A molten salt method was developed to prepare porous La1‐xSrxMn0.8Fe0.2O3 （0≤ x ≤ 0.6） micro‐spheres using hierarchical porous δ‐MnO2 microspheres as a template in eutectic NaNO3‐KNO3. X‐ray diffraction patt...A molten salt method was developed to prepare porous La1‐xSrxMn0.8Fe0.2O3 （0≤ x ≤ 0.6） micro‐spheres using hierarchical porous δ‐MnO2 microspheres as a template in eutectic NaNO3‐KNO3. X‐ray diffraction patterns showed that single phase LaMn0.8Fe0.2O3 with good crystallinity was syn‐thesized at 450℃ after 4 h. Transmission electron microscope images exhibited that the LaMn0.8Fe0.2O3 sample obtained at 450？？ after 4 h possessed a porous spherical morphology com‐posed of aggregated nanocrystallites. Field emission scanning electron microscope images indicated that the growth of the porous LaMn0.8Fe0.2O3 microspheres has two stages. SEM pictures showed that a higher calcination temperature than 450？？ had an adverse effect on the formation of a po‐rous spherical structure. The LaMn0.8Fe0.2O3 sample obtained at 450？？ after 4 h displayed a high BET surface area of 55.73 m2/g with a pore size of 9.38 nm. Fourier transform infrared spectra suggested that Sr2＋ions entered the A sites and induced a decrease of the binding energy between Mn and O. The CO conversion with the La1‐xSrxMn0.8Fe0.2O3 （0≤x≤0.6） samples indicated that the La0.4Sr0.6Mn0.8Fe0.2O3 sample had the best catalytic activity and stability. Further analysis by X‐ray photoelectron spectroscopy demonstrated that Sr2＋doping altered the content of Mn4＋ions, oxygen vacancies and adsorbed oxygen species on the surface, which affected the catalytic performance for CO oxidation.展开更多
With CO combustion promoters, the role of combustion air flow rate for concerns of economics and control is important. The combustion air is conceptually divided to three parts: the air consumed by coke burning,the ai...With CO combustion promoters, the role of combustion air flow rate for concerns of economics and control is important. The combustion air is conceptually divided to three parts: the air consumed by coke burning,the air consumed by CO combustion and the air unreacted. A mathematical model of a fluid catalytic cracking(FCC)unit, which includes a quantitative correlation of CO heterogeneous combustion and the amount of CO combustion promoters, is introduced to investigate the effects of promoters on the three parts of combustion air. The results show that the air consumed by coke burning is almost linear to combustion air flow rate, while the air consumed by CO combustion promoters tends to saturate as combustion air flow rate increases, indicating that higher air flow rate can only be used as a manipulated variable to control the oxygen content for an economic concern.展开更多
Reburning technology is one of the most cost-effective NOx reduction strategies for coal combustion systems. In this paper, a nitric oxide submodel incorporated into a comprehensive coal combustion model was developed...Reburning technology is one of the most cost-effective NOx reduction strategies for coal combustion systems. In this paper, a nitric oxide submodel incorporated into a comprehensive coal combustion model was developed for predicting NOx reduction in a 93 kW laboratory-scale coal combustion furnace by reburning. This NO submodel, including reburning mechanism, requires the solution of only two transport equations to model the behavior of NO reduction in the reburning process. A number of experiments have been performed in the same furnace, and the experimental data obtained from the optimized reburn configuration was used to validate the model. Measurements and predictions both show above 50% reduction of NO emissions for the optimized reburning process. Profile comparisons show that the predicted temperature and oxygen concentration match well with the measurements, and the general trend of predicted NO concentration is very similar to that measured. The results of this study show that the present nitric oxide submodel depicts quite well the observed behaviour of NO annihilation in the reburning process. It is expected that this usable and computationally economic model represents a useful tool to simulate the gaseous fuel reburning process for the researchers concerned with practical combustors.展开更多
