| OCR Text |
Show through the same passage, and through increasing the surface area of the mediwn, it is possible to obtain a high h:t exchange efficiency. The temperature of the combustion air rises to near that of the furnace temperature and e temperature of the final exhaust gas after passing through the burner is less than 200 C. In Fig. 2 is shown the combustion taking place in Burner A. The representative fuel used herein shall be natural gas. Gas and combustion air fed to Burner A and, after combustion inside the furnace, passes through the regenerator on the Burner B side and discharged outside. At this time, the major part of the high heat remaining in the exhaust g~ is passed to the regenerator. After a set time, when the regenerator is fully regenerating, the reversing system Will start to operate and the combustion will shift to the Burner B side. At this time, the combustion air of Burner B will pass Through the regenerator of the Burner B side and after being heated to a high temperature will be used for combustion. The time interval for reversing is from 20 seconds to about 3 minutes while the shape, quality, heat properties and filling method are decided by the capacity as well as the furnace temperature and control characteristics. The reason why the FDI and the regenerative system are the best combination is because the low NOx performance of the FDI is best displayed in a combustion using high temperature preheated air inside a high temperature furnace. Looking at this from a different aspect, by using the regenerative system as a high temperature furnace, a high temperature preheated air will be obtained and the NOx emission will rise extremely high and so there will be the need to combine this with a highly effective NOx reducing technique. If a regenerative system with no NOx reducing measures is used with a furnace temperature of over 1200 C, the preheated air temperature will rise to more than 1000 C and so the NOx emission will attain a level of 1000 - 2000 ppm (02 = 0%). This level is completely unacceptable when considering the environment. To create a condition in which this high efficiency regenerative system can be used without problem, a low NOx technique that requires no special denitration device, using combustion only, is indispensable. FDI indeed matched this condition. The FDI and the regenerative system have a relationship meeting all the requirements necessary for each other. The regenerative system is receiving worldwide attention and its use is accelerating. It is believed that the use of FDI combustion will also accelerate together with this. 2. The Perfonnance of the FDI and its Application to Actual Furnaces Next, an introduction will be made as concerns the basic performance of the FDI. For the reasons mentioned earlier, a high preheated air can be obtained with the regenerative system. The experimental furnace was shown in Fig. 3. The inside dimension of the furnace is 1.4 x 1.4 x 6.0 m. The burner was operated mainly for the combustion at about 840 kW, while a load device (350kW) was equipped at the furnace bed in order to make variations of various parameters with keeping the constant furnace temperature. The parameters deciding the performance of the FDI The parameters deciding the performance of the FDI are as follows: 1. Injection velocity of the air and the gas 2. Position of the air and gas nozzles 3. Angle of the gas nomes 4. Air ratio The effects to the NOx of the above four parameters are shown from Fig. 4 to Fig. 7. In short, it was found that to effectively obtain a low NOx 1. The injection velocity of the air should be increased. 2. The distance between the air nomes and the gas nomes should be increased. 3. The gas nomes should be angled away from the air injection flow. 4. Surplus air should be reduced as much as possible. Based on this, the ideal relationship with the control equipment such as a blower, as well as the ideal relationship |
