Advanced integrated gasification combined cycle （IGCC） power generation systems require the development of high-temperature, regenerable, desulfurization sorbents capable of removing hydrogen sulfide from coal gasif...Advanced integrated gasification combined cycle （IGCC） power generation systems require the development of high-temperature, regenerable, desulfurization sorbents capable of removing hydrogen sulfide from coal gasifier gas to very low levels. As a sort of effective desufurizer, such as Fe2O3, ZnO and ZnFe2O4, it will endure strong reducing atmosphere in desulfurization process. The reduced degree of desufurizer can have an effect on its desulfurization reactivity. In this paper, Fe2O3, ZnO and ZnFe2O4 were synthesized by precipitation or co-precipitation at constant pH. After aging, washing and drying, the solids were calcined at 800℃. The reduction behaviors of sample were characterized by temperature-programmed reduction （TPR）. It is found that there are two reduction peaks for Fe2O3 in TPR, and whereas no reduction peaks for ZnO are found. The reduction process of ZnFe2O4 prepared by co-precipitation is different from that of Fe2O3. ZnFe2O4 is easier to be reduced than Fe2O3. The activation energy of reduction process for Fe2O3 and ZnFe2O4 is obtained at different reduction periods.展开更多
The effects of basicity and temperature on the reduction process of Hongge high-chromium vanadium-titanium magnetite(HCVTM)sinter were investigated in this work.The main characterization methods of X-ray fluorescence(...The effects of basicity and temperature on the reduction process of Hongge high-chromium vanadium-titanium magnetite(HCVTM)sinter were investigated in this work.The main characterization methods of X-ray fluorescence(XRF),X-ray diffraction(XRD),scanning electron microscope(SEM),and metallographic microscope were employed in this study.In this work,the reduction of HCVTM sinter with different temperature and basicity were experimented.The Fe,FeO,and TiO in reductive samples increase with increasing basicity and temperatures.The increase of basicity and temperature is favorable to the reduction of HCVTM sinter.The Fe phase has out-migration tendency to the surface of sinter while the perovskite and silicate phases have in-migration tendency to the inside of sinter.The reduction degradation index(RDI)decreases while the reduction index(RI)increases with increasing basicity.The RI increases from 67.14%to 82.09%with increasing temperature from 1073 K to 1373 K.展开更多
The differences of reduction behaviors between iron ore lump and pellets were studied by conducting low temperature reduction degradation, static load reduction and droplet tests. These tests simulated the conditions ...The differences of reduction behaviors between iron ore lump and pellets were studied by conducting low temperature reduction degradation, static load reduction and droplet tests. These tests simulated the conditions of reduction temperature and hydrogen-containing gas in COREX. Due to its dense structure and low porosity compared with pellets, lump ore possesses poor reduction degradation index （RDI） and slower reduction rate in early and medium reaction stages ,showing signs of lower strength, lower softening and melting temperatures, as well as a wider melting zone and higher AP. That provides some basis to explain the phenomena of differential pressure rise,metallization decline and more sticking after the usage of lump ore in COREX plant.展开更多
The reduction behavior of pellet was researched through the programming apparatus under simulated con- ditions of oxygen blast furnace （OBF） and traditional blast furnace （T-BF）. The results indicated that compare...The reduction behavior of pellet was researched through the programming apparatus under simulated con- ditions of oxygen blast furnace （OBF） and traditional blast furnace （T-BF）. The results indicated that compared with traditional blast furnace, the reduction starting temperature of pellet decreased by 60 ℃ under oxygen blast furnace condition. The reduction degree of pellet could almost reach 100% under oxygen blast furnace condition when the temperature reached 1100 ℃, whereas it was only 82.49% in traditional blast furnace. The content of carbon in pel- let of oxygen blast furnace was about 5 times more than that of traditional blast furnace. In addition, the microstruc- ture at the periphery and core of pellets after reaction was characterized by means of SEM and EDS.展开更多
