Flash distillation operating equations

Derive and plot the operating equation for a binary flash distillation on a y-x diagram solve both sequential and simultaneous binary flash distillation problems... 

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. 

In the previous section we saw that the RT curve took the place of the equilibrium curve in binary flash distillation. For multiconponent flash distillation the y-x equilibrium curve is replaced by equilibrium expressions of the form y = K X and the combination of the operating equations and equilibrium are summed using Hxj = 1, Sy = 1, or Zy - ZX = 0. Since the operating equations for well-mixed permeators are similar to the operating equations for flash distillation fHoffman. 20031. if we can write the rate expression in the form y = Xj, then the mathematics to solve the permeation problem will be very... 

The relatively low partial pressure of carbon monoxide in the flash-tank has implications for catalyst stability. Since the rhodium catalyst exists principally as iodocarbonyl complexes (e.g., [Rh(CO)2l2] and [RtKCO LJ-), loss of CO ligands and precipitation of insoluble species (e.g., Rhl3) can be problematic. The conventional Monsanto process operates with a relatively high water concentration (10-15%, w/w) that helps to maintain catalyst stability and solubility (as discussed later). However, this operation results in a costly separation process to dry the product, typically requiring three distillation columns. The presence of water also results in the occurrence of the WGS reaction (Equation (2)), in competition with the desired carbonylation process, resulting in a lower utilization of CO. 

Consider the hypothetical perfect separation of a mixture of ethylene and ethane into pure products by distillation as shown below. Two schemes are to be considered conventional distillation and distillation using a heat pump with reboiler liquid flashing. In both cases the column will operate at a pressure of 200 psia, at which the average relative volatility is 1.55. A reflux ratio of 1.10 times minimum, as computed from the Underwood equation, is to be used. Other conditions for the scheme using reboiler liquid flashing are shown below. Calculate for each scheme ... 

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