As discussed in Increasing Crude Flexibility, refiners can capture substantial value by increasing their crude flexibility. Meanwhile, a site’s residue conversion capability is becoming an increasingly important value driver, especially given the forthcoming changes to marine bunker fuels specifications that are examined in The Bunker Fuels Challenge: How should you respond? Consequently, ever more refiners are evaluating a solution that addresses these twin objectives: converting their residue desulphurisation unit to a deasphalted oil (DAO) hydrocracker so they can simultaneously increase crude flexibility and minimise fuel oil production.

Shell’s Pernis refinery in the Netherlands has taken a positive step to reduce its exposure to the forthcoming changes to bunker fuel sulphur specifications. By installing a new solvent deasphalting (SDA) unit and revamping its residue hydroprocessing unit to a DAO hydrocracker, the refinery will increase its conversion of fuel oil to distillates. Crucially, this will also increase its crude flexibility.

With a capacity of 404,000 bbl/d, Pernis refinery is the largest integrated refinery–petrochemicals manufacturing site in Europe and, with hydrocracking, fluidised catalytic cracking (FCC) and gasification units in its configuration, it has a high Nelson complexity index.

As shown in Figure 1, the plan at Pernis is to integrate the new SDA unit with a DAO hydrocracker and the gasification plant. This is a relatively low-cost way of reducing fuel oil production while also enabling processing of a wider range of lower-priced crude oils. The new hydrocracker has a design feed of 100% DAO (extraction depth 60–70% on vacuum residue) derived from the main Pernis crude sources (Russia, the Middle East and Africa). It will operate at 65% conversion and produce ultra-low-sulphur-diesel and jet kerosene. The unconverted oil will go to the existing FCC unit. The hydrocracker will have a two-year cycle length.

SDA asphalt will go to the gasifier, with optional routing to bitumen or the fuel oil pool.

Revamping existing units and the tight integration with the rest of the refinery mean that the project could achieve a return on investment above 15%, which is a factor of two higher than the prediction for the industry-standard solution, a delayed coker.

Polish refiner Grupa LOTOS essentially proved DAO hydrocracking technology in 2011 when it became the world’s first refiner to make a new generation of DAO hydrocracking technology operational. The company built a new residue upgrading complex at its Gdańsk refinery featuring an advanced SDA unit that takes in vacuum residue and produces DAO that is sent directly to a 45,000-bbl/d DAO hydrocracker that it licensed from Shell Global Solutions.

In the years since, the unit has demonstrated high reliability, despite processing a very difficult feed. The design feed was 5-wt% Conradson carbon residue (CCR). Consequently, DAO hydrocracking has risen in prominence and other refiners have licensed similar schemes.

Pernis’s DAO hydrocracker builds on the lessons learned from Gdańsk. It will use the same SDA technology, a residuum oil supercritical extraction unit licensed by KBR that prepares high-quality DAO suitable as hydrocracker feedstock. However, the hydrocracking will take place in a revamped residue hydroprocessing unit rather than a grassroots hydrocracker. The existing residue unit’s relatively large catalyst volume enables Pernis refinery to process high-severity feeds. For example, at 7.4 wt% CCR (Table 1), its feed is one of the highest CCR feeds any hydrocracker anywhere is processing.

The project should have a major impact on the refinery’s economics, as it will increase its conversion of fuel oil, for which markets are diminishing, into valuable distillates. Overall, the facility’s fuel oil yield is likely to fall from 12 to 8%.

Another key advantage, given the changing crude slate, is that it will also improve the site’s crude flexibility. At present, one of the refinery’s crude diet constraints is the maximum allowable metals content in the vacuum residue that the existing vacuum residue hydrotreater can process. The new configuration will lift this constraint because the SDA unit will concentrate the crude impurities, such as CCR, asphaltenes and metals, in the asphalt stream that are routed to the gasifier or to bitumen. With the refinery’s strategic location in a major trading hub, this factor has the potential to add substantially to the site’s economics.

The relatively lower value of the SDA asphalt that will feed the gasifier should enhance the economics further compared with using vacuum residue, as it does now.

Table 1: Pernis refinery’s new DAO hydrocracker will have an extremely challenging feed.

Design case Urals crude
SG at 15°C 0.960
Sulphur, wt% 2.48
Total nitrogen, ppm 4,000
Vanadium, ppm 32
Nickel, ppm 10
Total metals (nickel + vanadium), ppm 42
CCR, wt% 7.4

Key Takeaways

  • Shell’s Pernis refinery is installing a new SDA unit and revamping its residue desulphurisation unit to a DAO hydrocracker.
  • Compared with other technology options, the return on investment could be extremely high (over 15%) but tight integration with other units will be vital.
  • It offers the potential to reduce fuel oil production by 4% and increase middle distillate yield and the site’s crude flexibility.
  • The project builds on lessons learned from Grupa LOTOS’s Shell-licensed DAO hydrocracker, which broke new ground and continues to show strong performance.

More in Industry Focus

Aromatic saturation technology

Understand why many refiners are upgrading light cycle oil (LCO) in an existing hydrodesulphurisation (HDS) unit using aromatic saturation technology.