Soot is a flocculent carbon nanoparticle that results the imperfect combustion of fossil fuel,and numerous studies are dedicated to the reduction of soot production to alleviate the associated environmental problems.H...Soot is a flocculent carbon nanoparticle that results the imperfect combustion of fossil fuel,and numerous studies are dedicated to the reduction of soot production to alleviate the associated environmental problems.However,soot as a functional material is also widely used in energy storage and superhydrophobic materials.As a partial oxidation technology,the entrained flow coal gasification process will produce part of the soot.It is important to separate soot from the coal gasification fine slag(CGFS)and understand its structural characteristics for soot utilization.For this purpose,two industrial typical pulverized coal gasification fine slag(PCGFS)and coal-water slurry gasification fine slag(WCGFS)were selected for this study.The results showed that both fine slags were rich in soot,and the dry ash free mass fraction of soot in PCGFS and WCGFS was 6.24%and 2.91%,respectively,and the soot of PCGFS had a hollow carbon nanosphere morphology,while the soot of WCGFS showed a flocculent irregular morphology.The average fringe length,fringe tortuosity,and fringe spacing of the soot were 0.84 nm,1.21,and 0.45 nm,respectively.Compared to the WCGFS,the soot particles of PCGFS have less continuity of molecular bonds within the lattice,the larger the defects within the lattice,the fewer isolated lattice carbon layers there are.This study provides important theoretical support for understanding the structural characteristics and next applications of soot in the entrained flow coal gasification fine slag.展开更多
Entrained flow adsorption using activated carbon as the adsorbent is widely adopted for PCDDs/Fs-abatement in municipal solid waste incineration (MSWI) process. The effects of operating parameters including flue gas t...Entrained flow adsorption using activated carbon as the adsorbent is widely adopted for PCDDs/Fs-abatement in municipal solid waste incineration (MSWI) process. The effects of operating parameters including flue gas temperature, feeding rate of activated carbon, polychlorinated dibenzodioxins and polychlorinated dibenzofurans (PCDDs/Fs) concentration at the inlet of the air pollution control device (APCD), filter materials, pressure drop on PCDDs/Fs removal efficiency are reviewed and commented upon in this paper. Evaluation on the various mechanistic models for entrained flow adsorption is carried out based on the computational simulation in terms of the actual operating condition and theoretical analysis. Finally, an advancement of en- trained flow adsorption in combination of dual bag filter is introduced.展开更多
The gasification kinetic modelling of two Victorian brown coal(Yallourn and Maddingley)chars and the validity for entrained flow gasification were investigated in this study.The study was conducted in a thermogravimet...The gasification kinetic modelling of two Victorian brown coal(Yallourn and Maddingley)chars and the validity for entrained flow gasification were investigated in this study.The study was conducted in a thermogravimetric analyzer(TGA)at 750–1100℃,30%–90%CO_(2)concentration using different char particle sizes within 20–106 mm.It was found that random pore model and modified volumetric model are applicable for TGA results,but volumetric model and grain model are not.The effect of particle size under106 mm on gasification rate is very limited.Activation energies of Maddingley char and Yallourn char in CO_(2)gasification are 219–220 and 197–208 k J/mol,respectively.The pre-exponential factors are in the same order of magnitude,and they increased as particle size decreased.A mathematical model was developed to predict carbon conversion over time for entrained flow gasification of Victorian brown coal chars at 1000–1400℃.展开更多
Four different pulverized coals have been used to study the effects of oxygen concentration on combustion characteristics under different enriched-oxygen conditions by entrained flow reactor experiments. The results s...Four different pulverized coals have been used to study the effects of oxygen concentration on combustion characteristics under different enriched-oxygen conditions by entrained flow reactor experiments. The results show that: with the increase of oxygen concentration, the ignition temperature of four coals greatly decreases and the low volatile coals decrease faster; with the increase of oxygen concentration, the ignition mode of pulverized coal has an obviously transformation from homogeneous ignition to heterogeneous ignition, and the corresponding oxygen concentrations are about 40% and 50%-60% respectively for bituminous coal and lignite, and both about 30% for lean coal and anthracite; with the increase of oxygen concentration, the optimal pulverized coal concentrations of bituminous coal and lignite increase firstly and then decrease, but for lean coal and anthracite, the optimal pulverized coal concentrations decrease slowly with the increase of oxygen concentration.展开更多
The process flow and the main devices of a new two-stage dry-fed coal gasification pilot plant with a throughout of 36 t/d are introduced in this paper. For comparison with the traditional one-stage gasifiers, the inf...The process flow and the main devices of a new two-stage dry-fed coal gasification pilot plant with a throughout of 36 t/d are introduced in this paper. For comparison with the traditional one-stage gasifiers, the influences of the coal feed ratio between two stages on the performance of the gasifier are detailedly studied by a series of experiments. The results reveal that the two-stage gasification decreases the temperature of the syngas at the outlet of the gasifier, simplifies the gasification process, and reduces the size of the syngas cooler. Moreover, the cold gas efficiency of the gasifier can be improved by using the two-stage gasification. In our experiments, the efficiency is about 3%-6% higher than the existing one-stage gasifiers.展开更多
Gasification technology is suggested to utilize asphalt particles, which are produced in the heavy oil deep separation process of using coupled low temperature separation of solvent and post extraction residue. In thi...Gasification technology is suggested to utilize asphalt particles, which are produced in the heavy oil deep separation process of using coupled low temperature separation of solvent and post extraction residue. In this work, the asphalt particles were first slurried with water and then gasified to produce synthesis gas. The gasification process of asphalt water slurry in an entrained flow gasifier was simulated using a three-dimensional computational fluid dynamics （CFD） model based on an Eulerian- Lagrangian method. The trajectories and residence time of asphalt particles, and the reaction rates, gas species distribution, temperature field and carbon conversion in the entrained flow gasifier were obtained. The predicted results indicated that the asphalt water slurry was a good feedstock for gasification. Moreover, the effects of particle size, oxygen equivalence ratio, and mass content of asphalt particles on the gasification performance of asphalt water slurry were investigated. These results are helpful for industrial application of asphalt water slurry gasification technology.展开更多
