OCR Text |
Show determine the growth of particles and their final phase. Particles, in their early stages of formation, are believed to be in liquid form, e.g. molten salts. These aerosols, depending on their residence time, may coalesce with other particles or grow by condensation and coagulation to form multicomponent aerosols. Depending on the thermal history, a multicomponent aerosol may be completely or partially solidified. Thus the particles that approach a collecting surface may be in liquid (molten), solid or multiphase form. Delivery rate of particles and condensable vapors to the collecting surfaces will be determined by Brownian diffusion, thermophoresis, turbulent eddy diffusion and inertial impaction. However the capture efficiency will be influenced by the sticking characteristics of both particles and collection surfaces, which in turn are functions of chemical nature of both the particles and surfaces and their temperatures. Corrosive effects of these deposits and their ultimate role in the efficiency reduction of the power cycle also depend strongly on the temperature of deposit. Combustion test studies have indicated that the deposition rate is influenced by pressure, temperature, particle size, and particle composition and concentration. Composition Effects: Identification of the chemical composition of deposits and their quantitative relation with the trace element contents of the fuel is of primary concern. While these relations have to some extent been established for petroleum based fuels, the present knowledge about coal liquids is very limited. Early observations of deposition and hot corrosion from the combustion of clean distillate fuels have identified anhydrous sodium 1.5.14 |