| OCR Text |
Show 3.2. Multiphase Fuel Furnace Complete details of the PSU-FCL multiphase fuel furnace (MPFF), shown schematically in Figure 2, have been published previously [11]. One burner was used to fire both the pulverized fuel and the coal-water slurry fuels [13]. Coal-water slurries were fed to the modified nozzle by a rotating- and reciprocating-piston pump. Pulverized coal was delivered to the burner via a vibrating screw feeder. As Figure 2 shows, the combustion chamber of the multiphase fuel furnace was fitted with windows near its horizontal center. This permitted a line-of-sight across the flame plume. This was done primarily for ignition time determination. Ignition times were defined as the transit time from the burner nozzle tip to the flame front. The flame front was located visually; the distance traveled by individual coal particles in the coal stream was measured using a cathetometer with HeNe laser line-of-sighting. It was assumed that the transit time was equal to the velocity within the burner tube. Ignition times were measured in terms of milliseconds (10 seconds, or msec). The test duration was limited only to the time requried to establish ignition. Prior to all neat coal and coal-water slurry ignition tests, the refractory walls of the MPFF were preheated to ca. 900°C using a distil late petroleum/air flame. Next, the natural gas/air pilot jet flame was ignited and the secondary combustion air turned on. It should be stressed that the secondary air was not preheated, nor was the primary air. Flow of the test fuel was then begun. For the coal-water slurry tests, all flow lines were pre-wetted with water prior to introducing the slurry. For all coal-water slurry ignition tests, the firing rate, excess air, and mean droplet size were held constant at 0.1 gallon per hour, 25% excess air, and 100 microns, respectively [11]. 22-9 |
