Catalytic C–H activation-initiated annulation reactions have emerged as a versatile strategy for the efficient construction of diverse ring structural units and complex cyclic molecules in synthetic chemistry.Herein,...Catalytic C–H activation-initiated annulation reactions have emerged as a versatile strategy for the efficient construction of diverse ring structural units and complex cyclic molecules in synthetic chemistry.Herein,we describe a new Rh(Ⅲ)-catalyzed C–H activation-initiated transdiannulation reaction of N,Ndimethyl enaminones with gem-difluorocyclopropenes in the presence of H_(2)O,enabling a facile and oxygen transfer access to ring-fluorinated tricyclicγ-lactones with a 6-5 ring-junction tetrasubstituted stereocenter.This approach features bond-forming/annulation efficiency,good functional group tolerance and complete regioselectivity,which may include a complex process consisting of Rh(Ⅲ)-catalyzed C(sp2)–H activation,cyclic alkene insertion,defluorinated ring-opening of gem-difluorocyclopropane,intramolecular oxygen transfer,intramolecular cyclization and oxidative hydration.展开更多
FeO-containing slag originated from the basic oxygen furnace to the ladle is a major reoxidation source during the following secondary refining.Ladle slag reduction treatment(slag treatment)is one of the common counte...FeO-containing slag originated from the basic oxygen furnace to the ladle is a major reoxidation source during the following secondary refining.Ladle slag reduction treatment(slag treatment)is one of the common countermeasures adopted to eliminate the steel contamination by FeO reoxidation.The oxygen transfer phenomenon between molten steel and slag was studied during the industrial production of interstitial-free(IF)steel,the measured and calculated oxygen activities in steel were compared,and the Fe–O equilibrium at the slag–molten steel interface was investigated by thermodynamic analysis.With slag treatment,the oxygen potential is higher in the molten steel than in the pre-deoxidation slag;this causes oxygen transfer from the molten steel to the slag,decreasing the efficiency of slag treatment.Based on this,a two-step slag deoxidation process was optimized.The second step further reduced the FeO content.On the other hand,the CaO/Al2O3(C/A)ratio in the refining slag must be controlled,because it affects the FeO activity and inclusion absorption capacity of the slag.The results suggest that the C/A ratio of 1.2–1.5 and the FeO content of\6%are beneficial to refine IF steel.展开更多
By measuring the mass transfer coefficient of benzoic acid between water and oil, the oxygen transfer rate in BOF bath was researched, and the influence of top and bottom blowing gas flow rate on the mass transfer bet...By measuring the mass transfer coefficient of benzoic acid between water and oil, the oxygen transfer rate in BOF bath was researched, and the influence of top and bottom blowing gas flow rate on the mass transfer between metal and slag was discussed. The results show that with increasing the bottom blowing gas flow rate under the conditions of fixed top blowing, the mass transfer rate evidently increases, and the influence of fixed top blowing on the mass transfer is 10% of bottom blowing. The stirring intensity was determined as a function of top blowing gas flow rate, bottom blowing gas flow rate, and lance height. The equation of the mass transfer coefficient between metal and slag was established. The relationship between the emulsification ratio of oil to water and the bottom blowing gas flow rate under the conditions of top and bottom blowing was obtained. The result shows that with the increase in the bottom blowing gas flow rate, the emulsification ratio increases linearly, which increases the mass transfer rate of benzoic acid between water and oil.展开更多
Knowledge of the oxygen mass transfer of aerators under operational conditions in a full-scale wastewater treatment plant （WWTP） is meaningful for the optimization of WWTP, however, scarce to best of our knowledge. ...Knowledge of the oxygen mass transfer of aerators under operational conditions in a full-scale wastewater treatment plant （WWTP） is meaningful for the optimization of WWTP, however, scarce to best of our knowledge. Through analyzing a plug flow aeration tank in the Lucun WWTP, in Wuxi, China, the oxygenation capacity of fine-bubble aerators under process conditions have been measured in- situ using the off-gas method and the non-steady-state method. The off-gas method demonstrated that the aerators in different corridors in the aeration tank of WWTP had significantly different oxygen transfer performance; furthermore, the aerators in the same corridor shared almost equal oxygen transfer performance over the course of a day. Results measured by the two methods showed that the oxygen transfer performance of fine-bubble aerators in the aeration tank decreased dramatically compared with that in the clean water. The loss of oxygen transfer coefficient was over 50% under low-aeration conditions （aeration amount 〈 0.67 Nm 3 /hr）. However, as the aeration amount reached 0.96 Nm 3 /hr, the discrepancy of oxygen transfer between the process condition and clean water was negligible. The analysis also indicated that the non-steady-state and off-gas methods resulted in comparable estimates of oxygen transfer parameters for the aerators under process conditions.展开更多
