Solids concentration and

In hydroseparator tests, it is necessaiy to measure solids concentrations and size distributions of both the supernatant sample withdrawn and the frac tion remaining in the cylinder. The volume of the latter sample should be such as to produce a solids concentration that would be typical of a readily pumped underflow shiny. 

The method is apphcable for unflocculated pulps or those in which the ionic characteristics of the solution produce a flocculent structure. If polymeric flocculants are used, the floccule size will be highly dependent on the feed concentration, and an approach based on the Kynch theoiy is preferred. In this method, the test is carried out at the expec ted feed solids concentration and is continued until underflow concentration is achieved in the cyhnder. To determine the unit area, Talmage and Fitch (op. cit.) proposed an equation derived from a relationship equivalent to that shown in Eq. (18-45) ... 

FIG. 18-85 Depth correction factorto he applied to unit areas determined with Wilhelm-Naide and direct methods. Velocity ratio calculated using tangents to settling cun e at a particular settled solids concentration and at start of test. 

Agitation by a wide spatula may be substituted for hand agitation, but only after it has been determined by feel that the spatula will provide the needed agitation. If this cannot be done, then confirmation of proper agitation must be based on back-calculated feed solids concentrations and/or particle size analyses of the filter cakes. 

Pulpy solids such as paper stock Single suction. Double suction only used on very slight solids concentrations and then with special end clearance wearing fits. Closed. Open type used to be standard but change to end clearance wearing fits made closed impellers better suited. 

The inverse relationship between dissolved solids concentration and pressure is illustrated by the figures given for low-pressure boiler waters in Table 17.6. That there is room for different opinions is shown by contrasting the BSS and ASME recommendations. Whilst both of these authorities propose essentially similar figures for feed-water (Table 17.7), some of the ASME boiler-water figures are substantially below their BS equivalents. This is probably due to the increasing trend towards higher heat fluxes than formerly in some low-pressure plant, particularly waste-heat boilers. 

The need to separate solid and liquid phases is probably the most common phase separation requirement in the process industries, and a variety of techniques is used (Figure 10.9). Separation is effected by either the difference in density between the liquid and solids, using either gravity or centrifugal force, or, for filtration, depends on the particle size and shape. The most suitable technique to use will depend on the solids concentration and feed rate, as well as the size and nature of the solid particles. The range of application of various techniques and equipment, as a function of slurry concentration and particle size, is shown in Figure 10.10. 

The feed enters near the center of the tank, and the liquid flows upward and overflows the top of the tank. The solids loading of the feed is 0.5 lbm of solids per gallon of slurry, and the feed rate is 50,000 gpm. What is the total solids concentration and the particle size distribution in the overflow Density of solids is 100 lbm/ft3. Assume that (1) the particles are spherical (2) the particles in the tank are unhindered and (3) the feed and overflow have the same properties as water. 

In the top (clarifying) zone the relatively clear liquid moves upward and overflows the top. In the middle zone the solid particles settle as the displaced liquid moves upward, and both the local solids concentration and the settling velocity vary from point to point. In the bottom (compressed) zone, the solids and liquid both move downward at a rate that is determined mainly by the underflow draw-off rate. For a given feed rate and solids... 

Dou, S., Herb, B., Tuzla, K., and Chen, J. C., Dynamic Variation of Solid Concentration and Heat Transfer Coefficient at Wall of Circulating Fluidized Bed, Fluidization VII, 793-801 (1993)... 

Potthoff, M., and Bohnet, M., Influence of Solids Concentration and Static Mixers on Fluid Dynamics in Three-Phase Fluidized Bed Bioreactors, Chem. Eng. Technol., 16 147 (1993)... 

In order to determine the critical temperature and solids concentration points, stability domain diagrams were constructed as a function of solids concentration and salt, (Figure 6) as well as a function of temperature and salt at fixed values of solids (Figure 7). 

The flow properties of suspensions are complex. The apparent viscosity at a given shear rate increases with increasing solids concentration and rises extremely rapidly when the volume fraction of solids reaches about 50 per cent. The flow properties also depend on the particle size distribution and the particle shape, as well as the flow properties of the suspending liquid. 

Wastewater streams from the utility functions include boiler and cooling tower blowdowns and waste brine and sludge produced by demineralizing and other water treatment systems. The quantity and quality of the wastewater streams depend on the design of the systems and the water source. These streams usually contain high dissolved and suspended solids concentrations and treatment chemicals from the boiler and cooling tower. The blowdown streams also have elevated temperatures. 

For a properly designed and operated cyclone, the sharpness index is constant, typically 0.6. The cut size and apparent bypass are a function of the cyclone geometry, the volumetric feed rate, the material relative density, the feed solids concentration, and the slurry rheology. The relationship for a standard cyclone geometry, where if D. is the cylinder diameter in cm and inlet area = 0.05 D vortex finder diameter = 0.35 Dc ... 

It is evident from Figure 3.32 that fractional gas holdup is decreased by the addition of solids and this decrease is higher for higher gas velocity, solid concentration, and solid density. 

Operating temperatures on shelf-life, while eliminating the effect of other variables (such as encapsulating agent, solids concentration, and powder moisture content) on shelf-life. 

Of course, in a two-phase system,/ + f2 must be equal to 1 (which can be easily checked). Note that Eqs. 3-62 and 3-63 are also valid if one of the phases is a solid (e.g., solid-water partitioning in a lake or in an aquifer, or solid-air partitioning in the atmosphere). In such cases, Kn2 is often expressed by the ratio of mole of i per mass of solid concentration and mole of i per volume concentration, and therefore, rl2 is then given by the ratio of the mass of solid and the volume of the bulk liquid or gas phase present in the system considered. 

Several workers (Kolbel et al. [40, 41], Deckwer et al. [17], Michael and Reicheit [42]) have investigated the heat transfer in BSCR versus solid concentration and particle diameters. Deckwer et al. [17] applied Kolmogoroff s theory of isotropic turbulence in combination with the surface renewal theory of Higbie [43] and suggested the following expression for the heat transfer coefficient in the Fischer-Tropsch synthesis in BSCR ... 

There is hidden assumption in equation 4 that the volume of the solids and liquid retained in ihe cake is negligible. This is reasonable at low concentrations but can lead to errors al high solids concentration and moisture contents of cakes. A corrected value of the concentration c can he used in equation 4 to reduce the errors, i.e.. 

Sorption coefficients quantitatively describe the extent to which an organic chemical is distributed at equilibrium between an environmental solid (i.e., soil, sediment, suspended sediment, wastewater solids) and the aqueous phase it is in contact with. Sorption coefficients depend on (1) the variety of interactions occurring between the solute and the solid and aqueous phases and (2) the effects of environmental and/or experimental variables such as organic matter quantity and type, clay mineral content and type, clay to organic matter ratio, particle size distribution and surface area of the sorbent, pH, ionic strength, suspended particulates or colloidal material, temperature, dissolved organic matter (DOM) concentration, solute and solid concentrations, and phase separation technique. 

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