Iron ore sintering is a pre-treatment technology by which orefines are converted into porous and permeable sin-ters,which are the used in blast furnaces.This process can be adversely affected by air leakage phenomena ...Iron ore sintering is a pre-treatment technology by which orefines are converted into porous and permeable sin-ters,which are the used in blast furnaces.This process can be adversely affected by air leakage phenomena of various types.As experimental measurements are relatively difficult and often scarcely reliable,here a theoretical model based on typicalfluid-dynamic concepts and relationships is elaborated.Through the analysis of two extreme cases,namely,those in which leakage is due to a small hole or a full rupture,a generalized hole-bed mod-el is introduced,which for thefirst time also includes a complete bed permeability equation and can deal with different leakage position conditions.The results show that the model can evaluate the influence of leakage on the system at one time and be used to calculate theflowrate and pressure drop.Notably,the obtained results are within a 15%deviation with respect to available experiment values,used for comparison.展开更多
In order to quantitatively predict the behavior of the material in the packed bed, a single particle model is developed to describe the combustion and sintering process inside an individual particle composed of multip...In order to quantitatively predict the behavior of the material in the packed bed, a single particle model is developed to describe the combustion and sintering process inside an individual particle composed of multiple solid material fines, including iron ore, coke and limestone, and is applied to the combustion modeling of an iron ore sintering. Byanalyzing three typical fuel distribution cases using the developed single particle combustion model, the effects of temperature and oxygen concentration gradient inside the particle on heat and mass transfer and the combustion behavior of the iron ore sintering process areinvestigated. Considering the various combustion rates which are highly dependent on the fuel distribution methods, correction factor for single particle model is also introduced and systematically analyzed. The aim of this research is to supplement particle technology to conventional approach and it is found that the oxygen concentration gradient inside the particle is significantly affected from the mixing method thereby changing the completion times of sintering process.展开更多
In this study, powder metallurgy methods were used to fabricate Mg-7.5Li-3Al-Zn alloys from repowdered extruded alloys. Extruded alloys were powdered using ultrasonic atomization, and then laser powder bed fusion(LPBF...In this study, powder metallurgy methods were used to fabricate Mg-7.5Li-3Al-Zn alloys from repowdered extruded alloys. Extruded alloys were powdered using ultrasonic atomization, and then laser powder bed fusion(LPBF) and pulse plasma sintering(PPS) were used to consolidate the bulk materials. A comparison of the properties of the fabricated alloys with those of a conventionally extruded one was carried out using methods that characterized the microstructure and corrosion resistance. When compared to their conventionally extruded counterpart, LPBF and PPS materials exhibited refined microstructures with low enrichment in Al Li and coarse Al, Zn, Mn precipitates. The main drawback of the LPBF alloy, printed for the needs of this study, was its porosity, which had a negative effect on its corrosion. The presence of unrecrystallized particle boundaries in the PPS alloy was also unbeneficial with regard to corrosion. The advantage of the LPBF and PPS processes was the ability to change the proportion of α(Mg) to β(Li), which when the complete consolidation of the material is achievable, may increase the corrosion resistance of dual-structured Mg-Li alloys. The results show that powder metallurgy routes have a wide potential to be used for the manufacture of Mg-Li based alloys.展开更多
Super-high bed sintering process is an important development direction of iron ore sintering for its lower emission and higher yield.However,there is a lack of deep understanding of the uneven quality of super-high be...Super-high bed sintering process is an important development direction of iron ore sintering for its lower emission and higher yield.However,there is a lack of deep understanding of the uneven quality of super-high bed sintering products,and the deterioration of reduction disintegration performance,the thickening of hearth layer and the reduction in energy-saving effect are perplexing enterprises and researchers.To ascertain the problems of super-high bed sintering,ten sintering machines with the areas of 265,280,360,550 and 660 m^(2)and bed depth above 900 mm were sampled and analyzed.The results showed that problems were mainly shown in the unevenness of chemical composition,macrostructure,mechanical strength and metallurgical performance.The chemical composition exhibits severe segregation in both horizontal and vertical directions,with basicity segregation reaching as high as 0.81.The uneven macrostructure of sinter is reflected in a 10%difference in porosity and mechanical strength increase in 16%–19%along the vertical direction.The reducibility and reduction disintegration performance gradually deteriorate along the bed depth,with a difference of 10.5%in reducibility and 7.3%in RDI−0.5 mm(reduction disintegration index of sinter with size smaller than 0.5 mm).展开更多
