of cement−tailing ratio. For the CPB with CEV added, with the increase of CEV addition ratio, the specific heat capacity increases significantly, and the sensible heat storage capacity and latent heat storage capacity can be increased by at least 10.74% and 218.97% respectively after adding 12% CEV. However, the addition of CEV leads to the increase of pores, and the thermal conductivity and UCS both decrease with the increase of CEV addition. When cement–tailing ratio is 1:8 and 6%, 9%, and 12% of CEV are added, the 28-days UCS of CPB is less than 1 MPa. Considering the heat storage capacity and cost price of backfill, the recommended proportion scheme of CPB material presents cement−tailing ratio of 1:6 and 12% CEV, and the most recommended heat storage/release temperature cycle range of CPB with added CEV is from 20 to 40°C. This work can provide theoretical basis for the utilization of heat storage backfill in green mines.
CaCl2·6H2O/expanded vermiculite shape stabilized phase change materials (CEV) was prepared by atmospheric impregnation method. Using gold mine tailings as aggregate of cemented paste backfill (CPB) material, the CPB with CEV added was prepared, and the specific heat capacity, thermal conductivity, and uniaxial compressive strength (UCS) of CPB with different cement−tailing ratios and CEV addition ratios were tested, the influence of the above variables on the thermal and mechanical properties of CPB was analyzed. The results show that the maximum encapsulation capacity of expanded vermiculite for CaCl2·6H2O is about 60%, and the melting and solidification enthalpies of CEV can reach 98.87 J/g and 97.56 J/g, respectively. For the CPB without CEV, the specific heat capacity, thermal conductivity, and UCS decrease with the decrease of cement−tailing ratio. For the CPB with CEV added, with the increase of CEV addition ratio, the specific heat capacity increases significantly, and the sensible heat storage capacity and latent heat storage capacity can be increased by at least 10.74% and 218.97% respectively after adding 12% CEV. However, the addition of CEV leads to the increase of pores, and the thermal conductivity and UCS both decrease with the increase of CEV addition. When cement–tailing ratio is 1:8 and 6%, 9%, and 12% of CEV are added, the 28-days UCS of CPB is less than 1 MPa. Considering the heat storage capacity and cost price of backfill, the recommended proportion scheme of CPB material presents cement−tailing ratio of 1:6 and 12% CEV, and the most recommended heat storage/release temperature cycle range of CPB with added CEV is from 20 to 40°C. This work can provide theoretical basis for the utilization of heat storage backfill in green mines.
2023, vol. 30, no. 2, pp.
260-270.
https://doi.org/10.1007/s12613-022-2471-y
Abstract:
With gradually diminishing Fe grade in tandem with the ever-increasing demand for high-grade iron ores, iron ore industries are now focusing on the beneficiation of low-grade iron ore fines, mainly considered waste. Besides, the scarcity of water at many of the mines’ sites and the new water conservation policies of the governments have necessitated research on suitable dry beneficiation routes. In this context, an effort has been made to evaluate the efficacy of a dry classification unit, such as the VSK separator, in upgrading the iron values of two low-grade Indian iron ore fines, named Sample 1 and Sample 2. The mineralogical studies, involving scanning electron microscopy and X-ray diffraction, suggest that Sample 1 is a low-grade blue dust sample (51.2wt% Fe) containing hematite and quartz as the major minerals, while Sample 2 (53.3wt% Fe) shows the presence of goethite in addition to hematite and quartz. The experiments, carried out using Box–Benkhen statistical design, indicate that blower speed, followed by feed rate, is the most influencing operating parameter in obtaining a good product in the VSK separator. At optimum levels of the operating factors, a fines product with ~55wt% Fe at a yield of ~40% can be obtained from Sample 1, while Sample 2 can be upgraded to ~56wt% Fe at a yield of ~85%. The results suggest that the VSK separator can be employed as an efficient intermediate unit operation in a processing circuit to upgrade the iron contents of iron ore fines.
With gradually diminishing Fe grade in tandem with the ever-increasing demand for high-grade iron ores, iron ore industries are now focusing on the beneficiation of low-grade iron ore fines, mainly considered waste. Besides, the scarcity of water at many of the mines’ sites and the new water conservation policies of the governments have necessitated research on suitable dry beneficiation routes. In this context, an effort has been made to evaluate the efficacy of a dry classification unit, such as the VSK separator, in upgrading the iron values of two low-grade Indian iron ore fines, named Sample 1 and Sample 2. The mineralogical studies, involving scanning electron microscopy and X-ray diffraction, suggest that Sample 1 is a low-grade blue dust sample (51.2wt% Fe) containing hematite and quartz as the major minerals, while Sample 2 (53.3wt% Fe) shows the presence of goethite in addition to hematite and quartz. The experiments, carried out using Box–Benkhen statistical design, indicate that blower speed, followed by feed rate, is the most influencing operating parameter in obtaining a good product in the VSK separator. At optimum levels of the operating factors, a fines product with ~55wt% Fe at a yield of ~40% can be obtained from Sample 1, while Sample 2 can be upgraded to ~56wt% Fe at a yield of ~85%. The results suggest that the VSK separator can be employed as an efficient intermediate unit operation in a processing circuit to upgrade the iron contents of iron ore fines.
