When To Use Depriester Chart How To Simplify The
Carry out bubble and dew point calculations for a given mixture Carry out flash calculation in order to determine the vapor/liquidFraction as well as the mixture composition of each phase at specified conditions using available K-Values etc.RKAC1 is vaporpressure vs. Apply Raoults law and Henrys law to solve simple thermodynamicProblems. Apply simplified VLE equations to obtain data for P-XY, T-XY and X-Y diagrams. Derive and simplify equations of VLE. K (or DePriester) Chart (high T range) in American Engineering Units from Introduction to Chemical Engineering Thermodynamics (7 th ed) by Smith, J.M., Van Ness, H.C., and Abbott, M.M.It is expected that students have the ability to: Describe the behaviour of VLE and how to simplify the VLE problem. The -value is where the green line intersects the curve for propane ().
Note: z1=y1=1 (10.14) If Raoult's Law valid, Pd 1yiPiPlot Tx1y1 at P=70kPaChoose T between T1sat and T2sat , calculate P1sat and P2sat and use these to calculate x1 by the following eqn.XiKi 1 (10.13). For Raoult's Law, P xiPisat (10.2) P x1P1sat x2P2sat x1P1sat (1 x1)P2satP (P1sat P2sat )x1 P2sat note: a linear line (y=mx+c)Calculate P for a set of x1 and then calculate y1using,183.211750.888074.960.8750.748366.720.6750.569258.470.4750.331350.230.275041.98075y1P(kPa)x1TB sat liquid solution or bubblepointPb is by BUBL PC sat vapor mixtureor dewpointPd is by DEW PDEW P calculationCalculate Pd and x1, given y1 and TSo lets calculate Pd at z1=0.6 and T=75oC.This is point c in previous Px1y1 diagram. 1000 kPa and 0 oCBUBL P: Calculate and PTo calculate the T when the 1st dew (drop of liquid) appear as a result of decrease in T at constant PTo calculate the T when the last dew disappear as a result of increase in T at constant P.Let T=1 mol, so V and L are mole fractionszi Lxi Vyi zi (1V )xi Vyi (A)Substitute yi Kixi into (A)zi (1V )xi KixiV xi (1V VKi ) xi (1V (Ki 1))xiAcetonitrile(1)/Nitromethane(2)Antoine Eqn,Calculate P and y1, given a set of x1 and T=75oCThis is BUBL P calculation.XiKi 1 (10.13). For Raoults law, needs PisatTherefore requires TFor light hydrocarbon mixture where Kiis essentially function of T and P only, the valuecould be simply tabulated as in DePriester chart.Read value of K-valueat given T and Pe.g. T curve for species 2C1 and C2 are critical points for species 1 & 2Under surface issaturated-vapor (P,T,y1 surface)Top surface issaturated-liquid(P,T,x1 surface)AEDBLA givesFigure 10.2 (a)Pxy phase diagram at constant TKJIHLK givesFigure 10.2 (b)Txy phase diagram at constant PF (liquid solution)L (bubble point)W (dew point)G (Gas mixture)LV = tie lineL = bubble pointW = dew pointNote: species 1 has higher vapor pressure or lower boiling point than species 2Most chemical processes operate at this P, T rangeAzeotropex1=y1 x2=y2Liquid composition= Gas composition
Stop if this is equal or close to earlier value of T, else use this value as a new guess. Calculate ik, (note: Number of ik is equal to number of component)6. Arbitrarily pick a component, e.g. Note: z1=x1XiKi 1 (10.13), For Raoult's Law, Pb xiPisat (10.2) Pb xiPisat Pksat xi PiThe solution is not straightforward as T is unknown.BUBL T calculationSolution is through iteration,T xi Tisat2.
Finally, calculate yi using Raoults law (Use Antoine Eqn for Pisat)76.4244.221.971776.4376.4344.241.970376.
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