CA1124513A - Process for calcining mineral raw materials in a uniflow regenerative shaft furnace - Google Patents
Process for calcining mineral raw materials in a uniflow regenerative shaft furnaceInfo
- Publication number
- CA1124513A CA1124513A CA335,698A CA335698A CA1124513A CA 1124513 A CA1124513 A CA 1124513A CA 335698 A CA335698 A CA 335698A CA 1124513 A CA1124513 A CA 1124513A
- Authority
- CA
- Canada
- Prior art keywords
- furnace
- cooling
- cooling air
- shaft
- preheated
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
- F27B1/00—Shaft or like vertical or substantially vertical furnaces
- F27B1/005—Shaft or like vertical or substantially vertical furnaces wherein no smelting of the charge occurs, e.g. calcining or sintering furnaces
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
- F27B1/00—Shaft or like vertical or substantially vertical furnaces
- F27B1/10—Details, accessories, or equipment peculiar to furnaces of these types
- F27B1/24—Cooling arrangements
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
- F27D17/00—Arrangements for using waste heat; Arrangements for using, or disposing of, waste gases
- F27D17/004—Systems for reclaiming waste heat
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Vertical, Hearth, Or Arc Furnaces (AREA)
- Furnace Details (AREA)
- Feeding, Discharge, Calcimining, Fusing, And Gas-Generation Devices (AREA)
- Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)
- Devices And Processes Conducted In The Presence Of Fluids And Solid Particles (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
.
`
A process for calcining mineral raw materials is performed in a two-shaft furnace wherein each of the shafts are alternately used as the calcining shaft and as the counterflow shaft. Fuel is supplied in the calcining shaft by means of burners at the end of a preheating zone and the mineral raw material is calcined in a calcining zone. Generated exhaust gases flow upwardly into the counter-flow shaft, heat up the raw material in the shaft and leave through an exhaust. The calcined raw material is passed through an after-deacidification zone and, subsequently, through a cooling zone in which it is cooled by means of cooling air which is blown in from below. After removal of dust, the heated cooling air is either entirely or partially conveyed either directly into a raw material preheater or it is utilized in a recuperator for heating combustion air.
.
`
A process for calcining mineral raw materials is performed in a two-shaft furnace wherein each of the shafts are alternately used as the calcining shaft and as the counterflow shaft. Fuel is supplied in the calcining shaft by means of burners at the end of a preheating zone and the mineral raw material is calcined in a calcining zone. Generated exhaust gases flow upwardly into the counter-flow shaft, heat up the raw material in the shaft and leave through an exhaust. The calcined raw material is passed through an after-deacidification zone and, subsequently, through a cooling zone in which it is cooled by means of cooling air which is blown in from below. After removal of dust, the heated cooling air is either entirely or partially conveyed either directly into a raw material preheater or it is utilized in a recuperator for heating combustion air.
Description
~29~
BACKGROUND OF THE INVENTION
.
The invention relates generally to a process for , calcining raw materials, such as limestone, dolomite or maynesite, in a uniflow regenerative shaft furnace having at least two shafts, wherein simultaneous cooling of caLcined lime in the cooling zones of`the shafts i5 performed.
A regenerative approach for strongly endothermic processes such as for example, the calcining of limestone, known from German AT-PS 211,214, has frequently been used~
for the construction of uniflow/counterflow shaft furnaces having two or three shafts and i has also frequently been described in the literature, among others, by E. SchieIe and L.W. Berens in the book "Xalk" (lime) pages 147-151, published by Verlay Stahl-Eisen, D~sseldorf (W. Germany).
The exclusively regenerative utilization of the heat carrier in this calclning process has been very successful because in the preheating zone of the shafts, not only the material to be calcined, but also the combustion air are preheated. The regenerative preheatina of the combustion air constitutes the thermo-technological feature of such a furnace.
It would seem difficult to practlcall~i improve this calclning process particularly with respect to heat -technology involved.
However, the process has been found not to meet all o~ the requirements with respect to its operational parameters.
It is, therefore, the task of the present invention to provide an improvement in the aforementioned calcining process in this regard.
.' ' ~
3 ~:
SU~'LM~RY OF THE INVENTION
, In accordance with the basic principles of the invention, cooling air which is heated in the cooling zone of the fuxnace by the calcined raw material is removed at least partially fro~ the furnace at the end of the cooling zone and its heat content is recuperatively utlli2ed , outside of the furnace shafts for preheating the raw materials which are supplied to the furnace andjor for preheating the combustion air to be supplied at the upper end of the pre-heating zone.
The various features of novelty which characterize ~ :
: . the invention are pointed out with particularity in the claims : . annexed to and forming a part of thls disclosure. For a better : understanding of the invention, its operating advantages and .
~ specific objects attained by its use, reference should be had .
to the accompanying drawings and descriptive matter in which there are illustrated and described preferred e~bodiments o the invention.
D CRIPTION OF THE DR_WINGS
' In the Drawings:
Fig. 1 is a schematic illustration of a two.shaft . urnace with a square or rectang~lar cross-section;
' . - 3 -~ z~5~3 Fig. 2 is a pressure model for the cooling zone of the counterflow shaf~ of a regenerative shaft furnacer wherein there occurs removal of an amount of cooling air at the outer side wall;
Fig. 3 is a pressure model for the cooling zone of the uniflow shaft of a~ reyenerative shaft furnace, wherein there occurs removal of an amount of coollng air at the inner side wall; and Fig. 4 is a schematic illustration of a two-shaft furnace with circular shaft cross-section.