The reduction behavior of iron ore pellets containing carbon under non-isothermal condition in the temperature range from 573 to 1373 K was investigated in a laboratory scale setup. The test results show that carbon c...The reduction behavior of iron ore pellets containing carbon under non-isothermal condition in the temperature range from 573 to 1373 K was investigated in a laboratory scale setup. The test results show that carbon content has no obvious effect on reduction degree of composite pellets (C/O mole ratio=1.0) by CO in the temperature range from 573 to 1373 K under linear temperature-rising program; reduction degree of iron ore pellets containing carbon is large in 90%CO-10%CO2 mixture than that of in 100%CO atmosphere or in 80%CO-20%CO2 mixture; the s type temperature-rising program has a better effect than that of linear one in increasing the reduction degree; and reduction degree of slower linear temperature-rising program is greater than that of faster one, but the final reduction degrees, i.e., those at the highest temperature are about the same for various CO partial pressures or temperature-rising programs. The kinetic analysis also shows that the reduction of iron ore-carbon composite pellets by CO or CO-CO2 mixture under non-isothermal condition should be controlled by surface reaction, and the apparent reduction activation energy changes with the reduction progress under various test conditions.展开更多
Iron ore pellets,as one of the main charges of blast furnaces,have a greater impact on the CO_(2)emission reduction and stable operation of blast furnaces.The isothermal reduction behavior of the pellets obtained from...Iron ore pellets,as one of the main charges of blast furnaces,have a greater impact on the CO_(2)emission reduction and stable operation of blast furnaces.The isothermal reduction behavior of the pellets obtained from a Chinese steel plant was studied in the gas mixtures of CO and N_(2).The results showed the reduction process is divided into two stages.The reduction in the initial stage(time t≤40 min)is cooperatively controlled by internal diffusion and interface chemical reactions with the activation energy of 30.19 and 16.67 kJ/mol,respectively.The controlling step of the reduction in the final stage(t>40 min)is internal diffusion with the activation energy of 34.60 kJ/mol.The reduction process can be described by two equations obtained from kinetic calculations.The reduction degree can be predicted under different temperatures and time,and the predicted results showed an excellent correlation with the experimental results.The reduction mechanisms were confirmed by the analysis of the scanning electron microscope equipped with an energy dispersive spectrometer and optical microscope.展开更多
The reduction behaviors of FeO·V2O3 and FeO·Cr2O3 during coal-based direct reduction have a decisive impact on the efficient utilization of high-chromium vanadium-bearing titanomagnetite concentrates. The ef...The reduction behaviors of FeO·V2O3 and FeO·Cr2O3 during coal-based direct reduction have a decisive impact on the efficient utilization of high-chromium vanadium-bearing titanomagnetite concentrates. The effects of molar ratio of C to Fe n(C)/n(Fe) and temperature on the behaviors of vanadium and chromium during direct reduction and magnetic separation were investigated. The reduced samples were characterized by X-ray diffraction(XRD), scanning election microscopy(SEM) and energy dispersive spectrometry(EDS) techniques. Experimental results indicate that the recoveries of vanadium and chromium rapidly increase from 10.0% and 9.6% to 45.3% and 74.3%, respectively, as the n(C)/n(Fe) increases from 0.8 to 1.4. At n(C)/n(Fe) of 0.8, the recoveries of vanadium and chromium are always lower than 10.0% in the whole temperature range of 1100-1250 °C. However, at n(C)/n(Fe) of 1.2, the recoveries of vanadium and chromium considerably increase from 17.8% and 33.8% to 42.4% and 76.0%, respectively, as the temperature increases from 1100 °C to 1250 °C. At n(C)/n(Fe) lower than 0.8, most of the FeO·V2O3 and FeO·Cr2O3 are not reduced to carbides because of the lack of carbonaceous reductants, and the temperature has little effect on the reduction behaviors of FeO·V2O3 and FeO·Cr2O3, resulting in very low recoveries of vanadium and chromium during magnetic separation. However, at higher n(C)/n(Fe), the reduction rates of FeO·V2O3 and FeO·Cr2O3 increase significatly because of the excess amount of carbonaceous reductants. Moreover, higher temperatures largely induce the reduction of FeO·V2O3 and FeO·Cr2O3 to carbides. The newly formed carbides are then dissolved in the γ(FCC) phase, and recovered accompanied with the metallic iron during magnetic separation.