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Marine Propulsion & Auxiliary Machinery

Marine Propulsion & Auxiliary Machinery

Can additives overcome low-sulphur problems?

Mon 07 Aug 2017

Can additives overcome low-sulphur problems?
Low sulphur fuels bring with them a number of potential operating problems

Low-sulphur fuels present a number of operational difficulties for end users. Are fuel additives the solution?

When it comes to the global sulphur cap, everyone knows one thing: under Marpol Annex VI, IMO will cut the maximum quantity of sulphur in fuel from 3.5 per cent to 0.5 per cent on 1 January 2020. That, though, is where certainty ends.

It is a source of considerable debate whether ship operators will continue to use high-sulphur heavy fuel oil (HFO) and install exhaust scrubbers, or switch to low-sulphur bunker fuel (LSF) or liquid natural gas. Each scenario has associated issues, including implementation and running costs, so it is unlikely there will be a clear winner. But, whatever the outcome, significant disruption in the oil market is expected.

Probably the most disruptive change will be the advent of large quantities of low-sulphur fuels in a market that has been used to operating on HFO for decades. The refineries will need to fundamentally alter their approach, but so too will vessel operators whose engines are largely designed and built to run on HFO.

Low-sulphur fuels bring with them a number of potential operating problems due to their fundamentally different physical properties. Here is where fuel additives may have a significant role to play in easing the transition to a low-sulphur future.

One problem with low-sulphur fuels is that they may have a high pour point. This means wax can solidify in fuels stored below this temperature, potentially causing operational issues. Here, the use of bunker fuel additives can substantially depress pour point, allowing lower value streams to be used. By reducing the temperature at which the wax forms, fuels can be run over a much wider temperature range.

The use of additives to improve low temperature properties can help to reduce handling and transportation costs. In regions where severe winter and sub-zero conditions are prevalent, it is recommended that even Winter-grade MGOs be treated for additional protection with a diesel coldflow improver.

This additional flexibility in flow properties could be crucial to a vessel's ability to operate, particularly in cases where the fuel storage tanks may be situated close to, or next to, the ship's hull and when low external temperatures may have greater effect on the fuel.

Cold filter plugging point (CFPP) is an important performance parameter, one that in future may be included in ISO 8217. CFPP is the lowest temperature at which a given volume of a diesel type of fuel still passes through a standardised filtration device in a specified time when cooled under certain conditions. As heating distillate fuels is unadvisable, their wider use in marine applications means CFPP is likely to require more attention. Here, advanced cold-flow bunker fuel additive solutions can provide effective CFPP performance. This could help to ensure trouble-free ship operation even at very low temperatures.

At the same time, bunker fuel additives can be used to widen the gap between cloud point and CFPP, allowing refiners to raise the cloud point and maximise the economics of fuel production.

Another potential problem is that of lubricity. The use of low-sulphur distillate and heavy fuels, which have a lower natural lubricity than conventional fuels, may have the potential to cause increased wear. Lubricity additives, which have been field-proven in over a billion tonnes of fuel, are available: they provide the right level of lubricity performance even in difficult-to-treat fuels.

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