On the circulating boiling bed energy

Energy losses through gas filtration in a circulating boiling bed have been analyzed. The expression of the power needed for sustaining the internal circulation of particles has been obtained. On this basis the theoretical dependence for determining the carrying capacity of the flow and the lower boundary of existence of a circulating boiling bed (minimum transport velocity) has been established. Simple engineering formulas for calculating the bed drag and the maximum transport velocity have been obtained.     

Mixing of particles in apparatuses with a circulating fluidized bed

A phenomenological model of mixing of particles in a circulating fluidized bed has been formulated; a distinctive feature of the model is allowance for convective particle fluxes in the radial direction that ensure a substantial decrease observed in practice in the concentration of the particles over the risers height. As a result of a comparison of experimental and calculated mixing curves it has been established that the value of the coefficient of radial dispersion of the particles lies in the interval 0.0006–0.006 m²/sec.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 77, No. 6, pp. 148–158, November–December, 2004.     

Experimental study of boiling on heating surfaces during the thermal fluidization of a bed of particles

The results of an experimental investigation into the boiling of distilled water, aqueous solutions of NaCl, and sea-water brine on heating surfaces situated in a bed of mutuallydisconnected particles at atmospheric and reduced pressures are presented.     

Elimination of stagnant particles from a N-valve with side aeration in circulating fluidized bed

The existence of stagnant particle layer in the conventional non-mechanical valves limits their utilization in CFB with the feedstock of caking particles. A new N-valve consisted of a fluidized weir chamber with bottom aeration and a moving-bed angled standpipe with side aeration was developed to eliminate the stagnant particle layer and reach high solids circulation rate G_s in CFBs. The particle flow behavior and its control in the N-valve were studied experimentally. By combining the bottom aeration for weir chamber and the side aeration for angled standpipe the G_s over 270 kg/(m² s) was achieved, and the stagnant particle layer completely disappeared. The G_s increased with increasing the side aeration gas flow rate Q_sa, and this loosing gas flow was optimally injected from the bend between the downcomer and the angled standpipe. At a constant but enough high Q_sa, the increase in the bottom aeration gas flow rate Q_ba elevated G_s linearly.     

Heat exchange and hydrodynamics during boiling on a horizontal tube bundle in a fluidized bed of solid particles

The results are given on the experimental study of heat transfer and hydrodynamics with boiling on a horizontal tube bundle located in a dispersed bed of solid particles and of this process hydrodynamics simulation by gas bubbling within the fluid filtration rate variation via the bed (0–3.5)v_zi.f. An analysis and correlation of experimental results are presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 43, No. 5, pp. 718–727, November, 1982.     

Hydrodynamics of a circulating fluidized bed

Within the framework of similarity theory and using the Fr_t and J_s criteria, which are the generalized characteristics of a circulating fluidized bed, we obtain dimensionless dependences that describe the available experimental data on the wall mass fluxes of particles and the tangential stress on riser walls. The influence of the scale factor and other parameters of the system on the Fr_t and J_s quantities is revealed. A procedure to calculate mass fluxes of particles in the bed core is developed.     

Aerodynamics of a circulating fluidized bed

The authors present results of an experimental determination of the aerodynamic drag, density, velocity and dwell time of disperse material in a circulating bed.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 57, No. 5, November, 1989.     

Heat transfer in a circulating fluidized bed

On the basis of similarity theory a relationship is established for calculating the conductive-convective component of the coefficient of heat transfer in a circulating bed. Recommendations on the calculation of the total coefficient of heat transfer in a high-temperature bed are given. The gas gap between the heat-transfer surface and the first row of particles is evaluated. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 3, pp. 447–453, May–June, 1998.     

Evaluation of sorption-enhanced reforming over catalyst-sorbent bi-functional particles in an internally circulating fluidized bed

An internally circulating fluidized bed (ICFB) has been applied in various industrial processes owing to its potential in the reduction of heat loss and compact size. In this work, the sorption-enhanced reforming process in the ICFB is investigated. The dense discrete phase model (DDPM) is employed to evaluate the performance of catalyst-sorbent bi-functional particles, considering the particle size distribution. The results demonstrate that the utilization of bi-functional particles can significantly increase hydrogen production. The impacts of operating parameters including solid loading and regenerator velocity on solid circulation rate and gas leakage are examined. It is found that the gas leakage between reactors is increased by 46.6% when the regenerator gas velocity varies from 1.8 m/s to 2.4 m/s so as to weaken the hydrogen yield.     

