Process Simulation for the Design and Scale Up of Heterogeneous Catalytic Process: Kinetic Modelling Issues

Abstract

Abstract:Process simulation represents an important tool for plant design and optimization, either applied to well established or to newly developed processes. Suitable thermodynamic packages should be selected in order to properly describe the behavior of reactors and unit operations and to precisely define phase equilibria. Moreover, a detailed and representative kinetic scheme should be available to predict correctly the dependence of the process on its main variables. This review points out some models and methods for kinetic analysis specifically applied to the simulation of catalytic processes, as a basis for process design and optimization. Attention is paid also to microkinetic modelling and to the methods based on first principles, to elucidate mechanisms and independently calculate thermodynamic and kinetic parameters. Different case studies support the discussion. At first, we have selected two basic examples from the industrial chemistry practice, e.g., ammonia and methanol synthesis, which may be described through a relatively simple reaction pathway and the relative available kinetic scheme. Then, a more complex reaction network is deeply discussed to define the conversion of bioethanol into syngas/hydrogen or into building blocks, such as ethylene. In this case, lumped kinetic schemes completely fail the description of process behavior. Thus, in this case, more detailed-e.g., microkinetic-schemes should be available to implement into the simulator. However, the correct definition of all the kinetic data when complex microkinetic mechanisms are used, often leads to unreliable, highly correlated parameters. In such cases, greater effort to independently estimate some relevant kinetic/thermodynamic data through Density Functional Theory (DFT)/ab initio methods may be helpful to improve process description.

Performance Study on Methanol Steam Reforming Rib Micro-Reactor with Waste Heat Recovery

“…The characteristics of the MSR are studied when the inlet reactant velocity increases from 0.01 m/s to 0.3 m/s, at inlet exhaust velocity of 1.1 m/s, inlet exhaust temperature of 673 K, inlet reactant temperature of 453 K. As the inlet reactant velocity increases, the heat absorption by the reactant increases, resulting in a decrease of the temperature. The change laws agree with the literatures [37,38], but the increasing range is larger, because the temperature is higher than literature one. As shown in Figure 7a, the axial temperature increases gradually along the axis and decreases with the reactant inlet velocity.…”

How sensitive is a dynamic ammonia synthesis process? Global sensitivity analysis of a dynamic Haber-Bosch process (for flexible seasonal energy storage)

“…This entering gas flow provides a limitation to the valid range of the reactor model when going below the 50% load (to 10%-20%). Below this load, the reactor model deviates from the experimental results [22], where the plant performance prediction is not reliable as discussed in Tripodi et al [50]. Therefore, the additional control In our dynamic model, we assume that the operating pressure of 100 bar is kept constant at all instants to avoid the limit cycle behavior.…”

Conceptual Design and Energy Analysis of Integrated Combined Cycle Gasification System

“…The flow rate of hydrogen is 16,200.38 kg/h which reacts with 61,627 kg/h N 2 (H2:N2, 1:3.804) at 271.11 • C in an equilibrium reaction producing 32,468.66 kg/h CH 4 at product yield of 24% with nitrogen steam (HICH 4 ) [32,33].…”