Friday, August 18, 2017

Damaging Catalytic Fines Need to be Extracted from Vessel Fuels

Pre-Treatment of Heavy Fuel Oil Can Reduce Engine Wear
Shipping News Feature
WORLDWIDE – Earlier this year the International Organization for Standardization (ISO) published its usual 5 year standard revised edition of its ISO 8217 specifications for marine fuels, in which it still maintains a 60 mg/kg limit for 'catfines'. These are the catalytic fines, the hard aluminium and silicon oxide particles that are normally present in heavy fuel oil and this 60 parts per million level is regularly broken when ship owners purchase fuel oil with higher concentrations. Meanwhile major engine manufacturers recommend less than 15ppm when the oil enters the engine which means the necessity for an efficient treatment method prior to combustion to avoid long term engine damage.

A test conducted just a few days ago by the Lloyd’s Register Fuel Oil Bunkering Analysis and Advisory Service (FOBAS) takes the debate to a new level. It shows that a number of bunker samples delivered in Fujairah, a strategic bunkering port, contained aluminium and silicon (Al + Si catfines) at levels ranging from ‘above 75 mg/kg up to nearly double, at 139 mg/kg.’ Considering what damage catfines can do to engines, this is a big deal.

These catfines are not a naturally present phenomenon but something added in to the refining process to enhance the ‘cracking’ or the process which converts high-boiling point, high-molecular weight hydrocarbon fractions of petroleum crude oils into more valuable gasoline, olefinic gases and of course oils for marine use.

As exceptional as the latest findings may be, they underscore the potential of even more uncertainty, and thus risk, that needs to be addressed: the FOBAS analysis states that ‘Al+Si at 75mg/kg can be difficult to reduce but may be manageable; however Al+Si at levels up to 139mg/kg would prove extremely difficult to bring down to acceptable levels for engine entry (<15mg/kg). Carry over of abrasive Al+Si material at high levels may lead to damage to fuel pumps/injectors and cylinder components’.

Catfines can occur at high concentrations in slurry oils, the product drawn at the bottom of the catalytic cracking fractionator. It’s because these slurry oils are highly aromatic and have a low viscosity, that they are an ideal blending component in heavy fuel oil production. The concentration of catfines varies according to the quantity of slurry oils used in the blending and the quantity of catfines already present in these same slurry oils thus the unpredictable levels. By nature, catfines are hydrophilic, i.e. they are attracted to water molecules and tend to stick to them, and this combination catfines/water is difficult to extract from the fuel at the separator levels.

With smaller particles, the catfine/water combination will emulsify and hamper purification performance. Compounding the problem is the fact that catfines come in varying sizes, fewer particles that are larger in size will be more readily ejected. High concentrations of minute catfine particles pose a much greater – and no less real – threat. According to FOBAS data, purifiers nowadays operate at only 60 to 65% on average.

At the same time, this hydrophilic nature of catfines offers a solution for reducing risk. Using a surfactant-based fuel treatment solution that facilitates water separation will ensure that a significant portion of the catfines captured by water molecules in the fuel tanks can be drained off along with the water. Also allowing thorough settling of the fuel will further reduce the counts of catfines, especially large particles. In addition, the right fuel treatment solution will also isolate contaminants, disperse agglomerations that lead to sludge, and stabilise as well as homogenise the fuel.

The net effect of this ensures that cleaner fuel enters the line cleaner resulting in more efficient combustion, plus a lower catfine count, enabling the separator to eject remaining catfines and contaminants more effectively, and ensuring the engine is fed a healthy diet. The old ‘prevention is better than cure’ adage applies here, the cleaner the fuel when it enters the separator, the more longevity the engine components will enjoy, cutting repair times and costs.

The FOBAS report is just one of many concerned with the quality and regulation of fuels in industrial and marine uses, joining studies by such as those by MAN Diesel and Turbo. With the looming of the 2020 sulphur cap, bunker companies and vessel operators face the problems of ensuring supply security and consistent quality, especially with future demand projected at up to two billion barrels a day. Removing sulphur from fuel oil means either hydrocracking or blending or a combination of both. Downstream, this could very well mean higher prices for uncertain quality along with the risk of fuel incompatibility and other problems that can lead to unexpected stoppages.

Reports and findings that meet strict standards, like this recent FOBAS spot check, provide an invaluable heads up. They also underscore the importance of allowing for sufficient safety margins – and the advantages of preventing risk over repairing damage. Olivier d’Olne, General Manager and Group Technical Director at Aderco Marine which specialises in improving fuel performance, commented thus on the issues:

“What is a Chief Engineer to do when the bunker analysis comes in three days out at sea with [catfine] numbers far outside the confidence range. Just to be on the ‘safer’ side, Shipowners and Managers will find themselves saddled with additional procedures, maintenance and costs due to increased constraints on fuel handling and management (extended fuel settling and purifying times, more frequent draining, elevated heating, greater care with backwash fuel oil) and a heavier workload on fuel separators. More prevention will be key in addressing the uncertainty and the challenges ahead, from catfines to sulphur emissions as well as other non-fuel-related issues. Along with a holistic approach to applying the right tools from a shared toolbox.”

Photo: Courtesy of Parker Kittiwake which produces catfines test kits.