Biodiesel Cold Soak Filterability - ASTM D6751 Annex A1

New ASTM Biodiesel Test Specification for Cold Weather Operability

The American Society for Testing of Materials has recently added a new test requirement to the D6751 Biodiesel Specification.

This new requirement is referred to as ASTM 6217 or as Annex A1 of ASTM D6751– Cold Soak Filterability.

Cold Soak Filtration Analysis is defined as: The time in seconds that it takes for cold soaked biodiesel to pass through two 0.8 micron filters and the amount of particulate matter expressed in milligrams per liter (mg/l) collected on the filter.

What does this mean? When biodiesel is stored in temperatures below 40°F for extended periods of time, certain components will precipitate (fall) out of solution and fall to the bottom of the storage tank. This precipitate will build in a thickening layer at or near the tank bottom. In general the colder the temperature and the longer the biodiesel stays at a given temperature, the more material will fall out.

This material can very quickly plug filters and shut down engines, usually at the worst time.

What is this material? It can have to do with the feedstock from which the biodiesel is created. Certain feedstocks, particularly Used Cooking Oils (UCO), Waste Vegetable Oil (WVO), and Animal Fats (Tallow) will produce high levels of precipitate. The material can also be due to incomplete removal of glycerin during the transestrification process.

This new test is a positive step in making biodiesel a more consistent user friendly product.

Diesel Doctor

Copyright 2009© - William Richards

Cetane Number – What it is and Why it’s so Important

Cetane Number – What it is and Why it’s so Important

Cooperative Fuel Research Engine (CFR)

Cetane is a measurement of a diesel fuel ignition and or combustion quality. This Cetane Number or CN is one of several components that determine the quality of diesel and biodiesel fuels. This number is used for light and middle distillate fuels. For heavy (residual) fuels Calculated Ignition Index (CII) and Calculated Carbon Aromaticity Index (CCAI) are used.

In some ways this measurement is similar to the Octane Ratings given to gasoline. In its simplest terms Cetane Number measures the delay between the start of fuel injection into the combustion chamber and the beginning of compression ignition (Auto-ignition).

In medium and high speed diesel engines (this all automotive and truck engines) fuel needs to have a CN between 38 and 55 to operate. In general the higher the CN number, the better for the engine and for emissions. However raising CN above 55 currently offers little if any benefit.

In the US the group setting the standards for CN is the American Society for Testing of Materials (ASTM) and currently the minimum is 40. While diesel engines will start and run with 40 CN fuel, they do not run as efficiently as they will at a higher number.

In Europe the European Union (EU) has systematically over several years raised the minimum from 38 to the current 51. This has allowed engine manufacturers to produce more efficient engines with lower emissions and better economy. Most fuel in the EU has a CN of 55 or even better.

Cetane Number is measured using a very expensive and arcane Cooperative Fuel Research (CFR) engine and a process that very complex.

You can also measure CN using an Ignition Quality Tester (IQT) which is somewhat less complex, but still quite costly.

There is a third measurement called Cetane Index (CI) that measures density and distillation range of the fuel and through a calculation provides a measurement. This method will calculate a reasonably accurate number for the refined diesel.

The problem is that today most diesel fuel uses additives to reach the desired Cetane Number and additives do not affect the density, thus the CI of a fuel containing additives is not accurate.

Some of you may have seen a device that looks like a battery fluid tester (a hydrometer). These devices are not capable of determining CN or CI with any accuracy.

You can raise CN by altering the refining process or through the use of Alkyl nitrates or di-tert-butyl peroxide additives. NOTE: Remember that additives do not raise CI.

Also, biodiesel, depending on the base oil from which it is derived has a natural Cetane Rating of 46 to as high as 60.

With the advent of Pilot or Multiple Pulse fuel injection, Cetane Number becomes more important than ever. The delay in auto-ignition (CN) affects the combustion timing, which has a significant effect on power output, fuel economy, and emissions.

Raising Cetane Number together with Improving Fuel Atomization is the fastest way to improve fuel economy and reduce emissions through the use of correctly formulated additives.

Please post your comments, ideas, and suggestions

More information at: http://www.lcbamarketing.com/ - Click on Fuel School Articles.

Diesel Doctor

Copyright 2009© - William Richards

Biodiesel Confusion New Labeling Requirements

Biodiesel Confusion

The diesel fuel/biodiesel market has recently gotten a lot more confusing. We now have another Federal agency involved in the diesel fuel marketplace.

The Federal Trade Commission (FTC) has now created labeling requirements for diesel, biodiesel, and biomass based diesel.

These requirements have wide ranging consequences for all diesel fuel users.

