Burner Improvements and Flame Quality Studies on a 650 MW Supercritical Pulverized Coal Boiler

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burner shown in Figure No.3 was selected for installation in Avon 9. Also, see photos, Figure No.4. This air register provided a very stable flame with a high degree of turbulence. This burner also has a very distinctive flame shape. Most of the testing and furnace observations were done with this burner in combination with different impeller designs. The windbox flow distribution study involved both airflow model testing and field airflow measurements. A unique measurement technique was employed by the consultant, Nels, Inc., utilizing large vane anemometers which were fitted over all 48 burners. This was able to give airflows on all burners simul­taneously. The vane anemometer is shown in the Figure No. 5 photo. The model testing was unable to uncover any significant problem with the wind­box. It was, therefore, concluded that any flow maldistribution was caused by the air registers. As an additional improvement, however, baffles to help turn the flow to the rear windbox were tested in the model (see Figure No.6). Although the model testing couldn't justify the need for the baffles, the test with the baffles also showed a good air distribution. On this basis, it was decided to install the baffles anyway. Prior to starting the unit, after in­stallation of the new air registers and windbox baffles, the boiler was field tested using the vane anemometers • . The results of these tests showed excellent secondary air balance, front to back and side to side (see Table No.2). The burner change on Avon 9 was completed in December 1985 during a long out­age when the unit was converted to balanced draft and a new precipitator in­stalled. Following the start-up, considerable unexpected combustion problems ensued. This led to an extensive investigation and testing program, the re­sults which are discussed in the following text. Burner Testing A number of combustion tests and flame pattern studies have been conducted from early 1986 to the present on the Avon 9, Eastlake 5 and Ashtabula 50 MW boilers. The testing attempted to evaluate combustion problems with both the old and new air registers. Eastlake 5 testing was done to obtain a base­line condition assessment of the original B&W cell air register. Primarily the results attempt to evaluate the effect of burner configuration on: flame shape, furnace slagging, furnace gas temperature and CO in the burner zone. Burner Characteristics The results of the testing provide a comparison of furnace conditions created by the new Avon 9 high turbulence burner compared to that of the original B&W cell burner. The B&W cell burner exhibits a fairly lazy flame. The new air register has a very distinct flame shape which has a strong amount of spin promoting rapid burning! Flame ignition is close to the nozzle tip and the flame has a well-defined uniform envelope. The flame created by the original B&W cell burners is more rolling, smoky and exhibits loose flame tails. The photograph in Figure No. 7 shows ~he flame shape of the new burner during an Eastlake 5 start-up. During one phase of testing, full size air registers were airflow tested. From the laboratory airflow tests, the throat velocity profile shown in Figure No. 8 was developed comparing the two air registers. It is apparent from this data the new air register is more effective in direct­ing flow to the center of the burner than the old cell burner. This register also imparts a strong 30° spin rotation.