The effects of SiO_(2) content on the preparation process and metallurgical properties of acid oxidized pellets, including compressive strength, reduction, and softening–melting behaviors, were systematically investi...The effects of SiO_(2) content on the preparation process and metallurgical properties of acid oxidized pellets, including compressive strength, reduction, and softening–melting behaviors, were systematically investigated.Mineralogical structures, elemental distribution, and pore size distribution were varied to analyze the mechanism of the effects.The results show that with an increase in SiO_(2) content from 3.51 wt%to 7.18 wt%, compressive strength decreases from 3150 N/pellet to 2100 N/pellet and reducibility decreases from 76.5% to 71.4%.The microstructure showed that pellets with high SiO_(2) content contained more magnetite in the mineralogical structures.Additionally, some liquid phases appeared, which hindered the continuous crystallization of hematite.Also, the softening–melting properties of the pellets clearly deteriorated as the SiO_(2) content increased.With increasing SiO_(2) content, the temperature range of the softening–melting zone decreased, and the maximum differential pressure and the comprehensive permeability index increased significantly.When acid oxidized pellets are used as the raw materials for blast furnace smelting, it should be combined with high basicity sinters to improve the softening–melting behaviors of the comprehensive charge.展开更多
Six additives,i.e.,limestone,lime,magnesite,magnesia,dolomite and light-burned-dolomite,were added for investigating their influences on the pellet quality.For green balls,adding lime and light-burned-dolomite makes t...Six additives,i.e.,limestone,lime,magnesite,magnesia,dolomite and light-burned-dolomite,were added for investigating their influences on the pellet quality.For green balls,adding lime and light-burned-dolomite makes the wet drop strength decrease firstly,and then increase with further increase of additive dosage.Ca(OH)2 affects the bentonite properties at the beginning,but the binding property of Ca(OH)2 will be main when the dosage is higher.The other four additives decrease the drop strength for their disadvantageous physical properties.For preheated pellets,no mater what kind of additive is added,the compressive strength will be decreased because of unmineralized additives.For roasted pellets,calcium additives can form binding phase of calcium-ferrite,and suitable liquid phase will improve recrystallization of hematite,but excessive liquid will destroy the structure of pellets,so the compressive strength of pellet increases firstly and then drops.When adding magnesium additives,the strength will be decreased because of the oxidation of magnetite retarded by MgO.展开更多
The calcined magnesite was utilized as a kind of MgO bearing additive to produce MgO bearing pellets. The effects of MgO on densification and consolidation of pellets were investigated. The experimental results show t...The calcined magnesite was utilized as a kind of MgO bearing additive to produce MgO bearing pellets. The effects of MgO on densification and consolidation of pellets were investigated. The experimental results show that, at the same process parameters, the porosity and pore size distribution of green pellets have no evident relation with the MgO bearing additive, pore size of green pellets is between 15 μm and 35 μm and the porosity of green pellets is about 34%. There is a densification and consolidation phenomenon during the induration process; the pore size and porosity of product pellets decrease gradually; and the structure of product pellets becomes dense. MgO makes a negative effect on the densification and consolidation of product pellets, the densification ratio of pellets decreases from 46.3% to 28.6% with the addition of MgO bearing additive from 0 to 2.0 %. The porosity and the pore size of product pellets increase gradually with the increase of MgO content; When the mass fraction of MgO bearing additive increases from 0 to 2.0%, the pore size of product pellet increases and the pore size distributes in a large range. Also, the porosity increases from 18.61% to 24.06%.展开更多
It is of great importance to elucidate reduction swelling behaviors and reaction mechanism of oxidized pellet in hydrogen-enriched atmosphere under coke oven gas injection. In this work, the effects of hydrogen concen...It is of great importance to elucidate reduction swelling behaviors and reaction mechanism of oxidized pellet in hydrogen-enriched atmosphere under coke oven gas injection. In this work, the effects of hydrogen concentration in N_2-CO-H_2 atmosphere with unchanged CO content on reduction swelling behaviors of oxidized pellet at 1173 K were studied, to clarify the mechanism of hydrogen-enriched reduction and exclude the influences of CO. Then, the reduction swelling behaviors of oxidized pellet at 1173 K in actual atmosphere under coke oven gas(COG) injection, got from the simulation results of multi-fluid blast furnace model, were investigated. The results show that with the concentration of hydrogen increasing in N_2-CO-H_2 gas from 2% to 18%, the reduction swelling index of pellet decreases from 10.12% to 5.57% while the reduction ratio of pellet increases obviously from 39.85% to 69.58%. In addition, with COG injection rate increasing from 0 to 152.34 m^3/t, the reduction swelling index of pellet decreases slightly from 10.71% to 9.54% while the reduction ratio of pellet is increased from 31.57% to 36.39%. The microstructures of pellet are transformed from the platy structure to the flocculent structure.展开更多
The effect of H_2 gas content on the reduction of Panzhihua titanomagnetite concentrate pellets by carbon monoxide was investigated by isothermal reduction experiment using CO-N_2-H_2 gas mixtures in a vertical electr...The effect of H_2 gas content on the reduction of Panzhihua titanomagnetite concentrate pellets by carbon monoxide was investigated by isothermal reduction experiment using CO-N_2-H_2 gas mixtures in a vertical electric resistance furnace.The morphology and phase transformation of reduced samples obtained were detected by scanning electron microscopy,energy disperse spectroscopy analysis and X-ray diffractometry respectively.The results show that increasing H_2 content will enhance the initial stage of reduction rate apparently.There are two reasons responsible for this effect,one is that H_2 accelerates the chemical reaction,and the other is that the addition of H_2 gas can improve the porosity of pellet intensively.It is noteworthy that this effect is more obvious when the reduction temperature reaches 1473 K with sticking phenomenon happening.There are no crystalline phases which can be found such as ulvospinle,ilmenite,ferrous-pseudobrookite and any titanium oxide except titanomagnetite(TTM).The reduction progress is suggested as follows:1) Fe_2O_3→Fe_3O_4→FeO→Fe;2) Fe_2TiO_5→Fe_2TiO_4+Fe_3O_4→TTM.Element Al migrates and gets enriched in high titanium content iron ores,and eventually Al to Ti molar ratio is 1:3.Al is likely to dissolve in titanium iron oxides to form a kind of composite iron compound,which results in the restrain of reduction.展开更多