The interfacial oxygen transfer rate is one of the main factors to control the composition of alloys.The commonly employed method of studying the interfacial oxygen transfer rate is the chemical composition analysis;h...The interfacial oxygen transfer rate is one of the main factors to control the composition of alloys.The commonly employed method of studying the interfacial oxygen transfer rate is the chemical composition analysis;however,it is difficult to be studied in situ.Here,a new method of measuring the oxygen transfer rate at the gas-slag and slag-metal interfaces was reported based on electrochemical analyses.The interfacial oxygen transfer rate in the smelting process of Inconel 718 superalloy was investigated at 1723,1773,1823,and 1873 K.The experimental results show that the electrochemical method can measure the real-time oxygen content;hence,this method is promising in controlling the oxygen content in alloys.As the temperature increased,both the equilibrium oxygen content and the rate of oxygen absorption increased significantly,and the increase was the most obvious when the temperature was 1873 K.The possible reason is that the increase in temperature weakens the mass transfer resistance of the electric double layer at the interface,thus accelerating the oxygen transfer rate.展开更多
Oxygen transfer presents a serious challenge in the application of liquid lead as a nuclear coolant in advanced reactors. To mitigate corrosion by liquid lead in contact with steel, carefully controlling the oxygen co...Oxygen transfer presents a serious challenge in the application of liquid lead as a nuclear coolant in advanced reactors. To mitigate corrosion by liquid lead in contact with steel, carefully controlling the oxygen concentration has been used as an effective way. Oxygen needs to mix in liquid lead uniformly and quickly. To enhance oxygen transport in liquid lead, nanoparticles are added to the liquid metal. In the current study, a lattice Boltzmann method is applied to investigate natural convection of copper/lead and aluminum oxide/lead in two-dimensional simplified container. Two thermal boundary cases are evaluated in order to check the effect of different natural convection flow patterns on oxygen transport. Some useful information are obtained such as improvement in natural convection and reduction in oxygen equilibrium time.展开更多
In this paper, the characteristics of fluid mixing time in a novel extra-loop fluidized bed were studied. The results showed that the mixing time was shortened with the increase of fluid velocity. All the discrete num...In this paper, the characteristics of fluid mixing time in a novel extra-loop fluidized bed were studied. The results showed that the mixing time was shortened with the increase of fluid velocity. All the discrete numbers of the reactor were above 0.2. The serial number n was 2.5 -3.0. It was judged accordingly that the reactor fluid state was continous stirred tank reactor （CSTR） mainly. When the inspiratory capacity increased the mixing time of the reactor was shortened. Thus the air input was beneficial for the fluid mixing. During the three phases mixing process, the mixing time of the reactor could be decreased by the n increase of carrier and air loading together, but the change was not significant. The parameters affecting the reactor fluid state were fluid velocity, inspiratory capacity and carrier. KLa could be increased with the air loading increase, and at the same gas/liquid ratio when the pressure drop was high, KL~ value was increased. The amount of carrier complex influence on KLa. As the carrier loading continued to increase, its value had been dropped but the changes was not significant, and optimization condition was found at above 800 1 000 g carrier loading （pouzzolane） or 600 g PVC. Under gas/liquid ratio of 0.8% -5.2%, KLa was （0.62-1.37）×10^-2· s^-1.展开更多
A flexible fibre biofilm reactor was developed for treatment of organic wastewaters.The hydrodynamic characteristics and mass transfer coefficients of oxygen were studied and compared with those of the conventional ac...A flexible fibre biofilm reactor was developed for treatment of organic wastewaters.The hydrodynamic characteristics and mass transfer coefficients of oxygen were studied and compared with those of the conventional activated sludge processes.Tracer experiments were performed to obtain the residence time distributions of the reactors.The results indicated that both reactors could be treated as mixed flow reactors.The effects of flow rates of water and air on the overall mass transfer coefficient of oxygen were investigated,and the correlations between the mass transfer coefficient and the ratio of flow rates were obtained.Compared to the conventional activated sludge reactor,the mass transfer coefficients in the flexible fibre reactor were similar to but slightly lower,and less sensitive to the variation in the ratio of flow rates.It indicated that the fibre packing in the reactor hindered the oxygen transfer to some extent.展开更多
