Refinery Process Solutions · Case study

Northshore CES1490: FCC slurry de-ashing for bunker-fuel sales

A 10 MMTPA refinery evaluated Northshore CES1490 to bring FCC slurry within marine bunker-fuel limits. The customer reported a 93% reduction in aluminium plus silicon at 24 hours, with both trial tanks meeting the ash and Al + Si specifications in half the agreed settling time.

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Operating context and acceptance basis

The refinery wanted to sell slurry oil from its 2.2 MMTPA FCC unit as marine bunker fuel rather than burn it as low-value fuel. Feed slurry contained 454–506 mg/kg Al + Si, approximately eight times the 60 mg/kg bunker limit. Four 2,000 m³ settling tanks with in-line dynamic mixers and flocculators had to release slurry within 48 hours to maintain the FCC unit’s operating cycle.

The technical agreement set two analytical limits for a composite of upper, middle and lower samples taken above the high draw-off nozzle: ash by GB/T 508 at ≤0.05% and Al + Si by IP 501 at ≤60 mg/kg. It also capped dose at 360 g/t of slurry and required no tank-safety issue or adverse effect on settled-sludge disposal.

Product and monitored application

Northshore CES1490 was pumped into the slurry line ahead of the in-line dynamic mixer and settled in tanks TK101–TK104. Tank temperature was 85–99 °C during the trial and 80–99 °C through the later campaigns.

The trial ran from 18 to 24 March 2024 over two tank batches: 3,654 t of slurry and 1.31 t of product, averaging 358.5 g/t. Each tank was sampled at sealing, 24 hours and 48 hours. The plant then ran 16 batches from 14 April to 20 May 2024 and 17 batches from 3 January to 25 February 2025.

Trial result: both tanks on specification at 24 hours

In TK101, Al + Si fell from 74 mg/kg at sealing to 35 mg/kg at 24 hours and 31 mg/kg at 48 hours; ash moved from 0.030% to 0.013% and remained there. TK102 fell from 61 to 30 to 26 mg/kg Al + Si, while ash fell from 0.018% to 0.011% and then 0.006%. Both tanks were inside both specifications at the 24-hour sample.

Al + Si compared with the 60 mg/kg limit

Feed slurry454–506

24 hours30–35

48 hours26–31

Figure 1. Customer-reported Al + Si values in mg/kg. The 24-hour clarified-oil range represents a 93% reduction from the reported feed range; the 48-hour range represents 94%.

The comparison uses the feed range and the composite clarified-oil results reported by the customer. It describes this refinery’s tanks and operating conditions; performance at another site depends on fines loading, mixing, temperature, settling time and draw-off arrangement.

Production campaign record

Customer-reported campaign summary
Period	Batches and slurry	Average dose	Reported quality
18–24 Mar 2024	2 trial tanks; 3,654 t	358.5 g/t	Both trial tanks met ash and Al + Si limits at 24 h
14 Apr–20 May 2024	16 batches; 25,753 t	295.5 g/t	15 logged batches at 70–210 mg/kg ash and 20–55 mg/kg Al + Si
3 Jan–25 Feb 2025	17 batches; 30,250 t	357.0 g/t	30–150 mg/kg ash and <15–56 mg/kg Al + Si in all 17 batches

Thirteen of the 17 batches in 2025 cleared within 48 hours; four required 56–72 hours. The 2024 daily dose was reduced from 317 to 261 g/t without losing the stated specifications across the 15 batches inside the reported campaign period.

The three periods together cover 59,657 t of slurry at a volume-weighted overall dose of approximately 331 g/t. One trial day, 19 March, reached 382 g/t while making up a prior shortfall after control-room and field metering readings differed; every other reported day was within the 360 g/t cap. The customer reported no tank-safety issue and no adverse effect on sludge disposal.

Operational value

The reports provide no monetary figure. The refinery’s stated objective was to blend or sell the clarified slurry as bunker fuel rather than burn it. A site-specific value model would use the slurry volume, treatment dose, price difference between bunker-blend and fuel-oil dispositions, and any tank-turnaround time released by reaching specification sooner.

The 24-hour trial result demonstrates spare time against the 48-hour agreement for those two tanks. The later 2025 record also shows that four batches needed longer, so an operating plan should retain flexibility for feed and settling variability.

Applying the findings

Fix the acceptance protocol before dosing: settling time, sampling levels, test methods, ash limit and Al + Si limit. Test the actual slurry to set the starting dose, then log every tank batch rather than relying on selected samples.

Size the initial dose for the upper expected fines loading and re-check it after a stable run. This refinery reduced its 2024 campaign dose from 317 to 261 g/t while the recorded batches remained on specification, but later variability confirms that dose and settling time should be reviewed together.

Discuss a similar application

Request the full illustrated case study and share your slurry ash, Al + Si and solids content; tank size, draw-off height and available settling time; and the existing injection and mixer arrangement. Cestoil can review whether the reported approach is relevant to your bunker-fuel or slurry-disposition objective.