Hello all,
Below is the revised version of “The ABC of Ethanol”. The revision and changes were suggested by many individuals from leaklist, Veeder-Root, KWA, and others. The opinion expressed by these individuals is theirs and not the institution that they represent. I would like to thank them for their valuable contributions.
The ABC of Ethanol
Ethanol fuel, also called Oxygenated fuel, is a simple “grain alcohol” or drinking alcohol. There are several ways to chemically represent its molecular formula, one representation is C2H5OH which indicates it is a hydroxide, notice the “OH”. Its formula may also be represented as CH3-CH2-OH, and its intoxicating effects had been known for centuries. Ethanol consumption as fuel for light automobiles is rather recent.
Ethanol will readily dissolve water, and is considered infinitely soluble in water. Since ethanol and water readily dissolve in each other, when ethanol is used as an additive in gasoline, water will actually dissolve in the blended fuel to a much greater extent than in conventional gasoline. When the water reaches the maximum amount that the gasoline blend can dissolve, any additional water will cause the water and ethanol mixture to separate from the gasoline. The amount of water (in percent of the total volume) that may be dissolved in ethanol varies with temperature. For example, at 60 degrees F, water can be absorbed by a blend of 90% gasoline and 10% ethanol, commonly called E10, up to a content of 0.5 volume percent before it will phase separate. This means that approximately 3.8 teaspoons of water can be dissolved per gallon of the E10 before the water and ethanol mixture will begin to phase separate.
If the above example can be repeated several times and approximately the same results are obtained, then by volume we can have ½ of one percent of water by volume in the mixture and not causing any damages to the vehicles. Any extra water dissolved in the ethanol will cause the water and ethanol mixture to move to the bottom of the UST and may be checked periodically with a simple gadget.
Since water is a natural product of combustion, any water in solution is removed with the product water in the exhaust system. The only effect water in solution with gasoline can have on an engine is decreased fuel economy. For example, assuming a high water concentration of 0.5 volume percent, one would see a 0.5 percent decrease in fuel economy. This fuel economy decrease is too low for an engine operator to notice, since many other factors (such as ambient temperature changes, wind and road conditions, etc.) affect fuel economy to a much larger extent.
There are those that claim under certain conditions and at certain time during combustion of the engine if water is added to the gasoline it actually improves the fuel efficiency.
Different studies suggest that while separate water phases in a fuel can be damaging to an engine, small amounts of water in solution with gasoline should have no adverse effects on engine components.
Based on the fact that every gallon of E10 can dissolve 0.5 percent of water at 60 degree F without phase separating, we can assume that the possibility of water build up at the bottom of the large tanks that have medium to large throughput decreases drastically. For example, if a throughput of a tank is 1000 gallons per day, the tank can absorb 5 gallons of water before phase separation of the water and ethanol mixture begins to occur. Indeed ethanol may help get rid of excess water at the bottom of the USTs.
Whenever two liquids are mixed, the best we could hope for is to get the mathematical sum of those liquids. For example, when one gallon of water is mixed with another gallon of water both having the same temperature the result is two gallons of water. But when one bushel of cantaloupes is mixed with a bushel of sesame seeds, the result is approximately 1 ¾ of bushels (depending on the sizes on the cantaloupes). When a gallon of water is mixed with a gallon of ethanol the volume of the mixture is about 1.91 gallons. Hopefully this volume change (reduction of about 5% in volume) is small enough not to matter.
Now that we are on the verge of modifying and rewriting the protocols for USTs, there is the 3,000 year old question which is, should we use “volume” or “mass”. Choosing volume over mass we need to include temperature, compensate for the change of volume, and also when we add 1+1 we don’t get 2.
Keywords
Phase Separation: When water is dissolved in a gasoline and ethanol blend, such as Exx, and reaches the saturation point, any additional water added to the gasoline blend will cause the water and ethanol mixture to separate from gasoline and move to the bottom of the tank. This process is called “Phase Separation”. Now there are two distinct states in the tank, one gasoline, the other a water and ethanol mixture at the bottom of the tank.
Exx: If “xx” is replaced by 10, it implies that the mixture contains 10% ethanol and 90% gasoline, and so on.