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 magnetization reduction of hematite using biomass waste can effectively utilize waste and reduce CO_(2) emission to achieve the goals of carbon peaking and carbon neutrality.The effects of temperatures on suspensi...The magnetization reduction of hematite using biomass waste can effectively utilize waste and reduce CO_(2) emission to achieve the goals of carbon peaking and carbon neutrality.The effects of temperatures on suspension magnetization roasting of hematite using biomass waste for evolved gases have been investigated using TG-FTIR,Py-GC/MS and gas composition analyzer.The mixture reduction process is divided into four stages.In the temperature range of 200-450℃ for mixture,the release of CO_(2),acids,and ketones is dominated in gases products.The yield and concentration of small molecules reducing gases increase when the temperature increases from 450 to 900℃.At 700℃,the volume concentrations of CO,H_(2) and CH_(4) peak at 8.91%,8.90% and 4.91%,respectively.During the suspension magnetization roasting process,an optimal iron concentrate with an iron grade of 70.86%,a recovery of 98.66% and a magnetic conversion of 45.70% is obtained at 700℃.Therefore,the magnetization reduction could react greatly in the temperature range of 600 to 700℃ owing to the suitable reducing gases.This study shows a detail gaseous evolution of roasting temperature and provides a new insight for studying the reduction process of hematite using biomass waste.展开更多
To investigate how the physicochemical properties and NH3‐selective catalytic reduction(NH3‐SCR)performance of supported ceria‐based catalysts are influenced as a function of support type,a series of CeO2/SiO2,CeO2...To investigate how the physicochemical properties and NH3‐selective catalytic reduction(NH3‐SCR)performance of supported ceria‐based catalysts are influenced as a function of support type,a series of CeO2/SiO2,CeO2/γ‐Al2O3,CeO2/ZrO2,and CeO2/TiO2catalysts were prepared.The physicochemical properties were probed by means of X‐ray diffraction,Raman spectroscopy,Brunauer‐Emmett‐Teller surface area measurements,X‐ray photoelectron spectroscopy,H2‐temperature programmed reduction,and NH3‐temperature programmed desorption.Furthermore,the supported ceria‐based catalysts'catalytic performance and H2O+SO2tolerance were evaluated by the NH3‐SCR model reaction.The results indicate that out of the supported ceria‐based catalysts studied,the CeO2/γ‐Al2O3catalyst exhibits the highest catalytic activity as a result of having a high relative Ce3+/Ce4+ratio,optimum reduction behavior,and the largest total acid site concentration.Finally,the CeO2/γ‐Al2O3catalyst also presents excellent H2O+SO2tolerance during the NH3‐SCR process.展开更多
AIM:Considerable controversy surrounds the adoption of endoscopic sphincterotomy(ES)to facilitate the placement of 10F plastic stents(PS)and to reduce the risk of pancreatitis The aim of the study was to assess the po...AIM:Considerable controversy surrounds the adoption of endoscopic sphincterotomy(ES)to facilitate the placement of 10F plastic stents(PS)and to reduce the risk of pancreatitis The aim of the study was to assess the possible advantages of ES before PS placement. METHODS:From 3/1996 to 6/2001,172 consecutive patients, who underwent placement of a single 10F-polyethylene stent for inoperable malignant strictures of the common bile duct,were randomly assigned to 2 groups.In group A(96 patients),a ES was performed before PS placement In Group B,96 patients had PS directly.Early complications(within 30 d)and late effects(from 30 d to stent replacement)were assessed.Patency interval was defined as the period between PS placement and obstruction or death.The success of stent replacement in the 2 groups was evaluated. RESULTS:Stent insertion was successful in 95.8%(92/96) of the pts in group A and in 93.7%(90/96)of the patients in group B(P>0.05).Early complications were more frequent in patients who underwent ES(6.5% vs4.4%)but the data were not significant(P>0.05).In group A pancreatitis developed in two patients and bleeding in three;whereas pancreatitis occurred in 2 patients in group B.Complications were managed conservatively.No procedure related mortality occurred.All late complications were acute cholangitis due to stent occlusion.We performed a stent replacement in 87 patients that was successful in 84 cases without differences between groups. CONCLUSION:Sphincterotomy does not seem to be necessary for placement of 10F-PS in patients with malignant common bile duct obstruction.展开更多
