Abstract: A selective catalytic reduction process (SCR) for reducing the oxides of nitrogen (NO.sub.x) content of a furnace flue gas. The process comprises splitting the flue gas into two streams, treating one of the streams with an SCR process with the same amount of NH.sub.3 as NO.sub.x, and then recombining the streams. By treating only a portion of the flue gas using an NH.sub.3 /NO.sub.x ratio of unity, the amount of catalyst required is reduced while the residual NO.sub.x and NH.sub.3 contents of the recombined streams is controlled to desired levels.

Abstract: A process for the treatment of a gas stream by passing the gas stream parallel to the outer screen of a contactor bed wherein the detrimental effects caused by the accumulation of fine particles on the screen is counteracted by the periodic or continuous admixture of additional fluidizable particles into the gas stream. The invention may be adapted to many processes in which a particle-containing gas stream is treated using a parallel flow vapor-solids contacting apparatus including the adsorption of specific chemical compounds, the oxidation of sulfur-containing compounds or the reduction of nitrogen oxides.