Heat transfer for a liquid boiling in a bed of granular material

An approximate analytical model is given for heat transfer during boiling in a bed of granular material, and this is used in a generalization from the published data.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 34, No. 5, pp. 792–798, May, 1978.     

Structure of a fluidized bed with surface boiling of the fluidizing medium

It is shown that, compared to free conditions, in a fluidized bed the convective component plays a larger role in the heat-transfer mechanism during surface boiling.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 42, No. 2, pp. 239–243, February, 1982.     

Gas distribution in a packed bed

The authors give experimental and theoretical results obtained in studying the effects of the bed filtration rate, bed height, and the piece diameter on the distribution of gas streams in a close-packed bed.     

Evaluation of direct quadrature method of moment for the internally circulating fluidized bed simulation with ultrafine particles

In the framework of the Euler-Euler gas–solid two-fluid model, the particle population balance equation is solved by the direct quadrature method of moment. The dynamic process of ultrafine particle movement and aggregation in an internally circulating fluidized bed is simulated. The distribution of the concentration and velocity of the agglomerates in the flow process is given, and the changes of the moments in the bed are shown. The effects of different breakage coefficients and inlet gas rates on the concentration distribution of agglomerates are compared. The results show that the particle size decreases with the increase of breakage coefficient, and the time required to reach steady fluidization state increases; the higher the inlet velocity, the better the effect of circulating particles in the bed. When there is a certain gas velocity difference between the two sides, the effect of circulating particles in the bed is better.     

Multi-fluid modelling of hydrodynamics in a dual circulating fluidized bed

In this work, a multi-fluid model based on the Eulerian-Eulerian framework is used to study the gas-solid hydrodynamics, such as solid distribution, particle motion and solid velocity, in a three-dimensional (3D) dual circulating fluidized bed (DCFB). The influence of four different drag force models, including two classic models, i.e. Gidaspow, EMMS drag model and two recent drag models, i.e. Rong and Tang drag model, on hydrodynamics in DCFB are assessed. Numerical results show that the characteristics of solid distribution and velocity in different sections are distinct. For qualitative analysis, all the drag models can predict a reasonable radial solid distribution and pressure distribution, but only the EMMS, Rong and Tang drag model can capture the phenomenon of dense solid concentration in the low part. For quantitative analysis, the solid circulating rate predicted by the EMMS drag model is the closest to the experimental value while the Gidaspow drag model shows the most significant deviation. The overall assessments confirm that the drag model selection has a significant influence on the simulations of gas-solid flow in DCFBs. This study sheds lights on the design and optimization of fluidized bed apparatuses.     

Fluctuations of the number of solid-phase particles in a fluidized bed

An analytic expression is obtained for calculating the relative fluctuation of the number of particles in a fluidized bed. The fluctuation of the number of particles in a bed consisting of glass pellets fluidized with water has been experimentally investigated. The relative fluctuations obtained in these experiments are compared with the theoretical values for a fluidized bed and an ideal gas.     

Probability analysis of the motion of particles in a fluidized bed

The velocity and acceleration of particles moving in a fluidized bed are analyzed by means of histograms and random functions.     

Fine-scale mixing in a gas-fluidized bed of fine particles

The coefficients of diffusion of the particles and gas in the dense phase of a fluidized bed and the mean squares of the components of their pulsation velocity are analyzed with direct particle collisions neglected.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 38, No. 5, pp. 836–846, May, 1980.     

Moisture evaporation in a fluidized bed of inert particles

Results of an experimental study are compared with calculations based on the equations for thermal and material balance.     

Thermal relaxation time of particles in a fluidized bed

Results are given of an experimental investigation of the thermal relaxation time of particles in a fluidized bed. Values of the coefficient of heat transfer from particles to gas are determined.