Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Relative volatility factor

As the partial vapour pressures of the individual components add up to the total pressure, the more volatile component accumulates in the vapour phase. This fact constitutes the basis of distillation. The ideal relative volatility factor then results from the vapour pressures of the pure components ... [Pg.71]

The larger the relative volatility factor the more the curves deviate from the bisecting line of an angle, resulting in an improved distillative separability. Unfortunately, most mixtures do not exhibit ideal behaviour. The components do not act independently of each other and instead of Raoult s law the following correlation applies for the partial vapour pressure ... [Pg.72]

The second one uses the mole fraction of the volatile component at the head and sump and the relative volatility factor a ... [Pg.75]

If a two-component mixture is present, the azeotrope can be characterised by the relative volatility factor. If a = 1, an azeotrope point is present. For a two-component mixture, this relative volatility can be defined as follows, equating the fugacity coefficient with 1 ... [Pg.81]

The equipment for continuous distillation can only separate one stage in the equilibrium diagram. Countercurrent distillation, also called rectification, has found widespread application with normal pressure and coarse vacuum distillation when complex mixtures or components with small relative volatility factor are to be separated. The fundamentals are discussed above (2.1.3.3.2) the technical side will be dealt with here [41-45]. [Pg.90]

Type of pollutant Weight % of volatile organic compounds contained In exhaust gas Relative risk factor... [Pg.261]

For an equiUbrium-based separation, a convenient measure of the intrinsic selectivity of the adsorbent is provided by the separation factor which is defined by analogy with the relative volatility as... [Pg.256]

In distillation towers, entrainment lowers the tray efficiency, and 1 pound of entrainment per 10 pounds of liquid is sometimes taken as the hmit for acceptable performance. However, the impact of entrainment on distiUation efficiency depends on the relative volatility of the component being considered. Entrainment has a minor impact on close separations when the difference between vapor and liquid concentration is smaU, but this factor can be dominant for systems where the liquid concentration is much higher than the vapor in equilibrium with it (i.e., when a component of the liquid has a very lowvolatiUty, as in an absorber). [Pg.1412]

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. [Pg.1453]

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. [Pg.70]

N,n = Minimum theoretical stages at total reflux Q = Heat transferred, Btu/hr U - Overall heat transfer coefficient, Btu/hrfP"F u = Vapor velocity, ft/sec U d = Velocity under downcomer, ft/sec VD(js = Downcomer design velocity, GPM/fL Vioad = Column vapor load factor W = Condensate rate, Ibs/hr Xhk = Mol fraction of heavy key component Xlk = Mol fraction of the light key component a, = Relative volatility of component i versus the heavy key component... [Pg.306]

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. [Pg.22]

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 ... [Pg.184]

This term is analogous to relative volatility or its reciprocal (or to an equilibrium selectivity). Similarly, the assumption of a constant separation factor is a useful assumption in many sorptive operations. [It is constant for the Langmuir isotherm, as described below, and for mass-action equilibrium with za = zh in Eq. (16-24).] This gives the constant separation factor isotherm... [Pg.15]

Another measure of the preference of an ion exchanger for one other ionic species is the separation factor a. This is defined in a similar way to relative volatility in vapour-liquid binary systems, and is independent of the valencies of the ions. [Pg.1057]

Gas-liquid relationships, in the geochemical sense, should be considered liquid-solid-gas interactions in the subsurface. The subsurface gas phase is composed of a mixture of gases with various properties, usually found in the free pore spaces of the solid phase. Processes involved in the gas-liquid and gas-solid interface interactions are controlled by factors such as vapor pressure-volatilization, adsorption, solubility, pressure, and temperature. The solubility of a pure gas in a closed system containing water reaches an equilibrium concentration at a constant pressure and temperature. A gas-liquid equilibrium may be described by a partition coefficient, relative volatilization and Henry s law. [Pg.144]

In other words, the equation defines an improvement factor, which consists of the ratio of relative volatility with salt present (calculated using liquid composition on a salt-free basis for direct comparison purposes) to relative volatility at the same liquid composition but without salt present. It relates the logarithm of this improvement factor in a direct proportionality with N3, the mole fraction of salt present in the liquid on a ternary basis. Jaques and Furter (17) tested the equation with data taken at several constant liquid compositions in four alcohol-water-inorganic salt systems, and observed good agreement. [Pg.34]

This equation relates a so-called improvement factor, the logarithm of the ratio of relative volatility with and without salt present, to the salt concentration in the liquid phase under the condition of fixed mixed-solvent composition, by a salt effect parameter k. Usually, the added salt lowers the volatility of both components in the liquid phase. If the extent of this lowering is different for... [Pg.106]

