Spouted Bed Research Articles

Attrition of lignite char in a spouted bed combustor

The generation of carbon fines by attrition during burning of Thai lignite char has been studied experimentally by means of a 92 mm i.d. continuous spouted bed combustor at different values of spouting gas velocity, bed temperature, and char feed size. Both inert particle size and static bed depth were fixed for all experimental runs. The collected data were used to analyse size distributions of both in-bed particles and elutriated fines, and to generate the suitable correlations for carbon attrition rate. Results obtained showed that attrition rate in the spouted bed is proportional to the excess of gas velocity above the minimum spouting gas velocity and the overall bed carbon surface exposed to attrition. The attrition rate constant is slightly dependent on operating bed temperature. Its values for the char studied were 1.6511 × 10−6 for 707°C operating bed temperature, and 1.1222 × 10−6 for 850°C, with the average for all tested runs being 1.224 × 10−6.

New reactor in jet spouted bed regime for catalytic polymerizations

The hydrodynamic features, suitable for catalytic polymerization in the gaseous phase, of a new reactor in the jet spouting regime have been studied. This regime is reached by expansion of conical spouted beds. The application of the jet spouted bed as a reactor in catalytic polymerizations implies the treatment of sticky solids with a wide particle size distribution, even of catalyst particles of reduced size (less than 1 mm diameter), which are not habitually treated in conventional spouted beds. The jet spouted bed has a high stability and reduced segregation together with a great capacity for continuous operation of the solids. In a pilot-plant scale unit, the following original aspects of the gas-solid contact have been studied: the design factors for stable operation (contactor angle, ratio between the inlet diameter and the base diameter of the contactor, ratio between the inlet diameter and the particle diameter); the hydrodynamics (correlations for the calculation of the minimum velocity, of the stable operation pressure drop and of the maximum pressure drop); the proposal of a disperse plug flow model for the gas in the reactor, and the subsequent calculation of the dispersion coefficient. The behaviour of the jet spouted bed as a reactor in the polymerization of benzyl alcohol has been studied in an automated laboratory unit where the effect of the residence time of the catalyst and the alcohol concentration in the feed have been analysed.

New reactor in jet spouted bed regime for catalytic polymerizations

The hydrodynamic features, suitable for catalytic polymerization in the gaseous phase, of a new reactor in the jet spouting regime have been studied. This regime is reached by expansion of conical spouted beds. The application of the jet spouted bed as a reactor in catalytic polymerizations implies the treatment of sticky solids with a wide particle size distribution, even of catalyst particles of reduced size (less than 1 mm diameter), which are not habitually treated in conventional spouted beds. The jet spouted bed has a high stability and reduced segregation together with a great capacity for continuous operation of the solids. In a pilot-plant scale unit, the following original aspects of the gas-solid contact have been studied: the design factors for stable operation (contactor angle, ratio between the inlet diameter and the base diameter of the contactor, ratio between the inlet diameter and the particle diameter); the hydrodynamics (correlations for the calculation of the minimum velocity, of the stable operation pressure drop and of the maximum pressure drop); the proposal of a disperse plug flow model for the gas in the reactor, and the subsequent calculation of the dispersion coefficient. The behaviour of the jet spouted bed as a reactor in the polymerization of benzyl alcohol has been studied in an automated laboratory unit where the effect of the residence time of the catalyst and the alcohol concentration in the feed have been analysed.

Prediction of the maximum spoutable bed height in two-dimensional spouted beds

The volumetric processing capacity, as well as the flexibility in operation, can be improved by using two-dimensional spouted beds (2DSBs) instead of conventional spouted beds (CSBs). These characteristics of the 2DSB geometry assure a great potential application of such beds to dry particulate solids. In this work, the mechanisms of spout termination in 2DSBs are analyzed and quantified through the use of meaningful dimensionless parameters. A new correlation for the maximum spoutable bed height in 2DSBs of coarse particles is proposed here. Criteria for scale-up of 2DSBs are also discussed on the basis of experimental data.

