Annular Jet Process

Annular Jet Process Centrifugal suspension separation Coacervation and phase separation Cocrystallization Controlled precipitation Dispersion/suspension polymerization Dripping and jet break up Electrospraying... 

There are a number of process technologies used for annular jet processes. While there are some dominant ones, some smaller or niche processes should not be completely unmentioned. However, as the market is moving and evolving, it is not possible to give a complete overview about technologies, but the interested reader may inform himself by regularly visiting conferences and access the well-established Journals to find out about newer developments. 

At the current time, the annular jet processes most commonly used in food, pharma, cosmetic, and chemistry that produce particles of one or another kind are certainly laminar flow breakup processes. It has to be kept in mind, that the absolute majority of annular jet processes are used in other fields—as fuel engines—or to produce matrix particles, as two material nozzles used in atomization. Those, however, will not be subject to this chapter. 

For the production of core-shell encapsulated products, annular jet processes offer a large number of advantages. Already a vast amount of products is produced using these processes, ranging from chewing gums, tobacco, medical products, supplements to electronic, and chemical applications. 

Annular Jet processes are used widely in industries. A special interest and growing application are processes to produce Micrcapsules with annular gap nozzles. A selection of those processes is presented in this chapter. 

A special niche annular Jet-based process is the flow focusing technology. Here, instead of using a liquid shell material, a matrix sphere is produced, but the outer nozzle is operated with an inert... 

Initially a molten tube of plastic called the Parison is extruded through an annular die. A mould then closes round the parison and a jet of gas inflates it to take up the shape of the mould. This is illustrated in Fig. 4.21(a). Although this process is principally used for the production of bottles (for washing-up liquid, disinfectant, soft drinks, etc.) it is not restricted to small hollow articles. Domestic cold water storage tanks, large storage drums and 2(X)... 

The tendency of premixed flames to detach from the flame holder to stabilize further downstream has also been reported close to the flammability limit in a two-dimensional sudden expansion flow [27]. The change in flame position in the present annular flow arrangement was a consequence of flow oscillations associated with rough combustion, and the flame can be particularly susceptible to detachment and possible extinction, especially at values of equivalence ratio close to the lean flammability limit. Measurements of extinction in opposed jet flames subject to pressure oscillations [28] show that a number of cycles of local flame extinction and relight were required before the flame finally blew off. The number of cycles over which the extinction process occurred depended on the frequency and amplitude of the oscillated input and the equivalence ratios in the opposed jets. Thus the onset of large amplitudes of oscillations in the lean combustor is not likely to lead to instantaneous blow-off, and the availability of a control mechanism to respond to the naturally occurring oscillations at their onset can slow down the progress towards total extinction and restore a stable flame. 

In industrial practice, cooling of the blown film is enhanced from the outside by an annular air jet, which fiows from an air ring (see Fig. 9.20) attached very close to the die and/or the inside by a process called internal bubble cooling (IBC). Note that the air jet usually hits the film... 

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