The nitric oxide and cyclic GMP production in myocardium early after burn injury in rats were investi- gated. Nitric oxide synthase activity was measured in cytosols from the left ventricular wall of burned rats. Cyto...The nitric oxide and cyclic GMP production in myocardium early after burn injury in rats were investi- gated. Nitric oxide synthase activity was measured in cytosols from the left ventricular wall of burned rats. Cytosols from the control group animals were shown to contain mainly Ca2+ dependent nitric oxide synthase （cNOS） with small amount of Ca2+ independent nitric oxide synthase （iNOS）. Following burn injury, there was a marked increase in iNOS activity with a peak at sh post-burn, however, myocardial cNOS ac- tivity was found to decline obviously. Parallel to iNOS induction there was a significant increase in myocar- dial nitric oxide and cyclic GMP production. All these changes were alleviated by treatment of the rats with dexamethasone. Since increases in cyclic GMP levels in the heart were associated with reduced myocardial contractility, it is possible that enhanced production of nitric oxide by a Ca2+, independent NO synthase ac- counts, at least in part, for the depression of myocardial contractility seen in burn animals and patients.展开更多
An experimental study was carried out in a small-scale furnace to investigate the performance, such as NOx emission, enhancement of heat transfer, uniformity of temperature, and etc., of oscillating combustion applied...An experimental study was carried out in a small-scale furnace to investigate the performance, such as NOx emission, enhancement of heat transfer, uniformity of temperature, and etc., of oscillating combustion applied in radiant tube burner sy stem for heat treatment furnace. A premixed type burner and a solenoid type oscillating control valve were designed and used. The fuel was used commercial LPG in this study and the fuel flow was oscillated by periodically opening and shutoff of the solenoid valve. From the tests, it was found that NOx emission, compared to no oscillation, could be reduced by 32% at 2.0 Hz. However, as oscillating frequency was increased, abatement of NOx emission was gradually reduced. At the high NOx abatement of 1.0 Hz, carbon monoxide was emitted above 10,000 ppm. Although rate of NOx abatement was low, oscillation condition of 2.5 Hz and duty ratio of 10-30% was recommended for low carbon monoxide emission. From the measurement of furnace heating time from 100 ℃ to 720 ℃, it was shown that heat transfer was increased by 11.5% at 2 Hz oscillating frequency. Temperature distribution of radiant tube surface was more uniform at 2 Hz oscillating frequency with drop of the peak temperature and rise of low temperature. From these results, it was confirmed that oscillating combustion was useful in radiant tube burner system.展开更多
基金supported by the National Science Foundation for Young Scientists of China (51202171)~~
文摘A molten salt method was developed to prepare porous La1‐xSrxMn0.8Fe0.2O3 （0≤ x ≤ 0.6） micro‐spheres using hierarchical porous δ‐MnO2 microspheres as a template in eutectic NaNO3‐KNO3. X‐ray diffraction patterns showed that single phase LaMn0.8Fe0.2O3 with good crystallinity was syn‐thesized at 450℃ after 4 h. Transmission electron microscope images exhibited that the LaMn0.8Fe0.2O3 sample obtained at 450？？ after 4 h possessed a porous spherical morphology com‐posed of aggregated nanocrystallites. Field emission scanning electron microscope images indicated that the growth of the porous LaMn0.8Fe0.2O3 microspheres has two stages. SEM pictures showed that a higher calcination temperature than 450？？ had an adverse effect on the formation of a po‐rous spherical structure. The LaMn0.8Fe0.2O3 sample obtained at 450？？ after 4 h displayed a high BET surface area of 55.73 m2/g with a pore size of 9.38 nm. Fourier transform infrared spectra suggested that Sr2＋ions entered the A sites and induced a decrease of the binding energy between Mn and O. The CO conversion with the La1‐xSrxMn0.8Fe0.2O3 （0≤x≤0.6） samples indicated that the La0.4Sr0.6Mn0.8Fe0.2O3 sample had the best catalytic activity and stability. Further analysis by X‐ray photoelectron spectroscopy demonstrated that Sr2＋doping altered the content of Mn4＋ions, oxygen vacancies and adsorbed oxygen species on the surface, which affected the catalytic performance for CO oxidation.
