The cheap manganese sand was first modified by H2O2 and was further creatively utilized as Ni-based catalyst support.In order to enhance the catalytic performance,Re was added into the Ni-based catalyst and the promot...The cheap manganese sand was first modified by H2O2 and was further creatively utilized as Ni-based catalyst support.In order to enhance the catalytic performance,Re was added into the Ni-based catalyst and the promotion effect of Re on the methanation coupling with water gas shift of biogas was investigated from the perspective of activation energy.It was found that CH4 and CO2 formation rates,which separately represented the reaction rate of methanation and water gas shift,were both enhanced after Re addition compared to non-added catalyst.Two kinetics models including empirical model and K-model were employed and from the results of calculation,it showed that Re selectively decreased the activation energy of methanation reaction and had little impact on the activation energy of water gas shift.The increased CO2 formation rate was owing to the assistance of accelerated H2O production from methanation rather than the activation energy change in water gas shift.展开更多
Methanation is an effective way to efficiently utilize product gas generated from the pyrolysis and gasification of organic solid wastes.To deeply study the heat transfer and mass transfer mechanisms in the reactor,a ...Methanation is an effective way to efficiently utilize product gas generated from the pyrolysis and gasification of organic solid wastes.To deeply study the heat transfer and mass transfer mechanisms in the reactor,a successful three-dimensional comprehensive model has been established.Multiphase flow behavior and heat transfer mechanisms were investigated under reference working conditions.Temperature is determined by the heat release of the reaction and the heat transfer of the gas-solid flow.The maximum temperature can reach 951 K where the catalyst gathers.In the simulation,changes in the gas inlet velocity and catalyst flow rate were made to explore their effects on CO conversion rate and temperature for optimization purposes.As the inlet gas velocity increases from 2.78 to 4.79 m/s,the CO conversion rate decreases from 81.6%to 72.4%.However,more heat is removed from the reactor,and the temperature rise increases from 78.03 to 113.49 K.When the catalyst flow rate is increased from 7.18 to 17.96 kg/(m^(2)·s),the mass of the catalyst in the reactor is increased from 0.0019 to 0.0042 kg,and the CO conversion rate is increased from 66.8%to 81.5%.However,this increases the maximum temperature in the reactor from 940.0 to 966.4 K.展开更多
Organic solid waste(OSW)contains many renewable materials.The pyrolysis and gasification of OSW can realize resource utilization,and its products can be used for methanation reaction to produce synthetic natural gas i...Organic solid waste(OSW)contains many renewable materials.The pyrolysis and gasification of OSW can realize resource utilization,and its products can be used for methanation reaction to produce synthetic natural gas in the specific reactor.In order to understand the dynamic characteristics of the reactor,a three-dimensional numerical model has been established by the method of Computational Fluid Dynamics(CFD).Along the height of the reactor,the particle distribution in the bed becomes thinner and the mean solid volume fraction decreases from 4.18%to 0.37%.Meanwhile,the pressure fluctuation range decreased from 398.76 Pa at the entrance to a much lower value of 74.47 Pa at the exit.In this simulation,three parameters of gas inlet velocity,operating temperature and solid particle diameter are changed to explore their influences on gas-solid multiphase flow.The results show that gas velocity has a great influence on particle distribution.When the gas inlet velocity decreases from 6.51 to 1.98 m/s,the minimum height that particles can reach decreases from 169 to 100 mm.Additionally,as the operating temperature increases,the particle holdup inside the reactor changes from 0.843%to 0.700%.This indicates that the particle residence time reduces,which is not conducive to the follow-up reaction.Moreover,with the increase of particle size,the fluctuation range of the pressure at the bottom of the reactor increases,and its standard deviation increases from 55.34 to 1266.37 Pa.展开更多
In this paper, high material quality Al_(0.4) In_(0.6) AsSb quaternary alloy on GaSb substrates is demonstrated. The quality of these epilayers is assessed using a high-resolution x-ray diffraction, Fourier transform ...In this paper, high material quality Al_(0.4) In_(0.6) AsSb quaternary alloy on GaSb substrates is demonstrated. The quality of these epilayers is assessed using a high-resolution x-ray diffraction, Fourier transform infrared(FTIR) spectrometer,and atomic force microscope(AFM). The x-ray diffraction exhibits high order satellite peaks with a measured period of 31.06 ?(theoretical value is 30.48 ?), the mismatch between the GaSb substrate and AlInAsSb achieves-162 arcsec,and the root-mean square(RMS) roughness for typical material growths has achieved around 1.6 ? over an area of 10 μm×10 μm. At room temperature, the photoluminescence(PL) spectrum shows a cutoff wavelength of 1.617 μm.展开更多
Pressurised oxy-fuel combustion(POFC)is a clean and efficient combustion technology with great potential.Due to the recycling of flue gas,the concentration of steam in the flue gas is higher than that of conventional ...Pressurised oxy-fuel combustion(POFC)is a clean and efficient combustion technology with great potential.Due to the recycling of flue gas,the concentration of steam in the flue gas is higher than that of conventional combustion,which enriches the free radical pool in the flue gas and thus affects the emission of gaseous pollutants.Therefore,further research into the effect of high steam concentrations on NO_(x)emission mechanisms in POFC is necessary.In this work,a fixed-bed reactor was used to conduct combustion experiments of volatiles and combined with chemical kinetic models to study the NO release characteristics for different pressures and steam concentrations in an O_(2)/CO_(2)atmosphere at 800℃/900℃temperature.The results of the study indicated that the volatile nitrogen comes from the pyrolysis of part of pyrrole,pyridine,and all quaternary nitrogen in coal.The increase in temperature promoted the formation of NO during combustion.Higher pressure affects the main reaction pathway for NO formation,promoting NO consumption by HCCO and C_(2)O groups while enhancing the overall NO reduction.Steam promoted NO consumption by NCO.In addition,steam increased the amount of H/OH groups during the reaction,which affected both NO formation and consumption.However,from the overall effect,the steam still inhibits the emission of NO.展开更多