.
; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Illustrated in Fig. 1 is a two-shaft furnace .
operate~ in uniflow wherein the shaft 1 operates as the calcining shaft and wherein the shaft 2 operates as the counterflow shaft. The shafts 1, 2 each define a preheating zone V, a calcining zone B, an after-deacidification zone N
and a cooling zone K. Combustion air and the cooling air are supplied by means of a blower 3 or 4, e.g. a rotary compressor. Fuel enters the calcining shaft 1 in Fig. 1 thxough burners 5 approximately at the beginn;ng of the calcining zone B~ Flue gases symbolically illustrated by an arrow 6 and enriched by CO2 which emerge from the ~L~.Z4~ ~
limestone initially flow downwardly parallel with the charge, then further in the counterflow shaft 2 and~ in the 'shaft 2, upwardly opposite the charging'movement to the exhaust 7.
The cooling air 10 which is supplied through a line 8 to the two shafts 1, 2 over sliding tables 9 serving to dlscharge the calcined material, flows upwardly in.the cooli.ng zone K, ancl after preheating through the calcined lime, it flows laterally outwardly through exhaust ducts 11 through a dust-collecting device, e.g., a cyclone, and through a line 13 into a limestone preheater 14 or through an alr recuperator 15 to the furnace exterior or to a dust-collecting system (not shown).
The combustion air delivered by the'blower 4 th~rough a line 16 enters the shaft 1 at the top either dlrectly through a line 17 or through the air regulator 15.
The limestone preheated and predried in the charging bucket or .
ladle 18 is, as required, supplied to one or the other of the shafts 1 or 2~ A change is made after the termination of the calcining procedure in the shaft 1 and the shaft 2 becomes the calcining shaft and the shaft 1 become5 the counterflow shat.
' Figs. 2 and 3 graphically depict flow conditions in the after-deacidification zone N and in the cooling zone K f the count~rflow sha-t 2 and the calcining shaft 1.
The results determined in a model by means of the electrical analogy method show that it is possible in the counterflow shaft 2 as well as in the calcining shaft 1 -to exhaust practically the entire amount of cooling air by means of the bIower 3 if the exhaust ducts 11 for the counterflow shaft are arranged at the outer side wall, i.e. the wall facing away from shaft 1 and those for the calcining shaft 1 are arranged at the inner side, i.e., the wall facing toward the shaft 2.
The design of the two-shaft furnace iIlustrated in Fig. 4 is basically the same as the design of the furnace in Fig. 1, except that the shaEts of the furnace of Fig. 4 are formed with a circular cross-section while the shafts of the furnace of Fig.l have a quadrilateral cross-section.
Accordingly, the same parts are provided with the same reference numerals and they are no~ again described~
The flue gases 6 enriched with the CO2 from the deacidlfication procedure flow from the calcining zone B of the uniflow shaft 1 through overflow ducts 20 into the counterflow shaft 2, while the heated cooling air 10 flows off through a central hollow cylinder 21. In furnaces having large shaft diameters, between the central hollow cylinder 21 and the cooling zone wall 22 there are advantag,eously provided roof-like cross-vaults or beams 23 which facilitate a uniform removal of the preheated cooling air. In the case of smaller shaft diameters, a cover 24 is provided above the central hollow cylinder 21.
.
.
4~
The thermal balance of the preheating zone V is demonstrated with the aid of an example in accordance with the followiny: .
Let it be assumed that:
- the deacidification of the limestone beqins at 810C~I the temperature difference between limestone and flue gas at the beginnlng of the calcining zone B is 30C and, accordingly, the temperature of the flue gases entering the preheating 20ne V from the calcining zone B~is 840C~;
- there is a free CaO of 94%;
- the heat loss of the furnace walls ln the preheating zone is 10 kcal/kg lime; and , - the temperature of the cooling alr which;is preheated and removed from the cooling zone K is 800C.
The amount of coollng air is assumed to be 0.6Nn3/kg*
lime~. This amount is completely Femoved.
The cooling air has a temperature at intake of 10C
and a temperature of 40C a~ter compression.
Heating ls performed by means of natural gas, the heat consumption being 900 kcal/kg. The combustion of the ormal cubic meter per kilogram ~.2~3 natural gas takes place with a theoretical air consumption of 1007 Nm 3/kg and results in a flue gas amount of 1.135 Nm 3/kg. In addition, there are 0.365 Nm 3/kg expelled CO2 so that the entire amount of flue gas entering the preheat-ing zone is 1.50 Nm 3 kg lime and its exhaust temperat~lre is 100~.
Heat of the flue gas from the calcining z~one B may be calculated as follows:
1~50 x 0.397 x 840 - ln5 x 100 x 0~349 - 10 -437.87 Kcal/kg Heat requirements for preheating the limestone may be calculated as follows:
1.74 x 0.260 x (310 - 103 = 361.92 kcal/kg Heat for preheating the combustion air may be calculated as follows:
1.007 x 0.33 x (840 - 40) = 265.84 kcal/kg The sum of the last two calculations is:
627.76 kcal/ky The heat deicit in the preheating zone without utilization of the preheated cooling air may be calculated as follows:
627.76 - 437~87 = 189.89 kcal!kc~
.
