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Sep-2020

IMO 2020: meeting the challenge

Developments in fuel additive technology address challenges and uncertainties raised by the IMO 2020 regulations

KERSTIN MÜLLER
Clariant

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Article Summary

In one of the largest changes to environmental regulations in the shipping industry for decades, new rules reducing the sulphur content of marine bunker fuels came into force, beginning 1 January 2020.

Before these rule changes, shippers used low grade bunker fuel, the world’s dirtiest diesel and a byproduct of the refining process. This bunker fuel had high sulphur content and was a major contributor to air pollution, as the exhaust from sulphur that is burned can be harmful to both humans and the environment. Now ships are required to use fuels with sulphur content capped at 0.5% compared to the previous limit of 3.5%. As the biggest reduction in the sulphur content of a transportation fuel that has ever been undertaken at one time, this move will drastically improve air quality and human health, particularly for those living close to ports and coastlines.

More broadly, the new regulations are part of a more ambitious, and longer term, sustainability strategy by the International Maritime Organization (IMO), the United Nations shipping agency. For the IMO, the year 2020 marks the beginning of the Sustainable Shipping for a Sustainable Planet initiative. This includes the goal of reducing greenhouse gas emissions from shipping by at least 50% by 2050 compared to 2008, whilst pursuing efforts towards phasing them out totally.

Leading up to the introduction of the new regulations, industry experts and analysts tried to forecast the impact on the shipping and bunker fuel industries – from cost implications and potential shortages of low sulphur fuel oil (LSFO) to oil comingling challenges and regional impacts, for example in Africa, given the mix of lower and higher sulphur in oil production across that continent.

Six months in, questions still remain as to how the balance between environmental improvements and the potential impact on the bunker fuel and shipping industries is going to be achieved and, furthermore, how this first move to LSFO will be implemented in the longer term.

Though it is still early, concerns have already been raised. Since the new regulations have come into force, Standard Club, a specialist marine and energy insurer, says that it has been notified by some concerned members of the non-availability of compliant fuel at some ports, although it was not specific as to which ones.1  Likewise, ship owners have warned of complications around LSFO, particularly in relation to sediment and wax formation.2  In addition, the ISO Standard 8217 that specifies the requirements for fuels for use in marine diesel engines does not provide specific guidance on the composition of low sulphur fuels,  causing these LSFOs to vary greatly in composition and quality.

Before the new IMO 2020 regulations came into force, the main blend component for high sulphur fuel oil (HSFO) was high sulphur residue. The residue was blended with various cutter stocks to create the final HSFO composition. With the new regulations, high sulphur components will need to be replaced. In principle, refiners have three options available to them to accomplish this: additional desulphurisation, blending with low sulphur distillates, or the use of low sulphur crude oils as feedstock. Which option is preferred is dependent on the set-up of the individual refinery and the availability of blend components and crude grades.

Crudes and heavy fuel oils are complex mixtures of various hydrocarbons ranging from paraffins, aromatics, naphthenes, and resins to asphaltenes. While aromatic type LSFO bears a higher risk of instability, and incompatibility, when comingled with other fuel types, paraffinic type LSFO might show cold flow challenges like increased pour points. Put simply, paraffins will precipitate when cooled down whilst asphaltenes will precipitate when destabilised. Diluting high sulphur streams by using low sulphur distillate streams like marine gasoil will also have an effect on the cold flow characteristics.

So what are the key challenges with fuels that contain paraffins? Paraffins in the fuel tend to crystallise when cooled down, leading to severe increases in viscosity and solidification. They could be redissolved through heating; however, this requires a tremendous effort in terms of cost and time. Changing the crude slate towards low sulphur crudes like ‘sweet light’ will ultimately also increase the amount of paraffins processed. Hence a higher pour point of the resulting fuel oil can be expected.

A pour point is the lowest temperature at which a fuel or oil will pour and, through additives called pour point depressants (PPDs), the pour points of fuel oils can be significantly reduced without changing the combustion behaviour of the LSFO. PPDs are polymer-like additives which are dosed to the LSFO ideally right after the blender fuel outlet, when the temperature of the fuel is high.

PPDs do not change the temperature at which wax crystallises or the amount of wax that builds up. Their application relies on the PPD co-crystallising with the targeted paraffin species present in the oil, thus modifying the wax crystal structures to one more favourable to flow. Further, the wax crystals are kept isolated by the PPD backbone and, because of this steric hindrance, the wax crystals are no longer able to form the 3D structures responsible for gelation and flow inhibition.

Crucial to its application is that the PPD is dosed above the ‘wax appearance temperature’ (WAT) of the fuel. The WAT describes the temperature at which the first paraffin crystals start to form when a fuel is cooled down. The WAT can be determined by different methods like differential scanning calometry or viscosity measurements; however, such methods usually do not exist in refinery laboratories. A general rule of thumb is to dose the PPD 20°C above the pour point of the fuel; for example, if the fuel has a blank pour point of 39°C, it would be recommended to dose the PPD at 60°C.

As a leading provider of marine fuel additives, Clariant Refinery Services has developed two PPD additive solutions for new types of marine fuels including Dodiflow 8421 and Dodiflow 6087, to ensure that the bunker industry can be confident in low sulphur blended fuels being compliant and safe.


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