Ammonia is an important chemical for pharmaceutical,agriculture,industry,as well as energy production et al.However,the industrial production of ammonia using the Haber-Bosch process is energy-intensive,which stimulat...Ammonia is an important chemical for pharmaceutical,agriculture,industry,as well as energy production et al.However,the industrial production of ammonia using the Haber-Bosch process is energy-intensive,which stimulates us to explore a cost-effective and low-carbon footprint way for the synthesis of ammonia[1–3].Electrochemical(EC)synthesis of ammonia from an aqueous N_(2)reduction reaction(NRR)has gained significant attention in recent years,while the high dissociation energy of the N≡N bond(941 kJ/mol),as well as higher over-potential than hydrogen evolution reaction(HER),cause a lower efficiency[4].展开更多
The movement of the bubble plume plays an important role in the operation of a moving bed biofilm reactor （MBBR）, and it directly affects the contact and the mixture of the gas-liquid-solid phases in the aeration ta...The movement of the bubble plume plays an important role in the operation of a moving bed biofilm reactor （MBBR）, and it directly affects the contact and the mixture of the gas-liquid-solid phases in the aeration tank and also the oxygen transfer from the gas phase to the liquid phase. In this study, the velocity field is determined by a 4-frame PTV as well as the time-averaged and timedependent velocity distributions. The velocity distribution of the bubble plume is analyzed to evaluate the operating efficiency of the MBBR. The results show that the aeration rate is one of the main factors that sway the velocity distribution of the bubble plumes and affect the operating efficiency of the reactor.展开更多
The dissolved oxygen concentration is an important index of water quality, and the atmosphere is one of the important sources of the dissolved oxygen. In this paper, the mass conservation law and the dimensional analy...The dissolved oxygen concentration is an important index of water quality, and the atmosphere is one of the important sources of the dissolved oxygen. In this paper, the mass conservation law and the dimensional analysis method are employed to study the oxygen transfer under regular and non-breaking waves, and a unified oxygen transfer coefficient equation is obtained with consideration of the effect of kinetic energy and wave period. An oxygen transfer experiment for the intermediate depth water wave is performed to measure the wave parameters and the dissolved oxygen concentration. The experimental data and the least squares method are used to determine the constant in the oxygen transfer coefficient equation. The experimental data and the previous reported data are also used to further validate the oxygen transfer coefficient, and the agreement is satisfactory. The unified equation shows that the oxygen transfer coefficient increases with the increase of a parameter coupled with the wave height and the wave length, but it decreases with the increase of the wave period, which has a much greater influence on the oxygen transfer coefficient than the coupled parameter.展开更多
The dissolved oxygen level is an important index of the water environment,and in this paper,the oxygen transfer of the bubbly jet in regular waves is investigated numerically and experimentally.The Reynolds-averaged N...The dissolved oxygen level is an important index of the water environment,and in this paper,the oxygen transfer of the bubbly jet in regular waves is investigated numerically and experimentally.The Reynolds-averaged Navier-Stokes equations,the re-normalisation group k-e equations,and the volume of fluid(VOF)technique are used along with a 2-D CFD model to simulate the wave and bubble motions as well as the turbulence,and a dissolved oxygen transport equation is used to model the oxygen transfer behavior both through the bubbly interface and the wave surface.A series of experiments are conducted to validate the mathematical model,with good agreement.In addition,a group of dimensionless parameters are defined from the wave parameter and the aeration parameter,and their relationships with the total oxygen transfer coefficient are explored.Furthermore,the dimensional analysis and the least squares methods are used to derive simple prediction formulas for the total oxygen transfer coefficient,and they are validated with the related experimental data.展开更多
Three laboratory-scale moving bed biofilm reactors （MBBR） with different carrier filling ratios ranging from 40% to 60% were used to study the effects of carrier-attached biofilm on oxygen transfer efficiency. In th...Three laboratory-scale moving bed biofilm reactors （MBBR） with different carrier filling ratios ranging from 40% to 60% were used to study the effects of carrier-attached biofilm on oxygen transfer efficiency. In this study, we evaluated the performance of three MBBRs in degrading chemical oxygen demand and ammonia. The three reactors removed more than 95% of NH4^＋ -N at an air flow-rate of 60L·h^-1. The standard oxygen transfer efficiency （αSOTE） of the three reactors was also investigated at air flow-rates ranging from 60 to 100L·h^-1. These results were compared to αSOTE of wastewater with a clean carrier （no biofilm attached）. Results showed that under. these process conditions, αSOTE decreased by approximately 70% as compared to αSOTE of wastewater at a different carrier-filling ratio. This indicated that the biofilm attached to the cartier had a negative effect on αSOTE. Mechanism analysis showed that the main inhibiting effects were related to biofilm flocculants and soluble microbial product （SMP）. Biofilm flocs could decrease otSOTE by about 20%, and SMP could decrease aαSOTE by 30%--50%.展开更多
