The Black Art of Blending
28th May 2012 04:26 GMT

As rising costs cast the spotlight on bunker fuel, blending practices have become more advanced and complex. Indeed, the process of blending plays a critical role in helping ship operators to receive fuel that is not only fit for purpose and safe to use, but also offers the best price per metric tonne of fuel in terms of energy content. Recently, a variety of factors have influenced the blending process and this has had an impact on the composition of fuel delivered to ships.

The product in bunker tanks on board of ships is the result of optimization between production costs and compliance with customer specifications. The main target blend specification for bunker fuel in the past was initially viscosity, reflected in product names such as IFO180, IFO 380 etc. As refining techniques became more and more sophisticated density also became a critical blend target. This often required blending heavy grades of residual product with more costly distillates and cutter stocks to enable the fuel to be used safely. In this sense, blending was primarily a means of producing fuel that was both economical (using the least amount of cutter stock to meet specification targets) and fit for purpose.

With the development of marine fuel standards such as ISO 8217, fuel blends also need to meet certain criteria that set out the parameters and general guidelines as to what constitutes acceptable fuel quality. At its core, blending needs to account for key qualities of fuel to be considered fit for purpose, stable with good ignition quality and combustibility. It is vital that all cutter-stocks used are compatible with the nature of the residual base stock in order to ensure the stability required of the overall blend is achieved.

In recent years, changing environmental regulations have played a big part in shifting blending priorities and this has had consequences throughout the supply chain. Where blending was previously meant to help ship operators balance costs with functionality, growing sulphur regulations have meant that the sulphur content of the fuel has become a critical parameter in the blending process.

Low sulphur fuels may have different qualities from high sulphur fuels and may create problems for some engines if the ignition properties of blended fuel are impacted due to an unusual density/viscosity relationship as defined by the CCAI in ISO 8217: 2010. Blending to produce low sulphur fuel can also result in fuels with poor stability characteristics and possibly higher cat fine content if slurry oils are used as cutter stock. This makes it especially important for suppliers and ship operators to test fuel that has been blended to meet sulphur requirements and to also ensure that the fuel meets international marine fuel oil standards.

Other trends such as bio-derived components becoming increasingly more popular in land based fuel applications over the years due to for example lower SOx and PM emissions, the likelihood that it could become present in the marine fuel supply chain may also increase. Fatty acid methyl ester,or FAME may pose adverse consequences when used in ship engines, the full effects of which are still being studied. ISO 8217:2010 does not allow the use of FAME, however it is difficult to avoid completely due to FAME being surface active, sticking to metal or glass surfaces. The risk of cross contamination where supply chain terminals, barges and trucks handle both marine fuel and bio-diesel are therefore real.

While it is important for ship operators to meet their fuel requirements while minimizing costs, it is vital that the blending processes in the marine fuel supply chain not be overlooked. The costs of improper blending are very real and can result in off-spec fuel which in turn may be difficult for onboard handling and/or damage ships' engines. Fuel quality is constantly changing to meet the shifting demands of regulatory and economic forces and the supply chain needs to evolve with these effectively.

Douglas Raitt,
28th May 2012 04:26 GMT

Comments on this Blog
Enel Reina - ACP
30th May 2012
great article, we recently had been hit by a fuel with alkylphenols and Alcohols.
Marco Antonio Costa Tritto
25th June 2012
Douglas, very nice article touching one vital aspect of our bunker industry today. To meet the specs we can see no more tanks in the terminals but 'caldrons' in certain sense.Besides we have a lack of information so far about what the consequences in burning the bunker fuel got in those 'caldrons'. It is true that the ISO 8217 says that the product has to be fitted for using as bunker fuel but the question is: how to know deeper in advance in a broadly view if what is being mixed would be fitted or not for using considering the lack of more information that we have today? In what proportion this or that component can harm indeed the engine in the end? It is not an easy task, really not cause a lot of folklore could be created but the sincere cooperation between the shipowners (showing the outcome of its use in their engines) and its suppliers (building a database of blending) could improve this knowledge.
Enel Reina - ACP
26th June 2012
I´m reviewing my actual fuel contract and besides going wth the new ISO 8217-2010, what else can be done in order to detect on time those harmful chemicals, that doesn´t show up in a FQT and affect directly to mechanical components of the engines.
khalid abdu
28th June 2012
Dear Douglas.
Thank you for your valuable information, I have some tec questions
Please, send me an e-mail to

Khalid abdu
khalid abdu
29th June 2012
Dear Douglas.
Thank you for information . I have a question for you
I want to produce IFO 180, and sell it is it feasable to use spent oil
or surplus Lube oils?
My cutting stock is refined crankcase oils (No H2o,benzene,dirts,etc)
Can I add Gas oil to my final product in order to have IFO 180?
If yes, what is the percentage of mixture? or
Can I added gas oil by 12 % to have IFO 180?
Looking forward to your answer.
Sunil Kumar
7th August 2012
Dear Douglas,
the concern you've raised is bit vital stuff and thanks for flashing such awareness. However i do feel this may become serious & countable in case bio diesel production boosts up in coming years and make its availability. Anyway i dnt think any issues due to FAME in the Middle East as the biodiesel production here is still a nightmare.
Sn Sunil

Comments have been closed for this article.