months of the year when the unit is air-blower (coke-burn) constrained, the maximum feed rate cannot be sustained. Under these conditions, the new feed nozzles enable a 2.5% higher feed rate at constant conversion • Increased conversion at maximum feed rate: during the remaining six months, the new feed nozzles provide 0.19 vol% more conversion at maximum feed rate • Dry gas reduction of 15% • Average riser temperature reduction of 15°F (8.3°C). FCC pretreatment – FCC optimisation scenario Upgrading feed nozzle technology can have implications for upstream units such as the FCC pretreatment (FCC-PT) unit. The optimisation of the FCC unit, along with the FCC-PT unit, is an important undertaking that should be evaluated to bring the most value to the site. FCC units that crack partially or fully hydroprocessed feedstocks have advantages with respect to crude and
FCC performance under SOR and EOR FCC-PT conditions
FCC-PT, SOR FCC-PT, EOR
Riser temperature, °F (°C)
985 (529)
985 (529) 1360 (738)
Regenerator temperature, °F (°C) 1356 (736)
Cat/oil ratio, wt/wt
6.1
6.0
Conversion, wt% yield
70.7 14.4 14.9 47.3
71.2 13.2 15.6 47.9
Slurry
LCO
Gasoline
BB PP
8.1 5.0 4.2 6.1
8.0 5.0 4.2 6.1
Dry gas
Coke
Dry gas, MMSCFD (scm/h) Wet gas, MMSCFD (scm/h)
25.7 (30,300) 25.7 (30,300) 45.1 (53,100) 45.0 (53,000)
Table 3
import feed-quality flexibility. Product yield selectivities are often better than FCC opera- tions lacking this upstream equipment. The FCC-PT can provide the FCC with upgraded feed quality, thereby improving its crackabil- ity and product yield selectivity. Optimisation scenario A refiner operates an FCC-PT–FCC com - plex (see Figure 7 ) in which a high-pressure FCC-PT operates at constant feed hydrodeni- trogenation (HDN) for a 32-month cycle that aligns with the mid-cycle for the FCC opera- tion. The FCC cracks 100% of the FCC-PT product at 60 MBPD under partial-burn regeneration. Owing to increasing severity over the oper- ating cycle, the FCC-PT start-of-run (SOR) and end-of-run (EOR) product qualities are different. As a result, the FCC performance varies at constant coke yield. Lower slurry yield and increasing transportation fuel yields are seen towards the EOR. The influence of the two FCC-PT conditions on FCC perfor- mance is shown in Table 3 . Running the FCC-PT at the higher EOR severity throughout the entire cycle will shorten the catalyst operating cycle, which can cause complications for site turnaround planning and scheduling. The FCC-PT cycle will no longer align with the FCC cycle. By upgrading FCC feed nozzles, it is possible to realise the increased FCC unit conversion and better yields associated with the feed qual- ity from higher EOR FCC-PT severity with- out actually increasing the FCC-PT severity, thereby preserving the FCC-PT operating cycle. Table 4 shows the impact of upgrading feed nozzles under FCC-PT SOR conditions. A drop in regenerator temperature and a
FCC performance with upgraded feed nozzles under FCC-PT SOR conditions
Existing feed nozzles
Upgraded feed nozzles
Riser temperature, °F (°C)
985 (529)
985 (529) 1337 (725)
995 (535) 1350 (732)
Regenerator temperature, °F (°C) 1356 (736)
Cat/oil ratio, wt/wt
6.1
6.5
6.6
Conversion, wt% yield
70.7 14.4 14.9 47.3
71.1 14.2 14.7 47.9
71.6 14.0 14.4 47.8
Slurry
LCO
Gasoline
BB PP
8.1 5.0 4.2 6.1
8.4 5.2 3.5 6.1
8.3 5.4 4.0 6.1
Dry gas
Coke
Dry gas, MMSCFD (scm/h) Wet gas, MMSCFD (scm/h)
25.7 (30,300) 21.7 (25,600) 45.1 (53,100) 41.9 (49,300)
24.3 (28,600) 44.7 (52,600)
Table 4
FCC performance with upgraded feed nozzles under FCC-PT E OR conditions
Existing feed nozzles
Upgraded feed nozzles
Riser temperature, °F (°C)
985 (529)
985 (529) 1348 (731)
995 (535) 1359 (737)
Regenerator temperature, °F (°C) 1360 (738)
Cat/oil ratio, wt/wt
6.0
6.4
6.4
Conversion, wt% yield
71.2 13.2 15.6 47.9
71.8 12.9 15.3 48.6
72.2 12.7 15.1 48.5
Slurry
LCO
Gasoline
BB PP
8.0 5.0 4.2 6.1
8.4 5.2 3.5 6.1
8.3 5.3 4.0 6.1
Dry gas
Coke
Dry gas, MMSCFD (scm/h) Wet gas, MMSCFD (scm/h)
25.7 (30,300) 21.9 (25,800) 45.0 (53,000) 42.0 (49,500)
24.5 (28,900) 44.8 (52,800)
Table 5
44
PTQ Q3 2022
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