Mole percent

Yields are in moles percent moles of starting material. ... 

Fig. 3. Theoretical mole percent of the principal combustion products of hydrocarbon fuels for fuel hydrogen carbon ratios from 1, eg, to 4, eg, CH, ...

Example 23 Estimate the vapor viscosity of a mixture of propane and methane. Assume 60 mole percent methane and 40 mole percent propane at 125 C and 10.34 MPa total pressure. The low pressure viscosity is 0.0123 op. Use Eq. (2-102) ... 

Experiment diffusion coefficients are scarce and not highly accurate, especially in the liquid phase, leading to prediction methods with marginal accuracy. However, use of the v ues predicted are generally suit le for engineering calculations. At concentrations above about 10 mole percent, predicted values should be used with caution. Diffu-sivities in liquids are lO -lO times lower than those in gases. 

For predic ting diffiisivities in binary polar or associating liquid systems at liign solute dilution, the method of Wilke and Chang " defined in Eq. (2-156) can be utilized. The Tyn and Cains equation (2-152) can be used to determine the molar volume of the solute at the normal boihng point. Errors average 20 percent, with occasional errors of 35 percent. The method is not considered to be accurate above a solute concentration of 5 mole percent. 

For concentrated binary nonpolar liquid systems (more than 5 mole percent solute), the diffiisivity can be estimated by a molar average mixing rule developed by Caldwell and Babb, " Eq. (2-156). 

For estimating the diffusivity of the dilute solute (10 mole percent) in water, the method of Hayduk and Laudie, Eq. (2-159), applies. 

Many more correlations are available for diffusion coefficients in the liquid phase than for the gas phase. Most, however, are restiicied to binary diffusion at infinite dilution D°s of lo self-diffusivity D -. This reflects the much greater complexity of liquids on a molecular level. For example, gas-phase diffusion exhibits neghgible composition effects and deviations from thermodynamic ideahty. Conversely, liquid-phase diffusion almost always involves volumetiic and thermodynamic effects due to composition variations. For concentrations greater than a few mole percent of A and B, corrections are needed to obtain the true diffusivity. Furthermore, there are many conditions that do not fit any of the correlations presented here. Thus, careful consideration is needed to produce a reasonable estimate. Again, if diffusivity data are available at the conditions of interest, then they are strongly preferred over the predictions of any correlations. 

An example of heterogeneous-azeotrope formation is shown in Fig. 13-13 for the water-normal butanol system at 101.3 kPa. At liquid compositions between 0 and 3 mole percent butanol and between 40 and 100 mole percent butanol, the liquid phase is homogeneous. Phase sphtting into two separate liquid phases (one with 3 mole percent butanol and the other with 40 mole percent butanol) occurs for any overall hquid composition between 3 and 40 mole percent butanol. A miuimum-boihug heterogeneous azeotrope occurs at 92°C (198°F) when the vapor composition and the over l composition of the two liquid phases are 75 mole percent butanol. 

Mole percent chloroform or ethyl acetate in liquid... 

Pressures can be specified at any level below the safe working pressure of the column. The condenser pressure will be set at 275.8 kPa (40 psia), and all pressure drops within the column will be neglected. The eqnihbrinm curve in Fig. 13-35 represents data at that pressure. AU heat leaks will be assumed to be zero. The feed composition is 40 mole percent of the more volatile component 1, and the feed rate is 0.126 (kg-mol)/s [1000 (lb-mol)/h] of saturated liquid (q = 1). The feed-stage location is fixed at stage 4 and the total number of stages at eight. 

The original column normally has less than 7 mol percent i-Cs in the overhead and less than 3 mole percent n-C4 in the bottoms product when operating at a distillate rate of D/F = 0.489. Can these product purities he produced on the smaller column at D/F = 0.489 ... 

A typical apphcatiou of a simple batch still might be distillation of an ethanol-water mixture at 101.3 kPa (1 atm). The initial charge is 100 mol of ethanol at 18 mole percent, aud the mixture must be reduced to a maximum ethanol concentration in the stiU of 6 mole percent. By using equilibrium data interpolated from Table 13-1,... 

To illustrate the use of these equations, consider a charge of 520 mol of an ethanol-water mixture containing 18 mole percent ethanol to be distilled at 101.3 kPa (1 atm). Vaporization rate is 75 moFh, and the product specification is 80 mole percent ethanol. Let L/V = 0.75, corresponding to a reflux ratio R = 3.0. If the system has seven theo-... 

