Dr. Vis is a Phd. in metallurgical engineering, holds a Masters in internal combustion engineering and a Bachelors in marine engineering. He has worked as chief engineer on ships, senior surveyor to the classification society American Bureau of Shipping. Since 1991, he has been associated with the materials evaluation activity of metals, composites and petroleum products. It is this unique combination of all three facets that has propelled him as one of the top experts in this field.
Viswa Lab wishes to share our knowledge on this subject.
First of all, styrene in isolation does not cause problems, unless these levels are very high.
Similarly, DCPD in isolation does not cause problems.
However, styrene and DCPD and Indene (which is being seen more, lately) together do seem to cause machinery problems. The problems can result in seizure of main engine fuel pumps (since these substances tend to polymerize) or in some cases, choking of main filters. Both problems can result in sudden stoppage of vessels engines which can result in serious safety situations.
A question often asked is the levels at which these contaminants can be considered unsafe.
In order to answer this question, the method of detection of these contaminants should also quantify the contaminants. Methods of sampling also do matter. A headspace sampling may give values one third or one fourth of the total values. We have seen this, particularly with respect to the presence of Styrene/DCPD. Also, headspace will capture only substances that vaporize at the sampling temperature. All other contaminants perhaps 80% will not be captured.
How does precise quantification help?
This helps with empirical studies in determining the levels at which these contaminants cause problems. It is important to understand empirical studies and limits based on empirical data.
Our customers report to us on problems experienced by them, say, fuel pump seizures. When we carry out GC-MS studies on these fuels (using full fuel injection in GC columns), we see that the contaminants are present above a certain limit say, greater than 100 ppm DCPD plus 100 ppm Styrene plus 100 ppm Indene. We then arrive at the empirical finding that a fuel containing DCPD, Styrene and Indene (all at the same time) at levels greater than 100 ppm is likely to cause machinery problems.
Such empirical conclusions are an accepted method of research in every field of science.
One important point to note is that the quantified numbers for the contaminants have to be reasonable accurate. Headspace analysis will not provide this, nor any method in which only a qualitative statement can be made. The other important point to note is that all three contaminants have to be present simultaneously.
Interested parties and, sadly some labs also contribute to the obfuscation of the issues connected with contamination. Empirical conclusions are scientifically acceptable. Quantification of contaminants is a painstaking activity achieved by direct liquid injection - it cannot be substituted by headspace sampling which can only give partial and imperfect values. All testing labs know this. There is no "secret proprietary methods" - only the difficult and painstaking one, which all labs can follow.
The other attempts at obfuscation, such as, testing the fuel at various intermediary stages such as refineries, fuel terminals, supply facilities, barges are virtually impossible to enforce. Those who are suggesting this know that this is unworkable.
One final question - Why are the refineries not coming out with a clear statement on how the bunker fuels get contaminated, usually with refinery wastes? After all, they know the whole game.
With regard to Styrene and DCPD and Indene, we would like to add the following comments:
Pyrolysis gasoline is a benzene rich byproduct of the ethylene manufacturing plants. Traditionally pyrolysis gasoline is blended with motor gasoline because of its high octane number. Only small portions are blended owing to unacceptable odour and its gum forming tendencies. When this pyrolysis gasoline is dimerised and distilled, first the lighter hydrocarbons, then Benzene, Toulene, o-Xylene and Styrene, then DCPD and finally heavier hydrocarbons (like Indene) are separated. Styrene and DCPD have gum forming tendencies at high temperatures. Usually, presence of Styrene and DCPD indicates possible presence of other gum forming compounds in any form (monomers, dimmers, trimers, tetramers etc). CPD is a monomer and DCPD is a dimer.
Please do not hesitate to contact us with any questions.
Dr. Ram Vis,
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