Spreadsheet mixture calculation

The system methanol-cyclohexane can be modeled using the NRTL equation. Vapor pressure coefficients for the Antoine equation for pressure in bar and temperature in Kelvin are given in Table 4.176. Data for the NRTL equation at 1 atm are given in Table 4.186. Assume the gas constant R = 8.3145 kIkmol 1-K 1. Set up a spreadsheet to calculate the bubble point of liquid mixtures and plot the x-y diagram. 

From the unknown absorbances at the two wavelengths, calculate the parts per million of Cr and Mn in your unknown using Beer s law for the mixture and the determined constants. Use a spreadsheet similar to the one given in Chapter 16 and in your CD to perform the mixture calculation. The calculated results will have the same units as used in determining the constants. Keep in mind the dilutions made. Report the results for each portion analyzed. 

To calculate the concentrations of phenacetin and caffeine, the absorbances of the phenacetin and caffeine standards and of the methylene chloride extract of the sample must all be read at both 250 and 275 nm. Using these absorbances, calculate the percent phenacetin and caffeine in the ARC tablets and the milligrams of each per tablet. See Chapter 16 for the spectrophotometric detennination of mixtures. Use a spreadsheet similar to the one in Chapter 16 and your CD to do the mixture calculations. 

Obtain an unknown mixture of meta and para isomers from your instructor. Prepare a mixture of this with o-xylene by adding 70 parts of the unknown to 30 parts o-xylene. Run the spectrum on this mixture and, using the baseline method and the same peaks as before, measure Pq/P for the three compounds and calculate log(Po/F)/log(Po/F)ortho for the two unknown isomers. Compare with the calibration curve to determine the percent concentrations of the meta and para isomers use the spreadsheet for calculations. Remember to divide by 0.7 to convert to initial concentrations. 

Prepare an Excel spreadsheet that calculates for a mixture the bubble point at pressures of 15,16,..., 25 atm and produces a plot of the bubble point versus pressure with suitable annotations and title. Use Goal Seek to solve the single nonlinear equation at each pressure. Data for the system are given in Figure 1.4. 

The approach that we have worked out for the titration of a monoprotic weak acid with a strong base can be extended to reactions involving multiprotic acids or bases and mixtures of acids or bases. As the complexity of the titration increases, however, the necessary calculations become more time-consuming. Not surprisingly, a variety of algebraic and computer spreadsheet approaches have been described to aid in constructing titration curves. 

Such calculations can give an approximate estimate of the Hkely maximum yield of explosives and explosives mixtures, and may readily be transferred to a spreadsheet for ease of use. In practice, small charges, particularly of improvised explosives, tend to produce less than their maximum output, and this needs to be estabhshed by experimental measurements. The results of simple calculations such as those above can be particularly helpful in the design of suitable experimental tests of explosives. 

BOX 5.1 Example of a spreadsheet calculation of the expected combined defined effect for a multiple mixture using different amounts of information. Note Tier-1 prediction relies on exposure and EC50 information (toxic unit summation), Tier-2 needs additional concentration response information for calculation of expected combined effects according to the reference models of response addition or concentration addition, and Tier-3 calculation (mixed models) requires information on the relevant mode of action. The sample is based on real analytical and effect data. Source Redrawn from data from Altenburger et al. (2004). 

BOX 5.2 Example of a spreadsheet calculation of toxic risk (msPAF) for a species assemblage in an imaginary aquatic pond as the result of exposure to a mixture of toxicants with diverse and species-dependent toxic modes of action. Note Overall risk values (msPAF) per species group were calculated assuming concentration addition within common modes of action and response addition between modes of action. This example only serves to demonstrate the method of calculation. The SSD information on the mixture constituents as well as the total and bioeffective concentrations in pond water were randomly selected by realistic expert judgement. The gray cells contain examples of the formulas applied. 

The example provided in Table 2 is for a four component mixture of hydrocarbons (methane, ethane, propane, and n-octane). The weighting method is a common calculation procedure that process engineers will encounter many times. Computations for simple systems can be easily set up on an Excel spreadsheet. 