In wastewater treatment plants（WWTPs）using the activated sludge process,two methods are widely used to improve aeration efficiency — use of high-efficiency aeration devices and optimizing the aeration control strat...In wastewater treatment plants（WWTPs）using the activated sludge process,two methods are widely used to improve aeration efficiency — use of high-efficiency aeration devices and optimizing the aeration control strategy. Aeration efficiency is closely linked to sludge characteristics（such as concentrations of mixed liquor suspended solids（MLSS）and microbial communities）and operating conditions（such as air flow rate and operational dissolved oxygen（DO）concentrations）. Moreover,operational DO is closely linked to effluent quality. This study,which is in reference to WWTP discharge class A Chinese standard effluent criteria,determined the growth kinetics parameters of nitrifiers at different DO levels in small-scale tests. Results showed that the activated sludge system could meet effluent criteria when DO was as low as 0.3 mg/L,and that nitrifier communities cultivated under low DO conditions had higher oxygen affinity than those cultivated under high DO conditions,as indicated by the oxygen half-saturation constant and nitrification ability. Based on nitrifier growth kinetics and on the oxygen mass transfer dynamic model（determined using different air flow rate（Q′air）and mixed liquor volatile suspended solids（MLVSS）values）,theoretical analysis indicated limited potential for energy saving by improving aeration diffuser performance when the activated sludge system had low oxygen consumption; however,operating at low DO and low MLVSS could significantly reduce energy consumption. Finally,a control strategy coupling sludge retention time and MLVSS to minimize the DO level was discussed,which is critical to appropriate setting of the oxygen point and to the operation of low DO treatment technology.展开更多
The effects of oxidizing slag on oxygen mass transfer and inclusions in different stages of IF(interstitial-free)steel refining were investigated by several heat simulation experiments.The results of the experiments s...The effects of oxidizing slag on oxygen mass transfer and inclusions in different stages of IF(interstitial-free)steel refining were investigated by several heat simulation experiments.The results of the experiments showed that the oxidizability of slag changed considerably during different refining stages.Keeping the content of FeO in the slag within 1 wt.%would narrow the difference of slag oxidizability,stabilize the content of[Al]s in the steel,avoid secondary oxidation of molten steel by the slag,and reduce the inclusions.When the mass transfer of FeO in the slag phase was a limiting step,the secondary oxidation reaction occurred at the steel–slag interface;when the diffusion of oxygen in the molten steel was a limiting step,the secondary oxidation reaction took place inside the molten steel.The oxygen transfer rate was affected by the mass transfer coefficient of oxygen.For every 0.0001m/s increase in mass transfer coefficient,the oxygen transfer rate increased by about 2.2×10^-6 min^-1.By changing the mass transfer coefficient,the oxygen transfer rate of the slag to the molten steel can be controlled.展开更多
Due to 4f electron characteristics and alternation valence, cerium involved in an oxidation-reduction reaction in plant, closely relating to photosynthesis. Our studies proved that cerium could promote photosynthesis ...Due to 4f electron characteristics and alternation valence, cerium involved in an oxidation-reduction reaction in plant, closely relating to photosynthesis. Our studies proved that cerium could promote photosynthesis and greatly improve spinach growth. However, the mechanism of promoting energy transfer and conversion by cerium remains unclear. Here we reported that the effects of Ce^3＋ on energy transfer and oxygen evolution in photosystem Ⅱ （PS Ⅱ ） isolated from spinach, which was related to 4f electron characteristics and alternation valence in Ce molecule. The methods of absorption spectrum, fluorescence spectrum were used in the research. Results showed that Ce^3＋ treatment at low concentration could suitably change PS Ⅱ mieroenvironment, increase the absorbance of visible light, improve the energy transfer among amino acids within PS Ⅱ protein-pigment complex, and accelerate energy transport from tyrosine residue to chlorophyll a. In summary, the photochemical activity of PS Ⅱ （fluorescence quantum yield） and its oxygen evolving rate were enhanced by Ce^3＋.展开更多
Pseudo-first order reaction rate constants of 5,10,15-tris（pentafluorophenyl）corrole Mn（V）-oxo （F_（15）CMn（V）-oxo）,5,15-bis（pentafluorophenyl）-10-（phenyl）corrole Mn（V）-oxo（F_（10）CMn（V）-oxo）,5,15- ...Pseudo-first order reaction rate constants of 5,10,15-tris（pentafluorophenyl）corrole Mn（V）-oxo （F_（15）CMn（V）-oxo）,5,15-bis（pentafluorophenyl）-10-（phenyl）corrole Mn（V）-oxo（F_（10）CMn（V）-oxo）,5,15- bis（phenyl）-10-（pentafluorophenyl）corrole Mn（V）-oxo（F_5CMn（V）-oxo） and 5,10,15-tris（phenyl）corrole Mn（V）-oxo（F_0CMn（V）-oxo） with a series of alkene substrates in different solvents were determined by UV-vis spectroscopy.The results indicated that the oxygen atom transfer pathway between Mn（V）-oxo corrole and alkene is solvent-dependent.展开更多