Pellet injection is a primary method for fueling the plasma in magnetic confinement devices.For that goal the knowledges of pellet ablation and deposition profiles are critical.In the present study,the pellet fueling ...Pellet injection is a primary method for fueling the plasma in magnetic confinement devices.For that goal the knowledges of pellet ablation and deposition profiles are critical.In the present study,the pellet fueling code HPI2 was used to predict the ablation and deposition profiles of deuterium pellets injected into a typical H-mode discharge on the EAST tokamak.Pellet ablation and deposition profiles were evaluated for various pellet injection locations,with the aim at optimizing the pellet injection to obtain a deep fueling depth.In this study,we investigate the effect of the injection angle on the deposition depth of the pellet at different velocities and sizes.The ablation and deposition of the injected pellet are mainly studied at each injection position for three different injection angles:0°,45°,and 60°.The pellet injection on the high field side(HFS)can achieve a more ideal deposition depth than on the low field side(LFS).Among these angles,horizontal injection on the middle plane is relatively better on either the HFS or the LFS.When the injection location is 0.468 m below the middle plane on the HFS or 0.40 m above the middle plane of the LFS,it can achieve a similar deposition depth to the one of its corresponding side.When the pre-cooling effect is taken into account,the deposition depth is predicted to increase only slightly when the pellet is launched from the HFS.The findings of this study will serve as a reference for the update of pellet injection systems for the EAST tokamak.展开更多
High-chromium vanadium-titanium magnetite(HVTM)is a crucial polymetallic-associated resource to be developed.The allpellet operation is a blast furnace trend that aims to reduce carbon dioxide emissions in the future....High-chromium vanadium-titanium magnetite(HVTM)is a crucial polymetallic-associated resource to be developed.The allpellet operation is a blast furnace trend that aims to reduce carbon dioxide emissions in the future.By referencing the production data of vanadium-titanium magnetite blast furnaces,this study explored the softening-melting behavior of high-chromium vanadium-titanium magnetite and obtained the optimal integrated burden based on flux pellets.The results show that the burden with a composition of 70wt%flux pellets and 30wt%acid pellets exhibits the best softening-melting properties.In comparison to that of the single burden,the softening-melting characteristic temperature of this burden composition was higher.The melting interval first increased from 307 to 362℃and then decreased to 282℃.The maximum pressure drop(ΔPmax)decreased from 26.76 to 19.01 kPa.The permeability index(S)dropped from 4643.5 to 2446.8 kPa·℃.The softening-melting properties of the integrated burden were apparently improved.The acid pellets played a role in withstanding load during the softening process.The flux pellets in the integrated burden exhibited a higher slag melting point,which increased the melting temperature during the melting process.The slag homogeneity and the TiC produced by over-reduction led to the gas permeability deterioration of the single burden.The segregation of the flux and acid pellets in the HVTM proportion and basicity mainly led to the better softening-melting properties of the integrated burden.展开更多
Direct reduction based on hydrogen metallurgical gas-based shaft furnace is a promising technology for the efficient and low-carbon smelting of vanadium-titanium magnetite.However,in this process,the sticking of pelle...Direct reduction based on hydrogen metallurgical gas-based shaft furnace is a promising technology for the efficient and low-carbon smelting of vanadium-titanium magnetite.However,in this process,the sticking of pellets occurs due to the aggregation of metal-lic iron between the contact surfaces of adjacent pellets and has a serious negative effect on the continuous operation.This paper presents a detailed experimental study of the effect of TiO2 on the sticking behavior of pellets during direct reduction under different conditions.Results showed that the sticking index(SI)decreased linearly with the increasing TiO2 addition.This phenomenon can be attributed to the increase in unreduced FeTiO3 during reduction,leading to a decrease in the number and strength of metallic iron interconnections at the sticking interface.When the TiO2 addition amount was raised from 0 to 15wt%at 1100°C,the SI also increased from 0.71%to 59.91%.The connection of the slag phase could be attributed to the sticking at a low reduction temperature,corresponding to the low sticking strength.Moreover,the interconnection of metallic iron became the dominant factor,and the SI increased sharply with the increase in re-duction temperature.TiO2 had a greater effect on SI at a high reduction temperature than at a low reduction temperature.展开更多
The increase to the proportion of fluxed pellets in the blast furnace burden is a useful way to reduce the carbon emissions in the ironmaking process.In this study,the interaction between calcium carbonate and iron or...The increase to the proportion of fluxed pellets in the blast furnace burden is a useful way to reduce the carbon emissions in the ironmaking process.In this study,the interaction between calcium carbonate and iron ore powder and the mineralization mechanism of fluxed iron ore pellet in the roasting process were investigated through diffusion couple experiments.Scanning electron microscopy with energy dispersive spectroscopy was used to study the elements’diffusion and phase transformation during the roasting process.The results indicated that limestone decomposed into calcium oxide,and magnetite was oxidized to hematite at the early stage of preheating.With the increase in roasting temperature,the diffusion rate of Fe and Ca was obviously accelerated,while the diffusion rate of Si was relatively slow.The order of magnitude of interdiffusion coefficient of Fe_(2)O_(3)-CaO diffusion couple was 10^(−10) m^(2)·s^(−1) at a roasting temperature of 1200℃for 9 h.Ca_(2)Fe_(2)O_(5) was the initial product in the Fe_(2)O_(3)-CaO-SiO_(2) diffusion interface,and then Ca_(2)Fe_(2)O_(5) continued to react with Fe_(2)O_(3) to form CaFe_(2)O_(4).With the expansion of the diffusion region,the sillico-ferrite of calcium liquid phase was produced due to the melting of SiO_(2) into CaFe_(2)O_(4),which can strengthen the consolidation of fluxed pellets.Furthermore,andradite would be formed around a small part of quartz particles,which is also conducive to the consolidation of fluxed pellets.In addition,the principle diagram of limestone and quartz diffusion reaction in the process of fluxed pellet roasting was discussed.展开更多
The self-charging concept has drawn considerable attention due to its excellent ability to achieve environmental energy harvesting,conversion and storage without an external power supply.However,most self-charging des...The self-charging concept has drawn considerable attention due to its excellent ability to achieve environmental energy harvesting,conversion and storage without an external power supply.However,most self-charging designs assembled by multiple energy harvesting,conversion and storage materials increase the energy transfer loss;the environmental energy supply is generally limited by climate and meteorological conditions,hindering the potential application of these selfpowered devices to be available at all times.Based on aerobic autoxidation of catechol,which is similar to the electrochemical oxidation of the catechol groups on the carbon materials under an electrical charge,we proposed an air-breathing chemical self-charge concept based on the aerobic autoxidation of catechol groups on oxygen-enriched carbon materials to ortho-quinone groups.Energy harvesting,conversion and storage functions could be integrated on a single carbon material to avoid the energy transfer loss among the different materials.Moreover,the assembled Cu/oxygen-enriched carbon battery confirmed the feasibility of the air-oxidation self-charging/electrical discharging mechanism for potential applications.This air-breathing chemical self-charge concept could facilitate the exploration of high-efficiency sustainable air self-charging devices.展开更多
