OCR Text |
Show Pulverized SRC Tests The pulverizer and delivery systems for the pulverized SRC tests were similar to coal pulverizer and delivery systems used in other facilities at PETC. The pulverizer system included a Mikropul impact mill with integral classification, a storage hopper, a lock hopper, and a variable-speed screw feeder. The SRC-I was pulverized to a nominal particle size of 90 percent minus 325 mesh and conveyed by the primary combustion air stream to the burner nozzle. The burner nozzle, contained within an air register with eight adjustable vanes, was water-cooled and was developed previously for pulverized 9 SRC tests at PETC. The nozzle was designed to burn approximately 125 pounds of SRC per hour. The pulverized SRC tests were performed for a total of 18 hours in two days. Because of the design limitation of the burner, the boiler was operated at approximately half load (1,700 to 1,900 pounds steam per hour). The excess oxygen level varied between 3 and 4.5 percent because of fuel flow fluctuations. The flame was quite similar to that when burning molten SRC; however, it was somewhat brighter and bushier. Although the boiler was tested at half load, the flue gas temperatures were about the same as when firing No. 6 fuel oil at full load. The carbon-conversion and boiler efficiencies during the pulverized SRC tests at half load were comparable to those of oil, slurry, and molten SRC tests at full boiler load. Pollutant Emissions The emissions of NO during the SRC tests were high, ranging from 499.8 ppm, or 0.668 lb/MBtu, to 845 ppm, or 1.115 lb/MBtu, when burning all three forms of SRC (as compared to 208 ppm, or 0.265 lb/MBtu, for oil firing). However, due to the short time span available for testing, no attempt was made to minimize NO emissions via combustion modifications. The emissions of S02 when burning all three forms of SRC were comparable to emissions when firing oil because of the low sulfur content (0.8 14-13 |