A new first degree solids mixing rate is proposed to evaluate the mixing of solids in small scale Iluidized beds. Particle mixing experiments were carried out in a 2D fluidized bed with a cross-section of 0.02 m ×...A new first degree solids mixing rate is proposed to evaluate the mixing of solids in small scale Iluidized beds. Particle mixing experiments were carried out in a 2D fluidized bed with a cross-section of 0.02 m × 0.2 m and a height of Im. white and black particles with average diameters of 850 and 450 μm were used in our experiments. Image processing was used to measure the concentration of the tracers at different times. The effects of four representative operating parameters （superficial gas velocity, ratio of tracer particles to bed particles, tracer particle position, and particle size） on mixing are discussed with reference to the mixing index. We found that the Lacey index depends on the concentration of the tracers, The position of the tracers affects the initial mixing rate but not the final degree of mixing. However, the new mixing rate equation does not depend on the initial configuration of the particles because this situation is considered to be the initial condition. Using the data obtained in this work and that found in literature, an empirical correlation is proposed to evaluate the mixing rate constant as a function of dimensionless numbers （Archimedes, Reynolds, and Froude） in small scale fluidized beds. This correlation allows for an estimation of the mixing rate under different operating conditions and for the detection of the end point and/or the time of mixing.展开更多
The flow dynamics in a novel fast-turbulent fluidized bed （FTFB） with middle-upper expanding structure and two different ring-feeder internals （mixed and vortex ring-feeder） were studied to achieve a reduction in ...The flow dynamics in a novel fast-turbulent fluidized bed （FTFB） with middle-upper expanding structure and two different ring-feeder internals （mixed and vortex ring-feeder） were studied to achieve a reduction in gasoline olefin production, Compared with a conventional circulating fluidized bed, the novel FTFB displayed unique characteristics and advantages. A higher solids holdup and more uniform solids holdup distribution existed in the diameter-expanding region, especially for the FTFB with vortex ring-feeder structure, A probability density distribution analysis indicated that the novel fluidized bed could reduce gas-solids segregation and enhance gas-solids interaction. A constant carbon dioxide tracer system was used to simulate the reactant gas distribution. The gas-solids contact efficiency was defined according to the solid dispersibility and the amount of gas covering the solid surface. Novel FTFB risers, especially those with vortex ring-feeders, have a much higher gas-solids contact efficiency than that of traditional risers.展开更多
文摘A new first degree solids mixing rate is proposed to evaluate the mixing of solids in small scale Iluidized beds. Particle mixing experiments were carried out in a 2D fluidized bed with a cross-section of 0.02 m × 0.2 m and a height of Im. white and black particles with average diameters of 850 and 450 μm were used in our experiments. Image processing was used to measure the concentration of the tracers at different times. The effects of four representative operating parameters （superficial gas velocity, ratio of tracer particles to bed particles, tracer particle position, and particle size） on mixing are discussed with reference to the mixing index. We found that the Lacey index depends on the concentration of the tracers, The position of the tracers affects the initial mixing rate but not the final degree of mixing. However, the new mixing rate equation does not depend on the initial configuration of the particles because this situation is considered to be the initial condition. Using the data obtained in this work and that found in literature, an empirical correlation is proposed to evaluate the mixing rate constant as a function of dimensionless numbers （Archimedes, Reynolds, and Froude） in small scale fluidized beds. This correlation allows for an estimation of the mixing rate under different operating conditions and for the detection of the end point and/or the time of mixing.
基金the financial support of the CNPC in the National Program on Key Basic Research Project(973 Program) of China(No.2012CB215000)
文摘The flow dynamics in a novel fast-turbulent fluidized bed （FTFB） with middle-upper expanding structure and two different ring-feeder internals （mixed and vortex ring-feeder） were studied to achieve a reduction in gasoline olefin production, Compared with a conventional circulating fluidized bed, the novel FTFB displayed unique characteristics and advantages. A higher solids holdup and more uniform solids holdup distribution existed in the diameter-expanding region, especially for the FTFB with vortex ring-feeder structure, A probability density distribution analysis indicated that the novel fluidized bed could reduce gas-solids segregation and enhance gas-solids interaction. A constant carbon dioxide tracer system was used to simulate the reactant gas distribution. The gas-solids contact efficiency was defined according to the solid dispersibility and the amount of gas covering the solid surface. Novel FTFB risers, especially those with vortex ring-feeders, have a much higher gas-solids contact efficiency than that of traditional risers.
