Slugging classifications

Powder Classification Techniques. The Geldart (1973) fluidization, and Dixon (1981) slugging classifications have been found useful in explaining ... 

The following comments are based on the findings of Wypych (1989b) who compared the actual conveying characteristics of several materials with the slugging classifications of Dixon (1979) and Dixon (1981). 

For a product that is well contained inside a particular group (i.e., A, B, C or D), the Dixon (1981) slugging diagram and classifications generally provide a good initial indication of what to expect when the product is conveyed in the dense-phase mode. 

Materials that lie close to or are on a classification boundary may exhibit slugging behavior from either one of the adjoining categories. This could be explained further by the particle size distribution problem or limitation described above. 

Classify the bulk solid according to the Dixon (1979, 1981) slugging diagram that matches the existing or proposed diameter of pipeline. Based on the research and consulting experience of the author, the following possibilities are proposed in relation to the Dixon (1979) classifications. 

This comprehensive definition makes it elear that a wide number of substances may be eonsidered to be pestieides, and that the eommonality among all pestieides is their ability to provide eontrol over pests. A variety of classifications for pesticides have been developed that are specific for the type of pest controlled. Insecticides, for example, are pesticides that control insects, while herbicides control weeds and fungicides control plant diseases (molds). In addition to these major classifications of pesticides, there are many other classifications. These include nematicides (for nematode control), acaracides (mite control), rodenticides (rodent control), molluscicide (snail and slug control), algacides (algal control), bacteriocides (bacterial control), and defoliants (leaf control). 

Perhaps the simplest classification of flow regimes is on the basis of the superficial Reynolds number of each phase. Such a Reynolds number is expressed on the basis of the tube diameter (or an apparent hydraulic radius for noncircular channels), the gas or liquid superficial mass-velocity, and the gas or liquid viscosity. At least four types of flow are then possible, namely liquid in apparent viscous or turbulent flow combined with gas in apparent viscous or turbulent flow. The critical Reynolds number would seem to be a rather uncertain quantity with this definition. In usage, a value of 2000 has been suggested (L6) and widely adopted for this purpose. Other workers (N4, S5) have found that superficial liquid Reynolds numbers of 8000 are required to give turbulent behavior in horizontal or vertical bubble, plug, slug or froth flow. Therefore, although this classification based on superficial Reynolds number is widely used... 

Classiflcations of Fluidization Behavior Geldart [Powder Technology, 7, 285 (1973)] and later Dixon [Pneumatic Conveying, Plastics Conveying and Bulk Storage, Butters (ed.). Applied Science Publishers, 1981] developed a classification of fluidization/aeration behavior from studies of fluidized beds and slugging in vertical tubes. 

In small channels, a number of flow patterns can be observed, and the same terminology and classifications as in large channels are commonly used. Because of the dominance of the surface tension forces, stratified flow is rarely observed in small channels. In general, bubble flow appears at low gas flow rates. As the gas flow rate increases, Taylor bubbles form. With further increase in the gas flow rate, annular flow appears with the liquid forming an annulus which wets the wall. At high gas and liquid flow rates, chum flow occurs where there is a liquid film at the wall and the gas flow in the center is interrupted by the firequent appearance of frothy bubbles and slugs. 

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