Early in 1953 the experiments by Peterka proved that air entrainment has effects on decreasing cavitation damage. This technology has been widely used in the release works of high dams since the inception of air entra...Early in 1953 the experiments by Peterka proved that air entrainment has effects on decreasing cavitation damage. This technology has been widely used in the release works of high dams since the inception of air entrainment in the Grand Goulee Dam in 1960. Behavior, mechanism and application of air entrainment for cavitation damage control have been investigated for over half century. However, severe cavitation damage happened due to complex mechanism of air entrainment. The effects of air entrainment are related to many factors, including geometric parameters, hydraulic parameters and entrained air manners. In the present work an experimental set-up for air entrainment was specially designed, the behavior of reducing cavitation damage was experimentally investigated in the three aspects of entrained air pressure, air tube aera and air tube number. The results show that magnitude of reduction of cavitation damage is closely related to the entrained air tube number as well as entrained air pressure, air tube aera, and that the effect through three air tubes is larger than that through single air tube although the entrained air tubes have the same sum of tube aera, that is, 1 ＋ 1 ＋ 1 〉 3. Therefore, it is important to design an effective manner of air entrainment.展开更多
The entrained flow gasification has been identified as the most promising gasification technology.Serious environmental pollution and waste of land resources are caused by the increasing amount of storage and producti...The entrained flow gasification has been identified as the most promising gasification technology.Serious environmental pollution and waste of land resources are caused by the increasing amount of storage and production of coal gasification slag.The aim of this work is to explore the feasibility of high-temperature combustion and melting technology for treating coal gasification fine slag and determine the important parameters of system operation.The flow properties and molten slag structure characteristics of three fine slags from different entrained flow gasifiers were studied.Depending on the melting mechanism of melt-dissolution,the melting time of fine slags is short.Three fine slags all produce glassy slags,which is conducive to slag discharge.The degree of polymerization of silicate melt is proportionate to the amount of SiO_(2)in the slag.A part of Al^(3+)exist in the form of[AlO_(4)]^(5-)because of the effect of CaO and Na_(2)O,as the network former.Finally,the degree of polymerization of the three type molten slag was calculated by considering the role of Si and Al in molten slag and the property of each one.展开更多
This paper presents entrainment mechanism, and transported and diffusioncharacteristics at the point of entry of submerged jet. The profiles of both velocity andconcentration within the air-water mixing layer were the...This paper presents entrainment mechanism, and transported and diffusioncharacteristics at the point of entry of submerged jet. The profiles of both velocity andconcentration within the air-water mixing layer were theoretically deduced. And the comparisonsbetween theoretical values and measured data were made. Results show that the velocity profilewithin the air-water mixing layer exhibits a form of error function. The concentrations of airentrainment in the internal and external regions of air-water mixing layer correspond to Gaussiandistribution.展开更多
The circadian system of mammals is composed of a hierarchical network of oscillators,including a core clock and peripheral clocks.The core clock receives an external photic signal and transmits it to the peripheral cl...The circadian system of mammals is composed of a hierarchical network of oscillators,including a core clock and peripheral clocks.The core clock receives an external photic signal and transmits it to the peripheral clocks,which,in turn,feed back to the core clock.Aging affects various functions of organisms including the circadian system.Entrainment displays the adaptability of the circadian system to changes in the external environment.However,there is currently no systematic study on the effects of aging on the entrainment capability.To explore the influencing mechanism,we develop a mathematical model of two populations of Goodwin oscillators,which represent the core clock and peripheral clocks.Based on numerical simulations,we conduct a detailed study on the impact of three aging-related factors on the entrainment capability represented by the entrainment range,entrainment time,and entrainment phase.The results indicate that the decrease in the sensitivity of suprachiasmatic nucleus(SCN)to light and the coupling strength from the SCN to the peripheral clocks due to aging increase the phase difference between the core and peripheral clocks,narrow the entrainment range,and prolong the entrainment time.A reduction in the coupling strength within the SCN has little effect on the three aspects mentioned above but increases the entrainment phase.Overall,aging reduces the circadian system's adaptability to the external environment,and the increased entrainment phase may lead to corresponding sleep problems.We also show that modulating the internal coupling strength in the peripheral clocks can mitigate aging effects;this provides an idea for using peripheral clocks to adjust the core clock,while also revealing new insights into the interaction between aging and the elasticity of the circadian system.This mechanism provides theoretical support for treating or alleviating circadian system disorders or sleep problems caused by aging.展开更多
An initialization-improved equilibrium constant method was used for modelling the copper matte smelting process with flash technology.Initial molar amounts of species were calculated by distributing the amounts of giv...An initialization-improved equilibrium constant method was used for modelling the copper matte smelting process with flash technology.Initial molar amounts of species were calculated by distributing the amounts of given elements.The species containing the largest amount of one element was chosen to be the corresponding thermodynamic component.The equilibrium values were derived via the Newton−Raphson method and converted to industrial forecast values using the mechanical entrainment equations.The results indicate that the calculated equilibrium value for copper concentration in the slag is 0.32 wt.%,while the industrial forecast value is 1.03 wt.%,with the industrial value being 1.13 wt.%.The present model required only 31 outer loops to derive the approximate solution close to the equilibrium value.The iterative path during the computation is considerably reduced and the risk of non-convergence during the computation is decreased.展开更多
