Drown-out

Based on differences in melting points and Hquid-phase solubilities four modes of operation possible drown-out, isothermal evaporation, adiabatic evaporation, and cooling (choice depends on stream characteristics). 

Order of preference adiabatic evaporation > isothermal evaporation > cooling >drown-out. 

Eor drown-out, look for MSA in which the component to be crystallised has low solubihty, while other components have high solubihty (MSA should be completely miscible with feed mixture). 

Fig. 11.8. Aluminium alloy quickly necks when it is drown out.

Fig. 11.9. Polythene forms o stable neck when it is drown out drown polythene is very strong.

Fig. 23.10. Cold-drawing of o linear polymer the molecules ore drown out and aligned giving, after o draw ratio of about 4, o material which is much stronger in the draw direction than it was before.

The concept of programmed operation can also be applied to other types of batch crystallization e.g. precipitation via drowning-out with miscible solvents (Jones and Teodossiev, 1988). 

Figure 9.3 Potassium sulphate crystals formed by. a) cooling, (h) drowning-out with acetone Jones etai, 1987)...

The presenee of the seeond solvent during drowning-out erystallization has a marked effeet on the erystallization kineties and eonsequent partiele... 

Berry, D.A., Dye, S.R. and Ng, K.M., 1997. Synthesis of drowning-out based crystallization separations. American Institute of Chemical Engineers Journal, 43, 91. 

Knockout or drown-out is generally not preferred as it involves adding a further extraneous material to the process. If it is to be successful, it requires a steep solubility curve versus the fraction of nonsolvent added. 

Apart from a few applications, such as UV disinfection and lacquer hardening, the intensity of UV radiation is well below that of visible light in ambient daylight or indoor lighting. A UV sensor must therefore be insensitive to visible light, otherwise the detection signal would easily be drowned out by the visible fraction of the radiation spectrum. Sensors that fulfill this requirement have a selective spectral sensitivity in the UV range. There are two important selectivities, known as visible-blindness and solar-blindness. 

Case study 2 Drowning-out Crystallization Solvent Design... 

Table 3 Design results of optimal solvent for drowning out crystallization...

I started to explain, and was drowned out as Matteo and the two women both started to tell him who I... 

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