ManejarBiodiesel

3.6 Exigencias del Receptor o Terminal

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The first consideration after you have made or received a batch of biodiesel is ensuring proper storage for the fuel.

 

3.6.1 Storage Tank Considerations

 

Storage tanks in the distribution chain present a challenging maintenance process for fuel handlers. Composition of storage tanks, pipes and pumping

equipment are critical in maintaining the integrity of the biodiesel. construction materials such as carbon steel, stainless steel, or aluminum are recommended.

 

Deficiencies in fuel storage are not relegated to biodiesel alone. For decades petroleum handlers have faced numerous quality challenges resulting from the poor storage and handling of fuels. Stored fuel may form insoluble materials that plug filters, foul injectors and form combustion system deposits which all promote fuel-system corrosion. A lack of good housekeeping practices will only increase operational headaches and result in more time and money in the long run.

 

Improper placement of water draw-off taps can lead to accumulation of water in the system. Lack of attention to water evaluation may exacerbate any existing problems. Electronically or physically testing the tanks (sticking) with water- finding paste before and after each fuel delivery is imperative. Drawing down water levels in tanks will go a long way in preserving the quality of your stored fuels.

 

Biodiesel compatible gaskets and elastomeric materials are highly recommended. B100 may degrade some hoses, gaskets, seals’ elastomers, glues and plastics with prolonged exposure. Natural or nitrile rubber compounds, polypropylene, polyvinyl, and Tygon materials are particularly vulnerable. More testing is being done to extend this list of vulnerable materials. Most elastomers (Viton/Teflon) used after 1993 are compatible with B100. Before handling or using B100 contact the equipment vendor to determine compatibility with fatty acid methyl esters.

 

B100 permeates some plastics typically used in petroleum applications. Materials such as polyethylene and polypropylene should not be used for storing B100.

 

Biodiesel blends of 20% or less have shown a much smaller effect on these materials. The effects are virtually non-existent in low-level blends such as B2. When handling blends of B20 or less, normal ****monitoring of hoses and gaskets for leaks is sufficient.

 

Teflon, viton, and nylon have very little reaction to biodiesel and are among the materials that can be used to update incompatible equipment. B100 suppliers and equipment vendors should be consulted to ensure the most recent findings on compatibility. For bulk fuel handlers of biodiesel it is highly recommended that you speak with your hose suppliers to source hoses that are compatible with neat biodiesel.

 

Most tanks designed to store diesel fuel will be adequate for storing B100. Acceptable storage tank materials include aluminum, steel, fluorinated polyethylene, fluorinated polypropylene, teflon, and most fiberglass materials.

 

Brass, bronze, copper, lead, tin, and zinc may catalyze the oxidation process of biodiesel creating fuel sediments or gels and salts. Lead solders and zinc linings should be avoided, as should copper pipes, brass regulators, and copper fittings. Affected equipment should be replaced with stainless steel, carbon steel, or aluminum. Blends of B20 and lower reduce the impact of metal compatibility issues.

 

Material Effects of Biodiesel

Teflon	Little change
Nylon 6/6	Little change
Nitrile	Hardness reduced 20%, Swell increased 18%
Viton A401-C	Little change
Viton GFLT	Little change
Fluorosilicon	Little change in hardness, Swell increased 7%
Polyurethane	Little change in hardness, Swell increased 6%
Polypropylene	Hardness reduced 10%, Swell increased 8-15%

 

Low temperature/cold weather properties need to be taken into consideration when discussing storage tanks. For terminal companies that are storing biodiesel in its neat form, you will need to heat your tanks, piping and associated delivery equipment to accommodate the pour point of biodiesel since it varies by feedstock. Section 3.6.6 Low Temperature Handling Properties, discusses the issue of the range for cloud point for biodiesel fuels even from the same feedstocks. Keeping the biodiesel heated from 10°C-16°C is highly recommended until you can ensure that you have satisfactorily blended it into your distillate product of choice.

 

Key Points for Storing Biodiesel

 

• Acceptable storage tank materials include aluminum, steel, teflon,fluorinated polyethylene, fluorinated polypropylene, and most fiberglass materials.
• Do not store B100 for long periods of time in systems containing reactive metals.
• B100 should be stored at temperatures at least 6°C higher than the cloud point. Generally, storage temperatures of 10°C to 13°C are acceptable for most B100, although some B100 fuels may require higher storage temperatures. Therefore, most underground storage facilities are adequate, but above ground fuel systems, depending on the climate, should be protected with insulation, agitation, heating systems or other methods.
• B100 is a mild solvent so carefully clean the tanks and fuel system where any sediments or deposits may exist. Prepare for more frequent filter changes while the system is being cleaned.

