Chemical Engineering : Thermodynamics and Kinetics

At the end of this learning unit, the student is able to :

• Axis 1: AA1.1, AA1.2
• Axis 2: AA2.2, AA 2.3, AA 2.4, AA 2.5, AA 2.6, AA 2.7
• Axis 4 : AA 4.2, AA 4.3, AA 4.4

• Model a basic process in the Aspen+ simulator, choose the appropriate thermodynamic method, optimize certain process parameters and critically analyze the results.

• Explain how to determine which type of thermodynamic model should be used in a practical problem, based on the nature of the present substances and the temperature-pressure domain being considered.
• Explain the operation principle of a multistage distillation column and explain how the presence of an azeotrope can influence the purity of the distillate and of the residue.
• Explain which are the important operating parameters which influence the operation of a distillation column and how such an equipment can be controlled in practice.
• Explain the use of multistage distillation in the case of crude oil refining.  Also explain which approach is used in process simulation for this operation and which are the operating parameters enabling to control it.
• Explain the principle of liquid-liquid extraction, its usefulness in separation operations and how to choose a good extraction solvent.  Enumerate the equipment types used to implement this operation.

• Describe qualitatively the shape of (h,P) diagrams of a pure substance and give examples illustrating their usefulness in solving some practical problems encountered in the process industry.
• Define the concept of fugacity, discuss its utility and give a physical interpretation thereof.  Show how the fugacity coefficient of a gas can be computed from a measurable value, namely the compressibility factor of this gas.
• Give the shape of the variation of a real gas compressibility and justify this shape on a physical basis.
• Justify the theory of van der Waals according to which the ideal gas equation can be corrected by two parameters in order to take into account the interactions between the molecules contained in the system.  Show how these two parameters can be identified.
• Demonstrate how the vapor pressure of a liquid at a given temperature can be derived from the shape of the curve describing the variation of pressure as a function of the molar volume, as expressed by the van der Waals equation.
• Explain the concept and the usefulness of the « equilibrium ratio » K in the context of problems involving vapor and/or liquid phases at equilibrium.
• Derive expressions of the « equilibrium ratio » K in terms of fugacity coefficients and activity coefficients.
• Explain how equations of state derived from the van der Waals equation (e.g.. Soave-Redlich-Kwong or Peng-Robinson) are used in order to compute thermodynamics properties of vapor-liquid mixtures at equilibrium, in particular the equilibrium ratios K.
• Explain how correlations for the computation of liquid phase activity coefficients (e.g. Wilson, NRTL, UNIQUAC or UNIFAC) are used in order to compute thermodynamics properties of vapor-liquid mixtures at equilibrium, in particular the equilibrium ratios K, of non-ideal vapor-liquid mixtures at equilibrium.

• Explain the elements characterizing the worldwide demand for crude oil and refined products, as well as its past and future historical evolution.
• Describe the notion of « refining margin », how it is computed and the parameters that influence it.

• Description of the kinetics of complex reactions and methods for reducing the complexity of kinetic models.

• Different steps in a heterogeneous catalytic reaction, chemisorption, elementary steps in heterogeneous catalytic reactions, Hougen-Watson Langmuir-Hinshelwood and Eley-Rideal approach for deriving rate expressions based on rate-determining steps, methodologies for kinetic modeling, introduction to advanced methods.

• Effect on observed reaction rates, transfer coefficient concept, modeling of the mass and heat transfer coefficient, criteria for evaluating the importance of interfacial transfer limitations.

• Effect on observed reaction rates, porous properties of catalytic particles, continuum description of a catalytic particle and the concepts of porosity, tortuosity, and effective diffusivity, experimental methods to determine porosity and tortuosity of catalysts, types of diffusion, modeling diffusion-reaction within the catalyst and calculating concentration profiles, Thiele modulus concept and effectiveness factor, generalized Thiele modulus concept, criteria for evaluating the importance of intra-particle diffusion limitations.

• Modeling approaches.

• Different types of deactivation, catalyst poisoning and modeling approach, coke formation and modeling approaches.

• Transport phenomena, two-film diffusion-reaction model, examples of concentration profile calculations within films for simple reactions and for the general case, Hatta number concept.