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Positive thinking: managing the challenge of low sulphur fuels

Posted 09.05.2019
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Industry stakeholders are increasingly voicing concerns over potential fuel quality problems associated with the use of new 0.50% bunker fuels after 2020. These fuels have yet to have market visibility but, as Charlotte Røjgaard of BV VeriFuel points out, many of the challenges they may bring should be manageable through onboard best practice. With just over 17 months to go before 1 January 2020, the shipping industry is ramping up its preparations to meet the new leg­islative environment, which reduces the sulphur content permitted in bunker fuel (outside sulphur emission control areas (SECAs) to a maximum of 0.50% for ves­sels not equipped with emission abatement technologies, such as exhaust gas cleaning systems (scrubbers).

The maximum 0.50% sulphur fuel oils (or very low sulphur fuel oils (VLSFO) as they are also called) are not yet widely available in the market, and this has led to much speculation on the properties that these new fuels may have. The speculation has tended to focus on the potential negative impact of these fuels, but the future may not be as dark as some fear.

There is a common understanding that, generally, VLSFOs will be more paraffinic and that suppliers will apply more blending in order to make these fuels. Many vessels operating in SECAs today are familiar with the maximum 0.10% sulphur ultra low sulphur fuel oils (ULSFO) which are used as the cheaper alternative to conventional marine gasoils (MGO). ULSFOs have a higher viscos­ity than MGO and tend to be more paraffinic.

Whereas paraffinic fuels have excellent igni­tion and combustion properties and generate more energy upon combustion, they require particular attention to their cold flow properties to avoid filter blocking and solidification in tanks.

Cold flow properties are not difficult to manage provided that the crew is aware of the temperatures that need to be main­tained to prevent wax precipitation; as a minimum, the pour point of a given fuel should always be reported. Similar con­siderations will apply for the VLSFOs.

Residual blend components contain asphaltenes which need to be kept in suspension to avoid precipitation. Aromatic blend components have the ability to keep asphaltenes in suspension, a property that paraffins do not have. The task for the fuel blender is to get the balance between asphaltenes, aromatics and paraffins right to make a stable fuel blend. When the industry last saw a surge in the supply of more blended fuels (with the introduction of the maximum 1.50% and maximum 1.00% fuel sulphur limits in 2006 and 2010, respectively), initially an increase in the number of unstable fuels was observed.

Over the first six months of these new sulphur content limits, the number of unstable fuels dropped to 'normal' levels. Naturally, lessons from these experiences should alert the industry to be cautious in this respect when receiving supplies of VLSFO during the first months of 2020.

Compatibility is a term frequently mentioned when discussing the post-2020 operations. Whereas stability applies to the fuel as sup­plied, compatibility is a term used when considering whether to mix two fuels. Two perfectly stable fuels can be incompatible resulting in an unstable blend. Incompatibility manifests itself in a way that can be simi­lar to an unstable fuel in that asphaltenes come out of solution, sludging and over­loading separators and blocking filters.

Incompatibility can noticeably occur during the change over from one fuel to another in the fuel booster circuit after the change over valve. Crews will likely observe an increase in separator/filter activity due to two incom­patible fuels mixing in the fuel piping/ tanks; however, when the change over to another stable fuel has been completed, the operational difficulties usually subside.

When using residual blend components, catalytic fines (cat fines) are also a risk factor. Cat fines are a well-known challenge to ship engines as they are abrasive and result in excessive wear if not sufficiently reduced in the fuel treatment and, especially, in the separators onboard. The separation efficiency depends on viscosity and density, where lower viscosity and density improves the efficiency. On average, the VLSFOs will likely have both lower viscosity and density compared to the average heavy fuel oils (HFO), for which reason the cat fines are likely to be easier to remove from a VLSFO than from an HFO.

Recently, many ships have felt the impact of challenging fuels supplied in the Houston area. A number of vessels, having bunkered in the area in March and April, suffered from filter blocking, separator sludg­ing and, especially, fuel pump sticking.

These incidents have led to specula­tion about whether this is an indication of what the industry can expect post 2020. It is important to note that the average sulphur content of the Houston fuels is about 2.50%, i.e. there is no obvious indi­cation that valuable low sulphur blend components have been used in these fuels.

If we look at the history of marine fuels, endemic cases occur once every 2-3 years. They are characterised by impacting several vessels having bunkered in a specific area during a specific period. The polymethacrylate cases in Houston in 2010­-2011 and the corrosive East Russian fuels in 2014 are other examples of endemic cases. It can be caused by a deliberate dumping of chemical waste, for example, or by unintentional cross contamination in the supply chain. In some cases, the use of inappropriate blend components has resulted in the fuels being harmful to operation.

Several suppliers and barges are involved in the current Houston case and the fuel testing agencies are each finding different chemical species, but only in small concentrations. The case highlights just how complicated marine fuel composition is and the challenges related to identifying components not normally found in fuels and linking the findings to the actual problems experienced onboard vessels. The use of non-standardised methods makes it difficult to validate the found results and to confirm the findings of a component by test­ing the same sample in a different laboratory.

Also, many of the used in-house methods do not properly quantify the components. The costs of these tests are significant and not all laboratories are willing to bear the costs of testing a wide range of prob­lematic as well as unproblematic samples bunkered in same port/period to document that the presence of the found component is clearly linked to the operational difficulties.

To get back to the question that has been asked by a lot of operators in recent months - is the Houston fuel issue a precursor for 2020? - we do not think so. There is no indi­cation that low sulphur blend components have been used in these fuels. Also, there is no common industry finding, yet, support­ing a certain component at a concentration that can be held responsible for the harm­ful behaviour of these fuels. The real culprit remains to be formally identified but until that happens there is no reason for opera­tors to feel that the Houston fuel experience will become a norm in post-2020 fuels.

There are also discussions in the industry that ISO 8217 will not cover the VLSFOs. This is not correct. When the ULSFOs were intro­duced to the market a few months before 1 January 2015, the ISO 8217 committee was in the final stages of releasing the sixth edi­tion. The ULSFOs came as a surprise to most of the industry and the ISO 8217 commit­tee did not have the time to make changes to the specification. As it was, it very soon became clear that the specification - as it stood - still provided the coverage needed and, despite the variability in their charac­teristics, the industry soon found suitable grades to place the ULSFO in. This has been well accepted and no one has found cause to question the suitability of ISO 8217 for these maximum 0.10% sulphur fuel oils.

The ISO 8217 committee considers that the ISO 8217 specification, as it currently stands, covers all fuels, including the VLSFOs simi­lar to the ULSFOs. The latest revision of the specification already addresses stability, cold flow properties, cat fines, deleterious materi­als etc., which are the main topics causing concern over 2020. Work is being done to elaborate on the concerns being raised by the industry in order to increase awareness about the expected properties of the coming fuels.

In 2002, the then US Secretary of Defense, Donald Rumsfeld, said: 'Reports that say that something hasn't happened are always interesting to me, because as we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know'.

We know that the 2020 sulphur regu­lations hold a lot of unknowns. However, when we consider what may come, the chal­lenges are not all new. The majority of the challenges that we can think of are man­ageable through preparation and training, and there is still enough time to achieve this.

By Charlotte Røjgaard, Global Technical Manager for Marine Fuels, Bureau Veritas - VeriFuel. 

First published in Bunkerspot, Aug/Sept 2018.

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