Method of removing nitrogen oxides from an exhaust
AssigneeNippon Kokan Kabushiki Kaisha
InventorsTomoji Iwata, Sanseki Moriguchi, Hiroshi Abe
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Abstract
A method of removing nitrogen oxides from an exhaust which comprises the steps of contacting an exhaust containing nitrogen oxides and ammonia with a reducing catalyst received in a reactor to reduce the nitrogen oxides to nitrogen gas, wherein iron ore catalyst lumps having a particle size of 25 mm or less and forming a catalyst bed in the reactor are used as a reducing catalyst; the iron ore lumps of the catalyst bed are let to fall gravitationally through the reactor continuously or intermittently; and the iron ore catalyst lumps discharged from the reactor are either used as raw material for iron manufacture or fed back to the reactor to be reused as a reducing catalyst after being sieved.
Claims11
In a method of removing nitrogen oxides from an exhaust which comprises contacting ammonia and an exhaust containing nitrogen oxides with a reducing catalyst of iron ore lumps received in a reactor to convert the nitrogen oxides into nitrogen gas,
- the improvement comprising:
- feeding iron ore catalyst lumps with a particle size of 25 mm or less to the reactor in the form of a movable bed so that said iron ore catalyst lumps are partly discharged from the reactor in succession;
- sieving the iron ore catalyst lumps discharged from the reactor by a 2 to 6 mm screen;
- repeatedly feeding back at least a portion of the larger iron ore catalyst lumps not sieved by said screen to the movable bed of reducing catalyst for again passing through the reactor;
- transferring the screenings of smaller iron ore catalyst lumps obtained by passing through the screen to a sintering or pelletizing plant to be converted into lumps having a sufficiently large particle size to be charged in a blast furnace for iron manufacture;
- and
- charging fresh iron ore catalyst lumps having a particle size of 25 mm or less into the reactor to replenish the discharged and transferred portion of said iron ore catalyst lumps.
In a method of removing nitrogen oxides from an exhaust which comprises contacting ammonia and an exhaust containing nitrogen oxides with a reducing catalyst of iron ore lumps received in a reactor to convert the nitrogen oxides into nitrogen gas,
- the improvement comprising:
- feeding iron ore catalyst lumps with a particle size of 25 mm or less to the reactor in the form of a movable bed so that said iron ore catalyst lumps are partly discharged from the reactor in succession;
- sieving the iron ore catalyst lumps discharged from the reactor by a 2 to 6 mm screen;
- feeding at least a portion of the larger iron ore catalyst lumps not sieved by said screen intact in a blast furnace;
- transferring the screenings of smaller iron ore catalyst lumps obtained by passing through the screen to a sintering or pelletizing plant to be converted into lumps having a sufficiently large particle size to be charged in a blast furnace for iron manufacture;
- and
- charging fresh iron ore catalyst lumps having a particle size of 25 mm or less into the reactor to replenish the discharged and transferred portion of said iron ore catalyst lumps.
Dependencies are inferred from the claim text.