Barocaloric refrigeration is regarded as one of the next-generation alternative refrigeration technology due to its environmental friendliness.In recent years,many researchers have been devoted to finding materials wi...Barocaloric refrigeration is regarded as one of the next-generation alternative refrigeration technology due to its environmental friendliness.In recent years,many researchers have been devoted to finding materials with colossal barocaloric effects,while neglecting the research on barocaloric refrigeration devices and thermodynamic cycles.Neopentyl glycol is regarded as one of the potential refrigerants for barocaloric refrigeration due to its giant isothermal entropy changes and relatively low operating pressure.To evaluate the performance of the barocaloric system using Neopentyl glycol,for the first time,this study establishes a thermodynamic cycle based on the metastable temperature-entropy diagram.The performance of the proposed system is investigated from the aspects of irreversibility,operating temperature range,and operating pressure,and optimized with finite-rate heat transfer.The guidance for the optimal design of the system is given by revealing the effect of the irreversibility in two isobaric processes.The results show that a COP of 8.8 can be achieved at a temperature span of 10 K when the system fully uses the phase transition region of Neopentyl glycol,while a COP of 3 can be achieved at a temperature span of 10 K when the system operates at room temperature.Furthermore,this study also shows that the system performance can be further improved through the modification of Neopentyl glycol,and some future development guidance is provided.展开更多
Cycle Time Distribution(CTD)plays a critical role for determining uniformity of particle coating in spray fluidized beds.However,the CTD is influenced by both geometrical structure and operating conditions of fluidize...Cycle Time Distribution(CTD)plays a critical role for determining uniformity of particle coating in spray fluidized beds.However,the CTD is influenced by both geometrical structure and operating conditions of fluidized bed.In this study,a spray fluidized bed of coating process is simulated by a comprehensive Computational Fluid Dynamics-Discrete Element Model(CFD-DEM).To achieve different behaviors of CTD,some modifications are designed on a pseudo-2D internally circulating fluidized bed,which traditionally composes of a high-velocity upward bed and low-velocity downward bed.These modifi-cations include making the air distributor slope and/or laying a baffle in the downward bed.First,the CTD and evolution of particle size distribution under different bed structures are compared.The CTD directly influences the coating uniformity.By making the particles flowing along a parallel direction in the downward bed through the geometrical modifications,the CTD becomes narrower and the coating uniformity is significantly improved.Second,under the optimized bed structure,the influence of oper-ating conditions on the coating uniformity is studied.Properly increasing the fluidization gas velocity and the fluidization gas temperature and reducing the liquid spray rate can improve the coating uniformity.展开更多
The aim of this study is to propose a photovoltaic(PV)module simulation model with high accuracy under practical working conditions and strong applicability in the engineering field to meet various PV system simulatio...The aim of this study is to propose a photovoltaic(PV)module simulation model with high accuracy under practical working conditions and strong applicability in the engineering field to meet various PV system simulation needs.Unlike previous model-building methods,this study combines the advantages of analytical and metaheuristic algorithms.First,the applicability of various metaheuristic algorithms is comprehensively compared and the seven parameters of the PV cell under standard test conditions are extracted using the double diode model,which verifies that the artificial hummingbird algorithm has higher accuracy than other algorithms.Then,the seven parameters under different conditions are corrected using the analytical method.In terms of the correc-tion method,the ideal factor correction is added on the basis of previous methods to solve the deviation between simulated data and measured data in the non-linear section.Finally,the root mean squared error between the simulated current data and the measured current data of the proposed model under three different temperatures and irradiance is 0.0697,0.0570 and 0.0289 A,respectively.展开更多
This paper proposes a comprehensive summary and analysis of an important issue during municipal solid waste(MSW)gasification-sulfur and nitrogen pollution.It provides an overview of the fundamentals of MSW and the bas...This paper proposes a comprehensive summary and analysis of an important issue during municipal solid waste(MSW)gasification-sulfur and nitrogen pollution.It provides an overview of the fundamentals of MSW and the basic aspects of nitrogen and sulfur elements.Their characteristics of immigration,transformation and distribution during gasification with control solutions in realized or potential engineering are also concluded.The analysis indicates that the complete scenario of the occurrence form of sulfur and nitrogen elements in MSW is difficult to obtain,owing to the diverse sources and complicated compositions.However,with the assistance of advanced characterization and quantification methods(XPS,XRD,TG-FTIR,et al.),the common sulfur-and nitrogen-containing compounds in both organic and inorganic states can be detected.Adjustment of gasification conditions can regulate the transformation of these elements for emission control.The multiple pollutants including H_(2)S,SO_(x),COS,NH_(3),HCN and NO_(x)cannot be eliminated by one-step treatment but a combination of adsorption and catalytic treatments may realize the control goal.This research aims to benefit meeting emission standards during MSW gasification and to provide a reference for other processes such as incineration,pyrolysis and other feedstocks like biomass and refuse derived fuel(RDF).展开更多