2023, vol. 30, no. 2, pp.
271-282.
https://doi.org/10.1007/s12613-022-2505-5
Abstract:
The activation properties of ammonium oxalate on the flotation of pyrite and arsenopyrite in the lime system were studied in this work. Single mineral flotation tests showed that the ammonium oxalate strongly activated pyrite in high alkalinity and high Ca2+ system, whereas arsenopyrite was almost unaffected. In mineral mixtures tests, the recovery difference between pyrite and arsenopyrite after adding ammonium oxalate is more than 85%. After ammonium oxalate and ethyl xanthate treatment, the hydrophobicity of pyrite increased significantly, and the contact angle increased from 66.62° to 75.15° and then to 81.21°. After ammonium oxalate treatment, the amount of ethyl xanthate adsorption on the pyrite surface significantly increased and was much greater than that on the arsenopyrite surface. Zeta potential measurements showed that after activation by ammonium oxalate, there was a shift in the zeta potential of pyrite to more negative values by adding xanthate. X-ray photoelectron spectroscopy test showed that after ammonium oxalate treatment, the O 1s content on the surface of pyrite decreased from 44.03% to 26.18%, and the S 2p content increased from 14.01% to 27.26%, which confirmed that the ammonium oxalate-treated pyrite surface was more hydrophobic than the untreated surface. Therefore, ammonium oxalate may be used as a selective activator of pyrite in the lime system, which achieves an efficient flotation separation of S–As sulfide ores under high alkalinity and high Ca2+ concentration conditions.
The activation properties of ammonium oxalate on the flotation of pyrite and arsenopyrite in the lime system were studied in this work. Single mineral flotation tests showed that the ammonium oxalate strongly activated pyrite in high alkalinity and high Ca2+ system, whereas arsenopyrite was almost unaffected. In mineral mixtures tests, the recovery difference between pyrite and arsenopyrite after adding ammonium oxalate is more than 85%. After ammonium oxalate and ethyl xanthate treatment, the hydrophobicity of pyrite increased significantly, and the contact angle increased from 66.62° to 75.15° and then to 81.21°. After ammonium oxalate treatment, the amount of ethyl xanthate adsorption on the pyrite surface significantly increased and was much greater than that on the arsenopyrite surface. Zeta potential measurements showed that after activation by ammonium oxalate, there was a shift in the zeta potential of pyrite to more negative values by adding xanthate. X-ray photoelectron spectroscopy test showed that after ammonium oxalate treatment, the O 1s content on the surface of pyrite decreased from 44.03% to 26.18%, and the S 2p content increased from 14.01% to 27.26%, which confirmed that the ammonium oxalate-treated pyrite surface was more hydrophobic than the untreated surface. Therefore, ammonium oxalate may be used as a selective activator of pyrite in the lime system, which achieves an efficient flotation separation of S–As sulfide ores under high alkalinity and high Ca2+ concentration conditions.
2023, vol. 30, no. 2, pp.
283-292.
https://doi.org/10.1007/s12613-021-2344-9
Abstract:
The recovery of vanadium (V) from stone coal by bioleaching is a promising method. The bioleaching experiments and the biosorption experiments were carried out, aiming to explore the adsorption characteristics of Bacillus mucilaginosus (B. mucilaginosus) on the surface of vanadium-bearing stone coal, and the related mechanisms have been investigated. After bioleaching at 30°C for 28 d, the cumulative leaching rate of V reached 60.2%. The biosorption of B. mucilaginosus on stone coal was affected by many factors. When the pH value of leaching system is 5.0, strong electrostatic attraction between bacteria and stone coal promoted biosorption. Bacteria in the logarithmic growth phase had mature and excellent biosorption properties. The initial bacterial concentration of 3.5 × 108 CFU/mL was conducive to adhesion, with 38.9% adsorption rate and 3.6 × 107 CFU/g adsorption quantity. The adsorption of B. mucilaginosus on the stone coal conformed to the Freundlich model and the pseudo-second-order kinetic model. Bacterial surface carried functional groups (–CH2, –CH3, –NH2, etc.), which were highly correlated with the adsorption behavior. In addition, biosorption changed the surface properties of stone coal, resulting in the isoelectric point (IEP) approaching the bacteria. The results could provide an effective reference for the adsorption laws of bacteria on minerals.
