Method of burning granular or pulverulent raw material and kiln plant therefor

Claim 1

A method of heat treating granular or pulverulent raw material by means of a suspension heat exchanger connected to the material inlet end portion of a rotary kiln having a burner pipe extending into the material outlet end portion, said heat exchanger including at least first and second multi-stage string preheating units operating in parallel, each of said units having at least one cyclone preheater stage defining a heat exchange zone in which the granular or pulverulent raw material is brought into heat exchange relationship with hot gases and a lowermost calcination stage for preheating and at least partially calcining the raw material, means to supply raw material to each of said multi-stage string preheater units, means for directing the preheated, at least partially calcined raw material to said material inlet end portion of said rotary kiln for sintering, and cooling means communicating with said rotary kiln defining a heat exchange zone in which the sintered material is brought into heat exchange relationship with cooling air comprising: (a) directing raw material to said multi-stage string preheating units for preheating and at least partially calcining the material; (b) feeding preheated, at least partially calcined material from said heat exchanger into said rotary kiln; (c) sintering the preheated, at least partially calcined material in said kiln; (d) directing the sintered material from said kiln into said communicating cooling means; (e) directing cooling air into said cooling means so as to contact said sintered material to effect a heat exchange between the sintered material and the cooling air thereby at least partially cooling the sintered material and at least partially heating the cooling air; (f) dividing the heated cooling air exiting the cooling means and directing a first portion of said heated cooling air to at least one of said calcination stages of at least a first of said multi-stage preheating units of said heat exchanger and directing a second portion thereof to said kiln in excess of that required to support combustion of fuel in the kiln for the sintering process thereby creating an intensified material cooling zone between the mouth of said burner pipe and the material exit end portion of said rotary kiln; (g) directing hot kiln exit gases to said calcination stage of at least a second of said multi-stage string preheating units; and (h) directing fuel to at least one of said calcination stages of said multi-stage string preheating units to support combustion with at least partially heated cooling air and thereby provide supplementary heating and at least partial calcining of said preheated material.

Claim 2

A method of heat treating granular or pulverulent raw material by means of a suspension heat exchanger connected to the material inlet end portion of a rotary kiln having a burner pipe extending into the material outlet end portion, said heat exchanger including at least first and second multi-stage string preheating units operating in parallel, each of said units having at least one cyclone preheater stage defining a heat exchange zone in which the granular or pulverulent raw material is brought into heat exchange relationship with hot gases and a lowermost calcination stage for preheating and at least partially calcining the raw material, means to supply raw material to each of said multi-stage string preheater units, means for directing the preheated, at least partially calcined raw material to said material inlet end portion of said rotary kiln for sintering, and cooling means communicating with said rotary kiln defining a heat exchange zone in which the sintered material is brought into heat exchange relationship with cooling air comprising: (a) directing raw material to said multi-stage string preheating units for preheating and at least partially calcining the material; (b) feeding preheated, at least partially calcined material from said heat exchanger into said rotary kiln; (c) sintering the preheated, at least partially calcined material in said kiln; (d) directing the sintered material from said kiln into said communicating cooling means; (e) directing cooling air into said cooling means so as to contact said sintered material to effect a heat exchange between the sintered material and the cooling air thereby at least partially cooling the sintered material and at least partially heating the cooling air; (f) dividing the heated cooling air exiting the cooling means and directing a first portion of said heated cooling air to at least one of said calcination stages of at least a first of said multi-stage preheating units of said heat exchanger and directing a second portion thereof to said kiln in excess of that required to support combustion of fuel in the kiln for the sintering process thereby creating an intensified material cooling zone between the mouth of said burner pipe and the material exit end portion of said rotary kiln; (g) directing hot kiln exit gases to said calcination stage of at least a second of said multi-stage string preheating units; and (h) directing fuel to at least one of said calcination stages of said multi-stage string preheating units to support combustion with at least partially heated cooling air and thereby provide supplementary heating and at least partial calcining of said preheated material.