In froth flotation,overall recovery of the floatable particles consists of true recovery and recovery by entrainment,where entrainment refers to the non-selective recovery of particles in the concentrate.To understand...In froth flotation,overall recovery of the floatable particles consists of true recovery and recovery by entrainment,where entrainment refers to the non-selective recovery of particles in the concentrate.To understand and optimize the flotation process with regard to process conditions,it is essential to distinguish true flotation recovery from overall recovery.The established methods rely on tailored flotation experiments,unrealistic flotation conditions,or using external tracers which can be different in density and crystal structure to the mineral(s) of interest.This study presents an approach to utilize naturally occuring suitable tracers to estimate the entrainment component from overall recovery of individual particles by establishing a relationship between their settling velocity coefficient and recovery probability.Recovery probabilities of individual particles are computed using particle-based separation modelling.The approach is demonstrated for a copper ore,where naturally occurring rutile was used as the tracer to determine the entrained component of the overall recovery of chalcopyrite particles.Laboratory flotation experiments revealed that entrainment accounted for up to 6% of the overall recovery probability of fully liberated chalcopyrite particles in the fine size fractions.This approach provides a practical method for entrainment correction enabling a more accurate evaluation of true flotation recovery.展开更多
Background: Brainwave entrainment using binaural beats has shown potential in treating tinnitus, but most studies have focused on one-month treatment durations. Objective: This study aimed to evaluate the time-bound e...Background: Brainwave entrainment using binaural beats has shown potential in treating tinnitus, but most studies have focused on one-month treatment durations. Objective: This study aimed to evaluate the time-bound efficacy of brainwave entrainment using binaural beats, comparing it to a standard tinnitus masker over a three-month duration. Method: Sixty-three individuals having tinnitus with normal hearing sensitivity were enrolled in the study. The participants were categorized into groups Ⅰ, Ⅱ, and Ⅲ. They were provided with delta(4 Hz) and alpha(10 Hz) frequency binaural beats and standard tinnitus masker, respectively, for a duration of three months. The tinnitus handicap inventory(THI) scores, Visual analogue scale(VAS) rating for tinnitus distress, and quality of life parameters were measured. The reductions obtained for each measure during the end of the first, second and third month were measured and compared across the groups. Results: All three groups showed considerable reductions in THI and VAS scores and improvements in the quality of life domains, focusing on physical and psychological health. However, groups Ⅰ and Ⅱ, who received binaural beats stimuli, showed higher benefits than those who received standard tinnitus masker. Conclusion: The results of the current study indicated that binaural beats can be an effective treatment technique for individuals with tinnitus having normal hearing sensitivity. Clinicians and otology/audiology practitioners shall adopt this innovative treatment after further validating these findings.展开更多
This study investigates the air–water interaction dynamics in jet streams,with particular emphasis on the transition from the cavity to the far-field regions.A dual-tip conductivity phase-detection probe was employed...This study investigates the air–water interaction dynamics in jet streams,with particular emphasis on the transition from the cavity to the far-field regions.A dual-tip conductivity phase-detection probe was employed to analyze four distinct downstream water levels.Based on the development of the cross-sectional mean air concentration,the jet flow was divided into four distinct regions:the jet length region,impact region,splash region,and far-field region.The results demonstrate varying trends in the evolution of the mean air concentration and maximum bubble frequency.Downstream water levels exerted a significant influence on these parameters in the splash and far-field regions,whereas minimal variation was observed in the impact region.Additionally,notable differences were identified in the probability density function of water droplets between the cavity and downstream regions.Furthermore,downstream water depth was found to have a negligible effect on the proportion of small-sized droplets in both the impact and splash regions.展开更多
The simultaneous unloading of double material heaps is a common occurrence in industrial workshops.This process causes dust escape to increase due to the interaction of entrained air between material heaps.In order to...The simultaneous unloading of double material heaps is a common occurrence in industrial workshops.This process causes dust escape to increase due to the interaction of entrained air between material heaps.In order to understand the coupling mechanism,a mathematical and physical model of the simultaneous unloading process of double material heaps is established in this paper.The DEM-CFD coupling method was validated using experimental data.The effects of material heap height,particle velocity and hopper outlet diameter on the entrained air characteristics of double material heap unloading process are analyzed.The“effective entrainment area”index was proposed for the first time to evaluate the coupling mechanism of entrained air between material heaps.The results indicate that:as the height of the material heap increases,the maximum velocity of the entrained air after collision of particles in different cross-sections gradually decreases from 1.4 to 1 m/s.With the increase in particle velocity and hopper outlet diameter,the maximum velocity of the entrained air generated between the material heaps increases.As the heap height,particle velocity,or hopper outlet diameter increases,the rate of change in entrained air velocity gradually decreases.The diameter of the hopper outlet has the greatest effect on the velocity of entrained air at the vertical axis between material heaps.The diameter of the hopper outlet has the most obvious effect on the height of the vortex core,with a maximum height difference of 33 mm.The effective entrainment area increases with heap height,particle velocity,or hopper outlet diameter,reaching a minimum of 568 mm^(2)at 2 m/s and a maximum of 1884 mm^(2)at 30 mm.展开更多
