Differential condensation

This process has been used for various situations (1—14). Eor the condensation of a single component from a binary gas mixture, the gas-stream sensible heat and mass-transfer equations for a differential condenser section take the following forms ... 

Differential condensation in which the liquid separates from the vapour from which it has condensed. This process is analogous to differential, or Rayleigh, distillation, and the condensation curve can be calculated using methods similar to those for determining the change in composition in differential distillation see Volume 2, Chapter 11. 

It is normal practice to assume that integral condensation occurs. The conditions for integral condensation will be approached if condensation is carried out in one pass, so that the liquid and vapour follow the same path as in a vertical condenser with condensation inside or outside the tubes. In a horizontal shell-side condenser the condensate will tend to separate from the vapour. The mean temperature difference will be lower for differential condensation, and arrangements where liquid separation is likely to occur should generally be avoided for the condensation of mixed vapours. 

Fig. 3. Four-line differential condensation TVA system [15]. 1, heated sample 2, 3, 4, 5 stopcocks (large bore, right-angle type) 6, 7, 8, 9, initial cold traps 10, 11, 12, 13, Pirani gauge heads 14, main cold trap 15, exhaust Pirani gauge head 16, 17, product collection points.

Fig. 53a. Differential condensation TVA curves for 20 mg film samples of (i) PVC Breon 113, (ii) PMM FR 1. Heating rate 10 degC min 1 [194],...

A process that is closely related to sinple batch distillation is differential condensation fTreybal. 19801. In this process vapor is slowly condensed and the condensate liquid is rapidly withdrawn. A derivation similar to the derivation of the Raleigh equation for a binary system gives. 

D18. A differential condensation [see Eq. f9-1411 is done for a binary mixture of ethanol and water. The feed is 0.5 kmol of vapor that is 0.10 mole fraction ethanol. The differential condensation is continued until the vapor remaining is yo final = 0-5 mole fraction ethanol. Find the values of Dfinai and the condensate and the average mole fraction of ethanol in the condensate, x avg- Note... 

Variants of TVA are differential condensation TVA [903] and sub-ambient TVA or SATVA [910, 938]. In SATVA the condensable gases and volatile liquids are further fractionated volatile components are collected in gas cells and less volatile liquid fractions are separated and characterised by GC-MS. SATVA consists in the slow, controlled, distillation of the volatile products from the -196°C trap (where they have been collected) as it is heated up to room temperature. As they distil, MS or IR identifies the volatiles and at the same time they are collected in narrow fractions for further analysis. Continuous pressure monitoring during distillation is recorded as a SATVA curve [939]. McGill et al [940,941] have indicated that the very simple technique of trap-to-trap distillation of trace amounts of liquid-nitrogen condensable volatiles can be used for qualitative... 

A partial condenser may produce any of several results (I) If time of contact between vapor product and liquid reflux is sufficient, the two will be in equilibrium with each other and the condenser provides an equilibrium condensation. (2) If the condensate is removed as rapidly as it forms, a differential condensation may occur. (3) If cooling is very rapid, little mass transfer between vapor and condensate results, and the two will have essentially the same composition. 

It is clear from table 21.1 and fig. 21.1 that the lanthanide distribution in the composite of North American shales (NASC) is different from that of the chondrites and the sun s atmosphere. Since the differences are a smooth function of atomic number (except for Eu), they are probably a result of processes of internal planetary differentiation. Differential condensation from a gas does not produce such smooth distributions (Boynton, 1975). What, then, does the NASC distribution represent, or tell us about the history of Earth ... 

In many ways condensation is just the reverse of vaporization, although some of the vaporization mechanisms cannot be mechanically duplicated in condensing equipment. Differential condensation, in which the condensate is removed as soon as it is formed, is not practiced commercially. 

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