First, diesel fuel may now contain up to 5% biodiesel or biomass-based diesel with no retail labeling required as long as the blended product meets ASTM D975 (note: ASTM D975 is being changed to allow up 5% biodiesel/biomass-based diesel to be blended as part of a diesel fuel).

Second, there are (according to the FTC) now two types of biodiesel, the first is the one most people are familiar with, where a plant, seed or animal derived oil is through transestrification converted to a Methyl Ester that is defined by ASTM D6751 and commonly referred to as biodiesel. The other is known as “Biomass-based Diesel”, this a fuel derived from biomass that does not contain Methyl Esters (note: there currently is not an ASTM specification for this product).

Third, effective December 16th, 2008, all retail fuel pumps are subject to the following labeling requirements based on Section 205 of the Energy Independence and Security Act of 2007 (EISA): Fuel blends containing no more than five percent (5%) biodiesel or no more than five percent (5%) biomass-based diesel and that meet ASTM D975 require no label.

Fuel blends containing more than five percent (5%), but no more than twenty percent (20%) biodiesel require a dispenser label 3”w x 2.5”h with a Blue background and a Bxx reporting the exact percentage or “Between B5 and B20” statement.

Fuel blends containing more than twenty percent (20%) biodiesel require a dispenser label with a Blue background and a Bxx reporting the exact percentage or “Containing more than 20% biodiesel statement.

Biodiesel that is “neat” or B100 must be labeled as “B100 Biodiesel” and “Contains 100 percent Biodiesel” on a Blue background.

Fuel blends containing more than five percent (5%), but no more than twenty percent (20%) biomass-based diesel require a dispenser label 3”w x 2.5”h with an Orange background and text reporting the exact percentage or “Between 5% and 20% Biomass-based Diesel” text statement.
Fuel blends containing more than twenty percent (20%) biodiesel require a dispenser label with an Orange background and text reporting the exact percentage or “Containing more than 20% Biomass-based Diesel” statement.Biomass-based Diesel that is “neat” or 100% must be labeled as “100% Biomass-based Diesel” on an Orange background.

Note: You should visit the FTC website at: http://www.ftc.gov/ at look at: 16 CFR Part 306 - RIN #3084-AA45 for more complete information on these requirements.

What this means in the real world is that suppliers can now add up to 5% biodiesel in retail fuels without notification to customers.

If you want biodiesel and have done your homework on what is required to successfully and safely use this fuel you should note what you want as you order your fuel.

If you do not want any biodiesel you should issue a written purchase order to your supplier telling them exactly what you want, e.g. no biodiesel.

Note: under the new ASTM D975 spec, 5% is allowed.

Diesel Fuel Mileage Decrease in Winter

Why Diesel Fuel Economy Drops in the Winter

Diesel fuel, particularly in the northern tier states changes rather significantly from season to season. In the cold weather months generally starting in September or October refiners begin to alter the chemical composition of diesel fuels to improve cold weather operability characteristics to meet ASTM, Pipeline Operator, and Customer requirements and specifications.

Refiners talk about the components that come out of the refining process as “streams”. In a typical refinery today there can be over 180 “streams” coming from the refining of crude oil. The addition of lighter product streams are known by names such as “aromatic chemicals”, “naptha’s”,” kerosene’s” and others to #2 diesel (whether Ultra-Low Sulfur Diesel (S-15) or Low Sulfur Diesel (S-500)) will lower (improve) the Cloud Point (CP), Cold Filter Plug Point (CFPP) commonly referred to as the gel point, and Pour Point (PP) depending on how much of those components are added to the base fuel. Refiners have a lot of latitude in determining how much of and what components are used to make these improvements.

The issue from a fleet operators standpoint is that these changes lower energy (Btu) content of the fuel. It is normal for fuel economy to decrease from one to as much as five percent seasonally. This decrease can be further exacerbated by fuel racks and or distributors further cutting with kerosene to try and improve cold weather operability. The normal energy content of #2 ULSD ranges between 138,000 and 140,000 Btu’s, kerosene is much lower ranging between 130,000 and 135,000 Btu’s, whereas gasoline is about 124,000 Btu’s per gallon.

As you can see the more lighter components added to fuel, the lower the energy content. Note: ULSD has 1%-3% lower Btu content than the LSD. This is primarily due to reduction in wax content in ULSD.

So if you put all of this together in a time line, you can see that you begin using additive to improve cold weather performance at the same time the refiners are blending the fuel in a way that reduces Btu content which lowers your fuel economy, then in the spring you stop using additive at the same time the refiners are going to a “summer” blend which increases the Btu content and so your mileage goes up.

Other cold weather considerations are more idle time, slower transit speeds, more time in traffic, and even driving through snow all, of which can have a significant negative impact on fuel usage.