To study the hydrodynamic characteristics of gas-solid-phase flow in a pulse riser,a dense discrete particle model considering particle collisions and solid volume fraction is used.The core-annular flow in the enlarge...To study the hydrodynamic characteristics of gas-solid-phase flow in a pulse riser,a dense discrete particle model considering particle collisions and solid volume fraction is used.The core-annular flow in the enlarged-diameter section of the pulse riser is described,which can be destroyed with a high superficial gas velocity.The particle trajectory crossing effect and particle-particle and particle-wall collisions in the reduced-diameter section of the pulse riser can also destroy the core-annular flow and enhance the gas-solid interaction.The solid volume fraction exhibits an S-type distribution at different solid mass rates.The distribution of axial velocity,radial velocity,and relative slip velocity is investigated by analyzing the simulated results at different pulse riser diameter ratios.A suitable pulse riser diameter ratio can improve the performance of the pulse riser.展开更多
The Beijing Research lnstitute of Coal Chemistry (BRICC) is developing the SMOVEN process for hot gas desulfurization. The SMOVEN process features sulfidation in an entrained bed,regeneration in a low velocity fluid b...The Beijing Research lnstitute of Coal Chemistry (BRICC) is developing the SMOVEN process for hot gas desulfurization. The SMOVEN process features sulfidation in an entrained bed,regeneration in a low velocity fluid bed or a moving bed with oxygen and sorbent circuIation con-trolled by gas stream. A series of tests on the bench scale unit and the continuous process devel-opment unit were carried out. The regenerable metal oxide sorbents were adopted for the sulfur-related components removing from coal gas at the temperature of 550-650℃. A fluidized bed gasifier of 100 mm (id) generated coal gas for tests. The principle of SMOVEN process has been positively verified.展开更多
Given the gradual increase in the chlorite content of hematite ores, pulp properties seriously deteriorate during flotation. The traditional anion reverse flotation of hematite cannot effectively eliminate the effects...Given the gradual increase in the chlorite content of hematite ores, pulp properties seriously deteriorate during flotation. The traditional anion reverse flotation of hematite cannot effectively eliminate the effects of chlorite, leading to a significant decrease in the total Fe(TFe) grade of the concentrate. In this work, the effect of sodium alginate on the reverse flotation of hematite was systematically investigated. Flotation tests of artificially mixed ores were conducted, and the results showed that sodium alginate can significantly improve the removal rates of quartz and chlorite. The adsorption measurements, infrared spectroscopy, and contact angle tests demonstrated that sodium alginate adsorbs on the quartz surface by chelating with calcium ions, thereby weakening the steric hindrance of oleate ions and increasing the adsorption capacity of sodium oleate to ultimately improve the removal rate of quartz. Furthermore, owing to its lower density and fine particle size, chlorite is easily entrained into the foam layer. Sodium alginate dramatically increases the liquid-to-gas ratio of the foam layer by increasing pulp viscosity, thereby increasing the entrainment rate of chlorite and finally improving its removal rate. The core content of this thesis bears significance in improving the Fe grade in the reverse flotation of chlorite-containing hematite.展开更多
After the passage of a cold front, spring in northern China, the outbreak of strong wind is often accompanied by dust emissions. Through analyses of data in the atmospheric boundary layer during a typical case, it is ...After the passage of a cold front, spring in northern China, the outbreak of strong wind is often accompanied by dust emissions. Through analyses of data in the atmospheric boundary layer during a typical case, it is revealed there are rather regular gust wave packets superimposed on the basic strong wind flow. The gust-wind wave packets have a period equal to around 3 6 rains and possess coherent structure. As the vertical transport of momentum is decomposed into separate parts by （a） basic flow, （b） gust-wind, and （c） turbulence, they are all in a downwards direction at the lower levels of the atmospheric boundary layer during strong wind periods. However, （a） is the largest, while （b） and （c） are comparable. All these are very different from the case of normal weather. Besides, the friction velocity at the ground surface is also much larger than that of normal weather and should be corrected by taking the contributions of the basic flow and gust-wind into account.The strong basic flow with descending motion is very favorable for soil erosion and sand/dust emissions, but suppresses the entrainment of dust particles by keeping them within the bottom levels of the atmospheric boundary layer. Owing to the coherent structure of gust-wind, dust particles can effectively overcome the systematic descending air motion and penetrate into the middle and upper levels of the atmospheric boundary layer, and then propagate further and diffuse into the troposphere where ascending air motion prevails.展开更多
A massive rock and ice avalanche occurred on the western slope of the Ronti Gad valley in the northern part of Chamoli,Indian Himalaya,on 7 February 7,2021.The avalanche on the high mountain slope at an elevation of 5...A massive rock and ice avalanche occurred on the western slope of the Ronti Gad valley in the northern part of Chamoli,Indian Himalaya,on 7 February 7,2021.The avalanche on the high mountain slope at an elevation of 5600 m above sea level triggered a long runout disaster chain,including rock mass avalanche,debris avalanche,and flood.The disaster chain had a horizontal travel distance of larger than 17,600 m and an elevation difference of 4300 m.In this study,the disaster characteristics and dynamic process were analyzed by multitemporal satellite imagery.The results show that the massive rock and ice avalanche was caused by four large expanding discontinuity planes.The disaster chain was divided into five zones by satellite images and field observation,including source zone,transition zone,dynamic entrainment zone,flow deposition zone,and flood zone.The entrainment effect and melting water were recognized as the main causes of the long-runout distance.Based on the seismic wave records and field videos,the time progress of the disaster was analyzed and the velocity of frontal debris at different stages was calculated.The total analyzed disaster duration was 1247 s,and the frontal debris velocity colliding with the second hydropower station was approximately 23 m/s.This study also carried out the numerical simulation of the disaster by rapid mass movement simulation(RAMMS).The numerical results reproduced the dynamic process of the debris avalanche,and the mechanism of long-runout avalanche was further verified by parametric study.Furthermore,this study discussed the potential causes of disaster and flood and the roles of satellite images and seismic networks in the monitoring and early-warning.展开更多
基金supported by the National Natural Science Foundation of China(22168032,21968024)the National Key Research and Development Program of China(2023YFC3904302).