The recovery of vanadium (V) from stone coal by bioleaching is a promising method. The bioleaching experiments and the biosorption experiments were carried out, aiming to explore the adsorption characteristics of Bacillus mucilaginosus (B. mucilaginosus) on the surface of vanadium-bearing stone coal, and the related mechanisms have been investigated. After bioleaching at 30°C for 28 d, the cumulative leaching rate of V reached 60.2%. The biosorption of B. mucilaginosus on stone coal was affected by many factors. When the pH value of leaching system is 5.0, strong electrostatic attraction between bacteria and stone coal promoted biosorption. Bacteria in the logarithmic growth phase had mature and excellent biosorption properties. The initial bacterial concentration of 3.5 × 108 CFU/mL was conducive to adhesion, with 38.9% adsorption rate and 3.6 × 107 CFU/g adsorption quantity. The adsorption of B. mucilaginosus on the stone coal conformed to the Freundlich model and the pseudo-second-order kinetic model. Bacterial surface carried functional groups (–CH2, –CH3, –NH2, etc.), which were highly correlated with the adsorption behavior. In addition, biosorption changed the surface properties of stone coal, resulting in the isoelectric point (IEP) approaching the bacteria. The results could provide an effective reference for the adsorption laws of bacteria on minerals.
2023, vol. 30, no. 2, pp.
293-302.
https://doi.org/10.1007/s12613-022-2459-7
Abstract:
Microwave heating can rapidly and uniformly raise the temperature and accelerate the reaction rate. In this paper, microwave heating was used to improve the acid leaching, and the mechanism was investigated via microscopic morphology analysis and numerical simulation by COMSOL Multiphysics software. The effects of the microwave power, leaching temperature, CaF2 dosage, H2SO4 concentration, and leaching time on the vanadium recovery were investigated. A vanadium recovery of 80.66% is obtained at a microwave power of 550 W, leaching temperature of 95°C, CaF2 dosage of 5wt%, H2SO4 concentration of 20vol%, and leaching time of 2.5 h. Compared with conventional leaching technology, the vanadium recovery increases by 6.18%, and the leaching time shortens by 79.17%. More obvious pulverization of shale particles and delamination of mica minerals happen in the microwave-assisted leaching process. Numerical simulation results show that the temperature of vanadium shales increases with an increase in electric field (E-field). The distributions of E-field and temperature among vanadium shale particles are relatively uniform, except for the higher content at the contact position of the particles. The analysis results of scale-up experiments and leaching experiments indicate high-temperature hot spots in the process of microwave-assisted leaching, and the local high temperature destroys the mineral structure and accelerates the reaction rate.
Microwave heating can rapidly and uniformly raise the temperature and accelerate the reaction rate. In this paper, microwave heating was used to improve the acid leaching, and the mechanism was investigated via microscopic morphology analysis and numerical simulation by COMSOL Multiphysics software. The effects of the microwave power, leaching temperature, CaF2 dosage, H2SO4 concentration, and leaching time on the vanadium recovery were investigated. A vanadium recovery of 80.66% is obtained at a microwave power of 550 W, leaching temperature of 95°C, CaF2 dosage of 5wt%, H2SO4 concentration of 20vol%, and leaching time of 2.5 h. Compared with conventional leaching technology, the vanadium recovery increases by 6.18%, and the leaching time shortens by 79.17%. More obvious pulverization of shale particles and delamination of mica minerals happen in the microwave-assisted leaching process. Numerical simulation results show that the temperature of vanadium shales increases with an increase in electric field (E-field). The distributions of E-field and temperature among vanadium shale particles are relatively uniform, except for the higher content at the contact position of the particles. The analysis results of scale-up experiments and leaching experiments indicate high-temperature hot spots in the process of microwave-assisted leaching, and the local high temperature destroys the mineral structure and accelerates the reaction rate.
2023, vol. 30, no. 2, pp.
