| OCR Text |
Show investigated the temperature dependence of the viscosity of the iron-rich particles might become important. The temperature dependence of the sticking probability of the aluminosilicates was estimated using the viscosity argument outlined earlier. The viscosity was calculated from the correlation of Riboud, Roux, Lucas, and Gaye (1981), using the average composition of the furnace exit ash, without iron. The particles were assumed to become perfectly sticky at a viscosity of 8 Pa.s. These assumptions and approximations gave the sticking probability distribution shown in Figure 10. This distribution, in conjunction with the other values chosen for the adjustable parameters in the model, reproduced the observed deposit growth. The highest possible temperature of the particles and deposit was equal to the temperature of the radiating furnace enclosure, 2755°F (1786 K). Since there has been no test of the ability of the sticking probability distribution to explain deposition at higher temperature, the portion of the distribution above 2750°F is shown dashed in Figure 10, to indicate that this portion of the distribution has no influence on the present results. In spite of the small fraction of aluminosilicates which are sticky, they make a significant contribution to the observed deposition rates at high temperatures. Aluminosilicates are estimated to contribute to the sticking probability an amount equal to 30% of the iron-rich particles at 2694°F (1752 K) and 50% at 2755°F (1786 K). The initial deposition rate at short times is directly dependent on the sticking probability at the temperature of the incoming particles 2694°F (1752 K). The process of deposit growth was simulated using Eq. 3, with 1 minute time intervals. The surface temperature was calculated at each 29 |
