Abstract: Hot flue gas containing sulfur oxides is treated in a dry injection desulfurization process by injecting a dry particulate soda ash sorbent into the SO.sub.2 -contaminated gas stream, which must contain 0.5-10 wt % water and be at a temperature of 100.degree.-175.degree. C., and collecting the sorbent in a solids collection device like a baghouse filter. The dry soda ash sorbent is a porous sodium carbonate, derived from calcination of a NaHCO.sub.3 -containing compound, and must have a minimum surface area of at least 2 m.sup.2 /g and less than 10 wt % residual bicarbonate. In this process, at least 40% of the sorbent's sodium content is utilized in the desulfurization reaction, at a normalized stoichiometric ratio=1.

Abstract: YUtilization of a soda-type dry sorbent in a dry injection flue gas desulfurization process is increased, without sacrifice in the SO.sub.2 removal efficiency, by reinjecting a portion of the sorbent collected in the baghouse filter back into the hot flue gas stream along with fresh sorbent; the recycled sorbent is optionally cooled below the bag filter temperature prior to its reinjection.