Deep-sea pipelines play a pivotal role in seabed mineral resource development,global energy and resource supply provision,network communication,and environmental protection.However,the placement of these pipelines on ...Deep-sea pipelines play a pivotal role in seabed mineral resource development,global energy and resource supply provision,network communication,and environmental protection.However,the placement of these pipelines on the seabed surface exposes them to potential risks arising from the complex deep-sea hydrodynamic and geological environment,particularly submarine slides.Historical incidents have highlighted the substantial damage to pipelines due to slides.Specifically,deep-sea fluidized slides(in a debris/mud flow or turbidity current physical state),characterized by high speed,pose a significant threat.Accurately assessing the impact forces exerted on pipelines by fluidized submarine slides is crucial for ensuring pipeline safety.This study aimed to provide a comprehensive overview of recent advancements in understanding pipeline impact forces caused by fluidized deep-sea slides,thereby identifying key factors and corresponding mechanisms that influence pipeline impact forces.These factors include the velocity,density,and shear behavior of deep-sea fluidized slides,as well as the geometry,stiffness,self-weight,and mechanical model of pipelines.Additionally,the interface contact conditions and spatial relations were examined within the context of deep-sea slides and their interactions with pipelines.Building upon a thorough review of these achievements,future directions were proposed for assessing and characterizing the key factors affecting slide impact loading on pipelines.A comprehensive understanding of these results is essential for the sustainable development of deep-sea pipeline projects associated with seabed resource development and the implementation of disaster prevention measures.展开更多
In order to avoid the formation ofηphase(W_(6)Co_(6)C or W_(3)Co_(3)C)that adversely affects the sintering process and its products in the preparation process of ultra-fine WC-Co powder,a technical route of prereduct...In order to avoid the formation ofηphase(W_(6)Co_(6)C or W_(3)Co_(3)C)that adversely affects the sintering process and its products in the preparation process of ultra-fine WC-Co powder,a technical route of prereduction of WO_(3)-Co_(3)O_(4)to WO_(2)-Co and then deep reduction carbonization to WC-Co powder has been proposed.This study mainly investigates the influence of gas partial pressure on the pre-reduction process of WO_(3)-Co_(3)O_(4)under a mixed atmosphere of H_(2)-C_(2)H_(4)-Ar at 600℃and establishes the kinetic equations of pre-reduction and carbon evolution.The results indicate that increasing the partial pressure of hydrogen is conducive to the rapid and complete conversion of WO_(3) to WO_(2).High carbon content can be generated by the deposition of C_(2)H_(4),and it hinders the diffusion of the reducing gas;WO_(3)still cannot be completely reduced to WO_(2)as the partial pressure of C_(2)H_(4) increases to 60%.For the carbon evolution of C_(2)H_(4),the carbon amount is positively related to the H_(2)partial pressure,but it shows the highest amount and evolution rate when the ethylene partial pressure is 20%.Based on the reduction rate curves of WO_(3) and carbon evolution rate curves of C_(2)H_(4),the rate equations of pre-reduction and carbon evolution of WO_(3)-Co_(3)O_(4)system at 600℃are established.The pre-reduction reaction belongs to the first-order reaction,and its equation is expressed as follows:r=-(dw_(WO_(3)))/dt=(9±0.15)×10^(-2)×P_(H_(2))^(0.44)P_(C_(2)H_(4))&(0.57)The carbon deposition rate equation of C_(2)H_(4) can be expressed as follows:r=-(dc_C)/dt=r_f-r_b≌7.35×10^(-2)×P_(C_(2)H_(4))^(0.31)展开更多
Using a newly developed experimental setup,the features and advantages of an autothermal single-casing atmospheric sub-bituminous coal fluidized bed air-blown gasifier,combining a combustion and gasification section,a...Using a newly developed experimental setup,the features and advantages of an autothermal single-casing atmospheric sub-bituminous coal fluidized bed air-blown gasifier,combining a combustion and gasification section,and mixing the dispersed phase(inert material,char)and heat exchange between them through an annular transfer device,have been revealed.To increase the efficiency of the gasifier,an experimental-computational method was developed find the conditions for optimal operation,combining changing the annular flow's geometry and regulating the primary air for gasification.A simple and reliable multizone thermodynamic calculation model makes it possible to predict the composition of char and syngas in the gasification section with acceptable accuracy.This method confirmed that a two-section fluidized bed gasifier can provide efficient gasification of solid fuels and is suitable for use in small-scale cogeneration plants.Syngas with a heating value of 3.6-4.5 MJ/m^(3)and CGE of 38.2%-42.3%was obtained in the experimental setup without optimizing the primary air flow rate.With optimization,the indicators increased to the heating value of syngas of 5.20-5.34 MJ/m^(3)and CGE of 42.5%-50.0%.With heat regeneration of 0.8,CGE increases to 70%.展开更多
A set of hydrodynamic similarity laws is applied to the scale-up of ethylene polymerization fluidized bed reactors(FBRs)under the condensed mode operation.The thermal stability of open-loop controlled FBRs is investig...A set of hydrodynamic similarity laws is applied to the scale-up of ethylene polymerization fluidized bed reactors(FBRs)under the condensed mode operation.The thermal stability of open-loop controlled FBRs is investigated by the homotopy continuation method.And the Hopf bifurcation point is selected as an index of the thermal stability similarity.The simulation results show the similarity in state variables,operation parameters,the space-time yield(STY),and the thermal stability of FBRs with different scales.Furthermore,the thermal stability behaviors and similarity of the closed-loop controlled FBRs with different scales are analyzed.The observed similar trend of Hopf bifurcation curves reveals the similarity in the thermal stability of closed-loop controlled FBRs with different scaling ratios.In general,the results of the thermal stability similarity confirm that the hydrodynamics scaling laws proposed in the work are applicable to the scale-up of FBRs under the condensed mode operation.展开更多
In this study,the open-source software MFIX-DEM simulations of a bubbling fluidized bed(BFB)are applied to assess nine drag models according to experimental and direct numerical simulation(DNS)results.The influence of...In this study,the open-source software MFIX-DEM simulations of a bubbling fluidized bed(BFB)are applied to assess nine drag models according to experimental and direct numerical simulation(DNS)results.The influence of superficial gas velocity on gas–solid flow is also examined.The results show that according to the distribution of time-averaged particle axial velocity in y direction,except for Wen–Yu and Tenneti–Garg–Subramaniam(TGS),other drag models are consistent with the experimental and DNS results.For the TGS drag model,the layer-by-layer movement of particles is observed,which indicates the particle velocity is not correctly predicted.The time domain and frequency domain analysis results of pressure drop of each drag model are similar.It is recommended to use the drag model derived from DNS or fine grid computational fluid dynamics–discrete element method(CFD-DEM)data first for CFD-DEM simulations.For the investigated BFB,the superficial gas velocity less than 0.9 m·s^(-1) should be adopted to obtain normal hydrodynamics.展开更多
