Simultaneous removal of $SO_x/NO_x$ using $CuO/γ-Al_2O_3$ sorbent/catalyst

Abstract

To determine the characteristics of simulataneous removal reaction of $SO_x$ and $NO_x$ from flue gas over $CuO/γ-Al_2O_3$ sorbent/catalyst, desulfurization and denitrification reaction of $CuO/γ-Al_2O_3$ sorbent/catalyst have been determined in a thermogravimetric analyzer (TGA) and fixed bed reactor, respectiviely. Optimum operating condition of simultaneous removal reaction of $SO_x/NO_x$ over $CuO/γ-Al_2O_3$ sorbent/catalyst has been determined in a fixed bed reactor. The sulfation degree of alumina support in terms of the amount of sulfate ions presents on the support can be classified into three types (surface, slightly deep and bulk sulfations) as a function of reaction temperature and CuO loading. Surface sulfation (sulfate ions $<2.0\times10^{18} ions/㎡)$ occurs at CuO loading between 2-11wt% at reaction temperature 250-350℃, slightly deep sulfation $(2.0\times10^{18} ions/㎡<sulfate ions<3.4\times10^{18} ions/㎡)$ occurs with the loading below 4wt% at 350-600℃, and bulk sulfation $(3.4\times10^{18} ions/㎡<sulfate ions)$ occurs at the loading above 6wt% at 450-600℃. The bulk sulfation of alumina occurs in the presence of $SO_3$ decomposed from $CuSO_4$. The main product of deep sulfation is $Al_2(SO_4)_3$ which is identified by XRD peak at 2 θ = 25.4. With an addition of 5wt% NaCl, bulk sulfation occurs at lower temperature by 50℃ and lower CuO loading by 2wt% CuO. Rate of bulk sulfation increases with increasing gas velocity and then decreases with maximum value at 1.0 liter/min. It also decreases with decreasing the particle size and bulk sulfation does not occur above the size of 100㎛. These are caused from the increase of outward diffusion rate of $SO_3$ which is produced inside the $CuO/γ-Al_2O_3$ particle from the decomposition of $CuSO_4$. However, bulk sulfation rate of 100㎛ particles increases again with increasing sample weight because sulfation reaction between $SO_3$ and alumina resumes. Effect of heat treatment temperature and time ...