Vacuum vapor condensation

In filter operation, it is essential that the gas be kept above its dew point to avoid water-vapor condensation on the bags and resiilting plugging of the bag pores. However, fabric filters have been used successfully in steam atmospheres, such as those encountered in vacuum diyers. In such cases, the housing is generally steam-traced. 

A distillation column is operating at 27.5 inches mercury vacuum, referenced to a 30-inch barometer. This is the pressure at the inlet to the ejector. Due to pressure drop through a vapor condenser and trays of a distillation column, the column bottoms pressure is 23 inches vacu-... 

Vacuum (a) Removal of liquid or vapor at greater rate than entering a vessel, capacity determined by volume displaced. (b) Injecting cold liquid into hot (steamed out) vessel, the condensing steam will create vacuum, and must be relieved. Capacity is equivalent to vapor condensed. 

Vacuum metalizing is the process of coating a workpiece with metal by flash heating metal vapor in a high-vacuum chamber containing the workpiece. The vapor condenses on all exposed surfaces. 

Implosion. The reverse of explosion—when the walls of a confining vessel collapse inwards, instead of bursting outwards. For instance, when a thin-walled glass container is partially filled with boiling water, sealed and then cooled, the vessel may collapse with a loud noise. This is due to the fact that water vapor condenses on cooling, creating a partial vacuum inside the vessel. This causes the atmosphere, which is at a higher pressure, to push the walls of the container towards the inside until they are broken... 

Flavor Extraction and Concentration. The apparatus used for the steam vacuum stripping consisted of a Nickerson-Likens extractor as modified by Schultz et al. (2). The sample/water slurry was maintained at a boil of 57-60°C (600-610 itm gauge pressure) for one hour. During this time, approximately 200 mL of water vapor and flavor volatiles vaporized, condensed, and were collected in the 250 mL flask. A needle-valve was attached to a glass tube in the second neck of the sample flask to admit a controlled stream of charcoal filtered air through the sample for even boiling under vacuum. 

Barometric-leg pumps are used for assisting in maintaining a vacuum when condensable vapors are involved. Auxiliary pumps are necessary to remove any fixed gases that may accumulate in the leg. For water condensation, the leg usually empties into an open well, and the vertical length of the leg must be longer than 34 ft. 

Typical all-glass air-cooled oil diffusion pump, shown with appropriate connections to the vacuum manifold and to the mechanical forepump. Cooling of the vapor condensation area can be achieved with a small electric fan or a compressed air line (not shown). The use of a liquid nitrogen trap is optional. 

The quinonoid form of p-xylylene reacts as a diradical would. It can be produced in quantitative yield by vacuum vapor phase pyrolysis of di-p-xylylene at 550 to 600° C (30). Condensation of the monomer to crystalline polymer does not occur in the gas phase under the vacuum con-... 

The usual procedure for decolorization involves the addition of a small amount of charcoal to a hot, nearly saturated solution of the compound to be purified. This is followed by a period of heating and gravity filtration to remove the charcoal. Gravity filtration is required because charcoal will usually pass through filter paper if vacuum filtration is employed. It is important to minimize crystalfization of the compound during the filtration, and this may conveniently be done by inserting the stem of a short-stemmed filter funnel into the neck of the flask in which the solution is being heated. The hot vapors condense in the funnel and heat it. 

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