The microwave heating characteristics of the mixture with oxidized pellet and coal was studied,and the non-isothermal reduction dynamics is discussed.The results show that,the slow-heating stage of the temperature ris...The microwave heating characteristics of the mixture with oxidized pellet and coal was studied,and the non-isothermal reduction dynamics is discussed.The results show that,the slow-heating stage of the temperature rising process can be segmented into two heating temperature curves approximately that have good linear relationship.They can be seen as temperature programming.In the first stage,between 827 and 1 073 K,the reaction mechanism obeys diffusion controlled model.In the second stage,between 1 093 and 1 323 K,the reaction mechanism also obeys diffusion controlled model.The apparent activation energies are found to be 75.13 kJ/mol for the first stage and 53.17 kJ/mol for the second stage.That is lower than the apparent activation energy under conventional heating.The microstructure of the reduced pellets shows that microwave can improve the kinetics of the reduction.Microwave has anxo-action to the reaction obviously.展开更多
As a main charging form of BF (blast furnace), pellets play an important role in blast furnace process. However, comparing with sinters, pellets have many disadvantages, such as reduction swelling, low softening and m...As a main charging form of BF (blast furnace), pellets play an important role in blast furnace process. However, comparing with sinters, pellets have many disadvantages, such as reduction swelling, low softening and melting temperature and so on. Therefore, the flux pellets have been applied in blast furnace widely, especially MgO containing pellets. The light burned magnesite is applied as MgO containing additive in pellet production. The characters of light burned magnesite are explored. Meanwhile, the effects of it on low-temperature metallurgical properties are investigated such as low-temperature reduction degradation index (RDI), compressive strength (CS) and the reduction swelling index (RSI). The light burned magnesite calcined at 850 ℃ manifests better grindability, larger specific surface area, and higher hydration activity. It is found that the addition of light burned magnesite can improve low-temperature metallurgical properties (RDI, RSI) of the pellets. With the increase of light burned magnesite in pellets, the RSI and RDI decrease gradually; when the proportion of light burned magnesite does not exceed 2.0% in pellets, the CS decreases slightly, but it still surpasses 2 689 N, which can still meet the demand of BF.展开更多
Based on conduction,convection and radiation heat transfer among the flue gas,kiln wall,and the pellet bed material,and on the basis of the coal combustion and analysis of reaction heat of pellet induration in the rot...Based on conduction,convection and radiation heat transfer among the flue gas,kiln wall,and the pellet bed material,and on the basis of the coal combustion and analysis of reaction heat of pellet induration in the rotary kiln,the temperature field model of rotary kiln was established.Using visual studio net,matlab and open source computer vision library as development tools,combining with the ActiveX data objects database technology,the temperature field simulation system for rotary kiln of iron ore oxidized pellet production was developed.Temperature distribution of pellet and flue gas in rotary kiln was dynamically displayed.展开更多
The influences of the time,temperature and atmosphere on the reduction swelling of oxidized pellets were investigated by single factor experiments.The mechanisms of reduction swelling of oxidized pellets were analyzed...The influences of the time,temperature and atmosphere on the reduction swelling of oxidized pellets were investigated by single factor experiments.The mechanisms of reduction swelling of oxidized pellets were analyzed and investigated by SEM(scanning electron microscopy)and XRD(X-ray diffractometer)analysis.The results show that the change rules of reduction swelling index of oxidized pellets in different reduction atmospheres are very similar.With the increase of reduction time,the reduction swelling index moves up firstly and then down.When the reduction temperature is above 900℃,α-quartz turns intoα-tridymite,and the transition generates additional volume expansion effect.The reduction swelling index changes faster in H2 atmosphere than in CO atmosphere.Increasing H2 content in the reduction atmosphere is useful to decrease the reduction swelling index,but it is also easy to cause oxidized pellets cracking.展开更多
Calcined magnesite is a binding additive and an MgO-bearing flux for pellets production.The effects of calcination temperature and time on the characteristics of calcined magnesite were investigated.Experimental resul...Calcined magnesite is a binding additive and an MgO-bearing flux for pellets production.The effects of calcination temperature and time on the characteristics of calcined magnesite were investigated.Experimental results indicated that the best calcination condition was 850℃and 1h.Under this condition,the hydration activity of the calcined magnesite was 80.56%,and the average diameter of crystal grain D,specific surface area Sand the medium particle size D50 were 25.4nm,45.40m2/g and 3.41μm,respectively.This kind of calcined magnesite was a good binding additive for pellets production.At the same proportion of calcined magnesite,the effects of activities of calcined magnesite on metallurgical properties of green pellet and indurated pellet showed that calcined magnesite with high activity could improve the dropping strength and compressive strength of green pellet and enhance the burst temperature of green pellet;however,the effects of activity on compressive strength,low-temperature reduction degradation index,reduction swelling index and reduction index of indurated pellet were not obvious.展开更多
Dry reforming of methane(DRM) is an attractive technology for utilizing the greenhouse gases(CO_(2) and CH_(4)) to produce syngas. However, the catalyst pellets for DRM are heavily plagued by deactivation by coking, w...Dry reforming of methane(DRM) is an attractive technology for utilizing the greenhouse gases(CO_(2) and CH_(4)) to produce syngas. However, the catalyst pellets for DRM are heavily plagued by deactivation by coking, which prevents this technology from commercialization. In this work, a pore network model is developed to probe the catalyst deactivation by coking in a Ni/Al_(2)O_(3) catalyst pellet for DRM. The reaction conditions can significantly change the coking rate and then affect the catalyst deactivation. The catalyst lifetime is higher under lower temperature, pressure, and CH_(4)/CO_(2) molar ratio, but the maximum coke content in a catalyst pellet is independent of these reaction conditions. The catalyst pellet with larger pore diameter, narrower pore size distribution and higher pore connectivity is more robust against catalyst deactivation by coking, as the pores in this pellet are more difficult to be plugged or inaccessible.The maximum coke content is also higher for narrower pore size distribution and higher pore connectivity, as the number of inaccessible pores is lower. Besides, the catalyst pellet radius only slightly affects the coke content, although the diffusion limitation increases with the pellet radius. These results should serve to guide the rational design of robust DRM catalyst pellets against deactivation by coking.展开更多
