Biodiesel and Cold Weather meet in Minnesota

Biodiesel and Cold Weather meet in Minnesota

The Minnesota Department of Agriculture recently released (February 15, 2009) a report to the legislature regarding the states mandated biodiesel program and the cold weather issues it has caused.

Starting in September 2005 Minnesota required that virtually all diesel fuel sold in the state contain at least 2% biodiesel. This level is supposed to be raised to 5% in 2009, 10% in 2012, and finally 20% in 2015.

This report by the Governors “Biodiesel Task Force” created in 2003 shows that there a number of significant problems with using biodiesel blends, particularly in areas subject to long periods of cold weather.

Some of the issues noted in the report:

· Discussion indicated at least fifteen cases of unusual filter plugging in commercial trucks this winter for which the cause had not been determined. Discussion of possible causes included engine manufacturers’ reduction of truck filter sizes (from 10 to15 microns down to 2 to 5 microns), paraffin from diesel, glycerin from biodiesel, water contamination, biotic contamination as a result of ultra-low sulfur diesel levels plus water contamination, and vehicle designs in which the fuel filter is located away from the engine.

· Discussion that existing cold flow test procedures are not sufficiently predictive of the
cold temperature performance of diesel fuel with or without biodiesel. ASTM International and other organizations at a national level must develop new test methods that are more predictive of the cold weather performance of diesel fuel and biodiesel blends.

· Variations in seasonal availability of fuel were also discussed, specifically routine shortages of diesel fuel at terminals in the fall leading to the practice of bulk plants and fleets buying and storing fuel in the late summer for use in the fall and early winter months when shortages of diesel are anticipated. Such stockpiling of B10 or higher could result in problems in above ground tanks.

· The suggestion was made that the Task Force discussions should freely address the availability and quality of all winter fuel in the state instead of being confined only to biodiesel. Given recent changes in the diesel industry, including biodiesel, low-sulfur diesel fuel and smaller fuel filter pore diameters, a wide range of issues regarding equipment and diesel fuel with and without biodiesel must be addressed.

Laboratory testing has indicated that blending with number one (#1) diesel at 50/50 rate produces results similar to treating with additives but the #1 fuel is at a far higher cost.

There is also a concern over whether the current testing (e.g. Cold Point (CP), Cold Filter Plug Point (CFPP), Pour Point (PP), Low Temperature Flow Test (LTFT)) done to assess cold weather operability characteristics of diesel fuel are adequate for testing biodiesel blends.

Unfortunately this discussion has been complicated by many factors including the change from Low Sulfur (LSD) to Ultra-Low Sulfur diesel (ULSD), that diesel fuel changes seasonally, the fact that biodiesel derived from different base oils have far different characteristics, that transportation and storage affect quality, and that materials will tend to precipitate out of biodiesel when it cold for extended periods of time.

To read the complete Minnesota Report to the Legislature please click here: Report to the Legislature February 2009

Please post your comments, questions, ideas, and thoughts.

Diesel Doctor

Copyright 2009© - William Richards

Asphaltene's and Plugged Fuel Filters

Asphaltenes and Plugged Fuel Filters

Asphaltenes in diesel fuels are becoming a much larger problem since the introduction of Ultra-Low Sulfur Diesel (ULSD - S-15) fuels.

There are actually several problems that have come together to cause the filter plugging black slime we so often see today.

Asphaltenes are highly polarized long chain components in crude and the heavier refined oils. Under certain circumstances these compounds associate themselves to form complex colloidal structures.

In Low Sulfur Diesel (LSD – S-500), High Sulfur Diesel (HSD – S-5000) and heating and bunker fuels the higher aromatic content of the fuel tends to discourage the formation of the complex colloidal structures limiting the problem.

However the EPA mandated reduction in aromatic content in ULSD has allowed this problem to happen sooner, more often, and in cooler temperatures than had been seen previously.

