| OCR Text |
Show American Flame Research Committee, International Flame Research Foundation, Fall International Symposium, Akron, Ohio, October 4-6, 1983. AN INTERPRETATION OF TIME-RESOLVED OXYGEN CONCENTRATION MEASUREMENTS IN COAL-BURNING FLUIDIZED BEDS Peter M. Walsh, Chengzhi Li, and Janos M. Beer Energy Laboratory Department of Chemical Engineering Massachusetts Institute of Technology Cambridge, Massachusetts 02139 SUMMARY Oxygen mole fractions were measured during combustion of high volatile bituminous coal in an atmospheric pressure fluidized bed using in situ sensors based on Pt,0 ;ZrO ;0 ,Pt electrochemical cells. The response time of the sensor is relatively rapid (30 ms) and the time-dependent cell potential therefore provides information on the frequencies and limits of the 0 concentration fluctuations in AFBC. The random character of the 0 fluctuations and the possibility that the outer Pt electrode catalyzes 0 reactions complicate the interpretation of the data. At heights not too close to the air distributor two peaks are typically observed in the probability density distribution of the cell potential. One peak corresponds to an 0 mole fraction of the same order of magnitude as that estimated by assuming equilibration of 0 with CO and CO . The other peak typically corresponds to mole fractions large enough that 0 consumption by CO and hydrocarbons at the Pt surface may be neglected. The shape of the high-0 peak is roughly that of a gamma probability density function. The fit of an analytic function to the distribution is convenient for the manipulation of the data, for example in the calculation of the time-averaged 0p. When the 0 consumption reaction is pseudo-first-order, the distribution of cell potentials is equivalent to a residence time distribution. *Visiting Scholar, Department of Chemical Engineering, MIT. Permanent Address: Department of Thermal Engineering, Northeast Institute of Technology, Shenyang, Liaoning, China 110006 1 |