Plastic crystal neopentyl glycol(NPG)exhibits colossal barocaloric effect with high entropy changes.However,their application is restricted in several aspects,such as low thermal conductivity,substantial supercooling ...Plastic crystal neopentyl glycol(NPG)exhibits colossal barocaloric effect with high entropy changes.However,their application is restricted in several aspects,such as low thermal conductivity,substantial supercooling effect,and poor springback properties.In this work,multi-walled carbon nanotubes(MWCNTs)with ultra-high thermal conductivity and high mechanical strength were selected for performance enhancement of NPG.The optimal mixing ratio was determined to be NPG with 3 wt%MWCNTs composites,which showed a 6K reduction in supercooling without affecting the phase change enthalpy.Subsequently,comprehensive performance of the composites with optimal mixing ratio was compared with pure NPG At 40 MPa,390J·K^(-1)·kg^(-1)change in entropy and 9.9 K change in temperature were observed.Furthermore,the minimum driving pressure required to achieve reversible barocaloric effect was reduced by 19.2%.In addition,the thermal conductivity of the composite was increased by approximately 28%,significantly reducing the heat exchange time during a barocaloric refrigeration cycle.More importantly,ultra-high pressure release rate resulted in a73.7%reduction in the springback time of the composites,offering new opportunities for the recovery of expansion work.展开更多
Coal-direct chemical-looping combustion(CDCLC)is a promising coal combustion technique that provides CO2 capture with a low energy penalty.In this study,we developed a three-dimensional Eulerian-Eulerian multiphase fu...Coal-direct chemical-looping combustion(CDCLC)is a promising coal combustion technique that provides CO2 capture with a low energy penalty.In this study,we developed a three-dimensional Eulerian-Eulerian multiphase full-loop model for simulating the circulation and separation of binary particle mixtures in a novel high-flux CDCLC system.This model comprised a high-flux circulating fluidized bed as the fuel reactor(FR),a counter-flow moving bed as the air reactor(AR),a high-flux carbon stripper,two downcomers,and two J-valves.This model predicted the main features of complex gas-solid flow behaviors in the system.The simulation results showed that quasi-stable solid circulation in the whole system could be achieved,and the FR,AR,and J-valves operated in a dense suspension upflow regime,a near-plug-flow regime,and a bubbling fluidization regime,respectively.The multiphase flow model of binary particle mixtures was used to predict the mechanisms of directional separation of binary particle mixtures of an oxygen carrier(OC)and coal throughout the system.A decrease in the baffle aspect ratio of the inertial separator improved the coal selective separation efficiency but resulted in a slight decline in the OC selective separation;this is believed to be the result of weakening of particle collisions with the baffle.A higher FR gas velocity had a slightly negative effect on the OC selective separation efficiency,but improved the coal selective separation efficiency;this can be attributed to an increase in the particle-carrying capacity of the gas stream.A decrease in the coal particle size led to better entrainment of the coal particles by the gas stream and this increased the coal selective separation efficiency.In real CDCLC applications,the operating variables for separation of binary particle mixtures should be comprehensively assessed to determine their positive and negative effects on the carbon capture efficiency,OC regeneration efficiency,gas leakage restraint,energy consumption,and fuel conversion.展开更多
Discrete element method(DEM)was developed to simulate the corn-shaped particles flow in the hopper.The corn-shaped particle was described by four overlapping spheres.Contact force and gravity force were considered whe...Discrete element method(DEM)was developed to simulate the corn-shaped particles flow in the hopper.The corn-shaped particle was described by four overlapping spheres.Contact force and gravity force were considered when establishing the model.In addition,flowing characteristic of particles in the hopper was studied.The effect of friction coefficient on the wall pressure,voidage and velocity distribution was analyzed.The results show that the discharge rate decreases with the friction coefficient increasing;and the"over-pressure"phenomenon occurs in the discharging process for two different friction coefficients.The voidage also increases as the friction coefficient increasing.And the velocity distribution is more uniformity and is closer to the mass flow with the friction coefficient deceasing.展开更多
The combustion characteristics of bio-oils derived from rice husk and corn were studied by thermogravimetry analysis.According to the thermo-gravimetry(TG),differential thermogravimetry(DTG)and differential thermal an...The combustion characteristics of bio-oils derived from rice husk and corn were studied by thermogravimetry analysis.According to the thermo-gravimetry(TG),differential thermogravimetry(DTG)and differential thermal analysis(DTA)curves of bio-oils in air and nitrogen atmosphere,we analyzed the combustion characteristics of different kinds of bio-oils in different atmospheres and worked out the combustion kinetics parameters of the bio-oil,providing reliable base data for the burningofbio-oil.Thethermogravimetry indicatedthat the combustion process of bio-oil was divided into three stages.At the same time,the combustion process can be described by different order reaction models,and with the method of Coats-Redfern,the activation energy and frequency factor of different kinds of bio-oils were obtained.展开更多