Background Oxidized soybean oil(OSO)has been shown to impair growth and exacerbate inflammation,leading to intestinal barrier injury in animals.Recent evidence suggests important roles for resveratrol(RES)in the promo...Background Oxidized soybean oil(OSO)has been shown to impair growth and exacerbate inflammation,leading to intestinal barrier injury in animals.Recent evidence suggests important roles for resveratrol(RES)in the promoting growth performance,antioxidant capacity,anti-inflammatory,and regulate intestinal barriers in animals.Therefore,The objectives of this study are to investigate the effects of dietary RES(purity 98%)supplementation on the growth performance,antioxidant capacity,inflammatory state,and intestinal function of weaned piglets challenged with OSO.Methods A total of 28 castrated weaned male piglets with a similar body weight of 10.197 replications per treatment and±0.10 kg were randomly assigned to 4 dietary treatments for 28-d feeding trial with 1 piglet per replicate.Treatments were arranged as a 2×2 factorial with oil type[3%fresh soybean oil(FSO)vs.3%OSO]and dietary RES(0vs.300 mg/kg).Results The results showed that relative to the FSO group,OSO stress tended to decrease the average daily feed intake(ADFI),and decreased the activity levels of lipase,villus/crypt ratio(VCR),the mRNA expression of FABP1,SOD2,IL-10 and ZO-1 in the jejunum,and SOD2,GPX1,occludin and ZO-1 in the colon,the levels of acetic acid in the colonic digesta,whereas up-regulated the mRNA expression of IL-1βand TNF-αin the jejunum(P<0.05).Moreover,dietary supplementation with RES increased ether extract(EE),the activity levels of sucrase,lipase,α-amylase,villus height(VH)and VCR,the mRNA expression of FABP1,SOD2,IL-10 and occludin in the jejunum,and FABP1,PPAR-γ,GPX1,occludin and ZO-1 in the colon,and the abundance of Firmicutes,acetic and propionic acid,but decreased the levels of D-lactic acid in the plasma,the abundance of Bacteroidetes in the colonic digesta of weaned piglets compared to the non-RES group(P<0.05).Meanwhile,in the interaction effect analysis,relative to the OSO group,dietary RES supplementation in the diets supplemented with OSO increased the activity levels of trypsin,VH in the jejunum,the abundance of Actinobacteria,the levels of butyric acid of weaned piglets,but failed to influence the activity levels of trypsin and VH,Actinobacteria abundance,the levels of butyric acid when diets were supplemented with FSO(interaction,P<0.05).Relative to the OSO group,dietary RES supplementation in the diets supplemented with OSO decreased the activity levels of DAO in the plasma of weaned piglets but failed to influence the activity levels of DAO when diets were supplemented with FSO(interaction,P<0.05).Relative to the FSO group,dietary RES supplementation in the diets supplemented with FSO decreased the level of propionic acid,whereas RES supplementation failed to influence the level of propionic acid when the diet was supplemented with OSO(interaction,P<0.01).Conclusions Inclusion of OSO intensified inflammatory states and impaired the intestinal health characteristics of weaned piglets.Dietary RES supplementation improved the antioxidant capacity,anti-inflammatory activity,and intestinal morphology.Further studies showed that the protective effects of RES on gut health could be linked to the decreased abundance of Prevotella_1,Clostridium_sensu_stricto_6,and Prevotellaceae_UCG003 and increased levels of acetic and propionic acid.展开更多
The mechanism of high pressure roll grinding on improvement of compression strength of oxidized hematite pellets was researched by considering their roasting properties.The results indicate that oxidized hematite pell...The mechanism of high pressure roll grinding on improvement of compression strength of oxidized hematite pellets was researched by considering their roasting properties.The results indicate that oxidized hematite pellets require higher preheating temperature and longer preheating time to attain required compression strength of pellets compared with the common magnetite oxidized pellets.It is found that when the hematite concentrates are pretreated by high pressure roll grinding(HPRG),the compression strengths of preheated and roasted oxidized hematite pellets get improved even with lower preheating and roasting temperatures and shorter preheating and roasting time.The mechanism for HPRG to improve roasting properties of oxidized pellets were investigated and the cause mainly lies in the increase of micro-sized particles and the decrease of dispersion degree for hematite concentrates,which promotes the hematite concentrate particles to be compacted,the solid-phase crystallization,and finally the formation of Fe2O3 bonding bridges during subsequent high temperature roasting process.展开更多
The oxygen distribution and evolution within the oxygen carrier exert significant influence on chemical looping processes.This paper describes the influence of oxygen bulk diffusion within FeVO4 oxygen carrier pellets...The oxygen distribution and evolution within the oxygen carrier exert significant influence on chemical looping processes.This paper describes the influence of oxygen bulk diffusion within FeVO4 oxygen carrier pellets on the chemical looping oxidative propane dehydrogenation(CL-ODH).During CL-ODH,the oxygen concentration at the pellet surface initially decreased and then maintained stable before the final decrease.At the stage with the stable surface oxygen concentration,the reaction showed a stable C3H6 formation rate and high C3H6 selectivity.Therefore,based on Fick’s second law,the oxygen distribution and evolution in the oxygen carrier at this stage were further analyzed.It was found that main reactions of selective oxidation and over-oxidation were controlled by the oxygen bulk diffusion.C3H8 conversion rate kept decreasing during this stage due to the decrease of the oxygen flux caused by the decline of oxygen gradient within the oxygen carrier,while C3H6 selectivity increased due to the decrease of overoxidation.In addition,reaction rates could increase with the propane partial pressure due to the increase of the oxygen gradient within the oxygen carrier until the bulk transfer reached its limit at higher propane partial pressure.This study provides fundamental insights for the diffusion-controlled chemical looping reactions.展开更多
Magnesium alloys are more widely used at higher temperatures.However,it is not well known whether oxide layer,produced at high temperature,could show corrosion protection.Thus,the corrosion behaviors of oxidized AZW80...Magnesium alloys are more widely used at higher temperatures.However,it is not well known whether oxide layer,produced at high temperature,could show corrosion protection.Thus,the corrosion behaviors of oxidized AZW800 alloy were investigated by hydrogen evolution and electrochemical measurements to evaluate effect of oxide layer on corrosion resistance.The results showed that corrosion of removed oxide layer AZW800 alloy showed characteristic of localized corrosion,leaving randomly bulky pits.While reserved oxide layer AZW800 alloy exhibited a relatively uniform corrosion.The results indicated that oxide layer could hinder corrosion of oxidized AZW800 alloy in the initial period of immersion.While subsequently,aggravated corrosion would occur owing to defects of oxide layer and less protective products film.Besides,present of oxide layer eliminated micro-galvanic couple on alloy surface.The synergistic effect of elimination of micro-galvanic couple on alloy surface and alkalization effect transforms localized corrosion into relatively uniform corrosion of alloys.展开更多
基金financially supported by the Key Program of the National Natural Science Foundation of China (No.U1360205)the Natural Science Foundation of Hebei Province of China (No.E2019209424)。
文摘The effects of SiO_(2) content on the preparation process and metallurgical properties of acid oxidized pellets, including compressive strength, reduction, and softening–melting behaviors, were systematically investigated.Mineralogical structures, elemental distribution, and pore size distribution were varied to analyze the mechanism of the effects.The results show that with an increase in SiO_(2) content from 3.51 wt%to 7.18 wt%, compressive strength decreases from 3150 N/pellet to 2100 N/pellet and reducibility decreases from 76.5% to 71.4%.The microstructure showed that pellets with high SiO_(2) content contained more magnetite in the mineralogical structures.Additionally, some liquid phases appeared, which hindered the continuous crystallization of hematite.Also, the softening–melting properties of the pellets clearly deteriorated as the SiO_(2) content increased.With increasing SiO_(2) content, the temperature range of the softening–melting zone decreased, and the maximum differential pressure and the comprehensive permeability index increased significantly.When acid oxidized pellets are used as the raw materials for blast furnace smelting, it should be combined with high basicity sinters to improve the softening–melting behaviors of the comprehensive charge.
