OCR Text |
Show ~) temperature, flame stability, and gas-phase residence time. The response curves of Figure 3, however, do not describe the individual effects of the derived system variables. It is important to establish the individual effects of stoichiometric ratio, oxygen enrichment, residence time, adiabatic flame temperature, measured kiln temperature, post flame oxygen flow, and post flame oxygen partial pressure on the response variables. It has been shown previouslyl,2 that, with respect to transient puffs from batch waste introduction, increasing kiln temperature increases puff intensity and that this is likely due to increased vaporization rates. This result is in contrast to typical kiln operating practice under steady-state operation, where increased temperatures are desirable because they increase the kinetic rates of oxidation reactions. Thus, for batch waste, while oxygen enrichment may increase the flame stability, flame stoichiometry, post flame oxygen flow, and post flame oxygen partial pressure, increased temperatures may drive the waste into the gas-phase more rapidly. We must try to quantify the relative magnitudes of each of these mechanisms. Figure 4 presents the calculated adiabatic flame temperatures and total flow rates through the rotary kiln simulator over the range of air and oxygen flow rates investigated by the first set of experiments (Table I). System residence time is roughly proportional to the inverse of the total flow. Comparison of Figure 4 with the response curves in Figure 3 shows that the regions of lowest peak area, peak height, filter weight, and peak CO responses correspond to the regions of low adiabatic flame temperature and high total flow (low residence time). The effect of high total flow can be explained by simple dilution. Additionally, the effect of increased temperature with respect to transient puffs is counterintuitive to normal steady-state incineration practice but consistent with increased vaporization rates. 11 |