|Do you know what’s in your customers’ storage tank? Could you explain to them what today’s heating oil is? You could say a milkshake of petroleum or explain the truth that it is a blend of petroleum hydrocarbons, derived from different crude stocks found around the world and blended to meet ASTM D396 then mixed with a new generation of mono-alkyl esters of long chain fatty acids derived from vegetable oils or animal fats that meets ASTM 6715.
The oil heat industry is changing again, not with the equipment, but with new blends of diesel fuel. The customer assumes the storage tank is clean particularly when you have always delivered their oil. After decades of mixing, blending and cracking, Mother Nature has a way with time of altering the effects of what man has done. Time, gravity, evaporation and chemical reaction can interfere with our attempt to change organic matter.
The reason for proper fuel filtration is to assist in the term referred to as “sick tank syndrome,” where a tank is adjusting from one form of diesel fuel to another. There are many feedstocks from many different countries and many different refining methods, and we have not had the time to determine how these different blends age or transform fuel already in the tank. Our industry stores the heating oil until needed unlike road fuel that consumes and refills constantly.
Currently in the U.S., heating oil for residential use has an average sulfur content of about 0.20-0.25 percent. The ASTM D396 limit for No. 2 heating oil is 0.5 percent sulfur by weight. Considerably higher levels have been allowed, however, and regulations vary by state and area. Only since the 1990s has heating oil had a standard for low sulfur diesel (LSD) at 500ppm, but it’s more expensive and considered a premium product. However, 40 CFR Part 80, Subpart 1, the primary standard for diesel fuel producers, is required to reduce the sulfur content to 50ppm called ultra low sulfur diesel (ULSD), which will be phased in for all diesel fuel from now through 2014.
The removal of the sulfur content in future heating oil, and the blending of the biodiesel with 10-30 year old tanks, will cause problems with sludge, water and sediment because of a cleaning process that occurs in the customers’ tank using these new fuels. “Biodiesel provides a cleaning effect and does have a tendency to dissolve or loosen some sediment that can be deposited in tanks and fuel systems from years of conventional diesel fuel or home heating oil use,” according to the National Biodiesel Board.
NORA/BNL research project (Ref 4) concluded, “The instability of fuel oil and sludge formation are related issues that can not be separated. Contamination due to exposure to air, dust, humidity and other environmental factors combine with the chemical nature (and inherent instability) of the fuel as it was refined. Stability always degrades with time. It is a related to the inherent instability of the product, how fast it is transported, the storage time and the use or nonuse of fuel stabilizers. Product roll-over and mixing with older product is also a factor.”
With most new tank or equipment installations, single pipe systems are favored, which allows the heating oil to settle and revert back to its original form, whether petroleum, vegetable oil or fat. With oil prices rising and world demand increasing, the decade of the 2000s will be the age of biodiesels.
Biodiesel is a generic term for clean burning alternative fuels for diesel engines that are derived from renewable feedstocks such as soybean, rapeseed, canola, palm, recycled cooking grease, animal fats and many more. In the U.S., soybean oil is the primary feedstock used to make biodiesel because we are the largest soy producer in the world.
The common ingredient in all biodiesel is (in some form) fat. Oils are just fats that are liquid at room temperature. These fats or triglyceride are made up of carbon, hydrogen and oxygen atoms. Biodiesel is not pure vegetable oil, rather a series of chemical reactions of raw fat or oil through the process of transesterification. A fat or oil is first purified and then reacted with an alcohol, usually methanol or ethanol, in the presence of a catalyst such as potassium hydroxide or sodium hydroxide. The process leaves behind two products, methyl esters (biodiesel) and glycerin, a common ingredient in soaps, pharmaceuticals and cosmetics. Biodiesel is a liquid that varies in color between golden and dark brown depending on the production feedstock. Pure biodiesel is called B100 because it is all biodiesel. Our industry is fine with B5 (5 percent biodiesel 95 percent ASTM D396 LSD heating oil) and a limit of B20 (20 percent biodiesel 80 percent ASTM D396 LSD) and is recognized as Bioheat™ fuel.
B100 cannot presently be treated successfully with conventional winter fuel additives and biodiesel supply is scarce. B100 is adjusted with a combination of kerosene and cold flow improvers designed for generic fuel and would cost more. Biodiesel not only is practically immiscible with water, typically contains less than 15ppm of sulfur and is an excellent lubricant, but also is a solvent with the ability to loosen deposits built up in the storage tank causing the fuel filter to become jammed with newly freed deposits.
Biodiesel is hygroscopic and will always have a tiny bit of water (about 1,200ppm) absorbed from the atmosphere, if from nowhere else, and is slightly heavier than petroleum diesel with a gravity value of 0.88 versus 0.85 and will gravitate to the bottom of the tank. Water will become more evident in the storage tank and can create microbes. These microbes form a slimy colony that lives at the fuel/water interface. They grow quite rapidly in warmer temperatures. They can even grow in cold weather when fuel tank heaters are installed. Parts of the colony can break off and clog the fuel lines and fuel filters. It is possible to kill this growth with a biocide treatment, but biocides attack the cell wall of microbes resulting in lysis, the death of a cell by bursting. The dead cells then gather on the bottom of the fuel tank and form sludge. Quality fuel filtration is your only defense for the burner’s protection.
Biodiesel is biodegradable, meaning that it can decompose as the result of natural agents such as bacteria. According to the EPA, biodiesel degrades at a rate four times faster than conventional diesel fuel.
With the seasonal use of heating oil, the new blends delivered and the length of time the product has to sit and settle in the storage tank, understand the importance of installing a quality fuel filter with enough filtering surface and capabilities to protect the burner.
Providing the customer with quality low sulfur fuels that are renewable is great, but providing them with the best fuel filtration to protect the equipment from their own storage tank will benefit the customer by giving them reliable heat with oil derived from plants.
Ref 4. Proceedings of the 2002 National Oilheat Research Alliance (NORA) Technology Symposium, BNL report 52670, August 2002, Paper No. 02-03, Maximizing Fuel Oil Quality and Heating System Performance, Wai Lin Litzke, Brookhaven National Laboratory and associated presentation viewgraphs provided at the NORA Technology Symposium at the Oilheat Visions Conference, August 19-20, 2002.