基金financial support from the schoollevel research projects of Yancheng Institute of Technology(No.xjr2020044)the National Natural Science Foundation of China(Nos.22101152,22271123 and 21971090)。
文摘Catalytic C–H activation-initiated annulation reactions have emerged as a versatile strategy for the efficient construction of diverse ring structural units and complex cyclic molecules in synthetic chemistry.Herein,we describe a new Rh(Ⅲ)-catalyzed C–H activation-initiated transdiannulation reaction of N,Ndimethyl enaminones with gem-difluorocyclopropenes in the presence of H_(2)O,enabling a facile and oxygen transfer access to ring-fluorinated tricyclicγ-lactones with a 6-5 ring-junction tetrasubstituted stereocenter.This approach features bond-forming/annulation efficiency,good functional group tolerance and complete regioselectivity,which may include a complex process consisting of Rh(Ⅲ)-catalyzed C(sp2)–H activation,cyclic alkene insertion,defluorinated ring-opening of gem-difluorocyclopropane,intramolecular oxygen transfer,intramolecular cyclization and oxidative hydration.
基金The authors are grateful for financial support from the National Natural Science Foundation of China under Grant No.51404020the National Key R&D Program of China under Grant Nos.2017YFB0304000 and 2017YFB0304001.
文摘FeO-containing slag originated from the basic oxygen furnace to the ladle is a major reoxidation source during the following secondary refining.Ladle slag reduction treatment(slag treatment)is one of the common countermeasures adopted to eliminate the steel contamination by FeO reoxidation.The oxygen transfer phenomenon between molten steel and slag was studied during the industrial production of interstitial-free(IF)steel,the measured and calculated oxygen activities in steel were compared,and the Fe–O equilibrium at the slag–molten steel interface was investigated by thermodynamic analysis.With slag treatment,the oxygen potential is higher in the molten steel than in the pre-deoxidation slag;this causes oxygen transfer from the molten steel to the slag,decreasing the efficiency of slag treatment.Based on this,a two-step slag deoxidation process was optimized.The second step further reduced the FeO content.On the other hand,the CaO/Al2O3(C/A)ratio in the refining slag must be controlled,because it affects the FeO activity and inclusion absorption capacity of the slag.The results suggest that the C/A ratio of 1.2–1.5 and the FeO content of\6%are beneficial to refine IF steel.
基金Item Sponsored by National Science and Technology Support Program for 11th Five-Year Plan of China (2006BAE03A00)
文摘By measuring the mass transfer coefficient of benzoic acid between water and oil, the oxygen transfer rate in BOF bath was researched, and the influence of top and bottom blowing gas flow rate on the mass transfer between metal and slag was discussed. The results show that with increasing the bottom blowing gas flow rate under the conditions of fixed top blowing, the mass transfer rate evidently increases, and the influence of fixed top blowing on the mass transfer is 10% of bottom blowing. The stirring intensity was determined as a function of top blowing gas flow rate, bottom blowing gas flow rate, and lance height. The equation of the mass transfer coefficient between metal and slag was established. The relationship between the emulsification ratio of oil to water and the bottom blowing gas flow rate under the conditions of top and bottom blowing was obtained. The result shows that with the increase in the bottom blowing gas flow rate, the emulsification ratio increases linearly, which increases the mass transfer rate of benzoic acid between water and oil.
基金supported by the Major Water Project of the National Science and Technology (No.2011ZX07319-001-004, 2011ZX07301-002)
文摘Knowledge of the oxygen mass transfer of aerators under operational conditions in a full-scale wastewater treatment plant （WWTP） is meaningful for the optimization of WWTP, however, scarce to best of our knowledge. Through analyzing a plug flow aeration tank in the Lucun WWTP, in Wuxi, China, the oxygenation capacity of fine-bubble aerators under process conditions have been measured in- situ using the off-gas method and the non-steady-state method. The off-gas method demonstrated that the aerators in different corridors in the aeration tank of WWTP had significantly different oxygen transfer performance; furthermore, the aerators in the same corridor shared almost equal oxygen transfer performance over the course of a day. Results measured by the two methods showed that the oxygen transfer performance of fine-bubble aerators in the aeration tank decreased dramatically compared with that in the clean water. The loss of oxygen transfer coefficient was over 50% under low-aeration conditions （aeration amount 〈 0.67 Nm 3 /hr）. However, as the aeration amount reached 0.96 Nm 3 /hr, the discrepancy of oxygen transfer between the process condition and clean water was negligible. The analysis also indicated that the non-steady-state and off-gas methods resulted in comparable estimates of oxygen transfer parameters for the aerators under process conditions.
