Solids particle size

Roy et al. (R3) define the critical solids holdup as the maximum quantity of solids that can be held in suspension in an agitated liquid. They present measurements of this factor for various values of gas velocity, gas distribution, solid-particle size, liquid surface tension, liquid viscosity, and a solid-liquid wettability parameter, and they propose the following two correlations in terms of dimensionless groups containing these parameters ... 

The suspended solid particle size and the volume of effluent also must be considered in examining deposition in the subsurface. For example, under leaching of a waste disposal site or following irrigation with sewage effluent, the coarse fraction of suspended solids is retained in the upper layer, while the finer colloidal fraction is more mobile, and its transport is controlled by the porosity of the subsurface solid phase. 

This equation has been deduced from studies conducted with bed diameters of 7.6-130 cm, minimum fluidization velocities of 0.5-20 cm/s, solid particle sizes of 0.006-0.045 cm, and us - wfm< 48 cm/s. To calculate an average value of the bubble velocity, an average bubble diameter should be used. This diameter can be taken to be equal to the bubble diameter at z = Hfl2. Thus, to calculate the bubble diameter and thus the bubble velocity, the fluidized bed height should be known. To solve the problem, an iteration method should be used (Figure 3.60). 

Pore-diffusion resistance Reactions involve solid particle size greater than about 1.6 mm All fast, noncatalytic gas-solid (G/S) reactions such as combustion and gasification Reactors with particle size lower than 100 pm to 0.1 mm Catalytic bubbling fluidized beds (BFB) Slurry reactors... 

The most common interferences are absorption and/or enhancement of the element of interest by other elements in the matrix. Line overlaps may also occur. In the analysis of solids, particle size and geological effects can be important. Computer programs are available to correct for all of these interferences. 

The current status of prediction and modelling in the area of fuel spray combustion requires, among other parameters, the measurement of droplet or solid particle size distribution and the relative velocity between the fuel and the surrounding gas. Many optical techniques, based on laser light scattering, have been investigated to this purpose (Refs.1,2,2,]+,, 6 and j), but the only system able to simultaneously determine the size and the velocity is the dual-beam laser Doppler velocimeter shown in Figure 1. 

Related Calculations. This procedure can be used to analyze either wet or dry solids particle size distributions. Particle size distributions from grinding or combustion and particles from crystallizers are described by the same mathematics. See Example 10.6 for an example of a situation in which the size distribution is based on a known size-distribution function rather than on an experimental sample. 

An important aspect of the design of three phase bubble columns is the variation of catalyst distribution along the reactor height, and its effect on reactor performance. Many factors influence the degree of catalyst distribution, including gas velocity, liquid velocity, solid particle size, phase densities, slurry viscosity, and, to a lesser extent, column diameter, solid shape and chemical affinity between the solid and liquid phases. 

For the tritiation of gases and liquids, exchange occurs efficiently however, for the labeling of crystalline solids, particle size is important.20 Studies with phenanthrene show that at room temperature a linear relationship [Eq. (14)] exists between log specific activity (A in pCi/mg) and the inverse square of r, where r (in mm) is half the average mesh diameter of the particles. 

Adlington and Thompson1 reported that the presence of solids had little influence on gas holdup below nominal gas velocities of about 1.5 cm s 1. At higher gas velocities, the gas holdup was decreased by the solids but was relatively independent of the solids particle size. Viswanathan et al.140 found that, in an air-water sy stem, the gas holdup in beds of small particles (0.649-, or 0.928-mm glass beads) was lower than in a solid-free system, whereas the gas holdup in beds of large particles (4-miti glass beads) was higher than in a solid-free system. 

The effects of suspended solid particles on liquid-phase axial dispersion in a cocurrent-upflow system have been studied by Schiigerl123 and Michelsen and Ostergaard.82 They showed that, in a three-phase column, the axial dispersion increases with gas rate. Unlike in a gas-liquid bubble-column, the liquid-phase axial dispersion coefficient in a three-phase column depends upon the liquid velocity. The nature of the effect is, however, dependent upon the gas rate and solids particle size. Similarly, the nature of the effect of solid size on the axial dispersion depends on the gas and liquid flow rates. 

Increasing the solid particle size or density favors bed expansion. This effect was observed by Bhatia and Epstein (1974), Kim et al. (1975), and Nicklin (1962). 

Figure 2. Pore size distribution of model material obtained from H4T4 at T =6.5. Four different solid particle sizes were used.

Figure 3. Solid frameworks with different solid particle size, (a) R=1.05 and (b) R=0.5. The presence of micropores is evident in (b).

Solid particle size distribution, retained on mesh by wt. 

Liquid-solid mixtures that do not settle out rapidly are usually treated as non-Newtonian fluids. This will usually be the case if the solid particle size is less than about 200 microns (0.2 mm). Larger particle sizes will form settling slurries and require a critical velocity to maintain the solids in suspension. Correlations for critical velocity and pressure drop are given in Perry and Green (1997). 

The sol-gel process is a wet-chemical technique (Chemical Solution Deposition) for the fabrication of metal oxide starting either from a chemical solution (sol short for solution) or colloidal particles (sol for nanoscale particle) to produce an integrated network (gel). Typical precursors are metal alkoxides and metal chlorides, which undergo hydrolysis and polycondensation reactions to form a colloid [a system composed of solid particles (size... 

Feed solid concentration Solid particle size (nun) ... 

Solid concentration 25% to 65% w/w solid particle size 20 to 300 pm. For finer particle size, watch for non-Newtonian behavior. For higher concentrations, consider short pumping runs only for small concentrations, beware of settling out. For larger particles, watch for settling out. 

Latexes—These are dispersions of homopolymers and copolymers in water that are produced by anionic emulsion polymerization and contain 50% solids. Particle size is low (0.2 ym) as is viscosity (20-30 centlpoises). To produce film forming properties, homopolymer latexes must be plasticized. They are supplied either with or without plasticizer. Certain copolymer latexes such as those with acrylates are self-plasticized and do... 

Here we need to choose both the solid particle size dp and the ratio /3. The considerations leading to the choices for these parameters are the... 

---