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Filtration technology In order to achieve effec-tive and reliable removal of the solid concentration in FCC bottom product, DAHLMAN designed, engineered and fabricated a FCC Slurry Oil Filter package, con-sisting of the following main components:

two for three filter vessels

backwash receiver vessel

gas accumulator tank

interconnecting piping

control and maintenance valves

instrumentation

controls (PLC) The filter vessels are suitable for processing 100% of the design flow rate and contain Dahlman’s high qua-lity sintered porous metal filter media retaining the catalyst fines on the inner surface of the elements. Clean filtrate passes through the built-up solids “cake” and filter medium and differential pressure increases. Once the pressure drop across the filter has reached its pre-set maximum value after normal filtration mode, the cleaning sequence is automatically started. The feed and filtered product connections are both closed and, subsequently, the valve connecting a gas accumulator will open towards the FCC Slurry Oil filter vessel. This results in pressurization of the slurry oil contained in the filter vessel. When a quick-opening valve installed below the filter vessel opens, the gas pocket pressurizing the FCC SO from above, rapidly expands. This results in a reverse flow of the slurry oil, from the outside to the inside of the filter elements. As a consequence, the collected particles/filter cake dislodges over the entire surface of the filter tubes. Together with the filtered liquid, the solids are forced further back by the expanding gas, and are transferred to the backwash receiver vessel in a matter of seconds.

Introduction For many refineries operating an FCCU, filtration of main fractionator bottoms (MCB), or so-called slurry oil, offers very attractive benefits. By re-ducing the amount of catalyst fines in the slurry oil, the product is upgraded to a more valuable commo-dity and can be used for various applications instead of disposing it as a waste product. As a result, addi-tional revenues up to $40/barrel have been seen and short return on investments are achieved. Since January 2004, a modern European refinery is operating an automatically regenerated backwash filtration system in its FCC plant. The main purpose for installing a slurry oil filtration package for this refiner was to protect the catalyst bed of a new LC Finer sys-tem. For this purpose DAHLMAN designed, fabricated and delivered a completely assembled FCC Slurry Oil Filtration Package making use of highly effective gas-assisted backwash cleaning technology. This document describes DAHLMAN’s advanced filtra-tion technology and the field results after nearly 8 years of successful operation.

Process description LC Fining is based on an efficient fluidized bed process used for desulfurization, demetallization, Conradson carbon reduction, and hydroprocessing of atmospheric and vacuum resids. Since solids in the feed tend to build up in the circula-ting beds of such hydrogenation systems and cause dilution, they need to be removed from the feed prior to introduction to the reactor(s). Catalyst fines escaping capture in FCC reactor cyclones, are fed along with the reaction products to the main fractionator column in the FCC product separation system, and leave the fractionator with the main column bottom product. If the amount of catalyst fines in FCC slurry oil is reduced to at least < 100 ppm wt, the filtered product can be used as a proper feed for the LC Finer unit.

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F C C S L U R R Y O I L F I L T R A T I O N

I N C R E A S I N G T H E R E V E N U E

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W W W . D A H L M A N . N L | T . + 3 1 ( 0 ) 1 0 5 9 9 1 1 1 1 | E . D A H L M A N @ D A H L M A N . N L V O L U M E 1 , N O . 1 1 — D E C E M B E R 2 0 1 1

Onsite testing with DAHLMAN’s Industrial Scale Pilot Filter Malfunctioning filtration units can often put a strain on a refiners’ profitability. Unnecessary quanti-ties of valuable backwash volumes may get lost or fre-quent cleaning of filters puts a burden on budget and staff. DAHLMAN can provide mobile industrial test equipment and field test engineers, who can be mobi-lized to any plant to assist in problem solving and opti-mizing the operation of critical assets. DAHLMAN’s Industrial Scale Pilot Filter is a semi-automatically operated and controlled, skid mounted test rig, fully designed for onsite testing of for instance FCC slurry oil or heavy coker gasoil filtration.

DAHLMAN’s gas-assisted backwash technology elimi-nates channeling and incomplete cleaning. It is consi-dered to be the most effective and efficient in-situ cleaning method. The operating temperature is critical for the reliability of the filtration process; for instance asphaltene precipitation on the filter media may occur when operating at too low temperatures, resulting in reduced cycle times and the need for undesirable ex-situ cleaning of the filter element. With DAHLMAN’s filtration technology, the sludge, disposed in the backwash receiver vessel, can be redi-rected to the riser, while maintaining a continuous flow rate.

Field results The full scale filter package was started up early 2004 by DAHLMAN in close cooperation with the refiner. The site acceptance test demonstrated that DAHLMAN’s slurry oil filtration technology redu-ces the solid content in the bottom product to far be-low the required and guaranteed 80 ppm wt. based on ash content (ASTM D482-95). Now that the slurry oil filter is in operation, the refiner is able to feed the LC Finer unit with 60% of primary VGO and 40% of cracked, and filtered VGO. Upgrading of the slurry oil significantly contributes to a high return on invest-ment for the refiner. Injection of backwashed sludge to the FCC riser is ac-complished via a dedicated feed nozzle (part of total feed distribution system). At present this amounts to

approx. 3,5 m3/hr. Continuous introduction and feed is guaranteed, by using hydroprocessed VGO as carrier medium. Conclusion After nearly 8 years of operation it can be concluded that DAHLMAN’s FCC Slurry Oil filtration package has provided a financially attractive and satis-factory solution to the refiner. The system continuous-ly operates above its design values, meaning with sig-nificantly higher flow rates and solid concentrations. Filtration cycle times of more than 6 hours are achieved while the vast majority of the original ele-ments are still in place. The installed technology has proven that combining highly efficient filtration and gas-assisted in-situ backwash cleaning, results in a reliable and effective reduction of the solids content to very low levels of 10 - 30 ppm wt.

Main operational figures (Q4, 2011)

Flow rate 7 up to 15 m

3/h

original design 10 m3/h

Operating

temperature 280 - 285 °C

Inlet solids

concentration

1000 up to 1700 ppm wt.

original design 800 ppm wt.

Outlet solids

concentration

< 10 - 30 ppm wt. based on

ash content (ASTM D482-95)

original guarantee

80 ppm wt.

Filtration cycle

time

at present approx. 6 hours

(see fig. 1)

Fig. 1: After two TAR’s DAHLMAN’s Slurry Oil

Filtration Package still achieves filtration cycle times

of more than 6 hours