Northshore CES1490: Slurry de-ashing for FCC recycle and flue-gas compliance

The refinery collected slurry oil from two FCC units in a receiving tank and returned the clarified oil to catalytic cracking. Incoming slurry normally contained about 3,000 mg/kg catalyst fines, rising to as much as 6,000 mg/kg during upsets. Reported ash before treatment was 0.26–0.30%.

The plant associated catalyst-fines recycle with increased particulate loading in regenerator flue gas. Its objective was to reduce slurry ash to below 0.05% (500 mg/kg) within 24–72 hours of settling, without mechanical changes. Acceptance was based on the average of top, middle and bottom samples taken above the high draw-off nozzle.

Northshore CES1490 is a slurry settling aid that promotes agglomeration of catalyst fines into larger, faster-settling flocs. Clarified oil is drawn above the sludge layer, while concentrated solids collect at the bottom for periodic removal.

The plant metered CES1490 through its existing slurry-solids additive system into the receiving line, mixed it in-line and settled the treated slurry in the receiving tank. The agreed program covered incoming solids up to 6,000 mg/kg, with a chemical-dose cap of 500 mg/kg on slurry.

The first delivery’s November tank results did not reach the target. Cestoil replaced the batch on 11 December 2019 and worked with the plant on laboratory settling tests on 20–23 December to confirm the dose before dosing resumed. A further 11 tonnes supplied the program from December 2019 to March 2020. The plant laboratory checked tank ash batch by batch.

Dose is expressed as chemical mass per mass of slurry. The reported fourth-quarter average includes the November period; it is not a dose recommendation for every slurry stream.

The three-level mean is calculated from the rounded tank values reported by the customer. A result of 0.05% equals 500 mg/kg: the bottom sample was at that level, while the three-level mean was below the agreement’s 0.05% criterion. This distinction clarifies the “below 0.05% at every level” wording in the supplied PDF.

The six reported tank-sampling results from late December through 2 March 2020 remained within the 500 mg/kg limit. The report also lists solids in clarified oil at 0.03–0.08%; solids content and ash are separate measurements.

The plant reported that de-ashed slurry returned to the FCC while flue-gas particulate emissions remained within applicable limits. Its operations department concluded that CES1490 could continue to be used. The supplied summary does not give measured flue-gas particulate concentrations or quantify an emissions reduction.

The refinery’s objective was to support slurry recycle while controlling ash and meeting its reported flue-gas requirement. The program used existing injection and tank equipment, with dose selection supported by laboratory tests and operating follow-up.

No monetary saving is reported for this refinery trial. The PDF’s carbon-black economic reference concerns a separate Cestoil application. For an evaluation at another site, record slurry volume, chemical dose and cost, the value of recycled or upgraded slurry versus its alternative disposition, and any avoided operating constraints.

Agree the acceptance test before dosing: available settling time, sampling levels above the draw-off, and the ash or solids limit. Run settling tests on the actual slurry to select an initial dose, then monitor tank samples for each batch and adjust treatment with the plant team.

Define the program against the upper end of expected catalyst-solids loading. Changes in incoming slurry, temperature, residence time and draw-off arrangements can change settling performance.