Neodymium oxyfluoride has received much attention in the fields of anionic solid electrolytes.luminescent,catalytic and magnetic materials because of its structure combined advantages of rareearth cations with F^(-)an...Neodymium oxyfluoride has received much attention in the fields of anionic solid electrolytes.luminescent,catalytic and magnetic materials because of its structure combined advantages of rareearth cations with F^(-)and O_(2)^(-)anions.In this work,neodynium oxyfluoride was synthesized by the reaction between neodymium oxide and four fluoride media with different fluoride ion activities.The synthesis processes in molten LiF-CaF_(2)-NdF_(3),LiF-NdF_(3),NaF-CaF_(2)-NdF_(3)and NaF-KF-NdF_(3)are observed in situ by a confocal scanning laser microscope.The expansion of neodymium oxide particle is observed in the LiF-CaF_(2)-NdF_(3),LiF-NdF_(3),and NaF-KF-NdF_(3)melts,and the growth of needle crystals on neodymium oxide particle is clearly observed in molten NaF-CaF_(2)-NdF_(3).Based on scanning electron microscopy(SEM)-energy dispersive X-ray spectroscopy(EDS)and X-ray diffraction(XRD)analyses of products,neodynium oxyfluoride was successfully synthesized in the four fluoride media.The neodynium oxyfluoride generated in the LiF-CaF_(2)-NdF_(3),LiF-NdF_(3),and NaF-KF-NdF_(3)melts is a tetragonal structure.However,in molten NaF-CaF_(2)-NdF_(3),neodynium oxyfluoride with a rhombohedral structure is formed.It is suggested that the substitution of Na(Ⅰ)and Ca(Ⅱ)for Nd(Ⅲ)can transform NdOF from tetragonal structure to rhombohedral structure.The growth rate of needle crystals generated in molten NaF-CaF_(2)-NdF_(3)was calculated based on the result of a confocal scanning laser microscope,and it is found that the reaction kinetics of crystal formation is zero-order reaction.The effect of fluoride media on the structure and morphology of formed NdOF were evaluated by XRD,X-ray photoelectron spectroscopy(XPS)and SEM.The neodymium oxyfluoride prepared in the fluoride media with high fluoride ion activity has low binding energy of F 1 s.The ratio of adsorbed oxygen to lattice oxygen for neodymium oxyfluoride prepared in molten LiF-NdF_(3)is larger than those in the other three fluoride media,so it can have better catalytic performance.展开更多
Recent years have witnessed significant improvement in China’s air quality.Strict environmental protection measures have led to significant decreases in sulfur dioxide(SO2),nitrogen oxides(NOx),and particulate matter...Recent years have witnessed significant improvement in China’s air quality.Strict environmental protection measures have led to significant decreases in sulfur dioxide(SO2),nitrogen oxides(NOx),and particulate matter(PM)emissions since 2013.But there is no denying that the air quality in 135 cities is inferior to reaching the Ambient Air Quality Standards(GB 3095–2012)in 2020.In terms of temporal,geographic,and historical aspects,we have analyzed the potential connections between China’s air quality and the iron and steel industry.The non-target volatile organic compounds(VOCs)emissions from iron and steel industry,especially from the iron ore sinter process,may be an underappreciated index imposing a negative effect on the surrounding areas of China.Therefore,we appeal the authorities to pay more attention on VOCs emission from the iron and steel industry and establish new environmental standards.And different iron steel flue gas pollutants will be eliminated concurrently with the promotion and application of new technology.展开更多
Barocaloric refrigeration technology,one of the caloric-effect refrigeration technologies,is drawing more and more attention.Neopentyl glycol(NPG)was reported to have a giant barocaloric effect,making it a potential b...Barocaloric refrigeration technology,one of the caloric-effect refrigeration technologies,is drawing more and more attention.Neopentyl glycol(NPG)was reported to have a giant barocaloric effect,making it a potential barocaloric material.However,the high solid-solid(S-S)phase transition temperature and low thermal conductivity hinder the application of NPG in barocaloric refrigeration.This work lowers the S-S phase transition temperature and improves the thermal conductivity of the NPG-based barocaloric material.An NPG/TMP(TMP:Trimethylolpropane)binary system with an S-S phase transition temperature of 283.15 K is prepared,in which the mass ratio of TMP is 20%.Graphene is then added to the binary system to enhance thermal conductivity,and the optimal mass ratio of graphene was determined to be 5%.The thermal conductivity of this composite is 0.4 W/(m·K),increased by 110%compared to the binary system.To predict the effect of enhanced thermal conductivity on the cold-extraction process of the barocaloric refrigeration cycle,a numerical model is developed.The results show that the cold-extraction time of the barocaloric refrigeration cycle utilizing the composite with 5%graphene as the refrigerant is shortened by 50%compared with that using the binary system.展开更多
基金Supported by the International S&T Cooperation Program of China(ISTCP,2014DFE70150)the National Key R&D Program of China(2018YFC1901200)+1 种基金the Scientific Research Foundation of Graduate School of Southeast University(YBJJ1803)the UK-China Joint Research and Innovation Partnership Fund provided by China Scholarship Council and The British Council(201703780063)。
文摘The cheap manganese sand was first modified by H2O2 and was further creatively utilized as Ni-based catalyst support.In order to enhance the catalytic performance,Re was added into the Ni-based catalyst and the promotion effect of Re on the methanation coupling with water gas shift of biogas was investigated from the perspective of activation energy.It was found that CH4 and CO2 formation rates,which separately represented the reaction rate of methanation and water gas shift,were both enhanced after Re addition compared to non-added catalyst.Two kinetics models including empirical model and K-model were employed and from the results of calculation,it showed that Re selectively decreased the activation energy of methanation reaction and had little impact on the activation energy of water gas shift.The increased CO2 formation rate was owing to the assistance of accelerated H2O production from methanation rather than the activation energy change in water gas shift.
