An examination of the exothermicity of CFBC ash
The exothermic characteristics of ashes from the 183 MWe CFBC boiler operated by Nova Scotia Power Inc. were examined. Both bed ash and fly ash were investigated using a Parr 1455 Solution Calorimeter to determine what factors contribute to the exothermicity of CFBC ash. Heat release and rate of reaction were measured when CFBC ashes were hydrated with excess amounts of water. Results indicated that the most important factor in determining exothermic behavior is particle size. Fly ash released about 4 to 5 times as much heat as bed ash, or alternatively, converted 50% or more of its available CaO to Ca(OH){sub 2}. Its maximum heat release rate was about an order of magnitude greater than that of the bed ash. Similarly, fine bed ash particles examined here ({lt}75 {micro}m) released about 4 times as much heat as did larger bed ash particles. However, their overall effect was small because of the relative proportions of fine and coarse particles. Heat release rates for bed ash particles greater than 0.6 mm decreased dramatically, which is consistent with other observations that such particles are primarily comprised of fuel-derived material. It was clear for the bed ash that exothermic behavior was directly proportional to the CaO content of the ash. However, no such clear dependence has been found for the fly ash. Overall, for the bed material about one-fourth of the available CaO contributed to the exothermic reaction during the hydration process. It was also found that, exposed to air, CFBC bed ash lost much of its exothermic characteristics over a period of 48 hours. Information gained from this work has been put towards developing a safe and effective disposal method for CFBC ashes, and ash treatment options are being examined in light of the findings of this study.
- Research Organization:
- Natural Resources Canada, Nepean, Ontario (CA)
- OSTI ID:
- 20006701
- Report Number(s):
- CONF-990534--
- Country of Publication:
- United States
- Language:
- English
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