ASTM | Springboard Biodiesel

Description of test
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‍Free and total glycerin levels within the finished biodiesel are tested under the D6584 specification and are important to biodiesel producers.

Free glycerin is an indicator of improperly washed fuel. If the amount of free glycerin exceeds the ASTM specified limit of 0.020% by mass, then it is likely to separate or solidify over time. This is very likely to result in excessive deposits left on valves and engine components as well as clogging and fouling in fuel pumps and lines.

Why the BioPro passes this test:

Because the BioPro line of biodiesel processors employs a three stage washing system with two stages that include vigorous agitation, it has been designed to pass the Free Glycerin test. In fact, we have never seen a fuel sample that was washed in a BioPro that has failed the test for free glycerin.
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The primary reaction that occurs to transform oils and fats into biodiesel is called a transesterification reaction. The Total Glycerin test indicates how complete the transesterification reaction has been. Fuel that does not meet the specified ASTM maximum value of 0.24% for total glycerin is not as likely to damage an engine as fuel that has excessive free glycerin, however there are negative effects to a high total glycerin number. A high level of total glycerin can lead to cold flow problems as well as a higher viscosity fuel, which can inhibit the spray pattern of a vehicle’s injectors and contribute to carbon buildup and inconsistent starting in cold weather.

Fortunately, the BioPro runs a two-stage duel catalyst series of reactions with the capacity to perform an 80/20 reaction as well. The BioPro processors precisely monitor reaction temperature as well as employ a powerful motor dedicated solely to agitating the feedstock during the reaction process. If the user follows the straightforward directions given in the owner’s manual, he will successfully pass D6584. Numerous tests both in-house and by customers in the field have proven the BioPro consistent ability to meet or beat the total glycerin spec.

Description of test
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The ASTM D664 test determines how acidic a particular sample of fuel is. It is entirely acceptable for fuel samples to be slightly acidic. The limit set for fuel acidity is 0.5 mgKOH/gram. This means that it takes 0.5 milligrams of Potassium Hydroxide to neutralize the acids in one gram of biodiesel.. The TAN is an indicator of aged fuel that is likely to develop insoluble organic compounds that could present a risk of polymerization and clogging of fuel lines. It also signals acidic fuel that may have solvent properties that are more aggressive than properly processed biodiesel. This fuel poses a risk to various seals, lines, and elastomers in the fuel delivery system. There are two common reasons that a sample of fuel maybe too acidic.Exhaustion of the fuel shelf life. As fuel begins to oxidize over time, (this process is exacerbated by the presences of sunlight, microbes, trace metals, temperature extremes, etc) there are numerous acids that form as byproducts of the oxidation. Freshly made fuel made in any type of processor would be unlikely to ever fail the TAN test for this reason. (See Oxidative Stability)Free fatty acids that are generated during the fuel washing process. Free fatty acids are generated in this process when molecules of soap in the fuel are neutralized by the action of an acid. The neutralization of one molecule of soap creates one molecule of free fatty acid. When fuel is washed using very acidic water, or dry washed using only an ion exchange resin, it is likely that it will become too acidic to meet the required ASTM specification.

Why the BioPro passes this test:

Because the BioPro™ processor performs a wash with fresh or only slightly acidic water, meeting this specification has never been a problem that typical BioPro™ customers have had to deal with. Typical test results have come in at only a fraction of the required specification.

BioPro™ customers that have purchased a SpringPro™ T76 Drywash system will find that they are superbly equipped to meet TAN. Not only does the 2 stage reaction process of the BioPro™ processors result in a lower than usual initial soap level in the raw fuel, but the SpringPro T76 Drywash system itself is specifically designed to minimize TAN. It does this through the use of a duel tower lead/lag setup, which is tailored for the use of an absorbent media in the lead column to remove bulk soaps and an ion exchange resin in the lag column to polish out residual contaminants. This setup and configuration has proven effective for easily meeting the TAN where other systems cannot.

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