303-313.
https://doi.org/10.1007/s12613-022-2484-6
Abstract:
In order to study the sintering characteristics of Ca-rich iron ore, chemical analysis, laser diffraction, scanning electron microscopy, XRD-Rietveld method, and micro-sintering were used to analyze the mineralogical properties and sintering pot tests were used to study the sintering behavior. In addition, a grey correlation mathematical model was used to calculate and compare the comprehensive sintering performance under different calcium-rich iron ore contents. The results demonstrate that the Ca-rich iron ore has coarse grain size and strong self-fusing characteristics with Ca element in the form of calcite (CaCO3) and the liquid phase produced by the self-fusing of the calcium-rich iron ore is well crystallized. Its application with a 20wt% content in sintering improves sinter productivity, reduces fuel consumption, enhances reduction index, and improves gas permeability in blast furnace by 0.45 t/(m2·h), 6.11 kg/t, 6.17%, and 65.39 kPa·°C, respectively. The Ca-rich iron ore sintering can improve the calorific value of sintering flue gas compared with magnetite sintering, which is conducive to recovering heat for secondary use. As the content of the Ca-rich iron ore increases, sinter agglomeration shifts from localized liquid-phase bonding to a combination of localized liquid-phase bonding and iron oxide crystal connection. Based on an examination of the greater weight value of productivity with grey correlation analysis, the Ca-rich iron ore is beneficial for the comprehensive index of sintering in the range of 0–20wt% content. Therefore, it may be used in sintering with magnetite concentrates as the major ore species.
In order to study the sintering characteristics of Ca-rich iron ore, chemical analysis, laser diffraction, scanning electron microscopy, XRD-Rietveld method, and micro-sintering were used to analyze the mineralogical properties and sintering pot tests were used to study the sintering behavior. In addition, a grey correlation mathematical model was used to calculate and compare the comprehensive sintering performance under different calcium-rich iron ore contents. The results demonstrate that the Ca-rich iron ore has coarse grain size and strong self-fusing characteristics with Ca element in the form of calcite (CaCO3) and the liquid phase produced by the self-fusing of the calcium-rich iron ore is well crystallized. Its application with a 20wt% content in sintering improves sinter productivity, reduces fuel consumption, enhances reduction index, and improves gas permeability in blast furnace by 0.45 t/(m2·h), 6.11 kg/t, 6.17%, and 65.39 kPa·°C, respectively. The Ca-rich iron ore sintering can improve the calorific value of sintering flue gas compared with magnetite sintering, which is conducive to recovering heat for secondary use. As the content of the Ca-rich iron ore increases, sinter agglomeration shifts from localized liquid-phase bonding to a combination of localized liquid-phase bonding and iron oxide crystal connection. Based on an examination of the greater weight value of productivity with grey correlation analysis, the Ca-rich iron ore is beneficial for the comprehensive index of sintering in the range of 0–20wt% content. Therefore, it may be used in sintering with magnetite concentrates as the major ore species.
2023, vol. 30, no. 2, pp.
314-323.
https://doi.org/10.1007/s12613-022-2432-5
Abstract:
Combustion performance of pulverized coal (PC) in blast furnace (BF) process is regarded as a criteria parameter to assess the proper injection dosage of PC. In this paper, effects of two kinds of additives, Fe2O3 and CaO, on PC combustion were studied using the thermo-gravimetric method. The results demonstrate that both the Fe2O3 and CaO can promote combustion performance index of PC including ignition index (Ci), burnout index (Db), as well as comprehensive combustibility index (Sn). The Sn increases from 1.37 × 10−6 to 2.16 × 10−6 %2·min−2·°C−3 as the Fe2O3 proportion increases from 0 to 5.0wt%. Additionally, the combustion kinetics of PC was clarified using the Coats-Redfern method. The results show that the activation energy (E) of PC combustion decreases after adding the above additives. For instance, the E decreases from 56.54 to 35.75 kJ/mol when the Fe2O3 proportion increases from 0 to 5.0wt%, which supports the improved combustion performance. Moreover, it is uneconomic to utilize pure Fe2O3 and CaO in production. Based on economy analysis, we selected the iron-bearing dust (IBD) which contains much Fe2O3 and CaO component to investigate, and got the same effects. Therefore, the IBD is a potential option for catalytic PC combustion in BF process.
Combustion performance of pulverized coal (PC) in blast furnace (BF) process is regarded as a criteria parameter to assess the proper injection dosage of PC. In this paper, effects of two kinds of additives, Fe2O3 and CaO, on PC combustion were studied using the thermo-gravimetric method. The results demonstrate that both the Fe2O3 and CaO can promote combustion performance index of PC including ignition index (Ci), burnout index (Db), as well as comprehensive combustibility index (Sn). The Sn increases from 1.37 × 10−6 to 2.16 × 10−6 %2·min−2·°C−3 as the Fe2O3 proportion increases from 0 to 5.0wt%. Additionally, the combustion kinetics of PC was clarified using the Coats-Redfern method. The results show that the activation energy (E) of PC combustion decreases after adding the above additives. For instance, the E decreases from 56.54 to 35.75 kJ/mol when the Fe2O3 proportion increases from 0 to 5.0wt%, which supports the improved combustion performance. Moreover, it is uneconomic to utilize pure Fe2O3 and CaO in production. Based on economy analysis, we selected the iron-bearing dust (IBD) which contains much Fe2O3 and CaO component to investigate, and got the same effects. Therefore, the IBD is a potential option for catalytic PC combustion in BF process.