基金supported by the National Key Research and Development Program of China[Grant Number 2019YFC1906802].
文摘Methanation is an effective way to efficiently utilize product gas generated from the pyrolysis and gasification of organic solid wastes.To deeply study the heat transfer and mass transfer mechanisms in the reactor,a successful three-dimensional comprehensive model has been established.Multiphase flow behavior and heat transfer mechanisms were investigated under reference working conditions.Temperature is determined by the heat release of the reaction and the heat transfer of the gas-solid flow.The maximum temperature can reach 951 K where the catalyst gathers.In the simulation,changes in the gas inlet velocity and catalyst flow rate were made to explore their effects on CO conversion rate and temperature for optimization purposes.As the inlet gas velocity increases from 2.78 to 4.79 m/s,the CO conversion rate decreases from 81.6%to 72.4%.However,more heat is removed from the reactor,and the temperature rise increases from 78.03 to 113.49 K.When the catalyst flow rate is increased from 7.18 to 17.96 kg/(m^(2)·s),the mass of the catalyst in the reactor is increased from 0.0019 to 0.0042 kg,and the CO conversion rate is increased from 66.8%to 81.5%.However,this increases the maximum temperature in the reactor from 940.0 to 966.4 K.
基金Funding Statement:This work was supported by the National Key Research and Development Program of China[Grant No.2019YFC1906802].
文摘Organic solid waste(OSW)contains many renewable materials.The pyrolysis and gasification of OSW can realize resource utilization,and its products can be used for methanation reaction to produce synthetic natural gas in the specific reactor.In order to understand the dynamic characteristics of the reactor,a three-dimensional numerical model has been established by the method of Computational Fluid Dynamics(CFD).Along the height of the reactor,the particle distribution in the bed becomes thinner and the mean solid volume fraction decreases from 4.18%to 0.37%.Meanwhile,the pressure fluctuation range decreased from 398.76 Pa at the entrance to a much lower value of 74.47 Pa at the exit.In this simulation,three parameters of gas inlet velocity,operating temperature and solid particle diameter are changed to explore their influences on gas-solid multiphase flow.The results show that gas velocity has a great influence on particle distribution.When the gas inlet velocity decreases from 6.51 to 1.98 m/s,the minimum height that particles can reach decreases from 169 to 100 mm.Additionally,as the operating temperature increases,the particle holdup inside the reactor changes from 0.843%to 0.700%.This indicates that the particle residence time reduces,which is not conducive to the follow-up reaction.Moreover,with the increase of particle size,the fluctuation range of the pressure at the bottom of the reactor increases,and its standard deviation increases from 55.34 to 1266.37 Pa.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61774130 11474248,61176127,61006085,61274013,and 61306013the Key Program for International Science and Technology Cooperation Projects of China(Grant No.2011DFA62380)the Ph.D. Programs Foundation of the Ministry of Education of China(Grant No.20105303120002)
文摘In this paper, high material quality Al_(0.4) In_(0.6) AsSb quaternary alloy on GaSb substrates is demonstrated. The quality of these epilayers is assessed using a high-resolution x-ray diffraction, Fourier transform infrared(FTIR) spectrometer,and atomic force microscope(AFM). The x-ray diffraction exhibits high order satellite peaks with a measured period of 31.06 ?(theoretical value is 30.48 ?), the mismatch between the GaSb substrate and AlInAsSb achieves-162 arcsec,and the root-mean square(RMS) roughness for typical material growths has achieved around 1.6 ? over an area of 10 μm×10 μm. At room temperature, the photoluminescence(PL) spectrum shows a cutoff wavelength of 1.617 μm.
