OCR Text |
Show Flame and wall temperatures and compositions of gaseous and solid products of combustion were characterized as a function of residence time (distance down the furnace centerline) by sampling the combustion environment through ports distributed along the vertical axis of the furnace (see Figure 2). The transit time between measuring positions was determined by correcting volumetric flow rates to give local flame velocities. Volumetric changes caused by molar and temperature variations were considered. Probes designed and fabricated at the PSU-FCL were used to measure: (a) the internal furnace wall temperature (thermocouples), (b) the gas temperature (suction pyrometer), and (c) the gaseous and solid products of combustion (various water-quenched gas and particulate sampling probes). Schematics of the probes used are shown in Figures 3-5. Gaseous product of combustion concentrations were measured on-line in the flame and exhaust gases using nondispersive infrared [CO, CO^] , paramagnetic [0-], and chemiluminescent [NOX] instrumental techniques. Captured solid samples were subjected to routine elemental analyses. The progress of combustion in the pulverized coal flame was monitored in two independent ways by measuring both the appearance of carbon dioxide in the gaseous products and the disappearance of elemental carbon in the char. Thus, carbon burnoff was resolved as a function of time. With these data on carbon burnoff and residence time, important events in the initiation and termination of the pulverized coal flame were timed, ignition and burnout, respectively. Ignition time is defined as the residence time required for 1% coal-carbon burnoff; burnout time is the time required for 100% carbon burnoff. 17-14 |