Can you recommend a process route for residual fuel oil feed to help comply with the IMO’s revised targets for bunker fuels?

First published in PTQ Q1 2018

David Schwalje, Business Development Manager, Axens North America
Eric Peer, Senior Technology Manager, Axens North America

Refiners will address the upcoming January 2020 regulatory shift to lower sulphur marine fuels primarily utilising one of four strategies: (1) crude acquisition, (2) technology investment to produce compliant, low sulphur fuel oil (LSFO), (3) reliance on the persistence of an attractive market for high sulphur fuel oil (HSFO), or (4) conversion of HSFO to lighter products with the goal of either reducing their fuel oil production or exiting the market altogether. Of course, the technology approach for each refiner will depend heavily on existing configurations and local market conditions.

For many sweet crude refiners, a compliant (<0.5 wt% sulphur) product can be produced without desulphurisation. However, for the majority of refiners, sulphur removal will be required.
Desulphurisation of bunker fuel components (Axens’ Hyvahl technology) has been technically proven for decades, having been practised by numerous refiners for the preparation of lower sulphur residue FCC feeds. Due to the relatively high concentrations of Conradson carbon, asphaltenes, and metals, these units operate at moderate to high pressure with large catalyst volumes compared to distillate hydrotreaters.

Refiners looking to reduce or eliminate their production of bunker fuel will utilise conversion technologies including coking, solvent deasphalting (SDA), residue hydrocracking, or a combination of these.
Coking is of course a well established carbon rejection technology which requires moderately high capital investment to produce a solid coke and a variety of high sulphur, hydrogen deficient distillates for processing elsewhere in the refinery. Installing coking capacity will primarily be utilised by the refiner looking to exit the residual fuel oil production market.

SDA (Axens’ Solvahl technology) is a relatively low cost, solvent based solution which extracts a paraffin rich deasphalted oil (DAO) from residual oils and rejects a high sulphur, hydrogen deficient pitch product, typically used for asphalt production or as solid fuel. For the majority of crudes, the DAO will not be a compliant LSFO component; it can either be hydrotreated for compliance or – more likely – converted to lighter products via hydrocracking or FCC. As such, SDA is also a technology most suited for refiners looking to reduce or eliminate residual fuel oil production.

Residue hydrocracking (Axens’ H-Oil technology) utilises an ebullated bed reactor to achieve high residue desulphurisation coupled with high conversion via hydrogen addition. Conversions between 60-90% can be readily achieved. For many crude slates, hydrocracker unconverted oil can also serve as a LSFO blend component as a result of the unit hydrodesulphurisation rates. Additionally, FCC slurry oil is a desired feedstock for these units, which essentially allows the refiner to utilise the hydrocracker as a slurry oil desulphurisation unit.Ebullated bed residue hydrocracking can therefore couple LSFO production with conversion to higher value middle distillates with the flexibility to adjust conversion ‘on the fly’ using only operational changes. This solution will be particularly attractive for refiners looking to maximum residue conversion and distillate production.

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