~v2~5~
The removed and heated cooling air has a heat content of 0.60 x 0.33 x 800 = 158.40 kcal/kg. Of this amount, there are losses for h'eating the stone o~ltside of the shafts at an ass~ned air exhaust temperature of 80C
of 0.6 x 0.33 x 80 ='15~84 kcal, further assumed losses in walls and lines of 10.00 kcal, and losses for water evapora-tion of the stone of 13.00 kcal with.'the , total losses being 38.84 kcal:. ' Accordingly, 158.40 - 38.84 = 119.56 kcalJkg are picked up and recupera'ted ~rom the stone. This results in a limestone heatiny of lI9.56 = 264.3C.
' 1.74x0.26 After adding the recuperative.heating of the stone, the heat deficit in the preheating zone is 189.89 - 119.56 = 70.33 kcal/kg, which must be compensated by an increased fuel supply. This heat deficit in the preheating zone according to the process c~escribed above is about the same as in the pure regenerative process in which about 64 kcal/kg are generated in the combustion 3 with 20~ excess air, an amount of cooling air of 0.6 Nm3~kg and an exhaust yas temperature of 80C.
In the regenerative process, the calcining cycle is changed in certain time intervals. In accordance with the .
above-described process, it` is important to effect control .
in such a way that the limestone which is recuperatively preheated outside of the furnace is charged into that shaft _ 9 _ , .
in which the calc ning subsequentlv takes place in uniflow, so that the cold combustion air meets the preheated limestone~
The advantages of the ahove-described pxocess reside essentially in the fac-t that the regenerative system of the furnace is relieved and that this results in significant improvements with respect to operation, production and utilization of the furnace.
Frequently, there is only available limestone which is unwashed, significantly contaminated and also very wet, such as, for example, chalk-like limestone with 10 to 20~ water content~ This leads to difficultles during transport of the material into the furnace since a substantial amount of fine material which cannot be separated during sifting adheres to the stone and negatively influences the furnace operation during calcining. During winter, there is the additional problem that the wet limestone pieces can .
freeze together into large lumps and can block -the chargina.
There also result problems during weighing of the limestone to be charged, these problems becoming troublesome when the water content of the material significantly varies due to seasonal influences.
The moisture content of the limestone is usually not measured before weighing. However, the amount of fuel to be supplied should be adjusted to the water content of the stone if a good and uniform quality of lime is to be obtained. This disadvantage is eliminated b~ introducing the limestone either completely dried or predried ~ith a uniform moisture content.
' - ' ,, ' , By directly conveying the heat of the cooling air removed from the reyenerative system and heatcd by the calcined lime to the limestone to be charged, or into a container on the furnace, a heat utilization is achieved which is about as good as ln the preheating zone of the regenerated system. Furthermore, the undersized and especially now also the dried fine material can be easlly separated from the limestone grain size intended for calclning before weighing and before the limestone is charged in the furnace.
., . , .
Another opportunity for utilizing the process is available whereby pellets of chalkstone prepared, ~or example, on a granulating plate with the addition of water can be dried and hardened by means of heated cooling air before being charged in the furnace.
- A variation of the process resides in that an entire or partial amount of the air heated in the cooling zone of the furnace is partially conducted over a recuperator and is used for preheating the combustion air to a temperature of, for example, 150C or 200~C, while maintaining an acceptable e~haust gas temperature. As a result, during i start-up of the furnace the flue yases can be safely prevented fro~ falling below the dew point, which would otherwise create a disturbing influence on a subsequent dust-collectiny system. -, . .
~.2~
Another variation of the process resides in the division of -the preheated cooling air to the recuperative preheating of thé mater~al -to be calcined and to the combustion air in such a manner that a portion of the preheated cooling air is admixed with the cold air which is additionally required for combustion.
Due to the complete or partial removal of the heated cooling aLr, a further significant advantage of the process resides in the fact that the partial pressure of the carbon dioxide in the exhaust gas can be adjusted to a desired-or a possible maximum value. Another advantage resides in the fact that the a~ount of cooling àir can be limited to the temperature desired for cooling the calclned lime, to wit, to about 0.6 to 0.7 Nm3/kg llme. This is because, under the hot and moist climatic conditions with high humidity and a high temperature of the air entering the coollng zone, the hydration of the calcined lime results in a significant temperature increase of the lime to be discharged. The heat consumption is thereby also increased, the heat consumption being increased with an increase in the amount of cooling air.
.
Due to the fact that the fuel ls supplied at the beginning of the deacidification zone, the uniflow calcining process facilitates the admission oE a very high heat which can be fully utilized in accordance with the processes previously described.
~.2~ 3 However~ since, according to -the new process, the cooliny alr does not flow off through the countershaft, the pressure difference between the two shaft heads is .
reduced, whereby the heat supply and the deficiency of the furnace can be raised.by about 30 -to 50%. .