A liquid-solid circulating fluidized bed boiler is designed and built for visualization research by applying the fluidized bed heat transfer and fouling prevention technology to the water side of the boiler. Four type...A liquid-solid circulating fluidized bed boiler is designed and built for visualization research by applying the fluidized bed heat transfer and fouling prevention technology to the water side of the boiler. Four types of engineering plastic particles with different physical properties are selected as the solid working media. The effect of particle types on the fluidization and distribution of particles in the boiler is investigated under different feedwater flow rates and amount of added particles by using the charge couple device image measurement and acquisition system. The results show that all kinds of particles can't be normally fluidized and accumulate in the drum at low amount of added particles and feedwater flow rate. The particles with great density and low sphericity are more likely to accumulate. The average solid holdup in the riser tubes increases with the increase in feedwater flow rate and the amount of added particles. The non-uniform degree of particle distribution in the riser tubes generally decreases with the increase in feedwater flow rate and the amount of added particles. The particles with small density and settling velocity have high average solid holdup in the riser tubes under close sphericity. In generally,the smaller the density and settling velocity, the more uniform the particle distribution in the riser tubes.Three-dimensional diagrams of the non-uniform degree of particle distribution in the riser tubes of the boiler are established.展开更多
The regeneration of fluidized catalytic cracking(FCC)catalysts is an essential process in petroleum processing.The current study focused the regeneration reaction characteristics of spent fluidized catalytic cracking ...The regeneration of fluidized catalytic cracking(FCC)catalysts is an essential process in petroleum processing.The current study focused the regeneration reaction characteristics of spent fluidized catalytic cracking catalyst(SFCC)at different atmospheres with influences on pore evolution and activity,for a potential way to reduce emission,produce moderate chemical product(CO),and maintain catalyst activity.The results show that regeneration in air indicates a satisfaction on removing coke on the catalyst surface while giving a poor effect on eliminating the coke inside micropores.This is attributed that the combustion in air led to a higher temperature and further transformed kaolinite phase to silicaaluminum spinel crystals,which tended to collapse and block small pores or expand large pores,with similar results observed in pure O_(2)atmosphere.Nevertheless,catalysts regenerated in O_(2)/CO_(2)diminished the combustion damage to the pore structure,of which the micro porosity after regeneration increased by 32.4% and the total acid volume rose to 27.1%.The regeneration in pure CO_(2)displayed low conversion rate due to the endothermic reaction and low reactivity.The coexistence of gasification and partial oxidation can promote regeneration and maintain the original structure and good reactivity.Finally,a mechanism of the regeneration reaction at different atmospheres was revealed.展开更多
Jets caused by burst tubes erode the surrounding soil, eventually leading to issues such as ground collapse. It is therefore highly important to study the mechanisms of soil erosion caused by jets after pipeline leaka...Jets caused by burst tubes erode the surrounding soil, eventually leading to issues such as ground collapse. It is therefore highly important to study the mechanisms of soil erosion caused by jets after pipeline leakage. To investigate the water-soil interaction mechanisms of pipe leakage, this study used transparent soil and developed a three-dimensional experimental device to observe the fluidization process. Changes in the boundary of the fluidization transition area were investigated, and a formula for calculating the soil damage area was derived. The results showed three different shapes of the fluidized cavity appearing in the fluidization process. The particles initially moved upward and then gradually transitioned into a state of backflow. The effects of particle size, upper load, and porosity on fluidization were also analyzed. It was found that soil with a large particle size and a lower porosity under a heavy upper load can effectively restrain fluidization. Therefore, large-diameter and dense soil can be used as pipe-covering material.展开更多
Magnetization roasting is one of the most effective way of utilizing low-grade refractory iron ore.However,the reduction roasting of siderite(FeCO3)generates weakly magnetic wüstite,thus reducing iron recovery vi...Magnetization roasting is one of the most effective way of utilizing low-grade refractory iron ore.However,the reduction roasting of siderite(FeCO3)generates weakly magnetic wüstite,thus reducing iron recovery via weak magnetic separation.We systematically studied and proposed the fluidized preoxidation-low-temperature reduction magnetization roasting process for siderite.We found that the maghemite generated during the air oxidation roasting of siderite would be further reduced into wüstite at 500 and 550℃due to the unstable intermediate product magnetite(Fe_(3)O_(4)).Stable magnetite can be obtained through maghemite reduction only at low temperature.The optimal fluidized magnetization roasting parameters included preoxidation at 610℃for 2.5 min,followed by reduction at 450℃for 5 min.For roasted ore,weak magnetic separation yielded an iron ore concentrate grade of 62.0wt%and an iron recovery rate of 88.36%.Compared with that of conventional direct reduction magnetization roasting,the iron recovery rate of weak magnetic separation had greatly improved by 34.33%.The proposed fluidized preoxidation-low-temperature reduction magnetization roasting process can realize the efficient magnetization roasting utilization of low-grade refractory siderite-containing iron ore without wüstite generation and is unlimited by the proportion of siderite and hematite in iron ore.展开更多
