Method for improved manufacture of cement in long kilns

An apparatus for enhancing the capacity and efficiency of clinker production of a conventional wet or dry long rotary kiln, said kiln comprising a rotating vessel having a fired lower end and an adjacent clinkering zone, an upper kiln gas exit end and an adjacent mineral drying zone, and an intermediate calcining zone along its length and a kiln gas stream flowing serially from the clinkering zone through the intermediate calcining zone and upper mineral drying zones out of the rotary vessel and to a kiln dust collection system and an in-process mineral stream flowing in the opposite direction in the rotary vessel from the mineral drying zone through the calcining zone to the clinkering zone, said apparatus comprising

• means for withdrawing a portion of the kiln gases from the rotating vessel at a point upstream of the drying zone, relative to the flowing kiln gases, to form a kiln gas bypass stream, said means for withdrawing the kiln gas bypass stream comprising a port in the rotary vessel, a bypass inlet tube covering the port and extending from the port into the rotary vessel a distance greater than a depth of the mineral stream to an open area adjacent the center of the rotary vessel to prevent in-process mineral from flowing through said port, a stationary annular plenum in sealing engagement with the rotary vessel and in alignment with said port axially along the length of the rotary vessel and in gas flow communication with said port, means connected in fluid communication with said annular plenum for creating reduced pressure in said annular plenum to withdraw at least a portion of the kiln gas stream out of said rotating vessel through said inlet tube and port and into said annular plenum and means connected for cooling the kiln bypass stream in the annular plenum.

In a conventional wet or dry long rotary kiln comprising a rotating vessel having a fired lower end and adjacent clinkering zone, and upper gas exit end and adjacent mineral drying zone, and an intermediate calcining zone along its length and in operation having a kiln gas stream flowing serially from said clinkering zone through said calcining and mineral drying zone out the gas exit end of the rotary vessel and from there to a kiln dust collection system and an in-process mineral stream flowing in an opposite direction from the drying zone through the calcining zone to the clinkering zone, the improvement which comprises

• a bypass port in the rotary vessel at a point upstream, relative to the serial kiln gas flow, of the mineral drying zone,
• a bypass inlet tube covering the port and in gas flow communication with said port and extending from the port into the rotary vessel a distance greater than a depth of the in-process mineral stream to an open area adjacent the center of the rotary vessel to prevent in-process mineral material from flowing through said port,
• a stationary annular plenum in sealing engagement with the rotary vessel in alignment with said port axially along the length of the rotary vessel, in gas flow communication with said port and having located thereon an ambient air inlet, and
• means connected to said annular plenum for creating reduced pressure in said annular plenum to draw air into said plenum through said ambient air inlet and to withdraw at least a portion of the kiln gas stream out of said rotary vessel through said port and into said annular plenum.

An apparatus for enhancing the capacity and efficiency of clinker production of a conventional wet or dry long rotary kiln, said kiln in operation comprising a rotating vessel having a fired lower end and an adjacent clinkering zone, an upper kiln gas exit end and an adjacent mineral drying zone, and an intermediate mineral calcining zone along its length and a kiln gas stream flowing serially from the clinkering zone through the intermediate calcining zone and upper mineral drying zone of the rotating kiln, and from there to a kiln dust collection system and an in-process mineral stream flowing in the opposite direction from the drying zone through the calcining zone to the clinkering zone, said apparatus comprising

• a solid fuel charging port and a gas bypass port in the rotary vessel, said fuel charging port located at a point along the length of the vessel wherein fuel charged through the port will enter the calcining zone and said bypass port located at a point on the vessel downstream, relative to kiln gas flow, from said fuel charging port;
• separate means each extending from one of the ports into the rotary vessel a distance greater than the depth of the in-process mineral stream to an open area adjacent the center of the rotary vessel for preventing in-process mineral from passing through each of said fuel charging and bypass ports;
• a stationary annular plenum in sealing engagement with the rotary vessel and in alignment with the bypass port axially along the length of the rotary vessel and in gas flow communication with said bypass port;
• an air inlet port on said plenum connected to a source of ambient air,
• means connected to the annular plenum in gas flow communication with the annular plenum for creating reduced pressure in said annular plenum to withdraw both ambient air from said source into said plenum through the air inlet port and at least a portion of the kiln gas stream through the separate means connected to said bypass port from within the rotary vessel and into said annular plenum to form a kiln gas bypass stream;
• and
• means cooperating with the charging port for charging solid fuel into the calcining zone through the other said separate means.

An apparatus for enhancing the capacity and efficiency of clinker production of a conventional wet or dry long rotary kiln, said kiln comprising a rotating vessel having a fired lower end and an adjacent clinkering zone, an upper kiln gas exit end and an adjacent mineral drying zone, and an intermediate calcining zone along its length and a kiln gas stream flowing serially from the clinkering zone through the intermediate calcining zone and upper mineral drying zone of the rotating vessel and from there to a kiln dust collection system and an in-process mineral stream flowing in an opposite direction from the drying zone through the calcining zone to the clinkering zone, said apparatus comprising

• a port in the rotary vessel located axially between the calcining zone and the mineral drying zone;
• a bypass inlet tube attached to the port and extending into the rotary vessel a distance greater than the depth of the in-process mineral stream to an open area adjacent the center of the rotary vessel, wherein the tube is longer than the maximum depth of mineral in the rotary vessel;
• a stationary annular plenum in sealing engagement with the rotary vessel in axial alignment with and in gas flow communication with the port and having an air inlet damper valve connected to a source of ambient air;
• a blower fan in air flow communication with the annular plenum for creating reduced pressure in the annular plenum to withdraw ambient air through the damper valve into the plenum and at least a portion of the kiln gas stream in the rotary vessel through the inlet tube, the port and into the plenum to form a kiln gas bypass stream.