Pulverized coal burner for furnace and operating method

A pulverized coal burner for a furnace comprising in combination, an elongated fuel tube, a tangential spiral delivery conduit connected to an inlet opening at one end of said fuel tube and adapted to receive finely divided coal free from air and conveyed by a minimum proportion of inert dry steam to insure delivery of said coal to the opposite end of said fuel tube in the absence of air within said tube, a central elongated tube of smaller diameter mounted coaxially within said fuel tube, means at said one end of said fuel tube supporting a corresponding end of said central tube, the opposite ends of said tubes defining therebetween an annular discharge means for said coal and steam mixture with the absence of air and the tangential delivery thereof to said fuel tube causing said mixture to move spirally and axially along said tube in a manner to cause centrifugal force to effect at least partial separation of the coal from the steam and dispose the coal particles in heavier concentration near the wall of said fuel tube while the steam tends to concentrate near said central tube, a circular outwardly flared diffuser on the discharge end of said fuel tube and an outwardly flared circular deflector on the delivery end of said central tube, an annular air inlet port adapted to be mounted in a furnace wall and coaxially surrounding said fuel tube adjacent the discharge end thereof, and means to deliver combustion air under pressure to said inlet port for mixture with the pulverized coal discharged spirally in an outwardly flared pattern, from said annular discharge means, whereby said coal is at least partially separated from said steam when exiting from said annular discharge means and is delivered to the combustion zone immediately adjacent the delivery of combustion air thereto for maximum burning efficiency with minimum smothering effect by the inert steam due to minimum ratio of inert steam to coal, said central tube is provided with steam inlet means adjacent the inlet end of said fuel tube operable to permit a portion of the inert steam of said mixture of steam and coal which is concentrated near said central tube by the centrifugal spiralling of said mixture for passage of said portion of steam through said central tube to the discharge end thereof where the greatest ratio of steam to coal occures as the same is delivered to said combustion zone.