Asphaltenes agglomerate into an oily sludge. This problem is made worse when water is added to mix.

Petroleum and bio-derived fuels all hold water suspended in them, ULSD unfortunately holds approximately twice as much as the LSD and HSD fuels we had seen prior to June of 2006. Biodiesel (B100) can hold ten (10) times as much water as LSD and HSD, so even small amounts of biodiesel blended with diesel fuels dramatically increases the amount of dissolved water present.

Blending of fuels refined from different crude stocks further exacerbates this problem. Also, warmer temperatures in storage or due to the recirculation of fuel by the engine fuel system speeds the process and thickens the sludge.

Fuel that looks perfect going into a clean tank can develop tiny asphaltene droplets in a matter of hours when recirculation temperatures exceed 140°F (note: some newer engine fuel temperature as it exits the head exceeds 210°F). These pin-prick sized droplets can plug a 10 micron fuel filter in 3ooo to 4000 miles or less 50 hours of operation.

Many people mistakenly see this as a biological (bacteria and fungi) problem, however in the majority of cases the accelerated biological growth is the result of near perfect growing conditions that allows this rapid growth after the filter plugging asphaltene material has blocked the filter(s).

Keeping the water out helps, but the real solution is a thermal stability additive, a oxidative stability additive, together with a water dispersant.

Please comment with your experiences, suggestions, and or questions.

Diesel Doctor

Copyright 2009©

Fuel and Water - They Don't Go Together

Fuel and Water

They don't mix and you shouldn't try to make them.

One of the more interesting characteristics that is shared by diesel, biodiesel, gasoline, and gasohol is that all these fuels are hygroscopic.

Hygroscopy is the ability of a substance to attract water molecules from the surrounding environment through either absorption or adsorption.

Some examples of this phenomenon are that Ultra-Low Sulfur Diesel (ULSD) will hold approximately 2/10 of 1% dissolved water. This may not sound like much, but if you do the numbers they show that 2/10 of 1% equals 2 gallons of water dissolved in 1000 gallons of fuel. If you work backwards, that would equal 1 gallon of water in 500 gallons of fuel, or 1 quart (32 ozs.), in 125 gallons, or 1 pint (16 ozs.), in 62.5 gallons, down to about 8 ozs. in a 30 gallon tank.

That much water can cause severe corrosion of fuel system components such as injectors, pumps, connectors, and even metal fuel tanks.

That level of water speeds the oxidation and chemical breakdown of the fuel.

That level of water is enough to encourage the growth of bacteria and fungi.

One of the most insidious characteristics of water dissolved in fuel is that the fuels ability to hold water is dependent on temperature. Simply put the warmer the fuel (up to a point) the more water it hold.

What often happens is that fuel stored for example at 60°F will absorb that 2/10% water then as the fuel in a vehicle gets colder more and more of that water is pushed out of the fuel becoming liquid water droplets.

These droplets can collect in filters and if the temperature drops below 32°F those droplets turn to ice crystals quickly plugging filters and causing other problems.

Fuel at 28°F can hold approximately 1/2 as much water as fuel at 60°F.

This means that you can have clear fuel with no liquid water at 60°F and if the temperature drops sufficiently, you can have large amounts of free water suddenly appear as the temperature drops.

To make matters worse biodiesel can pickup and hold 10 times as much water as ULSD. So adding 2% or 5% biodiesel to regular diesel can dramatically increase the level of dissolved water.

Gasoline containing Ethanol suffers the same problem.

A 10% Ethanol blend can hold 3.8 teaspoons of dissolved water at 60°F.

However if more water is added or if the temperature drops significantly this fuel suffers a problem called "Phase Separation".

In Phase Separation the dissolved (or liquid) water binds to the Ethanol and this Water/Ethanol mixture will drop out of the fuel.

This has a series of negative affects on the fuel quality and can have catastrophic effects on engines.

We will discuss more about this later.

We look forward to your comments and questions.