Claim 18

A method of heat treating granular or pulverulent raw material in the form of cement raw meal by means of a suspension heat exchanger connected to the material inlet end portion of a rotary kiln having a burner pipe extending into the material outlet end portion, said heat exchanger including at least two multi-stage cyclone string preheater units operating in parallel, each of said units having at least an uppermost cyclone preheater stage defining a heat exchanger zone in which the granular or pulverulent raw material is brought into heat exchange relationship with hot gases and a lowermost calcination stage for preheating and at least partially calcining the raw material, means to supply raw material to each of said multi-stage string preheater units, means for directing the preheated, at least partially calcined raw material to the material inlet end portion of said rotary kiln for sintering, and cooling means positioned and adapted to receive sintered material from said rotary kiln and defining a heat exchange zone in which the sintered material is brought into heat exchange relationship with cooling air comprising: (a) directing the raw material to said multi-stage preheater units for preheating and at least partially calcining the material; (b) feeding preheated at least partially calcined material from said lowermost cyclone preheater stage of said first string preheater to said calcination stage of said second string preheater; (c) further calcining said at least partially calcined material in said calcination stage of said second string preheater; (d) feeding preheated material from the penultimate cyclone preheater stage of said second string preheater to said calcination stage of said second string preheater; (e) feeding preheated, at least partially calcined material from said calcination stage of said second string preheater to the lowermost cyclone preheater stage of said second string preheater; (f) feeding preheated, at least partially calcined material from said lowermost cyclone preheater stage of said second string preheater of said heat exchanger to said material inlet end portion of said rotary kiln; (g) burning the preheated, at least partially calcined material in said rotary kiln; (h) directing the burnt material from said rotary kiln into said material cooling means communicating with said rotary kiln and adapted to receive material burnt in said rotary kiln for cooling therein; (i) directing cooling air into said cooling means countercurrent to the flow of material therein and in a manner to effect a heat exchange between said burnt material and said cooling air thereby at least partially cooling said burnt material and at least partially heating said cooling air; (j) dividing the heated cooling air exiting the material cooling means and directing a first portion of said heated cooling air to said calcination stage associated with said second string preheater and the remaining portion thereof to said rotary kiln to support combustion of fuel therein; (k) directing a second portion of said heated cooling air to said calcination stage of said second multi-stage string preheater; (l) directing hot kiln exit gases to the lowermost calcination stage associated with said first string preheater; (m) directing fuel to said calcination stage of at least said second string preheater and burning said fuel at least in said calcination stage while supporting combustion in said calcination stages of said first and second string preheaters with heated cooling air from said material cooling means and from said kiln; and (n) adjustably controlling the flow of heated cooling air through each of said string preheaters so as to divide the heated cooling air passing therethrough such that the heated cooling air passing through said rotary kiln is in excess of that required to support combustion of fuel for the burning process in the kiln thereby creating an intensified material cooling zone between the mouth of said burner pipe and the material outlet end portion of said rotary kiln.

