Antioxidant & Antistatic 2

[NiravK]

I want to know the chemical composition of Antioxidant / Antistatic addtivites used for 'jet fuels'.

Who are the suppliers? What should an inquiry consist of, if i want to order these chemicals?

What should be the criteria for the selection of these additives from available options?

Thanks.

 

[25362]

This will be a bit long submission based on ASTM manuals.

While the additives purpose is generally to improve certain aspects of the fuel performance, more often than not they achieve the desired effect by preventing or supressing some undesirable fuel behaviour, such as corrosion, icing, oxidation, detonation, etc.

Their effectiveness is due to their chemical nature and the resulting interactions (usually) with trace constituents of the fuel.

When approving additives one has not only to establish that they achieve the desired results and are fully compatible with all materials likely to be contacted, but to ensure also that they do not react in other ways producing adverse side effects on the fuel's performance, possibly by interfering with the action of other additives present.

The basic testing of aviation additives for approval purposes is usually carried by the aircraft and engine manufacturers; their results and conclusions may then appear in company fuel specifications, but they are also reviewed for adoption by the international fuel specification authorities. E.g., in the case of civil aviation: ASTM and IATA; for military fuels: US-MIL and DERD.

There is the ASTM D 4054 which, in conjunction with Research reports D02-11125, and D2-1137, is meant to suit ASTM D 1655 (Standard Specifications for A.T. Fuels).

Some additives in current use:

Color dyes (ASTM D 2392). Not permitted in jet fuels.

Antioxidants (Gum Inhibitors). Generally permitted but not mandatory in straight-run jet fuels. However, "hydrotreated" fuels, because of the removal of natural trace sulfur compounds acting as inhibitors, can generate a high-peroxide content which can cause deterioration of fuel system components made of nitrile rubber. A maximum limit of 24 mg/L usually applies to all jet fuels, with a minimum of 17.2 mg/L when the additive is made mandatory. The additives are generally phenolic or nitrogen-containing materials.

Metal deactivators. Meant mainly to "restore" the thermal stability of a fuel degraded by copper pick-up during distribution from refinery to airport. Metals such as Cu may degrade fuels storage stability (gum forming tendency) or the thermal stability of the fuel by catalytic action.
The purpose of the additive is to passivate these metals while in solution in jet fuels. One approved metal deactivator: N-N'-disalicylidene 1,2 propane diamine.

Corrosion inhibitors (CI). They are needed because traces of water are sometimes present. One direct benefit: the reduction of the amount of scale and fine rust shed into the fuel as particulate contaminants. They also provide "lubricity" to jet fuels. ASTM D 5001 has been developed to test mild wear, however is insensitive to fuel composition. Civil jet fuels, wide-cut kerosine type, normally do not contain CI. However, as a general rule, U.S. and British military jet fuels require the addition of an approved CI. U.S. MIL-I-25017 and the British DERD 2461 contain approved lists of CI, and the min/max concentrations allowed. Since some CI exhibit adverse effects on water-separating properties, electrical conductivity, and thermal stability, there is a reluctance to permit the use of additives that have not been thoroughly proved in service.

Fuel system anti-icing inhibitor (FSII). If the aircraft don't have heated main fuel filters to prevent blockage by ice formed from water precipitated in flight, as f.e., some Russian airliners, FSII prevents these problems by lowering the freezing point to such a degree that no ice formation can occur. They use additives based on ethyl or methyl cellosolve. The additive has only a limited solubility in the fuel and a much greater affinity for water. Ethylene glycol monomethyl ether(EGME) -flash point 40 deg C- has been superceded by di-EGME with a flash point of 65 deg C. Upon using EGME it was found that it is a very effective biostat if used continuously. FSII can be lost in use by evaporation or by contact with water during transportation. Among the various test methods to determine FSII content: IP 277 and ASTM D 5006.

Antistatic additives or static dissipator additives (SDA). They promote static relaxation and increase the electrical conductivity of the fuel. The build up of charges during movement of the fuel can lead to high-energy spark discharges capable of igniting flammable fuel/air mixtures. This is particularly true with modern jet fuels of extreme purity (low-natural conductivity), high pumping velocities, and the use of microfiltration equipment capable of producing a high rate of charge separation and static build up in the flowing fuel. The use of SDA is optional by agreement between supplier and user, but its use is mandatory in an increasing number of cases. For example, international Jet A-1 supplies, U.S. military JP-4 and JP-8, and British DERD 2494/2453 grades. Common currently approved SDA I know of: DuPont Stadis 450 (3 mg/L). The composition is proprietary, but it is known it doesn't contain metals. The presence of SDA is extremely difficult to detect in small concentrations, therefore the conductivity of the fuel is measured by methods ASTM D 2624/IP 274.

Biocides. Biofor JF (a mixture of dioxaborinanes) is used to "disinfect" the aircraft when it is left standing, filled or partially filled, with doped fuel, but only intermittently to minimize possible deposition of boron compounds.

Antismoke additives. Although some are approved for postoverhaul test-cell operation of the engines, to my knowledge none are approved for flight because of their ash content.

Antimisting additive. Meant to eliminate the fireball which can be formed in an otherwise survivable crash. Opinions on their usefulness are still divided.

I hope having covered the subject. I've tried to keep myself adhered to the subject of ATF (jet fuels) additives, not touching the subject of aviation gasolines. I've also left out the subject of fuels' quality and specs., which belongs to a different thread altogether.

The big international chemical and additive manufacturers can surely add a lot of information to nirav2909.

 

[unclesyd]

Adding to 25362's excellant post.
Here is a list of the common tests used on jet fuel. They do more tests as needed.

http://www.intertek-cb.com/newsitetest/news/AviationFuelTesting.shtml

 

[25362]

If we deal with fuel specs. as in the list presented in the link brought by unclesyd, plus those I mentioned above, I'll add the following ASTM tests:

D93-02a, D1159-01, D1298-99e2, D1319-03, D2624-02, D3240-91(2001), D3242-01, D3701-01, D3948-99a, D4305-98a(2004), D4308-95(2000)e1.