Consider a sub-cooled binary liquid that is 40 mol% ethanol.What is its bubble point?What is the composition of the first bubble? 2. Figure 2-3Temperature-composition diagram for ethanol-water bubble point dew point 圎,initial yE,initial boilingrange 1.
Wankat(ISBN: 0131382276) Copyright 2012 Pearson Education, Inc. yA A subcooled liquid feed of composition zA, heated to temperature TA, will separate spontaneously into 2 phases, of composition xA and yA TA xA yA zA From Separation Process Engineering, Third Edition by Phillip C. Figure 2-3Temperature-composition diagram for ethanol-water superheated vapor subcooled liquid 2-phaseregion saturated vapor line saturated liquid line 2 graphs in one: T vs. Thermodynamic calculations using K-values Dew point Procedure: a) Select T b) Ki(T) c)Ĭampuran terdiri n-hexane (0.15), n-heptane (0.20), n-octane (0.30) dan n-nonane (0.Goal 1: Design a flash drum How big should the drum be? What height should the nozzle be? What T and P should the drum be? What T and P should the feed be? Vapor-liquid equilibrium (VLE) Consider a binary (i.e., 2-component) system with 2-phases: Tvap, Pvap yA, yB Tliq, Pliq xA, xB What do we know? yA + yB = 1 xA + xB = 1 yA xAĪt equilibrium:Tvap = Tliq Pvap = Pliq Gibbs Phase Rule: degrees of freedom = # components (C) - # phases (P) + 2 For a binary, 2-phase system: 2 2 + 2 = 2 We can specify only 2 intensive variables (all others are fixed, by VLE) Specify P and T From Separation Process Engineering, Third Edition by Phillip C. Y A / K A (T ) + y B / K B (T ) = 1 - Thus as we decrease the temperature we put new K-values the above equation until this condition is met Y A + y B = 1 - Consider the process in the figure: we start with a mixture of composition 1 and temperature T1 and start decreasing the temperature - As we decrease the temperature we are going to reach a point where the first drop of liquid forms - The liquid in the droplet obeys: Thermodynamic calculations using K-values Dew point Thermodynamic calculations using K-values Bubble point Procedure: a) Select T b) Ki(T) c)Į) Adjusting T g) Final composition can be corrected usingĬampuran pada tekanan 300 kPa terdiri dari: 50 kmol Heptane 30 kmol Octane 20 kmol Nonane Tentukan bubble point! Gunakan de Priester Chart. K A (T ) x A + K B (T ) x B = 1 - Thus as we increase the temperature we put new K-values in the above equation until this condition is met As we increase the temperature we are going to reach a point where the first bubble forms - The vapour in this bubble obeys: X A + x B = 1 - Consider the process in the figure: we start with a mixture of composition 1 and temperature T1 and start increasing the temperature Thermodynamic calculations using K-values Bubble point - Model system: binary mixture A, B X* Easy for 2 component system, if T-x-y diagram is available (remember the lever rule?) What about the multi-component system? Thermodynamic calculations using K-values P Grafik menunjukkan hubungan nilai K untuk suatu komponen dengan suhu dan tekananĬampuran terdiri n-hexane, n-heptane, noctane dan n-nonane pada suhu 40C dan 500 kPaīubble point is the condition that the first bubble formed during liquid mixture boiled Dew point is the condition that the first drop formed during vapor mixture cooled Persamaan Antoine dan koefisien dinyatakan dalam beberapa bentuk:ĭata koefisien Antoine dapat dilihat di Chemical Engineering Vol 6 Persamaan Antoine memberikan hubungan tekanan uap murni (P atau VP) suatu senyawa/komponen dengan suhu. K i = Pi / P Relative volatility for ideal gas/ideal solution system: s Pi = yi P K-value for ideal gas/ideal solution system: s Pi is the partial pressure of component i
Thermodynamic data for mixtures: Simplified models V Ki = yi/xi correlated empirically or theoretically in terms of temperature pressure and composition The ratio of two K-values, or relative volatility, indicates the relative ease or difficulty of separating components i and j Thermodynamic considerations and phase equilibria: multicomponent mixtures For multicomponent mixtures simple graphical representations of vapour-liquid equilibria data do not exist Most often such data (including binary systems) is represented in terms of K values defined as: Penya enyajian jian Data Data Keset Kesetimbang imbangan an (presenting (presenting equilibrium data)
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