文摘Soot is a flocculent carbon nanoparticle that results the imperfect combustion of fossil fuel,and numerous studies are dedicated to the reduction of soot production to alleviate the associated environmental problems.However,soot as a functional material is also widely used in energy storage and superhydrophobic materials.As a partial oxidation technology,the entrained flow coal gasification process will produce part of the soot.It is important to separate soot from the coal gasification fine slag(CGFS)and understand its structural characteristics for soot utilization.For this purpose,two industrial typical pulverized coal gasification fine slag(PCGFS)and coal-water slurry gasification fine slag(WCGFS)were selected for this study.The results showed that both fine slags were rich in soot,and the dry ash free mass fraction of soot in PCGFS and WCGFS was 6.24%and 2.91%,respectively,and the soot of PCGFS had a hollow carbon nanosphere morphology,while the soot of WCGFS showed a flocculent irregular morphology.The average fringe length,fringe tortuosity,and fringe spacing of the soot were 0.84 nm,1.21,and 0.45 nm,respectively.Compared to the WCGFS,the soot particles of PCGFS have less continuity of molecular bonds within the lattice,the larger the defects within the lattice,the fewer isolated lattice carbon layers there are.This study provides important theoretical support for understanding the structural characteristics and next applications of soot in the entrained flow coal gasification fine slag.
基金Project supported by the National Basic Research Program (973) of China (No. G1999022211) and the National Natural Science Founda-tion of China (No. N59836210)
文摘Entrained flow adsorption using activated carbon as the adsorbent is widely adopted for PCDDs/Fs-abatement in municipal solid waste incineration (MSWI) process. The effects of operating parameters including flue gas temperature, feeding rate of activated carbon, polychlorinated dibenzodioxins and polychlorinated dibenzofurans (PCDDs/Fs) concentration at the inlet of the air pollution control device (APCD), filter materials, pressure drop on PCDDs/Fs removal efficiency are reviewed and commented upon in this paper. Evaluation on the various mechanistic models for entrained flow adsorption is carried out based on the computational simulation in terms of the actual operating condition and theoretical analysis. Finally, an advancement of en- trained flow adsorption in combination of dual bag filter is introduced.
文摘The gasification kinetic modelling of two Victorian brown coal(Yallourn and Maddingley)chars and the validity for entrained flow gasification were investigated in this study.The study was conducted in a thermogravimetric analyzer(TGA)at 750–1100℃,30%–90%CO_(2)concentration using different char particle sizes within 20–106 mm.It was found that random pore model and modified volumetric model are applicable for TGA results,but volumetric model and grain model are not.The effect of particle size under106 mm on gasification rate is very limited.Activation energies of Maddingley char and Yallourn char in CO_(2)gasification are 219–220 and 197–208 k J/mol,respectively.The pre-exponential factors are in the same order of magnitude,and they increased as particle size decreased.A mathematical model was developed to predict carbon conversion over time for entrained flow gasification of Victorian brown coal chars at 1000–1400℃.
文摘Four different pulverized coals have been used to study the effects of oxygen concentration on combustion characteristics under different enriched-oxygen conditions by entrained flow reactor experiments. The results show that: with the increase of oxygen concentration, the ignition temperature of four coals greatly decreases and the low volatile coals decrease faster; with the increase of oxygen concentration, the ignition mode of pulverized coal has an obviously transformation from homogeneous ignition to heterogeneous ignition, and the corresponding oxygen concentrations are about 40% and 50%-60% respectively for bituminous coal and lignite, and both about 30% for lean coal and anthracite; with the increase of oxygen concentration, the optimal pulverized coal concentrations of bituminous coal and lignite increase firstly and then decrease, but for lean coal and anthracite, the optimal pulverized coal concentrations decrease slowly with the increase of oxygen concentration.
基金This work was supported by the National High-Tech Research and Development Plan of China (No2003AA522030)
文摘The process flow and the main devices of a new two-stage dry-fed coal gasification pilot plant with a throughout of 36 t/d are introduced in this paper. For comparison with the traditional one-stage gasifiers, the influences of the coal feed ratio between two stages on the performance of the gasifier are detailedly studied by a series of experiments. The results reveal that the two-stage gasification decreases the temperature of the syngas at the outlet of the gasifier, simplifies the gasification process, and reduces the size of the syngas cooler. Moreover, the cold gas efficiency of the gasifier can be improved by using the two-stage gasification. In our experiments, the efficiency is about 3%-6% higher than the existing one-stage gasifiers.
基金support by the National Basic Research Program (Grant No. 2010CB226906)the Science Foundation of China University of Petroleum, Beijing (No. KYJJ2012-03-01)
文摘Gasification technology is suggested to utilize asphalt particles, which are produced in the heavy oil deep separation process of using coupled low temperature separation of solvent and post extraction residue. In this work, the asphalt particles were first slurried with water and then gasified to produce synthesis gas. The gasification process of asphalt water slurry in an entrained flow gasifier was simulated using a three-dimensional computational fluid dynamics （CFD） model based on an Eulerian- Lagrangian method. The trajectories and residence time of asphalt particles, and the reaction rates, gas species distribution, temperature field and carbon conversion in the entrained flow gasifier were obtained. The predicted results indicated that the asphalt water slurry was a good feedstock for gasification. Moreover, the effects of particle size, oxygen equivalence ratio, and mass content of asphalt particles on the gasification performance of asphalt water slurry were investigated. These results are helpful for industrial application of asphalt water slurry gasification technology.