Claim 19

A method of heat treating granular or pulverulent raw material in the form of cement raw meal by means of a suspension heat exchanger connected to the material inlet end portion of a rotary kiln having a burner pipe extending into the material outlet end portion, said heat exchanger including at least two multi-stage cyclone string preheater units operating in parallel, each of said units having at least an uppermost cyclone preheater stage defining a heat exchanger zone in which the granular or pulverulent raw material is brought into heat exchange relationship with hot gases and a lowermost calcination stage for preheating and at least partially calcining the raw material, means to supply raw material to each of said multi-stage string preheater units, means for directing the preheated, at least partially calcined raw material to the material inlet end portion of said rotary kiln for sintering, and cooling means positioned and adapted to receive sintered material from said rotary kiln and defining a heat exchange zone in which the sintered material is brought into heat exchange relationship with cooling air comprising: (a) directing the raw material to said multi-stage preheater units for preheating and at least partially calcining the material; (b) feeding preheated at least partially calcined material from said lowermost cyclone preheater stage of said first string preheater to said calcination stage of said second string preheater; (c) further calcining said at least partially calcined material in said calcination stage of said second string preheater; (d) feeding preheated material from the penultimate cyclone preheater stage of said second string preheater to said calcination stage of said second string preheater; (e) feeding preheated, at least partially calcined material from said calcination stage of said second string preheater to the lowermost cyclone preheater stage of said second string preheater; (f) feeding preheated, at least partially calcined material from said lowermost cyclone preheater stage of said second string preheater of said heat exchanger to said material inlet end portion of said rotary kiln; (g) burning the preheated, at least partially calcined material in said rotary kiln; (h) directing the burnt material from said rotary kiln into said material cooling means communicating with said rotary kiln and adapted to receive material burnt in said rotary kiln for cooling therein; (i) directing cooling air into said cooling means countercurrent to the flow of material therein and in a manner to effect a heat exchange between said burnt material and said cooling air thereby at least partially cooling said burnt material and at least partially heating said cooling air; (j) dividing the heated cooling air exiting the material cooling means and directing a first portion of said heated cooling air to said calcination stage associated with said second string preheater and the remaining portion thereof to said rotary kiln to support combustion of fuel therein; (k) directing a second portion of said heated cooling air to said calcination stage of said second multi-stage string preheater; (l) directing hot kiln exit gases to the lowermost calcination stage associated with said first string preheater; (m) directing fuel to said calcination stage of at least said second string preheater and burning said fuel at least in said calcination stage while supporting combustion in said calcination stages of said first and second string preheaters with heated cooling air from said material cooling means and from said kiln; and (n) adjustably controlling the flow of heated cooling air through each of said string preheaters so as to divide the heated cooling air passing therethrough such that the heated cooling air passing through said rotary kiln is in excess of that required to support combustion of fuel for the burning process in the kiln thereby creating an intensified material cooling zone between the mouth of said burner pipe and the material outlet end portion of said rotary kiln.

Claim 20

A method of heat treating granular or pulverulent raw material in the form of cement raw meal by means of a suspension heat exchanger connected to the material inlet end portion of a rotary kiln having a burner pipe extending into the material outlet end portion, said heat exchanger including at least three multi-stage cyclone string preheater units operating in parallel, each of said units having at least an uppermost cyclone preheater stage defining a heat exchanger zone in which the granular or pulverulent raw material is brought into heat exchange relationship with hot gases and a lowermost calcination stage for preheating and at least partially calcining the raw material, means to supply raw material to each of said multi-stage string preheater units, means for directing the preheated, at least partially calcined raw material to the material inlet end portion of said rotary kiln for sintering, and cooling means positioned and adapted to receive sintered material from said rotary kiln and defining a heat exchange zone in which the sintered material is brought into heat exchange relationship with cooling air comprising: a. directing the raw meal to said heat exchanger to effect a preheating and at least a partial calcination of the material; b. feeding peheated, at least partially calcined raw meal from the first two string preheaters to a rotary kiln; c. feeding preheated, at least partially calcined raw meal from one cyclone preheater of the last preheater stage of said third string preheater to the calcining stage associated with said second string preheater; d. feeding preheated, at least partially calcined raw meal from the other preheater cyclone of said third string preheater to the calcining stage associated with said first string preheater; e. burning the preheated, at least partially calcined raw meal in said rotary kiln; f. directing the burnt material from the kiln into cooling means communicating with the kiln; g. directing cooling air into said cooling means in a manner to effect a heat exchange between the burnt material and the cooling air; h. dividing the heated cooling air leaving the cooling means and directing a portion of said heated cooling air to the calcining stage associated with each of said first two string preheaters and the remaining portion of heated cooling air to said rotary kiln to support the combustion of fuel therein, the remaining portion being in excess of that required to support combustion of fuel for the burning process in the kiln and thereby creating an intensive material cooling zone between the mouth of said burner pipe and the material outlet end portion of said rotary kiln; i. directing the hot kiln exit gases to the lowermost calcining chamber associated with said third string preheater; j. directing fuel to each calcining stage of said string preheaters and burning said fuel in said calcining stages while supporting combustion in first and second chambers with preheated cooling air from said cooling means and in the third chamber with excess heated cooling air passing through said kiln; and k. controlling the flow of gases through each of said string preheaters and maintaining the flow of gases therethrough at levels capable of maintaining the deposits of alkalis therein at predetermined desired levels.