The negative pressure conical fluidized bed is widely used in the pharmaceutical industry.In this study,experiments based on the negative pressure conical fluidized bed are carried out by changing the material mass an...The negative pressure conical fluidized bed is widely used in the pharmaceutical industry.In this study,experiments based on the negative pressure conical fluidized bed are carried out by changing the material mass and particle size.The pressure fluctuation signals are analyzed by the time and the frequency domain methods.A method for absolutely characterizing the degree of the energy concentration at the main frequency is proposed,where the calculation is to divide the original power spectrum by the average signal power.A phenomenon where the gas velocity curve temporarily stops growing is observed when the material mass is light,and the particle size is small.The standard deviation and kurtosis both rapidly change at the minimum fluidization velocity and thus can be used to determine the flow regime,and the variation rule of the kurtosis is independent of both the material mass and particle size.In the initial fluidization stage,the dominant pressure signal comes from the material movement;with the increase in the gas velocity,the power of a 2.5 Hz signal continues to increase.A method of dividing the main frequency by the average cycle frequency can conveniently determine the fluidized state,and a novel concept called stable fluidized zone proposed in this paper can be obtained.Controlling the gas velocity within the stable fluidized zone ensures that the fluidized bed consistently remains in a stable fluidized state.展开更多
An analysis approach considering gas-solids hydrodynamics,reaction kinetics and reacting species nonuniformity together in a dual-reactor system is presented for better understanding its mass and energy balance.It was...An analysis approach considering gas-solids hydrodynamics,reaction kinetics and reacting species nonuniformity together in a dual-reactor system is presented for better understanding its mass and energy balance.It was achieved by a 3-dimensional comprehensive hydrodynamics and reaction model for the dual-reactor system,which was developed from the successfully verified 3-dimensional comprehensive combustion model for one circulating fluidized bed(CFB)system(Xu and Cheng,2019).The developed model and analysis approach was successfully used on a 1 MW circulating fluidized bed–bubbling fluidized bed(CFB-BFB)dual-reactor system.Results showed the sensible and chemical energy between two reactors as well as the energy distributions in each reactor were balanced and they agreed well with the experimental measurements.The analysis approach indicated energy balance had a close relationship with the mass transfer in the CFB-BFB dual-reactor system.It may be applied in a design and operation optimization for a dual-reactor system.展开更多
To improve the efficiency of a CycloBio fluidized sand bed(CB FSB) in removal of dissolved wastes in recirculating aquaculture systems, the hydrodynamics of solid-liquid flow was investigated using computational fluid...To improve the efficiency of a CycloBio fluidized sand bed(CB FSB) in removal of dissolved wastes in recirculating aquaculture systems, the hydrodynamics of solid-liquid flow was investigated using computational fluid dynamics(CFD) modeling tools. The dynamic characteristics of silica sand within the CB FSB were determined using three-dimensional, unsteady-state simulations with the granular Eulerian multiphase approach and the RNG k-ε turbulence model, and the simulation results were validated using available lab-scale measurements. The bed expansion of CB FSB increased with the increase in water inflow rate in numerical simulations. Upon validation, the simulation involving 0.55 mm particles, the Gidaspow correlation for drag coefficient model and the Syamlal-O'Brien correlation for kinetic granular viscosity showed the closest match to the experimental results. The volume fraction of numerical simulations peaked as the wall was approached. The hydrodynamics of a pilot-scale CB FSB was simulated in order to predict the range of water flow to avoid the silica sand overflowing. The numerical simulations were in agreement with the experimental results qualitatively and quantitatively, and thus can be used to study the hydrodynamics of solid-liquid multiphase flow in CB FSB, which is of importance to the design, optimization, and amplification of CB FSBs.展开更多
An experimental study on co-pyrolysis of bituminous coal and biomass was performed in a pressured fluidized bed reactor.The blend ratio of biomass in the mixture was varied between 0 and 100 wt%,and the temperature wa...An experimental study on co-pyrolysis of bituminous coal and biomass was performed in a pressured fluidized bed reactor.The blend ratio of biomass in the mixture was varied between 0 and 100 wt%,and the temperature was over a range of 550–650℃ under 1.0 MPa pressure with different atmospheres.On the basis of the individual pyrolysis behavior of bituminous coal and biomass,the influences of the biomass blending ratio,temperature,pressure and atmosphere on the product distribution were investigated.The results indicated that there existed a synergetic effect in the co-pyrolysis of bituminous coal and biomass in this pressured fluidized bed reactor,especially when the condition of bituminous coal and biomass blend ratio of 70:30(w/w),600℃,and 0.3 MPa was applied.The addition of biomass influenced the tar and char yields and gas and tar composition during co-pyrolysis.The tar yields were higher than the calculated values from individual pyrolysis of each fuel,and consequently the char yields were lower.The experimental results showed that the composition of the gaseous products was not in accordance with those of their individual fuel.The improvement of composition in tar also indicated synergistic effect in the co-pyrolysis.展开更多
AIM:To construct and evaluate the functionality of a choanoid-fluidized bed bioreactor(CFBB)based on microencapsulated immortalized human hepatocytes.METHODS:Encapsulated hepatocytes were placed in the constructed CFB...AIM:To construct and evaluate the functionality of a choanoid-fluidized bed bioreactor(CFBB)based on microencapsulated immortalized human hepatocytes.METHODS:Encapsulated hepatocytes were placed in the constructed CFBB and circulated through Dulbecco’s Modified Eagle’s Medium(DMEM)for 12 h,and then through exchanged plasma for 6 h,and compared with encapsulated cells cultivated under static conditions in a spinner flask.Levels of alanine aminotransferase(ALT)and albumin were used to evaluate the CFBB during media circulation,whereas levels of ALT,total bilirubin(TBil),and albumin were used to evaluate it during plasma circulation.Mass transfer and hepatocyte injury were evaluated by comparing the results from the two experimental conditions.In addition,the viability and microstructure of encapsulated cells were observed in the different environments.RESULTS:The bioartificial liver model based on a CFBB was verified by in vitro experiments.The viability of encapsulated cells accounting for 84.6%±3.7%in CFBB plasma perfusion was higher than the 74.8%±3.1%in the static culture group(P<0.05)after 6 h.ALT release from cells was 29±3.5 U/L vs 40.6±3.2U/L at 12 h(P<0.01)in the CFBB medium circulation and static medium culture groups,respectively.Albumin secretion from cells was 234.2±27.8μg/1×107cells vs 167.8±29.3μg/1×107 cells at 6 h(P<0.01),274.4±34.6μg/1×107 cells vs 208.4±49.3μg/1×107 cells(P<0.05)at 12 h,in the two medium circulation/culture groups,respectively.Furthermore,ALT and TBil levels were 172.3±24.1 U/L vs 236.3±21.5 U/L(P<0.05),240.1±23.9μmol/L vs 241.9±31.4μmol/L(P>0.05)at 6 h in the CFBB plasma perfusion and static plasma culture groups,respectively.There was no significant difference in albumin concentration between the two experimental plasma groups at any time point.The microstructure of the encapsulated hepatocytes remained healthier in the CFBB group compared with the static culture group after 6 h of plasma perfusion.CONCLUSION:The CFBB can function as a bioartificial liver based on a bioreactor.The efficacy of this novel bioreactor is promising for the study of liver failure.展开更多
