Removal of $SO_x/NO_x$ using $CuO/γ-Al_2O_3$ and limestone in a fluidized bed reactor

Abstract

Sulfation of the alkali-salt promoted CuO/$γ-Al_2O_3$ sorbent, Selective Catalytic Reduction (SCR) of NO by $NH_3$ and the simultaneous removal of $SO_X$/$NO_X$ have been carried out in a thermogravimetric analyzer (TGA), a fixed bed reactor and a fluidized bed reactor, respectively. Also, the thermal decomposition characteristics of the sorbent and alkali salt in $N_2$ gas was determined by differential thermal analyzer (DTA). An addition of alkali-salt to the sorbent increases $SO_2$ sorption and reduces the temperature range for the bulk sulfation of CuO/$γ-Al_2O_3$ sorbent. The main product in sulfation of LiCl-promoted sorbent above 450 ℃ is found to be $Al_2(SO_4)_3$ by X-ray diffractormeter. The rank for sulfur removal capacity of alkali-salts as additives in CuO/$γ-Al_2O_3$ sorbent is found to be LiCl ＞ LiBr ? NaCl ＞ LiF ? KCl ? NaF. In the cycle test of sulfation-regeneration at 500 ℃, $SO_2$ removal capacities of LiCl- and NaCl-promoted sorbents are over 3 times than those of the promoter-free sorbent for up to 30 cycles. The optimum amount of CuO loading in alumina support for $NO_X$ removal is 8 wt.%. The optimum temperatures of the fresh and sulfated CuO/$γ-Al_2O_3$ in the selective catalytic reduction (SCR) of NO are found to be 350 and 450 ℃ in a fixed bed reactor, respectively. NO reduction with the sulfated catalyst is somewhat higher than that of the fresh catalyst. The amount of $N_2O$ formation over the fresh and bulk sulfated catalysts is below 10% of NO in the feed stream. Intermediate in NO reduction by $NH_3$ over the bulk sulfated catalyst is found to be ammonium sulfate from IR study. The activation energies of the fresh, surface and bulk sulfated catalysts are found to be 29.4, 76.6 and 76.3 kJ/mol, respectively. The optimum temperatures of the fresh and sulfated CuO/$γ-Al_2O_3$ in SCR of NO are found to be 250 - 300 ℃ and 300 - 450 ℃ in a fluidized bed reactor, respectively. With the sulfated catalyst, NO removal efficiency is high...