基金supported by the National Natural Science Foundation of China (Grant No.50879021)the National Science Fund for Distinguished Young Scholars (Grant No.50925932)the Ministry of Science and Technology of China (Grant No.2008BAB19B04)
文摘Early in 1953 the experiments by Peterka proved that air entrainment has effects on decreasing cavitation damage. This technology has been widely used in the release works of high dams since the inception of air entrainment in the Grand Goulee Dam in 1960. Behavior, mechanism and application of air entrainment for cavitation damage control have been investigated for over half century. However, severe cavitation damage happened due to complex mechanism of air entrainment. The effects of air entrainment are related to many factors, including geometric parameters, hydraulic parameters and entrained air manners. In the present work an experimental set-up for air entrainment was specially designed, the behavior of reducing cavitation damage was experimentally investigated in the three aspects of entrained air pressure, air tube aera and air tube number. The results show that magnitude of reduction of cavitation damage is closely related to the entrained air tube number as well as entrained air pressure, air tube aera, and that the effect through three air tubes is larger than that through single air tube although the entrained air tubes have the same sum of tube aera, that is, 1 ＋ 1 ＋ 1 〉 3. Therefore, it is important to design an effective manner of air entrainment.
基金financially supported by Class A Strategic Pilot Science and Technology Project,Chinese Academy of Sciences(Grant No.XDA21040602)the National Natural Science Foundation of China(Grant No.U1810127)the Youth Innovation Promotion Association,Chinese Academy of Science(Grant No.Y201932)。
文摘The entrained flow gasification has been identified as the most promising gasification technology.Serious environmental pollution and waste of land resources are caused by the increasing amount of storage and production of coal gasification slag.The aim of this work is to explore the feasibility of high-temperature combustion and melting technology for treating coal gasification fine slag and determine the important parameters of system operation.The flow properties and molten slag structure characteristics of three fine slags from different entrained flow gasifiers were studied.Depending on the melting mechanism of melt-dissolution,the melting time of fine slags is short.Three fine slags all produce glassy slags,which is conducive to slag discharge.The degree of polymerization of silicate melt is proportionate to the amount of SiO_(2)in the slag.A part of Al^(3+)exist in the form of[AlO_(4)]^(5-)because of the effect of CaO and Na_(2)O,as the network former.Finally,the degree of polymerization of the three type molten slag was calculated by considering the role of Si and Al in molten slag and the property of each one.
文摘This paper presents entrainment mechanism, and transported and diffusioncharacteristics at the point of entry of submerged jet. The profiles of both velocity andconcentration within the air-water mixing layer were theoretically deduced. And the comparisonsbetween theoretical values and measured data were made. Results show that the velocity profilewithin the air-water mixing layer exhibits a form of error function. The concentrations of airentrainment in the internal and external regions of air-water mixing layer correspond to Gaussiandistribution.
基金Project supported by the graduate training funds of Shanghai Ocean University in China。
文摘The circadian system of mammals is composed of a hierarchical network of oscillators,including a core clock and peripheral clocks.The core clock receives an external photic signal and transmits it to the peripheral clocks,which,in turn,feed back to the core clock.Aging affects various functions of organisms including the circadian system.Entrainment displays the adaptability of the circadian system to changes in the external environment.However,there is currently no systematic study on the effects of aging on the entrainment capability.To explore the influencing mechanism,we develop a mathematical model of two populations of Goodwin oscillators,which represent the core clock and peripheral clocks.Based on numerical simulations,we conduct a detailed study on the impact of three aging-related factors on the entrainment capability represented by the entrainment range,entrainment time,and entrainment phase.The results indicate that the decrease in the sensitivity of suprachiasmatic nucleus(SCN)to light and the coupling strength from the SCN to the peripheral clocks due to aging increase the phase difference between the core and peripheral clocks,narrow the entrainment range,and prolong the entrainment time.A reduction in the coupling strength within the SCN has little effect on the three aspects mentioned above but increases the entrainment phase.Overall,aging reduces the circadian system's adaptability to the external environment,and the increased entrainment phase may lead to corresponding sleep problems.We also show that modulating the internal coupling strength in the peripheral clocks can mitigate aging effects;this provides an idea for using peripheral clocks to adjust the core clock,while also revealing new insights into the interaction between aging and the elasticity of the circadian system.This mechanism provides theoretical support for treating or alleviating circadian system disorders or sleep problems caused by aging.
基金supported by the National Natural Science Fund for Distinguished Young Scholars(No.51825403)Foundation for Innovative Research Groups of the National Natural Science Foundation of China(No.52121004)+2 种基金the Science and Technology Innovation Program of Hunan Province,China(No.2021RC3013)the National Key R&D Program of China(No.2022YFC3901602)the Major Science and Technology Project of Gansu Province,China(No.21ZD4GD033).
文摘An initialization-improved equilibrium constant method was used for modelling the copper matte smelting process with flash technology.Initial molar amounts of species were calculated by distributing the amounts of given elements.The species containing the largest amount of one element was chosen to be the corresponding thermodynamic component.The equilibrium values were derived via the Newton−Raphson method and converted to industrial forecast values using the mechanical entrainment equations.The results indicate that the calculated equilibrium value for copper concentration in the slag is 0.32 wt.%,while the industrial forecast value is 1.03 wt.%,with the industrial value being 1.13 wt.%.The present model required only 31 outer loops to derive the approximate solution close to the equilibrium value.The iterative path during the computation is considerably reduced and the risk of non-convergence during the computation is decreased.
