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Show INTRODUCTION The development of alternative fuels supply to replace or supplement the present petroleum fuels for power and steam generation is at its advent. Coal-derived liquids are seen as having increased availability in the coming decades, and, together with other heavy fuels, like tar sand and shale oils, will eventually serve as baseline fuels for gas turbines and boilers. Coal-derived liquids and other heavy fuels in general contain trace metallic components which, upon combustion, form vapors and fine particles depositing on the internals of gas turbines and boilers or emitting into the atmosphere. The emission of fine aerosols of toxic trace elements in itself is a serious threat to the environment, especially to the human and animal health (Natusch, 1974). The environmental aspect of emission requires careful attention, however it is out of the scope of this paper. Deposition of trace metal particles on turbine and boiler internals creates severe technical problems: a. Deposition of certain salts at high temperatures, especially in molten form, may cause severe corrosion problems. b. Deposit build up or fouling results in distortion of gas passages and reduces the aerodynamic efficiency of turbines. c. Deposit adherence to hot-section materials of boilers and turbines results in a reduction of heat transfer rates decreasing the thermal efficiency and useful life of tne construction material. d. Deposit accretion results in a loss of operational efficiency due to periodic shut down and cleaning requirement. 1.5.3 |