Alami et al. (2005) developed a relatively simple method for estimating the water content of acid gas mixtures. It is too complex to repeat here and probably too complex for multiple hand calculations. However, it is suitable for a spreadsheet calculation. 

A spreadsheet that performs the required material and energy balances and vapor-liquid equilibrium calculations on this process unit is shown on the next page. In the test case, a 40 mole benzene-60 mole% toluene mixture is fed to the evaporator at 120°C and a pressure high enough to assure that the feed stream remains in the liquid state. The unit operates at 7 = lOO C and P = 800 mm Hg. 

Process simulation software can also be used to help build simple energy balances in spreadsheet models, for example, by entering stream data to calculate mixture heat capacities, to calculate stream enthalpies, or to estimate heats of reaction. 

The spreadsheet below is included in your CD, Chapter 16. Check the above calculations. You can use the spreadsheet to solve any two-mixture problem by substituting the appropriate values for Ai, A2, Ki, kyi, k z, and kyz- (Be sure to save the spreadsheet to your desktop before using it.)... 

Selecting the appropriate thermodynamic model and supplying correct parameters is a key step in solving a simulation problem. The purpose of this chapter is to review the fundamentals of phase equilibria in process simulation. Modem thermodynamic methods make possible the treatment of very complex mixtures, including supercritical and subcritical components, hydrocarbons or polar species, water, etc. Such calculations are impossible by hand or even with spreadsheets. However, the user should be aware that only a good understanding of theoretical bases could ensure reliable results. 

The step-by-step procedure described here is for use on a Microsoft Excel , or similar, spreadsheet. For the generic time interval the amounts of heat exchanged with the containment internal atmosphere on the basis of the conditions existing at the start of the same interval are calculated, assuming that in the interval the temperature of the air water-steam mixture remains constant. Then, the balance of these quantities is made and, on the basis of the current heat capacity of the mixture, the variation of its temperature in the time interval and the corresponding final pressure are evaluated. The initial conditions for the subsequent time interval are then calculated. 

If VLE data are available in equation form, spreadsheet calculations can also be used for multiconponent flash distillation. These calculations are illustrated for a chemical mixture that follows Eq. 12-161 for Problem 2.D16. First, the spreadsheet is shown in Figure 2-B3 with the equations in each cell. Cells B3 to B6, C3 to C6, D3 to D6, E3 to E6, F3 to F6, and G3 to G6 are the constants for Eq. (2-161 from Table 2-3. Conditions for the operation are input in cells B7, D7, and F7, and the feed mole fractions are in cells B8, C8, F8, and G9. Eq. 12-161 is programmed for each conponent in cells BIO, Bll, B12, and B13. Then the liquid mole fractions are determined fromEq. 12-381 in cells B15 to B18. These four numbers are summed in cell B19. The Rachford-Rice terms from Eq. 12-421 for each conponent are calculated in cells B20 to B23, and the sum is in B24. 

The new nonpolar, polar, and hydrogen-bonding values for the solvent blend are calculated in three separate equations utilizing the three solubility parameter values of each blend solvent. A computer spreadsheet data file discussed in Chapter 19 can be used to automatically calculate the blend parameters. Blends of two or three solvents with different solubility values can yield a solvent blend with intermediate values that match a specific resin. Two nonresin solvents can be blended to give a solvent mixture that dissolves the resin. 

The procedure for calculation of dew point temperature for any two-component mixture is to assume a trial value of temperature calculate both values of vapor pressure using the Antoine Equation for solvent and nitrogen and using the above equation, solve for the total pressure. When it equals the specified total pressure, the trial temperature is the dew point temperature. Spreadsheets have a "goal-seeking" function to automate this work. 

Prepare an Excel spreadsheet that is similar to the one for the bubble point, but is used to compute the dew point of the same mixture at the same pressures. Put these calculations on the same Worksheet as those for the bubble point. 

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