Deep vacuums

Easy to use in distillation, from deep vacuum where low pressure drop is beneficial, to high pressure where capacity surpasses many trays. 

Nakahira, K. Validation of deep vacuum vapor phase hydrogen peroxide sterilizer retrofit to a production lyophilizer. PDA Asian Symposium, p. 1/6-6/6, Tokyo 1994... 

A satellite, e.g. for radio or TV communication, needs to be robust to withstand its environment in space. In particular, it needs to be protected from the tremendous gravitational forces exerted during take off, from the deep vacuum of space, and from atoms in space. 

The condensing turbine does not produce exhaust steam. All the turbine exhaust steam is turned into water in a surface condenser. We will study surface condensers in Chap. 18. The surface condenser is just like the sort of vacuum condensers we discussed in Chap. 16, sections on steam jets. The exhaust-steam condenses under a deep vacuum— typically 76 mm Hg, or 0.1 atm. Basically, then, a condensing steam... 

Pressure Generally, pressure has little effect on HETP of both random and structured packing, at least above 100 mbar abs. At deep vacuum (<100 mbar), there are data to suggest that efficiency decreases as pressure is lowered for random packings [Zelvinski, Titov, and Shalygin, Khim Tekhnol. Topi. Masel. 12(10) (1966)], but most of these data can also be explained by poor wetting or maldistribution. 

It can be stated that, at the very beginning of the construction of models for heterogeneous-catalytic reactions, a "bifurcation took place models were separated into "real (most of all) and "ideal . These models cannot, however, be opposed they must supplement each other. We cannot ignore the essential dependences of reaction parameters on the surface composition and state of the catalyst (see ref. 169) even if the significance of these dependences has not yet been clarified. This demand is satisfied by the model suggested by Creighton et al. [199] to describe the critical effects obtained in deep vacuum. The authors [199] applied a semi-empirical dependence of the CO sticking coefficients on the surface composition and temperature. 

Thus, in terms of a sufficiently simple two-route mechanism, it is possible to interpret the effects observed by different authors [48, 53, 62, 98] (1) a jumpwise increase in the reaction rate at definite temperatures (2) temperature independence of the rate and simultaneously first order with respect to CO at "low T and Pco (3) zero order with respect to CO at "high T. The model corresponding to the two-route mechanism and using the parameters from ref. 49 predicts the existence of critical effects first discovered by Golchet and White [62] under deep vacuum. 

The columns pressure deserves special attention. The top of both columns is set at 0.066bar with a pressure drop per tray at 500 Pa, a conservative value for vacuum operation. The total pressure drop is accounted for in real stages with 75% overall efficiency. Koch flexitrays with 4 passes are adopted as internals, since these give smaller diameter. However, relatively large values are obtained, of 2.5 and 3.2 m for the bottom and top trays respectively, due to the high throughput and deep vacuum. 

Pressure drop per theoretical stage. This parameter is of major importance at deep vacuum. For instance, a column containing 20 theoretical stages, with a packing that has a pressure drop of 0.2 in of water... 

Figure 8,12c shows that structured packings have a much lower pressure drop per theoretical stage than random packings. This is a major advantage in deep vacuum services. 

Lyophilization (or freeze-drying) is a process utilized to convert a water-soluble material filled into a container to a solid state by removal of the liquid while frozen. The process requires the use of deep vacuums and careful control of temperatures. By conducting the process under reduced pressure, the water in the container converts from ice directly to vapor as heat is applied and is removed from the container by the vacuum. The dissolved solids in the formulation cannot undergo this phase change and remain in the container. At the completion of the cycle, the container will be returned to near atmospheric pressure stoppers are applied or fully seated and crimped as described above. Lyophilization is particularly common with biological materials whose stability in aqueous solution may be relatively poor. The time period in solution and the temperature of the solution are kept at a specified low temperature to prevent product degradation [35],... 

ABB Lummus Global/UOP Styrene monomer Ethylbenzene Vapor-phase dehydrogenation of EB to styrene monomer, high-temperature, deep-vacuum design, 99.9% purity, 97% selectivity 51 1997... 

Air removal is particularly important in porous and equipment loads, but is usually of little importance in the sterilization of aqueous pharmaceutical products. Air removal can be important to the specification of new autoclaves—those which are to be designated only for aqueous product sterilization have no need for the pumps and ancillary equipment required to pull deep vacuums. 

Small disc filters and small single-use slacked disc filters in plastic housings are avail le and have the appearance of cartridge filters but consist of a series of separate membranes rather than of one continuous pleated membrane. This added complexity may make sterilization by saturated steam more difficult. Deep vacuums intended to ensure effective air removal from the filter media... 

In order to prepare ammonium salt solutions of chemical purity, the salts were refined by recrystallizing three times. Ammonia, which had been dried over metallic sodium for ten hours, was recondensed three times. After recondensation, frozen ammonia was evaculated to deep vacuum (10"° mm. Hg). 

The main drawback of chimney trays is that they consume more column height than alternative drawoff devices, resulting in a more expensive arrangement. Chimney trays are also relatively high-pressure-drop devices, which is a major disadvantage in packed columns operating in deep vacuum. 

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