Granular filtration

While the development of codeposition theories was essentially dormant, the understanding of the kinetics of particle deposition from suspensions was rapidly evolving. The omnipresence of the interaction of particles with surfaces [70] and the importance to deep-bed granular filtration, deposition of paints, fouling of coolant circuits, chemical reactors and membranes, led to careful theoretical and experimental investigations of the mechanism of deposition. The theory is most advanced in the area of filtration and a number of comprehensive reviews exist [71-73]. It is striking that of... 

Tien, C., Granular Filtration of Aerosols and Hydrosols, Butterworth, Stoneham, MA, 1989. 

The collection efficiency of a fiber is defined as the ratio of the number of particles striking the fiber to the number which would strike it if the streamlines were not diverted [Dorman, 1966]. For particles with dp > 1 pm, the particles are collected primarily by inertial impaction and interception. Collection by diffusion is only important for submicron particles. In the following, we only discuss the methodology of collection efficiency by interception. Details about the filtration of fine and ultrafine powders or granular filtration in general can be found in Davies (1973), Fuchs (1964), Dickey (1961), Matteson and Orr (1987), and Tien (1989). 

Tien, C. (1989). Granular Filtration of Aerosols and Hydrosols. Stoneham, Mass. Butterworths. White, H. J. (1963). Industrial Electrostatic Precipitation. Reading, Mass. Addison-Wesley. 

C. Tien, "Granular filtration of aerosols and hydrosols". Series in Chemical Engineering, p.65, Butterworths, Boston (1989)... 

Crossflow membrane separations, crossflow filtration and granular filtration... 

In Section 7.2.2, we consider fixed-bed granular filtration for clarifying dilute suspensions of particles from a liquid. We will identify the similarities between this process and the fixed-bed adsorption/desorption processes studied in Section 7.1.1 both processes employ a low velocity bulk liquid flow through a bed of fixed particles and solute molecules or particles are removed from the liquid by forces acting perpendicular to the fixed particles. Both processes achieve high levels of purification. From a black-box type of perspective, granular filtration may also look very similar to the dead-end filtration studied in Section 6.3.3.1, but there are significant differences. 

Very detailed models of granular filtration have been developed using such idealizations of the porous medium (Tien, 1989). A simple aspect of this filtration is that, as the liquid flows down the porous medium, particles are transported perpendicular to the flow by electrostatic force. Brownian difiusion, various surface interaction forces and interception. Gravitational force is also present its... 

Figure 7.2.10. Fixed-bed granular filtration (a) various mechanisms of particle capture by a spherical collector granule (after Davis (2001)) (b) granular packed-bed schematic for filtration.

This equation, along with equation (7.2.177) for e, relation (7.2.174) for the increase in pressure gradient and expression (7.2.173) for the time-dependent increase of a , govern the granular filtration process subject to the following initial and boundary conditions ... 

It is useful to summarize the common operating conditions in granular filtration in drinking water and... 

---