The effects of funnel-shape internals on hydrodynamics and mass transfer in an internal loop three-phase fluidized bed were investigated.Three different kinds of internals were designed which were setup on the top of ...The effects of funnel-shape internals on hydrodynamics and mass transfer in an internal loop three-phase fluidized bed were investigated.Three different kinds of internals were designed which were setup on the top of draft-tube in terms of horizontal angle and outer diameter, and gas hold up, liquid mixing time, liquid circulation velocity and mass transfer coefficient were measured respectively.It was shown that the riser gas holdup and mass transfer coefficient increased by 10% and 15% than that without such an internal, liquid mixing time decreased by 10% to 25%.When the superficial gas velocity was less than 0.5 cm·s-1, liquid circulation velocity increased with the setup of such internals·Liquid circulation velocity decreased when the superficial gas velocity was above 0.5 cm·s-1.In addition, the variation of structural parameters of funnel-shape internals had significant effects on hydrodynamics and mass transfer.展开更多
Flow behaviors of four kinds of granular particles(i.e. sphere,ellipsoid,hexahedron and binary mixture of sphere and hexahedron) in rectangular hoppers were experimentally studied. The effects of granular shape and ho...Flow behaviors of four kinds of granular particles(i.e. sphere,ellipsoid,hexahedron and binary mixture of sphere and hexahedron) in rectangular hoppers were experimentally studied. The effects of granular shape and hopper structure on flow pattern,discharge fraction,mean particle residence time and tracer concentration distribu-tion were tested based on the visual observation and particle tracer technique. The results show that particle shape affects significantly the flow pattern. The flow patterns of sphere,ellipsoid and binary mixture are all parabolic shape,and the flow pattern shows no significant difference with the change of wedge angle. The flowing zone be-comes more sharp-angled with the increasing outlet size. The flow pattern of hexahedron is featured with straight lines. The discharge rates are in increasing order from hexahedron,sphere,binary mixture to ellipsoid. The dis-charge rate also increases with the wedge angle and outlet size. The mean particle residence time becomes shorter when the outlet size increases. The difference of mean particle residence time between the maximum and minimum values decreases as the wedge angle increases. The residence time of hexahedron is the shortest. The tracer concen-tration distribution of hexahedron at any height is more uniform than that of binary mixture. The tracer concentra-tion of sphere in the middle is lower than that near the wall,and the contrary tendency is found for ellipsoid particles.展开更多
The incipient condition of hang-up for three Geldart-D powders has been experimentally studied in a 21 m long standpipe hopper system. Experimental results show that the pressure gradient for hang-up to occur is indep...The incipient condition of hang-up for three Geldart-D powders has been experimentally studied in a 21 m long standpipe hopper system. Experimental results show that the pressure gradient for hang-up to occur is independent of the materials height in the hopper and the diameter of orifice and equals to (dpw/dl)s, which can be predicted by Eq. (7). While the corresponding gas velocity in the standpipe equals to the incipient fluidized velocity of particles at the high pressure and can be predicted by Kwauk's equation.展开更多
文摘The effects of funnel-shape internals on hydrodynamics and mass transfer in an internal loop three-phase fluidized bed were investigated.Three different kinds of internals were designed which were setup on the top of draft-tube in terms of horizontal angle and outer diameter, and gas hold up, liquid mixing time, liquid circulation velocity and mass transfer coefficient were measured respectively.It was shown that the riser gas holdup and mass transfer coefficient increased by 10% and 15% than that without such an internal, liquid mixing time decreased by 10% to 25%.When the superficial gas velocity was less than 0.5 cm·s-1, liquid circulation velocity increased with the setup of such internals·Liquid circulation velocity decreased when the superficial gas velocity was above 0.5 cm·s-1.In addition, the variation of structural parameters of funnel-shape internals had significant effects on hydrodynamics and mass transfer.
基金Supported by the National Natural Science Foundation of China （50706007 50976025） the National Key Program of Basic Research in China （2010CB732206）+1 种基金 the Foundation of Excellent Young Scholar of Southeast University （4003001039） the Collaboration Project of China and British （2010DFA61960）
文摘Flow behaviors of four kinds of granular particles(i.e. sphere,ellipsoid,hexahedron and binary mixture of sphere and hexahedron) in rectangular hoppers were experimentally studied. The effects of granular shape and hopper structure on flow pattern,discharge fraction,mean particle residence time and tracer concentration distribu-tion were tested based on the visual observation and particle tracer technique. The results show that particle shape affects significantly the flow pattern. The flow patterns of sphere,ellipsoid and binary mixture are all parabolic shape,and the flow pattern shows no significant difference with the change of wedge angle. The flowing zone be-comes more sharp-angled with the increasing outlet size. The flow pattern of hexahedron is featured with straight lines. The discharge rates are in increasing order from hexahedron,sphere,binary mixture to ellipsoid. The dis-charge rate also increases with the wedge angle and outlet size. The mean particle residence time becomes shorter when the outlet size increases. The difference of mean particle residence time between the maximum and minimum values decreases as the wedge angle increases. The residence time of hexahedron is the shortest. The tracer concen-tration distribution of hexahedron at any height is more uniform than that of binary mixture. The tracer concentra-tion of sphere in the middle is lower than that near the wall,and the contrary tendency is found for ellipsoid particles.
文摘The incipient condition of hang-up for three Geldart-D powders has been experimentally studied in a 21 m long standpipe hopper system. Experimental results show that the pressure gradient for hang-up to occur is independent of the materials height in the hopper and the diameter of orifice and equals to (dpw/dl)s, which can be predicted by Eq. (7). While the corresponding gas velocity in the standpipe equals to the incipient fluidized velocity of particles at the high pressure and can be predicted by Kwauk's equation.
