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Show with oxygen and natural gas using both the "A" Burner and conventional burners. compared to the "A" Burner, the NOx level was two orders of magnitude higher for a swirl type burner with a refractory block and almost one order of magnitude higher for a co-current burner without a refractory block. The comparison between the "A" Burner and the co-current burner was made with a controlled flow of air into the furnace to simulate an air leak. The results are plotted in Figure 5. The firing rate was 0.8 MHBTU/hr and the furnace gas temperature, as measured with a suction pyrometer near the flue, was in the 2800-2900°F range. The NOx level increased linearly with increased air leakage rate for both burners but the level for the "A" Burner was always substantially lower. The amount of NOx formed with the "A" Burner was always well below the federal codes for burning natural gas. 0 .25 FIRING RATE· 0.8 M BTU/HR 0.20 0.15 0.10 AIR LEAKAGE RATE· CFH Fig. 5 - Nitrogen oxide formation as a function of air leakage rate for burning natural gas and oxygen in a concentric jet burner and an "A" burner. • The "A" Burner has been scaled up and tested in a number of industrial furnaces. Detailed results for some of these installations have already been reported (3&4). The industrial burners range in size from 1-2 MHBTU/hr (for applications 333 requiring a multiple of small burners) to 20 MMBTU/hr. To date, the fuels used include natural gas, coke oven gas and fuel oil (#2 and #6). The favorable operating results (low flame temperature, low NOx ' uniform temperature distribution, and large turn down ratio) obtained in the experimental furnace were also achieved with the scaled up "A" Burners in industrial furnaces. The conversion of a furnace from air to oxygen using "A" Burners usually results in fuel savings of 50~ or more. This often leads to a reduction in the number of burners required. This reduction can be made while still maintaining the desired temperature distribution in the furnace. As already noted, individual oxygen nozzles can be changed to obtain any pattern of jet velocity and orientation required to achieve a given furnace temperature distribution. A picture of a 10 MHBTU/hr "A" Burner for natural gas is shown in Figure 6. The burner is 4 1/2 inches 0.0., water cooled, and most of the component parts are made with copper. A refractory layer is attached to the face to reduce heat losses. This burner was originally tested in an industrial furnace in 1980. A bank of five steel reheat furnaces were installed with "A" Burners in 1981(2). Extensive operating experience has been obtained with steel reheat furnaces. These include soaking pits for ingots as well as batch and continuous furnaces for slabs and blooms. The "A" Burners have also been demonstrated in glass and copper melting furnaces. For all of these applications, the auxiliary equipment such as piping and valve skids, microprocessor controls, safety interlocks, etc. have also been developed and demonstrated. Fig. 6 - Picture of a 10 MMBTU/hr "A" Burner for natural gas. |