基金financial support from the China National Key R&D Program(Project No.2016YFB0600800)。
文摘Pressurised oxy-fuel combustion(POFC)is a clean and efficient combustion technology with great potential.Due to the recycling of flue gas,the concentration of steam in the flue gas is higher than that of conventional combustion,which enriches the free radical pool in the flue gas and thus affects the emission of gaseous pollutants.Therefore,further research into the effect of high steam concentrations on NO_(x)emission mechanisms in POFC is necessary.In this work,a fixed-bed reactor was used to conduct combustion experiments of volatiles and combined with chemical kinetic models to study the NO release characteristics for different pressures and steam concentrations in an O_(2)/CO_(2)atmosphere at 800℃/900℃temperature.The results of the study indicated that the volatile nitrogen comes from the pyrolysis of part of pyrrole,pyridine,and all quaternary nitrogen in coal.The increase in temperature promoted the formation of NO during combustion.Higher pressure affects the main reaction pathway for NO formation,promoting NO consumption by HCCO and C_(2)O groups while enhancing the overall NO reduction.Steam promoted NO consumption by NCO.In addition,steam increased the amount of H/OH groups during the reaction,which affected both NO formation and consumption.However,from the overall effect,the steam still inhibits the emission of NO.
基金supported by the Basic Research Program of Frontier Leading Technologies in Jiangsu Province(BK20202008)Hebei Natural Science Foundation(No.E2022210022)+1 种基金Science and Technology Project of Hebei Education Department(No.BJK2022056)the Introduction Program of Oversea Talents of Hebei Province(No.C20220505)。
文摘Barocaloric refrigeration is regarded as one of the next-generation alternative refrigeration technology due to its environmental friendliness.In recent years,many researchers have been devoted to finding materials with colossal barocaloric effects,while neglecting the research on barocaloric refrigeration devices and thermodynamic cycles.Neopentyl glycol is regarded as one of the potential refrigerants for barocaloric refrigeration due to its giant isothermal entropy changes and relatively low operating pressure.To evaluate the performance of the barocaloric system using Neopentyl glycol,for the first time,this study establishes a thermodynamic cycle based on the metastable temperature-entropy diagram.The performance of the proposed system is investigated from the aspects of irreversibility,operating temperature range,and operating pressure,and optimized with finite-rate heat transfer.The guidance for the optimal design of the system is given by revealing the effect of the irreversibility in two isobaric processes.The results show that a COP of 8.8 can be achieved at a temperature span of 10 K when the system fully uses the phase transition region of Neopentyl glycol,while a COP of 3 can be achieved at a temperature span of 10 K when the system operates at room temperature.Furthermore,this study also shows that the system performance can be further improved through the modification of Neopentyl glycol,and some future development guidance is provided.
基金supports by National Nature Science Foundation of China(grant No.51976037).
文摘Cycle Time Distribution(CTD)plays a critical role for determining uniformity of particle coating in spray fluidized beds.However,the CTD is influenced by both geometrical structure and operating conditions of fluidized bed.In this study,a spray fluidized bed of coating process is simulated by a comprehensive Computational Fluid Dynamics-Discrete Element Model(CFD-DEM).To achieve different behaviors of CTD,some modifications are designed on a pseudo-2D internally circulating fluidized bed,which traditionally composes of a high-velocity upward bed and low-velocity downward bed.These modifi-cations include making the air distributor slope and/or laying a baffle in the downward bed.First,the CTD and evolution of particle size distribution under different bed structures are compared.The CTD directly influences the coating uniformity.By making the particles flowing along a parallel direction in the downward bed through the geometrical modifications,the CTD becomes narrower and the coating uniformity is significantly improved.Second,under the optimized bed structure,the influence of oper-ating conditions on the coating uniformity is studied.Properly increasing the fluidization gas velocity and the fluidization gas temperature and reducing the liquid spray rate can improve the coating uniformity.
文摘The aim of this study is to propose a photovoltaic(PV)module simulation model with high accuracy under practical working conditions and strong applicability in the engineering field to meet various PV system simulation needs.Unlike previous model-building methods,this study combines the advantages of analytical and metaheuristic algorithms.First,the applicability of various metaheuristic algorithms is comprehensively compared and the seven parameters of the PV cell under standard test conditions are extracted using the double diode model,which verifies that the artificial hummingbird algorithm has higher accuracy than other algorithms.Then,the seven parameters under different conditions are corrected using the analytical method.In terms of the correc-tion method,the ideal factor correction is added on the basis of previous methods to solve the deviation between simulated data and measured data in the non-linear section.Finally,the root mean squared error between the simulated current data and the measured current data of the proposed model under three different temperatures and irradiance is 0.0697,0.0570 and 0.0289 A,respectively.
基金supported by the National Key R&D Program of China(Grant No.2019YFC1906803).
文摘This paper proposes a comprehensive summary and analysis of an important issue during municipal solid waste(MSW)gasification-sulfur and nitrogen pollution.It provides an overview of the fundamentals of MSW and the basic aspects of nitrogen and sulfur elements.Their characteristics of immigration,transformation and distribution during gasification with control solutions in realized or potential engineering are also concluded.The analysis indicates that the complete scenario of the occurrence form of sulfur and nitrogen elements in MSW is difficult to obtain,owing to the diverse sources and complicated compositions.However,with the assistance of advanced characterization and quantification methods(XPS,XRD,TG-FTIR,et al.),the common sulfur-and nitrogen-containing compounds in both organic and inorganic states can be detected.Adjustment of gasification conditions can regulate the transformation of these elements for emission control.The multiple pollutants including H_(2)S,SO_(x),COS,NH_(3),HCN and NO_(x)cannot be eliminated by one-step treatment but a combination of adsorption and catalytic treatments may realize the control goal.This research aims to benefit meeting emission standards during MSW gasification and to provide a reference for other processes such as incineration,pyrolysis and other feedstocks like biomass and refuse derived fuel(RDF).
