Bk. Gullett et al., NO(X) REMOVAL WITH COMBINED SELECTIVE CATALYTIC REDUCTION AND SELECTIVE NONCATALYTIC REDUCTION - PILOT-SCALE TEST-RESULTS, Journal of the Air & Waste Management Association [1995], 44(10), 1994, pp. 1188-1194
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.