The influence of basicity on the metallurgical performances and reduction characteristics of fired super high-grade magnetite pellets under the simulated shaft furnace gas conditions was investigated.The fired pellets...The influence of basicity on the metallurgical performances and reduction characteristics of fired super high-grade magnetite pellets under the simulated shaft furnace gas conditions was investigated.The fired pellets in the basicity range of 0.09(natural basicity)to 1.00 show superior reducibility and low-temperature disintegration performance.However,in the basicity range of 0.20–0.80,the abnormal swelling of the fired pellets occurs.Improving basicity from 0.09 to 0.40 promotes the generation of low melting point slag phases and lower porosity of fired pellets,and accelerates the growth and densification of hematite crystals,impeding the reduction of hematite particles and the formation of metallic iron shell.In addition,the slags that distribute between the hematite particles absorb the reduction stresses by increased distances between the particles during the reduction process,which leads to the large reduction swelling of pellets.展开更多
Wustite-based catalyst for ammonia synthesis exhibits extremely high activity and easy to reduction under a wide range of conditions. The reaction kinetics of ammonia synthesis can be illustrated perfectly by both the...Wustite-based catalyst for ammonia synthesis exhibits extremely high activity and easy to reduction under a wide range of conditions. The reaction kinetics of ammonia synthesis can be illustrated perfectly by both the classical Temkin-Pyzhev and modified Temkin equations with optimized a of 0.5. The pre-exponent factors and activation energies at the pressures of 8.0 and 15.0MPa are respectively k0 = 1.09 x 1015, 7.35 X 1014Pa0.5.s-1, and E = 156.6, 155.5kJ-mol-1 derived from the classical Temkin-Phyzhev equation, as well as k0 = 2.45 X 1014, 1.83 X 1014Pa0.5s-1, and E = 147.7, 147.2kJ-mol-1 derived from the modified Temkin equation. Although the degree of reduction under isothermal condition is primarily dependent upon temperature, low pressure seems to be imperative for reduction under high temperature and low space velocity to be considered as a high activity catalyst. The reduction behavior with dry feed gas can be illustrated perfectly by the shrinking-sphere-particle model, by which the reduction-rate constants of 4248exp (-71680/KT) and 644exp (-87260/RT) were obtained for the powder (0.045-0.054mm) and irregular shape (nominal diameter 3.17 mm) catalysts respectively. The significant effect of particle size on reduction rate was observed, therefore, it is important to take into account the influence of particle size on reduction for the optimization of reduction process in industry.展开更多
Objective:To compare the diagnostic value of the ABCD2 and ABCD3-栺scoring systems in predicting the development of a 30-day neurological event in adult patients with transient ischemic attack(TIA)presenting to the em...Objective:To compare the diagnostic value of the ABCD2 and ABCD3-栺scoring systems in predicting the development of a 30-day neurological event in adult patients with transient ischemic attack(TIA)presenting to the emergency department.Methods:The study was observational and prospective and was conducted in a single center.The diagnostic values of the ABCD2 and ABCD3-栺scores in predicting a neurological event within one month were compared in patients diagnosed with TIA in the emergency department.Results:A statistically significant difference was observed between groups with or without stroke within one month in terms of both the ABCD2 and ABCD3-栺scores(P=0.044 and P=0.029,respectively).There was no statistically significant difference between the patients with and without a recurrent TIA within one month in relation to the ABCD2 score(P=0.934),but a statistically significant difference was found in the ABCD3-栺scores of these groups(P<0.001).Conclusions:Both the ABCD2 and ABCD3-栺scoring systems could predict ischemic stroke within 30 days of TIA,the ABCD3-栺score is more effective than the ABCD2 score in the prediction of TIA recurrence.展开更多