Cooling air and combustion air are advantageously .
supplied by means of rotary compressors so that the furnace can operate undèr pressure. In this manner, the circulation of dust-containing gases in the compressors is avoidedO ~ .
further advantage resides in the fact that no cooling elements are required in the process of.the invention.
While specific embodiments o~ the lnvention have been shown and described in detail to illustrate the application of the inventive principles, it will be under- .
stood that the invention may be embodied otherwise without departlng from such prlnciples.
'' ', ' ,,' . I `~' . , .
.,
BACKGROUND OF THE INVENTION
.
The invention relates generally to a process for , calcining raw materials, such as limestone, dolomite or maynesite, in a uniflow regenerative shaft furnace having at least two shafts, wherein simultaneous cooling of caLcined lime in the cooling zones of`the shafts i5 performed.
A regenerative approach for strongly endothermic processes such as for example, the calcining of limestone, known from German AT-PS 211,214, has frequently been used~
for the construction of uniflow/counterflow shaft furnaces having two or three shafts and i has also frequently been described in the literature, among others, by E. SchieIe and L.W. Berens in the book "Xalk" (lime) pages 147-151, published by Verlay Stahl-Eisen, D~sseldorf (W. Germany).
The exclusively regenerative utilization of the heat carrier in this calclning process has been very successful because in the preheating zone of the shafts, not only the material to be calcined, but also the combustion air are preheated. The regenerative preheatina of the combustion air constitutes the thermo-technological feature of such a furnace.
It would seem difficult to practlcall~i improve this calclning process particularly with respect to heat -technology involved.
However, the process has been found not to meet all o~ the requirements with respect to its operational parameters.
It is, therefore, the task of the present invention to provide an improvement in the aforementioned calcining process in this regard.
.' ' ~
3 ~:
SU~'LM~RY OF THE INVENTION
, In accordance with the basic principles of the invention, cooling air which is heated in the cooling zone of the fuxnace by the calcined raw material is removed at least partially fro~ the furnace at the end of the cooling zone and its heat content is recuperatively utlli2ed , outside of the furnace shafts for preheating the raw materials which are supplied to the furnace andjor for preheating the combustion air to be supplied at the upper end of the pre-heating zone.
The various features of novelty which characterize ~ :
: . the invention are pointed out with particularity in the claims : . annexed to and forming a part of thls disclosure. For a better : understanding of the invention, its operating advantages and .
~ specific objects attained by its use, reference should be had .
to the accompanying drawings and descriptive matter in which there are illustrated and described preferred e~bodiments o the invention.
D CRIPTION OF THE DR_WINGS
' In the Drawings:
Fig. 1 is a schematic illustration of a two.shaft . urnace with a square or rectang~lar cross-section;
' . - 3 -~ z~5~3 Fig. 2 is a pressure model for the cooling zone of the counterflow shaf~ of a regenerative shaft furnacer wherein there occurs removal of an amount of cooling air at the outer side wall;
Fig. 3 is a pressure model for the cooling zone of the uniflow shaft of a~ reyenerative shaft furnace, wherein there occurs removal of an amount of coollng air at the inner side wall; and Fig. 4 is a schematic illustration of a two-shaft furnace with circular shaft cross-section.
.
; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Illustrated in Fig. 1 is a two-shaft furnace .
operate~ in uniflow wherein the shaft 1 operates as the calcining shaft and wherein the shaft 2 operates as the counterflow shaft. The shafts 1, 2 each define a preheating zone V, a calcining zone B, an after-deacidification zone N
and a cooling zone K. Combustion air and the cooling air are supplied by means of a blower 3 or 4, e.g. a rotary compressor. Fuel enters the calcining shaft 1 in Fig. 1 thxough burners 5 approximately at the beginn;ng of the calcining zone B~ Flue gases symbolically illustrated by an arrow 6 and enriched by CO2 which emerge from the ~L~.Z4~ ~
limestone initially flow downwardly parallel with the charge, then further in the counterflow shaft 2 and~ in the 'shaft 2, upwardly opposite the charging'movement to the exhaust 7.
The cooling air 10 which is supplied through a line 8 to the two shafts 1, 2 over sliding tables 9 serving to dlscharge the calcined material, flows upwardly in.the cooli.ng zone K, ancl after preheating through the calcined lime, it flows laterally outwardly through exhaust ducts 11 through a dust-collecting device, e.g., a cyclone, and through a line 13 into a limestone preheater 14 or through an alr recuperator 15 to the furnace exterior or to a dust-collecting system (not shown).
The combustion air delivered by the'blower 4 th~rough a line 16 enters the shaft 1 at the top either dlrectly through a line 17 or through the air regulator 15.
The limestone preheated and predried in the charging bucket or .
ladle 18 is, as required, supplied to one or the other of the shafts 1 or 2~ A change is made after the termination of the calcining procedure in the shaft 1 and the shaft 2 becomes the calcining shaft and the shaft 1 become5 the counterflow shat.
' Figs. 2 and 3 graphically depict flow conditions in the after-deacidification zone N and in the cooling zone K f the count~rflow sha-t 2 and the calcining shaft 1.
The results determined in a model by means of the electrical analogy method show that it is possible in the counterflow shaft 2 as well as in the calcining shaft 1 -to exhaust practically the entire amount of cooling air by means of the bIower 3 if the exhaust ducts 11 for the counterflow shaft are arranged at the outer side wall, i.e. the wall facing away from shaft 1 and those for the calcining shaft 1 are arranged at the inner side, i.e., the wall facing toward the shaft 2.
