雙成分氣液相平衡觀念介紹課件

1、Introduction to Chemical Engineering ThermodynamicsJi-Sheng ChangChapter 10-1The concepts and laws forbinary vapor-liquid equilibrium problems1Equilibrium between phasesThe nature of equilibriumEquilibrium:the all values of the thermodynamic properties of the system had been fixed.By macroscopic vie

2、w:static equilibriumBy microscopic view:dynamic equilibrium平衡的本質(zhì)在平衡時，熱力變數(shù)的數(shù)值為定值巨觀觀點：靜態(tài)平衡微觀觀點：動態(tài)平衡2The phase ruleThe size of systemThe size of the system, we have to given an extensive property of the system.Given each one of extensive propertyVtotal, Htotal, Utotal, . , or total mass系統(tǒng)的大小系統(tǒng)大小由一個示量性質(zhì)

3、界定之3The phase ruleThe phase ruleThe Gibbs phase rule, tell us that how many properties or variables can to fix the system?For a phases and N components system at equilibriumF = 2 - + N相律Gibbs phase rule提供界定系統(tǒng)之自由度的計算式自由度隨系統(tǒng)之總成份數(shù)與總平衡相數(shù)而變4The phase ruleThe phase ruleThe Duhems theorem, tell us that how

4、 many variables can given the information of the size distribution between equilibrium phases?F = 2F: the degrees of freedom of a system.相律Duhems theorem 提供平衡相間確知相分佈未的自由度自由度為定值等於 25Simple models for VLESimple models for vapor/liquid equilibriumDaltons law; ideal solution behavior for gas phase Pi =

5、yi PRaoults law; ideal solution behavior for liquid phase Pi = xi PisatHenrys law; ideal solution behavior for liquid phase Pi = xi Hi,j氣液平衡有關之模式道爾吞分壓定律勞特定律拉午耳定律亨利定律6Simple models for VLESimple models for vapor/liquid equilibriumIdeal gas behaviorPV=RT; For pure components vapor/liquid system, at eq

6、uilibrium, P = Pisat氣液平衡有關之模式理想氣體純成份氣液平衡系統(tǒng)，系統(tǒng)壓力為成分飽和蒸汽壓7Thermodynamic variablesThe variablesT: TemperatureP: Pressure: chemical potential f: fugacityPi: partial pressure the suffix and superscriptV: vapor phase; L: liquid phase; 1,2: species變數(shù)/熱力性質(zhì)8VLE problemsFor a binary VLE problemsVariablesT, P,

7、 x1, x2, y1, y2;( P1sat, P2sat)The degrees of freedom from the Gibbs phase ruleF = 2 -2 + 2 = 2雙成分氣液平衡問題未知變數(shù)有 六個因勞特定律之適用增加二個變數(shù)計算得雙成份氣液平衡系統(tǒng)之自由度為 29Independent equations(1)Independent equations as from the state at equilibrium,TV = TLPV = PLP1V=P1L; (1V=1L; f1V=f1L)P2V=P2L; (2V=2L; f2V=f2L)獨立方程式溫度壓力成份

8、 1 的分壓成份 2 的分壓10Independent equations(2)Other equationsThe physical lawThe other thermodynamic modelsAntoine equation獨立方程式物理定律與定義定律其他之熱力學模式安東尼方程式11Kind of VLE calculationThe cases of binary VLE problemsBubble pressure calculationDew pressure calculationBubble temperature calculationDew temperature c

9、alculationCompositions calculationStates property calculation雙成分氣液平衡計算類型泡點壓力計算霧點壓力計算泡點溫度計算霧點溫度計算組成計算狀態(tài)性質(zhì)計算12Vapor-liquid equilibriumEquation of vapor/liquid equilibriumWhen the liquid phase is an ideal solution, when the gas phase is an ideal solution, and which of each species in vapor phase is an

10、ideal gas behavior.The partial pressure of species could be given by Daltons law Pi = yi P and Raoults law Pi = xi Pisat yi P = xi Pisat 氣液平衡方程式成份之蒸氣遵守理想氣體行為氣相為理想氣體理想混合液相為理想溶液13Vapor-liquid equilibriumEquation of vapor/liquid equilibriumWhen the liquid phase is not an ideal solution Modified by Raou

11、lts lawyi P = i xi Pisat ;by氣液平衡方程式若液相混合物不是理想溶液行為用活性係數(shù)修正勞特定律14Vapor-liquid equilibriumEquation of vapor/liquid equilibriumWhen the gas phase is not an ideal solution Additional modified of Daltons lawi yi P = i xi Pisat氣液平衡方程式若氣相不是理想氣體混合用逸壓係數(shù)修正道爾吞分壓定律15Vapor-liquid equilibriumEquation of vapor/liquid equilibriumWhen each of species in vapor phase is a real gas, using the fugacity of pure species thermodynamic properties replaced the satura