 

3.6.2 Solvency/Cleaning Effect

 

Biodiesel is comprised of methyl esters. Methyl esters are mild solvents and have been used as low volatile organic-compound cleaners for years. Therefore, B100 may dissolve or dislodge the accumulated sediments in diesel storage tanks, pipes, fueling systems and engine fuel tanks. Dissolved or dislodged sediments can plug fuel filters and cause fuel injector failure. Existing tanks and transfer systems should be cleaned, dried, and inspected prior to introducing B100 into the tank.

 

Biodiesel and biodiesel blends will form high sediment levels when in contact with the following metals:

• Brass, Bronze, Copper, Lead, Tin, Zinc

 

If you plan to use or store biodiesel the following considerations should be made:

 

• Carefully clean the tanks and fuel system where any sediments or deposits may exist. Petroleum handlers should be evaluating bulk storage tanks regardless of possible biodiesel storage and distribution to ensure that the fuel quality preservation of conventional distillates is maintained.
• Be prepared for the possibility of some filter clogging and more frequent filter changes until the system has been cleaned of old sediments. Once the system is cleaned the filter change interval should return to normal intervals.
• Wipe biodiesel spills from painted surfaces immediately as it will dissolve some paints.

 

Note: These effects are greatly reduced or eliminated in blends of 20% or less. (B20, B5, B2 etc.) Additional unscheduled filter changes have been reported in less than 2% of the cases when biodiesel blends less than 20% are first introduced. There have been no reports of additional filter changes with the use of B2. Tank maintenance and storage is crucial in all cases. However, this issue is vital for those organizations planning on using diesel fuel or heating oil tanks with years of accumulated sediment (tank bottoms). It is highly recommended that the tanks be cleaned before introducing B100 biodiesel.

 

 

In some cases, the cleaning effect or solvency of B100 has been confused with gums and sediments that could form over time in storage as fuel ages. It should also be noted that this solvent effect should diminish after the second load. Tests of the acid number and the viscosity should be performed to determine the cause of the sediment. If these numbers are within ASTM specifications, the sediment is most likely the result of the solvency of B100.

 

3.6.3 Excess Air

 

As a fuel tank is emptied, air will enter through the vent pipes to displace the fuel in the tank. The excess air in the tank may lead to increased oxidation, particulate contamination, and increased water levels. These contaminants affect both the stability and quality of the fuel. In order to limit the effects of air in the tanks, it is recommended that fuel handlers do not store fuels for long periods of time in partially empty tanks without stabilizers. Additionally, one may consider desiccant filters on vents to reduce moisture and particulate contamination (dirt).

 

3.6.4 Water Contamination

 

Biodiesel is susceptible to water-related problems. Desiccant filters on breathing vents will greatly reduce condensation in the tank and are highly recommended. Sump drains are recommended where practical.

 

Both free and entrained water accelerate corrosion and fuel degradation. Free water may enter bulk fuel tanks via condensation, carry-over from the fuel distribution system or leakage through the fill cap, spill containment valve or piping.

 

In addition to accelerated breakdown of the fuel product, water also creates a fertile growing environment for microbial contamination. Microbial activity,surfactants, alcohols, particulates, and poorly designed additives may be the cause of entrained water problems.

 

Poor tank design can make complete removal of water nearly impossible, and therefore, it is important to take steps to prevent water entrance. If you believe that your storage systems fall into this category contact a mechanical engineering company to determine a strategy that will optimize your storage tank.

 

3.6.5 Microbial Contamination

 

See Section 2.4 - Biocides for information on how to deal with microbial contamination of your biodiesel.

 

3.6.6 Low Temperature/Cold Weather Handling Properties

 

Biodiesel cold weather properties require that careful attention be paid when dealing with the product in cold weather climates. It is extremely important that before handling the fuels, one be familiar with the cold weather properties of both biodiesel and the generic diesel intended for blending.

