Thursday, January 29, 2009

Biodiesel and Cold Weather Issues

We have recently seen a new cold weather problem related blended biodiesel fuels.
The problem has been seen with B5 and greater blends where the diesel portion has been treated with certain lubricity agents.
What is being seen is that when the stored fuel is cold (below 15F) for extended periods of time (generally 48 hours or more) the dispenser filters will plug with an orange colored material. When this fuel filter is removed and the fuel poured out into a container that will allow it to be viewed you see an orange cloud floating in the fuel. The colder it gets the more of this material is found in the filter.
This appears to be the result of the fuel becoming more viscous as it gets colder. As the fuel becomes thicker it will begin to reduce the pore size of the filter media. As the pore size gets smaller, the filter begins to filter out the lubricity additive and the filter will concentrate it until the restriction is such that little or no fuel will pass through the filter.
This is a separate issue from gelling. The fuel when tested can have a very good CFPP or LTFT number and still see this problem.
If anyone has seen this issue, please let me know and I can offer suggestions for how to deal with this problem.