Process Modelling of Fixed Bed Units for Adsorption and Sorption-enhanced Reaction Systems = 흡착 및 흡착 부과 반응 시스템을 위한 고정층 유닛의 공정 모델링

다국어 초록 (Multilingual Abstract)

In industries, fixed bed unit operations are widespread, for example fixed bed adsorbers are used for gas separation. Similarly, catalytic reactions are also carried out in fixed bed reactors also known as packed bed reactors. The two phenomena can also be combined in a single fixed bed unit containing both adsorbent and catalyst and referred to as sorption-enhanced reaction processes (SERP). For thermodynamically limited reactions like steam methane reforming, SERP is known to improve methane conversion and hydrogen purity. As the applications of adsorption and SERP processes grow, performance evaluation of such processes becomes increasingly important. The performance of the fixed bed for only adsorption or SERP is evaluated using breakthrough curve.
Process modelling and simulation can be an efficient tool to predict the breakthrough curves and hence to evaluate the performance of fixed bed systems. A well validated process model can also be used to test the fixed bed systems under a variety of process conditions, to understand the relationship between different process variables, and to find the optimal process variables for a given system. The goals of this thesis are: (1) to discuss the fundamentals of process modelling of fixed bed systems for adsorption and SERP applications; (2) to develop a framework for simulating such process models in a user-friendly manner; (3) to demonstrate the utility of process modelling for predicting the performance of adsorption-based separation processes.
In the first chapter, the process model for fixed bed system for pure adsorption and SERP, developed from the first principles, is presented. The model has been packaged into BREAKLAB application, which offers a graphical user interface to run breakthrough simulations for multicomponent adsorption and sorption-enhanced steam methane reforming (SE-SMR) process in a user-friendly manner. First, the mathematical model for BREAKLAB has been discussed along with the different pure component and mixture isotherm models available in BREAKLAB. The use of BREAKLAB has been demonstrated by three case studies. The extension of the model to simulate pressure vacuum sing adsorption (PVSA) cycle for SE-SMR followed by process optimization was also carried out.
In the second chapter, process modelling for adsorption was integrated with molecular simulations to screen the best zeolite for acid gas (H2S, CO2) removal from the ternary mixture of H2S, CO2 and CH4. The extended dual-site Langmuir-Freundlich isotherm model was used, and the isotherm parameters were validated using the mixture isotherm data generated from grand canonical Monte Carlo (GCMC) simulation. The process optimization was carried out for validated zeolites (APC-0, APC-2, and ATV-1) using modified Skarstrom PVSA cycle. Process optimizations revealed that APC zeolites demonstrate superior performance because of simultaneous removal of H2S and CO2. Economic optimization showed that the APC-2 is the optimal zeolite for energy-efficient acid-gas removal.

목차 (Table of Contents)

• BREAKLAB: A User-friendly GUI for Adsorption and Sorption-Enhanced Steam Methane Reforming Simulation 1
• 1.1. Introduction 2
• 1.2. Isotherm Models in BREAKLAB 8
• 1.2.1. Dual-site Langmuir 8
• 1.2.2. Dual-site Langmuir-Freundlich 8
• 1.2.3. Quadratic 9
• 1.2.4. Temkin’s Approximation 9
• 1.2.5. BET 10
• 1.2.6. SE-SMR Isotherm Models for CO2 Adsorption 10
• 1.3. Mixture Isotherm Models in BREAKLAB 12
• 1.3.1. Extended Dual-site Langmuir Model (EDSL) 12
• 1.3.2. Ideal Adsorption Solution Theory (IAST) 12
• 1.4. Mathematical Model 14
• 1.4.1. Model Development 14
• 1.4.2. Steam Methane Reforming Reactions 17
• 1.4.3. Boundary Conditions 18
• 1.4.4. Numerical Solution 22
• 1.5. Case Studies 24
• 1.5.1. Case study 1: Isothermal Breakthrough Simulations 24
• 1.5.2. Case study 2: Non-isothermal Breakthrough Simulation 34
• 1.5.3. Case study 3: SE-SMR Breakthrough Simulation 39
• 1.6. SE-SMR Pressure Vacuum Swing Adsorption (PVSA) Cycle 45
• 1.7. Conclusion 51
• Multi-scale computational screening of all-silica zeolites for adsorptive separation of ternary (H2S/CO2/CH4) mixtures 53
• 2.1. Introduction 54
• 2.2. Computational Methods 58
• 2.2.1. Zeolite Structures 58
• 2.2.2. Molecular Simulation 58
• 2.2.3. Adsorption Equilibrium Model 59
• 2.2.3.1. Extended Dual-site Langmuir Freundlich (EDSLF) Model 59
• 2.2.3.2. Ideal Adsorbed Solution Theory (IAST) 60
• 2.2.4. Pressure/Vacuum Swing Adsorption (PVSA) Cycle 60
• 2.2.5. Modeling of PVSA Cycle 61
• 2.2.6. Optimization of PVSA Cycle 63
• 2.3. Results and Discussion 65
• 2.3.1. Validation of the Equilibrium Adsorption Model 65
• 2.3.2. Parameter Sensitivity Analysis using Breakthrough Simulation 71
• 2.3.3. Process-level Evaluation of the Zeolites for Acid Gas Removal 74
• 2.4. Conclusion 82
• Appendix 84
• References 107
• 요약 117