Method of burning pulverous raw material and rotary kiln plant therefor

A method of heat treating preheated pulverous raw material consisting entirely of, or at least containing a portion of lime to produce at least a partial calcination in a generally upright elongated calcination chamber having an upper portion and a lower portion, first feeding means communicating with said lower portion and extending downward and inward for feeding raw material into said chamber, an inclined annular bottom wall tapering downward and inward and having inner surface portions provided with a plurality of inwardly extending grooves, second feeding means extending upward and inward for feeding fuel into the lower portion of said calcination chamber comprising:

• (a) feeding preheated raw material through said first feeding means into the lower portion of said calcination chamber such that at least a portion of the raw material slides down the bottom wall along at least one of said grooves;
• (b) separately feeding a fuel capable of carrying out at least a partial calcination of the material generally upward through said second feeding means into the lower portion of said calcination chamber such that said raw material and said fuel enter the lower portion of said calcination chamber in separate and intesecting paths resulting in substantially immediate and intimate mixing;
• (c) directing a stream of oxygen containing gas upward and generally centrally through said calcination chamber to intersect the path of said material and fuel mixture so as to form eddys as said upward directing gas passes through said calcination chamber to cause said fuel to burn and the individual particles of the raw material to be at least partially calcined substantially isothermally;
• (d) passing the at least partially calcined material particles and exit gases out of the chamber in the central gas stream;
• and
• (e) separating the particles from said central gas stream.

A method of heat treating preheated, pulverous raw material consisting entirely of, or at least containing a portion of lime to produce at least a partial calcination in a generally elongated calcination chamber having an upper portion and a lower portion, said lower portion comprising first means for discharging raw material thereinto and further comprising an inclined annular bottom wall which tapers downward and inward, inner surface portions of said bottom wall defining an alternating series of generally radially extending crests and valleys, said bottom wall being provided with means for dividing the flow of raw material discharged thereon, and second means extending upward and inward for feeding fuel into bottom portions of at least one of the valleys in the lower portion of said calcination chamber and said chamber oriented so that its central axis is generally upright comprising:

• (a) discharging preheated raw material into the lower portion of the calcination chamber toward the central axis and down the bottom wall along at least one valley of the inclined annular bottom wall of the lower portion of the calcination chamber such that the raw material flow is divided by said baffle means and distributed generally circumferentially about the central axis of the chamber;
• (b) separately feeding a fuel which is at least one of a combustible gas and a fuel capable of producing a combustible gas upon contacting the preheated raw material and capable of carrying out at least a partial calcination of said raw material, the feeding of said fuel being in a generally upward direction through said second feeding means through the bottom wall of the calcination chamber toward the central axis at a location adjacent to, and radially inward of, the location of discharge of raw material such that said raw material and said fuel enter the lower portion of said calcination chamber in separate and intersecting paths resulting in substantially immediate and intimate mixing;
• (c) directing a stream of oxygen containing gas substantially centrally upward through the calcination chamber to intersect the path to said material and fuel mixture so as to form eddies as said upward directed gas passes through said calcination chamber to cause said fuel to burn and the individual particles of the raw material to be at least partially calcined substantially isothermally;
• (d) directing the at least partially calcined material particles and exit gases out of the chamber in the central gas stream;
• and
• (e) separating the particles from said central gas stream.

A method of heat treating preheated, pulverous raw material consisting entirely of, or at least containing a portion of lime to produce at least a partial calcination in a generally elongated calcination chamber having an upper portion and a lower portion, said upper portion having an inclined annular upper wall which tapers upward and inward, said lower portion communicating with a first inclined conduit for feeding raw material thereinto and having an inclined annular bottom wall which tapers downward and inward and defines a generally central opening, inner surface portions of said bottom wall defining an alternating sequence of grooves having peaks and valleys extending generally tangentially of the central opening, baffle means for dividing the flow of raw material discharged into the chamber, second conduit means extending upward and inward for feeding fuel into bottom portions of at least one of said valleys at a location adjacent to and radially inward of the location of discharge of said first conduit and said chamber oriented so that its central axis is generally upright comprising:

• (a) discharging preheated raw material into the lower portion of the calcination chamber toward the central axis and down the bottom wall along at least one valley of the inclined annular bottom wall of the lower portion of the calcination chamber such that the raw material flow is divided by said baffle means and thereby distributed generally circumferentially about the central opening of the bottom wall;
• (b) separately feeding a fuel which is at least one of a combustible gas and a fuel capable of producing a combustible gas upon contacting the preheated raw material and capable of carrying out at least a partial calcination of said raw material, the feeding of said fuel being in a generally upward direction through said second feeding means through the bottom wall of the calcination chamber toward the central axis into bottom portions of at least one of said valleys such that said raw material and said fuel enter the lower portion of said calcination chamber in separate and intersecting paths resulting in substantially immediate and intimate mixing;
• (c) directing a stream of oxygen containing gas substantially centrally upward through the calcination chamber to intersect the path of said material and fuel mixture so as to form eddies as said upward directed gas passes through said calcination chamber to cause said fuel to burn and the individual particles of the raw material to be at least partially calcined substantially isothermally;
• (d) directing the at least partially calcined material particles and exit gases out of the chamber in the central gas stream;
• and
• (e) separating the particles from said central gas stream.

A calcination plant for heat treating a preheated, pulverous raw material consisting entirely of, or at least containing a portion of lime to produce at least a partial calcination thereof which comprises a substantially upright generally tubular calcination chamber including an upper portion having an upper wall portion defining a generally central outlet opening, a lower portion having an inclined annular bottom wall which tapers downward and inward and defines a generally central inlet opening, a substantially central inlet means in said lower portion, a particle/gas separator, duct means communicating said substantially central outlet portion with said particle/gas separator, duct means for introducing raw material downward and inward into the lower portion of said chamber, separate duct means for introducing fuel upward and inward through said bottom wall into said calcination chamber such that said raw material and said fuel enter the lower portion of said calcination chamber in separate and intersecting paths resulting in substantially immediate and intimate mixing, means for directing a flow of oxygen containing gas through said substantially central inlet opening upward and generally centrally through said calcination chamber to intersect the path of said material and fuel mixture so as to form eddys as said upward directed gas passes through said calcination chamber to cause said fuel to burn and the individual particles of the raw material to be at least partially calcined substantially isothermally prior to directing said central gas stream to said particle/gas separator means for separating the at least partially calcined material particles from said central gas stream.

A rotary kiln plant for preheating, at least partially calcining and finally burning pulverous raw material consisting entirely of or at least containing a portion of lime which comprises a cyclone string preheater including at least a lowermost cyclone stage to preheat pulverous raw material, a rotary kiln having a material inlet end portion and a material discharge end portion, a calcination plant comprising a generally upright substantially tubular calcination chamber having an upper portion and a lower portion, a bottom wall defining a substantially central inlet portion, an upper wall, duct means for feeding raw material downward and inward into the lower portion of said calcination chamber, separate duct means for introducing fuel upward and inward through said bottom wall into said calcination chamber such that said raw material and said fuel enter the lower portion of said calcination chamber in separate and intersecting paths resulting in substantially immediate and intimate mixing, means for directing a flow of oxygen containing gas through said substantially central inlet means upward and generally centrally through said calcination chamber to intersect the path of said material and fuel mixture so as to form eddies as said upward directed gas passes through said calcination chamber to cause said fuel to burn and the individual particles of the raw material to be at least partially calcined, a substantially central outlet portion in said upper wall of said calcination chamber, means to direct said mixture into said lowermost cyclone stage of said string preheater for separating the at least partially calcined material particles from said central gas stream, and means to feed said preheated material particles from said lowermost stage of said cyclone preheater to the material inlet end portion of said rotary kiln.