Gas conditioning apparatus

Claim 1

In a sulfur trioxide gas conditioning apparatus wherein an induced flow of heated air is directed via a flowpath extending between an inlet and outlet and from such outlet into a flue for conditioning of flue gases containing flyash by injecting a controlled amount of sulfur trioxide gaseous mixture to vary the resistivity of such flyash, such induced air flow, as it flows along said flowpath, passes through conversion means to produce an air and sulfur trioxide mixture for use in the conditioning of such flue gases and which conditioning apparatus includes a purge means for purging, on demand, at least a downstream portion thereof of sulfur trioxide gaseous mixture therefrom, the improvement in said purge means comprising: a purge air flow induction means; a first purge air conduit means for directing purge air flow into said flowpath upstream from said conversion means; second purge air flow conduit means for directing purge air flow into said flowpath downstream from said conversion means; selectively operable valve means for selectively directing purge air flow from said purge air flow induction means through said first and said second purge air flow conduit means and for selectively isolating said purge air flow induction means from said flowpath; and said selectively operable valve means includes a respectively operable valve in each of said first and second purge air flow conduit means.