Shipowners are struggling with issues caused by differences in viscosity, density and the chemistry of very low sulphur fuel oils
One year on since the shipping industry transitioned to very low sulphur fuel oil (VLSFO) and vessel owners are encountering more handling issues and engine problems than had been expected.
During Riviera’s Fuel testing in a new age webinar, on 26 November 2020, Innospec technical services engineer for marine fuel specialties Joshua Townley said there have been more engine failures and issues since the industry-wide switching to VLSFO took place.
“No one anticipated the increases in engine damage,” said Mr Townley. “Some are still suffering ongoing issues, with most damage occurring when using higher density fuels with high viscosities.”
Of all the issues and faults encountered in 2020, almost 60% are from separation failure, with another 18% from blocked filters, 14% engine damage, 7% solids in storage tanks and the rest from cold flow (or low viscosity at low temperature) issues.
“There have been more fuel handling problems on ships, especially with lower viscosity VLSFOs, mostly through blocked filters and separation failure,” said Mr Townley.
Engine problems include piston ring breakage, injector failures, liner wear and scavenge fire.
Fuel handling issues can include purifier breakdowns and fuel starvation, while storage issues can involve excessive sludge, wax formation and comingling of different fuels with varying chemical composition and qualities.
“No one anticipated the increases in engine damage”
“Separation failure is seen across all density ranges, most commonly at lower densities,” said Mr Townley. “Engine damage occurs when using higher density fuels and solids in tanks seen above densities of 940 kg/m3 and filter blocking is seen across all density ranges,” he explained.
Some of the reasons for handling issues and engine problems come from the higher paraffinic (alkane) content or single-chain hydrocarbons in VLSFO compared to HFO.
“Typical blend ratios of modern residual marine fuels show a much higher proportion of the saturate (paraffinic) component in combination with aromatics (such as benzene), which are structurally dissimilar, causing separation and instability,” said Mr Townley.
“Paraffins are prone to rapid oxidation when heated, or drop out as wax in low temperatures,” he said.
This leads to cold flow issues and deterioration of VLSFO over time. Lower aromatic content in VLSFO means asphaltenes begin to agglomerate and increase in size, forming sludges in tanks and attributing to poor combustion,” said Mr Townley.
He said additives, such as Octamar, will prevent oxidation of paraffins and reduce growth of asphaltenes.
Intertek Lintec global technical manager Tracy Wardell said some of the problems shipowners have faced with VLSFO is down to where they bunker.
She said some issues come from regional differences in VLSFO quality and attributes including viscosity, density, pour point and flash point.
“Ships have to cope with variable bunkers and costs,” Ms Wardell said. “There are many instances where the fuel did not conform and there were then issues on board.”
To date this year there have been issues with piston ring failure and cylinder liner damage, deterioration of rubber seals, deposition of solids on cylinder heads and unusual fuel odours.
There are continuing problems with sludging during purification and microbial contamination.
More issues in fuel stability, handling and combustion could come as ships begin to bunker more biofuels in the future.
Before the industry gets to that stage, there are several regulatory and market-driving elements to overcome.
Biofuels, predominantly fatty acid methyl esters (FAME), are considered to be the drop in fuel solution, particularly for older ships, said Mr Townley.
“It is not feasible to supply the whole market with bio products, nor is it possible to supply biofuel to the marine market that meets EN14214 specification,” he added.
IMO and the International Standards Organisation (ISO) are evaluating current and future marine biofuels and there are separate discussions looking at technical aspects only, not considering the legislative challenges of biofuels.
“We have generations of experience treating biofuels and overcoming their limitations, including a tendency to oxidise leading to long-term storage issues, an affinity to water and risk of microbial growth,” said Mr Townley.
In addition, FAME material can be deposited on exposed surfaces, including filter elements and flow properties degrade in lower temperatures. He said Octamar HF-10 Plus additive was developed for a lower sulphur fuels and is biofuel ready.
There should be technology for checking quality and quantities of biofuel in ship bunkers and this would be important for verifying biofuels come from environmentally sustainable feedstocks, said Lloyd’s Register EMEA global operations manager for Fuel Oil Bunker Analysis Service (FOBAS), Naeem Javaid.
He said biofuels come from various sources and feedstocks, such as food crops, including rapeseed, soybean, or biomass waste and, in the future, algae-based feedstock.
Mr Javaid said suppliers should obtain a sustainability certificate for FAME from independent bodies such as the Roundtable on Sustainable Biomaterials (RSB) or International Sustainability Carbon Certification (ISCC) to qualify their source and quality.
Forecast Technology technical sales director Stuart Hall said DNA tracing was developed for quality assurance of marine fuels.
He said this includes a unique tag and flag introduced into the feedstock and/or fuel, which can be traced through supply chains and checked on ships.
DNA tracing “helps check that the fuel delivered is as expected, linking the fuel to the paperwork,” said Mr Hall.
“It can show sustainability of the feedstock,” he continued, “and shows if there have been any changes, such as dilution or swaps.”
He expects this could bring financial and assurance benefits to shipowners for better compliance and reporting. “It reduces downtime and debate and could reduce insurance,” said Mr Hall.
Biodiesel positives and industry challenges
Biodiesel can be blended with marine distillate and is applicable with existing ships and bunkering infrastructure with minor modifications.
FOBAS global operations manager Naeem Javaid said there were benefits with biodiesel, but also challenges in emissions.
“Emissions produced from biodiesel combustion do not contain polycyclic aromatic hydrocarbons,” said Mr Javaid.
“For the blended fuels, the emissions of particulate matters, hydrocarbons and carbon monoxide are reduced as the amount of biodiesel in the blended fuel increases,” he added.
However, using biodiesel seems to emit 10% more NOx than using conventional diesel.
There could also be logistics issues with industry-wide distribution.
“Although biodiesel is the readiest alternative fuel for actual application in the shipping industry, biodiesel produced from the first- and the second-generation feedstock, such as edible vegetable oils and inedible oils, will not be sufficient to support the shipping industry to achieve IMO’s 2050 targets, especially when considered from a lifecycle perspective,” said Mr Javaid.