Grain alcohol: Is used as a general word covering any agricultural product that may be used to produce alcohol, such as raisins, dates, corn, etc.
Miscibility: The tendency or capacity of two or more liquids to form a uniform blend, that is, to dissolve in each other, ethanol and water have this property.
Below are comments and answer to some of them.
Sam,
I trust you are open for comment.
Please accept that the early Model T Fords ran on ethanol, so its use is not that recent.
Why grain? Are you overlooking Brazil where it has been made from sugar cane for decades and is the most energy efficient method of production?
You might find that the use of grain as a feed-stock is practically energy neutral with as much being consumed in the distillation process as is available from the end product. If it were not for the “tax break” (subsidy) then it would still be fed to humans and animals rather than “wastefully” converted.
Yes fuel consumption is better on rainy days when the combustion air has a higher humidity %.
Yes, sloshing of fuel in the tank as the vehicle moves will mix up any water; hence the problem with E10 in boats where the boat has been moored.
Best regards,
That is very informative and will be something to pass along to customers.
Are gasoline and ethanol miscible? What would happen to an E10 blend if it were mixed with diesel fuel? Would all three components blend together or would the E10 be separate from the diesel. I am asking in the frame of reference of E10 contaminated diesel fuel (~6K gallons of fuel ½ is E10 the other ½ is diesel) and mixing that load back into a million gallon tank of diesel.
Thank you,
Sam,
A correction: Phase separation involves primarily the separation of ethanol from the fuel blend, with a little bit of water mixed with the separated ethanol. Phase separation reduces the ethanol content in the gasoline blend.
So…at 60 degrees F, approx 4 teaspoons per gal dissolved in E10; 768 teaspoons per gallon; RCRA I requires UST leak detection to catch a 0.2 gallon/hour leak; 0.2 gallon equals 154 teaspoons; 154 teaspoons divided by 4 teaspoons per gallon is approx 40 gallons….if I do the math correctly, more than 40 gallons of E10 will dissolve a 0.2 gallon per hour water infiltration leak (most likely) and prevent UST leak detection equipment from working, at least until the E10 is “saturated” w/water and the remaining water leaking in phase separates. And the higher the thruput, the more likely the E10 will keep dissolving the leaking water and prevent the leak detection from working when ground water is higher than the fuel level in the UST.
Now I understand the concerns w/ethanol blends and leak detection.
Reply to above question (if I do the math …) by one of our guest
This statement Is not entirely incorrect, but I want to point out that when water dissolves in E10 it does not just disappear. The volume increases when the water dissolves and this increase can be detected by the leak detection system. The calculations to provide a leak rate are slightly different as when ethanol dissolves in water the sum of the two volumes is more than the actual increase. If we are clever enough we can figure out how to detect the water ingress.
Reply to above question (if I do the math …) by another of our guest, this one also explains how the water ingress is “masked” by loss of volume.
I believe what the commenter is saying is that enough water will dissolve into the ethanol without increasing the volume to hide a 0.2 gallon per hour leak. I didn’t try to check the math. I am sure you can do that better than I. But, the way I understand it, when water first comes in contact with ethanol, the ethanol will absorb a certain percentage of water where the volume of the ethanol water mixture is the same as the volume of the ethanol alone without the water. This could also be illustrated with the cantaloupes and sesame seeds. When you first start adding the sesame seeds, all the voids between the cantaloupes start filling, which would not increase the volume of the cantaloupe and sesame mixture at all. When all the voids are filled with sesame seeds, then the volume of the mixture begins to increase.
When there is no volume increase in the ethanol and water mixture, there would be no indication of a leak by a volume based leak detection method. That, to me, presents a problem. Especially in a scenario where the throughput rate continues to absorb the water into the volume of the ethanol with no volume change over and over again with every delivery so that the water ingress is not discovered until the ingress rate increases, or the throughput rate decreases. This problem would “matter” if the throughput allowed the water to be continuously removed with the ethanol prior to increasing the volume, thus masking the water ingress. I believe this is a real concern, but without doing the math, I do not know if it would actually mask a 0.2 gallon per hour leak that the commenter above said it would.