OCR Text |
Show (a) Influence of heat input Fig. 21 shows the relationship between the concentration of emitted nitrogen oxides and the heat input. While the test burner has a design heat input of 37,000 kcal/h, the combustion load is ranged between 30,000 and 50,000 kcal/h. The horizontal axis indicates the amount of steam injected. As you can see the more the steam is injected, the less nitrogen oxide emitted. A lower heat input provides lower nitrogen oxide emission. However, the figure also shows that the effect not sustained if much more steam is injected. In other words, an increase in injected the amount of steam generates no remarkable effect past the saturation point. Through the above study, we estimated that the new burner system should require approximately 2 kg/h of injection steam to clear the regulated value of 150 ppm in an actual furnace under a design heat input of 37,000 kcal/h. (b) Influence of the air ratio Fig. 22 shows the relationship between nitrogen oxides emission and the air ratio. The figure clearly indicates that the concentration is highly sensitive to the air ratio in the system without steam injection. Increased air ratios emit more nitrogen oxides. An increase in nitrogen oxides is not so remarkable in a system with steam injection, and the air ratio has a relatively unimportant role. 3-4 Durability test The on-line test using an actual furnace also aims at proving thermodynamic capabilities of the new system as well as estimating the durability and reliability of the hardware. This is why the components are frequently actua ted and why the COG, containing many impuri ties such as tar and dust compared to the natural gas and LPG, is often used as a fuel for steel making plants. Through tests lasting some 1,500 hours, we successfully operated new system without experiencing any mechanical difficulties. Conclusions 1. Characteristics of a ceramic honeycomb for regenera tor media could be predicted by the simulation model described here. And, we found that there is a certain relationship between the honeycomb wall thickness and the changeover time. 2. Performances of Regenerative Burner System were confirmed. Thermal efficiency of the system was 83%, and fuel saving factor was 39% in the best. 3. Radiant tube surface temperature distribution showed much flatter than the one obtained with conventional radiant tube burner. 4. NOx emissions could be depressed under the regulation with a little amount of steam injection into the fuel gas at the burner gun. 5. Reliabilities of the system were examined at least for 1,500 hours. Therefore, a father trail is expected. - 9 - |