The first two factors help make fractionation better, the last factor makes fractionation worse. How can an operator select the optimum tower pressure, to maximize the benefits of enhanced relative volatility, and reduced tray deck dumping, without unduly promoting jet flooding due to entrainment ... [Pg.31]

The relative volatility or separation factor (a) depends upon the interactions of the solute and the liquid phase, that is, van der Waals cohesive forces. These cohesive forces may be divided into three types ... [Pg.89]

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 ... [Pg.96]

Solvent Mole per cent in charge T, °C. Relative volatility, s Improve- ment factor, Df8/a... [Pg.418]

An adsorbent can be visualized as a porous solid having certain characteristics. When the solid is immersed in a liquid mixture, the pores fill with liquid, which at equilibrium differs in composition from that of (he liquid surrounding the particles. These compositions can then be related to each other by enrichment factors that are analogous lo relative volatility in distillation. The adsorbent is selective for the component that is more concentrated in the pores than in the surrounding liquid. [Pg.40]

The model includes parameters for relative volatility a, vapor velocity v, tray spacing flow constant kv, flooding factor //, vapor py and liquid pL densities, molecular weight MW, and some known upper bound on column flow rates FmaX. [Pg.8]

Experience Factors These are tabulations of efficiencies previously measured for various systems. Tray efficiency is insensitive to tray geometry (above), so in the absence of hydraulic anomalies and issues with VLE data, efficiencies measured in one tower are extensible to others distilling the same system. A small allowance to variations in tray geometry as discussed above is in order. Caution is required with mixed aqueous-organic systems, where concentration may have a marked effect on physical properties, relative volatility, and efficiency. Table 14-12 shows typical tray efficiencies reported in the literature. [Pg.50]

The CLND is limited, of course, to mobile phases that do not contain nitrogen. Acetonitrile and amine modifiers, commonly used in HPLC, are therefore precluded. In addition, the CLND is not readily amenable to non-volatile buffers in the mobile phase. However, it is still possible to determine RRF values for samples run under these non-CLND-compatible HPLC conditions. In such cases, a two-step process is used. First, a CLND-compatible mobile phase (e.g., methanol/water/trifluoroacetic acid) is used to separate the compounds of interest and determine RRF values under those conditions (RRF ). Separately, the UV peak areas obtained using both the CLND-compatible and non-compatible HPLC conditions are compared by analyzing a common sample by both sets of HPLC conditions (apart from the CLND). The peaks of interest must, of course, be tracked to avoid misassignment (e.g., through UV spectra comparison). The relative response factor (RRF ) obtained for the CLND-compatible method can then be used to determine the relative response factor (RRF2)... [Pg.198]

Volatilization rates of chemicals from surface deposits are directly proportional to their relative vapor pressures. The actual rates of loss, or the proportionality constant relating vapor pressure to volatilization rates, are dependent upon external conditions that affect movement away from the evaporating surface, such as wind speed and air turbulence. Initial volatilization of pesticide deposits from leaf surfaces and grass or litter on the forest floor are examples of this type of volatilization. Factors controlling volatilization rates from plants was discussed by Taylor (1). [Pg.195]

The relative volatility, or selectivity factor, for each component in the presence of carbon dioxide is also given in Table I. Relative volatility is defined as the ratio of K-value for component i to K-value for limonene. The K-value for component i is defined as mole fraction i in the vapor (extract) phase to mole fraction i in the liquid (raffinate) phase. [Pg.206]

The selecti vi ti es in the supercritical carbon dioxide extraction of terpenes from the oxy fraction, and the oxy fraction from sesquiterpenes, for lemon oil are shown in Figures 7 and 8, respectively. Figure 7 shows the relative volatility, or selectivity factor, of limonene to geranial as a function of oil solubility in the vapor phase. Operation of the extractor at 308 K and 1 wt% solubility (the highest practical level at this temperature) provides a relative volatility of 2. Operation at 313 K and 2.8 wt% solubility provides a relative volatility of 1.3. The selectivity factors are an order of magnitude lower than the vapor pressure ratios at 303 to 313 K. [Pg.210]


See other pages where Relative volatility factor is mentioned: [Pg.1382]    [Pg.98]    [Pg.213]    [Pg.71]    [Pg.223]    [Pg.408]    [Pg.148]    [Pg.54]    [Pg.760]    [Pg.145]    [Pg.120]    [Pg.1083]    [Pg.273]    [Pg.269]    [Pg.171]    [Pg.418]    [Pg.439]    [Pg.49]   
See also in sourсe #XX -- [ Pg.71 ]




SEARCH



Relative volatility

© 2024 chempedia.info