Safe Aircraft Fuel Wing Deicing Fluids Proposed to Replace Toxic Glycols

3/28/1996 - 31-96r
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Winter may be fading to spring in the northern hemisphere but the search for nontoxic, inexpensive, and biodegradable deicing compounds for both jet fuels and wing deicing continues unabated at the Naval Research Laboratory (NRL) and George Mason University, Fairfax, Va.

In a scientific paper to be published in the journal, "Fuel Science and Technology," and highlighted at the 211th American Chemical Society (ACS) national meeting in New Orleans, La., March 24-28, scientists from NRL's Navy Technology Center for Safety and Survivability, Fuels Section, and George Mason's Chemistry Department, show that acetals and ketals of reduced sugars represent safe, viable alternatives to glycol-based additives.

These alternatives are nontoxic to people and the environment. They are inexpensive, fuel compatible and biodegradable, and, of utmost importance to aviators and their passengers, they prevent fuel from icing just as effectively as do the glycol-based products.

The current fuel system icing inhibitor additives used in both military aircraft and commercial airlines are toxic at the concentrations that are required for effective deicing, according to NRL's Dr. George Mushrush, principal investigator and also a professor at George Mason University. Their use is mandatory in all military aircraft fuels and optional for worldwide aviation fuels depending on routes, flight lengths, and the season.

"The additives currently used are ethylene glycol monomethyl ether (EGME) and diethylene glycol monomethyl ether (DiEGME). When fuel system sumps, filters and storage tanks are drained, they contain EGME and DiEGME and therefore create a personnel hazard," Dr. Mushrush said.

"When glycols and their derivatives are introduced into the environment, they cause the death of aquatic organisms as dissolved oxygen is depleted by the high oxygen demand made by glycols as they decompose. The U.S. EPA is currently developing regulations specifically addressing the problems associated with deicer runoff," Dr. Mushrush explained.

NASA, the FAA, and industry officials have proposed the use of propylene glycol-based deicing compounds. However, these materials have been shown to be unsuitable due to higher costs per unit effectiveness. These compounds are also toxic, though less toxic than either EGME or DiEGME, according to the U.S. Department of Health and Human Services.

According to Dr. Mushrush, "NRL's approach is to utilize the large U.S. surplus of sugars (which are carbohydrates) as the basis for the synthesis of biodegradable deicing compounds. Studies demonstrate that acetals and ketals synthesized from the reduced mannose sugar are effective icing inhibitors for aircraft fuel systems.

"At present, the manufacture of carbohydrates are important to many industries and to the organic chemical synthesis industry. With such a broad demand, the basic building blocks of carbohydrate chemistry are industrially quite inexpensive and readily available.

"The carbohydrate derivatives show excellent fuel stability and, based on accelerated storages tests, should remain stable in Jet A or JP-8 fuels for at least two years. They do not cause preoxidation, and they mimic the behavior of EGME and DiEGME in JP-8 rig simulator tests."

The authors note that their article complements the already abundant literature with a new use for these rather simple compounds.

The paper was authored by Dr. Mushrush; Mrs. Erna J. Beal, NRL; Mr. Wayne M. Stalick, Dr. Subash C. Basu, and Mr. J. Eric Slone, all of George Mason University; and Mr. John Cummings, Naval Air Warfare Center, Trenton, NJ.

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