Traditional coal mining and utilisation patterns are severely detrimental to natural resources and environments and significantly impede safe, low-carbon, clean, and sustainable utilisation of coal resources. Based on...Traditional coal mining and utilisation patterns are severely detrimental to natural resources and environments and significantly impede safe, low-carbon, clean, and sustainable utilisation of coal resources. Based on the idea of in situ fluidized coal mining that aims to transform solid coal into liquid or gas and transports the fluidized resources to the ground to ensure safe mining and low-carbon and clean utilisation, in this study, we report on a novel in situ unmanned automatic mining method. This includes a flexible, earthworm-like unmanned automatic mining machine (UAMM) and a coal mine layout for in situ fluidized coal mining suitable for the UAMM. The technological and economic advantages and the carbon emission reduction of the UAMM-based in situ fluidized mining in contrast to traditional mining technologies are evaluated as well. The development trends and possible challenges to this design are also discussed. It is estimated that the proposed method costs approximately 49% of traditional coal mining costs. The UAMM-based in situ fluidized mining and transformation method will reduce CO2 emissions by at least 94.9% compared to traditional coal mining and utilisation methods. The proposed approach is expected to achieve safe and environmentally friendly coal mining as well as lowcarbon and clean utilisation of coal.展开更多
Abstract:The aim of this research is to design and operate a 10 kW hot chemical-looping gasification(CLG)unit using Fe2O3/Al2O3as an oxygen carrier and saw dust as a fuel.The effect of the operation temperature on gas...Abstract:The aim of this research is to design and operate a 10 kW hot chemical-looping gasification(CLG)unit using Fe2O3/Al2O3as an oxygen carrier and saw dust as a fuel.The effect of the operation temperature on gas composition in the air reactor and the fuel reactor,and the carbon conversion of biomass to CO2and CO in the fuel reactor have been experimentally studied.A total60 h run has been obtained with the same batch of oxygen carrier of iron oxide supported with alumina.The results show that CO and H2concentrations are increased with increasing temperature in the fuel reactor.It is also found that with increasing fuel reactor temperature,both the amount of residual char in the fuel reactor and CO2concentration of the exit gas from the air reactor are degreased.Carbon conversion rate and gasification efficiency are increased by increasing temperature and H2production at 870℃reaches the highest rate.Scanning electron microscopy(SEM),X-ray diffraction(XRD)and BET-surface area tests have been used to characterize fresh and reacted oxygen carrier particles.The results display that the oxygen carrier activity is not declined and the specific surface area of the oxygen carrier particles is not decreased significantly.展开更多
A fluidized bed jet milling process was used to make micro-fine high Nb-containing TiAl alloyed powders from the chippings obtained by crushing the Ti-45Al-8.5Nb-(W,B,Y) ingot.The influences of classifier frequency on...A fluidized bed jet milling process was used to make micro-fine high Nb-containing TiAl alloyed powders from the chippings obtained by crushing the Ti-45Al-8.5Nb-(W,B,Y) ingot.The influences of classifier frequency on powder characteristics were investigated.The results show that the powders with controlled average particle size can be prepared on a large scale.The powders with different sizes are all dominated by γ with aminor amount of α2-Ti3Al.The particle size significantly decreases with the classifier frequency increasing.At a classifier frequency higher than 38 Hz,the average particle size of the ground powders is lower than 25μm.The powders are composed of two differ-ent sizes of particles:shaped particles and some clastic particles,and both particle sizes meet the log-normal distribution.With the classifier frequency increasing,the both sizes decrease;meanwhile,the proportion of the clastic particles gradually increases,and the size distribution span value of the ground powders increases correspondingly.展开更多
In this work,syngas methanation over Ni-W/TiO2-SiO2catalyst was studied in a fluidized-bed reactor(FBR)and its performance was compared with a fixed-bed reactor(FIXBR).The effects of main operating variables including...In this work,syngas methanation over Ni-W/TiO2-SiO2catalyst was studied in a fluidized-bed reactor(FBR)and its performance was compared with a fixed-bed reactor(FIXBR).The effects of main operating variables including feedstock gases space velocity,coke content,bed temperature and sulfur-tolerant stability of 100 h life were investigated.The structure of the catalysts was characterized by XRD,N2adsorptiondesorption and TEM.It is found that under same space velocity from 5000 h 1to 25000 h 1FBR gave a higher CH4yield,lower coke content,and lower bed temperature than those obtained in FIXBR.Ni-W/TiO2-SiO2catalyst possessed excellent sulfur-tolerant stability on the feedstock gases less than 500 ppm H2S in FBR.The carbon deposits formed on the spent catalyst were in the form of carbon fibers in FBR,while in the form of dense accumulation distribution appearance in FIXBR.展开更多
A magnetically stabilized fluidized bed (MSB) is a highly efficient filter that takes the advantage of both fluidized beds and fixed beds. This paper presents the research to collect aerosol in airflow with a MSB. The...A magnetically stabilized fluidized bed (MSB) is a highly efficient filter that takes the advantage of both fluidized beds and fixed beds. This paper presents the research to collect aerosol in airflow with a MSB. The filtering model of MSB is established with its parameters including magnetic field intensity, gas superficial velocity, average grain size, and bed height on the collection efficiency of MSB. The model is verified by experiments.展开更多
基金supported by the opening fund of State Key Laboratory of Coastal and Offshore Engineering at Dalian University of Technology(No.LP2310)the opening fund of State Key Laboratory of Geohazard Prevention and Geoenvironment Protection at Chengdu University of Technology(No.SKLGP2023K001)+2 种基金the Shandong Provincial Key Laboratory of Ocean Engineering with grant at Ocean University of China(No.kloe200301)the National Natural Science Foundation of China(Nos.42022052,42077272 and 52108337)the Science and Technology Innovation Serve Project of Wenzhou Association for Science and Technology(No.KJFW65).
