Distillation separation factor

The permselectivities, or separation factors, defined by Equation (3) were used to scale the experimental data for design purposes. The system permselectivity is analogous to the distillation separation factor... 

The distillation separation factor for an isotopic mixture or a close boiling mixture is very close to 1. Separation by conventional distillation would be highly energy-intensive and capital-intensive. If, however, a reactive but relatively nonvolatile species 3 is added to a close-boiling binary mixture of species 1 and 2, such that the lighter species 1 reacts according to... 

Irreversible processes are mainly appHed for the separation of heavy stable isotopes, where the separation factors of the more reversible methods, eg, distillation, absorption, or chemical exchange, are so low that the diffusion separation methods become economically more attractive. Although appHcation of these processes is presented in terms of isotope separation, the results are equally vaUd for the description of separation processes for any ideal mixture of very similar constituents such as close-cut petroleum fractions, members of a homologous series of organic compounds, isomeric chemical compounds, or biological materials. 

The suitabiHty and economics of a distillation separation depend on such factors as favorable vapor—Hquid equiHbria, feed composition, number of components to be separated, product purity requirements, the absolute pressure of the distillation, heat sensitivity, corrosivity, and continuous vs batch requirements. Distillation is somewhat energy-inefficient because in the usual case heat added at the base of the column is largely rejected overhead to an ambient sink. However, the source of energy for distillations is often low pressure steam which characteristically is in long supply and thus relatively inexpensive. Also, schemes have been devised for lowering the energy requirements of distillation and are described in many pubHcations (87). 

Selectivity. The relative separation, or selectivity, Ot of a solvent is the ratio of two components in the extraction-solvent phase divided by the ratio of the same components in the feed-solvent phase. The separation power of a hquid-liquid system is governed by the deviation of Ot from unity, analogous to relative volatility in distillation. A relative separation Ot of 1.0 gives no separation of the components between the two liquid phases. Dilute solute concentrations generally give the highest relative separation factors. 

The Smith-Brinkley Method uses two sets of separation factors for the top and bottom parts of the column, in contrast to a single relative volatility for the Underwood Method. The Underwood Method requires knowing the distillate and bottoms compositions to determine the required reflux. The Smith-Brinkley Method starts with the column parameters and calculates the product compositions. This is a great advantage in building a model for hand or small computer calculations. Starting with a base case, the Smith-Brinkley Method can be used to calculate the effect of parameter changes on the product compositions. 

Relative volatility is the volatility separation factor in a vapor-liquid system, i.e., the volatility of one component divided by the volatility of the other. It is the tendency for one component in a liquid mixture to separate upon distillation from the other. The term is expressed as fhe ratio of vapor pressure of the more volatile to the less volatile in the liquid mixture, and therefore g is always equal to 1.0 or greater, g means the relationship of the more volatile or low boiler to the less volatile or high boiler at a constant specific temperature. The greater the value of a, the easier will be the desired separation. Relative volatility can be calculated between any two components in a mixture, binary or multicomponent. One of the substances is chosen as the reference to which the other component is compared. 

By taking the ratio of the distribution coefficients for the two Components i and j, the separation factor can be defined, which is analogous to relative volatility in distillation ... 

An alternative and more widely used technique for lsO production is via water distillation. The separation factors are much smaller than they are for NO, and the number of plates required, the time to production, and the energy demand and capital costs commensurately larger, but cost of feed, ease of handling, and safety concerns favor water distillation. Production columns are located in the United States, Israel, Russia and other countries. The Israeli plant has the advantage of using already partially enriched Dead Sea water as feed. 

B is a powerful neutron absorber and has been employed in reactor control rods, neutron detectors, and other applications. Cascades based on exchange distillation of boron-ether complexes have usefully large a s and were used for 10B/UB isotope separation by the US DOE. Exchange distillation takes advantage of the fact that condensed phase/vapor phase separation factors can be enhanced (as compared to liquid/vapor a s) by association/dissociation equilibria in one or the other phase. At the normal boiling point (173 K) the VPIE for... 

The property of pertechnetate to be easily reduced by hydrochloric acid is utilized in its separation from rhenium by distillation. Perrier and Segre separated both elements by distillation from a mixture of sulfuric and hydrochloric acid at 180-200 °C. Under these conditions about 90% of rhenium is said to pass into the distillate, but almost all the technetium which is reduced to Tc (IV) remains in solution. The separation factor was found to be 50. 

