## 4 Discussion
The ICrA evaluation results as \(\upmu\) and \(\upupsilon\) values of the different hydrocracking process variables is presented in Tables 3 and 4. One can see from the data in Tables 3 and 4 that the vacuum residue conversion has a statistically meaningful positive relationship with the reactor temperatures, HDM, and the first reactor \(\Delta\)T. The first reactor \(\Delta\)T also exhibits a statistically meaningful negative relationship with the ATB sediment content and a statistically meaningful positive relationship with HDM. The second reactor \(\Delta\)T does not display any statistically meaningful relation to either HDM or ATB sediment content. These findings imply that the activity of the catalyst in the first reactor affects to a greater extent both HDM and sediment formation rate than the activity in the second reactor. Therefore, the separate addition of the fresh catalyst in both reactors instead of fresh catalyst addition only in the second reactor and the addition of equilibrium catalyst taken from the second reactor in the first reactor, a practice employed until this study, has allowed to improve both total HDM extent and reduce sediment formation rate. \begin{table}
\begin{tabular}{l c c c c} \hline \hline \multicolumn{1}{c}{**Period of Time**} & \multicolumn{1}{c}{**Between 17 May 2022 and 15 August 2022**} & \multicolumn{1}{c}{**Between 15 October 2022 and 28 November 2022**} \\ \hline Performance indicators & 17 May 2022 & 15 August 2022 & 15 October 2022 & 27 November 2022 \\ Net conversion, wt.\% & 67.0 & 76.1 & 79.2 & 82.7 \\ WABT, \({}^{\circ}\)C & 418.5 & 429.5 & 430 & 431 \\ LHSV, h-1 & 0.18 & 0.19 & 0.18 & 0.17 \\ ATB, sediment content, wt.\% & 0.35 & 0.30 & 0.24 & 0.12 \\ Fouling rate & Unacceptably high & acceptable & acceptable & acceptable \\ HDM, \% & 58.2 & 85.7 & 87.7 & 97.9 \\ AT R-1001 & 58 & 77 & 86 & 84 \\ Saturates in hydrocracked vacuum & 22.4 & 20.8 & 19.4 & 17.4 \\ residue, wt.\% & & & & \\ C7-asphaltenes in hydrocracked & & & & \\ Vacuum residue, wt.\% & & & & \\ C5-asphaltenes in hydrocracked & & & & \\ vacuum residue, wt.\% & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Main performance indicators of the commercial ebullated bed vacuum residue hydrocracker during the periods when 100% Urals and Siberian Light vacuum residues were processed. The activity of the catalyst in the first reactor seems to have a considerable impact on both HDM and sediment control. The lower sediment formation rate was a result of the higher equilibrium activity of the catalyst in the first reactor, which allowed reaction temperature enhancement and consequently conversion augmentation. An interesting fact observed during the processing of Basrah Heavy crude oils is the lower registered hydrodeasphaltization extent, as shown in Figure 13. The data in Table 3 also suggests that the processing of Basrah Heavy crude oil has a negative impact on HDM extent (\(\mu\) = 0.17). However, \(\
u\)-value of Basrah Heavy (Table 4) of 0.19 suggests a very big uncertainty in this evaluation, and therefore it cannot be confidentially considered that the processing of Basrah Heavy vacuum residue definitely affects negatively HDM. Nevertheless, if one takes a look at the data in Figure 5, he will see that Basrah Heavy has been processed in the period 16 August 2022-10 October 2022, and the data in Figure 8 shows that HDM falls from 88% down to 81% in the period 16 August 2022-19 September 2022. Moreover, during the processing of Basrah Heavy, the HDAs (C\({}_{5}\)) fall by 10% and the HDAs (C\({}_{7}\)) fall by 20% (see Figure 13), and [PERSON] et al. [43] and [PERSON] et al. [44] report that the HDM and hydrodeasphaltization (HDAs) are linearly related. This data suggests some negative effects of the processing of Basrah Heavy vacuum residue on