文摘Deep-sea pipelines play a pivotal role in seabed mineral resource development,global energy and resource supply provision,network communication,and environmental protection.However,the placement of these pipelines on the seabed surface exposes them to potential risks arising from the complex deep-sea hydrodynamic and geological environment,particularly submarine slides.Historical incidents have highlighted the substantial damage to pipelines due to slides.Specifically,deep-sea fluidized slides(in a debris/mud flow or turbidity current physical state),characterized by high speed,pose a significant threat.Accurately assessing the impact forces exerted on pipelines by fluidized submarine slides is crucial for ensuring pipeline safety.This study aimed to provide a comprehensive overview of recent advancements in understanding pipeline impact forces caused by fluidized deep-sea slides,thereby identifying key factors and corresponding mechanisms that influence pipeline impact forces.These factors include the velocity,density,and shear behavior of deep-sea fluidized slides,as well as the geometry,stiffness,self-weight,and mechanical model of pipelines.Additionally,the interface contact conditions and spatial relations were examined within the context of deep-sea slides and their interactions with pipelines.Building upon a thorough review of these achievements,future directions were proposed for assessing and characterizing the key factors affecting slide impact loading on pipelines.A comprehensive understanding of these results is essential for the sustainable development of deep-sea pipeline projects associated with seabed resource development and the implementation of disaster prevention measures.
基金the National Natural Science Foundation of China(22078326,21878305,21908227)。
文摘In order to avoid the formation ofηphase(W_(6)Co_(6)C or W_(3)Co_(3)C)that adversely affects the sintering process and its products in the preparation process of ultra-fine WC-Co powder,a technical route of prereduction of WO_(3)-Co_(3)O_(4)to WO_(2)-Co and then deep reduction carbonization to WC-Co powder has been proposed.This study mainly investigates the influence of gas partial pressure on the pre-reduction process of WO_(3)-Co_(3)O_(4)under a mixed atmosphere of H_(2)-C_(2)H_(4)-Ar at 600℃and establishes the kinetic equations of pre-reduction and carbon evolution.The results indicate that increasing the partial pressure of hydrogen is conducive to the rapid and complete conversion of WO_(3) to WO_(2).High carbon content can be generated by the deposition of C_(2)H_(4),and it hinders the diffusion of the reducing gas;WO_(3)still cannot be completely reduced to WO_(2)as the partial pressure of C_(2)H_(4) increases to 60%.For the carbon evolution of C_(2)H_(4),the carbon amount is positively related to the H_(2)partial pressure,but it shows the highest amount and evolution rate when the ethylene partial pressure is 20%.Based on the reduction rate curves of WO_(3) and carbon evolution rate curves of C_(2)H_(4),the rate equations of pre-reduction and carbon evolution of WO_(3)-Co_(3)O_(4)system at 600℃are established.The pre-reduction reaction belongs to the first-order reaction,and its equation is expressed as follows:r=-(dw_(WO_(3)))/dt=(9±0.15)×10^(-2)×P_(H_(2))^(0.44)P_(C_(2)H_(4))&(0.57)The carbon deposition rate equation of C_(2)H_(4) can be expressed as follows:r=-(dc_C)/dt=r_f-r_b≌7.35×10^(-2)×P_(C_(2)H_(4))^(0.31)
基金funding from the Ministry of Science and Higher Education of the Russian Federation (Ural Federal University Program of Development within the Priority-2030 Program)is gratefully acknowledged.
文摘Using a newly developed experimental setup,the features and advantages of an autothermal single-casing atmospheric sub-bituminous coal fluidized bed air-blown gasifier,combining a combustion and gasification section,and mixing the dispersed phase(inert material,char)and heat exchange between them through an annular transfer device,have been revealed.To increase the efficiency of the gasifier,an experimental-computational method was developed find the conditions for optimal operation,combining changing the annular flow's geometry and regulating the primary air for gasification.A simple and reliable multizone thermodynamic calculation model makes it possible to predict the composition of char and syngas in the gasification section with acceptable accuracy.This method confirmed that a two-section fluidized bed gasifier can provide efficient gasification of solid fuels and is suitable for use in small-scale cogeneration plants.Syngas with a heating value of 3.6-4.5 MJ/m^(3)and CGE of 38.2%-42.3%was obtained in the experimental setup without optimizing the primary air flow rate.With optimization,the indicators increased to the heating value of syngas of 5.20-5.34 MJ/m^(3)and CGE of 42.5%-50.0%.With heat regeneration of 0.8,CGE increases to 70%.
基金financial supports from the Project of the National Natural Science Foundation of China(22178304,22108239)the Start-up Funding of Ningbo Research Institute of Zhejiang University(20201207Z0204).
文摘A set of hydrodynamic similarity laws is applied to the scale-up of ethylene polymerization fluidized bed reactors(FBRs)under the condensed mode operation.The thermal stability of open-loop controlled FBRs is investigated by the homotopy continuation method.And the Hopf bifurcation point is selected as an index of the thermal stability similarity.The simulation results show the similarity in state variables,operation parameters,the space-time yield(STY),and the thermal stability of FBRs with different scales.Furthermore,the thermal stability behaviors and similarity of the closed-loop controlled FBRs with different scales are analyzed.The observed similar trend of Hopf bifurcation curves reveals the similarity in the thermal stability of closed-loop controlled FBRs with different scaling ratios.In general,the results of the thermal stability similarity confirm that the hydrodynamics scaling laws proposed in the work are applicable to the scale-up of FBRs under the condensed mode operation.