The design of the two-shaft furnace iIlustrated in Fig. 4 is basically the same as the design of the furnace in Fig. 1, except that the shaEts of the furnace of Fig. 4 are formed with a circular cross-section while the shafts of the furnace of Fig.l have a quadrilateral cross-section.
Accordingly, the same parts are provided with the same reference numerals and they are no~ again described~
The flue gases 6 enriched with the CO2 from the deacidlfication procedure flow from the calcining zone B of the uniflow shaft 1 through overflow ducts 20 into the counterflow shaft 2, while the heated cooling air 10 flows off through a central hollow cylinder 21. In furnaces having large shaft diameters, between the central hollow cylinder 21 and the cooling zone wall 22 there are advantag,eously provided roof-like cross-vaults or beams 23 which facilitate a uniform removal of the preheated cooling air. In the case of smaller shaft diameters, a cover 24 is provided above the central hollow cylinder 21.
.
.
4~
The thermal balance of the preheating zone V is demonstrated with the aid of an example in accordance with the followiny: .
Let it be assumed that:
- the deacidification of the limestone beqins at 810C~I the temperature difference between limestone and flue gas at the beginnlng of the calcining zone B is 30C and, accordingly, the temperature of the flue gases entering the preheating 20ne V from the calcining zone B~is 840C~;
- there is a free CaO of 94%;
- the heat loss of the furnace walls ln the preheating zone is 10 kcal/kg lime; and , - the temperature of the cooling alr which;is preheated and removed from the cooling zone K is 800C.
The amount of coollng air is assumed to be 0.6Nn3/kg*
lime~. This amount is completely Femoved.
The cooling air has a temperature at intake of 10C
and a temperature of 40C a~ter compression.
Heating ls performed by means of natural gas, the heat consumption being 900 kcal/kg. The combustion of the ormal cubic meter per kilogram ~.2~3 natural gas takes place with a theoretical air consumption of 1007 Nm 3/kg and results in a flue gas amount of 1.135 Nm 3/kg. In addition, there are 0.365 Nm 3/kg expelled CO2 so that the entire amount of flue gas entering the preheat-ing zone is 1.50 Nm 3 kg lime and its exhaust temperat~lre is 100~.
Heat of the flue gas from the calcining z~one B may be calculated as follows:
1~50 x 0.397 x 840 - ln5 x 100 x 0~349 - 10 -437.87 Kcal/kg Heat requirements for preheating the limestone may be calculated as follows:
1.74 x 0.260 x (310 - 103 = 361.92 kcal/kg Heat for preheating the combustion air may be calculated as follows:
1.007 x 0.33 x (840 - 40) = 265.84 kcal/kg The sum of the last two calculations is:
627.76 kcal/ky The heat deicit in the preheating zone without utilization of the preheated cooling air may be calculated as follows:
627.76 - 437~87 = 189.89 kcal!kc~
.
~v2~5~
The removed and heated cooling air has a heat content of 0.60 x 0.33 x 800 = 158.40 kcal/kg. Of this amount, there are losses for h'eating the stone o~ltside of the shafts at an ass~ned air exhaust temperature of 80C
of 0.6 x 0.33 x 80 ='15~84 kcal, further assumed losses in walls and lines of 10.00 kcal, and losses for water evapora-tion of the stone of 13.00 kcal with.'the , total losses being 38.84 kcal:. ' Accordingly, 158.40 - 38.84 = 119.56 kcalJkg are picked up and recupera'ted ~rom the stone. This results in a limestone heatiny of lI9.56 = 264.3C.
' 1.74x0.26 After adding the recuperative.heating of the stone, the heat deficit in the preheating zone is 189.89 - 119.56 = 70.33 kcal/kg, which must be compensated by an increased fuel supply. This heat deficit in the preheating zone according to the process c~escribed above is about the same as in the pure regenerative process in which about 64 kcal/kg are generated in the combustion 3 with 20~ excess air, an amount of cooling air of 0.6 Nm3~kg and an exhaust yas temperature of 80C.
In the regenerative process, the calcining cycle is changed in certain time intervals. In accordance with the .
above-described process, it` is important to effect control .
in such a way that the limestone which is recuperatively preheated outside of the furnace is charged into that shaft _ 9 _ , .
in which the calc ning subsequentlv takes place in uniflow, so that the cold combustion air meets the preheated limestone~
The advantages of the ahove-described pxocess reside essentially in the fac-t that the regenerative system of the furnace is relieved and that this results in significant improvements with respect to operation, production and utilization of the furnace.
Frequently, there is only available limestone which is unwashed, significantly contaminated and also very wet, such as, for example, chalk-like limestone with 10 to 20~ water content~ This leads to difficultles during transport of the material into the furnace since a substantial amount of fine material which cannot be separated during sifting adheres to the stone and negatively influences the furnace operation during calcining. During winter, there is the additional problem that the wet limestone pieces can .
freeze together into large lumps and can block -the chargina.
There also result problems during weighing of the limestone to be charged, these problems becoming troublesome when the water content of the material significantly varies due to seasonal influences.