基金gratefully express their appreciation to National Natural Science Foundation of China(Nos.51974153 and U1960203)the Joint Fund of State Key Laboratory of Marine Engineering and University of Science and Technology Liaoning(SKLMEA-USTL-201707)the China Scholarship Council(201908210457).
文摘The interfacial oxygen transfer rate is one of the main factors to control the composition of alloys.The commonly employed method of studying the interfacial oxygen transfer rate is the chemical composition analysis;however,it is difficult to be studied in situ.Here,a new method of measuring the oxygen transfer rate at the gas-slag and slag-metal interfaces was reported based on electrochemical analyses.The interfacial oxygen transfer rate in the smelting process of Inconel 718 superalloy was investigated at 1723,1773,1823,and 1873 K.The experimental results show that the electrochemical method can measure the real-time oxygen content;hence,this method is promising in controlling the oxygen content in alloys.As the temperature increased,both the equilibrium oxygen content and the rate of oxygen absorption increased significantly,and the increase was the most obvious when the temperature was 1873 K.The possible reason is that the increase in temperature weakens the mass transfer resistance of the electric double layer at the interface,thus accelerating the oxygen transfer rate.
基金the financial support from the office of Vice-President for Research at University of Nevada-Las Vegas
文摘Oxygen transfer presents a serious challenge in the application of liquid lead as a nuclear coolant in advanced reactors. To mitigate corrosion by liquid lead in contact with steel, carefully controlling the oxygen concentration has been used as an effective way. Oxygen needs to mix in liquid lead uniformly and quickly. To enhance oxygen transport in liquid lead, nanoparticles are added to the liquid metal. In the current study, a lattice Boltzmann method is applied to investigate natural convection of copper/lead and aluminum oxide/lead in two-dimensional simplified container. Two thermal boundary cases are evaluated in order to check the effect of different natural convection flow patterns on oxygen transport. Some useful information are obtained such as improvement in natural convection and reduction in oxygen equilibrium time.
基金Project supported by the Foundation Social European,Republoque Francaise
文摘In this paper, the characteristics of fluid mixing time in a novel extra-loop fluidized bed were studied. The results showed that the mixing time was shortened with the increase of fluid velocity. All the discrete numbers of the reactor were above 0.2. The serial number n was 2.5 -3.0. It was judged accordingly that the reactor fluid state was continous stirred tank reactor （CSTR） mainly. When the inspiratory capacity increased the mixing time of the reactor was shortened. Thus the air input was beneficial for the fluid mixing. During the three phases mixing process, the mixing time of the reactor could be decreased by the n increase of carrier and air loading together, but the change was not significant. The parameters affecting the reactor fluid state were fluid velocity, inspiratory capacity and carrier. KLa could be increased with the air loading increase, and at the same gas/liquid ratio when the pressure drop was high, KL~ value was increased. The amount of carrier complex influence on KLa. As the carrier loading continued to increase, its value had been dropped but the changes was not significant, and optimization condition was found at above 800 1 000 g carrier loading （pouzzolane） or 600 g PVC. Under gas/liquid ratio of 0.8% -5.2%, KLa was （0.62-1.37）×10^-2· s^-1.
文摘A flexible fibre biofilm reactor was developed for treatment of organic wastewaters.The hydrodynamic characteristics and mass transfer coefficients of oxygen were studied and compared with those of the conventional activated sludge processes.Tracer experiments were performed to obtain the residence time distributions of the reactors.The results indicated that both reactors could be treated as mixed flow reactors.The effects of flow rates of water and air on the overall mass transfer coefficient of oxygen were investigated,and the correlations between the mass transfer coefficient and the ratio of flow rates were obtained.Compared to the conventional activated sludge reactor,the mass transfer coefficients in the flexible fibre reactor were similar to but slightly lower,and less sensitive to the variation in the ratio of flow rates.It indicated that the fibre packing in the reactor hindered the oxygen transfer to some extent.