基金Project(2008BAB32B06) supported by the Key Projects in the National Science and Technology Pillar Program during the 11th Five-year Plan PeriodProject(2009ybfz20) supported by the Program for Excellent Doctor’s Degree Paper in Central South University,ChinaProject(1343/74333001114) supported by the Postgraduate’s Paper Innovation Fund of Hunan Province,China
文摘Six additives,i.e.,limestone,lime,magnesite,magnesia,dolomite and light-burned-dolomite,were added for investigating their influences on the pellet quality.For green balls,adding lime and light-burned-dolomite makes the wet drop strength decrease firstly,and then increase with further increase of additive dosage.Ca(OH)2 affects the bentonite properties at the beginning,but the binding property of Ca(OH)2 will be main when the dosage is higher.The other four additives decrease the drop strength for their disadvantageous physical properties.For preheated pellets,no mater what kind of additive is added,the compressive strength will be decreased because of unmineralized additives.For roasted pellets,calcium additives can form binding phase of calcium-ferrite,and suitable liquid phase will improve recrystallization of hematite,but excessive liquid will destroy the structure of pellets,so the compressive strength of pellet increases firstly and then drops.When adding magnesium additives,the strength will be decreased because of the oxidation of magnetite retarded by MgO.
基金Projects(51074206,51074040) supported by the National Natural Science Foundation of China
文摘The calcined magnesite was utilized as a kind of MgO bearing additive to produce MgO bearing pellets. The effects of MgO on densification and consolidation of pellets were investigated. The experimental results show that, at the same process parameters, the porosity and pore size distribution of green pellets have no evident relation with the MgO bearing additive, pore size of green pellets is between 15 μm and 35 μm and the porosity of green pellets is about 34%. There is a densification and consolidation phenomenon during the induration process; the pore size and porosity of product pellets decrease gradually; and the structure of product pellets becomes dense. MgO makes a negative effect on the densification and consolidation of product pellets, the densification ratio of pellets decreases from 46.3% to 28.6% with the addition of MgO bearing additive from 0 to 2.0 %. The porosity and the pore size of product pellets increase gradually with the increase of MgO content; When the mass fraction of MgO bearing additive increases from 0 to 2.0%, the pore size of product pellet increases and the pore size distributes in a large range. Also, the porosity increases from 18.61% to 24.06%.
基金Project(51404005)supported by the National Natural Science Foundation of China
文摘It is of great importance to elucidate reduction swelling behaviors and reaction mechanism of oxidized pellet in hydrogen-enriched atmosphere under coke oven gas injection. In this work, the effects of hydrogen concentration in N_2-CO-H_2 atmosphere with unchanged CO content on reduction swelling behaviors of oxidized pellet at 1173 K were studied, to clarify the mechanism of hydrogen-enriched reduction and exclude the influences of CO. Then, the reduction swelling behaviors of oxidized pellet at 1173 K in actual atmosphere under coke oven gas(COG) injection, got from the simulation results of multi-fluid blast furnace model, were investigated. The results show that with the concentration of hydrogen increasing in N_2-CO-H_2 gas from 2% to 18%, the reduction swelling index of pellet decreases from 10.12% to 5.57% while the reduction ratio of pellet increases obviously from 39.85% to 69.58%. In addition, with COG injection rate increasing from 0 to 152.34 m^3/t, the reduction swelling index of pellet decreases slightly from 10.71% to 9.54% while the reduction ratio of pellet is increased from 31.57% to 36.39%. The microstructures of pellet are transformed from the platy structure to the flocculent structure.
基金Project (51134008) supported by the National Natural Science Foundation of ChinaProject (2012CB720401) supported by the National Basic Research Program of China
文摘The effect of H_2 gas content on the reduction of Panzhihua titanomagnetite concentrate pellets by carbon monoxide was investigated by isothermal reduction experiment using CO-N_2-H_2 gas mixtures in a vertical electric resistance furnace.The morphology and phase transformation of reduced samples obtained were detected by scanning electron microscopy,energy disperse spectroscopy analysis and X-ray diffractometry respectively.The results show that increasing H_2 content will enhance the initial stage of reduction rate apparently.There are two reasons responsible for this effect,one is that H_2 accelerates the chemical reaction,and the other is that the addition of H_2 gas can improve the porosity of pellet intensively.It is noteworthy that this effect is more obvious when the reduction temperature reaches 1473 K with sticking phenomenon happening.There are no crystalline phases which can be found such as ulvospinle,ilmenite,ferrous-pseudobrookite and any titanium oxide except titanomagnetite(TTM).The reduction progress is suggested as follows:1) Fe_2O_3→Fe_3O_4→FeO→Fe;2) Fe_2TiO_5→Fe_2TiO_4+Fe_3O_4→TTM.Element Al migrates and gets enriched in high titanium content iron ores,and eventually Al to Ti molar ratio is 1:3.Al is likely to dissolve in titanium iron oxides to form a kind of composite iron compound,which results in the restrain of reduction.