Claim 21

A method of heat treating granular or pulverulent raw material in the form of cement raw meal by means of a suspension heat exchanger connected to the material inlet end portion of a rotary kiln having a burner pipe extending into the material outlet end portion, said heat exchanger including at least three multi-stage cyclone string preheater units operating in parallel, each of said units having at least an uppermost cyclone preheater stage defining a heat exchanger zone in which the granular or pulverulent raw material is brought into heat exchange relationship with hot gases and a lowermost calcination stage for preheating and at least partially calcining the raw material, means to supply raw material to each of said multi-stage string preheater units, means for directing the preheated, at least partially calcined raw material to the material inlet end portion of said rotary kiln for sintering, and cooling means positioned and adapted to receive sintered material from said rotary kiln and defining a heat exchange zone in which the sintered material is brought into heat exchange relationship with cooling air comprising: a. directing the raw meal to said heat exchanger to effect a preheating and at least a partial calcination of the material; b. feeding peheated, at least partially calcined raw meal from the first two string preheaters to a rotary kiln; c. feeding preheated, at least partially calcined raw meal from one cyclone preheater of the last preheater stage of said third string preheater to the calcining stage associated with said second string preheater; d. feeding preheated, at least partially calcined raw meal from the other preheater cyclone of said third string preheater to the calcining stage associated with said first string preheater; e. burning the preheated, at least partially calcined raw meal in said rotary kiln; f. directing the burnt material from the kiln into cooling means communicating with the kiln; g. directing cooling air into said cooling means in a manner to effect a heat exchange between the burnt material and the cooling air; h. dividing the heated cooling air leaving the cooling means and directing a portion of said heated cooling air to the calcining stage associated with each of said first two string preheaters and the remaining portion of heated cooling air to said rotary kiln to support the combustion of fuel therein, the remaining portion being in excess of that required to support combustion of fuel for the burning process in the kiln and thereby creating an intensive material cooling zone between the mouth of said burner pipe and the material outlet end portion of said rotary kiln; i. directing the hot kiln exit gases to the lowermost calcining chamber associated with said third string preheater; j. directing fuel to each calcining stage of said string preheaters and burning said fuel in said calcining stages while supporting combustion in first and second chambers with preheated cooling air from said cooling means and in the third chamber with excess heated cooling air passing through said kiln; and k. controlling the flow of gases through each of said string preheaters and maintaining the flow of gases therethrough at levels capable of maintaining the deposits of alkalis therein at predetermined desired levels.

