MFA Oil
By Don North
Considerations for tank storage of ethanol
Ethanol-blended gasoline has been around since the 1970s, when fuel supplies were short due to oil embargoes. Support of the product has re-emerged since 9/11 and the war in Iraq due to a resurging quest for domestically sourced fuel and the fear of supply shortages from the Middle East.
Several cities and states have mandated use of ethanol-blended gasoline, and in 2004 about one-third of gasoline used in America was combined with ethanol, most of it E10, a blend of 10 percent ethanol and 90 percent unleaded gasoline. Another blend, E85, is gaining in popularity as it becomes more readily available and as manufacturers increase production of flexible fuel vehicles, which are the only vehicles that can run on the product.
The state mandate that all automotive unleaded gasoline sold in Missouri contain 10 percent ethanol by 2008 means many fuel storage tanks will hold ethanol for the first time. It is important to note that, although any gasoline engine (including lawn mowers, chain saws, boats and autos) can run on E10 with no modification, when ethanol goes into a storage tank for the first time, preventive maintenance requires some housekeeping measures.
The worst enemy of ethanol-blended gasoline is water. Although water is a problem for any fuel, ethanol blends present additional complications. Water in straight gasoline simply sinks to the bottom of the tank and may stay there a long time. But when an ethanol-blended gasoline is introduced for the first time, if there is water on the bottom, the ethanol will draw it into the fuel. When the ethanol exceeds its tolerance level, the ethanol-water mix will separate from the gasoline, resulting in “phase separation.”
Phase separation is what happens when too much water gets into a tank that contains a blend of gasoline and ethanol. Ethanol disperses itself in gasoline, and while the ethanol molecules roam around the mixture, they pick up a water molecule or two. When there is too much water in the tank, the ethanol can’t hold it in suspension, so the ethanol and water settle to the bottom of the tank, resulting in two layers: gasoline on top and the ethanol-water mix on the bottom.
The ethanol-water mix will not run a gasoline engine. The amount of water it takes to cause phase separation is fairly significant – or fairly small – depending on how much fuel is in a tank in the first place. As a rule of thumb, it takes about a quarter to a half of a percent of water content to separate a 10 percent ethanol blend. That means it would take a quart to a half-gallon of water to affect 100 gallons of ethanol-blended gasoline.
There is a very simple solution to the problem of phase separation: prevention. Don’t let water in. Be sure that fill lids and tank covers are in good condition, fit properly and are placed on the fill openings correctly. These steps will prevent nearly every possibility of problems. And before that first fill of an ethanol-blended gasoline, make sure all water and sediment have been removed from the storage tank.
Most above-ground fuel storage tanks have an inlet/outlet at the bottom of the tank that allows small amounts of water and sediment to be drained. Underground tanks have to be cleaned with a suction pump to remove all water and sediment.
If phase separation occurs, correcting the problem can be as simple as removing the water mix. The difficult part is knowing the level (gallons) of the phase separation. A lab test is required to find where the ethanol-water mix stops and the good gasoline starts. Larger quantities require more complex solutions, and your fuel supplier should be happy to work with you to solve that type of problem.
Don North is director of product development and lubricant sales at MFA Oil.
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