Capture of monodispersed aerosol particles in a fixed and in a fluidized bed

Knettig, P.; Beeckmans, J. M.

doi:10.1002/cjce.5450520602

Cited by 38 publications

(24 citation statements)

References 4 publications

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“…8 or 9a. Experiments do show (Knetting and Beeckmans, 1974;Doganoglu et al, 1978;D'Ottavio and Goren, 1983) that for large values of L /%I there exists an exponential dependence between L / 2 a and the efficiency v. The effect of the other parameters on q is not quantitatively clear or agreed upon. In spite of the limitations of the sphere-in-cell models and the single sphere efficiency approach they are widely used in the literature…”

Section: Total Filter Bed Efficiencymentioning

confidence: 87%

A study of inertial effects in granular bed filtration

1985

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The filtration efficiency of a granular bed filter was investigated in the domain where inertial effects are dominant. A filtration model predicting single sphere and total bed efficiencies based on trajectory calculations of dust particles in the voids of the granular bed was developed. The model uses the flow field in a bed of spheres arranged in a body-centered cubic array for which the filtration efficiency was found to be a function of a modified Stokes number defined by Sf' = St X F where the function Fdepends only on the Reynolds number. The value of the function F can be found experimentally or predicted from the Ergun correlation to be F = 1 + 0.0157 Re, The filtration efficiency calculated using the model agrees well with experimental results obtained in beds of dense cubic packing of spheres especially at relatively low Reynolds numbers (Re < 2W) and relatively high Stokes numbers (St' > 0.01). The prediction of the theoretical model also agrees well with experimental data for randomly packed beds at low porosities and low Reynolds numbes. Most theoretical models of filtration in granular beds are based on evaluating the filtration efficiency of a single granule and then integrating the results over the entire bed by assuming that all granules in the bed experience similar filtration conditions and have the same filtration efficiency. The single sphere efficiency is usually determined by calculating the trajectories of aerosol particles flowing toward a single sphere and modifying the gas flow field to account for the porosity of the bed. The major difficulty in using this approach is that the particle trajectories and therefore the filtration efficiency depends strongly on the actual threedimensional flow profile of the gas flowing through the bed. A representative and accurate threedimensional velocity profile for flow in a granular bed is not yet availabe in the literature so that simplified flow models must be used for trajectory calculations with results that do not agree well with experimental data.In the present work an improved version of the Snyder and Stewart (1966) flow model for a dense cubic packing of spheres is used to evaluate the filtration efficiency in a granular bed. The threedimensional flow model enables trajectory calculations to be made for a single sphere as well as for the entire bed. The calculated single sphere and total bed efficiencies are compared to determine the validity of the single sphere efficiency concept. The results for the single sphere and total bed efficiencies are also compared with experimental data obtained in both dense cubic packing of spheres and in randomly packed beds. CONCLUSIONS AND SIGNIFICANCEA filtration model predicting both single sphere and total bed efficiency was developed for a dense cubic packing using the flow field developed by Snyder and Stewart (1966). The model is based on trajectory calculations of dust particles inside the granular bed and assumes no bouncing of dust particles from the surface of the granules. The filtration efficien...

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Section: Total Filter Bed Efficiencymentioning

confidence: 87%

A study of inertial effects in granular bed filtration

1985

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“…In 1970 and 1980s, the studies of particle filtration by fluidized beds were proceeded because the new type of energy production system such as integrated gasification combined cycle (IGCC) was developed. Knettig and Beeckmans [9], Doganoglu et al [10] and other workers focused on the efficiency of particle filtration with different parameters mainly on superficial gas velocity, static bed height, different collector particles and distributor. Most of them used the particle generator to produce monodispersed particles (usually about 1 m).…”

Section: Introductionmentioning

confidence: 99%

The effect of ash and filter media characteristics on particle filtration efficiency in fluidized bed

Wey

Chen

Liu

2005

Journal of Hazardous Materials

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“…As is well known [2,5], a fairly high efficiency of collection of dust by a filter with a fluidized granular bed can be maintained in a comparatively narrow range of operating velocities from the rate of minimum fluidization U min,f to the rate of minimum bubble nucleation U min,b . When U min,f is attained, the bed expands and becomes fluidized; its height h and, consequently, porosity ε increase as compared to the values in a fixed bed (Fig.…”

Section: Efficiency Of Collection Of Dust In a Magnetofluidized Bed mentioning

confidence: 99%

Investigation of the properties of a magnetofluidized bed and development of a new gas purification technology based on them for simultaneous removal of solid and gaseous substances from hot waste gases

Dolidovich

2004

J Eng Phys Thermophys

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The results of investigation of the influence of the mechanical, thermal, structural, catalytic, and regenerative characteristics of granular oxide catalysts on the efficiency of decontamination of volatile organic substances in the catalyst unit and of the filtration rate, amount, and concentration of dust, the size of filter particles, the direction and intensity of a magnetic field, and other parameters on the behavior of the particles, the structure, the porosity, the resistance, the optimum fluidization rates, and the efficiency of collection of dust in magnetofluidization of magnetic particles have been given. The diagram and operating principles of a new technology for simultaneous decontamination of volatile organic matter and collection of dust have been presented.Hot waste gases of many industrial processes with a temperature to 900 o C are contaminated with volatile organic substances and dust, whose concentrations vary over a wide range from zero to tens of g/m 3 . Theory and industrial practice offer a few methods of removal of such pollutants from hot gases, including thermal and catalytic decontamination of gaseous organic matter and inertial electrostatic dust control as well as filtration of the gases through ceramic, fiber, or granular filters for collection and removal of finely divided dust. Each of the methods mentioned above possesses its inherent advantages and disadvantages, a detailed discussion of which is beyond the scope of the present paper, where the emphasis is on the development of new methods and equipment that are based on the principles of filtration of hot gases through a granular bed.It is well known [1-3] that the method of filtration of gases through fixed and fluidized beds is widely used to monitor the emission of dust and has demonstrated its sufficient efficiency for particles with a wide range of sizes. Filtration through a fixed bed ensures a sufficient efficiency of dust collection for relatively high flow rates of the gas. It is particularly suitable for operation under the conditions of higher-than-average temperatures and pressures. However, filtration through a fixed granular bed is characterized by an unstable state, since such a filter is gradually and to an increasingly greater extent clogged with the collected dust and the resistance of the bed continuously grows. In this connection, the granular bed must be regenerated or be replaced by a new one. The inevitable consumption of time by this procedure makes the operating costs of the process of gas purification higher. Furthermore, filters with a fixed bed are unsuitable for operation with sticking-together volatile ashes and similar substances.One possible means of overcoming this drawback is the operation of a granular filter in the regime of a fluidized bed, which allows continuous removal and introduction of a filter medium. Fluidized-bed filters possess the advantages of continuous operation with higher flow rates of the gas; they are more suitable in situations in which the adhesion of dust to the surface...

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Capture of monodispersed aerosol particles in a fixed and in a fluidized bed

Cited by 38 publications

References 4 publications

A study of inertial effects in granular bed filtration

A study of inertial effects in granular bed filtration

The effect of ash and filter media characteristics on particle filtration efficiency in fluidized bed

Investigation of the properties of a magnetofluidized bed and development of a new gas purification technology based on them for simultaneous removal of solid and gaseous substances from hot waste gases

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