4 Clay Element Information Clay Treatment of Turbine Fuel SOURCES OF SURFACTANT Surfactant contamination in turbine fuels has been attributed to the following sources: 1. Refinery – Naphthenic and sulfonic acids; also sodium naphthenates and sulfonates formed during acid and caustic treating. 2. Pipelines and transport trucks – Residuals from motor gasolines and heating oils adsorbed on pipe walls – then desorbed into turbine fuel. Also, pipeline additives are surfactants. 3. Ships and barges – Same methods as in (2) above. Also, sea water and acids in the fuel can combine to form sodium naphthenates and sulfonates. 4. Maintenance materials – Soaps, detergents, and steam cleaning residues. Rust preventives and descaling chemicals usually are surfactants or combine to form surfactants. The problems that are attributed to surfactants are principally related to their tendency to prevent the filter/separator from performing its functions, i.e., removing dirt and water from the fuel. The mechanics of this are a subject for a separate discussion but the results of such a failure are extensive. Water and dirt in an aircraft fuel system have well recognized dangers, but secondary effects are of equal importance. Bacteria can grow in the aircraft fuel system if water is present and the result can be corrosion of structural members and errors in the signals from fuel quantity gauging probes. Treatment of fuel to remove surfactants is usually done with attapulgus clay. In the refinery, large towers are built to contain many tons of bulk clay in a percolation column. However, complications of handling bulk clay outside of a refinery have led the industry to use cartridge-type clay vessels when it is necessary to treat the fuel in field installations. The key to good results in clay treatment is to keep the fuel in contact with the clay for as long a time as possible. We call this “residence” time. If you look at a clay particle, you see what seems to be a grain of fine (60 to 90 mesh) sand. But if you look within the grain with a microscope, you find This photograph was taken at 35000X and was reproduced from technical literature of Minerals and Chemicals Philipp Corporation.
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