Horizontal segregation has been a constraint to the development and application of super-high bed sintering.To eliminate the horizontal segregation of super-high bed sintering,several typical sintering machines were s...Horizontal segregation has been a constraint to the development and application of super-high bed sintering.To eliminate the horizontal segregation of super-high bed sintering,several typical sintering machines were sampled and analyzed,and theoretical calculation was made to compare the bed depth and their differences in different areas within the mixture bin.Then,solutions were proposed and applied to a 265 m^(2) sintering machine.The results showed that the horizontal seg-regation of the 265 m^(2) sintering machine was dominated by particles larger than 8 mm with horizontal segregation degree of 0.48,while 360 and 550 m^(2) sintering machines were affected by 5-8 mm and 1-3 mm particles with horizontal segregation degree of 0.27 and 0.31,respectively.Causes analysis indicated the different segregation distribution results from the matching of the bed depth of each area within the mixture bin.Finally,the horizontal segregation degree not larger than 0.06 was achieved by optimizing the time parameters and the division of three zones on the 265 m^(2) sintering machine.展开更多
Polymers are widely used materials in aerospace,automotive,construction,medical devices and pharmaceuticals.Polymers are being promoted rapidly due to their ease of manufacturing and improved material properties.Resea...Polymers are widely used materials in aerospace,automotive,construction,medical devices and pharmaceuticals.Polymers are being promoted rapidly due to their ease of manufacturing and improved material properties.Research on polymer processing technology should be paid more attention to due to the increasing demand for polymer applications.Selective laser sintering(SLS)uses a laser to sinter powdered materials(typical polyamide),and it is one of the critical additive manufacturing(AM)techniques of polymer.It irradiates the laser beam on the defined areas by a computer-aided design three-dimensional(3D)model to bind the material together to create a designed 3D solid structure.SLS has many advantages,such as no support structures and excellent mechanical properties resembling injection moulded parts compared with other AM methods.However,the ability of SLS to process polymers is still affected by some defects,such as the porous structure and limited available types of SLS polymers.Therefore,this article reviews the current state-of-the-art SLS of polymers,including the fundamental principles in this technique,the SLS developments of typical polymers,and the essential process parameters in SLS.Furthermore,the applications of SLS are focused,and the conclusions and perspectives are discussed.展开更多
A new gas clean-up process called 'integrated sintered metal screen moving granular bed' (ISMSMGB) for the integrated gasification combined cycle (IGCC) and pressured fluidized bed combustion (PFBC) was develo...A new gas clean-up process called 'integrated sintered metal screen moving granular bed' (ISMSMGB) for the integrated gasification combined cycle (IGCC) and pressured fluidized bed combustion (PFBC) was developed on the basis of a sintered metal candle filter and a cross-flow moving granular bed filter. This is a combination of the surface and deep bed filtering processes. A set of facilities was established and a series of cold model tests were carried out. The dust removal efficiency and the pressure drop of the filter were measured and analyzed. The results show that this process features the advantages of the moving bed for high capacity as well as high inlet dust load and the surface filter for high efficiency. Meanwhile, the granules moving downward cleans the cake on the screen surface, so that the system is operated at steady state.展开更多
The sinter quality is important for its performance in a blast furnace,and optimizing ore matching is a main way to ensure the quality and yield of sinter ore and to reduce the cost of ore matching.The research on opt...The sinter quality is important for its performance in a blast furnace,and optimizing ore matching is a main way to ensure the quality and yield of sinter ore and to reduce the cost of ore matching.The research on optimizing ore matching for a 550 m2sintering machine in Shougang Jingtang was carried out in this paper. Firstly,based on the condition of iron ore resourse in Shougang,sintering properties of various ores,especially the high temperature properties were researched,and basic structure of ore matching was determined according to the mutual complementary properties of assimilation and liquid phase fluidity among Australia ore,Brazilian ore and domestic concentrates,that was Australian ore(50%-60%) + Brazilian ore(40%-30%) + domestic concentrates(about 10%).Secondly,9 groups of ore matching schemes were designed and sintering pot tests were carried out,and then the starting scheme of the 550 m2sintering machine was obtained:ore from southern Brazil (20%) +ore from northern Brazil(10%) + semi-limonite(20%) + limonite ore(35%) + domestic concentrates (15%).Thirdly,experiment of optimizing parameters of optimizing basicity,lime ratio,water addition and bed depth were carried out,and 9 groups of ore matching schemes were designed.The results showed that parameters fit for Jingtang currently are as follows:binary basicity is 1.9 - 1.95,lime ratio and water addition is 5%and 7.0% respectively;sintering bed should increase to 800 mm gradually.At last,Jingtang sintering plant was put into production successfully and yields stably,with the bed depth of 800 mm and advanced sintering indexes.展开更多