基金supported by the National Natural Science Foundation of China (Grant Nos.12205196 and 12275040)the National Key Research and Development Program of China (Grant No.2022YFE03090003)。
文摘Pellet injection is a primary method for fueling the plasma in magnetic confinement devices.For that goal the knowledges of pellet ablation and deposition profiles are critical.In the present study,the pellet fueling code HPI2 was used to predict the ablation and deposition profiles of deuterium pellets injected into a typical H-mode discharge on the EAST tokamak.Pellet ablation and deposition profiles were evaluated for various pellet injection locations,with the aim at optimizing the pellet injection to obtain a deep fueling depth.In this study,we investigate the effect of the injection angle on the deposition depth of the pellet at different velocities and sizes.The ablation and deposition of the injected pellet are mainly studied at each injection position for three different injection angles:0°,45°,and 60°.The pellet injection on the high field side(HFS)can achieve a more ideal deposition depth than on the low field side(LFS).Among these angles,horizontal injection on the middle plane is relatively better on either the HFS or the LFS.When the injection location is 0.468 m below the middle plane on the HFS or 0.40 m above the middle plane of the LFS,it can achieve a similar deposition depth to the one of its corresponding side.When the pre-cooling effect is taken into account,the deposition depth is predicted to increase only slightly when the pellet is launched from the HFS.The findings of this study will serve as a reference for the update of pellet injection systems for the EAST tokamak.
基金supported by the National Natural Science Foundation of China (Nos.52174277 and 52204309)the China Postdoctoral Science Foundation (No.2022M720683).
文摘High-chromium vanadium-titanium magnetite(HVTM)is a crucial polymetallic-associated resource to be developed.The allpellet operation is a blast furnace trend that aims to reduce carbon dioxide emissions in the future.By referencing the production data of vanadium-titanium magnetite blast furnaces,this study explored the softening-melting behavior of high-chromium vanadium-titanium magnetite and obtained the optimal integrated burden based on flux pellets.The results show that the burden with a composition of 70wt%flux pellets and 30wt%acid pellets exhibits the best softening-melting properties.In comparison to that of the single burden,the softening-melting characteristic temperature of this burden composition was higher.The melting interval first increased from 307 to 362℃and then decreased to 282℃.The maximum pressure drop(ΔPmax)decreased from 26.76 to 19.01 kPa.The permeability index(S)dropped from 4643.5 to 2446.8 kPa·℃.The softening-melting properties of the integrated burden were apparently improved.The acid pellets played a role in withstanding load during the softening process.The flux pellets in the integrated burden exhibited a higher slag melting point,which increased the melting temperature during the melting process.The slag homogeneity and the TiC produced by over-reduction led to the gas permeability deterioration of the single burden.The segregation of the flux and acid pellets in the HVTM proportion and basicity mainly led to the better softening-melting properties of the integrated burden.
基金the National Natural Science Foundation of China(No.51904063)the Science and Technology Plan Project of Liaoning Province,China(No.2022JH24/10200027)+1 种基金the Key Research and Development Project of Hebei Province,China(No.21314001D)the seventh batch of the Ten Thousand Talents Plan(No.ZX20220553).
文摘Direct reduction based on hydrogen metallurgical gas-based shaft furnace is a promising technology for the efficient and low-carbon smelting of vanadium-titanium magnetite.However,in this process,the sticking of pellets occurs due to the aggregation of metal-lic iron between the contact surfaces of adjacent pellets and has a serious negative effect on the continuous operation.This paper presents a detailed experimental study of the effect of TiO2 on the sticking behavior of pellets during direct reduction under different conditions.Results showed that the sticking index(SI)decreased linearly with the increasing TiO2 addition.This phenomenon can be attributed to the increase in unreduced FeTiO3 during reduction,leading to a decrease in the number and strength of metallic iron interconnections at the sticking interface.When the TiO2 addition amount was raised from 0 to 15wt%at 1100°C,the SI also increased from 0.71%to 59.91%.The connection of the slag phase could be attributed to the sticking at a low reduction temperature,corresponding to the low sticking strength.Moreover,the interconnection of metallic iron became the dominant factor,and the SI increased sharply with the increase in re-duction temperature.TiO2 had a greater effect on SI at a high reduction temperature than at a low reduction temperature.
基金support of Shanxi Province Major Science and Technology Projects,China (No.20191101002).
文摘The increase to the proportion of fluxed pellets in the blast furnace burden is a useful way to reduce the carbon emissions in the ironmaking process.In this study,the interaction between calcium carbonate and iron ore powder and the mineralization mechanism of fluxed iron ore pellet in the roasting process were investigated through diffusion couple experiments.Scanning electron microscopy with energy dispersive spectroscopy was used to study the elements’diffusion and phase transformation during the roasting process.The results indicated that limestone decomposed into calcium oxide,and magnetite was oxidized to hematite at the early stage of preheating.With the increase in roasting temperature,the diffusion rate of Fe and Ca was obviously accelerated,while the diffusion rate of Si was relatively slow.The order of magnitude of interdiffusion coefficient of Fe_(2)O_(3)-CaO diffusion couple was 10^(−10) m^(2)·s^(−1) at a roasting temperature of 1200℃for 9 h.Ca_(2)Fe_(2)O_(5) was the initial product in the Fe_(2)O_(3)-CaO-SiO_(2) diffusion interface,and then Ca_(2)Fe_(2)O_(5) continued to react with Fe_(2)O_(3) to form CaFe_(2)O_(4).With the expansion of the diffusion region,the sillico-ferrite of calcium liquid phase was produced due to the melting of SiO_(2) into CaFe_(2)O_(4),which can strengthen the consolidation of fluxed pellets.Furthermore,andradite would be formed around a small part of quartz particles,which is also conducive to the consolidation of fluxed pellets.In addition,the principle diagram of limestone and quartz diffusion reaction in the process of fluxed pellet roasting was discussed.
基金financially supported by the National Natural Science Foundation of China(51503178,52202048,52027801)National Key R&D Program of China(2017YFA0206301)+1 种基金China-Germany Collaboration Project(M-0199)Natural Science Foundation of Hebei Province(B2021203012,E2022203082)。
文摘The self-charging concept has drawn considerable attention due to its excellent ability to achieve environmental energy harvesting,conversion and storage without an external power supply.However,most self-charging designs assembled by multiple energy harvesting,conversion and storage materials increase the energy transfer loss;the environmental energy supply is generally limited by climate and meteorological conditions,hindering the potential application of these selfpowered devices to be available at all times.Based on aerobic autoxidation of catechol,which is similar to the electrochemical oxidation of the catechol groups on the carbon materials under an electrical charge,we proposed an air-breathing chemical self-charge concept based on the aerobic autoxidation of catechol groups on oxygen-enriched carbon materials to ortho-quinone groups.Energy harvesting,conversion and storage functions could be integrated on a single carbon material to avoid the energy transfer loss among the different materials.Moreover,the assembled Cu/oxygen-enriched carbon battery confirmed the feasibility of the air-oxidation self-charging/electrical discharging mechanism for potential applications.This air-breathing chemical self-charge concept could facilitate the exploration of high-efficiency sustainable air self-charging devices.
