NO(X) REMOVAL WITH COMBINED SELECTIVE CATALYTIC REDUCTION AND SELECTIVE NONCATALYTIC REDUCTION - PILOT-SCALE TEST-RESULTS

Pilot-scale tests were conducted to develop a combined nitrogen oxide (NO(x)) reduction technology using both selective catalytic reduction (SCR) and selective noncatalytic reduction (SNCR). A commercially avai lable vanadium- and titanium-based composite honeycomb catalyst and en hanced urea (NH2CONH2) were used with a natural-gas-fired furnace at a NO(x) concentration of 110 ppm. Changes in SNCR chemical injection te mperature and stoichiometry led to varying levels of post-furnace ammo nia (NH3), which acts as the reductant feed to the downstream SCR cata lyst. The urea-based chemical could routinely achieve SNCR plus SCR to tal NO(x) reductions of 85 percent with less than 3 ppm NH3 slip at re ductant/NO(x) stoichiometries ranging from about 1.5 to 2.5 and SCR sp ace velocities of 18,000 to 32,000 h-1. This pilot-scale research has shown that SNCR and SCR can be integrated to achieve high NO(x) remova l. SNCR provides high temperature reduction of NO(x) followed by furth er removal of NO(x) and minimization of NH(3) slip by a significantly downsized (high-space velocity) SCR.