基金the Ministry of Science and Technology of China under the Grant No. G2005CB221203the Natural Science Foundation of China(20776092)
文摘Advanced integrated gasification combined cycle （IGCC） power generation systems require the development of high-temperature, regenerable, desulfurization sorbents capable of removing hydrogen sulfide from coal gasifier gas to very low levels. As a sort of effective desufurizer, such as Fe2O3, ZnO and ZnFe2O4, it will endure strong reducing atmosphere in desulfurization process. The reduced degree of desufurizer can have an effect on its desulfurization reactivity. In this paper, Fe2O3, ZnO and ZnFe2O4 were synthesized by precipitation or co-precipitation at constant pH. After aging, washing and drying, the solids were calcined at 800℃. The reduction behaviors of sample were characterized by temperature-programmed reduction （TPR）. It is found that there are two reduction peaks for Fe2O3 in TPR, and whereas no reduction peaks for ZnO are found. The reduction process of ZnFe2O4 prepared by co-precipitation is different from that of Fe2O3. ZnFe2O4 is easier to be reduced than Fe2O3. The activation energy of reduction process for Fe2O3 and ZnFe2O4 is obtained at different reduction periods.
基金Project(2013CB632603)supported by the National Basic Research Program of ChinaProject(2015BAB19B02)supported by the National Key Technology R&D Program of ChinaProjects(51674084,51174051,51574082)supported by National Natural Science Foundation of China
文摘The effects of basicity and temperature on the reduction process of Hongge high-chromium vanadium-titanium magnetite(HCVTM)sinter were investigated in this work.The main characterization methods of X-ray fluorescence(XRF),X-ray diffraction(XRD),scanning electron microscope(SEM),and metallographic microscope were employed in this study.In this work,the reduction of HCVTM sinter with different temperature and basicity were experimented.The Fe,FeO,and TiO in reductive samples increase with increasing basicity and temperatures.The increase of basicity and temperature is favorable to the reduction of HCVTM sinter.The Fe phase has out-migration tendency to the surface of sinter while the perovskite and silicate phases have in-migration tendency to the inside of sinter.The reduction degradation index(RDI)decreases while the reduction index(RI)increases with increasing basicity.The RI increases from 67.14%to 82.09%with increasing temperature from 1073 K to 1373 K.
基金sponsored by Shanghai Rising-Star Program(B type 11QB1400200)
文摘The differences of reduction behaviors between iron ore lump and pellets were studied by conducting low temperature reduction degradation, static load reduction and droplet tests. These tests simulated the conditions of reduction temperature and hydrogen-containing gas in COREX. Due to its dense structure and low porosity compared with pellets, lump ore possesses poor reduction degradation index （RDI） and slower reduction rate in early and medium reaction stages ,showing signs of lower strength, lower softening and melting temperatures, as well as a wider melting zone and higher AP. That provides some basis to explain the phenomena of differential pressure rise,metallization decline and more sticking after the usage of lump ore in COREX plant.
基金Sponsored by National Basic Research Program of China(2012CB720401)Natural Science Foundation of China and Baosteel(51134008)
文摘The reduction behavior of pellet was researched through the programming apparatus under simulated con- ditions of oxygen blast furnace （OBF） and traditional blast furnace （T-BF）. The results indicated that compared with traditional blast furnace, the reduction starting temperature of pellet decreased by 60 ℃ under oxygen blast furnace condition. The reduction degree of pellet could almost reach 100% under oxygen blast furnace condition when the temperature reached 1100 ℃, whereas it was only 82.49% in traditional blast furnace. The content of carbon in pel- let of oxygen blast furnace was about 5 times more than that of traditional blast furnace. In addition, the microstruc- ture at the periphery and core of pellets after reaction was characterized by means of SEM and EDS.
