PYROMETRIC TEMPERATURE-MEASUREMENT METHOD AND APPARATUS FOR MEASURINGPARTICLE TEMPERATURES IN HOT FURNACES - APPLICATION TO REACTING BLACKLIQUOR

A specialized two-color pyrometric method has been developed for the m easurement of particle surface temperatures in hot, radiating environm ents. In this work, the method has been applied to the measurement of surface temperatures of single reacting black liquor char particles in an electrically heated muffle furnace. Black liquor was introduced in to the hot furnace as wet droplets. After drying, the resulted particl es were processed in different atmospheres corresponding to combustion , pyrolysis, and gasification at furnace temperatures of 700-900 degre es C. The pyrometric measurement is performed using two silicon photod iode detectors and 10 nm bandpass filters centered at 650 and 1050 nm. Thermal radiation is transferred using an uncooled fiberoptic probe b rought into the vicinity of the char particle, The key features of the pyrometric apparatus and analysis method are: (1) Single particle tem perature is resolved temporally at high speed. (2) The thermal radiati on originating from the furnace and reflected by the particle is accou nted for in the measurement of the surface temperature. (3) Particle t emperatures above or below the furnace temperature can be measured wit hout the need of a cooled background assisting the measurement in the hot furnace. To accomplish this, a minimum particle size is needed tha t is a function of the temperature difference between the particle and furnace. Particles cooler than the furnace can be measured if their d iameter is more than 0.7 mm. Surface temperatures of 300-400 degrees C above the furnace temperature were measured during combustion of blac k liquor char particles in air, In atmospheres corresponding to gasifi cation, endothermic reactions occurred, and char temperature remained typically 40 degrees below the furnace temperature. (C) 1996 American Institute of Physics.