Simultaneous adsorption of SO2-NOx from flue gases in a riser configuration

Simultaneous adsorption of SO2-NOx is a new, promising process in treating industrial flue gases in a short-contact-time dilute phase riser with Na/gamma -Al2O3 sorbent particles of 50-100 mum diameter at 370-430 K. A major part of the sorbent is recycled for maximum utilization of the sorbent capacity before, regeneration. A steady-state model for the riser adsorber is developed by combining independently deter mined rate equations with a 1-D, two-phase hydrodynamic model of the riser. The simulation was validated with the operating data from a pilot-scale installation of 4.2 Nm(3)/s flue-gas capacity and solid fluxes between 1 and 3 kg (.) m(-2 .) s(-1). Pie riser operates in an extremely dilute phase with a solid volume fraction below 7.0 x 10(-4) and a slip velocity that is constant for almost the entire riser length, indicating fully developed flow The experimental observation that an increase in the SO2-NO ratio in the feed gas leads to a higher NO removal efficiency is explained as resulting from an increased concentration of the adsorbed SO2. The SO2 removal efficiency, however, may drop if free adsorption sites are not sufficiently available. Recycling of the sorbent has only a marginal effect on the NO removal, but helps to maximize the SO2 adsorption. For the first time, the simultaneous removal of SO2 above 95% and of NOx above 80% is reported using a dry, regenerable sorbent in a riser reactor.