文摘The reduction behavior of iron ore pellets containing carbon under non-isothermal condition in the temperature range from 573 to 1373 K was investigated in a laboratory scale setup. The test results show that carbon content has no obvious effect on reduction degree of composite pellets (C/O mole ratio=1.0) by CO in the temperature range from 573 to 1373 K under linear temperature-rising program; reduction degree of iron ore pellets containing carbon is large in 90%CO-10%CO2 mixture than that of in 100%CO atmosphere or in 80%CO-20%CO2 mixture; the s type temperature-rising program has a better effect than that of linear one in increasing the reduction degree; and reduction degree of slower linear temperature-rising program is greater than that of faster one, but the final reduction degrees, i.e., those at the highest temperature are about the same for various CO partial pressures or temperature-rising programs. The kinetic analysis also shows that the reduction of iron ore-carbon composite pellets by CO or CO-CO2 mixture under non-isothermal condition should be controlled by surface reaction, and the apparent reduction activation energy changes with the reduction progress under various test conditions.
基金support from the National Natural Science Foundation of China(No.52174300)Natural Science Foundation of Chongqing,China(Nos.cstc2020jcyj-msxmX0583 and cstc2021jcyj-msxmX1004)+1 种基金Chongqing Talent Plan Project(No.cstc2021ycjh-bgzxm0211)Chongqing Doctoral"Through Train"Project(No.sl202100000343).T。
文摘Iron ore pellets,as one of the main charges of blast furnaces,have a greater impact on the CO_(2)emission reduction and stable operation of blast furnaces.The isothermal reduction behavior of the pellets obtained from a Chinese steel plant was studied in the gas mixtures of CO and N_(2).The results showed the reduction process is divided into two stages.The reduction in the initial stage(time t≤40 min)is cooperatively controlled by internal diffusion and interface chemical reactions with the activation energy of 30.19 and 16.67 kJ/mol,respectively.The controlling step of the reduction in the final stage(t>40 min)is internal diffusion with the activation energy of 34.60 kJ/mol.The reduction process can be described by two equations obtained from kinetic calculations.The reduction degree can be predicted under different temperatures and time,and the predicted results showed an excellent correlation with the experimental results.The reduction mechanisms were confirmed by the analysis of the scanning electron microscope equipped with an energy dispersive spectrometer and optical microscope.
基金Projects(2013CB632601,2013CB632604)supported by the National Basic Research Program of ChinaProject(51125018)supported by the National Science Foundation for Distinguished Young Scholars of China+1 种基金Project(KGZD-EW-201-2)supported by the Key Research Program of the Chinese Academy of SciencesProjects(51374191,21106167,51104139)supported by the National Natural Science Foundation of China
文摘The reduction behaviors of FeO·V2O3 and FeO·Cr2O3 during coal-based direct reduction have a decisive impact on the efficient utilization of high-chromium vanadium-bearing titanomagnetite concentrates. The effects of molar ratio of C to Fe n(C)/n(Fe) and temperature on the behaviors of vanadium and chromium during direct reduction and magnetic separation were investigated. The reduced samples were characterized by X-ray diffraction(XRD), scanning election microscopy(SEM) and energy dispersive spectrometry(EDS) techniques. Experimental results indicate that the recoveries of vanadium and chromium rapidly increase from 10.0% and 9.6% to 45.3% and 74.3%, respectively, as the n(C)/n(Fe) increases from 0.8 to 1.4. At n(C)/n(Fe) of 0.8, the recoveries of vanadium and chromium are always lower than 10.0% in the whole temperature range of 1100-1250 °C. However, at n(C)/n(Fe) of 1.2, the recoveries of vanadium and chromium considerably increase from 17.8% and 33.8% to 42.4% and 76.0%, respectively, as the temperature increases from 1100 °C to 1250 °C. At n(C)/n(Fe) lower than 0.8, most of the FeO·V2O3 and FeO·Cr2O3 are not reduced to carbides because of the lack of carbonaceous reductants, and the temperature has little effect on the reduction behaviors of FeO·V2O3 and FeO·Cr2O3, resulting in very low recoveries of vanadium and chromium during magnetic separation. However, at higher n(C)/n(Fe), the reduction rates of FeO·V2O3 and FeO·Cr2O3 increase significatly because of the excess amount of carbonaceous reductants. Moreover, higher temperatures largely induce the reduction of FeO·V2O3 and FeO·Cr2O3 to carbides. The newly formed carbides are then dissolved in the γ(FCC) phase, and recovered accompanied with the metallic iron during magnetic separation.
