DEMULSIFIERS FOR GAS TURBINE FUEL OIL TREATMENT PLANTS
Heavy residual-grade oils and crude oils are normally processed in a fuel oil treatment plant (“FOTP”) prior to combustion in gas turbine engines. This treatment, known as “fuel washing”, is performed to reduce the level of water-soluble sodium and potassium salts to within OEM specification limits – such as 0.5 or 1.0 ppm Na+K maximum. Sediments and other water-extractable impurities are also removed during the washing process.
A quantity of fresh water is injected into the raw fuel and thoroughly mixed to create a water/oil emulsion. Water-soluble contaminants are thereby diluted and transferred into the water phase, along with water-wettable solids and sediments. The emulsion must then be quickly broken to enable efficient separation of the water and oil phases. This is achieved by using either centrifugal or electrostatic separation equipment, plus the addition of a chemical demulsifier. Extracted impurities leave the process via an effluent water stream and purified fuel is pumped to the treated fuel storage tanks.
Chemical demulsifiers play an important role in both centrifugal and electrostatic fuel oil treatment plants, and greatly enhance the separation efficiency of water/oil emulsions. Being surface-active agents, demulsifiers also improve the wettability of entrained solids and sediments, and influence the quality of discharged effluent water.
Properties of crude oils and residual-grade fuels vary considerably, and care should be taken when selecting an appropriate demulsifier for a particular application. Products need to be fast acting and formulations should match the chemical properties of the candidate fuel. Other selection criteria include the type of physical separation process involved (ie. centrifuge or electrostatic), process operating temperature, wash water quality and quantity etc..
Experience has proved that a range of different demulsifier formulations must be available to satisfy the various types of fuel and process conditions encountered in this market. Optimum performance will not be achieved by using only one “universal” product. The Turbotect demulsifier product line has therefore been specifically developed to address a wide range of candidate gas turbine fuels and process conditions, but customized blends can also be formulated for unique fuels or specific applications. Important Turbotect demulsifiers are as follows:
TURBOTECT EP-169, EP-170, EP-171, EP-211, EP-343 and ER-52B
In order to pre-select the most effective demulsifier, Turbotect normally recommends that preliminary laboratory tests be performed using representative samples of the candidate fuel. The laboratory test procedure should also duplicate actual on-site process conditions as closely as possible. Demulsifier selection and optimum dosage can then be confirmed by on-site field testing under actual treatment plant operating conditions. Note that demulsifier action is enhanced by efficient mixing into the fuel oil stream, normally at an injection point before the introduction of wash water. This ensures thorough dissolution and improves the speed of migration of the demulsifier to the oil/water interface.
The following general selection guidelines are useful if laboratory pre-testing is not possible:
|Optimum and cost-effective demulsifier performance calls for an individually formulated product, developed for the specific fuel and fuel treatment plant operating conditions