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Cal Poly Pomona CHE 425 - Problem Set #6

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CHE425: Problem set #61) Run program ABSORP. You need to copy the folder CHE425 into the H: drive or yourflash drive. Open the folder CHE425 and double click on DOSBox.exe. When the prompt“C:\>” appears, type ABSORP and press “ENTER” to run the program. Copy and report thescore and performance number from the program. Type “e” or “exit” and press “ENTER” toexit the DOSBox program.2) 1We have 10 kmol/h of a saturated liquid feed that is 40 mol % benzene and 60 mol %toluene. We desire a distillate composition that is 0.992 mole fraction benzene and a bottomsthat is 0.986 mole fraction toluene. CMO is valid. Assume a constant relative volatility withBT = 2.4. Reflux is returned as a saturated liquid. The column has a partial reboiler and atotal condenser.(a) Use the Fenske equation to determine Nmin.(b) Use the Underwood equation to find (L/D)min(c) For L/D = 1.1(L/D)min, use the previous results and the Gilliland correlation to estimate thetotal number of stages and the optimum feed stage location.Ans:Nm = 10.37, Rmin = 1.7488, N = 24.63) 2We have an existing column that acts as 30 equilibrium contacts. We are separating amulticomponent mixture where LK = 1.1 and LK = 1.0. A recovery fraction of 98% isrequired for the light key in the distillate. Find the recovery fraction of the heavy key in thebottoms. Feed is a saturated liquid that contains zLNK = 0.1, zLK = 0.4, zHK = 0.3, zHNK = 0.2.LNK = 1.25 and HNK = 0.75. Operation is at total reflux.Ans:FR of HK = 0.2634) The following feed of 100 mol/h at the boiling point and 60 psia pressure is fed to afractionating tower: n-butane (xa = 0.40), n-pentane (xb = 0.25), n-hexane (xc = 0.20), and n-heptane (xd = 0.15). This feed is distilled so that 95% of the n-pentane is recovered in thedistillate and 95% of the n-hexane in the bottoms. Calculate the following.(a) Moles per hour and composition of distillate and bottoms.(b) Top and bottom temperature of tower.(c) Minimum stages for total reflux and distribution of other components (trace components)in the distillate and bottoms, i.e, moles and mole fractions.(d) (L/D)min using the Underwood equations.(e) For L/D = 1.3(L/D)min, use the previous results and the Gilliland correlation to estimate thetotal number of stages and the optimum feed stage location.Table 4 Equilibrium K values for light hydrocarbon systems=============================================================11 J. D. Seader and E. J. Henley, Separation Process Principles, Wiley, 199822 J. D. Seader and E. J. Henley, Separation Process Principles, Wiley, 19981(1) ln K = A/T2 + B  C ln(P) , where P is in psia, T is in oR Compound A B C Form=============================================================n-Butane 1280557 7.94986 .96455 (1)n-Pentane 1524891 7.33129 .89143 (1)n-Hexane 1778901 6.96783 .84634 (1)n-Heptane 2013803 6.52914 .79543 (1)Ans: (a) Moles per hour and composition of distillate and bottoms.D = 64.75 mol/h, B = 35.25 mol/h(b) Top and bottom temperature of tower.Dew point temperature, T(R) = 607.22, T(C) = 64.19Bubble point temperature, T(R) = 733.02, T(C) = 134.08(c) Minimum stages for total reflux and distribution of other components (trace components)in the distillate and bottoms, i.e, moles and mole fractions.Nmin = 7.74Table C Product distributionDistillate xdBottoms xbnC4nC5, light key nC6, heavy keynC74023.7512.0788×10-30.61780.36680.01543.21×10-52.38×10-31.2519156.75×10-50.0355 0.5390 0.425564.75 1.0000 35.25 1.0000(d) (L/D)min using the Underwood equations.Rmin = 0.5658(e) For L/D = 1.3(L/D)min, use the previous results and the Gilliland correlation to estimate thetotal number of stages and the optimum feed stage location.Ne + Ns = 18.7, Ne = 10.2, the feed tray is 10 trays from the top.5. Run the ChemSep program and produce Table 5 in the example: DistillationCalculation using ChemSep Software. Copy the ChemSepL folder from theDistribution folder to your H: drive. Open the ChemSepL folder and double click on cs.batto start the program. Note: This program only works properly in your H: drive. If you wantthis program on your flash drive you need to download ChemSep-LITE from the website: http://www.chemsep.org/program/index.html and install it on your flash drive.Example: Distillation Calculation using ChemSep Software“ChemSep is a software system for simulation of distillation, absorption, and extractionoperations. ChemSep integrates flash calculations, the classic equilibrium stage columnmodel and a nonequilibrium or rate-based column model in one easy to use program”.11 http://www.chemsep.org/program/index.html2ChemSep-LITE is available for FREE. It only includes the equilibrium column model and islimited to 10 components and 150 stages.Double click on the cs.bat and the following screen will appearYou can click on the menu: Components, Operation, Properties, Feeds, andSpecifications on the left column to specify your operation and conditions. When all thenecessary specifications are entered into the program, the menu will have a green check nextto it. Let consider the following example:3A butane-pentane splitter is to operate at 8.3 bar with the following feed compositionSaturated liquid feed (kmol/s)Propane,Isobutane,Normal butane,Isopentane,Normal pentaneC3iC4nC4, light keyiC5, heavy keynC5.05.15.25.20.35For a specification of a reflux ratio of 2.5 and split between two components in the bottomiso-pentane/n-pentane = 0.45, determine the compositions of the product streams.You can enter the data given in the example and the following information into the program:Operation Thermodynamics Properties FeedsEquilibrium columnSimple distillationTotal condenserPartial reboilerNumber of stages: 14Feed stage: 6K-value: EOSEquation of state: Soave-RKEnthalpy: Soave-RKLeave blank for Thermodynamic Model ParametersState: Pressure & VaporfractionSpecifications Column SpecificationsConstant pressureColumn heat loss: 0Default stage efficiency: 1Split between two componentsiso-pentane/n-pentane = 0.45You will need to explore this program to be familiar with the menu and sub-menu. Youshould read the ChemSep Help and ChemSep Book to know more about the program andits functions. After you enter all the necessary information into the program you will arrive atthe following screen: 4Choose Quick Solve in the menu and you will get the following results: Table


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