基金funding from the European Union’s Horizon 2020 Marie Sklodowska-Curie Actions (MSCA), Innovative Training Networks (ITN), H2020-MSCA-ITN-2020 grant agreement(No.955805)。
文摘In froth flotation,overall recovery of the floatable particles consists of true recovery and recovery by entrainment,where entrainment refers to the non-selective recovery of particles in the concentrate.To understand and optimize the flotation process with regard to process conditions,it is essential to distinguish true flotation recovery from overall recovery.The established methods rely on tailored flotation experiments,unrealistic flotation conditions,or using external tracers which can be different in density and crystal structure to the mineral(s) of interest.This study presents an approach to utilize naturally occuring suitable tracers to estimate the entrainment component from overall recovery of individual particles by establishing a relationship between their settling velocity coefficient and recovery probability.Recovery probabilities of individual particles are computed using particle-based separation modelling.The approach is demonstrated for a copper ore,where naturally occurring rutile was used as the tracer to determine the entrained component of the overall recovery of chalcopyrite particles.Laboratory flotation experiments revealed that entrainment accounted for up to 6% of the overall recovery probability of fully liberated chalcopyrite particles in the fine size fractions.This approach provides a practical method for entrainment correction enabling a more accurate evaluation of true flotation recovery.
文摘Background: Brainwave entrainment using binaural beats has shown potential in treating tinnitus, but most studies have focused on one-month treatment durations. Objective: This study aimed to evaluate the time-bound efficacy of brainwave entrainment using binaural beats, comparing it to a standard tinnitus masker over a three-month duration. Method: Sixty-three individuals having tinnitus with normal hearing sensitivity were enrolled in the study. The participants were categorized into groups Ⅰ, Ⅱ, and Ⅲ. They were provided with delta(4 Hz) and alpha(10 Hz) frequency binaural beats and standard tinnitus masker, respectively, for a duration of three months. The tinnitus handicap inventory(THI) scores, Visual analogue scale(VAS) rating for tinnitus distress, and quality of life parameters were measured. The reductions obtained for each measure during the end of the first, second and third month were measured and compared across the groups. Results: All three groups showed considerable reductions in THI and VAS scores and improvements in the quality of life domains, focusing on physical and psychological health. However, groups Ⅰ and Ⅱ, who received binaural beats stimuli, showed higher benefits than those who received standard tinnitus masker. Conclusion: The results of the current study indicated that binaural beats can be an effective treatment technique for individuals with tinnitus having normal hearing sensitivity. Clinicians and otology/audiology practitioners shall adopt this innovative treatment after further validating these findings.
基金supported by the National Natural Science Foundation of China(52479068)Open Fund Research from the State Key Laboratory of Hydraulics and Mountain River Engineering(SKHL2323).
文摘This study investigates the air–water interaction dynamics in jet streams,with particular emphasis on the transition from the cavity to the far-field regions.A dual-tip conductivity phase-detection probe was employed to analyze four distinct downstream water levels.Based on the development of the cross-sectional mean air concentration,the jet flow was divided into four distinct regions:the jet length region,impact region,splash region,and far-field region.The results demonstrate varying trends in the evolution of the mean air concentration and maximum bubble frequency.Downstream water levels exerted a significant influence on these parameters in the splash and far-field regions,whereas minimal variation was observed in the impact region.Additionally,notable differences were identified in the probability density function of water droplets between the cavity and downstream regions.Furthermore,downstream water depth was found to have a negligible effect on the proportion of small-sized droplets in both the impact and splash regions.
基金supported by the National Natural Science Foundation of China(grant No.52108099)the Natural Science Foundation Youth Program of Hunan Province,China(grant No.2022JJ40443)the Basic Research Fund of Zhongye Changtian International Engineering Co.,Ltd.(grant No.2024JCYJ15).
文摘The simultaneous unloading of double material heaps is a common occurrence in industrial workshops.This process causes dust escape to increase due to the interaction of entrained air between material heaps.In order to understand the coupling mechanism,a mathematical and physical model of the simultaneous unloading process of double material heaps is established in this paper.The DEM-CFD coupling method was validated using experimental data.The effects of material heap height,particle velocity and hopper outlet diameter on the entrained air characteristics of double material heap unloading process are analyzed.The“effective entrainment area”index was proposed for the first time to evaluate the coupling mechanism of entrained air between material heaps.The results indicate that:as the height of the material heap increases,the maximum velocity of the entrained air after collision of particles in different cross-sections gradually decreases from 1.4 to 1 m/s.With the increase in particle velocity and hopper outlet diameter,the maximum velocity of the entrained air generated between the material heaps increases.As the heap height,particle velocity,or hopper outlet diameter increases,the rate of change in entrained air velocity gradually decreases.The diameter of the hopper outlet has the greatest effect on the velocity of entrained air at the vertical axis between material heaps.The diameter of the hopper outlet has the most obvious effect on the height of the vortex core,with a maximum height difference of 33 mm.The effective entrainment area increases with heap height,particle velocity,or hopper outlet diameter,reaching a minimum of 568 mm^(2)at 2 m/s and a maximum of 1884 mm^(2)at 30 mm.
基金This study was supported by the National Natural Science Foundation of China(No.21878335,21576293,and 21576294)the Major Scientific and Technological Innovation Projects in Shandong Province of China(No.2018CXGC0301)+1 种基金the Fundamental Research Funds for the Central Universities(18CX02121A)The authors gratefully acknowledge the financial support from the State Key Laboratory of Heavy Oil Processing and the Shandong Natural Science Foundation(ZR2017QEE006).
