The spout-fluidizing characteristics of high-carbon ferromanganese powders with different sizes and masses were studied via a plexiglass spout-fluidized bed with an inner diameter of 30 mm and a height of 1000 mm.The ...The spout-fluidizing characteristics of high-carbon ferromanganese powders with different sizes and masses were studied via a plexiglass spout-fluidized bed with an inner diameter of 30 mm and a height of 1000 mm.The relationships between bed voidage and such parameters as bed height,particle size,fluidizing air velocity,and air flow were obtained.Experimental results show that the powder material with high density can be fluidized in the spout-fluidized bed where the particle size is a key factor influencing the quality of fluidization.展开更多
Optimal design of gas intake in powder fuel supply systems is crucial for performance of aerospace engines.There is little research on the impact of intake structure on powder conveying performance.Three novel interna...Optimal design of gas intake in powder fuel supply systems is crucial for performance of aerospace engines.There is little research on the impact of intake structure on powder conveying performance.Three novel internal intakes were proposed,which are spherical,cube-shaped,and dome-shaped.After validation,CFD simulations demonstrate that fluctuation of mass flow rate of powders in the dome-shaped intake is reduced by about 73.3%compared with the annular external one.Variation trends of phase velocities are similar for the spherical and cube-shaped intakes,while those are similar for the annular external and dome-shaped internal intakes.Fluctuation of area of gas zone for the annular external and spherical internal intakes is larger than that for the cube-shaped and dome-shaped internal intakes.Pressure and relative pressure drop in the fluidization chamber have a stable stage,and fluctuation of relative pressure drop is small when dome-shaped internal intake is used.展开更多
Fluidization of fine cohesive powders is seriously restricted by the strong interparticle cohesion. The rational combination of nanoparticles with fine cohesive powders is expected to obtain composite par- ticles with...Fluidization of fine cohesive powders is seriously restricted by the strong interparticle cohesion. The rational combination of nanoparticles with fine cohesive powders is expected to obtain composite par- ticles with improved flowability. In this work, we firstly reviewed the sandwich and three-point contact models regarding the fundamental principles of nano-additives in reducing cohesiveness. Based on these previous models, the effects of the size of nanoparticles, their agglomeration and coverage on the surface of cohesive powders in reducing interparticle forces were theoretically analyzed. To validate the the- ory effectiveness for the irregularly shaped cohesive powders, an extreme case of cubic powders coated with silica nanoparticles was fabricated, and the flowability of the composite particles was determined experimentally. Ultimately, based oN force balance of a single particle, a semi-theoretical criterion for predicting the fluidization behavior of coated powders was developed to guide the practical applications of improving the flowability of cohesive powders through structural design and modulation.展开更多
This paper presents the results of an ongoing investigation into the fluctuations of pressure signals due to solids-gas flows for dense-phase pneumatic conveying of fine powders. Pressure signals were obtained from pr...This paper presents the results of an ongoing investigation into the fluctuations of pressure signals due to solids-gas flows for dense-phase pneumatic conveying of fine powders. Pressure signals were obtained from pressure transducers installed along different locations of a pipeline for the fluidized dense-phase pneumatic conveying of fly ash （median particle diameter 30μm; particle density 2300 kg/m^3; loose- poured bulk density 700 kg/m^3） and white powder （median particle diameter 55 p.m; particle density 1600 kg/m^3 ; loose-poured bulk density 620 kg/m^3） from dilute to fluidized dense-phase. Standard deviation and Shannon entropy were employed to investigate the pressure signal fluctuations. It was found that there is an increase in the values of Shannon entropy and standard deviation for both of the prod- ucts along the flow direction through the straight pipe sections. However, both the Shannon entropy and standard deviation values tend to decrease after the flow through bend（s）, This result could be attributed to the deceleration of particles while flowing through the bends, resulting in dampened particle fluctua- tion and turbulence. Lower values of Shannon entropy in the early parts of the pipeline could be due to the non-suspension nature of flow （dense-phase）, i.e., there is a higher probability that the particles are concentrated toward the bottom of pipe, compared with dilute-phase or suspension flow （high velocity）, where the particles could be expected to be distributed homogenously throughout the pipe bore （as the flow is in suspension）. Changes in straight-pipe pneumatic conveying characteristics along the flow direction also indicate a change in the flow regime along the flow.展开更多
The removal of volatile organic compounds by photocatalytic degradation is one of the safest and most effective ways of removing pollutants from the air. This process is highly affected by the type of reactor, light e...The removal of volatile organic compounds by photocatalytic degradation is one of the safest and most effective ways of removing pollutants from the air. This process is highly affected by the type of reactor, light exposure, and hydrodynamics. For scale up purposes, continuous reactors with high capacity are required for treating large amounts of feedstock. In this work, two types of reactors based on different hydrodynamics, fluidized and spouted reactors, were designed to work under light irradiation inside the reactor. The efficiency of the reactors for volatile organic compound removal from high flow rates of air under Hg lamp irradiation using N-F-TiO2 photocatalyst was investigated. The performance of the fluidized bed and spouted bed were evaluated and compared at the same weight hourly space velocity of feed stream through the reactor. The results revealed that 80% of the initial acetaldehyde was removed in the fluidized bed after about 200 min, while in the spouted bed the acetaldehyde was totally removed after about 120 min.展开更多
基金sponsored by National Natural Science Foundation of China and Baosteel Group Corporation (No.50974149)
文摘The spout-fluidizing characteristics of high-carbon ferromanganese powders with different sizes and masses were studied via a plexiglass spout-fluidized bed with an inner diameter of 30 mm and a height of 1000 mm.The relationships between bed voidage and such parameters as bed height,particle size,fluidizing air velocity,and air flow were obtained.Experimental results show that the powder material with high density can be fluidized in the spout-fluidized bed where the particle size is a key factor influencing the quality of fluidization.
