## 5 Conclusions  
The number of papers published in referenced journals dealing with commercial vacuum residue hydrocracking data is enormously small relative to that related to laboratory hydrocracking experiments. Therefore, there is a need for more publications discussing commercial vacuum residue hydrocracking data to appear in the referenced journals to make the academic audience familiar with the real-world vacuum residue hydrocracking issues.  
The earlier commercial experience with the processing of higher saturate content vacuum residues derived from Urals and Siberian Light crude oils during the employment of cascade mode of fresh catalyst addition in the ebullated bed hydrocracking and running at LHSV of 0.25 h\({}^{-1}\) showed that their conversion was about 60%. The replacement of the cascade by the parallel mode of fresh catalyst addition, where 60-70% of the fresh catalyst is inserted in the first reactor and 30-40% in the second reactor, allowed achievement of 83% conversion during operation at a LHSV of 0.17 h\({}^{-1}\).  
The use of intercriteria analysis evaluation of the commercial ebullated bed vacuum residue hydrocracker data enabled identification of the factors influencing conversion improvement. They are itemized below:  
* HDM extent enhancement
* First reactor \(\Delta\)T increase
* Higher metal removal from the first reactor  
The results of this study suggest that the higher metal removal and higher catalyst activity in the first reactor as a consequence of the higher portion of fresh catalyst added to the first reactor contribute to the suppression of the sediment formation rate during the processing of higher saturate content Urals and Siberian light vacuum residues. This underlines the significance of the activity and metal removal capacity of the catalyst in the first reactor for the overall performance of the commercial hydrocracker.  
It was observed a decreased HDM extent during the processing of Basrah Heavy vacuum residue. The relation between HDM and HDAs observed at laboratory hydrocracking experiments was confirmed with the commercial data generated in this study.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app13063755/s1](https://www.mdpi.com/article/10.3390/app13063755/s1)]([https://www.mdpi.com/article/10.3390/app13063755/s1](https://www.mdpi.com/article/10.3390/app13063755/s1)), Table S1: Properties of crude oils under study; Table S2: Different variables characterizing the ebullated bed vacuum residue hydrocracker performance to be evaluated by ICrA.; Table S3: Ebulated bed vacuum residue hydrocracker data for LHSV, reaction temperature (WABT), and net convesion.  
Conceptualization, D.S.S. and A.N.; methodology, R.D. and I.K.S.; software, S.R., S.N. and D.D.S.; validation, D.P., S.S. and E.S.; formal analysis, M.I.; investigation, G.N.P., G.S.A., M.I. and B.E.G.; resources, K.A.; data curation, S.N. and D.P.; writing--original draft preparation, D.S.S.; writing--review and editing, D.S.S.; visualization, G.S.A.; supervision, K.A. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The authors [PERSON], and [PERSON] acknowledge the support from the Bulgarian National Science Fund under Grant Ref. No. KP-06-N22-1/2018 \"Theoretical research and applications of InterCriteria Analysis\".  
The authors declare no conflict of interest.