| OCR Text |
Show predicted to remain unreacted at these conditions. Injection of CH30H at 950 K (Figure 4c) forms about 220 ppm CO, 16 ppm CH20, 6 ppm H2, and about 48 ppm CH30H remains in the mixture. The amount of CH20 and CH30H rapidly decrease with an increase in the injection temperature. At 950 K, NO is completely converted to N02 with trace amounts of HN02 and HN03 (0.6 ppm 0.1 ppm, respectively). Injection of the H20/CH30H mixture at 900 K (Figure 4d) is also predicted to completely convert NO to N02 with trace amounts of HNOiHN03• However, the amounts of CO, CH30H, CH20, H20 2, and H2 in flue gas are substantially lower (i.e., 124, 11, 4, 1.6, and 1.4 ppm respectively). These amounts also rapidly decrease at slightly higher injection temperatures. Thus, injection of hydrogen peroxide in the mixture with methanol dramatically decreases the concentrations of combustible products in flue gas. The selected reaction mechanism includes 284 elementary steps which dictate the overall perfonnance of the process. In order to better understand what reactions are the most significant in the mechanism, a sensitivity analysis was performed through the use of the SENKIN kinetic code developed by Lutz et al. (1991). In this program, the nonnalized sensitivity coefficient is Wj,i = (A/Z) (az/aA), where A is the pre-exponential factor of the rate constant of each elementary reaction and Z is one of the process variables which include temperature and concentrations of all components. Thus, sensitivities of all concentrations (and temperature) to each rate constant can be calculated, and the most important reactions can be identified. Figure 5a presents the NO sensitivity plot for the process of H20 2 injection at 850 K. Important reactions which are responsible for the fonnation and consumption of NO are shown with their associated numbers. In the presence of H20 2, the total amount of OH radicals increases due to dissociation via (-37) 13 - |
