Computational Fluid Dynamics Study of a Pharmaceutical Full-Scale Hydrogenation Reactor

Abstract

The pharmaceutical industry has been quite successful in developing new hydrogenation processes, and the chemistry of hydrogenation is currently well understood. However, it is a complex process to scale and optimize due to its high exothermicity, use of expensive catalysts and solvents, and its mass transfer requirements. Therefore, the aim of this work is to develop a CFD model to be able to describe the mass transfer, hydrodynamics, and mixing with respect to changes in rotational speed for a full-scale pharmaceutical hydrogenation reactor. In the first stage, a simple CFD model is used to predict the development of the surface vortex, and it is validated against literature data. In the second stage, the CFD model is tested on a full-scale configuration equipped with a Rushton turbine and a bottom kicker to study the formation of the surface vortex. Simulation results show the ability to predict the development of the surface vortex. These results are used to estimate the liquid height and mixing time as a function of several rotational speeds, allowing us to propose novel process correlations for this particular configuration. Although modelling the complete hydrogenation process would be challenging, this work is seen as a first step towards developing models that demonstrate the use of CFD at such large reactor scales.

Advancing Nitrobenzene Hydrogenation Process Understanding: A Multiscale Modeling Approach using Industrial Pharmaceutical Production Data

“…Due to the limited variation in the available data, it is important that only the most relevant phenomena are included in the model and that the added value of accounting for an additional phenomenon outweighs the incorporation of additional parameters in the model, which can only be estimated if sufficient corresponding variation is present in the observations. The phases are considered to be uniformly mixed at the commercial operating conditions, consistent with the work of Fernandes del Pozo et al, 15 in which a CFD model was developed for these specific reactors.…”

“…The reaction is performed in two 2500 L stirred tank reactors, R1 and R2, equipped with a Rushton turbine for mechanical stirring, , which are identical in geometry and design. However, reactor R1 is constructed from Hastelloy C22 and reactor R2 from stainless steel 316, which impacts the heat transfer.…”

“…The phases are considered to be uniformly mixed at the commercial operating conditions, consistent with the work of Fernandes del Pozo et al, in which a CFD model was developed for these specific reactors.…”

“…The heat transfer area depends on the wetted surface area by the liquid, which is related to the reactor liquid level and therefore changes in the agitation. A CFD model specifically developed for these reactors, detailed in the work of Fernandes del Pozo et al, 15 was used to estimate the wetted surface area under varying agitation conditions. The variation is not constant because vortex formation is not present at the lower stirring speeds, and this increases the area with agitation.…”