基金the National Natural Science Foundation of China(grant No.12102161)the Aeronautical Science Foundation of China(grant No.20200001056001).
文摘Optimal design of gas intake in powder fuel supply systems is crucial for performance of aerospace engines.There is little research on the impact of intake structure on powder conveying performance.Three novel internal intakes were proposed,which are spherical,cube-shaped,and dome-shaped.After validation,CFD simulations demonstrate that fluctuation of mass flow rate of powders in the dome-shaped intake is reduced by about 73.3%compared with the annular external one.Variation trends of phase velocities are similar for the spherical and cube-shaped intakes,while those are similar for the annular external and dome-shaped internal intakes.Fluctuation of area of gas zone for the annular external and spherical internal intakes is larger than that for the cube-shaped and dome-shaped internal intakes.Pressure and relative pressure drop in the fluidization chamber have a stable stage,and fluctuation of relative pressure drop is small when dome-shaped internal intake is used.
基金The authors acknowledge the financial supports provided by the National Key Research and Development Program （No. 2016YFA0200101）, the National Natural Science Foundation of China （Nos. 21306102 and 21422604） and the China Postdoctoral Science Foundation （No. 2015M571049）.
文摘Fluidization of fine cohesive powders is seriously restricted by the strong interparticle cohesion. The rational combination of nanoparticles with fine cohesive powders is expected to obtain composite par- ticles with improved flowability. In this work, we firstly reviewed the sandwich and three-point contact models regarding the fundamental principles of nano-additives in reducing cohesiveness. Based on these previous models, the effects of the size of nanoparticles, their agglomeration and coverage on the surface of cohesive powders in reducing interparticle forces were theoretically analyzed. To validate the the- ory effectiveness for the irregularly shaped cohesive powders, an extreme case of cubic powders coated with silica nanoparticles was fabricated, and the flowability of the composite particles was determined experimentally. Ultimately, based oN force balance of a single particle, a semi-theoretical criterion for predicting the fluidization behavior of coated powders was developed to guide the practical applications of improving the flowability of cohesive powders through structural design and modulation.
文摘This paper presents the results of an ongoing investigation into the fluctuations of pressure signals due to solids-gas flows for dense-phase pneumatic conveying of fine powders. Pressure signals were obtained from pressure transducers installed along different locations of a pipeline for the fluidized dense-phase pneumatic conveying of fly ash （median particle diameter 30μm; particle density 2300 kg/m^3; loose- poured bulk density 700 kg/m^3） and white powder （median particle diameter 55 p.m; particle density 1600 kg/m^3 ; loose-poured bulk density 620 kg/m^3） from dilute to fluidized dense-phase. Standard deviation and Shannon entropy were employed to investigate the pressure signal fluctuations. It was found that there is an increase in the values of Shannon entropy and standard deviation for both of the prod- ucts along the flow direction through the straight pipe sections. However, both the Shannon entropy and standard deviation values tend to decrease after the flow through bend（s）, This result could be attributed to the deceleration of particles while flowing through the bends, resulting in dampened particle fluctua- tion and turbulence. Lower values of Shannon entropy in the early parts of the pipeline could be due to the non-suspension nature of flow （dense-phase）, i.e., there is a higher probability that the particles are concentrated toward the bottom of pipe, compared with dilute-phase or suspension flow （high velocity）, where the particles could be expected to be distributed homogenously throughout the pipe bore （as the flow is in suspension）. Changes in straight-pipe pneumatic conveying characteristics along the flow direction also indicate a change in the flow regime along the flow.
文摘The removal of volatile organic compounds by photocatalytic degradation is one of the safest and most effective ways of removing pollutants from the air. This process is highly affected by the type of reactor, light exposure, and hydrodynamics. For scale up purposes, continuous reactors with high capacity are required for treating large amounts of feedstock. In this work, two types of reactors based on different hydrodynamics, fluidized and spouted reactors, were designed to work under light irradiation inside the reactor. The efficiency of the reactors for volatile organic compound removal from high flow rates of air under Hg lamp irradiation using N-F-TiO2 photocatalyst was investigated. The performance of the fluidized bed and spouted bed were evaluated and compared at the same weight hourly space velocity of feed stream through the reactor. The results revealed that 80% of the initial acetaldehyde was removed in the fluidized bed after about 200 min, while in the spouted bed the acetaldehyde was totally removed after about 120 min.
