Low viscosity is a major factor behind very low sulphur fuel oil (VLSFO) stability issues, Riviera’s Fuel additives and fuel blending: additives and their role in maintaining fuel stability during storage and reducing CO2 emissions webinar has highlighted
Sponsored by Aderco and Innospec, the webinar was held on 10 March 2021 during Riviera’s Marine Fuels Webinar Week, and also revealed the results of a benchmark fuel ageing case study.
Aderco Singapore technical manager Asia & Pacific Idris Talib told delegates at the webinar “At Aderco, we have dealt with more than 220 bad fuel cases in 2020, most of them successfully solved through our treatment and advice. In the last two months we have seen more than 30 cases. The majority of the cases fall in the low viscosity fuel category, especially below the 80 centistoke (cSt) mark. Many of these cases are due to fuel degradation, which results in instability and high sedimentation in the tanks.”
He singled out that major issues in 2020 caused by VLSFO included fuel stability and incompatibility issues. “In 2021, the fuel stability issue still remains and is a major problem for many of the shipowners that have fuels that produce sedimentation.” This could cause damage to machinery on board.
Benchmark case study
Aderco took part in a benchmark fuel ageing case study, carried out by third-party V-TIC Services (www.vticservices.com). Three additives from three major additive manufacturers – including Aderco – were tested. The test was based on the comparison of total sediment existent, which is the most suitable test for fuel ageing. Ten samples with varied density and viscosity were used.
The case study showed that viscosity may be an indicator of how VLSFO will be if stored for a long time. The effect of low viscosity on total sediment existent is highlighted by the study. The highest sedimentation is observed in the low-viscosity samples, with sample number three having the lowest viscosity and highest sedimentation out of all the samples. Similarly, other low-viscosity samples had increased sedimentation. However, higher-viscosity samples remained within the ISO8217 specification deteriorating from the initial sedimentation figures.
Mr Talib noted that this has corroborated with Aderco’s clients’ experiences – most of their bad fuel cases involving sedimentation and stability issues had low viscosity.
Mr Talib revealed that the Aderco 2055G molecule showed a reduction in low-viscosity samples after four weeks of ageing and the eight-week results showed a reduction in all fuel samples regardless of the viscosity. “Aderco provides stability for fuel,” said Mr Talib, highlighting that the study demonstrated the effectiveness of Aderco2055G in limiting fuel degradation.
Meanwhile, Innospec marine market specialist Joshua Townley also highlighted the problems of the impact of lower viscosity on the stability of VLSFOs. “IMO has recognised there is lower viscosity and density across the board with VLSFOs and that they come with a higher net-specific energy, lower MCR and lower CCAI and a higher pour point. This is to do with the increased paraffin content in these fuels and I think there is a link between this and the inherent stability of the residual currents in the fuel.”
He pointed out that total sediment potential is considerably higher for VLSFOs versus high sulphur fuel. “VPS has witnessed that VLSFOs, in terms of stability, exhibit a much shorter shelf life of approximately three months. Which is drastic when compared to stable high sulphur fuel oil, previously stored for around 12 months safely.”
Reviewing the fuel spec
To reflect this, ISO is in the process of reviewing the fuel specification. Mr Townley commented “There is some pressure from the industry, namely around introducing a minimum viscosity limit. There is some recognition that something needs to be done.”
Mr Townley explained that Innospec has been mapping viscosity of VLSFO and the proportion of problems seen on ships. “Most of the problems are occurring where viscosity is low. Overwhelmingly it is separation failure… This makes sense when considering the composition of the fuels. They are lighter and less stable. When applying pressure and temperature at purification, this is when they come apart a little bit.”
While more problems are involved with less density, Mr Townley added “The interesting trend I see is that the higher-density fuels seem to be the ones involved in all the liner-wear issues… as residual components become unstable, they grow and impact the combustion quality, leading to liner-wear [issues].”
Like Aderco, Innospec is able to show how additives can solve VLSFO instability. In January 2021, ClassNK verified the effect of Innospec’s Octamar HF-10 Plus on VLSFO stability. The treated fuel remained homogenous.
Mr Townley said “It means less sludge, less unplanned maintenance, better conditions for crew and better performance for the fleet.”
Fuel additives also play an important role in reducing emissions. Mr Townley highlighted how Octamar Ultra HF has led to a 26% reduction in carbon monoxide, 60% reduction in particulate matter and a 73% decrease in unburnt fuel in the exhaust. He explains “The improvement works by reducing ignition delay and creating a more complete combustion, which also shortens the combustion period with a better release of heat… the 26% reduction in carbon monoxide is a fantastic indication of how much better the combustion quality is. There are less emissions and reduced fuel consumption.”
Both panellists highlighted their key conclusions. Mr Talib said “Issues will remain with VLSFO if low viscosity levels remain. We believe that with the right treatment, fuel can be managed and prevent unnecessary hassle for engine crew and purifiers with [the use of] additives.”
Looking to the future, he said that biofuel is expected to play a large role and that “we have put our feet totally in the pool with biofuel and have major testing going on right now.”
Meanwhile, Mr Townley singled out the major issue of VLSFO fuel stability in 2020. “What everyone keyed into is stability and last year we dealt with over 2,500 cases in Europe alone.” He emphasised “True innovation will come without passing on the additional cost to shipping.”
The issues with VLSFOs having low viscosity was reflected by a poll among webinar attendees. Asked whether VLSFOs with low viscosity (below 80 centistokes) have given them problems in the past six months, the majority – 61% – said yes, leaving 39% saying no.
Asked how many times they had encountered issues with unstable VLSFO in the last 6 months, the lead answer was three times (29%), followed by 25% for four times. 17% said two times, 8% plumped for once and 21% said zero times.
Elsewhere, 37% said they were somewhat worried about the quality of VLSFO, considering the increase in oil prices. This was followed by 31% being very worried, 24% being neutral, with just 4% being somewhat not worried and 4% not being worried.
When it came to the question: if you were in charge of selecting the fuel treatment to improve your fleet performance, how would you prioritise the following? 33% said first was third-party verification, followed by expertise and customer support and then price of product. This was followed by 21%, who said that expertise and customer support was first, followed by price of product and then third-party verification. While only 15% gave the order: price of product, third-party verification and expertise and customer support.
The last two questions highlight the importance given to fuel stability. When asked in what order of importance the following targeted chemistries will be of most use to the future of shipping, the majority (52%) said first was fuel stability and reliability, followed by improved fuel economy, then reduced emissions. 24% gave the order: improved fuel economy, reduced emissions, then fuel stability and reliability. 24% said: reduced emissions, then fuel stability and reliability followed by improved fuel economy.
The final question – the most important consideration for shipping is a chemistry that provides… – saw 70% say fuel stability and reliability, 19% said reduced emissions, followed by 11% for reduced fuel consumption.
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Riviera’s Fuel additives and fuel blending: additives and their role in maintaining fuel stability during storage and reducing CO2 emissions webinar panel were (from left to right): Aderco technical manager Asia & Pacific Idris Talib and Innospec marine market specialist Joshua Townley