Mixing and Dispersion

Mixing height The height above an internal or external pollutant source within which emitted pollutants are dispersed and mixed with the surrounding atmosphere. In meteorological terms, this is the area below the inversion layer. 

Kim VS, Skachkov VV (1980) Dispersion and mixing in the processes of manufacture and processing of plastic materials, Moscow, Chemistry, p 240 (in Russian)... 

In the case where two particles are involved, those that are not in close proximity will not react, whereas those that are close will undergo solid state reaction with ease. This is due to the fact that cations and/or anions from one structure must be transported, or interchange by some mechcinlsm, to the other structure in order to form a completely new compound. Thus, the degree of dispersion and mixing of one reacting solid with emother is important to the overall mechanism of solid state... 

Unconfined explosion Unconfined explosions occur in the open. This type of explosion is usually the result of a flammable gas spill. The gas is dispersed and mixed with air until it comes in contact with an ignition source. Unconfined explosions are rarer than confined explosions because the explosive material is frequently diluted below the LFL by wind dispersion. These explosions are destructive because large quantities of gas and large areas are frequently involved. 

Formation of an explosive cloud This step is often done using two computer models. The first is a source emissions model which calculates what happens at the interface between the contained material and the atmosphere into which it is being released. The second is a dispersion model which calculates how the released material disperses and mixes with the air. 

A problem In the analysis of these data Is the potential masking of some sources of variability by other correlated variables which may be difficult to quantify. For example, the potential meteorological Influences of atmospheric dispersion and mixing, scavenging differences between warm and cold clouds, variable rates of oxidation of sulfur and nitrogen species, and the dilution effect of variable rain volume may mask source-receptor chemical relationships. A particular problem Is that meteorological data and source-receptor locations share directional dependence. 

EXAMPLE 6.10 Air-Stripping tower with first-order degradation, modeled as plugfiow, plug flow with dispersion, and mixed tanks-in-series reactors... 

Prepare a neutralizing solution of water/NaDH/NaHCD3. Add it to the Carbopol resin dispersion and mix until homogeneous. 

Thus far developed is the need tor dilution water, arithmetic for determining volumes and a simple but unique approach to low dilution water use rates incorporating the volumes of water retained internal to the process. It also is necessary to develop the need for an economical, simple method of water injection, dispersion and mixing. 

On the average, normal flow is presumed to be between the two extremes. plug flow and complete mixing. This is shown in curves C and D in Fig. 2. Note as dispersive and mixing forces become increasingly important, the RTD curves become increasingly more ekewed as more... 

The most common example of dispersive mixing of particulate solid agglomerates is the dispersion and mixing of carbon black into a rubber compound. The dispersion of such a system is schematically represented in Fig. 3.22. However, the break up of particulate agglomerates is best explained using an ideal system of two small spherical particles that need to be separated and dispersed during a mixing process. 

Clayton, C. G., Ball, A. M. and Spackman, R. (1968) Dispersion and Mixing during Turbulent Flow in a Circular Pipe. UK Atomic Energy Authority Res. Group Report AERE-R 5569. 

The static inline mixer shown in Figure 10.53 is effective in both laminar and turbulent flow, and can be used to mix viscous mixtures. The division and rotation of the fluid at each element cause rapid radical mixing see Rosenzweig (1977) and Baker (1991). The dispersion and mixing of liquids in pipes is discussed by Zughi et al. (2003) and Lee and Brodkey (1964). 

Middleton, J.C. (1992), Gas-liquid dispersion and mixing, in Mixing in the Process Industries , Butterworth-Heinemann, Woburn, MA. 

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