基金supported by the National Natural Science Foundation of China(T2322013)supported by the Ministry of Science and ICT through the National Research Foundation of Korea(2022H1D3A3A01077254,NRF-2019R1A2C3010479)。
文摘Ammonia is an important chemical for pharmaceutical,agriculture,industry,as well as energy production et al.However,the industrial production of ammonia using the Haber-Bosch process is energy-intensive,which stimulates us to explore a cost-effective and low-carbon footprint way for the synthesis of ammonia[1–3].Electrochemical(EC)synthesis of ammonia from an aqueous N_(2)reduction reaction(NRR)has gained significant attention in recent years,while the high dissociation energy of the N≡N bond(941 kJ/mol),as well as higher over-potential than hydrogen evolution reaction(HER),cause a lower efficiency[4].
基金supported by the National Natural Science Foun-dation of China(Grant No.51076130)
文摘The movement of the bubble plume plays an important role in the operation of a moving bed biofilm reactor （MBBR）, and it directly affects the contact and the mixture of the gas-liquid-solid phases in the aeration tank and also the oxygen transfer from the gas phase to the liquid phase. In this study, the velocity field is determined by a 4-frame PTV as well as the time-averaged and timedependent velocity distributions. The velocity distribution of the bubble plume is analyzed to evaluate the operating efficiency of the MBBR. The results show that the aeration rate is one of the main factors that sway the velocity distribution of the bubble plumes and affect the operating efficiency of the reactor.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51009123,50809065)the Natural Science Foundation of Shandong Province(Grant No.ZR2009FQ003)
文摘The dissolved oxygen concentration is an important index of water quality, and the atmosphere is one of the important sources of the dissolved oxygen. In this paper, the mass conservation law and the dimensional analysis method are employed to study the oxygen transfer under regular and non-breaking waves, and a unified oxygen transfer coefficient equation is obtained with consideration of the effect of kinetic energy and wave period. An oxygen transfer experiment for the intermediate depth water wave is performed to measure the wave parameters and the dissolved oxygen concentration. The experimental data and the least squares method are used to determine the constant in the oxygen transfer coefficient equation. The experimental data and the previous reported data are also used to further validate the oxygen transfer coefficient, and the agreement is satisfactory. The unified equation shows that the oxygen transfer coefficient increases with the increase of a parameter coupled with the wave height and the wave length, but it decreases with the increase of the wave period, which has a much greater influence on the oxygen transfer coefficient than the coupled parameter.
基金supported by the National Natural Science Foundation of China(Grant Nos.51879251,51579229)the Key Research and Development Plan of Shandong Province,China(Grant No.2017GHY15103)the State Key Laboratory of Ocean Engineering,Shanghai Jiao Tong University,China(Grant No.1602).
文摘The dissolved oxygen level is an important index of the water environment,and in this paper,the oxygen transfer of the bubbly jet in regular waves is investigated numerically and experimentally.The Reynolds-averaged Navier-Stokes equations,the re-normalisation group k-e equations,and the volume of fluid(VOF)technique are used along with a 2-D CFD model to simulate the wave and bubble motions as well as the turbulence,and a dissolved oxygen transport equation is used to model the oxygen transfer behavior both through the bubbly interface and the wave surface.A series of experiments are conducted to validate the mathematical model,with good agreement.In addition,a group of dimensionless parameters are defined from the wave parameter and the aeration parameter,and their relationships with the total oxygen transfer coefficient are explored.Furthermore,the dimensional analysis and the least squares methods are used to derive simple prediction formulas for the total oxygen transfer coefficient,and they are validated with the related experimental data.
基金This study was supported by the National Natural Science Foundation of China （Grant No. 51408601）.
文摘Three laboratory-scale moving bed biofilm reactors （MBBR） with different carrier filling ratios ranging from 40% to 60% were used to study the effects of carrier-attached biofilm on oxygen transfer efficiency. In this study, we evaluated the performance of three MBBRs in degrading chemical oxygen demand and ammonia. The three reactors removed more than 95% of NH4^＋ -N at an air flow-rate of 60L·h^-1. The standard oxygen transfer efficiency （αSOTE） of the three reactors was also investigated at air flow-rates ranging from 60 to 100L·h^-1. These results were compared to αSOTE of wastewater with a clean carrier （no biofilm attached）. Results showed that under. these process conditions, αSOTE decreased by approximately 70% as compared to αSOTE of wastewater at a different carrier-filling ratio. This indicated that the biofilm attached to the cartier had a negative effect on αSOTE. Mechanism analysis showed that the main inhibiting effects were related to biofilm flocculants and soluble microbial product （SMP）. Biofilm flocs could decrease otSOTE by about 20%, and SMP could decrease aαSOTE by 30%--50%.