基金supported by the Basic Research Program of Frontier Leading Technologies in Jiangsu Province(BK20202008)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX23_0240)+3 种基金the key research and demonstration projects of future low-carbon emission buildings(No.BE2022606)Hebei Natural Science Foundation(No.E2022210022)Science and Technology Project of Hebei Education Department(No.BJK2022056)the Introduction Program of Oversea Talents of Hebei Province(No.C20220505)。
文摘Plastic crystal neopentyl glycol(NPG)exhibits colossal barocaloric effect with high entropy changes.However,their application is restricted in several aspects,such as low thermal conductivity,substantial supercooling effect,and poor springback properties.In this work,multi-walled carbon nanotubes(MWCNTs)with ultra-high thermal conductivity and high mechanical strength were selected for performance enhancement of NPG.The optimal mixing ratio was determined to be NPG with 3 wt%MWCNTs composites,which showed a 6K reduction in supercooling without affecting the phase change enthalpy.Subsequently,comprehensive performance of the composites with optimal mixing ratio was compared with pure NPG At 40 MPa,390J·K^(-1)·kg^(-1)change in entropy and 9.9 K change in temperature were observed.Furthermore,the minimum driving pressure required to achieve reversible barocaloric effect was reduced by 19.2%.In addition,the thermal conductivity of the composite was increased by approximately 28%,significantly reducing the heat exchange time during a barocaloric refrigeration cycle.More importantly,ultra-high pressure release rate resulted in a73.7%reduction in the springback time of the composites,offering new opportunities for the recovery of expansion work.
基金This work was financially supported by the National Natu-ral Science Foundation of China(51806035)the Natural Science Foundation of Jiangsu Province(BK20170669)+1 种基金the Fundamental Research Funds for the Central Universities(2242018K40117)the Guangdong Provincial Key Laboratory of New and Renewable Energy Research and Development(Y707s41001).
文摘Coal-direct chemical-looping combustion(CDCLC)is a promising coal combustion technique that provides CO2 capture with a low energy penalty.In this study,we developed a three-dimensional Eulerian-Eulerian multiphase full-loop model for simulating the circulation and separation of binary particle mixtures in a novel high-flux CDCLC system.This model comprised a high-flux circulating fluidized bed as the fuel reactor(FR),a counter-flow moving bed as the air reactor(AR),a high-flux carbon stripper,two downcomers,and two J-valves.This model predicted the main features of complex gas-solid flow behaviors in the system.The simulation results showed that quasi-stable solid circulation in the whole system could be achieved,and the FR,AR,and J-valves operated in a dense suspension upflow regime,a near-plug-flow regime,and a bubbling fluidization regime,respectively.The multiphase flow model of binary particle mixtures was used to predict the mechanisms of directional separation of binary particle mixtures of an oxygen carrier(OC)and coal throughout the system.A decrease in the baffle aspect ratio of the inertial separator improved the coal selective separation efficiency but resulted in a slight decline in the OC selective separation;this is believed to be the result of weakening of particle collisions with the baffle.A higher FR gas velocity had a slightly negative effect on the OC selective separation efficiency,but improved the coal selective separation efficiency;this can be attributed to an increase in the particle-carrying capacity of the gas stream.A decrease in the coal particle size led to better entrainment of the coal particles by the gas stream and this increased the coal selective separation efficiency.In real CDCLC applications,the operating variables for separation of binary particle mixtures should be comprehensively assessed to determine their positive and negative effects on the carbon capture efficiency,OC regeneration efficiency,gas leakage restraint,energy consumption,and fuel conversion.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.50706007 and 50976025)National Key Program of Basic Research in China(No.2010CB732206)the Foundation of Excellent Young Scholar of Southeast University(4003001039).
文摘Discrete element method(DEM)was developed to simulate the corn-shaped particles flow in the hopper.The corn-shaped particle was described by four overlapping spheres.Contact force and gravity force were considered when establishing the model.In addition,flowing characteristic of particles in the hopper was studied.The effect of friction coefficient on the wall pressure,voidage and velocity distribution was analyzed.The results show that the discharge rate decreases with the friction coefficient increasing;and the"over-pressure"phenomenon occurs in the discharging process for two different friction coefficients.The voidage also increases as the friction coefficient increasing.And the velocity distribution is more uniformity and is closer to the mass flow with the friction coefficient deceasing.
基金Financial support came from the National Basic Research Program of China(973 Program,2007CB210208)National Natural Science Foundation-funded projects(50776019)Ministry of Education to support the new century talents Scheme(NCET-05-0469).
文摘The combustion characteristics of bio-oils derived from rice husk and corn were studied by thermogravimetry analysis.According to the thermo-gravimetry(TG),differential thermogravimetry(DTG)and differential thermal analysis(DTA)curves of bio-oils in air and nitrogen atmosphere,we analyzed the combustion characteristics of different kinds of bio-oils in different atmospheres and worked out the combustion kinetics parameters of the bio-oil,providing reliable base data for the burningofbio-oil.Thethermogravimetry indicatedthat the combustion process of bio-oil was divided into three stages.At the same time,the combustion process can be described by different order reaction models,and with the method of Coats-Redfern,the activation energy and frequency factor of different kinds of bio-oils were obtained.