基金the China-CEEC Joint Higher Education Project(Cultivation Project)(CEEC2021001)Srdjan Beloševic,Aleksandar Milicevic and Ivan Tomanovic acknowledge the financial support by the Ministry of Science,Technological Development and Innovation of the Republic of Serbia(Contract Annex:451-03-47/2023-01/200017).
文摘In this study,the open-source software MFIX-DEM simulations of a bubbling fluidized bed(BFB)are applied to assess nine drag models according to experimental and direct numerical simulation(DNS)results.The influence of superficial gas velocity on gas–solid flow is also examined.The results show that according to the distribution of time-averaged particle axial velocity in y direction,except for Wen–Yu and Tenneti–Garg–Subramaniam(TGS),other drag models are consistent with the experimental and DNS results.For the TGS drag model,the layer-by-layer movement of particles is observed,which indicates the particle velocity is not correctly predicted.The time domain and frequency domain analysis results of pressure drop of each drag model are similar.It is recommended to use the drag model derived from DNS or fine grid computational fluid dynamics–discrete element method(CFD-DEM)data first for CFD-DEM simulations.For the investigated BFB,the superficial gas velocity less than 0.9 m·s^(-1) should be adopted to obtain normal hydrodynamics.
基金supported by the open foundation of State Key Laboratory of Chemical Engineering (SKL–ChE–18B03)the Municipal Science and Technology Commission of Tianjin, China (2009ZCKFGX01900)。
文摘A liquid-solid circulating fluidized bed boiler is designed and built for visualization research by applying the fluidized bed heat transfer and fouling prevention technology to the water side of the boiler. Four types of engineering plastic particles with different physical properties are selected as the solid working media. The effect of particle types on the fluidization and distribution of particles in the boiler is investigated under different feedwater flow rates and amount of added particles by using the charge couple device image measurement and acquisition system. The results show that all kinds of particles can't be normally fluidized and accumulate in the drum at low amount of added particles and feedwater flow rate. The particles with great density and low sphericity are more likely to accumulate. The average solid holdup in the riser tubes increases with the increase in feedwater flow rate and the amount of added particles. The non-uniform degree of particle distribution in the riser tubes generally decreases with the increase in feedwater flow rate and the amount of added particles. The particles with small density and settling velocity have high average solid holdup in the riser tubes under close sphericity. In generally,the smaller the density and settling velocity, the more uniform the particle distribution in the riser tubes.Three-dimensional diagrams of the non-uniform degree of particle distribution in the riser tubes of the boiler are established.
基金supported by the National Natural Science Foundation of China(21908063)the Shanghai Pujiang Program(21PJ1402300)the Fundamental Research Funds of the Central Universities(JKB01211715 and JKB01221677)。
文摘The regeneration of fluidized catalytic cracking(FCC)catalysts is an essential process in petroleum processing.The current study focused the regeneration reaction characteristics of spent fluidized catalytic cracking catalyst(SFCC)at different atmospheres with influences on pore evolution and activity,for a potential way to reduce emission,produce moderate chemical product(CO),and maintain catalyst activity.The results show that regeneration in air indicates a satisfaction on removing coke on the catalyst surface while giving a poor effect on eliminating the coke inside micropores.This is attributed that the combustion in air led to a higher temperature and further transformed kaolinite phase to silicaaluminum spinel crystals,which tended to collapse and block small pores or expand large pores,with similar results observed in pure O_(2)atmosphere.Nevertheless,catalysts regenerated in O_(2)/CO_(2)diminished the combustion damage to the pore structure,of which the micro porosity after regeneration increased by 32.4% and the total acid volume rose to 27.1%.The regeneration in pure CO_(2)displayed low conversion rate due to the endothermic reaction and low reactivity.The coexistence of gasification and partial oxidation can promote regeneration and maintain the original structure and good reactivity.Finally,a mechanism of the regeneration reaction at different atmospheres was revealed.
基金supported by the National Natural Science Foundation of China(Grant No.52070165)the Major Science and Technology Project of Zhejiang Province,China(Grant No.2015C03015).
文摘Jets caused by burst tubes erode the surrounding soil, eventually leading to issues such as ground collapse. It is therefore highly important to study the mechanisms of soil erosion caused by jets after pipeline leakage. To investigate the water-soil interaction mechanisms of pipe leakage, this study used transparent soil and developed a three-dimensional experimental device to observe the fluidization process. Changes in the boundary of the fluidization transition area were investigated, and a formula for calculating the soil damage area was derived. The results showed three different shapes of the fluidized cavity appearing in the fluidization process. The particles initially moved upward and then gradually transitioned into a state of backflow. The effects of particle size, upper load, and porosity on fluidization were also analyzed. It was found that soil with a large particle size and a lower porosity under a heavy upper load can effectively restrain fluidization. Therefore, large-diameter and dense soil can be used as pipe-covering material.
基金the National Natural Science Foundation of China(Nos.51974287 and 21736010)Innovation Academy for Green Manufacture,Chinese Academy of Sciences(No.IAGM-2019-A11).
文摘Magnetization roasting is one of the most effective way of utilizing low-grade refractory iron ore.However,the reduction roasting of siderite(FeCO3)generates weakly magnetic wüstite,thus reducing iron recovery via weak magnetic separation.We systematically studied and proposed the fluidized preoxidation-low-temperature reduction magnetization roasting process for siderite.We found that the maghemite generated during the air oxidation roasting of siderite would be further reduced into wüstite at 500 and 550℃due to the unstable intermediate product magnetite(Fe_(3)O_(4)).Stable magnetite can be obtained through maghemite reduction only at low temperature.The optimal fluidized magnetization roasting parameters included preoxidation at 610℃for 2.5 min,followed by reduction at 450℃for 5 min.For roasted ore,weak magnetic separation yielded an iron ore concentrate grade of 62.0wt%and an iron recovery rate of 88.36%.Compared with that of conventional direct reduction magnetization roasting,the iron recovery rate of weak magnetic separation had greatly improved by 34.33%.The proposed fluidized preoxidation-low-temperature reduction magnetization roasting process can realize the efficient magnetization roasting utilization of low-grade refractory siderite-containing iron ore without wüstite generation and is unlimited by the proportion of siderite and hematite in iron ore.
