Process Engineering for Pollution Control and Waste Minimization_6

Trên tất cả trong số này, hầu hết của các chất gây ô nhiễm hữu cơ ngoan cố thường có tính hòa tan tối thiểu trong giai đoạn dịch, nơi mà các vi sinh vật được lưu trữ và được coi là tích cực nhất. Những tiến bộ gần đây trong biocatalysis đã chứng minh rằng nó là khả thi để thực hiện
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Process Engineering for Pollution Control and Waste Minimization_6 ƒ2 ∆G = RT ln (real gas) (78) ƒ1 Here, ƒ1 is the fugacity at pressure P1. The fugacity may be considered as an adjusted pressure. It is defined so as to coincide with the pressure at low densities: lim ƒ =1 (79) P→0 P The ratio of fugacity to pressure is called the fugacity coefficient, φ. Thus, the previous equation may be written ƒ lim ϕ≡ ⇒ ϕ=1 (80) P→0 P 5.4 Chemical Potential Consider a solution consisting of n species A, B, . . . . The Gibbs free energy of the solution is given by n ∑ Nkµk G= (81) k=1 where µk is the chemical potential of species k, defined by  ∂G  µk =   (82)  ∂Nk T,P,Nj≠k 5.5 Fugacity and Activity The chemical potential is generally a function of temperature, pressure, and composition. It is common practice to write µA = µ˚A(T) + RT ln aA (83) where µ˚A(T) is the standard chemical potential and aA is the activity of species A. The activity is defined as the ratio of the fugacity ƒA to a standard-state fugacity ƒ˚A: ƒA aA = (84) ƒ ˚A Activities and standard states are discussed in greater detail in many texts on chemical thermodynamics (11,12). Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved. 5.6 Phase Equilibrium Consider a multicomponent system that separates into two or more phases (denoted I, II, . . .). The criteria for phase equilibrium are TI = TII = . . . (thermal equilibrium) (85) PI = PII = . . . (mechanical equilibrium) (86) (µA)I = (µA)II = . . . (equilibrium for species A) (87) (µB)I = (µB)II = . . . (equilibrium for species B) (88) . . . 5.7 Reaction Equilibrium Consider a reaction aA + bB + . . . = . . . + xX + zZ which, as before, can be expressed in the shorthand notation n ∑ νkIk 0= k=1 The criterion for chemical reaction equilibrium is n ∑ νkµk ∆G = =0 (89) k=1 Reaction equilibrium may also be expressed in terms of the standard Gibbs free-energy change: ∆G0 = RT ln Ka (90) Here, Ka is the equilibrium constant, defined by n ∏ akν Ka = (91) k k=1 6 ENGINEERING FLUID MECHANICS Fluid mechanics deals with the flow of liquids and gases. For most engineering applications, a macroscopic approach is usually taken. Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved. 6.1 Engineering Bernoulli Equation Most enginee ...