基金Project supported by National Key Research and Development Program of China(2020YFC1909102)Natural Science Foundation of Inner Mongolia(2020BS05033)+1 种基金Inner Mongolia Major Basic Research Open Project(0406091701)Major Projects of Natural Science Foundation of Inner Mongolia of China(2018ZD07)。
文摘Neodymium oxyfluoride has received much attention in the fields of anionic solid electrolytes.luminescent,catalytic and magnetic materials because of its structure combined advantages of rareearth cations with F^(-)and O_(2)^(-)anions.In this work,neodynium oxyfluoride was synthesized by the reaction between neodymium oxide and four fluoride media with different fluoride ion activities.The synthesis processes in molten LiF-CaF_(2)-NdF_(3),LiF-NdF_(3),NaF-CaF_(2)-NdF_(3)and NaF-KF-NdF_(3)are observed in situ by a confocal scanning laser microscope.The expansion of neodymium oxide particle is observed in the LiF-CaF_(2)-NdF_(3),LiF-NdF_(3),and NaF-KF-NdF_(3)melts,and the growth of needle crystals on neodymium oxide particle is clearly observed in molten NaF-CaF_(2)-NdF_(3).Based on scanning electron microscopy(SEM)-energy dispersive X-ray spectroscopy(EDS)and X-ray diffraction(XRD)analyses of products,neodynium oxyfluoride was successfully synthesized in the four fluoride media.The neodynium oxyfluoride generated in the LiF-CaF_(2)-NdF_(3),LiF-NdF_(3),and NaF-KF-NdF_(3)melts is a tetragonal structure.However,in molten NaF-CaF_(2)-NdF_(3),neodynium oxyfluoride with a rhombohedral structure is formed.It is suggested that the substitution of Na(Ⅰ)and Ca(Ⅱ)for Nd(Ⅲ)can transform NdOF from tetragonal structure to rhombohedral structure.The growth rate of needle crystals generated in molten NaF-CaF_(2)-NdF_(3)was calculated based on the result of a confocal scanning laser microscope,and it is found that the reaction kinetics of crystal formation is zero-order reaction.The effect of fluoride media on the structure and morphology of formed NdOF were evaluated by XRD,X-ray photoelectron spectroscopy(XPS)and SEM.The neodymium oxyfluoride prepared in the fluoride media with high fluoride ion activity has low binding energy of F 1 s.The ratio of adsorbed oxygen to lattice oxygen for neodymium oxyfluoride prepared in molten LiF-NdF_(3)is larger than those in the other three fluoride media,so it can have better catalytic performance.
基金supported by the Key Research and Development Program of Henan Province(No.212102310506)Financial support from the National Natural Science Foundation(No.K2022QN027)+1 种基金the Postgraduate Education Quality Improving Project(No.JG202217)the Discipline Strength Improving Project of Zhongyuan University of Technology(No.SD202242)were also acknowledged.
文摘Recent years have witnessed significant improvement in China’s air quality.Strict environmental protection measures have led to significant decreases in sulfur dioxide(SO2),nitrogen oxides(NOx),and particulate matter(PM)emissions since 2013.But there is no denying that the air quality in 135 cities is inferior to reaching the Ambient Air Quality Standards(GB 3095–2012)in 2020.In terms of temporal,geographic,and historical aspects,we have analyzed the potential connections between China’s air quality and the iron and steel industry.The non-target volatile organic compounds(VOCs)emissions from iron and steel industry,especially from the iron ore sinter process,may be an underappreciated index imposing a negative effect on the surrounding areas of China.Therefore,we appeal the authorities to pay more attention on VOCs emission from the iron and steel industry and establish new environmental standards.And different iron steel flue gas pollutants will be eliminated concurrently with the promotion and application of new technology.
基金supported by the Basic Research Program of Frontier Leading Technologies in Jiangsu Province(BK20202008).
文摘Barocaloric refrigeration technology,one of the caloric-effect refrigeration technologies,is drawing more and more attention.Neopentyl glycol(NPG)was reported to have a giant barocaloric effect,making it a potential barocaloric material.However,the high solid-solid(S-S)phase transition temperature and low thermal conductivity hinder the application of NPG in barocaloric refrigeration.This work lowers the S-S phase transition temperature and improves the thermal conductivity of the NPG-based barocaloric material.An NPG/TMP(TMP:Trimethylolpropane)binary system with an S-S phase transition temperature of 283.15 K is prepared,in which the mass ratio of TMP is 20%.Graphene is then added to the binary system to enhance thermal conductivity,and the optimal mass ratio of graphene was determined to be 5%.The thermal conductivity of this composite is 0.4 W/(m·K),increased by 110%compared to the binary system.To predict the effect of enhanced thermal conductivity on the cold-extraction process of the barocaloric refrigeration cycle,a numerical model is developed.The results show that the cold-extraction time of the barocaloric refrigeration cycle utilizing the composite with 5%graphene as the refrigerant is shortened by 50%compared with that using the binary system.