The moisture content of the limestone is usually not measured before weighing. However, the amount of fuel to be supplied should be adjusted to the water content of the stone if a good and uniform quality of lime is to be obtained. This disadvantage is eliminated b~ introducing the limestone either completely dried or predried ~ith a uniform moisture content.
' - ' ,, ' , By directly conveying the heat of the cooling air removed from the reyenerative system and heatcd by the calcined lime to the limestone to be charged, or into a container on the furnace, a heat utilization is achieved which is about as good as ln the preheating zone of the regenerated system. Furthermore, the undersized and especially now also the dried fine material can be easlly separated from the limestone grain size intended for calclning before weighing and before the limestone is charged in the furnace.
., . , .
Another opportunity for utilizing the process is available whereby pellets of chalkstone prepared, ~or example, on a granulating plate with the addition of water can be dried and hardened by means of heated cooling air before being charged in the furnace.
- A variation of the process resides in that an entire or partial amount of the air heated in the cooling zone of the furnace is partially conducted over a recuperator and is used for preheating the combustion air to a temperature of, for example, 150C or 200~C, while maintaining an acceptable e~haust gas temperature. As a result, during i start-up of the furnace the flue yases can be safely prevented fro~ falling below the dew point, which would otherwise create a disturbing influence on a subsequent dust-collectiny system. -, . .
~.2~
Another variation of the process resides in the division of -the preheated cooling air to the recuperative preheating of thé mater~al -to be calcined and to the combustion air in such a manner that a portion of the preheated cooling air is admixed with the cold air which is additionally required for combustion.
Due to the complete or partial removal of the heated cooling aLr, a further significant advantage of the process resides in the fact that the partial pressure of the carbon dioxide in the exhaust gas can be adjusted to a desired-or a possible maximum value. Another advantage resides in the fact that the a~ount of cooling àir can be limited to the temperature desired for cooling the calclned lime, to wit, to about 0.6 to 0.7 Nm3/kg llme. This is because, under the hot and moist climatic conditions with high humidity and a high temperature of the air entering the coollng zone, the hydration of the calcined lime results in a significant temperature increase of the lime to be discharged. The heat consumption is thereby also increased, the heat consumption being increased with an increase in the amount of cooling air.
.
Due to the fact that the fuel ls supplied at the beginning of the deacidification zone, the uniflow calcining process facilitates the admission oE a very high heat which can be fully utilized in accordance with the processes previously described.
~.2~ 3 However~ since, according to -the new process, the cooliny alr does not flow off through the countershaft, the pressure difference between the two shaft heads is .
reduced, whereby the heat supply and the deficiency of the furnace can be raised.by about 30 -to 50%. .
Cooling air and combustion air are advantageously .
supplied by means of rotary compressors so that the furnace can operate undèr pressure. In this manner, the circulation of dust-containing gases in the compressors is avoidedO ~ .
further advantage resides in the fact that no cooling elements are required in the process of.the invention.
While specific embodiments o~ the lnvention have been shown and described in detail to illustrate the application of the inventive principles, it will be under- .
stood that the invention may be embodied otherwise without departlng from such prlnciples.
'' ', ' ,,' . I `~' . , .
.,
Claims (12)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a process for calcining mineral raw materials, such as limestone, dolomite or magnesite, in a uniflow regenerative shaft furnace having at least two shafts each defining a cooling zone wherein simultaneous cooling of calcined lime with cooling air is effected in said cooling zones of said shafts, the improvement comprising the steps of at least partially removing at the end of said cooling zone cooling air which has been heated by calcined raw material in said cooling zone; and recu-peratively utilizing the heat content of said removed cooling air outside of said furnace shafts for preheating at least one of the raw materials to be supplied to said furnace and combustion air to be supplied to a preheating zone of said furnace.
2. Process according to Claim 1, wherein said cooling zone includes side walls and wherein said removed preheated cooling air is removed at said side walls of said cooling zone.
3. Process according to Claim 2, wherein said at least two shafts have a quadrilateral cross-section and wherein the preheated cooling air of the uniflow shaft is removed on the inner side wall and the preheated cooling air of the counterflow shaft is removed at the outer side wall of the cooling zone.
4. Process according to Claim 2, wherein said at least two shafts have a circular shaft cross-section and wherein the preheated cooling air is removed inwardly and downwardly through a central hollow cylinder arranged in the cooling zone.
5. Process according to Claim 4, wherein the preheated cooling air is removed downwardly through free space beneath beams extending in a crossed manner between the brickwork of the sides of the cooling zone at said furnace and a central hollow cylinder and further through the interior of said hollow cylinder.
6. Process according to Claim 1, wherein the cooling air which is preheated and removed from the furnace is supplied at the lower end of a limestone container located immediately above said furnace shafts.
7. Process according to Claim 1, wherein the preheated cooling air is supplied to a limestone container which is arranged ahead of a stone elevator in said furnace.
8. Process according to Claim 1 wherein said cooling air which is preheated and removed from the furnace is utilized for preheating at least one limestone outside of said furnace and combustion air in a recuperator.
9. Process according to Claim 1, wherein said cooling air which is preheated and removed from said furnace is mixed at least partially with cold combustion air.
