The aerodynamics of particles and heat transfer of gas-to-particles in a two-dimensional spouted bed (2DSB) with draft plates are investigated by the discrete element method (DEM). The physical properties of the particles are similar to those of shelled corn. The calculated minimum spouting velocity and pressure drop agree well with the empirical correlations proposed by Kudra et al. The particle circulation rate increases when the friction coefficient decreases or the separation height increases. The draft plates can reduce the minimum spouting velocity and pressure drop. They also increase the maximum spoutable bed height. The effect of taking out the draft plates on the spouting phenomenon is investigated. The mixing of a 2DSB without draft plates of 10 000 particles is better than that of 26 000 particles. In our simulation, the gas-to-particle heat transfer is investigated. The Ranz-Marshall correlation and the correlation of Sartori et al. are applicable in the spout region and the downcomer region, respectively. The gas-to-particle heat transfer occurs mainly in the central or spout region, as reported by Freitas and Freire.

The aerodynamics of particles and gas flow in a two-dimensional spouted bed (2DSB) with draft plates is investigated with the aid of the discrete element method. The geometry of the 2DSB with draft plates is set as close as possible to the experimental apparatus of Kudra [1] and Kalwar [2]. The physical properties of the coarse particles are similar to those of shelled corn. The calculated minimum spouting velocity and pressure drop agree well with the correlations of Kudra [1] and Kalwar [2]. In the spout region, the particle vertical velocities are found to decrease as the height increases. The fluid velocity in the downcomer region decreases as the superficial gas velocity increases. The particle circulation rate increases when the friction coefficient decreases or the separation height increases. At the minimum spouting velocity, the bed height does not affect the particle circulation rate in the 2DSB with draft plates. ne draft plates not only reduce the minimum spouting velocity and pressure drop but also increase the maximum spoutable bed height. The effect of taking out the draft plates on the spouting phenomenon is investigated and the effect of putting in a deflector on the possible breakage of the particles is also estimated.

The solids motion in a gas–solid fluidized bed was investigated via discrete particle simulation. The motion of individual particles in a uniform particle system and a binary particle system was monitored by the solution of the Newton's second law of motion. The force acting on each particle consists of the contact force between particles and the force exerted by the surrounding fluid. The contact force is modeled by using the analogy of spring, dash-pot and friction slider. The flow field of gas was predicted by the Navier–Stokes equation. The solids distribution is non-uniform in the bed, which is very diluted near the center but high near the wall. It was also found that there is a single solids circulation cell in the fluidized bed with ascending at the center and descending near the wall. This finding agrees with the experimental results obtained by Moslemian. The effects of the operating conditions, such as superficial gas velocity, particle size, and column size on the solids movement, were investigated. In the fluidized bed containing uniform particles better solids mixing was found in the larger bed containing smaller size particles and operated at higher superficial gas velocity. In the system containing binary particles, it was shown that under suitable conditions the particles in a fluidized bed could be made mixable or non-mixable depending on the ratios of particle sizes and densities. Better mixing of binary particles was found in the system containing particles with less different densities and closer sizes. These results were found to follow the mixing and segregation criteria obtained experimentally by Tanaka et al.

The present paper describes a discrete particle simulation of pulsating fluidized beds. The effect of the gas pulsation on the flow pattern was studied numerically. Two cases of the bed were considered: one is of Group B particles in Geldart's classification and the other is of Group D particles. We also proposed a relaxation time of fluidized beds from the viewpoint of the bed response to the gas pulsation. The proposed relaxation time provided a good estimation to the present calculation results.