High speed sintering,a new powder-bed fusion additive manufacturing technology,utilizes infrared lights(IR)to intensely heat and melt polymer powders.The presence of defects such as porosity,which is associated with p...High speed sintering,a new powder-bed fusion additive manufacturing technology,utilizes infrared lights(IR)to intensely heat and melt polymer powders.The presence of defects such as porosity,which is associated with particle coalescence,is highly dependdent on the level of energy input.This study investigate the influcence of energy input on porosity and its subsequent effects on the mechanical properties and microstructures of PEBA parts.The parts were manufactured with a variety of lamp powers,resulting in a range of energy input levels spanning from low to high.Subsequebtly,they underwent testing using Archimedes’method,followed by tensile testing.The porosity,mechanical characteristics,and energy input exhibit a strong correlation;inadequate energy input was the primary cause of pore formation.Using the reduced IR light power resulted in the following outcomes:porosity,ultimate tensile strength,and elongation of 1.37%,7.6 MPa,and 194.2%,respectively.When the energy input was further increased,the porosity was reduced to as low as 0.05%and the ultimate tensile strength and elongation were increased to their peak values of 233.8%and 9.1 MPa,respectively.展开更多
To better understand the evolution characteristics of bed porous structure during iron ore sintering,X-ray computed tomography scanning technology was used to analyze the pore parameters in different areas of the sint...To better understand the evolution characteristics of bed porous structure during iron ore sintering,X-ray computed tomography scanning technology was used to analyze the pore parameters in different areas of the sintering bed.A pore skeleton structure model was established to study the characteristics of the airflow channels in different zones.The absolute permeability of different areas was calculated through simulation,and the corresponding streamline and pressure drop distribution were analyzed.The results show that the porosity of raw material zone,high-temperature zone,and sintered zone increases gradually,which are 37.69%,46.41%,and 55.57%,respectively.The absolute permeability calculation results of the raw material zone and sintered zones are 792.49μm^(2) and 20560.80μm^(2),while the tortuosity is 1.77 and 1.45,respectively.Compared with the raw material zone,the flow streamline in the sintered zone is thicker and denser,the airflow resistance and the pressure drop are minor.展开更多
文摘Iron ore sintering is a pre-treatment technology by which orefines are converted into porous and permeable sin-ters,which are the used in blast furnaces.This process can be adversely affected by air leakage phenomena of various types.As experimental measurements are relatively difficult and often scarcely reliable,here a theoretical model based on typicalfluid-dynamic concepts and relationships is elaborated.Through the analysis of two extreme cases,namely,those in which leakage is due to a small hole or a full rupture,a generalized hole-bed mod-el is introduced,which for thefirst time also includes a complete bed permeability equation and can deal with different leakage position conditions.The results show that the model can evaluate the influence of leakage on the system at one time and be used to calculate theflowrate and pressure drop.Notably,the obtained results are within a 15%deviation with respect to available experiment values,used for comparison.
文摘In order to quantitatively predict the behavior of the material in the packed bed, a single particle model is developed to describe the combustion and sintering process inside an individual particle composed of multiple solid material fines, including iron ore, coke and limestone, and is applied to the combustion modeling of an iron ore sintering. Byanalyzing three typical fuel distribution cases using the developed single particle combustion model, the effects of temperature and oxygen concentration gradient inside the particle on heat and mass transfer and the combustion behavior of the iron ore sintering process areinvestigated. Considering the various combustion rates which are highly dependent on the fuel distribution methods, correction factor for single particle model is also introduced and systematically analyzed. The aim of this research is to supplement particle technology to conventional approach and it is found that the oxygen concentration gradient inside the particle is significantly affected from the mixing method thereby changing the completion times of sintering process.