2023, vol. 30, no. 2, pp.
324-334.
https://doi.org/10.1007/s12613-021-2355-6
Abstract:
The hot deformation behavior of Mn18Cr18N and Mn18Cr18N+Ce high nitrogen austenitic stainless steels at 1173–1473 K and 0.01–1 s–1 were investigated by thermal compression tests. The influence mechanism of Ce on the hot deformation behavior was analyzed by Ce-containing inclusions and segregation of Ce. The results show that after the addition of Ce, large, angular, hard, and brittle inclusions (TiN–Al2O3, TiN, and Al2O3) can be modified to fine and dispersed Ce-containing inclusions (Ce–Al–O–S and TiN–Ce–Al–O–S). During the solidification, Ce-containing inclusions can be used as heterogeneous nucleation particles to refine as-cast grains. During the hot deformation, Ce-containing inclusions can pin dislocation movement and grain boundary migration, induce dynamic recrystallization (DRX) nucleation, and avoid the formation and propagation of micro cracks and gaps. In addition, during the solidification, Ce atoms enrich at the front of solid–liquid interface, resulting in composition supercooling and refining the secondary dendrites. Similarly, during the hot deformation, Ce atoms tend to segregate at the boundaries of DRX grains, inhibiting the growth of grains. Under the synergistic effect of Ce-containing inclusions and Ce segregation, although the hot deformation resistance and hot deformation activation energy are improved, DRX is more likely to occur and the size of DRX grains is significantly refined, and the problem of hot deformation cracking can be alleviated. Finally, the microhardness of the samples was measured. The results show that compared with as-cast samples, the microhardness of hot-deformed samples increases significantly, and with the increase of DRX degree, the microhardness decreases continuously. In addition, Ce can affect the microhardness of Mn18Cr18N steel by affecting as-cast and hot deformation microstructures.
The hot deformation behavior of Mn18Cr18N and Mn18Cr18N+Ce high nitrogen austenitic stainless steels at 1173–1473 K and 0.01–1 s–1 were investigated by thermal compression tests. The influence mechanism of Ce on the hot deformation behavior was analyzed by Ce-containing inclusions and segregation of Ce. The results show that after the addition of Ce, large, angular, hard, and brittle inclusions (TiN–Al2O3, TiN, and Al2O3) can be modified to fine and dispersed Ce-containing inclusions (Ce–Al–O–S and TiN–Ce–Al–O–S). During the solidification, Ce-containing inclusions can be used as heterogeneous nucleation particles to refine as-cast grains. During the hot deformation, Ce-containing inclusions can pin dislocation movement and grain boundary migration, induce dynamic recrystallization (DRX) nucleation, and avoid the formation and propagation of micro cracks and gaps. In addition, during the solidification, Ce atoms enrich at the front of solid–liquid interface, resulting in composition supercooling and refining the secondary dendrites. Similarly, during the hot deformation, Ce atoms tend to segregate at the boundaries of DRX grains, inhibiting the growth of grains. Under the synergistic effect of Ce-containing inclusions and Ce segregation, although the hot deformation resistance and hot deformation activation energy are improved, DRX is more likely to occur and the size of DRX grains is significantly refined, and the problem of hot deformation cracking can be alleviated. Finally, the microhardness of the samples was measured. The results show that compared with as-cast samples, the microhardness of hot-deformed samples increases significantly, and with the increase of DRX degree, the microhardness decreases continuously. In addition, Ce can affect the microhardness of Mn18Cr18N steel by affecting as-cast and hot deformation microstructures.
2023, vol. 30, no. 2, pp.
335-344.
https://doi.org/10.1007/s12613-021-2409-9
Abstract:
The composition control of molten steel is one of the main functions in the ladle furnace (LF) refining process. In this study, a feasible model was established to predict the alloying element yield using principal component analysis (PCA) and deep neural network (DNN). The PCA was used to eliminate collinearity and reduce the dimension of the input variables, and then the data processed by PCA were used to establish the DNN model. The prediction hit ratios for the Si element yield in the error ranges of ±1%, ±3%, and ±5% are 54.0%, 93.8%, and 98.8%, respectively, whereas those of the Mn element yield in the error ranges of ±1%, ±2%, and ±3% are 77.0%, 96.3%, and 99.5%, respectively, in the PCA–DNN model. The results demonstrate that the PCA–DNN model performs better than the known models, such as the reference heat method, multiple linear regression, modified backpropagation, and DNN model. Meanwhile, the accurate prediction of the alloying element yield can greatly contribute to realizing a “narrow window” control of composition in molten steel. The construction of the prediction model for the element yield can also provide a reference for the development of an alloying control model in LF intelligent refining in the modern iron and steel industry.