When studying a new separation, the separation factors applicable to the considered medium are first determined in our laboratories. Then the various parameters are fed into a computer which uses a program similar to the one used in fractional distillation. The data obtained are usually in excellent agreement with the results of commercial scale operations. 

Activity coefficients at infinite dilution, of organic solutes in ILs have been reported in the literature during the last years very often [1,2,12,45,64, 65,106,123,144,174-189]. In most cases, a special technique based on the gas chromatographic determination of the solute retention time in a packed column filled with the IL as a stationary phase has been used [45,123,174-176,179,181-187]. An alternative method is the "dilutor technique" [64,65,106, 178,180]. A lot of y 3 (where 1 refers to the solute, i.e., the organic solvent, and 3 to the solvent, i.e., the IL) provide a useful tool for solvent selection in extractive distillation or solvent extraction processes. It is sufficient to know the separation factor of the components to be separated at infinite dilution to determine the applicability of a compound (a new IL) as a selective solvent. 

SEPARATION FACTOR. The reader will recall that the separation factor, a, in Section 2.1.4, is the same as the relative volatility term used in distillation theory. In 1959, Purnell (32,33) introduced another separation factor (S) term to describe the efficiency of a column. It can be used very conveniently to describe efficiency of open tubular columns ... 

As a proof of the feasibility of such direct COSMO-RS process simulation, Taylor et al. [100] have linked the COSMOtherm program into their simulation program CHEMSEP [101] for distillation separation processes. For a number of typical separation problems they report very satisfying results, which are comparable with simulations based on empirical models. The simulation times were only a factor of 2 greater than those using empirical models. The quality of the simulations was considered as comparable to empirical models, although those were based on fitted experimental data. 

The pervaporation separation factor, f3pen,ap, simply equals the product of the evaporation (distillation)... 

Let us first focus on a nonreactive system with constant separation factors. Typical examples are distillation processes with constant relative volatilities or adsorption processes described by competitive Langmuir isotherms. For nonreactive systems with constant separation factors, the constant pattern waves and spreading waves are... 

Sample size, maximum, 223 Sensitivity (detector), 95 Separation, definition of, 4 Separation factor, 20-22, 77 Separation number, 18 Sieving, molecular sieves, 45-47. See also Size exclusion chromatography Silica, surface of, 166, 167, 236, 237 Simulated distillation, 150... 

Cryogenic distillation is used to enrich carbon-13, nitrogen-15, oxygen-17, and oxygen-18. Typical of these processes is carbon monoxide distillation, which has a C-13/C-12 separation factor of 1.008 between the vapor and the liquid. The initial 20-meter packed column is tapered from 2.5 cm at the boiler to 10 cm at the reflux condenser. This brings the... 

Extractive distillation is evaluated as an alternative to ordinary distillation for the separation of propylene-propane mixtures. Particular attention is given to the necessary compromises between different design factors solvent concentration within the primary column, solvent selectivity, solvent loss, etc. A major expense is associated with the sensible heat requirements of the circulating solvent process modifications so as to minimize this expense are discussed. The process analysis explores combinations of solvent selectivity and other solvent properties which might make extractive distillation attractive. It appears that in almost all cases extractive distillation offers no advantage compared with ordinary distillation. Only in special cases may circumstances warrant extractive distillation. External factors favoring the use of extractive distillation are identified. 

A secondary effect of the solvent volatility is on the operating temperature of the extractive distillation column. A more volatile solvent results in a lower average plate temperature. At the lower temperature, the separation factor is generally higher because of higher selectivity. 

The obtained values of FX2 for these samples are plotted against time from solvent injection to establish the maximum value for the separation factor, F12 (max). Further details about the experimental technique are in the original paper (35). The larger the value of FX2 (max), the better the solvent can separate the mixture, indicating a better extractive distillation solvent. This was verified by comparing values for FX2 (max) and infinite dilution relative volatilities (a°i2) for the system n-hexane-benzene with six different solvents. The results presented in... 

The presence of undissociated addition complex in the gas phase, which vaporizes without fractionation with respect to the liquid, reduces the separation factors which could be attained by exchange distillation. 

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