In the DHDT exchanger train investigation, CFD identified severe flow imbalance and guided corrective piping modifi - cations that restored near‑uniform distribution. The storage‑tank additive dosing study used CFD‑predicted mixing profiles to establish pump‑suction injection as the most effective and economically beneficial configuration, later validated through successful commercial demonstration. For furnace burner assessment, CFD provided detailed flame envelope and heat flux characterisation, confirming that both wall‑ and floor‑mounted burners were operating within design limits. Collectively, these applications highlight how CFD provides high‑fidelity insight into hydrodynamics, mixing, and thermal behaviour that are otherwise inaccessi - ble, enabling data‑driven solutions that reduce operational risks, improve performance, and support reliable engineering decisions in refinery environments. The authors gratefully acknowledge IOCL for allowing us to publish the present work. We also acknowledge Mr Dinesh Kumar, Mr Soumitro Majumdar, Dr Pravesh Kumar, and Dr I Devotta from IOCL R&D, as well as the IOCL refinery teams, including RHQ for their valuable contribu - tions in the different case studies described in the manuscript. References 1 Raynal, L., Augier, F., Bazer-Bachi, F., Haroun, Y., Fonte, C. (2015). CFD applied to process development in the oil and gas industry – a review. Oil & Gas Sci. and Tech. 71. https://doi.org/10.2516/ogst/2015019. 2 Jain, E., Sau, M., Buwa, V.V. (2021). Eulerian smulations of liquid dis - tribution generated by chimney and bubble cap distributors. Chem. Eng. Journal , 421, 127799. https://doi.org/10.1016/j.cej.2020.127799. 3 Patent EP3530349B1.
4 Atta, A., Roy, S., Nigam, K.D.P. Investigation of liquid maldistribution in trickle-bed reactors using porous media concept in CFD. Chem. Eng. Sci. , 62, 24, 2007, pp.7,033-7,044. https://doi.org/10.1016/j.ces.2007.07.069.
Sahithi Ravuluri is Research Manager of the process modelling depart - ment at the Research & Development Centre of Indian Oil Corporation Limited, India. She has around eight years of experience in the model development for indigenous process, process simulations, and CFD studies for refinery technologies. Ravuluri holds an MTech in chemical engineering from IIT Delhi. Email: ravuluris@indianoil.in SK Shabina is Chief Research Manager of the process modelling depart - ment at the Research and Development Centre of Indian Oil Corporation Limited, India. She has 25 years of experience in the development of proprietary models and process optimisation for refinery hydroprocess - ing technologies. Shabina holds an MTech in chemical engineering from IIT, Madras. Email: shabinask@indianoil.in Dr I R Choudhury is General Manager and head of the process model - ling and RT-technical services at the Research and Development Centre of Indian Oil Corporation Limited, India. He has more than 25 years of experience in process modelling of the downstream hydrocarbon sector, notably in FCC and hydroprocessing technologies. Choudhury holds a PhD from the University of Ghent, Belgium, and an MTech in chemical engineering from IIT, Kanpur. Email: choudhuryir@indianoil.in Sarvesh Kumar is Executive Director at the Research & Development Centre of Indian Oil Corporation Limited, India. With three decades of experience in refining, petrochemicals, and gasification, he is instrumen - tal in the development of several indigenous process technologies and their commercial deployment. Kumar holds an MTech in chemical engi - neering from IIT Kanpur. He has numerous patents and awards. Email: kumarsarvesh@indianoil.in
Technology in Action
reactor. What makes iron uniquely problematic is that much of it arrives in soluble organic forms, like iron naphthenates and iron carboxylates, which pass directly through conven - tional inert filtration. It is this soluble iron that has the potential to cause real damage. Once inside the reactor, elevated temperatures exceeding 300°C can allow soluble iron to react with the H 2S produced by hydrotreating reactions and precipitate as iron sulphide (FeS). Since this forms where H2S is pro - duced, it can drive deposition in the catalyst bed, leading to crust layer development and pressure drop rise. Active filtration: A catalytic approach ActiPhase technology, developed by Crystaphase, helps tackle precipitated-iron fouling by introducing catalytic activity into the top of the reactor. That catalytic zone induces the precipitation reaction above the main catalyst, giving iron the opportunity to deposit in the filtration media rather than in the bed below. This is achieved through the combination of a reticulated
Soluble iron in hydroprocessing: The case for active filtration
The challenge Iron compounds remain a leading source of fouling in hydro - processing reactors with the potential to cause significant performance issues. They can drive unplanned shutdowns, shorten cycles, and erode profitability. Yet, the mechanisms by which iron threatens reactor performance are frequently misunderstood, leading to mitigation strategies that can fall short. Conventional approaches, such as feed filters and inert grading materials, address only part of this problem. Iron reaches the reactor by two primary routes: iron in the feed itself and corrosion-derived iron generated upstream. Corrosion-derived iron can come from upstream equip - ment, where naphthenic acids and sulphur compounds attack carbon steel piping, releasing iron into the feed before it ever reaches the reactor. As little as 1 ppm of iron deposited in the bed can cause major issues in a fixed-bed
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