SIMULTANEOUS IN-SITU MEASUREMENT OF TEMPERATURE AND SIZE OF BURNING CHAR PARTICLES IN A FLUIDIZED-BED FURNACE BY MEANS OF FIBEROPTIC PYROMETRY

A pyrometric instrument for the measurement of the temperature of burn ing fuel particles in fluidized bed furnaces is presented. The instrum ent is equipped with a fiberoptic probe which is inserted into the flu idized bed. A theory based on radiative transfer and analysis of the s tatistics of fuel particles is developed, which allows for the extract ion of statistical expectation values of the size of the fuel particle from the pyrometric signals along with the temperature. Experimental results obtained with the instrument in a pilot scale fluidized bed fu rnace of 500 kW thermal power are presented. The pyrometrically measur ed two-color ratio temperature of the fluidized bed is found to be in very close agreement with an independent thermocouple reading. The emi ssivity of the bed is found to be close to unity. The elevation of the fuel particle temperature above the bed temperature varies from about 50 up to about 600 degrees. The temperature elevation of the fuel par ticles is found to decrease with increasing particle size in all exper iments.