Vacuum pump, compression

The actual internal step of solvent recovery involves more than simple condensation in a heat exchanger. The vacuum pump compresses the vapor (Chapter 2.2.3) removed from the work chamber, which results in condensation. This vapor is then condensed further in a heat exchanger. In the absence of air, heat transfer when condensing a pure solvent vapor can be very rapid. 

The so-called hyperbar vacuum filtration is a combination of vacuum and pressure filtration in a pull—push arrangement, whereby a vacuum pump of a fan generates vacuum downstream of the filter medium, while a compressor maintains higher-than-atmospheric pressure upstream. If, for example, the vacuum produced is 80 kPa, ie, absolute pressure of 20 kPa, and the absolute pressure before the filter is 150 kPa, the total pressure drop of 130 kPa is created across the filter medium. This is a new idea in principle but in practice requires three primary movers a Hquid pump to pump in the suspension, a vacuum pump to produce the vacuum, and a compressor to supply the compressed air. The cost of having to provide, install, and maintain one additional primary mover has deterred the development of hyperbar vacuum filtration only Andrit2 in Austria offers a system commercially. 

Optimum Design of Pumping, Compression, and Vacuum Systems... 

The ejector is widely used as a vacuum pump, where it is staged when required to achieve deeper vacuum levels. If the motive fluid pressure is sufficiently high, the ejector can compress gas to a slightly positive pressure. Ejectors are used both as subsonic and supersonic devices. The design must incorporate the appropriate nozzle and diffuser compatible with the gas velocity. The ejector is one of the ( to liquid carryover in the suction gas. 

The Nash vacuum pump or compressor has only one moving part—a balanced rotor that runs without any internal lubrication. Such simplicity is possible because all functions of mechanical pistons or vanes are performed by a rotating band of liquid compressant. 

Moisture or even slugs of liquid entering the inlet of a liquid-ring vacuum pump will not harm it. Such liquid becomes an addition to the liquid compressant. Vapor is often condensed in a vacuum pump. The condensate is also added to the liquid compressant. 

Compression may be from below atmospheric as in a vacuum pump or above atmospheric as for the majority of process applications. The work done by Scheeh - is useful. 

The synthesis of aromatic amines is an active and important area of research.2 Many methods are available in the literature for the synthesis of these compounds. Though some of these are widely used, still they have limitations based on safety or handling considerations. For example, catalytic hydrogenation3 of nitro or azido compounds in the presence of metals such as palladium on carbon or Raney nickel require stringent precautions because of their flammable nature in the presence of air. In addition, these methods require compressed hydrogen gas and a vacuum pump to create high pressure within the reaction flask. To overcome these difficulties, several new methods have been reported in the... 

Power requirements for compressors and vacuum pumps must be considered when wiring plans are made. Both compressed air and vacuum are frequently used in laboratories. Sometimes both can be piped to more than one laboratory room from a central location. Air pressure will usually be sufficient for laboratory applications, but vacuum may not always be, in which case a separate vacuum pump would be required. 

Even a small compressor tends to be very noisy and for that reason should not be in the laboratory proper. Rough plumbing will carry air to the laboratory area. Since the moisture in compressed air causes rusting, the use of rust-resistant pipe will substantially lengthen the life of the air filters. Vacuum pumps, on the other hand, are usually not too noisy to be in the laboratory, although the pump selected should be checked for noise before such a decision is made. 

A scroll vacuum pump uses two interleaved Archimedean spiral-shaped scrolls to pump or compress gases (see Fig. 1.9). One of the scrolls is fixed, while the other orbits eccentrically without rotating, thereby trapping and compressing gases between the scrolls and moving it towards the outlet. 

Fig. 2.29.1. Working schema of a dry vacuum pump operating on the so-called claw principle. 1 rotors 2, compression chamber 3, suction chamber 4, exhaust slit 5, suction slit 6, purge between stages (Figure from [2.241).

Boyle s experiments with the vacuum pump ceased in 1662, when Hooke moved to London to become curator of the Royal Society. However, by this time, Boyle and Hooke had performed a number of additional experiments that are described in the second edition of Spring of the Air, published in 1669. Included in the second edition was a statement of what is now known as Boyle s law the pressure of a gas is inversely proportional to its volume. In other words, if the pressure is doubled, the gas is compressed to one-half of its former volume and if the pressure is halved, the volume doubles. 

Like Roots pumps, claw pumps belong to the group of dry compressing rotary piston vacuum pumps (or rotary vacuum pumps). These pumps may have several stages their rotors have the shape of claws. 

The pumps of the DRYVAC family are the classic dry compressing claw vacuum pumps that are preferably used in the semiconductor industry, whereby the pumps need to meet a variety of special requirements. In semiconductor processes, as in many other vacuum applications, the formation of particles and dusts during the process and/or in the course of compressing the pumped substances to atmospheric pressure within the pump, is unavoidable. In the case of vacuum pumps operating on the claw principle it is possible to convey particles through the pump by means of so called pneumatic conveying". This prevents the deposition of particles and... 

---