Catalysis 2025 Issue

A Louise Jivan Shah, Senior R&D Manager | Mechanical Concepts, Topsoe, ljsh@topsoe.com Topsoe recognises the importance of CFD in the design, development, and troubleshooting of our reactors, and we have successfully integrated it into our workflows from an early stage. Despite the challenges associated with multiphase models in CFD, these limitations have been addressed by validating our CFD models for critical assumptions using in-house measurements and literature information. This validation process ensures that our simulations closely rep - resent the real-world behaviour of our reactors, giving us confidence in the results. Thanks to our in-house 2,000+ central processing unit (CPU) cores high-performance com - puting cluster for running these computationally demand - ing CFD simulations. One of the major benefits we have experienced is the ability of CFD to provide meaningful insights and informa - tion that are difficult to obtain through plant-scale mea - surements. Troubleshooting in hydroprocessing reactors often involves identifying the root cause of observed devia - tions, such as temperature radials in the reactor beds. With CFD, we have been able to strengthen our hypotheses by analysing the impact of different design and process devia - tions on the observed deviations. For instance, when we observed a temperature radial in our reactor, we utilised CFD to understand how various fac - tors contributed to the observed deviations. These included design deviations (for example, as-intended vs as-built) and process deviations (for example, actual operating vs design-basis conditions). By simulating different scenarios and analysing the results, we gained a better understand - ing of the underlying causes and were able to develop tar - geted solutions. Overall, the implementation of CFD for hydroprocess - ing reactor troubleshooting has been highly beneficial for Topsoe. It has allowed us to address issues more effectively, improve reactor performance, and optimise our processes. The insights and information generated through CFD have proven invaluable in enhancing our understanding and decision-making capabilities. Q To what extent is pretreatment needed to protect hydrotreaters/hydrocrackers from impurities when upgrad- ing WPO to petrochemical feedstocks? A Scott Sayles, Manager, Renewable Fuels and Alternate Feeds, Becht, ssayles@becht.com Waste plastic oil (WPO) has potential impurities that cause catalyst deactivation. The types of impurities depend on the plastic type being fed to the liquefaction device. Typical feed contaminants are nitrogen, oxygen, olefins, phospho - rus, silicon, and chlorides. For example, polyvinyl chloride (PVC) has the most difficult composition, mainly due to the chloride concentration and some metal stabilisers, while polypropylene has the least. The waste plastic received is a mixture of all plastic types. Some sorting is used to remove the hardest-to-process plastics, but the resulting feed is typically a mix of plastic types.

the catalyst bed is fluidised by the upward flow of liquid feed, gas, and recycle liquid. By analysing catalyst, oil, and gas residence times and mixing, CFD provides critical data for evaluating and quantifying the effectiveness of vari - ous design configurations. This facilitates targeted design modifications to resolve maldistribution and improve over - all reactor performance. In troubleshooting scenarios, such as operational upsets or dynamic process changes, CFD offers a powerful tool for analysing time-dependent behaviours. Breaking the timeline into discrete periods and simulating each phase provides insights into the causes of process disruptions and supports the development of effective solutions. CFD’s utility extends beyond reactors to associated systems. For example, it has been used to address flow distribution issues in complex geometries like elbows and tees in coke drum dual inlet piping systems, where design adjustments, such as adding wedges, successfully bal - ance vapour and liquid flow rates to reduce thermal and mechanical stresses. Similarly, CFD has been applied to optimise steam distribution in hydrocarbon outlet headers of proprietary Catofin reactors, minimising coke formation and damage to liners. Additionally, in high-velocity envi - ronments like waste heat boilers, CFD accurately predicts erosion rates and identifies critical failure zones, enabling targeted design enhancements and improved inspection protocols. CFD has also addressed thermal management chal - lenges, such as optimising heat transfer in storage tanks. Simulations can lead to adjustments like closer steam coil spacing in molten sulphur tanks, which maintain wall tem - peratures above the acid dew point, preventing corrosion and improving system reliability. Overall, CFD has consistently demonstrated its predictive power by validating design changes, reducing downtime, and ensuring long-term equipment integrity. Its role in trou - bleshooting and optimisation underscores its importance in enhancing process safety and performance in hydropro - cessing reactors and their associated systems. A Rainer Rakoczy, Technical Advisor, Fuels, Clariant, rainer.rakoczy@clariant.com The role of numerical methods for the simulation of fluid flows has become key for understanding and optimisation in uncountable areas in technology and engineering. Fixed catalyst bed hydrogenation calls beside an appropriate catalyst solution for the optimum dispersion of the desired feed and the applied hydrogen. The design of reactor dimensions, grading, and internals such as flow distributors or quench lines needs immense support from CFD, espe - cially on the process engineering side. As a catalyst vendor, the shape of the applied materials can be key. Therefore, Clariant started to look into optimis - ing shapes as well. Some decades ago, for some hydro - processing applications, a unique computer design shape (CDS) was developed and commercialised in several prod - uct series as CDS material, and the advantages, especially from the macroscopic surface area, are very much enjoyed by the applicants.