Performance of Single and Multi-stage Spouted Bed Drying Systems

ABSTRACT A mathematical model is developed to predict the performance of single-stage and multi-stage drying systems using spouted beds. The model uses unsteady state analysis for batch operation to simulate the steady state operation of a continuously fed spouted bed. A parametric study is carried out to study the effect of the following parameters on the performance of a single-stage grain drying system: air flow rate per unit mass of the grain in the bed, ambient air temperature and humidity, initial and target moisture contents, the residence time in the bed, and the effectiveness of the heat exchanger to recover the thermal energy in the exhaust air. The parametric study is also extended to investigate the effect of these parameters (except ambient air temperature and humidity) on the performance of the multi-stage system. In addition, the number of stages is also included in the latter study. The results are presented in terms of charts which may be adopted for the design of such systems.

Particle circulation and liquid bypassing in three phase draft tubed spouted beds

The design of any fluid-solid contacting system is based on a knowledge of certain intrinsic parameters and their functional dependence on extrinsic or easily measurable parameters such as system geometry, flow rates, etc. For Three Phase Draft-Tubed Spouted Bed systems(TPDS) , the important intrinsic design parameters are the particle circulation and the liquid distribution between the draft tube and the annulus. The extrinsic parameters are liquid and gas flow rates, solid loading, particle size, inlet size and draft tube size and spacing. In this paper a semi-empirical model is developed which relates the intrinsic design parameters to extrinsic variables at a constant draft tube size. The model is based on the earlier work of Grbavcic (1991a,b) who used a variational drag in transport systems and Matthew's (Ph.D thesis, RPI, Troy NY) work on pressure profiles in draft tubed spouted beds.

Mass Transfer between Fluid and Particles in a Liquid Spouted Bed.

Mass Transfer between Fluid and Particles in a Liquid Spouted Bed.

Particle velocity and circulation rate in liquid spouted beds

In this work, the particle velocity and circulation rate in water spouted beds of small glass particles are experimentally studied. The pathline, velocity and residence time of particles 0.53 to 1.40 mm in diameters were measured in the annulus of half-cylindrical columns 40, 60 and 90 mm in diameters. The particle velocity in the annulus and circulation rate increase practically linearly with fluid flowrate. As the column diameter was increased, the average particle velocity in the annulus was decreased, but the particle circulation rate was increased.

Mass transfer in liquid-fluidized and spouted beds of ion exchange resin at low Reynolds number

Rates of mass transfer from the liquid phase to small ion exchange resin particles (0.78 mm in mean diameter) in fluidized and spouted beds were studied experimentally. Dilute aqueous solution of sodium hydroxide was fed into the beds of strong cation exchange resin and the exit concentration of the solution was determined by conductivity measurement. In spouted beds, the initial conversion and Kl increased with bed height, but decreased with fluid flowrate. The model, applying material balance of the reactant and axisymmetric flow of fluid in the annulus of a spouted bed, predictions of the initial conversion in spouted beds are satisfactory. In fluidized beds, the obtained mass transfer coefficients were correlated and compared with other works.

The spouting regime map, bubbling characteristics and bed expansion of deep beds of large hollow polyethylene spheres

AbstractThe high velocity spouting regime of a deep bed containing 9.6 mm hollow polyethylene spheres of density 394 kg/m3 was investigated in a 152.4 mm flat bottom cylindrical half column with a 50.8 mm inlet. A bed height vs gas velocity regime diagram is presented showing the conditions under which type II spouting is observed. The transition velocity from bubbling to type II spouting is determined using the autocorrelation of the pressure fluctuations in the bed. The bubbling characteristics of the bed are described. Bed expansion in bubbling and type II spouted beds are reported.

