| OCR Text |
Show concentration due to increase of air comming through the clearance while keeping the air ratio of the burner at a constant level and reducing the furnace pressure little by little. With some heat treatment furnaces, "agitation air" is sometimes ejected from the periphery of the furnace to improve the agitstion of the air in the furnace. On the test, the influence of the agitation air over NOx concentration turned out to be about the same of the influence by the same quantity of air supplied to the burner as combustion air. To improve NOx performance of furnace, therefore, the total air quantity of the combustion air supplied to the burner plus the air comming from the openings shall be reduced as much as possible. Furnace pressure control or improvement of the sealing at openings are important not only for energy saving or for furnace temperature distribution but also for NOx control. Operating furnace temperature From the principle of NOx gbiieiaLiuu, high the operating furnace temperature, larger the produced quantity of NOx. The relation between the furnace temperature, of two tage burner and NOx:is as shown in Fig.83. Though NOx concentration of various industrial furnaces can be summarized by their operating temperature as shown in the drawing, the plot is quite extensive with much variation in NOx concentration. Fig.83 Furnace temperature of two stage combustion burner and NOx e o «H CO u CU - o u E a. a. •«_• x o z 40 30 20 1C TS-45U 13A specification Jity gas ISA u _ombvstic|>n 45x10 OLcal/h) 800 900 1000 1100 Furnace temp.(°C) 0; 1.4~,2-0(&) TTCTO 9 - 78 - |
