OCR Text |
Show percentage variation around baseline, and the figures are indicated as percentages because, although the percentage reduction relative to a specific control technique is predictable, the baseline emission on each application is different. Consequently, actual emissions could be very misleading if quoted out of context. The burners were designed for low excess air operation only, with no consideration for N0X; therefore, there were no refinements on the burners to accurately control fuel/air ratios. You will note that although the "burners out of service" (BOOS) technique offered slightly greater percentage reductions below 3% oxygen, "bias oil firing" offered reduction to 1.4% oxygen with all burners in service. In any event, the key to lowest possible N0X is in the baseline set up by the burner and operating conditions. This, of course, intensifies the requirements for a low N0X burner. Figure 12 indicates N0X versus 02 data points while firing oil only, 50% gas and 50% oil firing, and gas firing only at ambient combustion air temperatures. A large number of tests were conducted over several months, and each individual data point could not be shown in Figure 12 since many tests showed practically the same concentration. The firing of oil only showed a large dependence of nitrogen oxides on excess oxygen, while gas firing showed only a slight dependence. There was nearly a 12-30 |