10. Process according to Claims 1, 4 or 5 wherein limestone which is recuperatively preheated outside of the furnace is admitted to the uniflow regenerative furnace after having been predried at least to a uniform moisture content.
11. Process according to Claim 1, wherein the composition of the exhaust gases flowing from the uniflow regenerative furnace are controlled to a maximum of CO2.
12. Process according to Claim 1, wherein as compared to a process with exclusively regenerative heat utilization occurring in the preheating stage, an efficiency is obtained which is 30 to 50% higher.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH968378A CH637760A5 (en) | 1978-09-15 | 1978-09-15 | Method for burning mineral, carbonate-containing raw materials in the co-current regenerative shaft furnace |
| CH9683/78 | 1978-09-15 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1124513A true CA1124513A (en) | 1982-06-01 |
Family
ID=4354532
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA335,698A Expired CA1124513A (en) | 1978-09-15 | 1979-09-14 | Process for calcining mineral raw materials in a uniflow regenerative shaft furnace |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS5816932B2 (en) |
| AT (1) | AT372519B (en) |
| CA (1) | CA1124513A (en) |
| CH (1) | CH637760A5 (en) |
| DE (1) | DE2927834A1 (en) |
| FR (1) | FR2436346A1 (en) |
| SE (1) | SE7906176L (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102630294A (en) * | 2009-12-15 | 2012-08-08 | 梅尔兹·奥芬布股份有限公司 | Parallel flow-counter flow regenerative lime kiln and method for the operation thereof |
| CN104501578A (en) * | 2014-12-18 | 2015-04-08 | 南京净环热冶金工程有限公司 | Multistage heat-storage double shaft kiln type calcinator |
| CN105452186A (en) * | 2013-08-05 | 2016-03-30 | 麦尔兹欧芬堡股份公司 | Process for burning and cooling carbonate rock in a parallel-flow regenerative lime kiln, and a parallel-flow regenerative lime kiln |
Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3006980A1 (en) * | 1980-02-25 | 1981-09-10 | Krupp Polysius Ag, 4720 Beckum | Cement mfg. plant using fluidised bed - where part of air preheated in clinker cooler is used to heat air of combustion carrying precalcined cement flour into bed |
| CH647313A5 (en) * | 1980-04-30 | 1985-01-15 | Maerz Ofenbau | REGENERATIVE SHAFT OVEN FOR THE BURNING OF CARBONATE-CONTAINING RAW MATERIALS. |
| DE3409727C2 (en) * | 1984-03-16 | 1990-03-29 | Peter Dipl.-Ing. 4630 Bochum Zeisel | Process for firing and sintering lumpy material such as limestone or dolomite |
| DE3601572A1 (en) * | 1986-01-21 | 1987-08-06 | Steine & Erden Gmbh | DEVICE FOR RECUPERATIVE PREHEATING FROM A LIMEWELL OVEN OR THE LIKE SUPPLIED AIR |
| JPH02597U (en) * | 1988-06-14 | 1990-01-05 | ||
| EP1038851B1 (en) * | 1999-02-27 | 2001-05-09 | Peter Dipl.-Ing. Zeisel | Process for firing a lumpy, burnable charge expecially limestone, dolomite and magnesite, and a regenerative shaft furnace for carrying out the process |
| DE10324953A1 (en) * | 2003-06-03 | 2004-12-23 | Maerz Ofenbau Ag | Method for firing lumpy kiln |
| DE102006039204B4 (en) * | 2006-08-22 | 2011-12-08 | Rheinkalk Gmbh | Annular shaft kiln |
| DE102010036587A1 (en) | 2009-07-23 | 2011-01-27 | Caldery France S.A.S. | Hanging wall for deflecting hot gases in calcium carbonate burning furnace, has recesses provided for fastening of wall elements and area of refractory material, where fixed weight of material does not exceed strength of material of holders |
| DE102010016059A1 (en) * | 2010-03-22 | 2011-11-24 | Polysius Ag | Process for the preparation of chalk lime |
| DE102016104076A1 (en) * | 2016-03-07 | 2017-09-07 | Maerz Ofenbau Ag | Plant with a furnace and method of operating such a plant |
| DE102020004372A1 (en) | 2020-07-20 | 2022-01-20 | Maerz Ofenbau Ag | Co-current counter-current regenerative shaft kiln and method for firing carbonate rock |
| CN114014563B (en) * | 2021-11-11 | 2023-09-15 | 广西盛隆冶金有限公司 | Automatic time-sharing reversing system and reversing method for double-chamber lime kiln |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1087071B (en) * | 1952-11-12 | 1960-08-11 | Hildegard Seeger Geb Brockhaus | Method and shaft furnace for burning lumpy limestone or the like. |
| DE1008641B (en) * | 1954-10-21 | 1957-05-16 | Rheinische Kalksteinwerke | Method and device for burning limestone, dolomite or magnesite in a gas-heated shaft furnace with exhaust gas circulation |
| AT211214B (en) * | 1958-08-09 | 1960-09-26 | Alois Schmid | Process for carrying out any endothermic processes in the shaft furnace, e.g. B. for burning lime, and furnace for carrying out the process |
| DE1157133B (en) * | 1958-08-09 | 1963-11-07 | Alois Schmid | Process for burning and cooling grainy goods, e.g. of limestone in the shaft furnace, and furnace for practicing the process |