基金the National Standardization Project of TCM(ZYBZH-C-TJ-55)and National Science and Technology Major Project(2018ZX09201011-002).
文摘The negative pressure conical fluidized bed is widely used in the pharmaceutical industry.In this study,experiments based on the negative pressure conical fluidized bed are carried out by changing the material mass and particle size.The pressure fluctuation signals are analyzed by the time and the frequency domain methods.A method for absolutely characterizing the degree of the energy concentration at the main frequency is proposed,where the calculation is to divide the original power spectrum by the average signal power.A phenomenon where the gas velocity curve temporarily stops growing is observed when the material mass is light,and the particle size is small.The standard deviation and kurtosis both rapidly change at the minimum fluidization velocity and thus can be used to determine the flow regime,and the variation rule of the kurtosis is independent of both the material mass and particle size.In the initial fluidization stage,the dominant pressure signal comes from the material movement;with the increase in the gas velocity,the power of a 2.5 Hz signal continues to increase.A method of dividing the main frequency by the average cycle frequency can conveniently determine the fluidized state,and a novel concept called stable fluidized zone proposed in this paper can be obtained.Controlling the gas velocity within the stable fluidized zone ensures that the fluidized bed consistently remains in a stable fluidized state.
基金The authors are grateful for the financial support of the National Key Research and Development Program of China(2018YFB0605403).
文摘An analysis approach considering gas-solids hydrodynamics,reaction kinetics and reacting species nonuniformity together in a dual-reactor system is presented for better understanding its mass and energy balance.It was achieved by a 3-dimensional comprehensive hydrodynamics and reaction model for the dual-reactor system,which was developed from the successfully verified 3-dimensional comprehensive combustion model for one circulating fluidized bed(CFB)system(Xu and Cheng,2019).The developed model and analysis approach was successfully used on a 1 MW circulating fluidized bed–bubbling fluidized bed(CFB-BFB)dual-reactor system.Results showed the sensible and chemical energy between two reactors as well as the energy distributions in each reactor were balanced and they agreed well with the experimental measurements.The analysis approach indicated energy balance had a close relationship with the mass transfer in the CFB-BFB dual-reactor system.It may be applied in a design and operation optimization for a dual-reactor system.
基金supported by the 12th Five-year National Technology Support Project(2011BAD13B04)
文摘To improve the efficiency of a CycloBio fluidized sand bed(CB FSB) in removal of dissolved wastes in recirculating aquaculture systems, the hydrodynamics of solid-liquid flow was investigated using computational fluid dynamics(CFD) modeling tools. The dynamic characteristics of silica sand within the CB FSB were determined using three-dimensional, unsteady-state simulations with the granular Eulerian multiphase approach and the RNG k-ε turbulence model, and the simulation results were validated using available lab-scale measurements. The bed expansion of CB FSB increased with the increase in water inflow rate in numerical simulations. Upon validation, the simulation involving 0.55 mm particles, the Gidaspow correlation for drag coefficient model and the Syamlal-O'Brien correlation for kinetic granular viscosity showed the closest match to the experimental results. The volume fraction of numerical simulations peaked as the wall was approached. The hydrodynamics of a pilot-scale CB FSB was simulated in order to predict the range of water flow to avoid the silica sand overflowing. The numerical simulations were in agreement with the experimental results qualitatively and quantitatively, and thus can be used to study the hydrodynamics of solid-liquid multiphase flow in CB FSB, which is of importance to the design, optimization, and amplification of CB FSBs.
基金Supported by Hydrocarbon High-efficiency Utilization Technology Research Center of Yanchang Petroleum(Group)Co.Ltd.,China(ycsy2013ky-A-30)
文摘An experimental study on co-pyrolysis of bituminous coal and biomass was performed in a pressured fluidized bed reactor.The blend ratio of biomass in the mixture was varied between 0 and 100 wt%,and the temperature was over a range of 550–650℃ under 1.0 MPa pressure with different atmospheres.On the basis of the individual pyrolysis behavior of bituminous coal and biomass,the influences of the biomass blending ratio,temperature,pressure and atmosphere on the product distribution were investigated.The results indicated that there existed a synergetic effect in the co-pyrolysis of bituminous coal and biomass in this pressured fluidized bed reactor,especially when the condition of bituminous coal and biomass blend ratio of 70:30(w/w),600℃,and 0.3 MPa was applied.The addition of biomass influenced the tar and char yields and gas and tar composition during co-pyrolysis.The tar yields were higher than the calculated values from individual pyrolysis of each fuel,and consequently the char yields were lower.The experimental results showed that the composition of the gaseous products was not in accordance with those of their individual fuel.The improvement of composition in tar also indicated synergistic effect in the co-pyrolysis.
