ExxonMobil Marine Fuels (EMMF), a world leading supplier of marine fuels, has warned that alternatives to a pure sulphur cap on fuels need to be investigated, made workable and used, if serious pitfalls are to be avoided.
Steve Walker, Global Technical Manager of EMMF, told the recent International Bunker Conference in Rotterdam that, while any move to ensure cleaner air should be welcomed, the current EC proposal for amendment of the Sulphur in Liquid Fuels Directive has yet to look in depth at the real effect it will have on the end-user.
Walker explained that, for internationally trading vessels, the current proposal would involve having three grades of fuel – 4.5 per cent sulphur bunker fuel, 1.5 per cent sulphur bunker fuel, and 0.2 per cent sulphur gas oil - in terminals and on board ships.
While acknowledging that changing from high-sulphur to low-sulphur fuel oil of the same viscosity was not a problem, he warned that changing from fuel oil to gas oil raised a number of potential difficulties, including thermal shock of fuel system components, and a loss of power and manoeuvrability as a result of the system gassing-up. “How long will it be after implementation of the legislation,” he asked, “before the root cause of a casualty is noted as loss of main engine power caused by gassing-up of the vessel’s fuel oil system
Walker added, “Of more concern is the potential safety issue of changing over boiler plant from fuel oil to gas oil firing. Many tankers have boilers to drive their cargo plant, and many LNG carriers use boilers to drive steam turbine propulsion systems. Under the proposed legislation, these vessels would have to fire their boilers on 0.2 per cent sulphur fuel whilst alongside in Europe.
“Introducing diesel into a hot furnace could be dangerous if extreme care is not taken to ensure that the boiler furnace is correctly purged of all gases. Even then, if the fuel does not light off immediately, it will vaporise and could result in a furnace explosion and catastrophic failure of the boiler itself.”
Noting also that the question of segregating and carrying three grades of fuels raised serious difficulties for shipowners, Walker concluded that alternatives to a pure sulphur cap needed to be explored. He noted that initial findings suggested that new-generation exhaust gas scrubbers, although significant in terms of capital outlay, could achieve major reductions in emissions levels while also addressing NOx emissions, provided it is demonstrated that sea water scrubbing is acceptable with respect to sea water pollution. And he said, “It is not all doom and gloom. Engines using low-sulphur fuel on a permanent basis will be able to use lube oils with a lower TBN additive package and, as a result, may be less expensive. Engine components should last longer, and fuel-testing agencies are likely to benefit from a boom in work. And, above all, if the legislation works, we will all have cleaner air to breathe.”