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(52022019)supported by the National Natural Science Foundation of China。
文摘The magnetization reduction of hematite using biomass waste can effectively utilize waste and reduce CO_(2) emission to achieve the goals of carbon peaking and carbon neutrality.The effects of temperatures on suspension magnetization roasting of hematite using biomass waste for evolved gases have been investigated using TG-FTIR,Py-GC/MS and gas composition analyzer.The mixture reduction process is divided into four stages.In the temperature range of 200-450℃ for mixture,the release of CO_(2),acids,and ketones is dominated in gases products.The yield and concentration of small molecules reducing gases increase when the temperature increases from 450 to 900℃.At 700℃,the volume concentrations of CO,H_(2) and CH_(4) peak at 8.91%,8.90% and 4.91%,respectively.During the suspension magnetization roasting process,an optimal iron concentrate with an iron grade of 70.86%,a recovery of 98.66% and a magnetic conversion of 45.70% is obtained at 700℃.Therefore,the magnetization reduction could react greatly in the temperature range of 600 to 700℃ owing to the suitable reducing gases.This study shows a detail gaseous evolution of roasting temperature and provides a new insight for studying the reduction process of hematite using biomass waste.
基金supported by the National Natural Science Foundation of China (21507130)the Chongqing Science and Technology Commission (cstc2016jcyjA 0070,cstc2014pt-gc20002,cstc2014yykfC 20003,cstckjcxljrc13)the Open Project Program of Chongqing Key Laboratory of Ca-talysis and Functional Organic Molecules from Chongqing Technology and Business University (1456029)~~
文摘To investigate how the physicochemical properties and NH3‐selective catalytic reduction(NH3‐SCR)performance of supported ceria‐based catalysts are influenced as a function of support type,a series of CeO2/SiO2,CeO2/γ‐Al2O3,CeO2/ZrO2,and CeO2/TiO2catalysts were prepared.The physicochemical properties were probed by means of X‐ray diffraction,Raman spectroscopy,Brunauer‐Emmett‐Teller surface area measurements,X‐ray photoelectron spectroscopy,H2‐temperature programmed reduction,and NH3‐temperature programmed desorption.Furthermore,the supported ceria‐based catalysts'catalytic performance and H2O+SO2tolerance were evaluated by the NH3‐SCR model reaction.The results indicate that out of the supported ceria‐based catalysts studied,the CeO2/γ‐Al2O3catalyst exhibits the highest catalytic activity as a result of having a high relative Ce3+/Ce4+ratio,optimum reduction behavior,and the largest total acid site concentration.Finally,the CeO2/γ‐Al2O3catalyst also presents excellent H2O+SO2tolerance during the NH3‐SCR process.
文摘AIM:Considerable controversy surrounds the adoption of endoscopic sphincterotomy(ES)to facilitate the placement of 10F plastic stents(PS)and to reduce the risk of pancreatitis The aim of the study was to assess the possible advantages of ES before PS placement. METHODS:From 3/1996 to 6/2001,172 consecutive patients, who underwent placement of a single 10F-polyethylene stent for inoperable malignant strictures of the common bile duct,were randomly assigned to 2 groups.In group A(96 patients),a ES was performed before PS placement In Group B,96 patients had PS directly.Early complications(within 30 d)and late effects(from 30 d to stent replacement)were assessed.Patency interval was defined as the period between PS placement and obstruction or death.The success of stent replacement in the 2 groups was evaluated. RESULTS:Stent insertion was successful in 95.8%(92/96) of the pts in group A and in 93.7%(90/96)of the patients in group B(P>0.05).Early complications were more frequent in patients who underwent ES(6.5% vs4.4%)but the data were not significant(P>0.05).In group A pancreatitis developed in two patients and bleeding in three;whereas pancreatitis occurred in 2 patients in group B.Complications were managed conservatively.No procedure related mortality occurred.All late complications were acute cholangitis due to stent occlusion.We performed a stent replacement in 87 patients that was successful in 84 cases without differences between groups. CONCLUSION:Sphincterotomy does not seem to be necessary for placement of 10F-PS in patients with malignant common bile duct obstruction.