Claim 22

A method of heat treating granular or pulverulent raw material in the form of cement raw meal by means of a suspension heat exchanger connected to the material inlet end portion of a rotary kiln having a burner pipe extending into the material outlet end portion, said heat exchanger including at least four multi-stage cyclone string preheater units operating in parallel, each of said units having at least an uppermost cyclone preheater stage defining a heat exchanger zone in which the granular or pulverulent raw material is brought into heat exchange relationship with hot gases and a lowermost calcination stage for preheating and at least partially calcining the raw material, means to supply raw material to each of said multi-stage string preheater units, means for directing the preheated, at least partially calcined raw material to the material inlet end portion of said rotary kiln for sintering, and cooling means positioned and adapted to receive sintered material from said rotary kiln and defining a heat exchange zone in which the sintered material is brought into heat exchange relationship with cooling air comprising: a. directing the raw meal to said heat exchanger to effect a preheating and at least a partial calcination of the material; b. feeding preheated, at least partially calcined raw meal from each preheater string to a common conduit; c. feeding the preheated meal through the common conduit into a rotary kiln; d. burning the preheated, at least partially calcined raw meal in said rotary kiln; e. directing the burnt material from the rotary kiln into a cooler communicating with the kiln; f. directing cooling air into said cooler in a manner to effect a heat exchange between the burnt material and the cooling air; g. dividing the heated cooling air leaving the cooler and directing a portion of said heated cooling air into two of said calcination stages associated respectively with a first two of said preheater strings, and directing the remaining portion of said heated cooling air to said rotary kiln in excess of that required to support combustion of fuel in the kiln for the burning process, thereby creating an intensive material cooling zone between the mouth of said burner pipe and the material outlet portion of said rotary kiln; h. directing hot kiln exit gases to the calcining stages of said remaining two string preheaters; i. directing fuel to each calcining stage of said string preheaters and burning said fuel in said calcining stages while supporting combustion in two of said stages with preheated cooling air from said cooler and supporting combustion in the remaining two stages with excess heated cooling air passing through said kiln; and j. controlling the flow of gases through each string of said last heat exchanger units so as to control the division of waste cooling air between said rotary kiln and said string preheaters and maintaining the flow of gases therethrough at levels capable of maintaining alkali deposits therein at predetermined desired minimum levels.

Claim 23

A method of heat treating granular or pulverulent raw material in the form of cement raw meal by means of a suspension heat exchanger connected to the material inlet end portion of a rotary kiln having a burner pipe extending into the material outlet end portion, said heat exchanger including at least four multi-stage cyclone string preheater units operating in parallel, each of said units having at least an uppermost cyclone preheater stage defining a heat exchanger zone in which the granular or pulverulent raw material is brought into heat exchange relationship with hot gases and a lowermost calcination stage for preheating and at least partially calcining the raw material, means to supply raw material to each of said multi-stage string preheater units, means for directing the preheated, at least partially calcined raw material to the material inlet end portion of said rotary kiln for sintering, and cooling means positioned and adapted to receive sintered material from said rotary kiln and defining a heat exchange zone in which the sintered material is brought into heat exchange relationship with cooling air comprising: a. directing the raw meal to said heat exchanger to effect a preheating and at least a partial calcination of the material; b. feeding preheated, at least partially calcined raw meal from each preheater string to a common conduit; c. feeding the preheated meal through the common conduit into a rotary kiln; d. burning the preheated, at least partially calcined raw meal in said rotary kiln; e. directing the burnt material from the rotary kiln into a cooler communicating with the kiln; f. directing cooling air into said cooler in a manner to effect a heat exchange between the burnt material and the cooling air; g. dividing the heated cooling air leaving the cooler and directing a portion of said heated cooling air into two of said calcination stages associated respectively with a first two of said preheater strings, and directing the remaining portion of said heated cooling air to said rotary kiln in excess of that required to support combustion of fuel in the kiln for the burning process, thereby creating an intensive material cooling zone between the mouth of said burner pipe and the material outlet portion of said rotary kiln; h. directing hot kiln exit gases to the calcining stages of said remaining two string preheaters; i. directing fuel to each calcining stage of said string preheaters and burning said fuel in said calcining stages while supporting combustion in two of said stages with preheated cooling air from said cooler and supporting combustion in the remaining two stages with excess heated cooling air passing through said kiln; and j. controlling the flow of gases through each string of said last heat exchanger units so as to control the division of waste cooling air between said rotary kiln and said string preheaters and maintaining the flow of gases therethrough at levels capable of maintaining alkali deposits therein at predetermined desired minimum levels.