基金Supported by the National Natural Science Foundation of China(21006127)the National Basic Research Program of China(2012CB720500)
文摘With CO combustion promoters, the role of combustion air flow rate for concerns of economics and control is important. The combustion air is conceptually divided to three parts: the air consumed by coke burning,the air consumed by CO combustion and the air unreacted. A mathematical model of a fluid catalytic cracking(FCC)unit, which includes a quantitative correlation of CO heterogeneous combustion and the amount of CO combustion promoters, is introduced to investigate the effects of promoters on the three parts of combustion air. The results show that the air consumed by coke burning is almost linear to combustion air flow rate, while the air consumed by CO combustion promoters tends to saturate as combustion air flow rate increases, indicating that higher air flow rate can only be used as a manipulated variable to control the oxygen content for an economic concern.
基金Project 2004CB217704-4 supported by the Special Funds for Major State Basic Research Projects of China and 306012 by the Key Grant Project of Chinese Ministry of Education
文摘Reburning technology is one of the most cost-effective NOx reduction strategies for coal combustion systems. In this paper, a nitric oxide submodel incorporated into a comprehensive coal combustion model was developed for predicting NOx reduction in a 93 kW laboratory-scale coal combustion furnace by reburning. This NO submodel, including reburning mechanism, requires the solution of only two transport equations to model the behavior of NO reduction in the reburning process. A number of experiments have been performed in the same furnace, and the experimental data obtained from the optimized reburn configuration was used to validate the model. Measurements and predictions both show above 50% reduction of NO emissions for the optimized reburning process. Profile comparisons show that the predicted temperature and oxygen concentration match well with the measurements, and the general trend of predicted NO concentration is very similar to that measured. The results of this study show that the present nitric oxide submodel depicts quite well the observed behaviour of NO annihilation in the reburning process. It is expected that this usable and computationally economic model represents a useful tool to simulate the gaseous fuel reburning process for the researchers concerned with practical combustors.
文摘The nitric oxide and cyclic GMP production in myocardium early after burn injury in rats were investi- gated. Nitric oxide synthase activity was measured in cytosols from the left ventricular wall of burned rats. Cytosols from the control group animals were shown to contain mainly Ca2+ dependent nitric oxide synthase （cNOS） with small amount of Ca2+ independent nitric oxide synthase （iNOS）. Following burn injury, there was a marked increase in iNOS activity with a peak at sh post-burn, however, myocardial cNOS ac- tivity was found to decline obviously. Parallel to iNOS induction there was a significant increase in myocar- dial nitric oxide and cyclic GMP production. All these changes were alleviated by treatment of the rats with dexamethasone. Since increases in cyclic GMP levels in the heart were associated with reduced myocardial contractility, it is possible that enhanced production of nitric oxide by a Ca2+, independent NO synthase ac- counts, at least in part, for the depression of myocardial contractility seen in burn animals and patients.
文摘An experimental study was carried out in a small-scale furnace to investigate the performance, such as NOx emission, enhancement of heat transfer, uniformity of temperature, and etc., of oscillating combustion applied in radiant tube burner sy stem for heat treatment furnace. A premixed type burner and a solenoid type oscillating control valve were designed and used. The fuel was used commercial LPG in this study and the fuel flow was oscillated by periodically opening and shutoff of the solenoid valve. From the tests, it was found that NOx emission, compared to no oscillation, could be reduced by 32% at 2.0 Hz. However, as oscillating frequency was increased, abatement of NOx emission was gradually reduced. At the high NOx abatement of 1.0 Hz, carbon monoxide was emitted above 10,000 ppm. Although rate of NOx abatement was low, oscillation condition of 2.5 Hz and duty ratio of 10-30% was recommended for low carbon monoxide emission. From the measurement of furnace heating time from 100 ℃ to 720 ℃, it was shown that heat transfer was increased by 11.5% at 2 Hz oscillating frequency. Temperature distribution of radiant tube surface was more uniform at 2 Hz oscillating frequency with drop of the peak temperature and rise of low temperature. From these results, it was confirmed that oscillating combustion was useful in radiant tube burner system.
