Citation: Georgiev, B.E.; Stratiev, D.S.; Argirov, G.S.; Nedelchev, A.; Dinkov, R.; Shishkova, I.K.; Ivanov, M.; Atanassov, K.; Ribagin, S.; Nikolov Palichev, G.; et al. Commercial Ebullated Bed Vacuum Residue Hydrocracking Performance Improvement during Processing Difficult Feeds. Appl. Sci. 2023, 13, 3755. https://doi.org/10.3390/ app13063755 Academic Editor: Michalis Konsolakis Received: 23 February 2023 Revised: 9 March 2023 Accepted: 13 March 2023 Published: 15 March 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). applied sciences Article Commercial Ebullated Bed Vacuum Residue Hydrocracking Performance Improvement during Processing Difficult Feeds Borislav Enchev Georgiev 1,2 , Dicho Stoyanov Stratiev 1,2, * , Georgy Stoilov Argirov 1 , Angel Nedelchev 1 , Rosen Dinkov 1 , Ivelina Kostova Shishkova 1 , Mihail Ivanov 1 , Krassimir Atanassov 2 , Simeon Ribagin 2,3 , Georgi Nikolov Palichev 2 , Svetoslav Nenov 4 , Sotir Sotirov 3 , Evdokia Sotirova 3 , Dimitar Pilev 4 and Danail Dichev Stratiev 2 1 LUKOIL Neftohim Burgas, 8104 Burgas, Bulgaria 2 Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Georgi Bonchev 105, 1113 Sofia, Bulgaria 3 Intelligent SystemsLaboratory, University Prof. Dr. Assen Zlatarov, Professor Yakimov 1, 8010 Burgas, Bulgaria 4 Department of Mathematics, University of Chemical Technology and Metallurgy, Kliment Ohridski 8, 1756 Sofia, Bulgaria * Correspondence: stratiev.dicho@neftochim.bg Abstract: The Urals and Siberian vacuum residues are considered difficult to process in the ebul- lated bed hydrocracking because of their increased tendency to form sediments. Their achievable conversion rate reported in the literature is 60%. Intercriteria analysis was used to assess data from a commercial vacuum residue hydrocracker during processing blends from three vacuum residues: Urals, Siberian Light, and Basra Heavy. The analysis revealed that the main contributors to conversion enhancement is hydrodemetallization (HDM) and the first reactor ΔT augmentation. The increase of HDM from 40 to 98% and the first reactor ΔT(ΔT(R1)) from 49 to 91 ◦ C were associated with a vacuum residue conversion enhancement of 62.0 to 82.7 wt.%. The developed nonlinear regression prediction of conversion from HDM and ΔT(R1) suggests a bigger influence of ΔT(R1) enhancement on conversion augmentation than the HDM increase. The intercriteria analysis evaluation revealed that the higher first reactor ΔT suppresses the sediment formation rate to a greater extent than the higher HDM. During processing Basrah Heavy vacuum residue, a reduction in hydrodeasphaltization (HDAs) from 73.6 to 55.2% and HDM from 88 to 81% was observed. It was confirmed that HDM and HDAs are interrelated. It was found that the attainment of conversion of 80 wt.% and higher during processing Urals and Siberian Light vacuum residues is possible when the HDM is about 90% and LHSV ≤ 0.19 h −1 . Keywords: vacuum residue; hydrocracking; ebullated bed; HDM; HDAs; sediment control; fouling 1. Introduction The level of heavy oil conversion is the factor that controls modern refining profitabil- ity. The ebullated bed hydrocracking and the slurry hydrocracking are the conversion technologies that can provide the highest conversion level ≥ 90 wt.% among all technolo- gies converting vacuum residue [1,2]. Currently, more than 90% of the world’s vacuum residual oils are hydrocracked using the ebullated bed hydrocracking technology [3]. After slurry hydrocracking, with 95% vacuum residue conversion achieved on a commercial scale [4], ebullated bed vacuum residue hydrocracking (EBVRHC) demonstrated com- mercially the capability of attaining 93% conversion [2]. The lowest conversion level reported for the EBVRHC is 55% [2,5]. The very large difference of almost 40% can be a result of different feed quality [6], distinct catalyst conditions [7], and various operat- ing conditions [2]. The main constraint to increasing reaction severity and consequently conversion is the sediment formation rate, which increases exponentially with reaction Appl. Sci. 2023, 13, 3755. https://doi.org/10.3390/app13063755 https://www.mdpi.com/journal/applsci