The composition control of molten steel is one of the main functions in the ladle furnace (LF) refining process. In this study, a feasible model was established to predict the alloying element yield using principal component analysis (PCA) and deep neural network (DNN). The PCA was used to eliminate collinearity and reduce the dimension of the input variables, and then the data processed by PCA were used to establish the DNN model. The prediction hit ratios for the Si element yield in the error ranges of ±1%, ±3%, and ±5% are 54.0%, 93.8%, and 98.8%, respectively, whereas those of the Mn element yield in the error ranges of ±1%, ±2%, and ±3% are 77.0%, 96.3%, and 99.5%, respectively, in the PCA–DNN model. The results demonstrate that the PCA–DNN model performs better than the known models, such as the reference heat method, multiple linear regression, modified backpropagation, and DNN model. Meanwhile, the accurate prediction of the alloying element yield can greatly contribute to realizing a “narrow window” control of composition in molten steel. The construction of the prediction model for the element yield can also provide a reference for the development of an alloying control model in LF intelligent refining in the modern iron and steel industry.
2023, vol. 30, no. 2, pp.
345-353.
https://doi.org/10.1007/s12613-021-2347-6
Abstract:
The dissolution kinetics of Al2O3 in CaO–Al2O3–SiO2 slags was studied using a high-temperature confocal scanning laser microscope at 1773 to 1873 K. The results show that the controlling step during the Al2O3 dissolution was the diffusion in molten slag. It was found that the dissolution curves of Al2O3 particles were hardly agreed with the traditional boundary layer diffusion model with the increase of the CaO/Al2O3 ratio of slag. A modified diffusion equation considering slag viscosity was developed to study the dissolution mechanism of Al2O3 in slag. Diffusion coefficients of Al2O3 in slag were calculated as 2.8 × 10−10 to 4.1 × 10−10 m2/s at the temperature of 1773–1873 K. The dissolution rate of Al2O3 increased with higher temperature, CaO/Al2O3, and particle size. A new model was shown to be\begin{document}${v}_{{\mathrm{A}\mathrm{l}}_{2}{\mathrm{O}}_{3}}=0.16\times {r}_{0}^{1.58}\times $\end{document} ![]()
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\begin{document}$ {x}^{3.52}\times {\left(T-{T}_{\mathrm{m}\mathrm{p}}\right)}^{1.11} $\end{document} ![]()
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\begin{document}$ {v}_{{\mathrm{A}\mathrm{l}}_{2}{\mathrm{O}}_{3}} $\end{document} ![]()
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The dissolution kinetics of Al2O3 in CaO–Al2O3–SiO2 slags was studied using a high-temperature confocal scanning laser microscope at 1773 to 1873 K. The results show that the controlling step during the Al2O3 dissolution was the diffusion in molten slag. It was found that the dissolution curves of Al2O3 particles were hardly agreed with the traditional boundary layer diffusion model with the increase of the CaO/Al2O3 ratio of slag. A modified diffusion equation considering slag viscosity was developed to study the dissolution mechanism of Al2O3 in slag. Diffusion coefficients of Al2O3 in slag were calculated as 2.8 × 10−10 to 4.1 × 10−10 m2/s at the temperature of 1773–1873 K. The dissolution rate of Al2O3 increased with higher temperature, CaO/Al2O3, and particle size. A new model was shown to be
2023, vol. 30, no. 2, pp.
354-364.
https://doi.org/10.1007/s12613-022-2548-7
Abstract:
First, strip cast samples of high strength microalloyed steel with sub-rapid solidification characteristics were prepared by simulated strip casting technique. Next, the isothermal growth of austenite grain during the reheating treatment of strip casts was observed in situ through confocal laser scanning microscope (CLSM). The results indicated that the time exponent of grains growth suddenly rise when the isothermal temperature higher than 1000°C. And the activation energy for austenite grain growth were calculated to be 538.0 kJ/mol in the high temperature region (above 1000°C) and 693.2 kJ/mol in the low temperature region (below 1000°C), respectively. Then, the kinetics model of austenite isothermal growth was established, which can predict the austenite grain size during isothermal hold very well. Besides, high density of second phase particles with small size was found during the isothermal hold at the low temperature region, leading to the refinement of austenite grain. After isothermal hold at different temperature for 1800 s, the bainite transformation in microalloyed steel strip was also observed in situ during the continuous cooling process. And growth rates of bainite plates with different nucleation positions and different prior austenite grain size (PAGS) were calculated. It was indicated that the growth rate of the bainite plate is not only related to the nucleation position but also to the PAGS.
