PREDICTION OF BED MATERIAL ACTIVITY FROM CHANGES IN CARBON-DIOXIDE CONCENTRATION FOLLOWING COAL PARTICLE INJECTION IN THE FLUIDIZED-BED REACTOR

An electrically heated laboratory scale fluidized bed reactor was used for measurement of carbon dioxide concentrations from the devolatiliz ation of bituminous coal under conditions pertinent to a large scale a tmospheric pressure fluidized bed combustor (AFBC). Feeding a few part icles into the bed, which contained 1 or 2 g of char, produced an incr ease in CO2 concentration. The quantity of CO2 released from the fluid ized bed was found to be a function of fluidizing solid material, as w ell as the bed temperature and oxygen concentration in the fluidizing gas. Silica sand, magnesium oxide, calcium sulfate and partially sulfa ted Reed lime from a larger continuously fed AFBC (used bed material) were utilized as fluidizing solid particles. CO2 concentration profile s in the effluent gas were integrated and converted to the weight frac tions of coal particles that created disturbance in the CO2 level. For the silica sand bed, under the conditions of pyrolysis in the absence of oxygen, the quantity of CO2 evolved from the bed was increased fro m 1 to 3 wt% coal when the bed temperature was varied from 950 to 1150 K. For partially sulfated Reed lime, under similar conditions, the CO 2 quantity increased from 2.4 to 23.4 wt% coal. Magnesium oxide partic les had shown similar behaviour to silica sand solids, while the calci um sulfate bed had released a larger CO2 quantity, like the used bed m aterial. Thus, under similar conditions, the activity of the various f luidizing materials can be compared by CO2 measurement.