Combustion and flow in a two dimensional spouted bed

A planar, two-dimensional spouted bed laboratory combustor has been studied to determine the interaction among the gas flow, particle flow, and combustion. The facility designed for a maximum thermal power of 5 kW, has a quartz front wall providing full optical access to particle flows and combustion processes. The combustor was characterized in terms of pressure, temperature, gas velocity, and particle velocity profiles and operating limits. Premixed propane and air and a fixed bed height, bed material, injector slot width, and combustor geometry were employed. As in previous investigations of axisymmetric spouted beds, the ratio of particle mass circulation rate to jet mass flow rate was observed to be about ten. Combustion increased this ratio by about ten percent. A pulsating mode of operation was noted with a characteristic frequency of about ten Hz, controlled by the interaction of the particle and gas flows. A simple model for the prediction of particle velocities in the spout agrees with experimental observation.

Hydrodynamic characteristics of jet‐spouted beds

AbstractJet‐spouted beds characterised by high velocity gas jets (above 1.7 Umsl), and shallow bed depths H0 of around 2 D1 were investigated on laboratory scale beds and industrial scale beds and the results obtained thereof are correlated and presented in this work. Compared with the classical spouted beds, important differences in bed structure, solid movements and basic hydrodynamic characteristics were observed. The minimum spouting velocity, bed voidage and pressure drop during stabilized spouting are described in terms of dimensionless equations. Bed expansion was used as the basis for the classification of different jet‐spouting regimes (incoherent spouting, fast spouting, pneumatic conveying) and changes in the slope of the bed expansion curve are correlated with regime changes. This classification could be useful in the optimization of industrial scale jet‐spouted beds. A typically applicable regime of fast spouting was identified.

Elutriation of Fines from a Continuous Spouted Bed in Solid-Gas System

連続式固-気系噴流層からの小粒子の飛び出し速度Vと塔高Hとの関係が, 大小2粒子系において実験的に研究された.その結果, 小粒子が飛び出す流速範囲で, 大小2粒子系噴流層を形成させるためには, 大粒子が飛び出さないある高さの塔高が必要であることが認められた.また, 噴流層のフリーボード部について考察し, この部分が3領域に区分できること.さらに, この各領域において, 飛び出し塔高係数αを各粒子系, 各実験条件について算出し, そのαが粒子供給速度の影響を受けず, 流速Uによって変化すること.また, α=αUはUによってあまり影響されず, 粒子径が大きくなるほど大きくなることが見いだされた.さらに, 塔の任意の高さでの粒子の飛び出し速度の推箪が, この αを用いることによって提案された.

A comparison of cylindrical and semi-cylindrical spouted beds of coarse particles

A comparison of cylindrical and semi-cylindrical spouted beds of coarse particles

Elutriation of Fines from a Small Spouted Bed in Solid-Gas System

Elutriation of Fines from a Small Spouted Bed in Solid-Gas System

Hydrodynamic model of the drying of a spouting bed

Hydrodynamic model of the drying of a spouting bed

Cracking of Residual Oil by Use of Dual Spouted Bed Reactor with Three Chambers (Part 2)

Cracking of Residual Oil by Use of Dual Spouted Bed Reactor with Three Chambers (Part 2)

Cracking of Residual Oil by Use of Dual Spouted Bed Reactor with Three Chambers (Part 1)

Cracking of Residual Oil by Use of Dual Spouted Bed Reactor with Three Chambers (Part 1)

噴流層による熱分解炭素の粒子への被覆

噴流層による熱分解炭素の粒子への被覆

On the Study of Behaviour of Solid Particles in the Stirred Spouted Bed

The model of diffusion has been dealt in the behaviour of solid particles for a gas-solid fluidized bed, the effects of operating conditions on the coefficient of solid diffusion have been investigated.In this paper, the stirred spouted bed was newly produced by way of trial for a granulating apparatus, the behaviour of solid particles in the bed was discussed from the residence time distribution obtained by the analysis of tracer particles.As a result, the mixing index and the apparent dead space in the bed were experimentally related to the operating variables, and these experimental equations were obtained,