Example 10 Calculation of Multicomponent Batch Distillation A charge of 45.4 kg mol (100 Ih-mol) of 25 mole percent heuzeue, 50 mole percent monochlorohenzene (MCB), and 25 mole percent orthodichloro-henzene (DCB) is to he distilled in a hatch still consisting of a rehoiler, a column containing 10 theoretical stages, a total condenser, a reflux drum, and a distillate accumulator. Condenser-reflux drum and tray holdups are 0.0056 and... 

From these results, 22.98 Ih-mol, or almost 23 percent of the charge, would he recycled for redistillation. AU three products are at least 98 mole percent pure. 

Selection of Solubility Data Solubility values determine the liquid rate necessaiy for complete or economic solute recoveiy and so are essential to design. Equihbrium data generally will be found in one of three forms (1) solubility data expressed either as solubility in weight or mole percent or as Heniy s-law coefficients, (2) pure-component vapor pressures, or (3) equilibrium distribution coefficients (iC values). Data for specific systems may be found in Sec. 2 additional references to sources of data are presented in this section. 

It should be clear from this example that there is considerable room for error when approximate design methods are employed in situations involving large heat effects, even for a case in which the solute concentration in the inlet gas was only 6 mole percent. 

The reaction of lithium with methyl chloride in ether solution produces a solution of methyllithium from which most of the relatively insoluble lithium chloride precipitates. Ethereal solutions of halide-free" methyllithium, containing 2-5 mole percent of lithium chloride, were formerly marketed by Foote Mineral Company and by Lithium Corporation of America, Inc., but this product has been discontinued by both companies. Comparable solutions are also marketed by Alfa Products and by Aldrich Chemical Company these solutions have a limited shelf-life and older solutions have often deteriorated... 

A pipeline is flowing 3.6 standard million cubic feet per day. The gas is made up of the following components 85% methane, 10% ethane, 4% butane, 1% nitrogen. The values are given as a mole percent. The flowing temperature is 80°F and the pressure is 300 psig. 

The ACF is the actual cubic feet of gas measured at t, F and P, psig. SCF represents standard conditions at 70 F and 14.6 psia. The formulas provided require input information on the pressure and temperature of the fuel gas, the fuel gas analysis by volume (or mole percent if the pressures are sufficiently low), and the percent excess air. The calculation provides the air to fuel ratio required for complete combustion. 

Here Q is the solute concentration and R the gas constant. This is in fact obeyed over a rather wide range of concentrations, almost up to solute mole fractions of 0.61, with an error of only 25 percent. This is remarkable, since the van t Hoff equation is rigorous only in the infinitely dilute limit. Even in the case of highly nonideal solutions, for example a solution with a ratios of 1.5 and e ratios of 4, the van t Hoff equation is still obeyed quite well for concentrations up to about 6 mole percent. It appears from these results that the van t Hoff approximation is much more sensitive to the nonideality of the solutions, and not that sensitive... 

The molecular simulations also showed that electro-osmosis is also observed in aqueous electrolyte solutions, as long as the external electric field is reversed periodically to prevent the ions from accumulating near the membrane. An example of this is shown in Fig. 10, which shows the effect of an electric field on a 4.67 mole percent aqueous LiCl solution at 25°C. It is quite clear that the mobility of the solvent molecules increases as a result of... 

FIG. 10 Effect of an electric field (Eg) on the mean-squared displacement perpendicular to the plane of the membrane for a 4.67 mole percent aqueous LiCl solution at 25°C and 1 bar [25]. 

From Eq. (4-la) the stoichiometric concentration of methane in oxygen is 1 part in 3 = 33.3 mole percent methane. From Eq. (4-lb) the approximate stoichiometric concentration of methane in air is 1 part in 3 -E (158/21) = 9.5 mole percent methane. Tims, a mixtnre of 15 mole percent methane in oxygen has a stoichiometric ratio (p = 15/33.3 = 0.45 (lean), while the same methane concentration in air has a stoichiometric ratio (p = 15/9.5 = 1.58 (rich). 

For paraffins the stoichiometric ratio decreases as the nnmber of carbon atoms increases. Using a more precise calcnlation (which inclndes other species snch as CO, OH, etc.) than that shown in Eq. (4-lb), methane s stoichiometric ratio in air is 9.48 mole percent, propane s is 4.01 mole percent, and hexane s is 2.16 mole percent. Hydrogen, which combines with oxygen to form only water, has a stoichiometric ratio of 29.6 mole percent in air. 

The offgases from the two vacnnm colnmns, at the vacnnm pnmp discharge, normally contain 1.3 mole percent organic vapor (Cg to Cg aromatics) in air, which slightly exceeds the lower flammable limit of the... 

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