Multiscale CFD modelling and analysis of TBR behavior for an HDS process: Deviations from ideal behaviors

Abstract For the hydrotreatment process of petroleum cuts, there is a great diversity and level of Trickle Bed Reactors (TBR) models, in which it is very common to use important simplifications, such as the consideration of plug flow; these simplifications restrict the analysis of the multiphysics and multiscale nature of the phenomena that take place in such systems. The analysis of the phenomena that take place at different scales in the TBRs is very scarce; moreover, the qualitative and quantitative determination of the information that passes from one to another scale and its influence on the mass transport nature in these systems is even more difficult to find. With the purpose of analyzing the multiphysic and multiscale nature of a reactor for an HDS process, three Computational Fluid Dynamics (CFD) models were studied at three different scales, corresponding to: (i) Heterogeneous micropores model (HMM) for a particle with explicit representation of the internal surface microstructure of the catalyst, (ii) Pseudohomogeneous catalyst particle model (PCM), and (iii) Reactor scale model (RSM). The objective sought is to establish the validity of some of the assumptions commonly made in the simulation of these types of reactors and develop an analysis to determine the importance of establishing bridges of information between the phenomena that take place at different scales. The results show that despite the small dimensions of the reactor, the plug flow assumptions might not be valid, due to the presence of strong radial gradients. It was also determined that the models that do not take into account the communication between scales (catalysts to reactor scale) differ substantially from those that do, which can be verified by the differences found for the effectiveness factors, of around 35%.