a commitment to ensure high cat- alyst quality to maximise perfor- mance and reliability. The European refiner operated the DHT unit in two modes: 1 ULSD mode by processing a blend of light gasoil (75 wt%), heavy gasoil (3 wt%), vacuum gas- oil (2 wt%), and cracked gasoil (20 wt%). 2 Heating oil mode by processing a blend of light gasoil (20 wt%), heavy gasoil (45 wt%), vacuum gas- oil (15 wt%), and cracked gasoil (20 wt%). As a result, the unit was able to process a blend of light and vac- uum gasoil with coker distillate to produce two grades of final prod - uct. The unit achieved the projected cycle length while reducing catalyst expense. A summary of the feed and operating conditions is shown in Table 4 . The rejuvenated NiMo catalyst provided high HDN activity com - bined with deep HDS levels to han - dle the high nitrogen concentration in the feed blends. The primary objectives of the hydrotreater were: • To produce ULSD, targeting a product sulphur of 11 ppmw • To produce heating oil, targeting a product sulphur of 55 ppmw The rejuvenated catalyst gave this European refiner the expected per - formance while enabling substantial cost savings versus loading fresh catalyst. This unit successfully pro- duced on-specification product for both modes throughout the cycle, with Excel NiMo on par with the previous cycle loaded with fresh alternative NiMo catalyst. The nor- malised weighed average bed tem- perature (WABT) for both cycles is shown in Figure 9 . Conclusions Excel rejuvenated NiMo catalyst, as a standalone, demonstrated slightly better hydrogenation activ - ities (HDS, HDN, and HDA) than its parent fresh under high severity ULSD conditions operating with 50% of cracked feed. Rejuvenated catalyst can offer a good alterna - tive to fresh catalyst by loading it as a full reactor or as stacked beds with fresh and reducing the fill cost without affecting the unit’s
105
0.91
0.9
104.5
0.89
104
0.8
103.5
0.87
0.86
103
40
45
50
55
TOS (day)
Volume Gain : Fresh NiMo Volume Gain : Excel NiMo
Density : Fresh NiMo Density : Excel NiMo
Volume Gain : 30% Excel NiMo / 70% Fresh NiMo Volume Gain : 70% Fresh NiMo / 30% Excel CoMo Volume Gain : 70% Excel NiMo / 30% Excel CoMo
Density : 30% Excel NiMo / 70% Fresh NiMo Density : 70% Fresh NiMo / 30% Excel CoMo Density : 70% Excel NiMo / 30% Excel CoMo
Figure 6 Volume swell for all catalyst configurations
101
30% Excel NiMo / 70% Fresh NiMo 70% Fresh NiMo / 30% Excel CoMo 70% Excel NiMo / 30% Excel CoMo
Fresh NiMo Excel NiMo
100.5
100
99.5
99
40
45
50
55
TOS (day)
Figure 7 C 5 + yield for all catalyst configurations
activities and poly-aromatics hydro- genation. The feed and operating conditions were carefully evaluated to optimise catalyst system design and simultaneously meet multi- ple unit objectives. Throughout the technical evaluation, there was
Example of a commercial run Evonik provided the same Excel rejuvenated NiMo catalyst to help the refinery extend its hydropro - cessing unit cycle until the next turnaround.⁴ The catalyst was pro - posed to maximise HDS/HDN
54 PTQQ 2 2022
www.digitalrefining.com
Powered by FlippingBook