| FR1440786A (en) * | 1965-04-21 | 1966-06-03 | Sofim Saar Saarofenbau Fuer In | Method for firing limestone and device for carrying out this process |
| AT301430B (en) * | 1970-08-27 | 1972-09-11 | Beckenbach Karl | Inclined furnace |
| GB1510877A (en) * | 1975-09-24 | 1978-05-17 | Zytan Anlagenbau Gmbh | Shaft kiln |
-
1978
- 1978-09-15 CH CH968378A patent/CH637760A5/en not_active IP Right Cessation
-
1979
- 1979-07-10 DE DE19792927834 patent/DE2927834A1/en not_active Withdrawn
- 1979-07-11 AT AT482379A patent/AT372519B/en not_active IP Right Cessation
- 1979-07-18 SE SE7906176A patent/SE7906176L/en not_active Application Discontinuation
- 1979-08-16 FR FR7920765A patent/FR2436346A1/en active Granted
- 1979-09-14 CA CA335,698A patent/CA1124513A/en not_active Expired
- 1979-09-14 JP JP54117469A patent/JPS5816932B2/en not_active Expired
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102630294A (en) * | 2009-12-15 | 2012-08-08 | 梅尔兹·奥芬布股份有限公司 | Parallel flow-counter flow regenerative lime kiln and method for the operation thereof |
| CN102630294B (en) * | 2009-12-15 | 2014-10-15 | 梅尔兹·奥芬布股份有限公司 | Parallel flow-counter flow regenerative lime kiln and method for the operation thereof |
| US9011143B2 (en) | 2009-12-15 | 2015-04-21 | Maerz Ofenbau Ag | Parallel flow regenerative lime kiln and method for the operation thereof |
| CN105452186A (en) * | 2013-08-05 | 2016-03-30 | 麦尔兹欧芬堡股份公司 | Process for burning and cooling carbonate rock in a parallel-flow regenerative lime kiln, and a parallel-flow regenerative lime kiln |
| US10301219B2 (en) | 2013-08-05 | 2019-05-28 | Maerz Ofenbau Ag | Parallel-flow regenerative lime kilns and processes for burning and cooling carbonate rock in same |
| CN104501578A (en) * | 2014-12-18 | 2015-04-08 | 南京净环热冶金工程有限公司 | Multistage heat-storage double shaft kiln type calcinator |
Also Published As
| Publication number | Publication date |
|---|---|
| ATA482379A (en) | 1983-02-15 |
| SE7906176L (en) | 1980-03-16 |
| FR2436346A1 (en) | 1980-04-11 |
| FR2436346B1 (en) | 1984-08-31 |
| CH637760A5 (en) | 1983-08-15 |
| DE2927834A1 (en) | 1980-03-27 |
| AT372519B (en) | 1983-10-25 |
| JPS5816932B2 (en) | 1983-04-04 |
| JPS5539300A (en) | 1980-03-19 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1124513A (en) | Process for calcining mineral raw materials in a uniflow regenerative shaft furnace | |
| US4225332A (en) | Energy efficient pollution abating glass manufacturing process with external recovery of heat from furnace flue gases | |
| US8557039B2 (en) | Method for manufacturing a sulfoaluminous or belitic sulfoaluminous clinker, and corresponding equipment | |
| GB1506589A (en) | Process of and apparatus for heat-treating material and conditioning waste exhaust gases | |
| US4298340A (en) | Method and apparatus for producing a hydraulic binder | |
| US4022568A (en) | Method and apparatus for heat treating pulverous raw materials | |
| AU2391301A (en) | Method and apparatus for manufacturing cement clinker from particulate cement raw material | |
| CA1124514A (en) | Uniflow regenerative shaft furnace for calcining limestone utilizing fuels in fine particulate form | |
| GB2043853A (en) | Method and apparatus for making cement clinker | |
| CA1097501A (en) | Method of burning granular or pulverulent raw material and kiln plant therefor | |
| GB1136864A (en) | Improved method of, and apparatus for, heat-treating minerals | |
| CS199570B2 (en) | Apparatus for calcinating and sintering cement-making raw materials | |
| US4588429A (en) | Method of heating particulate material with a particulate heating media | |
| US4229226A (en) | Method for the production of cement clinker low in sulphur | |
| US4534731A (en) | Process and apparatus for calcining limestone | |
| KR101131294B1 (en) | Method and plant for preheating particulate or pulverulent material | |
| US4662841A (en) | Method for burning and sintering limestone, dolomite and the like and plant for the implementation thereof | |
| CA2495568C (en) | Method and plant for manufacturing cement clinker | |
| US4670054A (en) | Heat processing of particulate material | |
| CN211367425U (en) | Three-chamber shaft kiln | |
| GB2155159A (en) | Producing sintered material | |
| CN110818289A (en) | Three-chamber shaft kiln and calcination method | |
| EP0030409B1 (en) | Method of and plant for manufacturing pulverous or granular material, for example cement | |
| RU2010780C1 (en) | Method of manufacturing cement clinkers and plant for production thereof | |
| CN2419205Y (en) | Mechanic activated lime calcinator by using coal as fuel |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |