Flow-through cyclone

In a separate investigation on the fragility of agglomerates, we have determined that the agglomerates up to modest sizes are sufficiently robust to withstand the rigors of the flow through cyclones and electrostatic precipitators (27). The research is based on experimental results with inertial separation devices (impactors) and comparing the experienced shear stresses in impactors as determined from theory, with the shear stresses experienced in cyclones. 

As mentioned in Chap. 1, cyclones work as a result of the centrifugal forces acting on the particles suspended in the swirling gas stream. This causes the particles, which are denser than the gas, to move outward to the cyclone wall, along which they are transported downward to the dust exit. The cleaned gas leaves near the centerline, in a reverse-flow cyclone through the roof. In a once-through or flow-through cyclone, the cleaned gas exits out the bottom. ... 

Fig. 13.3.3. Left Wright-Austin type 31L CLC vapor/liquid cyclone separator. Courtesy Hayward Industrial Products, Inc. Right A generic flow-through cyclone design...

Cyclone Pressure Drop. Typical cyclone pressure drops range from 250 to 2000 Pa. Most data are reported for clean air flowing through the cyclone and these data are conservative for design purposes. Many investigators have unsuccessfully attempted to relate pressure drops to inlet and oudet dimension ratios. Manufacturers caUbration curves or experimental measurements on cyclones of similar dimension should be used where possible. If a rehable experimental measurement is available, however, the pressure drop at other conditions can be estimated by first evaluating the constant i in equation 17. 

By integrating Eq. (13.35) step by step in time, the particle trajectory of the particle may be obtained. In the integration, the interaction between the particle and the wall may be approximated as being fully elastic however, when the particle hits the sidewall of the cyclone, the particle may be treated as being collected and the computation for the particle may terminated in order to save the computational time that may be required to track the particle to the bottom of the cyclone. If the particle trajectories for a range of particle diameters at different rates of fluid flow through the cyclone are determined, then the particle efficiency curve and the cut-off particle diameter of the cyclone may be obtained. 

Solids of group C are very fine-grained, cohesive powders (e.g. flour, fines from cyclones, and electrostatic filters) that virtually cannot be fluidized without fluidization aids. The adhesion forces between particles are stronger than the forces that the fluid can exert on the particles. Gas flow through the bed forms channels extending from the grid to the top of the bed, and the pressure drop across the bed is lower than the value from cq 1. Fluidization properties can be improved by the use of mechanical equipment (agitators, vibrators) or flowability additives such as Aerosil. 

Gas exiting the gasifier flows through a cyclone for removal of entrained solids (char, ash, and sorbent) and then to the product gas... 

IBAD The interim biological agent detector (IBAD) is composed of a particle-size sorter/counter, a wet cyclone sampler, a manual identifier, and a flow-through colorimetric ticket assay. Agent identification occurs within 20 minutes. 

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