World Bunkering > News > Autumn 2009 > Detecting the presence of chemicals

Geoff Jones

Blending fuels with cutter stock to meet low-sulphur limits can lead to an increase in the levels of catalytic fines, and influence stability and ignition/combustion characteristics as well as introducing waste chemicals. It is debatable whether chemicals of non-petroleum refining origin have actually been present in fuels for many years. There is no doubt that improvements in analytical capability have made it easier to look for and find these waste chemicals. It is now possible to determine concentrations of the many chemicals present in bunker fuels, both those occurring naturally (or as part of the refining process), and those introduced during blending.

The need for forensic analysis

The need to blend cutter stocks of variable quality with poor quality residuals has given rise to many instances of waste chemicals being detected in bunker fuels. Consequently, the need for ‘forensic’ methods of analysis has been brought to the forefront for both shipowners and fuel testing agencies.

Using GC MS effectively

Heavy bunker fuels naturally contain many chemicals, ranging from relatively low to very high carbon number compounds. The high molecular weight compounds are critical factors for “direct injection” Gas Chromatography Mass Spectrometry (GC MS) test, a favoured analytical technique. A Gas Chromatograph, containing a highly specific separation column, is linked to a mass spectrometer detector to identify target chemicals in petroleum products.

Specific sample preparation is needed prior to injection into the GC MS, otherwise the chemicals for identification will be masked by many others present in the bunker fuel. Solid phase extraction (SPE) and derivatisation techniques are often required to ensure that target chemicals are detectable by GC MS.

“Head Space”

Another GC MS technique is “Head Space” GC MS, ideal for determining Volatile Organic Compounds (VOCs), as it can reduce analysis time and be performed prior to the fuel being burnt. Head space is a very convenient technique for volatile chemicals such as styrenes, and many chlorinated hydrocarbons such as methylene chloride, chloroform, carbon tetrachloride, and alcohols etc, the presence of which as waste may result in marine fuels failing to comply with ISO 8217.

It is an appropriate and cost-effective methodology, protecting shipoperators’ interests. Styrene and DCPD can be found in marine fuels at levels over 0.1%, although more serious waste chemicals, eg chlorinated hydrocarbons, are often at very low parts-per-million levels, and have been found in around 3% of fuels screened by Lintec worldwide.

The real challenge now is to link the presence of chemicals to actual machinery damage, in time to develop and refine a limit for chemicals for inclusion in a bunker fuel specification. To achieve this, all sectors of the marine industry will need to work together.