Removal of particles

Disk, pulp, and sheet filters accomphsh extreme clarification. Not infrequently their mission is complete removal of particles above a... 

Flotation is a physical process involving relative interaction of three phases solid, water, and air. An understanding of the wettability of the solid surface, physical surface, and chemical phenomena by which the flotation reagents act and the mechanical factors that determine particle-bubble attachment and removal of particle-laden bubbles, is helpful in designing and operating flotation systems successfully. 

Removal of particles from liquid, as with polymer additives which induce clay flocculation. 

The collection technique involves the removal of particles from the air stream. The two principal methods are filtration and impaction. Filtrahon consists of collecting particles on a filter surface by three processes—direct interception, inertial impaction, and diffusion (5). Filtration attempts to remove a very high percentage of the mass and number of particles by these three processes. Any size classification is done by a preclassifier, such as an impactor, before the particle stream reaches the surface of the filter. 

Electrostatic precipitator A filtering system for the removal of particles from an air stream by giving them an electrical charge. The charged particles are attracted to plates of opposite polarity onto which they adhere. The precipitators are classified as... 

Commerciol Equipment for Collection or Removal of Particles from a Gas... 

Removal of particles from the air stream is generally carried out in a cyclone, positioned outside the building and taking particles from all sources in the building. Care should be taken to position cyclones away from noise-sensitive areas since both ducts and cyclones can be noisy, especially if grits or chips are being carried. 

Microfiltration and ultrafiltration have recently been introduced for the removal of particles down to any desired size. Their capital cost is relatively high. Experience with them is limited, and a short trial with a small-scale pilot element is advisable. Prediction of full-scale performance from such trials is normally quite reliable. 

The solid-liquid separation of shinies containing particles below 10 pm is difficult by conventional filtration techniques. A conventional approach would be to use a slurry thickener in which the formation of a filter cake is restricted and the product is discharged continuously as concentrated slurry. Such filters use filter cloths as the filtration medium and are limited to concentrating particles above 5 xm in size. Dead end membrane microfiltration, in which the particle-containing fluid is pumped directly through a polymeric membrane, is used for the industrial clarification and sterilisation of liquids. Such process allows the removal of particles down to 0.1 xm or less, but is only suitable for feeds containing very low concentrations of particles as otherwise the membrane becomes too rapidly clogged.2,4,8... 

From Figure 10.22, for 90 per cent removal of particles above 20 pm... 

Modeling studies have shown that when the bed is not monosized and the difference in particle sizes is great enough, it is possible that the large particles will not reach a lower settling velocity than the small particles hence the large particles will remain in the bottom of the bed (Myska and Svec, 1994). If biofilm thickness control is desired, removal of particles at a location other than the free surface would have to be implemented in this case. 

At sufficiently high velocity of fluid upward through a bed of particles, the particles become entrained and do not settle that is, the particles are carried up with the fluid. Elutriation is the selective removal of particles by entrainment, on the basis of size. 

The main problems involved in the removal of particles from a gas stream have been reviewed by Ashman(51), Stairmand and Nonhobel152 and more recently by Swift(53). The main reasons for removing particles from an effluent gas are ... 

The advantages of fluidized beds compared to fixed bed reactors are improved heat and mass transfer, an easier passage through the bed for foreign material and unwanted micro-organisms, a lower pressure drop, better control of the thickness of the biofilm and the easy removal of particles from the bed in order to remove excess biomass (Epstein, 2003). 

Primary Removal of particles and Removal of dissolved Removal of divalent ions Removal of... 

Generally, particulate matter is eliminated by filtration, but the word elimination or even the concept of being substantially free of as appear in some compendia, are levels practically impossible to reach. In fact, complying with pharmacopeia prescription is limited to a removal of particles above a certain size, since the elimination of particles becomes increasingly more difficult the smaller the particle is. Elimination difficulty seemingly increases in an exponential fashion as the size decreases. 

The separated particles should reach the wall when the feed leaves the top end of the tube, as shown by the locus of a particle in Figure 9.3a. The elimination of df from Equations 9.10 and 9.11 and integration with boundary conditions (r = at z = 0 and r = r2 at z = Z) give the maximum flow rate for perfect removal of particles from the feed suspension. 

Let us assume that turbulence in the tank keeps the suspended particle concentration homogeneous, but that at the bottom of the tank the particles can sink through some screen below which no water currents exist (Fig. 23.2 b). In the absence of any external particle fluxes or in situ production/removal of particles, the mass balance equation for suspended particle mass is given by equating the rate of change of particle mass in the water volume V with time with the rate of loss due to settling ... 

These relations are used in Example 18.5 to find the size of a separator corresponding to a specified critical particle diameter, and to the reverse problem of finding the extent of removal of particles when the diameter of the vessel and the velocity are specified. 

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