The trade-off between N{sub 2}, NO, and N{sub 2}O under fluidized bed combustor conditions
NO and N{sub 2}O are harmful pollutants. Under fluidized bed combustor conditions the nitrogen of the solid fuel is partly converted to these species. The trade-off between N{sub 2}O depends on the fuel and fuel characteristics, the complex homogeneous and heterogeneous formation and destruction paths, temperature and residence times, and so forth. Because of these complex interrelations, it is necessary to study these processes separately and to analyze their relative importance. To obtain a better understanding of the formation and destruction paths of NO and N{sub 2}O, comprehensive studies have been performed in a laboratory-scale fluidized bed reactor optimized to obtain formation rates. The influence of the temperature and radicals on the NO and N{sub 2}O formation from HCN and NH{sub 3} and destruction reactions were studied. The results show that N{sub 2}O is formed only from HCN. Oxidation of NH{sub 3} forms NO and N{sub 2}O, HCN forms NO, N{sub 2}O, and N{sub 2}. 30 to 70% of NH{sub 3} are converted to N{sub 2} depending on bed temperature. In the case of HCN only 5 to 25% are converted to N{sub 2}. At temperatures below 800 C NO reacts with CH{sub 4} oxidation products to NO{sub 2}. Tests with HCN show that HCN conversion starts already at 700 C in the fluidized bed catalyzed by sand, N{sub 2}O is formed in significant amounts only in the presence of CH{sub 4}. The results of the NO and N{sub 2}O destruction tests show that the thermal mechanism is of minor importance. At 900 C N{sub 2}O destruction with H radicals can be seen. N{sub 2}O formation shows a maximum at 850 C. The NH{sub 3}, HCN, NO, and N{sub 2}O single particle formation characteristics of coke, bituminous coal, peat and spruce wood can be explained well with the results obtained from the gas reaction tests.
- Research Organization:
- Univ. of Technology, Vienna (AT)
- OSTI ID:
- 20006707
- Report Number(s):
- CONF-990534--
- Country of Publication:
- United States
- Language:
- English
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