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Upgrading an FCC unit

Collaboration between technical and project teams enabled the fast-track replacement of an FCC unit

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Article Summary
PCK Raffinerie GmbH (PCK) located in North-East Germany, 100km from Berlin and near the city of Schwedt, is among the largest companies in the state of Brandenburg and the most important in the region. Every year, PCK processes 12 million tonnes of crude oil and is one of the largest crude oil processing locations in Germany, the primary products being diesel fuel, gasoline, kerosene, liquefied petroleum gas, heating oils and bitumen.

PCK is operated by a consortium of international oil companies, the major shareholders being Ruhr Oel GmbH (BP and Rosneft), Shell Deutschland Oil GmbH and AET-Raffineriebeteiligungsgesellschaft mbH (Eni and Rosneft).

Over the past 20 years, the shareholders have invested €2 billion in PCK, primarily in recent technologies and for environmental protection.

Project background
The PCK FCC unit at Schwedt refinery was first commissioned in 1981. The unit was originally designed by UOP, consisting of a high efficiency style combustor regenerator and downturned arm riser termination system. It has since been revamped several times by Honeywell UOP, most recently 15 years ago, more than doubling its original nameplate capacity of 150 t/h.

In 2010, UOP’s technical service specialists participated in a turnaround discussion for updating and modernising the FCC reactor technology. The increasing maintenance demands of the FCC reactor system after 15 years of service since the last replacement presented PCK with an investment opportunity to upgrade or replace the existing reactor. The upgrade option would incorporate the best available FCC technology while meeting the refinery’s long term processing objectives to increase its profitability by increasing feed capacity, maximising propylene yield, and increasing operating flexibility, meanwhile reducing maintenance headaches.

Project objectives
The FCC unit operates with a deep hydrotreated VGO feed with moderate to high reactor severity to maximise propylene and/or gasoline as demand dictates. Hydroprocessing the feed negates the requirement for post treatment of gasoline product for sulphur. Table 1 shows the typical feed qualities of the PCK FCC unit.

The challenges posed by clean feeds with very low Conradson carbon content and the implementation of highly coke selective FCC technologies characteristically results in a very low delta coke operation. This at best would be challenging for any FCC regenerator to deal with and assure efficient coke combustion kinetics and minimal afterburning.

Honeywell UOP solution
Following the 2010 turnaround, a study was executed by UOP which evaluated a number of revamp options and objectives.

The solution proposed was a complete new reactor including the following UOP technologies:
• Vortex separation system (VSS)
• RxCat design
• AF stripper packingww
• Optimix feed distributors.

The challenges posed by the clean feed were overcome through the addition of RxCat technology which decouples the traditional FCC heat balance and permits the refiner to manipulate the regenerator delta coke operation by adjusting the recycle of carbonised spent catalyst from the FCC stripper to the riser. In this way, the refiner can adjust the delta coke up or down as required for maximum flexibility. PCK has established a threshold for the RxCat slide valve opening to maintain an acceptable minimum regenerator dense bed temperature to achieve minimal afterburning while maintaining good catalyst activity maintenance. Without the RxCat system at PCK, the regenerator would be severely challenged with regard to delta coke.

There were two principal revamp strategy options for PCK to evaluate:
•    Option 1: upgrade and repair existing reactor
•    Option 2: complete new reactor system.

The first option, though least costly from a capex standpoint, would result in a prolonged turnaround duration for extensive maintenance estimated to be in the order of six weeks. A new reactor would eliminate substantial risk and unforeseen maintenance elements of the existing equipment, resulting in a shorter turnaround window targeting three weeks, thus netting increased revenue, shorter payback time and fastest on-stream time.

After discussions by PCK with its shareholders on future investments, the revamp of the FCC was approved by the board and a fast track engineering project was initiated in 2011 to produce the necessary project and equipment design specifications.

Throughout 2011, UOP developed an engineering design package and worked with PCK to ensure that the proposed reactor design met PCK’s objectives for the revamp. Frequent dialogue between the project teams took place to ensure that any major engineering challenges, especially with respect to the existing reactor support structure, were addressed expediently to ensure the project remained on track.

In November of that year, the complete engineering design package was issued to PCK. At this point of the project, PCK already had awarded the detailed design and fabrication of the new reactor to MAN Diesel & Turbo of Deggendorf, Germany. Fabrication of the new reactor took place throughout 2012 with completion later in that year (see Figure 1).

Key enablers in execution strategy to reduce the schedule included:
• Mechanical design: changes to reactor tangent length and footprint minimised to allow re-use of existing support structure and maintain standpipe tie-ins
• Basic engineering design: advance preliminary release of mechanical drawings
• UOP shop inspection at manufacturing facility: ensuring no design inconsistencies and compliance with specification prior to shipping and delivery to site
• Fabrication and early equipment check-out: delivery of new reactor, equipment check-out and modifications required to accommodate the RxCat chamber were made several months in advance of turnaround
• UOP Technical Services Depart-ment: reliable and consistent support provided throughout the design phase and during start-up.
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