 

Blends of biodiesel will impact cold weather operability in direct relationship to the independent base analysis of the fuels being blended to create B2, B5, and B20. Therefore, the cloud point and the pour point of both generic fuels require the attention of the blender, and the blended cloud point information should be provided to the customer. It is imperative that selection of the absolutely lowest operating temperature of your diesel fuel be adhered to prior to accepting blends of biodiesel.

 

The same precautions taken with petroleum diesel can be used to insure trouble-free operations with biodiesel. Traditional cold weather solutions for diesel work well with biodiesel with the exception of commercial cold-flow additives. Although some additive suppliers claim to have products that work with biodiesel, it is more likely that these products impact the generic diesel or heating oil cold-flow characteristics and not the neat biodiesel.

 

B100 solidifies/freezes at higher temperatures than conventional diesel fuels. Operators must take this into account if they are handling or using B100. Most B100 begins to cloud between 3°C and 15°C. This clouding will lead to sedimentation that could plug lines and filters. Heated, insulated tanks, lines, and pumps may be needed even in moderate climates. The viscosity of B100 begins to rise dramatically as it begins to gel. Viscosity rises to levels much higher than most diesel fuel. This can cause increased stress on pumping equipment.

 

Cloud point is the temperature, during cooling, at which wax crystals first form in the fuel. Wax crystals create a visible haze. These crystals can plug fuel filters in diesel engines. Without heating aids on the fuel filter and fuel lines, the cloud point limits the low temperature operability of a diesel fuel.

 

In general, it has been found that cloud point or LTFT (Low Temperature Flow Test) are better indicators of operability limits. The LTFT is a test which takes 24 hours, and is therefore impractical. In many cases, the CFPP (Cold Filter Plugging Point) tends to overestimate the operability of B100 and B20 blends. The cloud point is therefore the most widely accepted measure of cold weather operability limits. On average, a B2 blend will warm the cloud point by 2°C to 3°C. In general, a B20 blend will impact the finished fuel’s cold weather operational temperatures by 7°C to 12°C. The actual warming of the cloud point is dependent upon the cloud point of the biodiesel fuel and that of the petroleum diesel fuel. Keep that compromise in mind when sourcing your base diesel fuel.

 

B20 has enjoyed a successful track record when these basic instructions are adhered to.

 

Pour Point is the lowest temperature at which a diesel fuel will flow, and is usually a few degrees below the cloud point. This can be relevant to the minimum delivery temperature for a diesel fuel, especially a biodiesel fuel blend.

 

Low Temperature Operability Properties

 

B100 Feedstock	Cloud Point °C	Pour Point °C	Cold Filter Plug Point °C
Soy Oil	2	-1	-2
Canola Oil	-3	-4	-4
Lard	14	11	11
Edible Tallow	20	13	14
Yellow Grease	42	12	11

 

 

More typical cloud point ranges are found in the following table. Typical cloud points for biodiesel will vary based on the feedstock from which they were derived:

 

 

B100 Biodiesel Feedstock	Fuel Cloud Point (°C)
Soy Oil	3 to -7
Canola Oil	-2 to -12
Tallow	10 to 20
Yellow Grease	5 to 15
Coconut Oil	6 to 7
Palm Oil	12 to 13
Jatropha	6 to 7

 

Source: Robert Dunn, "Cold Weather Properties and Performance of Biodiesel," in The Biodiesel Handbook, 2005.

 

B100 should be stored at temperatures at least 6°C higher than the cloud point. Generally, storage temperatures of 10°C to 13°C are acceptable for most B100 fuels, although some B100 fuels may require higher storage temperatures.

 

These temperature requirements make most underground storage facilities adequate, but above ground fuel systems, depending on the climate, should be protected with insulation, agitation, heating systems or other methods. These precautions should also be taken with piping, tanks, pumping equipment, vehicles or any other equipment used for the transport or storage of the fuel.

 

Cold-flow additives have had limited effectiveness on biodiesel produced in the United States. The same would be true of all North American produced biodiesel fuels. The effectiveness of the additives varies greatly depending on the type of biodiesel and the processing that it has undergone. Cold-flow additives have been used much more successfully with biodiesel blends. For further information contact the major additive manufacturers.

 

Maintaining Fuel Quality

• Specify fuels meeting ASTM D6751 for B100 biodiesel blend stock

 

• Reference cold weather performance and other special needs prior to ordering

 

• Be proactive with general housekeeping practices

 

• Execute a monthly or quarterly fuel-analysis program to ensure the safe keeping of fuels