文摘In this study, powder metallurgy methods were used to fabricate Mg-7.5Li-3Al-Zn alloys from repowdered extruded alloys. Extruded alloys were powdered using ultrasonic atomization, and then laser powder bed fusion(LPBF) and pulse plasma sintering(PPS) were used to consolidate the bulk materials. A comparison of the properties of the fabricated alloys with those of a conventionally extruded one was carried out using methods that characterized the microstructure and corrosion resistance. When compared to their conventionally extruded counterpart, LPBF and PPS materials exhibited refined microstructures with low enrichment in Al Li and coarse Al, Zn, Mn precipitates. The main drawback of the LPBF alloy, printed for the needs of this study, was its porosity, which had a negative effect on its corrosion. The presence of unrecrystallized particle boundaries in the PPS alloy was also unbeneficial with regard to corrosion. The advantage of the LPBF and PPS processes was the ability to change the proportion of α(Mg) to β(Li), which when the complete consolidation of the material is achievable, may increase the corrosion resistance of dual-structured Mg-Li alloys. The results show that powder metallurgy routes have a wide potential to be used for the manufacture of Mg-Li based alloys.
基金supported by the National Natural Science Foundation of China(Grant No.52274290)the Basic Science Center Project for the National Natural Science Foundation of China(No.72088101).
文摘Super-high bed sintering process is an important development direction of iron ore sintering for its lower emission and higher yield.However,there is a lack of deep understanding of the uneven quality of super-high bed sintering products,and the deterioration of reduction disintegration performance,the thickening of hearth layer and the reduction in energy-saving effect are perplexing enterprises and researchers.To ascertain the problems of super-high bed sintering,ten sintering machines with the areas of 265,280,360,550 and 660 m^(2)and bed depth above 900 mm were sampled and analyzed.The results showed that problems were mainly shown in the unevenness of chemical composition,macrostructure,mechanical strength and metallurgical performance.The chemical composition exhibits severe segregation in both horizontal and vertical directions,with basicity segregation reaching as high as 0.81.The uneven macrostructure of sinter is reflected in a 10%difference in porosity and mechanical strength increase in 16%–19%along the vertical direction.The reducibility and reduction disintegration performance gradually deteriorate along the bed depth,with a difference of 10.5%in reducibility and 7.3%in RDI−0.5 mm(reduction disintegration index of sinter with size smaller than 0.5 mm).
基金supported by the National Natural Science Foundation of China (Grant No.52274290)the Basic Science Center Project for the National Natural Science Foundation of China (No.72088101).
文摘Horizontal segregation has been a constraint to the development and application of super-high bed sintering.To eliminate the horizontal segregation of super-high bed sintering,several typical sintering machines were sampled and analyzed,and theoretical calculation was made to compare the bed depth and their differences in different areas within the mixture bin.Then,solutions were proposed and applied to a 265 m^(2) sintering machine.The results showed that the horizontal seg-regation of the 265 m^(2) sintering machine was dominated by particles larger than 8 mm with horizontal segregation degree of 0.48,while 360 and 550 m^(2) sintering machines were affected by 5-8 mm and 1-3 mm particles with horizontal segregation degree of 0.27 and 0.31,respectively.Causes analysis indicated the different segregation distribution results from the matching of the bed depth of each area within the mixture bin.Finally,the horizontal segregation degree not larger than 0.06 was achieved by optimizing the time parameters and the division of three zones on the 265 m^(2) sintering machine.
基金the support from the Shanghai Science and Technology Committee Innovation Grant(Grant No.19ZR1404600)Fudan University-CIOMP Joint Fund(FC2020-006)。
文摘Polymers are widely used materials in aerospace,automotive,construction,medical devices and pharmaceuticals.Polymers are being promoted rapidly due to their ease of manufacturing and improved material properties.Research on polymer processing technology should be paid more attention to due to the increasing demand for polymer applications.Selective laser sintering(SLS)uses a laser to sinter powdered materials(typical polyamide),and it is one of the critical additive manufacturing(AM)techniques of polymer.It irradiates the laser beam on the defined areas by a computer-aided design three-dimensional(3D)model to bind the material together to create a designed 3D solid structure.SLS has many advantages,such as no support structures and excellent mechanical properties resembling injection moulded parts compared with other AM methods.However,the ability of SLS to process polymers is still affected by some defects,such as the porous structure and limited available types of SLS polymers.Therefore,this article reviews the current state-of-the-art SLS of polymers,including the fundamental principles in this technique,the SLS developments of typical polymers,and the essential process parameters in SLS.Furthermore,the applications of SLS are focused,and the conclusions and perspectives are discussed.
