The Selective catalytic reduction of NOx by urea as reducing agent has been carried out in a fluidized bed reactor(0.1m-ID×2m). Fresh and bulk sulfated CuO/γ-$Al_2O_3$ were used as catalyst in this study.
The effects of reaction temperature, gas velocity, urea decomposition temperature and α(Nreducing agent/$N_NO$) on $NO_x$ reduction have been determined. The inlet concentration of NO in the reactor was 400ppm and the outlet concentrations of NO, $N_2O$ and $NH_3$ were measured by ND-IR type gas analyzer. The temperature range was 250-500℃ as 50℃ intervals and the flow rate of simulated flue gas was varied from 1 to 3Umf at each reaction temperature.
The optimum α was 2 over the fresh CuO/γ-$Al_2O_3$ and 1.5 over the sulfated CuO/γ-$Al_2O_3$, respectively. The optimum decomposition temperature of urea solution was 350℃.
$NO_x$ reduction by urea increases with increasing the reaction temperature and exhibits the sharp maximum at the temperature range, 300-350℃ and then decreases because of oxidation of $NH_3$ over fresh CuO/γ-$Al_2O_3$ catalyst. NO reduction decreases with increasing superficial gas velocity.
The optimum temperature range of NO SCR over the bulk sulfated CuO/γ-$Al_2O_3$ catalyst was 400-450℃ with the sulfated catalyst. NO removal efficiency was higher than that with the fresh catalyst in a fluidized bed reactor.
The amount of $N_2O$ formation over the fresh and bulk sulfated catalyst increases with increasing gas velocity under 5% of NO in the feed stream. The amount of $NH_3$ in flue gas increases with increasing gas velocity and decreases with increasing reaction temperature under 5% of reducing agent of feed stream. The amount of $N_2O$ formation and $NH_3$ in flue gas stream was very little compared with NO SCR by $NH_3$.
Total NO removal rate per gram of catalyst increases with increasing gas velocity($U_g$).