基金The authors want to express their gratitude for the financial support from the National Natural Science Foundation of China(No.52004075)Science and Technology Planning Projects of Guizhou Province(No.ZK[2021]262)+1 种基金Program Foundation for Talents of Guizhou University(No.(2020)15)the Hunan Provincial Co-innovation Center for Clean and Efficient Utilization of Strategic Metal Mineral Resources.
文摘The influence of basicity on the metallurgical performances and reduction characteristics of fired super high-grade magnetite pellets under the simulated shaft furnace gas conditions was investigated.The fired pellets in the basicity range of 0.09(natural basicity)to 1.00 show superior reducibility and low-temperature disintegration performance.However,in the basicity range of 0.20–0.80,the abnormal swelling of the fired pellets occurs.Improving basicity from 0.09 to 0.40 promotes the generation of low melting point slag phases and lower porosity of fired pellets,and accelerates the growth and densification of hematite crystals,impeding the reduction of hematite particles and the formation of metallic iron shell.In addition,the slags that distribute between the hematite particles absorb the reduction stresses by increased distances between the particles during the reduction process,which leads to the large reduction swelling of pellets.
基金Supported by the National Natural Science Foundation of China (No. 29706011), the Natural Science Foundation of Zhejiang Province for the distinguished young scholars (No. RC9702) and the Ninth-five Key Project of China (No. 96-550-02-01).
文摘Wustite-based catalyst for ammonia synthesis exhibits extremely high activity and easy to reduction under a wide range of conditions. The reaction kinetics of ammonia synthesis can be illustrated perfectly by both the classical Temkin-Pyzhev and modified Temkin equations with optimized a of 0.5. The pre-exponent factors and activation energies at the pressures of 8.0 and 15.0MPa are respectively k0 = 1.09 x 1015, 7.35 X 1014Pa0.5.s-1, and E = 156.6, 155.5kJ-mol-1 derived from the classical Temkin-Phyzhev equation, as well as k0 = 2.45 X 1014, 1.83 X 1014Pa0.5s-1, and E = 147.7, 147.2kJ-mol-1 derived from the modified Temkin equation. Although the degree of reduction under isothermal condition is primarily dependent upon temperature, low pressure seems to be imperative for reduction under high temperature and low space velocity to be considered as a high activity catalyst. The reduction behavior with dry feed gas can be illustrated perfectly by the shrinking-sphere-particle model, by which the reduction-rate constants of 4248exp (-71680/KT) and 644exp (-87260/RT) were obtained for the powder (0.045-0.054mm) and irregular shape (nominal diameter 3.17 mm) catalysts respectively. The significant effect of particle size on reduction rate was observed, therefore, it is important to take into account the influence of particle size on reduction for the optimization of reduction process in industry.
文摘Objective:To compare the diagnostic value of the ABCD2 and ABCD3-栺scoring systems in predicting the development of a 30-day neurological event in adult patients with transient ischemic attack(TIA)presenting to the emergency department.Methods:The study was observational and prospective and was conducted in a single center.The diagnostic values of the ABCD2 and ABCD3-栺scores in predicting a neurological event within one month were compared in patients diagnosed with TIA in the emergency department.Results:A statistically significant difference was observed between groups with or without stroke within one month in terms of both the ABCD2 and ABCD3-栺scores(P=0.044 and P=0.029,respectively).There was no statistically significant difference between the patients with and without a recurrent TIA within one month in relation to the ABCD2 score(P=0.934),but a statistically significant difference was found in the ABCD3-栺scores of these groups(P<0.001).Conclusions:Both the ABCD2 and ABCD3-栺scoring systems could predict ischemic stroke within 30 days of TIA,the ABCD3-栺score is more effective than the ABCD2 score in the prediction of TIA recurrence.
