Vapour-liquid separators

The use of mixed gases is designed to equalize the heat capacities of the two counterflow gas streams and thereby make the exchange process much more efficient. However, the expanded fluid is a mixture of liquid and gas hence a liquid-vapour separator is needed to allow the expanding liquid to precool the vapour. Figure 5.13 shows the cycle as modified by MMR Technologies [53]... 

Fig. 5.13. Schematic diagram of a Klimenko cycle cryocooler. E123 denote heat exchangers V12 3 n are capillary expansion valves S12 3in are liquid-vapour separators [53].

Natural gas expander cycles can be utilized at places with a high-pressure main gas pipeline and a low-pressure distribution line. The natural gas is expanded in a turbine, thereby cooling the exit gas. Dependent on the inlet conditions, the exit temperature will be so low that a part of the gas is condensed, typically around 12 to 30 %. The liquid is separated from the gas flow in a liquid-vapour separator as shown in Figure 11. 

Falling-film evaporators eliminate the problem of a hydrostatic head with liquid phase. The feed enters at the head of the evaporator, is distributed evenly across the heating tubes and, as a result of gravity, flows downward as a thin film. The liquid-vapour separation takes place at the bottom. The falling-film evaporator is widely used for heat-sensitive materials, because the contact time is small and the liquid is not overheated during passage. 

A.F. Oliveira, O. Fatibello-Filho, J.A. Nobrega, Focused-microwave-assisted reaction in flow injection spectrophotometry a new liquid-vapour separation chamber for determination of reducing sugar in wine, Talanta 55 (2001) 677. 

Gerunda, A. (1981) How to size liquid-vapour separators. Chemical Engineering, 4 May, 81-84. 

For a multicomponent system, it is possible to simulate at constant pressure rather than constant volume, as separation into phases of different compositions is still allowed. The method allows one to study straightforwardly phase equilibria in confined systems such as pores [166]. Configuration-biased MC methods can be used in combination with the Gibbs ensemble. An impressive demonstration of this has been the detennination by Siepmaim et al [167] and Smit et al [168] of liquid-vapour coexistence curves for n-alkane chain molecules as long as 48 atoms. 

One of the main attractions of SCF solvents is the ease of separating products at the end of the reaction. For products which are liquids, phase separation can be achieved merely by reducing the pressure. However, it should be remembered that some of the SCF will still remain dissolved in the liquid phase. This may not be a problem in reactions carried out in SCCO2 but it could present difficulties for products isolated on a large scale from flammable SCFs, where outgassing of flammable vapour from the liquid product could occur. 

A solution of propanoic acid (5.92 g, 80mmol) in 1,2,4-trichlorobenzene (80 ml) was heated at 80-100°C. Davy s methyl reagent (12.6 g, 44 mmol), prepared according to [142], was added portionwise in 2 min. The mixture was heated at 140°C during 10 min (caution operate under a hood and trap obnoxious vapours by bleach). It was then cooled to room temperature. The liquid which separated was distilled to give yellow methyl propanedithioate (5.93 g, 49 mmol, 61%), b.p. 57°C/12 torr. 

On-line preconcentration followed by liquid chromatographic separation and cold vapour atomic absorption spectrometry have been used to detect 0.5ppt methylmercuiy in non saline water [43],... 

Absorption Vapour Liquid MSA Separation of C02 from combustion products... 

The sO Called spheroidal state, in which a drop of water or other volatile liquid rolls about on a hot metal plate (or on the surface of a boiling liquid) with only very slow evaporation, is mainly a consequence of the very slow transmission of heat from the solid through the thin layer of vapour separating it from the liquid drop. A beam of light may be passed between the drop and the plate. Poggendorff said that an electric current will not pass from the drop to the hot plate, but Buff showed that a weak current passes and that the drop oscillates, sometimes touching the support. Stark showed that the drop is supported by a layer of vapour but executes oscillations which may sometimes reach the support. 

Distillation is used to separate the components of a liquid mixture by vaporizing the liquids, condensing the vapours and collecting the liquid condensate. Separation is the result of the differing boiling points of the individual constituents of the mixture and the efficiency of the distillation column. You may be required to purify a hquid by distillation, which involves the removal of small quantities of impurities, or to separate a mixture of liquids by fractional distillation, each of which can then be purified by distillation. 

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