# Revamping Fluid Catalytic Cracking Unit, and Optimizing Catalyst to Process Heavier Feeds
## 4 Discussion
### Performance of the FCC Unit before and after the Revamp  
By processing the data from the commercial LNB FCCU after the revamp, the variation in the content of H-Oil HAGO, LVGO, and HVGO in the H-Oil VGO blend was as follows:  
17.8 wt.% \(\leq\) HAGO \(\leq\) 33.2 wt.%; 19.7 wt.% \(\leq\) LVGO \(\leq\) 37.5 wt.%; 36.1 wt.% \(\leq\) LVGO \(\leq\) 57.2 wt.%; and the H-Oil VGO blend content in the FCC feed varied between 15.7 wt.% and 34.5 wt.%. The following multiple regression was developed:  
\[ \begin{split}\text{LNB FCCU conversion }=8.8+0.1212\times\text{Riser Temperature}\\ +0.5873\times\text{Catalyst to oil ratio }\left(\frac{\text{kg}}{\text{kg}} \right)-0.0756\times\text{Content of HAGO in FCC feed, \%}\\ -0.2215\times\text{Content of LVGO in FCC feed, \%}\\ -0.1093\times\text{Content of HVGO in FCC feed, \%}\end{split}  \tag{1}\]  
Figure 5 shows the parity graph of the estimated versus observed conversion. This data shows a very good agreement between observed conversion and that predicted by Equation (1), keeping in mind that this is commercial data, where the noise of the data is relatively high. Equation (1) indicates that the commercial FCCU data confirms the H-Oil gas oil reactivity data (see the data in Table 3) obtained in the laboratory ACE unit, showing that the least reactive H-Oil gas oil is LVGO. The data in Table 3, and that shown in Figure 1, suggest that the most appropriate catalyst to process the heavier gas oils from H-Oil is that possessing both the highest activity and the lowest coke selectivity. Figure 5: Parity graph of conversion estimated by Equation (1) versus observed conversion at the LNB FCCU. The data in Table 4 shows that the H-Oil VGO suppresses hydrogenation in the FCC feed hydrotreater (pretreater = FCCPT). This is evident from the lower density reduction in the hydrotreated VGO (9 kg/m\({}^{3}\) at 8.9% H-Oil VGO content in the FCCPT feed) than that during processing only straight-run VGO (21 kg/m\({}^{3}\) at zero content of H-Oil VGO in the FCCPT feed). The data in Table 4 also indicate that the quality and quantity of the H-Oil VGO in the FCC feed for the three studied cases are different. The highest share in the FCC feed and the lowest Kw-characterization factor of the H-Oil VGO was observed for Case: 11-13 September 2022 (after FCC revamp). The FCC feed for this case was also characterized by the lowest Kw-characterization factor. This means that the feed for this case is the most refractory among the studied three cases. Considering the relation of FCC feed containing H-Oil VGO established in our earlier research [28] and shown in Equation (2):  
\[Conversion=0.1787\times e^{0.5013 Kw}\ \ \mathrm{R}=0.99,\ \mathrm{av.\ error}=1.7\% \tag{2}\]  
The estimated conversions which reflect FCC feed reactivity are as follows:  
* Case: 10 September -11 September 2018 (before revamp) = 71.2 wt.% estimated conversion;
* Case: 11 September -13 September 2022 (after revamp) = 67.3 wt.% estimated conversion;
* Case 2.10-3.10.2022 (after revamp) = 70.4 wt.% estimated conversion. These data suggest that Case: 11 September -13 September 2022 (after revamp) has the lowest reactivity feed, while the other two cases have the same reactivity feeds (the difference between estimated conversions is 1.1%, which is lower than the error of prediction of Equation (2)). Despite the poor quality of the feed for the Case: 11 September -13 September 2022 (after the revamp), it demonstrated the same conversion level as that observed in Case: 10 September -11 September 2018 (before revamp). Comparing the cases which have the same quality of FCC feed, Case: 10 September -11 September 2018 (before the revamp) and Case 2.10-3.10.2022 (after the revamp), one can see that the case after the revamp registered a 2.5 wt.% higher conversion. Another big advantage of the revamp is the higher octane number of the gasoline (+0.8 points for both RON and MON).