First, strip cast samples of high strength microalloyed steel with sub-rapid solidification characteristics were prepared by simulated strip casting technique. Next, the isothermal growth of austenite grain during the reheating treatment of strip casts was observed in situ through confocal laser scanning microscope (CLSM). The results indicated that the time exponent of grains growth suddenly rise when the isothermal temperature higher than 1000°C. And the activation energy for austenite grain growth were calculated to be 538.0 kJ/mol in the high temperature region (above 1000°C) and 693.2 kJ/mol in the low temperature region (below 1000°C), respectively. Then, the kinetics model of austenite isothermal growth was established, which can predict the austenite grain size during isothermal hold very well. Besides, high density of second phase particles with small size was found during the isothermal hold at the low temperature region, leading to the refinement of austenite grain. After isothermal hold at different temperature for 1800 s, the bainite transformation in microalloyed steel strip was also observed in situ during the continuous cooling process. And growth rates of bainite plates with different nucleation positions and different prior austenite grain size (PAGS) were calculated. It was indicated that the growth rate of the bainite plate is not only related to the nucleation position but also to the PAGS.
2023, vol. 30, no. 2, pp.
365-377.
https://doi.org/10.1007/s12613-022-2504-6
Abstract:
To remove the key impurity elements, P and B, from primary Si simultaneously, Sr and Zr co-addition to Al–Si alloy systems during solvent refining has been investigated. Sr reacts with Al, Si, and P in the melt to form a P-containing Al2Si2Sr phase and Zr reacts with B to form a ZrB2 phase. In the Al–Si–Sr–Zr system, high removal fractions of P and B in the primary Si, with 84.8%–98.4% and 90.7%–96.7%, respectively, are achieved at the same time, respectively. The best removal effect is obtained in the sample with the addition of Sr-32000+Zr-3000 μg·kg–1, and the removal fractions of P and B in the purified Si reach 98.4% and 96.1%. Compared with the Sr/Zr single-addition, the removal effects of Sr and Zr co-addition on P and B do not show a significant downward trend, indicating that the nucleation and growth of the B/P-containing impurity phases are mutually independent. Finally, an evolution model is proposed to describe the nucleation and the growth stages of Sr/Zr-containing compound phases, which reveals the interaction between the impurity phases and the primary Si.
To remove the key impurity elements, P and B, from primary Si simultaneously, Sr and Zr co-addition to Al–Si alloy systems during solvent refining has been investigated. Sr reacts with Al, Si, and P in the melt to form a P-containing Al2Si2Sr phase and Zr reacts with B to form a ZrB2 phase. In the Al–Si–Sr–Zr system, high removal fractions of P and B in the primary Si, with 84.8%–98.4% and 90.7%–96.7%, respectively, are achieved at the same time, respectively. The best removal effect is obtained in the sample with the addition of Sr-32000+Zr-3000 μg·kg–1, and the removal fractions of P and B in the purified Si reach 98.4% and 96.1%. Compared with the Sr/Zr single-addition, the removal effects of Sr and Zr co-addition on P and B do not show a significant downward trend, indicating that the nucleation and growth of the B/P-containing impurity phases are mutually independent. Finally, an evolution model is proposed to describe the nucleation and the growth stages of Sr/Zr-containing compound phases, which reveals the interaction between the impurity phases and the primary Si.
2023, vol. 30, no. 2, pp.
378-387.
https://doi.org/10.1007/s12613-022-2553-x
Abstract:
Recovering the iron (Fe) and phosphorus (P) contained in steelmaking slags not only reduces the environmental burden caused by the accumulated slag, but also is the way to develop a circular economy and achieve sustainable development in the steel industry. We had previously found the possibility of recovering Fe and P resources, i.e., magnetite (Fe3O4) and calcium phosphate (Ca10P6O25), contained in steelmaking slags by adjusting oxygen partial pressure and adding modifier B2O3. As a fundamental study for efficiently recovering Fe and P from steelmaking slag, in this study, the crystallization behavior of the CaO–SiO2–FeO–P2O5–B2O3 melt has been observed in situ, using a confocal scanning laser microscope (CLSM). The kinetics of nucleation and growth of Fe- and P-rich phases have been calculated using a classical crystallization kinetic theory. During cooling, a Fe3O4 phase with faceted morphology was observed as the 1st precipitated phase in the isothermal interval of 1300–1150°C, while Ca10P6O25, with rod-shaped morphology, was found to be the 2nd phase to precipitate in the interval of 1150–1000°C. The crystallization abilities of Fe3O4 and Ca10P6O25 phases in the CaO–SiO2–FeO–P2O5–B2O3 melt were quantified with the index of (TU − TI)/TI (where TI represents the peak temperature of the nucleation rate and TU stands for that of growth rate), and the crystallization ability of Fe3O4 was found to be larger than that of Ca10P6O25 phase. The range of crystallization temperature for Fe3O4 and Ca10P6O25 phases was optimized subsequently. The Fe3O4 and Ca10P6O25 phases are the potential sources for ferrous feedstock and phosphate fertilizer, respectively.