Flows in a spouted bed in a cylinder with a tapered bottom were simulated numerically. To reduce the computational load, a quasi-three-dimensional numerical simulation method for axisymmetric gas-solid flows was proposed. Fluid motion was calculated two-dimensionally by solving the locally averaged equations written in cylindrical coordinates, in which the circumferential components were neglected assuming the axisymmetry. Particle motion was calculated three-dimensionally and was traced discretely by solving Newton's equation of motion for each particle. The discrete element method (DEM) was employed to model the interaction between particles. The typical flow pattern of the spouted bed was obtained in the present calculation, i.e., a stable spout, fountain and annulus were obtained. The calculation was made for the same geometry as the experiment by Roy et al. [D. Roy, F. Larachi, R. Legros, J. Chaouki, Can. J. Chem. Eng. 72 (1994) 945–952]. The calculated spout diameter agreed quantitatively well with their experimental result. The calculated distributions of the vertical component of the particle velocity in the spout, the fountain and the annulus were compared with the experiments by He et al. [Y.-L. He, S.-Z. Qin, C.J. Lim, J.R. Grace, Can. J. Chem. Eng. 72 (1994) 561–568], in which smaller particles were used. The calculated velocity profiles agreed qualitatively well with the experimental results in spite of the difference in the particle diameter.

Dense gas-solid flows in a vertical pipe are important relating to many industrial applications; for example, standpipe flows in circulating fluidized beds or vertical plug flows in pneumatic conveying systems. In such flows, particles do not disperse uniformly in the pipes but form clusters, or generate density waves. Experimental and numerical studies have been performed for small-scale standpipe flows, and a power law have been found in power spectra of the density waves. In the present work, we analyzed the density wave in an industrial-scale vertical pipe, and found the similar power law in it although the value of the exponent was different from that of the previous works for small-scale systems. We also performed a numerical simulation based on the discrete element method (DEM) coupled with CFD. The calculated value of the exponent agreed quantitatively with that in the corresponding experiment. The effect of the gas velocity on flow structure was also investigated.

An Eulerian/Lagrangian-type numerical simulation was performed on a two-dimensional fluidized bed in which the particle motion is restricted by parallel front and rear walls. Particle motion was calculated using Newton's equation of motion, and the contact forces were modeled by the discrete element method. The locally averaged equations were solved to calculate the fluid motion, taking into account the interaction between fluid and particles. Two kinds of models were used regarding the calculation of the particle motion: a two-dimensional model and a three-dimensional model. Results for both cases were compared with each other and the effect of the walls on the particle motion is discussed. Cases where partition walls are set up artificially in the bed are also calculated.

A distinct element model is used to study the hydrodynamics of large-particle fluidized beds. The computed bubble rise velocity, voidage variations, averaged particle/particulate and fluid velocities are compared with the other continuum theory based on two fluid model. Based on the averaged particle/particulate velocities in a grid cell, deformation of the particle layers predicted by the two fluid model and the distinct element method are also compared. The predicted characteristics of bubble formation, motion, and eruption at the bed surface are in good qualitative agreement with the experimental observations. The quantitative differences in predicting the above parameters along with the advantages and limitations of two approaches for the case of a single isolated bubble rising in a two-dimensional fluidized bed are discussed.

Numerical simulation, in which the motion of individual particles was calculated, was performed of a two-dimensional gas-fluidized bed. Contact forces between particles are modeled by Cundall's Distinct Element Method (P.A. Cundall and O.D.L. Strack, Geotechnique, 29 (1979) 47), which expresses the forces with the use of a spring, dash-pot and friction slider. The gas was assumed to be inviscid and its flow was solved simultaneously with the motion of particles, taking into account the interaction between particles and gas. The simulation gives realistic pictures of particle motion. Formation of bubbles and slugs and the process of particle mixing were observed to occur in the same way as in experiments. The calculated pressure fluctuations compared well with measurements.

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Conversion of primary alcohols to the corresponding thiocyanates was effected by constant-current electrolysis of thiocyanate ion in dichloromethane containing an alcohol, triphenylphosphite, and 2, 6-lutidinium perchlorate or tetrafluoroborate. The electrolysis was performed at ambient temperature in a one-compartment cell using a graphite plate and a platinum plate as the anode and the cathode, respectively. 2, 6-Lutidinium cation effectively extracted thiocyanate ion into the organic phase from sodium thiocyanate suspended in the reaction mixture.