Separation of solids from fluids

Applications of agglomeration in environmental control 5,4,5,3,1 Separation of solids from fluids... 

When the principles of and equipment for the separation of solids from fluids are applied to solids classification, it is desirable to minimize the amount of misplaced material. This is related to the general slope of the grade efficiency curve which can be expressed in terms of a sharpness index defined in many different ways sometimes simply as the slope of the tangent to the curve atxso or, more often, as a ratio of two sizes corresponding to two different percentages on the grade efficiency curve on either side of 50%, i.e. for example ... 

Conveyance of fluids, pressure loss in tubes, fixed, fluidized and entrained beds, compressors and pumps, mixing of fluids, and separation of solids from fluids. 

When eontaminated, polluted, or valuable suspension liquors are present, it becomes necessary to wash the filter cake to effect clean separation of solids from the mother liquor or to recover the mother liquor from the solids. The operation known as dewatering involves forcing a clean fluid through the cake to recover residual liquid retained in the pores, directly after filtering or washing. Dewatering is a complex process on a microscale, because it involves the hydrodynamics of... 

Consider a thin layer solid bowl centrifuge as shown in Figure 4.20. In this device, particles are flung to the wall of the vessel by centrifugal force while liquor either remains stationary in batch operation or overflows a weir in continuous operation. Separation of solid from liquid will be a function of several quantities including particle and fluid densities, particle size, flowrate of slurry, and machine size and design (speed, diameter, separation distance, etc.). A relationship between them can be derived using the transport equations that were derived in Chapter 3, as follows. 

Filtration is the separation of solids from a fluid. While various filtration processes do, in fact, include separation in the ionic and molecular ranges, here we are primarily concerned with particulate filtration. Traditionally, a filter medium is employed to remove particles in the range of 1 to 1,000 micron ( x). 

P.C. Dell Orco, E.F. Gloyna, S. Buelow, Oxidation Processes in the Separation of Solids from Supercritical Water, Supercritical Fluids Engineering Science, Fundamentals and applications, ACS Symposium Series, 514, (1993), 314. 

The potential of supercritical extraction, a separation process in which a gas above its critical temperature is used as a solvent, has been widely recognized in the recent years. The first proposed applications have involved mainly compounds of low volatility, and processes that utilize supercritical fluids for the separation of solids from natural matrices (such as caffeine from coffee beans) are already in industrial operation. The use of supercritical fluids for separation of liquid mixtures, although of wider applicability, has been less well studied as the minimum number of components for any such separation is three (the solvent, and a binary mixture of components to be separated). The experimental study of phase equilibrium in ternary mixtures at high pressures is complicated and theoretical methods to correlate the observed phase behavior are lacking. 

In the filtration process, a liquid containing suspended solids is passed through a porous medium. The solids are trapped against the medium, and the separation of solids from liquids results. For large solid particles, a thick barrier such as sand may be used for smaller particles, a fine filter such as a filter cloth is preferable. Fluid passage may be induced by gravity, positive pressure, or a r acuum. A few of the more popular filter fypes are the plate and frame filter press, and shell and leaf and cartridge filters. 

Filtration is the separation of suspended particles of solids from fluids (liquid or gas) by use of a porous medium (6). It is therefore a sieving process whereby sohds are separated from a solvent and does not involve solutes interacting with surfaces. In discussing oU processing, adsorption can be confused with filtration. For example, it could be argued as to whether soaps and phospholipids were separated by adsorption or filtration. Under low-solubihty conditions (low temperamre and high concentrations), soaps and phospholipids tend to be separated more by filtration than adsorption, and visa versa. Expressed simply, adsorption is described as the assimilation of oil-soluble impurities, whereas filtration is the removal of solid particulates and insoluble contaminants. 

Svarovsky, L. 2000. Efficiency of separation of particles from fluids. In Solid-Liquid Separation, Svarovsky, L. (ed.). London Butterworths-Heinemann. 

The secondary process element (shown in red) separates particulate solids from fluids on the basis of size-exdusion. 

Thirdly, there are those chapters which only needed minor updating and amendments. These include Characterization of Particles Suspended in Liquids, Efficiency of Separation of Particles from Fluids, Hydrocyclones, Separation by Centrifugal Sedimentation, Filtration Fundamentals, Methods for Limiting Cake Growth, Pressure Filtration, Particle-Huid Interaction, Thermodynamics of Solid-Liquid Separation. 

The purpose of filtration is the separation of solids from a fluid phase. The solids, the fluid, or both may be valuable. In most cases, however, one phase is considered to be a waste and its minimization and disposal are important parts of the process. 

Filtration is the separation of a fluid-solids mixture involving passage of most of the fluidthrough a porous barrier which retains most of the solid particulates contained in the mixture. This subsec tion deals only with the filtration of solids from liquids gas filtration is treated in Sec. 17. Filtration is the term for the unit operation. A filter is a piece of unit-operations equipment by which filtration is performed. The filter medium or septum is the barrier that lets the liquid pass while retaining most of the solids it may be a screen, cloth, paper, or bed of solids. The hquid that passes through the filter medium is called the filtrate. 

Filter Any medium used for the separation of solid, gaseous, or liquid contaminants from a gas or fluid stream. The collection efficiency depends on the materials used. Some types of filters are listed here. 

Precipitation When a solid is formed from a solution, or the separation of particles from a fluid by the process of precipitation. 

There exist a number of other methods for the separation of diamondoids from petroleum fluids or natural gas streams (1) a gradient thermal diffusion process [54] is proposed for separation of diamondoids (2) a number of extraction and absorption methods [53,83] have been recommended for removing diamondoid compounds from natural gas streams and (3) separation of certain diamondoids from petroleum fluids has been achieved using zeolites [56, 84] and a number of other solid adsorbents. 

Many mechanical separations involve the movement of solid particles or liquid drops through a fluid. The fluid may be gas or liquid, and it may be flowing or static. As some assortment of examples mention may be made of the removal of dust and fumes from air or flue gas, the removal of solids from liquid wastes to permit discharge into public domain, and of the recovery of acid mists from an acid plant gaseous wastes. 

SFE has been used extensively in the analysis of solid polymers. Supercritical fluid extraction of liquid samples is undertaken less widely because dissolution or entrainment of the matrix can occur. As illustrated elsewhere SFE has also been applied for the analysis of liquid poly(alkylene glycol) (PAG) lubricants and sorbitan ester formulations [370]. The analysis of PAG additives (antioxidants, biocides and anticorrosion, antiwear and antifoaming agents) is hindered by the presence of the low molecular weight PAG matrix (liquid) and therefore a method for the selective separation of additives from PAG is required. The PAG... 

Many engineering operations involve the separation of solid particles from fluids, in which the motion of the particles is a result of a gravitational (or other potential) force. To illustrate this, consider a spherical solid particle with diameter d and density ps, surrounded by a fluid of density p and viscosity /z, which is released and begins to fall (in the x = — z direction) under the influence of gravity. A momentum balance on the particle is simply T,FX = max, where the forces include gravity acting on the solid (T g), the buoyant force due to the fluid (Fb), and the drag exerted by the fluid (FD). The inertial term involves the product of the acceleration (ax = dVx/dt) and the mass (m). The mass that is accelerated includes that of the solid (ms) as well as the virtual mass (m() of the fluid that is displaced by the body as it accelerates. It can be shown that the latter is equal to one-half of the total mass of the displaced fluid, i.e., mf = jms(p/ps). Thus the momentum balance becomes... 

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