Recovering the iron (Fe) and phosphorus (P) contained in steelmaking slags not only reduces the environmental burden caused by the accumulated slag, but also is the way to develop a circular economy and achieve sustainable development in the steel industry. We had previously found the possibility of recovering Fe and P resources, i.e., magnetite (Fe3O4) and calcium phosphate (Ca10P6O25), contained in steelmaking slags by adjusting oxygen partial pressure and adding modifier B2O3. As a fundamental study for efficiently recovering Fe and P from steelmaking slag, in this study, the crystallization behavior of the CaO–SiO2–FeO–P2O5–B2O3 melt has been observed in situ, using a confocal scanning laser microscope (CLSM). The kinetics of nucleation and growth of Fe- and P-rich phases have been calculated using a classical crystallization kinetic theory. During cooling, a Fe3O4 phase with faceted morphology was observed as the 1st precipitated phase in the isothermal interval of 1300–1150°C, while Ca10P6O25, with rod-shaped morphology, was found to be the 2nd phase to precipitate in the interval of 1150–1000°C. The crystallization abilities of Fe3O4 and Ca10P6O25 phases in the CaO–SiO2–FeO–P2O5–B2O3 melt were quantified with the index of (TU − TI)/TI (where TI represents the peak temperature of the nucleation rate and TU stands for that of growth rate), and the crystallization ability of Fe3O4 was found to be larger than that of Ca10P6O25 phase. The range of crystallization temperature for Fe3O4 and Ca10P6O25 phases was optimized subsequently. The Fe3O4 and Ca10P6O25 phases are the potential sources for ferrous feedstock and phosphate fertilizer, respectively.
2023, vol. 30, no. 2, pp.
388-400.
https://doi.org/10.1007/s12613-022-2475-7
Abstract:
Decarbonization is a critical issue for peaking CO2 emissions of energy-intensive industries, such as the iron and steel industry. The decarbonization options of China’s ironmaking and steelmaking sector were discussed based on a systematic three-dimensional low-carbon analysis from the aspects of resource utilization (Y), energy utilization (Q), and energy cleanliness which is evaluated by a process general emission factor (PGEF) on all the related processes, including the current blast furnace (BF)–basic oxygen furnace (BOF) integrated process and the specific sub-processes, as well as the electric arc furnace (EAF) process, typical direct reduction (DR) process, and smelting reduction (SR) process. The study indicates that the three-dimensional aspects, particularly the energy structure, should be comprehensively considered to quantitatively evaluate the decarbonization road map based on novel technologies or processes. Promoting scrap utilization (improvement of Y) and the substitution of carbon-based energy (improvement of PGEF) in particular is critical. In terms of process scale, promoting the development of the scrap-based EAF or DR–EAF process is highly encouraged because of their lower PGEF. The three-dimensional method is expected to extend to other processes or industries, such as the cement production and thermal electricity generation industries.
Decarbonization is a critical issue for peaking CO2 emissions of energy-intensive industries, such as the iron and steel industry. The decarbonization options of China’s ironmaking and steelmaking sector were discussed based on a systematic three-dimensional low-carbon analysis from the aspects of resource utilization (Y), energy utilization (Q), and energy cleanliness which is evaluated by a process general emission factor (PGEF) on all the related processes, including the current blast furnace (BF)–basic oxygen furnace (BOF) integrated process and the specific sub-processes, as well as the electric arc furnace (EAF) process, typical direct reduction (DR) process, and smelting reduction (SR) process. The study indicates that the three-dimensional aspects, particularly the energy structure, should be comprehensively considered to quantitatively evaluate the decarbonization road map based on novel technologies or processes. Promoting scrap utilization (improvement of Y) and the substitution of carbon-based energy (improvement of PGEF) in particular is critical. In terms of process scale, promoting the development of the scrap-based EAF or DR–EAF process is highly encouraged because of their lower PGEF. The three-dimensional method is expected to extend to other processes or industries, such as the cement production and thermal electricity generation industries.
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