Al2O3, sand, Ti system, Cr, ZrO2 and zeolite system were investigated as a candidate for N2O decomposition, where some zeolite substances showed 100% of N2O conversion at 650 ℃ as reaction temperature. Apart from FAU zeolite, BEA, MOR and ZSM-5 ones were stable even at a high temperature of 850 ℃, and thus they were highly applicable to a fluidization bed material for N2O reduction.

Raw materials of zeolite were zeolite B, zeolite M or a mixture of zeolite B and M, which are mixed with organic and inorganic binders to prepare paste for extrusion. The mixing ratios of the raw materials were adjusted to get desired compression strength and bulk density. The final extruded material was active in N2O 100% conversion at the reaction temperature 850℃.

The prepared zeolite bed materials were examined in minimum fluidization velocity (Umf) by cold mode test. The 0.4 mm of sand showed 0.44 m/s of minimum fluidization velocity, 6 mm of zeolite beads needed higher velocity of 2.11 m/s than sand. When 6 mm of zeolite was mixed with sand, it was observed that the fluidization of the mixture was similar to that of sand. In zeolite bed materials size is less than 2 mm, minimum fluidization velocity was below 0.6 m/s, implying that the zeolite materials might be suitable for an application to fluidization incineration.

Fluidization incineration was performed by feeding 10 kg/h of sewage sludge. When sand was used as a bed material, operation conditions were varied in excess air ratio and bed temperature in order to find out stable operation conditions and N2O emission. Sewage sludge in dried powder form was supplied into the bed part. Bed temperature and excess air ratio were adjusted between 850 ℃ to 950 ℃, and 1.2 to 1.7, respectively. As a result, N2O was emitted up to 500 ppm in concentration. On the other hand, the use of zeolite bed materials below 1 mm size could reduce N2O emission to around 100 ppm. Furthermore, when the additional catalyst for N2O decomposition was installed in near freeboard of the incinerator, the N2O concentration in exhaust gas was below i.e. about 50 ppm. As our observation, the used zeolite bed material shows same activity of N2O decomposition, it was revealed that the zeolite bed material could not be affected in the activity under the operation conditions.