基金Sponsored by National Science Fund for Distinguished Young Scholars of China(50725416)
文摘The microwave heating characteristics of the mixture with oxidized pellet and coal was studied,and the non-isothermal reduction dynamics is discussed.The results show that,the slow-heating stage of the temperature rising process can be segmented into two heating temperature curves approximately that have good linear relationship.They can be seen as temperature programming.In the first stage,between 827 and 1 073 K,the reaction mechanism obeys diffusion controlled model.In the second stage,between 1 093 and 1 323 K,the reaction mechanism also obeys diffusion controlled model.The apparent activation energies are found to be 75.13 kJ/mol for the first stage and 53.17 kJ/mol for the second stage.That is lower than the apparent activation energy under conventional heating.The microstructure of the reduced pellets shows that microwave can improve the kinetics of the reduction.Microwave has anxo-action to the reaction obviously.
基金Item Sponsored by National Natural Science Foundation of China ( 51074206 , 51074040 )
文摘As a main charging form of BF (blast furnace), pellets play an important role in blast furnace process. However, comparing with sinters, pellets have many disadvantages, such as reduction swelling, low softening and melting temperature and so on. Therefore, the flux pellets have been applied in blast furnace widely, especially MgO containing pellets. The light burned magnesite is applied as MgO containing additive in pellet production. The characters of light burned magnesite are explored. Meanwhile, the effects of it on low-temperature metallurgical properties are investigated such as low-temperature reduction degradation index (RDI), compressive strength (CS) and the reduction swelling index (RSI). The light burned magnesite calcined at 850 ℃ manifests better grindability, larger specific surface area, and higher hydration activity. It is found that the addition of light burned magnesite can improve low-temperature metallurgical properties (RDI, RSI) of the pellets. With the increase of light burned magnesite in pellets, the RSI and RDI decrease gradually; when the proportion of light burned magnesite does not exceed 2.0% in pellets, the CS decreases slightly, but it still surpasses 2 689 N, which can still meet the demand of BF.
基金Sponsored by Program for New Century Excellent Talents in University of China(NCET-05-0630)
文摘Based on conduction,convection and radiation heat transfer among the flue gas,kiln wall,and the pellet bed material,and on the basis of the coal combustion and analysis of reaction heat of pellet induration in the rotary kiln,the temperature field model of rotary kiln was established.Using visual studio net,matlab and open source computer vision library as development tools,combining with the ActiveX data objects database technology,the temperature field simulation system for rotary kiln of iron ore oxidized pellet production was developed.Temperature distribution of pellet and flue gas in rotary kiln was dynamically displayed.
基金Sponsored by National Natural Science Foundation of China(51104014)National Natural Science Foundation of China and Baosteel(51134008)National Basic Research Program(973Program)of China(2012CB720401)
文摘The influences of the time,temperature and atmosphere on the reduction swelling of oxidized pellets were investigated by single factor experiments.The mechanisms of reduction swelling of oxidized pellets were analyzed and investigated by SEM(scanning electron microscopy)and XRD(X-ray diffractometer)analysis.The results show that the change rules of reduction swelling index of oxidized pellets in different reduction atmospheres are very similar.With the increase of reduction time,the reduction swelling index moves up firstly and then down.When the reduction temperature is above 900℃,α-quartz turns intoα-tridymite,and the transition generates additional volume expansion effect.The reduction swelling index changes faster in H2 atmosphere than in CO atmosphere.Increasing H2 content in the reduction atmosphere is useful to decrease the reduction swelling index,but it is also easy to cause oxidized pellets cracking.
基金Item Sponsored by National Natural Science Foundation of China(51074206,51074040)
文摘Calcined magnesite is a binding additive and an MgO-bearing flux for pellets production.The effects of calcination temperature and time on the characteristics of calcined magnesite were investigated.Experimental results indicated that the best calcination condition was 850℃and 1h.Under this condition,the hydration activity of the calcined magnesite was 80.56%,and the average diameter of crystal grain D,specific surface area Sand the medium particle size D50 were 25.4nm,45.40m2/g and 3.41μm,respectively.This kind of calcined magnesite was a good binding additive for pellets production.At the same proportion of calcined magnesite,the effects of activities of calcined magnesite on metallurgical properties of green pellet and indurated pellet showed that calcined magnesite with high activity could improve the dropping strength and compressive strength of green pellet and enhance the burst temperature of green pellet;however,the effects of activity on compressive strength,low-temperature reduction degradation index,reduction swelling index and reduction index of indurated pellet were not obvious.
基金financially supported by the National Natural Science Foundation of China (22078090 and 92034301)the Shanghai Rising-Star Program (21QA1402000)+1 种基金the Natural Science Foundation of Shanghai (21ZR1418100)the Open Project of State Key Laboratory of Chemical Engineering (SKL-ChE-21C02)。
文摘Dry reforming of methane(DRM) is an attractive technology for utilizing the greenhouse gases(CO_(2) and CH_(4)) to produce syngas. However, the catalyst pellets for DRM are heavily plagued by deactivation by coking, which prevents this technology from commercialization. In this work, a pore network model is developed to probe the catalyst deactivation by coking in a Ni/Al_(2)O_(3) catalyst pellet for DRM. The reaction conditions can significantly change the coking rate and then affect the catalyst deactivation. The catalyst lifetime is higher under lower temperature, pressure, and CH_(4)/CO_(2) molar ratio, but the maximum coke content in a catalyst pellet is independent of these reaction conditions. The catalyst pellet with larger pore diameter, narrower pore size distribution and higher pore connectivity is more robust against catalyst deactivation by coking, as the pores in this pellet are more difficult to be plugged or inaccessible.The maximum coke content is also higher for narrower pore size distribution and higher pore connectivity, as the number of inaccessible pores is lower. Besides, the catalyst pellet radius only slightly affects the coke content, although the diffusion limitation increases with the pellet radius. These results should serve to guide the rational design of robust DRM catalyst pellets against deactivation by coking.
