Particle capture efficiency

Figure 2. Particle capture efficiencies of 8.0-fim and 0.4-fim Nude pore filters for a face velocity of 5 cm/s.

Many solids-handling operations have an effect on the particle size distribution (PSD) of the solid phase. The particle size distribution can also be an important product property. Aspen Plus allows the user to enter a particle size distribution as an attribute of a solid substream. In UniSim Design, the particle size distribution is entered on the PSD Property tab, which appears under worksheet on the stream editor window for any stream that contains a pure or hypothetical solid component. Unit operations such as yield-shift reactor, crusher, screen, cyclone, electrostatic precipitator, and crystallizer can then be set up to modify the particle size distribution, typically by using a conversion function or a particle capture efficiency in each size range. 

In addition dissolved air flotation experiments were carried out to obtain the flotation efficiency under the same experimental conditions as the zeta potential measurement. The values of particle capture efficiency were a maximum when the absolute values of zeta potentials of the bubbles and particles were at a minimum. 

Monodispersed polystyrene latex particles 1.049 pm in diameter (std dev = 0.0587 pm) were captured utilizing a radial flow parallel-plate mobility analyzer (Tardos et. al. 1984). The mobility of the particles was determined from measurements of the collection efficiency of the analyzer by sampling particle number density for the inlet and exit flows (Figure 3-10). The principle was fundamentally that of electrostatic precipitation. The particles were charged by a corona discharge. The particles capture efficiency in the mobility... 

The discussion of the particles capture in the previous section was based on the assumption, that the particles are not subject to the forces from the system liquid - collector. Actually a particle near the surface of collector, is subject to the surface forces of (molecular and electrostatic) interactions, as well as the hydrodynamic force of viscous resistance from the liquid film between the particle and collector. The account of these forces considerably complicates the problem of determining the particles capture efficiency for the given obstacle. 

Most models currently available for blood filtration are based on empirical models/ Bruil proposed a mathematical model for leucocyte filtration process and could explain the filtration law in the plain membrane filter. However, the effect of direct interception in blood filtration is not clearly understood, and the particle capture efficiency may be modelled based on an empirical model proposed by Khilar and Fogler"" for Newtonian liquid flow. With the consideration of the further particle capture due to the reduction of the pore sizes and the porosity of filter fabric by particle bridging, pore blockage, and pore closure, a modified Khilar—Fogler model of the particle capture efficiency by Gruesbeck and Collins" may be applied in blood filtration. 

To analyze the particle capture efficiency of the upper lung, particles of different diameters were initially released with a uniform distribution at the trachea inlet and their trajectories were analyzed. Figure 36 shows the locations at which the particles of different size were captured. It is seen that the relatively large 30-pm particles are mainly deposited on the carina by impaction mechanisms. On the other hand, the 10-nm particles have a more uniform distribution pattern. These small particles are deposited mainly by the diffusion process on the entire passage surface. Very few 1-pm particles are captured by the first lung bifurcation, since for this size range. 

Figure 43 compares the simulated total capture efficiency of the triple bifurcation airway with the experimental data for different particle diameters. In this figure, solid lines denote the simulation results of Mazaheri and Ahmadi and the stars represent the experimental data collected by Hinds.This figure shows that total capture efficiency increases as particle diameter increases. It is also seen that the numerical simulation results are comparable with the experimental data Mazaheri and Ahmadi also showed that when the effect of the turbulence in the lung was neglected, the particle capture efficiencies are reduced by about 40-60%. 

Fig. 57 Comparisons of particle capture efficiency in the human upper oral airway with experimental data (Zahmatkesh et al. )...

Eisentrager A, Vella D, Griffiths IM (2014) Particle capture efficiency in a multi-wire model for high gradient magnetic separation. Appl Phys Lett 105 033508... 

The quantity of interest from a utilitarian point of view is the extent of removal of particles from the air stream in the depth filter. A predictive approach to this usually involves a number of steps. The first step is to calculate the particle capture efficiency of a single fiber element in a filter via a given mechanism, say Ejs due to inertial impaction. In the second step, add up appropriately the corresponding single-fiber capture efficiencies due to the different mechanisms to obtain EtSi the total efficiency for a single fiber, and apply the result to the whole filter bed/depth filter. 

