PTQ Q3 2022 Issue

During the 2019 turnaround, the latest generation Shell Max Atomisation Feed Nozzles were installed. The yields of PP and BB increased while slurry oil yield dropped. The yield shifts are summarised in Table 2 . Unlike at Pulau Bukom, the bottoms upgrading was not seen in gasoline selectivity but rather in a shift to more BB and PP. An earlier unit upgrade in 2014 had already achieved good feed atomisation and dispersion within the circulating catalyst, and the new riser was operating with a low level of non-uniform radial mixing. Consequently, the extent to which gasoline was prematurely being cracked to light products was already low. So, instead of more gasoline, higher PP and BB yields were achieved through the conversion increase. Key results include a: • 0.6% increase in conversion • 1% decrease in slurry yield • 0.4% increase in BB yield • 0.2% increase in PP yield • Reduction in regenerator bed temperature of 39°F (22°C). Audited Result 3: Sarnia FCC unit, Canada The FCC unit at the Sarnia refinery operated to an air blower constraint, which was more severe in summer. During the 2016 turnaround, latest-generation Shell Max Atomisation Feed Nozzles were installed. As a result of lower feed coke production, the air-blower constraint was alleviated. The FCC unit performance improved in terms of: •Increased feed rate at constant conversion: for the six

Audited yield shifts after Puget Sound FCC unit feed nozzle upgrade

Component

Yield shift* (wt%)

Dry gas

–0.3

PP BB

0.2 0.4

Gasoline

–0.4

LCO

0.4

Slurry oil

–1.0

Coke

0.1 0.6

Conversion

*Audited at similar feed quality and rate

Table 2

The nozzle upgrade brought the site relief from this con- straint. The unit no longer experiences this limitation. Key results include: • 2.7% increase in conversion • 3.7% increase in gasoline yield • 1.8% decrease in slurry yield • Average riser temperature reduction of 27°F (15°C). Audited Result 2: Puget Sound FCC unit, Washington, USA The challenge with the Puget Sound refinery FCC unit was to optimise the economics, which processes a blend of vacuum gasoil and unhydrotreated heavy coker gasoil.

Figure 7 FCC-PT–FCC integrated plant

PTQ Q3 2022