基金supported by the National Natural Science Foundation of China(31872986)。
文摘Background Oxidized soybean oil(OSO)has been shown to impair growth and exacerbate inflammation,leading to intestinal barrier injury in animals.Recent evidence suggests important roles for resveratrol(RES)in the promoting growth performance,antioxidant capacity,anti-inflammatory,and regulate intestinal barriers in animals.Therefore,The objectives of this study are to investigate the effects of dietary RES(purity 98%)supplementation on the growth performance,antioxidant capacity,inflammatory state,and intestinal function of weaned piglets challenged with OSO.Methods A total of 28 castrated weaned male piglets with a similar body weight of 10.197 replications per treatment and±0.10 kg were randomly assigned to 4 dietary treatments for 28-d feeding trial with 1 piglet per replicate.Treatments were arranged as a 2×2 factorial with oil type[3%fresh soybean oil(FSO)vs.3%OSO]and dietary RES(0vs.300 mg/kg).Results The results showed that relative to the FSO group,OSO stress tended to decrease the average daily feed intake(ADFI),and decreased the activity levels of lipase,villus/crypt ratio(VCR),the mRNA expression of FABP1,SOD2,IL-10 and ZO-1 in the jejunum,and SOD2,GPX1,occludin and ZO-1 in the colon,the levels of acetic acid in the colonic digesta,whereas up-regulated the mRNA expression of IL-1βand TNF-αin the jejunum(P<0.05).Moreover,dietary supplementation with RES increased ether extract(EE),the activity levels of sucrase,lipase,α-amylase,villus height(VH)and VCR,the mRNA expression of FABP1,SOD2,IL-10 and occludin in the jejunum,and FABP1,PPAR-γ,GPX1,occludin and ZO-1 in the colon,and the abundance of Firmicutes,acetic and propionic acid,but decreased the levels of D-lactic acid in the plasma,the abundance of Bacteroidetes in the colonic digesta of weaned piglets compared to the non-RES group(P<0.05).Meanwhile,in the interaction effect analysis,relative to the OSO group,dietary RES supplementation in the diets supplemented with OSO increased the activity levels of trypsin,VH in the jejunum,the abundance of Actinobacteria,the levels of butyric acid of weaned piglets,but failed to influence the activity levels of trypsin and VH,Actinobacteria abundance,the levels of butyric acid when diets were supplemented with FSO(interaction,P<0.05).Relative to the OSO group,dietary RES supplementation in the diets supplemented with OSO decreased the activity levels of DAO in the plasma of weaned piglets but failed to influence the activity levels of DAO when diets were supplemented with FSO(interaction,P<0.05).Relative to the FSO group,dietary RES supplementation in the diets supplemented with FSO decreased the level of propionic acid,whereas RES supplementation failed to influence the level of propionic acid when the diet was supplemented with OSO(interaction,P<0.01).Conclusions Inclusion of OSO intensified inflammatory states and impaired the intestinal health characteristics of weaned piglets.Dietary RES supplementation improved the antioxidant capacity,anti-inflammatory activity,and intestinal morphology.Further studies showed that the protective effects of RES on gut health could be linked to the decreased abundance of Prevotella_1,Clostridium_sensu_stricto_6,and Prevotellaceae_UCG003 and increased levels of acetic and propionic acid.
基金Project(50725416) supported by the National Natural Science Funds for Distinguished Young Scholars of China
文摘The mechanism of high pressure roll grinding on improvement of compression strength of oxidized hematite pellets was researched by considering their roasting properties.The results indicate that oxidized hematite pellets require higher preheating temperature and longer preheating time to attain required compression strength of pellets compared with the common magnetite oxidized pellets.It is found that when the hematite concentrates are pretreated by high pressure roll grinding(HPRG),the compression strengths of preheated and roasted oxidized hematite pellets get improved even with lower preheating and roasting temperatures and shorter preheating and roasting time.The mechanism for HPRG to improve roasting properties of oxidized pellets were investigated and the cause mainly lies in the increase of micro-sized particles and the decrease of dispersion degree for hematite concentrates,which promotes the hematite concentrate particles to be compacted,the solid-phase crystallization,and finally the formation of Fe2O3 bonding bridges during subsequent high temperature roasting process.
基金the National Key Research and Development Program of China (2021YFA1501302)the National Natural Science Foundation of China (22122808, U20B6002)+1 种基金the Haihe Laboratory of Sustainable Chemical Transformations and the Program of Introducing Talents of Discipline to Universities (BP0618007) for financial supportsupported by the XPLORER PRIZE by Tencent Foundation
文摘The oxygen distribution and evolution within the oxygen carrier exert significant influence on chemical looping processes.This paper describes the influence of oxygen bulk diffusion within FeVO4 oxygen carrier pellets on the chemical looping oxidative propane dehydrogenation(CL-ODH).During CL-ODH,the oxygen concentration at the pellet surface initially decreased and then maintained stable before the final decrease.At the stage with the stable surface oxygen concentration,the reaction showed a stable C3H6 formation rate and high C3H6 selectivity.Therefore,based on Fick’s second law,the oxygen distribution and evolution in the oxygen carrier at this stage were further analyzed.It was found that main reactions of selective oxidation and over-oxidation were controlled by the oxygen bulk diffusion.C3H8 conversion rate kept decreasing during this stage due to the decrease of the oxygen flux caused by the decline of oxygen gradient within the oxygen carrier,while C3H6 selectivity increased due to the decrease of overoxidation.In addition,reaction rates could increase with the propane partial pressure due to the increase of the oxygen gradient within the oxygen carrier until the bulk transfer reached its limit at higher propane partial pressure.This study provides fundamental insights for the diffusion-controlled chemical looping reactions.
基金The authors are very grateful to the Nation Natural Science Foundation of China(No.51974082,No.51901037)the Natural Science Foundation of Liaoning Province,China(No.2019-BS-083)State Key Laboratory of Baiyunobo Rare Earth Resource Researched and Comprehensive Utilization(No.2021H2279)。
文摘Magnesium alloys are more widely used at higher temperatures.However,it is not well known whether oxide layer,produced at high temperature,could show corrosion protection.Thus,the corrosion behaviors of oxidized AZW800 alloy were investigated by hydrogen evolution and electrochemical measurements to evaluate effect of oxide layer on corrosion resistance.The results showed that corrosion of removed oxide layer AZW800 alloy showed characteristic of localized corrosion,leaving randomly bulky pits.While reserved oxide layer AZW800 alloy exhibited a relatively uniform corrosion.The results indicated that oxide layer could hinder corrosion of oxidized AZW800 alloy in the initial period of immersion.While subsequently,aggravated corrosion would occur owing to defects of oxide layer and less protective products film.Besides,present of oxide layer eliminated micro-galvanic couple on alloy surface.The synergistic effect of elimination of micro-galvanic couple on alloy surface and alkalization effect transforms localized corrosion into relatively uniform corrosion of alloys.
