Proper Handling Of Ethanol

As more ethanol is introduced to the supply chain, handlers need to be aware of potential conditions like “phase separation.”

By Mike Gruca

Because of ethanol's affinity for water, gasoline oxygenated with ethanol is generally not transported in pipelines like traditional motor fuel. Instead, it is added to gasoline tanker trucks at the terminal level in order to keep its possible exposure to water at a minimum.

However, water still has the ability to infiltrate each link in the supply chain, opening the door for potential problems with the shipping of ethanol-oxygenated gasoline or the higher-concentration E85 that is entering the supply network on a more regular basis. According to various reports, ethanol can be found in up to 46% of the nation's gasoline supply as a 10% oxygenate, while the number of fueling stations offering E85 for use in flex-fuel vehicles stood at almost 1,300 sites in the Unites States as of August 1.

Phase Separation
One of the main concerns in the supply process as the use of ethanol continues to climb is the potential for what is called “phase separation” in gasoline that contains ethanol. Phase separation occurs when enough water contaminates the gasoline, causing the ethanol to attach itself to the water molecules, leaving two distinct layers in the storage tank: a gasoline-only layer at the top and an ethanol/water “cocktail” along the bottom.

As noted on Chevron's Web site, while conventional gasoline can dissolve up to 150 parts per million of water at 70°F, the situation is different for gasoline oxygenated with 10% ethanol. This 90% gasoline/10% ethanol blend can dissolve up to 7,000 ppm of water at 70°F. When this blend is cooled, both the water and some of the ethanol become insoluble. Contacting the blend with more water also draws ethanol from the blend. The result, in both cases, is two layers of liquid—an upper ethanol-deficit gasoline layer and a lower ethanol-rich water layer. This phase separation of the gasoline/ethanol mix lowers the octane number and may cause knocking in an engine, while the engine will not run at all on the ethanol/water layer.

As far as E85 is concerned, according to the New England Interstate Water Pollution Control Commission's L.U.S.T. Line of May 2006, phase separation may also occur in this fuel, but not as often, since approximately 4% water is needed. This is a large amount of water for a fueling system and would only result under extreme conditions.

Because of this potential for phase separation at any ethanol level, it is imperative that motor fuels containing ethanol not be exposed to water during its distribution or use, making housekeeping at the service station and any other points along the supply chain very important in the prevention of water contamination. Another property of ethanol blends is that they are hygroscopic, meaning they absorb moisture from the air, raising the potential for phase separation during storage if the tank is vented to the atmosphere and is subject to condensation formation as a result of temperature change.

This ability of water to insidiously enter the fuel stream makes it vital that those handling fuels that contain ethanol at any level are extremely vigilant when adding it to or reconciling it with their fuel supply. For example, a marketer buying fuel has to be aware of the potential phase separation properties of adding certain levels of ethanol- or non-ethanol-blended fuels to his supply. If this marketer has a tank containing 3,000 gallons of a 90-10 blend of gasoline and ethanol and adds 3,000 of neat gasoline to that tank (which, theoretically, could contain 30 gallons of water), the resulting mixture would contain 95% gasoline and 5% ethanol. However, if phase separation of gasoline occurs with 1% water in a 90-10 mixture, studies have shown that phase separation would not necessarily occur with a directly proportional amount of water in a 95-5 gasoline/ethanol mixture.

Also factoring into the equation is the temperature of the product. According to the Renewable Fuel Association's “Fuel Ethanol Industry Guidelines, Specifications and Procedures,” the amount of water tolerated by a gasoline/ethanol blend is directly dependent upon product temperature. The lower the temperature, the lower the water tolerance, meaning that at 60°F a 10% ethanol blend will tolerate approximately 0.5% water. However, at 10°F that tolerance can be reduced to approximately 0.3%. Because of these properties, an E10 fuel system that is near its saturation point at 60°F may experience phase separation if there is a sudden reduction in temperature.

Sensing Filtration
When dispensing fuels containing ethanol, proper filtration can detect phase separation. Special phase separation dispenser filters will notify the operator of the condition by slowing fuel flow to less than one gallon per minute. This “slow flow” condition is a signal that water is present and that the tanks should be tested for phase separation.

In order to ensure that their water-detecting properties are used to their maximum capabilities, these phase-separation-sensing filters should generally be changed after six months in service, after dispensing 500,000 gallons of fuel, at any point when a reduction in flow rate is detected or at any time the fuel-load composition is changed.

Handlers of fuels containing ethanol also have to remember that high concentrations of ethanol will scour tanks, hoses and other fueling components, resulting in a lot of contaminants being thrown at the filter. Because of this, filters should be changed more often when tanks are being converted from gasoline-only use to being used with fuels containing any level of ethanol. Before this conversion, it is also wise to dry out wholesale storage tanks and properly prepare retail storage tanks and dispensers for the new fuel.

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The PEI Journal • Third Quarter 2007 • Volume 1, No. 3 • Contents are Copyright © Data Key Communications, Inc.
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