Series fractionation

Loss of Heat in Series Fractionation System - In series fractionation, i.e., where the bottoms from the first column feeds into the second column and the bottoms from the second feeds into the third, it is possible for the loss of heat input to a column to overpressure the following column. Loss of heat results in some of the light ends remaining with the bottoms and being transferred to the next column as feed. Under this circumstance, the overhead load of the second column may consist of its normal vapor load, plus the light ends from the first column. If the second column does not have the condensing capacity for the additional vapor load, excessive pressure could occur. 

Adaughterx/weff-daughter and the daughter will be effectively supported by a greater amount of parent than that in secular equilibrium. These dynamical effects will result in greater U-series fractionation than expected in static systems. 

THE ROLE OF SOURCE HETEROGENEITIES ON U-SERIES FRACTIONATION IN HOTSPOT MAGMATISM... 

Osmond J. K. (2003) Uranium-series fractionation in mafic extmsives. A/)/)/. Geochem. 18, 127-134. 

Electric power loss Accumulation of noncondensibles Failure of automatic controls Loss of heat in series fractionation Volatile material entering system Heat exchanger tube failure... 

Commencing with the fraction next to the most soluble one (fraction 6 in this case) the liquor is poured into the most soluble fraction and the crystals allowed to drain as thoroughly as time allows. The liquor from fraction 5 is then poured onto the crystals in 6, that from fraction 4 onto the crystals in 5, etc., until the liquor from fraction 1 is poured onto the crystals in 2. Thus there has been accomplished a one-series fractionation, f Since fraction 1 is now dry, more solvent must be added to it. The volume of solvent must be somewhat smaller than the amount of solution that it is desired to pour from this fraction in the next fractionation. 

Fig. 5A. R vs. Ri for fatty acids of various chain lengths. The figure applies only to the special case of acetoacetate formation where 2-carbon fragments are converted quantitatively to acetoacetate (see text). R = C 0 C 00H ratio for carboxyl-labeled fatty acids Ri = C 0 C 00H ratio for penultimately labeled fatty acids c = number of carbons in a fatty acid (even series) / fractional degree of the conversion, (CH3CO—) —> (—CH2CO—) / = 1.0 is represented by the point (R = 1.0, Ri = 1.0). Note that when R = 1.0, Ri > 1.0. Small rectangular area is enlarged in Fig. 5B.

The step with the longest time limits the cycle time. Alternatively, if more than one step is carried out in the same equipment, the cycle time is limited by the longest series of steps in the same equipment. The batch cycle time must be at least as long as the longest step. The rest of the equipment other than the limiting step is then idle for some fraction of the batch cycle. 

Vaseline A trade name for soft paraffin. Yellow and white semi-solid, partly translucent mixtures of hydrocarbons of the paraffin series ranging from CijHji to C2oH42- Obtained from the high-boiling fractions of petroleum... 

The solubility of hydrocarbon liquids from the same chemical family diminishes as the molecular weight increases. This effect is particularly sensitive thus in the paraffin series, the solubility expressed in mole fraction is divided by a factor of about five when the number of carbon atoms is increased by one. The result is that heavy paraffin solubilities are extremely small. The polynuclear aromatics have high solubilities in water which makes it difficult to eliminate them by steam stripping. 

In such a plant the gas stream passes through a series of fractionating columns in which liquids are heated at the bottom and partly vaporised, and gases are cooled and condensed at the top of the column. Gas flows up the column and liquid flows down through the column, coming into close contact at trays in the column. Lighter components are stripped to the top and heavier products stripped to the bottom of the tower. 

The virial series in temis of the packing fraction q = upa /3 is then... 

The molecule decomposes by elimination of CF, which should occur with equal probabilities from each ring when energy is randomized. However, at pressures in excess of 100 Torr there is a measurable increase in the fraction of decomposition in the ring that was initially excited. From an analysis of the relative product yield versus pressure, it was deduced that energy flows between the two cyclopropyl rings with a rate of only 3x10 s In a related set of experiments Rabinovitch et al [116] studied the series of chemically activated fliioroalkyl cyclopropanes ... 

Figure Bl.21.3. Direct lattices (at left) and corresponding reciprocal lattices (at right) of a series of connnonly occurring two-dimensional superlattices. Black circles correspond to the ideal (1 x 1) surface structure, while grey circles represent adatoms in the direct lattice (arbitrarily placed in hollow positions) and open diamonds represent fractional-order beams m the reciprocal space. Unit cells in direct space and in reciprocal space are outlined.

Originally, general methods of separation were based on small differences in the solubilities of their salts, for examples the nitrates, and a laborious series of fractional crystallisations had to be carried out to obtain the pure salts. In a few cases, individual lanthanides could be separated because they yielded oxidation states other than three. Thus the commonest lanthanide, cerium, exhibits oxidation states of h-3 and -t-4 hence oxidation of a mixture of lanthanide salts in alkaline solution with chlorine yields the soluble chlorates(I) of all the -1-3 lanthanides (which are not oxidised) but gives a precipitate of cerium(IV) hydroxide, Ce(OH)4, since this is too weak a base to form a chlorate(I). In some cases also, preferential reduction to the metal by sodium amalgam could be used to separate out individual lanthanides. 

The so-called hydro-vac pump, shown in Fig. 11, 22, 2 (the upper half of the mercury reservoir and the column above it are insulated by a layer of asbestos), is an inexpensive, all-glass, mercury diffusion pump, which can be used in series either with an oil pmnp or with a water Alter pmnp (compare Fig. 11,21, 1) capable of producing a vacuum of at least 2 mm. It is accordingly of particular value in the organic laboratory for vacuum distillations, fractionations, sublimations and pyrolyses as well as for molecular distillations (see Section 11,26). The hydro-vac... 

FIGURE 2 11 Distillation of crude oil yields a series of volatile fractions having the names indicated along wih a nonvolatile residue The number of carbon atoms that characterize the hydrocarbons in each frac tion IS approximate... 

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