Park JJ  Lee SJ  Ryu IS  Jeon SG  Park YS  Moon SH

Vol. 20,  No. 4, pp. 390-397, Dec.  2014

N2O decomposition Sewage sludge Fluidizing media Fluidized bed incineration

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This study was performed to investigate the effects of fluidizing media on N2O production in fluidized bed incineration of sewage sludge. The fluidized media were prepared in a form of 2 mm bead by mixing zeolite powders in our lab. Sand having 0.4 mm of the mean size showed 0.44 m/s of minimum fluidization velocity (Umf), while the prepared zeolite media 0.5 m/s. When the ratio of fluidizing media height to the inside diameter of the incinerator (bed aspect ratio) increased from 1.4 to 3.1, it was found that Umf of the zeolite media was varied from 0.5 m/s to 0.7 m/s. Under the operation conditions in 1.79 of excess air ratio, 909 ℃ of bed temperature and ca. 1.65 m/s of superficial velocity, as the weight of fluidizing meadia was increased, O2 concentration in the flue gas was slightly decreased, and CO2 increased. Above 6 kg of fluidizing media weight (1.98 of bed aspect ratio), it was observed that N2O concentration was significantly reduced, which might result from the decomposition of N2O on the zeolite media rather than transformation of N2O to NOx. On the other hand, in a variation of the zeolite media mixing ratio to sand and bed temperature at a constant total bed height, significant difference was exhibited in N2O emission concentration according to the temperature. Considering the operation temperature in the incineration, the effective calcination temperature of the zeolite media was suggested to be around 900 ℃.