基金Supported by The Grants from the National Scientific and Technological Major Project of China,No.2011ZX10004-901,No.2013ZX10004904the National Science and Technology Major Project,No.2012ZX10002006
文摘AIM:To construct and evaluate the functionality of a choanoid-fluidized bed bioreactor(CFBB)based on microencapsulated immortalized human hepatocytes.METHODS:Encapsulated hepatocytes were placed in the constructed CFBB and circulated through Dulbecco’s Modified Eagle’s Medium(DMEM)for 12 h,and then through exchanged plasma for 6 h,and compared with encapsulated cells cultivated under static conditions in a spinner flask.Levels of alanine aminotransferase(ALT)and albumin were used to evaluate the CFBB during media circulation,whereas levels of ALT,total bilirubin(TBil),and albumin were used to evaluate it during plasma circulation.Mass transfer and hepatocyte injury were evaluated by comparing the results from the two experimental conditions.In addition,the viability and microstructure of encapsulated cells were observed in the different environments.RESULTS:The bioartificial liver model based on a CFBB was verified by in vitro experiments.The viability of encapsulated cells accounting for 84.6%±3.7%in CFBB plasma perfusion was higher than the 74.8%±3.1%in the static culture group(P<0.05)after 6 h.ALT release from cells was 29±3.5 U/L vs 40.6±3.2U/L at 12 h(P<0.01)in the CFBB medium circulation and static medium culture groups,respectively.Albumin secretion from cells was 234.2±27.8μg/1×107cells vs 167.8±29.3μg/1×107 cells at 6 h(P<0.01),274.4±34.6μg/1×107 cells vs 208.4±49.3μg/1×107 cells(P<0.05)at 12 h,in the two medium circulation/culture groups,respectively.Furthermore,ALT and TBil levels were 172.3±24.1 U/L vs 236.3±21.5 U/L(P<0.05),240.1±23.9μmol/L vs 241.9±31.4μmol/L(P>0.05)at 6 h in the CFBB plasma perfusion and static plasma culture groups,respectively.There was no significant difference in albumin concentration between the two experimental plasma groups at any time point.The microstructure of the encapsulated hepatocytes remained healthier in the CFBB group compared with the static culture group after 6 h of plasma perfusion.CONCLUSION:The CFBB can function as a bioartificial liver based on a bioreactor.The efficacy of this novel bioreactor is promising for the study of liver failure.
基金The authors gratefully acknowledge the financial support provided by the State Key Research Development Program of China (Grant Number 2016YFC0600705)the National Natural Science Foundation of China (Grant Numbers 51674251, 51727807, and 51374213)+1 种基金the National Major Project for Science and Technology (Grant Number 2017ZX05049003-006)and the Innovation Teams of Ten-thousand Talents Program sponsored by the Ministry of Science and Technology of China (Grant Number 2016RA4067).
文摘Traditional coal mining and utilisation patterns are severely detrimental to natural resources and environments and significantly impede safe, low-carbon, clean, and sustainable utilisation of coal resources. Based on the idea of in situ fluidized coal mining that aims to transform solid coal into liquid or gas and transports the fluidized resources to the ground to ensure safe mining and low-carbon and clean utilisation, in this study, we report on a novel in situ unmanned automatic mining method. This includes a flexible, earthworm-like unmanned automatic mining machine (UAMM) and a coal mine layout for in situ fluidized coal mining suitable for the UAMM. The technological and economic advantages and the carbon emission reduction of the UAMM-based in situ fluidized mining in contrast to traditional mining technologies are evaluated as well. The development trends and possible challenges to this design are also discussed. It is estimated that the proposed method costs approximately 49% of traditional coal mining costs. The UAMM-based in situ fluidized mining and transformation method will reduce CO2 emissions by at least 94.9% compared to traditional coal mining and utilisation methods. The proposed approach is expected to achieve safe and environmentally friendly coal mining as well as lowcarbon and clean utilisation of coal.
基金Supported by the National Natural Science Foundation of China(51076154)National Key Technology Research&Development Program of 12 th Five-year of China(2011BAD15B05)
文摘Abstract:The aim of this research is to design and operate a 10 kW hot chemical-looping gasification(CLG)unit using Fe2O3/Al2O3as an oxygen carrier and saw dust as a fuel.The effect of the operation temperature on gas composition in the air reactor and the fuel reactor,and the carbon conversion of biomass to CO2and CO in the fuel reactor have been experimentally studied.A total60 h run has been obtained with the same batch of oxygen carrier of iron oxide supported with alumina.The results show that CO and H2concentrations are increased with increasing temperature in the fuel reactor.It is also found that with increasing fuel reactor temperature,both the amount of residual char in the fuel reactor and CO2concentration of the exit gas from the air reactor are degreased.Carbon conversion rate and gasification efficiency are increased by increasing temperature and H2production at 870℃reaches the highest rate.Scanning electron microscopy(SEM),X-ray diffraction(XRD)and BET-surface area tests have been used to characterize fresh and reacted oxygen carrier particles.The results display that the oxygen carrier activity is not declined and the specific surface area of the oxygen carrier particles is not decreased significantly.
基金financially supported by the National Nature Science Foundation of China (No.50974017)
文摘A fluidized bed jet milling process was used to make micro-fine high Nb-containing TiAl alloyed powders from the chippings obtained by crushing the Ti-45Al-8.5Nb-(W,B,Y) ingot.The influences of classifier frequency on powder characteristics were investigated.The results show that the powders with controlled average particle size can be prepared on a large scale.The powders with different sizes are all dominated by γ with aminor amount of α2-Ti3Al.The particle size significantly decreases with the classifier frequency increasing.At a classifier frequency higher than 38 Hz,the average particle size of the ground powders is lower than 25μm.The powders are composed of two differ-ent sizes of particles:shaped particles and some clastic particles,and both particle sizes meet the log-normal distribution.With the classifier frequency increasing,the both sizes decrease;meanwhile,the proportion of the clastic particles gradually increases,and the size distribution span value of the ground powders increases correspondingly.
文摘In this work,syngas methanation over Ni-W/TiO2-SiO2catalyst was studied in a fluidized-bed reactor(FBR)and its performance was compared with a fixed-bed reactor(FIXBR).The effects of main operating variables including feedstock gases space velocity,coke content,bed temperature and sulfur-tolerant stability of 100 h life were investigated.The structure of the catalysts was characterized by XRD,N2adsorptiondesorption and TEM.It is found that under same space velocity from 5000 h 1to 25000 h 1FBR gave a higher CH4yield,lower coke content,and lower bed temperature than those obtained in FIXBR.Ni-W/TiO2-SiO2catalyst possessed excellent sulfur-tolerant stability on the feedstock gases less than 500 ppm H2S in FBR.The carbon deposits formed on the spent catalyst were in the form of carbon fibers in FBR,while in the form of dense accumulation distribution appearance in FIXBR.
文摘A magnetically stabilized fluidized bed (MSB) is a highly efficient filter that takes the advantage of both fluidized beds and fixed beds. This paper presents the research to collect aerosol in airflow with a MSB. The filtering model of MSB is established with its parameters including magnetic field intensity, gas superficial velocity, average grain size, and bed height on the collection efficiency of MSB. The model is verified by experiments.
