Interview: Rojgaard says wider variety is new frontier of VLSFOs

New York — Key variables, such as viscosity and density, in new IMO 2020-compliant bunker fuels mean those handling them must be prepared, but many of the challenges are familiar, according to fuel testing agency Bureau Veritas.

"It is all about temperature management to ensure the correct viscosities are applied for separations and injection," Charlotte Rojgaard, global head of Bureau Veritas' Marine Fuel Services, told S&P Global Platts in an interview. "This is not a new challenge but whereas the [3.5% sulfur] RMG 380 fuels pre-2020 did not vary much on viscosity, the [very low sulfur fuel oils] currently vary quite a bit."

The limit of sulfur content in marine fuels burned on the high seas fell from 3.5% to 0.5% on Januar,y 1, as mandated by the International Maritime Organization. Ships equipped with exhaust gas cleaning systems, or scrubbers, can continue to burn 3.5% S FO.

The new VLSFOs are on the whole more paraffinic, have a larger range of viscosities and display wider geographical variation, according to Bureau Veritas data.

As expected with the drop in the sulfur cap from IMO 2020, average sulfur content in January and February of this year was 0.46%, compared with 2.48% a year earlier.

In addition, the lower sulfur content marine fuels has brought a drop in average viscosities. VLSFO averaged 112.5 CST between January and February 2020, compared with an average of 337.9 CST in high sulfur fuel oil in the equivalent period in 2019, the data showed.

The viscosity range of VLSFO blends spanned from as low as 2.239 CST, to as high as 600 CST, between January and February 2020, Bureau Veritas said.

Platts added a minimum viscosity of 30 CST at 50 degrees Celsius to its global marine fuel 0.5% S assessments across all regions and sizes, including cargoes, barges and bunker deliveries effective April 1.

Viscosity has been a growing area of concern and linked to a rising share of distillates in the new VLSFO blends, fuel management provider Integr8 said in a research note March 18.

"The viscosity drop has affected most bunker hubs. For example, viscosity in ARA dropped 30 CST by March to 100 CST and there was a bigger decrease in Singapore, from 170 CST down to 90 CST, with an even bigger reduction in Malta, from 150 CST to 50 CST," Anton Shamray, senior research analyst at Integr8 said in the research note.

Rojgaard was more circumspect.

"For some ports there seems to be a slight trend supporting [the picture of decreasing viscosity] – but not at all. I believe we need another couple of months before we can confirm this trend," she said.

In any case, it remains important to keep different fuels separate.

"It was important before 2020 – and it still is – to avoid mixing of fuels and to always evaluate which fuel have received on board and to take the proper action [based on] the actual fuel," Rojgaard said.

COLD FLOW PROPERTIES FEEL THE HEAT

Besides viscosity, there are a number of other fuel characteristics to consider.

"When storing any type of fuel, you must consider stability (temperature and time of storage), cold flow properties (temperature) and viscosity (temperature)," Rojgaard said. "That's how is has always been. However, the new challenge is the properties of VLSFOs varying more than fuels within a specific grade of HSFO vary. This puts more importance on considerations of the actual fuel property when storing the fuel."

Bureau Veritas data showed that the Pour Point temperature for VLSFO samples was on average higher compared to HSFO.

"Twenty-four percent of tested VLSFOs had a Pour Point temperature exceeding 21C, whereas for HSFO last year this number was 0.1%," said Rojgaard, adding that VLSFO was on the whole paraffinic.

In particular, the Pour Point temperature of the fuel is considered to be an important cold flow property, as the lowest temperature a fuel can "pour" under gravity.

In terms of compatibility issues, Rojgaard noted there have been fewer this year:.

"We did occasionally see compatibility issues pre-2020 and we have seen issues post-2020," she said. "However, whereas there were some cases of compatibility issues onboard in the early days, we see [fewer] cases now."