文摘To study the hydrodynamic characteristics of gas-solid-phase flow in a pulse riser,a dense discrete particle model considering particle collisions and solid volume fraction is used.The core-annular flow in the enlarged-diameter section of the pulse riser is described,which can be destroyed with a high superficial gas velocity.The particle trajectory crossing effect and particle-particle and particle-wall collisions in the reduced-diameter section of the pulse riser can also destroy the core-annular flow and enhance the gas-solid interaction.The solid volume fraction exhibits an S-type distribution at different solid mass rates.The distribution of axial velocity,radial velocity,and relative slip velocity is investigated by analyzing the simulated results at different pulse riser diameter ratios.A suitable pulse riser diameter ratio can improve the performance of the pulse riser.
文摘The Beijing Research lnstitute of Coal Chemistry (BRICC) is developing the SMOVEN process for hot gas desulfurization. The SMOVEN process features sulfidation in an entrained bed,regeneration in a low velocity fluid bed or a moving bed with oxygen and sorbent circuIation con-trolled by gas stream. A series of tests on the bench scale unit and the continuous process devel-opment unit were carried out. The regenerable metal oxide sorbents were adopted for the sulfur-related components removing from coal gas at the temperature of 550-650℃. A fluidized bed gasifier of 100 mm (id) generated coal gas for tests. The principle of SMOVEN process has been positively verified.
基金financially supported by the National Natural Science Foundation of China(Nos.51504053 and 51374079)the Fundamental Research Funds for the Central Universities(No.N170107013)
文摘Given the gradual increase in the chlorite content of hematite ores, pulp properties seriously deteriorate during flotation. The traditional anion reverse flotation of hematite cannot effectively eliminate the effects of chlorite, leading to a significant decrease in the total Fe(TFe) grade of the concentrate. In this work, the effect of sodium alginate on the reverse flotation of hematite was systematically investigated. Flotation tests of artificially mixed ores were conducted, and the results showed that sodium alginate can significantly improve the removal rates of quartz and chlorite. The adsorption measurements, infrared spectroscopy, and contact angle tests demonstrated that sodium alginate adsorbs on the quartz surface by chelating with calcium ions, thereby weakening the steric hindrance of oleate ions and increasing the adsorption capacity of sodium oleate to ultimately improve the removal rate of quartz. Furthermore, owing to its lower density and fine particle size, chlorite is easily entrained into the foam layer. Sodium alginate dramatically increases the liquid-to-gas ratio of the foam layer by increasing pulp viscosity, thereby increasing the entrainment rate of chlorite and finally improving its removal rate. The core content of this thesis bears significance in improving the Fe grade in the reverse flotation of chlorite-containing hematite.
基金funded by the National Natural Science Foundation of China under Grant Nos.40830103, 40775018, 40875008 and 40605006the science plan in the Chinese Academy of Sciences (KZCX2-YW210)+2 种基金Chinese Academy of Sciences under Grant No.YZ200708through special finance from the China Meteorological Administration(GYHY200706034)the Urban Meteorological Research Foundation (UMRF200810)
文摘After the passage of a cold front, spring in northern China, the outbreak of strong wind is often accompanied by dust emissions. Through analyses of data in the atmospheric boundary layer during a typical case, it is revealed there are rather regular gust wave packets superimposed on the basic strong wind flow. The gust-wind wave packets have a period equal to around 3 6 rains and possess coherent structure. As the vertical transport of momentum is decomposed into separate parts by （a） basic flow, （b） gust-wind, and （c） turbulence, they are all in a downwards direction at the lower levels of the atmospheric boundary layer during strong wind periods. However, （a） is the largest, while （b） and （c） are comparable. All these are very different from the case of normal weather. Besides, the friction velocity at the ground surface is also much larger than that of normal weather and should be corrected by taking the contributions of the basic flow and gust-wind into account.The strong basic flow with descending motion is very favorable for soil erosion and sand/dust emissions, but suppresses the entrainment of dust particles by keeping them within the bottom levels of the atmospheric boundary layer. Owing to the coherent structure of gust-wind, dust particles can effectively overcome the systematic descending air motion and penetrate into the middle and upper levels of the atmospheric boundary layer, and then propagate further and diffuse into the troposphere where ascending air motion prevails.
文摘A massive rock and ice avalanche occurred on the western slope of the Ronti Gad valley in the northern part of Chamoli,Indian Himalaya,on 7 February 7,2021.The avalanche on the high mountain slope at an elevation of 5600 m above sea level triggered a long runout disaster chain,including rock mass avalanche,debris avalanche,and flood.The disaster chain had a horizontal travel distance of larger than 17,600 m and an elevation difference of 4300 m.In this study,the disaster characteristics and dynamic process were analyzed by multitemporal satellite imagery.The results show that the massive rock and ice avalanche was caused by four large expanding discontinuity planes.The disaster chain was divided into five zones by satellite images and field observation,including source zone,transition zone,dynamic entrainment zone,flow deposition zone,and flood zone.The entrainment effect and melting water were recognized as the main causes of the long-runout distance.Based on the seismic wave records and field videos,the time progress of the disaster was analyzed and the velocity of frontal debris at different stages was calculated.The total analyzed disaster duration was 1247 s,and the frontal debris velocity colliding with the second hydropower station was approximately 23 m/s.This study also carried out the numerical simulation of the disaster by rapid mass movement simulation(RAMMS).The numerical results reproduced the dynamic process of the debris avalanche,and the mechanism of long-runout avalanche was further verified by parametric study.Furthermore,this study discussed the potential causes of disaster and flood and the roles of satellite images and seismic networks in the monitoring and early-warning.