基金Chinese Special Funds for Major State Basic Research Projects 973 (No. G1999022104).
文摘A new gas clean-up process called 'integrated sintered metal screen moving granular bed' (ISMSMGB) for the integrated gasification combined cycle (IGCC) and pressured fluidized bed combustion (PFBC) was developed on the basis of a sintered metal candle filter and a cross-flow moving granular bed filter. This is a combination of the surface and deep bed filtering processes. A set of facilities was established and a series of cold model tests were carried out. The dust removal efficiency and the pressure drop of the filter were measured and analyzed. The results show that this process features the advantages of the moving bed for high capacity as well as high inlet dust load and the surface filter for high efficiency. Meanwhile, the granules moving downward cleans the cake on the screen surface, so that the system is operated at steady state.
文摘The sinter quality is important for its performance in a blast furnace,and optimizing ore matching is a main way to ensure the quality and yield of sinter ore and to reduce the cost of ore matching.The research on optimizing ore matching for a 550 m2sintering machine in Shougang Jingtang was carried out in this paper. Firstly,based on the condition of iron ore resourse in Shougang,sintering properties of various ores,especially the high temperature properties were researched,and basic structure of ore matching was determined according to the mutual complementary properties of assimilation and liquid phase fluidity among Australia ore,Brazilian ore and domestic concentrates,that was Australian ore(50%-60%) + Brazilian ore(40%-30%) + domestic concentrates(about 10%).Secondly,9 groups of ore matching schemes were designed and sintering pot tests were carried out,and then the starting scheme of the 550 m2sintering machine was obtained:ore from southern Brazil (20%) +ore from northern Brazil(10%) + semi-limonite(20%) + limonite ore(35%) + domestic concentrates (15%).Thirdly,experiment of optimizing parameters of optimizing basicity,lime ratio,water addition and bed depth were carried out,and 9 groups of ore matching schemes were designed.The results showed that parameters fit for Jingtang currently are as follows:binary basicity is 1.9 - 1.95,lime ratio and water addition is 5%and 7.0% respectively;sintering bed should increase to 800 mm gradually.At last,Jingtang sintering plant was put into production successfully and yields stably,with the bed depth of 800 mm and advanced sintering indexes.
基金This work was financially supported by the National Natural Science Foundation of China(No.52275333).
文摘High speed sintering,a new powder-bed fusion additive manufacturing technology,utilizes infrared lights(IR)to intensely heat and melt polymer powders.The presence of defects such as porosity,which is associated with particle coalescence,is highly dependdent on the level of energy input.This study investigate the influcence of energy input on porosity and its subsequent effects on the mechanical properties and microstructures of PEBA parts.The parts were manufactured with a variety of lamp powers,resulting in a range of energy input levels spanning from low to high.Subsequebtly,they underwent testing using Archimedes’method,followed by tensile testing.The porosity,mechanical characteristics,and energy input exhibit a strong correlation;inadequate energy input was the primary cause of pore formation.Using the reduced IR light power resulted in the following outcomes:porosity,ultimate tensile strength,and elongation of 1.37%,7.6 MPa,and 194.2%,respectively.When the energy input was further increased,the porosity was reduced to as low as 0.05%and the ultimate tensile strength and elongation were increased to their peak values of 233.8%and 9.1 MPa,respectively.
基金supported by National Natural Science Foundation of China (grant No.52036008).
文摘To better understand the evolution characteristics of bed porous structure during iron ore sintering,X-ray computed tomography scanning technology was used to analyze the pore parameters in different areas of the sintering bed.A pore skeleton structure model was established to study the characteristics of the airflow channels in different zones.The absolute permeability of different areas was calculated through simulation,and the corresponding streamline and pressure drop distribution were analyzed.The results show that the porosity of raw material zone,high-temperature zone,and sintered zone increases gradually,which are 37.69%,46.41%,and 55.57%,respectively.The absolute permeability calculation results of the raw material zone and sintered zones are 792.49μm^(2) and 20560.80μm^(2),while the tortuosity is 1.77 and 1.45,respectively.Compared with the raw material zone,the flow streamline in the sintered zone is thicker and denser,the airflow resistance and the pressure drop are minor.