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Gas Turbine Fuel - Biological Contamination - (Biocide) Slime Preventer

CONTROL OF BIOLOGICAL CONTAMINATION IN GAS TURBINE DISTILLATE FUEL OILS

Bacterial activity in fuel oil storage tanks produces a build-up of biological slime which, if left undetected and untreated, can result in various operational problems for gas turbine power plants. Common problems include the plugging of fuel filtration systems, flow dividers and fuel burner nozzles etc. The accumulation of biological slime also promotes internal corrosion in fuel storage tanks and piping systems. Under anaerobic conditions hydrogen sulfide can also be produced which further accelerates the potential for serious corrosion.

Bacterial activity requires the combined presence of certain micro-organisms and water, and both these components are almost always present at some level in stored hydrocarbon fuels. Stagnant conditions at the bottom of storage tanks are ideally suited to support biological growth because both fuel and water layers are in intimate contact. However, even trace amounts of water suspended in distillate-grade fuels will support bacterial action. This is usually seen as a “haze” or opacity in the fuel, but inevitably results in the formation of biological slime and sludge. Distillates used as “stand-by” or “back-up” fuels are particularly susceptible because long and undisturbed periods of storage are usually involved.

The problem can be partially controlled by minimizing the accumulation of water in fuel storage tanks. However, complete elimination of water is virtually impossible, and even with distillate fuels the rate of settling is extremely slow. Therefore, for effective control it is necessary to improve the rate of water separation from the fuel and to kill the micro-organisms that cause bacterial activity. This can be achieved by treating with a fuel additive that includes a biocide/slime prevention component.

TURBOTECT ER-302 is a combination fuel additive, specially formulated to reduce the amount of water haze in mid-distillate fuels and kill most problematic micro-organisms at an early stage of development. The product provides rapid response in preventing the formation of biological slime in water-contaminated fuel.

Biological slime is caused by the degradation of fuels through the action of bacteria such as Pseudomonas aeruginosa, or fungi such as Cladosporium resinae and Candida tropicalis. Water in the fuel supplies nutrients and plays an important role in the metabolism of the micro-organisms, making it easier for growth to accelerate in the hydrocarbon phase. Middle distillates originating from naphthenic crude oils are particularly sensitive to this phenomenon because of their tendency to solubilize relatively large quantities of water during the refining process. At temperatures above 20°C these type distillates can hold up to 300 ppm or more of soluble water. However, once the fuel temperature decreases (usually long after leaving the refinery) the water becomes less soluble, and comes out of solution as a haze or opacity. The formation of free water droplets thus initiates conditions for the onset of bacterial activity.

TURBOTECT ER-302 can be used on a preventative basis to maintain a bright and clear appearance of middle-distillate fuels and to reduce the risk of slime formation. The product can also be used on a curative basis at slightly higher treatment rates in fuels where bacterial action has already initiated. It is toxic to both fungal and bacterial organisms and has good middle- to long-term activity even if treated fuel is transferred several times to other storage tanks or if temperature fluctuates widely. TURBOTECT ER-302 maintains the properties of the treated fuel such as colour, pour point, cloud point and heat of combustion. These properties are usually altered by the presence of water and/or slime.


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