基金supported by the National Science and Technology Major Project(No.2013ZX07314-001)
文摘In wastewater treatment plants（WWTPs）using the activated sludge process,two methods are widely used to improve aeration efficiency — use of high-efficiency aeration devices and optimizing the aeration control strategy. Aeration efficiency is closely linked to sludge characteristics（such as concentrations of mixed liquor suspended solids（MLSS）and microbial communities）and operating conditions（such as air flow rate and operational dissolved oxygen（DO）concentrations）. Moreover,operational DO is closely linked to effluent quality. This study,which is in reference to WWTP discharge class A Chinese standard effluent criteria,determined the growth kinetics parameters of nitrifiers at different DO levels in small-scale tests. Results showed that the activated sludge system could meet effluent criteria when DO was as low as 0.3 mg/L,and that nitrifier communities cultivated under low DO conditions had higher oxygen affinity than those cultivated under high DO conditions,as indicated by the oxygen half-saturation constant and nitrification ability. Based on nitrifier growth kinetics and on the oxygen mass transfer dynamic model（determined using different air flow rate（Q′air）and mixed liquor volatile suspended solids（MLVSS）values）,theoretical analysis indicated limited potential for energy saving by improving aeration diffuser performance when the activated sludge system had low oxygen consumption; however,operating at low DO and low MLVSS could significantly reduce energy consumption. Finally,a control strategy coupling sludge retention time and MLVSS to minimize the DO level was discussed,which is critical to appropriate setting of the oxygen point and to the operation of low DO treatment technology.
基金The authors would like to express their appreciation to the National Natural Science Foundation of China(No.51471002).
文摘The effects of oxidizing slag on oxygen mass transfer and inclusions in different stages of IF(interstitial-free)steel refining were investigated by several heat simulation experiments.The results of the experiments showed that the oxidizability of slag changed considerably during different refining stages.Keeping the content of FeO in the slag within 1 wt.%would narrow the difference of slag oxidizability,stabilize the content of[Al]s in the steel,avoid secondary oxidation of molten steel by the slag,and reduce the inclusions.When the mass transfer of FeO in the slag phase was a limiting step,the secondary oxidation reaction occurred at the steel–slag interface;when the diffusion of oxygen in the molten steel was a limiting step,the secondary oxidation reaction took place inside the molten steel.The oxygen transfer rate was affected by the mass transfer coefficient of oxygen.For every 0.0001m/s increase in mass transfer coefficient,the oxygen transfer rate increased by about 2.2×10^-6 min^-1.By changing the mass transfer coefficient,the oxygen transfer rate of the slag to the molten steel can be controlled.
基金Project supported by the National Natural Science Foundation of China (20671067, 30470150)
文摘Due to 4f electron characteristics and alternation valence, cerium involved in an oxidation-reduction reaction in plant, closely relating to photosynthesis. Our studies proved that cerium could promote photosynthesis and greatly improve spinach growth. However, the mechanism of promoting energy transfer and conversion by cerium remains unclear. Here we reported that the effects of Ce^3＋ on energy transfer and oxygen evolution in photosystem Ⅱ （PS Ⅱ ） isolated from spinach, which was related to 4f electron characteristics and alternation valence in Ce molecule. The methods of absorption spectrum, fluorescence spectrum were used in the research. Results showed that Ce^3＋ treatment at low concentration could suitably change PS Ⅱ mieroenvironment, increase the absorbance of visible light, improve the energy transfer among amino acids within PS Ⅱ protein-pigment complex, and accelerate energy transport from tyrosine residue to chlorophyll a. In summary, the photochemical activity of PS Ⅱ （fluorescence quantum yield） and its oxygen evolving rate were enhanced by Ce^3＋.
基金The financial support from the National Natural Science Foundation of China(Nos.20971046 and 21171057)
文摘Pseudo-first order reaction rate constants of 5,10,15-tris（pentafluorophenyl）corrole Mn（V）-oxo （F_（15）CMn（V）-oxo）,5,15-bis（pentafluorophenyl）-10-（phenyl）corrole Mn（V）-oxo（F_（10）CMn（V）-oxo）,5,15- bis（phenyl）-10-（pentafluorophenyl）corrole Mn（V）-oxo（F_5CMn（V）-oxo） and 5,10,15-tris（phenyl）corrole Mn（V）-oxo（F_0CMn（V）-oxo） with a series of alkene substrates in different solvents were determined by UV-vis spectroscopy.The results indicated that the oxygen atom transfer pathway between Mn（V）-oxo corrole and alkene is solvent-dependent.