An alternative approach calculates the particle capture efficiency of a single fiber element due to the simultaneous action of different capture mechanisms to obtain Ets and then applies such a result to the whole bed. We will consider these approaches in Section 7.2.2 along with the other capture mechanisms primarily for hydrosol removal by granular filters. 

As we have seen in Section 6.3.1.4 on the removal of particles from air by a fibrous bed via the mechanism of inertial deposition, if one can locate the limiting trajectory (dimension b in Figure 6.3.9A), the particle capture efficiency can be determined (e.g. definition (6.3.42a)). Determination of the limiting trajectory is achieved via particle trajectory analysis in the porous medium, i.e. the granular filter medium. The governing equation for particle motion in the inter-particle space is equation (6.2.45) ... 

All particles of size tp > Pmax will be captured in the device. Thus the grade efficiency function for a disk-stack centrifuge does not depend on the channel height 2b but instead depends on the flow rate per channel. Also, the larger the value of grade efficiency Gritp) for that particle size. 

The complementai y is the cumulative capture efficiency Z (= 1 — Y), which is defined as the feed particles of a given size and smaller which are captured in the cake, which in most dewateiing applications is the product stream. 

List several types of air cleaning devices that can be used to remove airborne particulate matter. Rank these in order of their collection efficiency and typical maximum size particle capture. 

Detailed Evaluation Detailed evaluation is performed by measuring the capture efficiency, either by using the actual contaminant or by using a tracer gas. (In principle, it is possible to use particles as tracers, but gases are usually used as tracers.) The most reliable evaluation is to use the process-generated contaminant, since there are always problems with a tracer, due to the difficulties of feeding the tracer to the source in the same way and in a similar amount as the generated contaminant. ... 

Capture efficiency is the fraction of generated contaminant that is directly captured by the hood. Measurement of capture efficiency involves measuring concentration of process-generated contaminant or a tracer material. Using process-generated contaminant requires use of instruments suited to each specific contaminant and its conditions (temperature, pressure, concentration, form, etc.). In order to facilitate these measurements, a tracer is often substituted for the process-generated contaminant. The tracer is usually a gas (sulfur hexafluoride, nitrous oxide, helium, or similar), but an aerosol (particles) can also be used (potassium iodide, polystyrene particles, microbiological particles, etc.). The chosen tracer should be as similar to the real contaminant as possible, but at the same time should... 

Figure 4-17B. Capture efficiency vs particle size for four standard York-Vane mist eliminators. By permission, Otto H. York Co. Inc.

It is accepted that the radical entry rate coefficient for miniemulsion droplets is substantially lower than for the monomer-swollen particles. This is attributed to a barrier to radical entry into monomer droplets which exists because of the formation of an interface complex of the emulsifier/coemulsifier at the surface of the monomer droplets [24]. The increased radical capture efficiency of particles over monomer droplets is attributed to weakening or elimination of the barrier to radical entry or to monomer diffusion by the presence of polymer. The polymer modifies the particle interface and influences the solubility of emulsifier and coemulsifier in the monomer/polymer phase and the close packing of emulsifier and co emulsifier at the particle surface. Under such conditions the residence time of entered radical increases as well as its propagation efficiency with monomer prior to exit. This increases the rate entry of radicals into particles. 

The capture efficiency of sticky surfaces for dry particles, and of dry surfaces for moist or sticky particles (ascospores or dye particles), agrees reasonably with theory, but dry surfaces are less efficient for dry particles. Theory and experiments on filter efficiency (Dahneke, 1971 Esmen et al., 1978 Ellenbecker et al., 1980) have shown that the critical parameter is the kinetic energy of the particle. Figure 6.4 shows Cp/C, as given by the ratio of catch on non-sticky compared with sticky pine needles (Chamberlain Little, 1980). Also shown are the results of experiments by Ellenbecker et al. (1980) (0.2-//m fly ash particles on 8-fim steel fibres) and Aylor Ferrandino (1985) (Lycopodium particles... 

The capture of acid particles, or acid droplets, by forests is considered an important cause of acidification of soils and water courses in mountain regions (Lovett, 1984 Lovett Reiners, 1986). Field experiments on the required scale are hardly feasible. Several authors have made calculations of the wind profile within the forest, and the capture efficiency of model leaves and twigs in the canopy. Figure 6.12 shows the results of calculations by Belot (1975), Slinn (1982), and Lovett (1984). When expressed in terms of the normalised velocity of deposition v., there is little difference in Fig. 6.9 between the calculated... 

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