High temperature corrosion by combustion gases produced by burning liquid fuels containing sulphur, sodium and vanadium.

High temperature corrosion, at 730° C, by combustion gases produced by burning liquid fuels in a laboratory combustor has been investigated. A selected range of steels and alloys (mild steel, stainless steel type 347, Nimonic N90, N105, and IN657) have been tested in the combustion gases using fuels containing varying amounts of impurities in the range of 0 - 6% sulphur, 0 - 60 ppm sodium, and 0 - 300 ppm vanadium. On the basis of the comprehensive results a computer programme was written to predict corrosion rates of mild steel by combustion gases produced by burning fuels containing impurities such as sulphur, sodium and vanadium. The programme was tested, and the predictions which included the change of fuel were experimentally verified. Oil soluble additives have been used to show the effect on corrosion rates of the materials tested. By using X-ray diffraction analysis of the oxide layers, and with the help of electron microscopy, an attempt was made to investigate the mechanism of corrosion in the individual and collective presence of sulphur, sodium and vanadium-supplied by the test fuels. It is shown, for example, that the presence of sulphur in the fuel helps in the formation of FeO in the surface oxide layers.
The ignition delay time or simply the ignition delay, which is the time lapse between the introduction of a fuel droplet into a heated atmosphere and its eventual ignition, was measured for all the test fuels. It is shown that the addition of elemental impurities such as sulphur sodium and vanadium have no significant effect on the ignition delay of the fuel but the addition of oil soluble additive makes the, ignition delay - temperature, curve steeper at the operating temperature and also reduces, corrosion of materials. Light hydrocarbon fuels having lower ignition delay than Kerosene at the operating temperature can be used as an additive to reduce the formation of sulphur trioxide in the combustion gases.

A thesis submitted to CNAA in partial fulfilment of the requirements for the degree of Doctor of Philosophy.