Downstream-countercurrent heat accumulating type shaft kiln and carbonate rock combustion method

Abstract

The invention relates to a co-current / counter-current regenerative shaft kiln (1) for combusting and cooling materials such as carbonate rocks, comprising two shafts (2) which can be alternately used as a combustion shaft and a regenerative shaft and which are connected to one another by means of a connecting line (2), each shaft (2) comprises a preheating zone (21) for preheating the material, a combustion zone (20) for combusting the material, and a cooling zone (22) for cooling the material, the cooling zone (22) comprising a cooling gas inlet (23) for feeding a cooling gas into the cooling zone (22) and a cooling gas removal device (17) for discharging the cooling gas from the shaft (2), the post-calcination zone (9) is arranged downstream of the combustion zone (20) in the direction of flow of the material, the post-calcination zone being arranged and adapted such that it post-calcinates the material leaving the combustion zone (20) at a temperature of 800 DEG C to 1100 DEG C, in particular 900 DEG C to 1000 DEG C, preferably about 850 DEG C to 950 DEG C.

Description

Technical Field

[0001] The present invention relates to a pre-flow / counter-flow regenerative heat shaft kiln (PFR shaft kiln) and a method of burning and cooling a material such as carbonate rock using the PFR shaft kiln. Background Art

[0002] Carbonate combustion in PFR shaft kilns has been around for about 60 years. Such PFR shaft kilns, such as those described in WO 2011 / 072894 A1, have two vertical, parallel shafts operating in a circular pattern. Combustion occurs only in one shaft, the combustion shaft, while the other shaft serves as a heat storage shaft. Oxidizing gas is supplied to the combustion shaft co-currently with the charge and fuel. The resulting hot exhaust gas, along with heated cooling air supplied from below, is directed via a crossover line to the exhaust gas shaft, where it is directed upwards in counter-current to the charge, preheating the charge. The charge is typically supplied to the shaft from above along with the oxidizing gas, and fuel is injected into the combustion zone.

[0003] In each shaft, the material to be combusted typically passes through a preheating zone for preheating the material, a downstream combustion zone for combusting the material, and a downstream cooling zone for supplying cooling air to the hot material.

[0004] To meet the high reactivity quality requirements of quicklime, such as those in steel mills, the temperature in the combustion zone must not exceed 1100°C, preferably 1000°C. Furthermore, there is a growing demand for environmentally friendly quicklime production, which necessitates meeting specific requirements for the CO2 content in the waste gas for subsequent post-treatment. Furthermore, a high degree of calcination is also a requirement for the final product. Summary of the Invention

[0005] The object of the present invention is therefore to provide a PFR shaft kiln and a method for burning carbonate rocks using a PFR shaft kiln, which can produce lime with high reactivity and high calcination, wherein the exhaust gases simultaneously have a high CO2 content, thereby allowing economical and efficient separation from the exhaust gases.

[0006] According to the invention, this object is achieved by an apparatus having the features of the independent apparatus claim 1 and by a method having the features of the independent method claim 12. Advantageous developments are disclosed in the dependent claims.

[0007] In a first aspect, the present invention comprises a co-current / counter-current regenerative shaft kiln for burning and cooling a material such as carbonate rock. The kiln comprises two shafts that can be used alternately as a combustion shaft and a regenerative shaft and are interconnected by a connecting pipeline. Each shaft comprises, along the direction of material flow, a preheating zone for preheating the material, a combustion zone for burning the material, and a cooling zone for cooling the material. The cooling zone comprises a cooling gas inlet for introducing cooling gas into the cooling zone and a cooling gas removal device for discharging the cooling gas from the shaft. A post-calcination zone is disposed downstream of the combustion zone along the direction of material flow. The post-calcination zone is configured and adapted to post-calcine the material exiting the combustion zone at an air temperature of 800°C to 1100°C, particularly 900°C to 1000°C, and preferably approximately 850°C to 950°C.

[0008] The post-calcination zone is preferably located immediately after the combustion zone. Each shaft preferably includes a flow channel leading to a connecting line, wherein the post-calcination zone is located completely downstream of the flow channel, particularly in the direction of material flow. The flow channel leading to the connecting line is preferably arranged within the combustion zone or at the transition between the combustion zone and the post-calcination zone. The post-calcination zone, for example, extends from the flow channel in the direction of material flow.

[0009] The material to be combusted is preferably limestone or dolomite, and its particle size is 10 mm to 200 mm, preferably 15 mm to 120 mm, and most preferably 30 mm to 100 mm. The cooling gas is, for example, air.

[0010] The post-calcination zone is preferably arranged between the combustion zone and the cooling zone, so that the material is passed directly into the post-calcination zone after the combustion zone and post-calcined therein. During the post-calcination, the material components that have not been calcined in the combustion zone are subsequently calcined, wherein the air temperature in the post-calcination zone is lower than that in the combustion zone, but higher than the calcination temperature of the material.

[0011] Each shaft preferably has a material inlet for feeding the material to be combusted into the shaft. The material inlet is preferably located at the upper end of the respective shaft so that the material falls into the respective shaft under the action of gravity. The material inlet and / or material outlet are preferably in the form of a sluice for feeding the material into the shaft kiln and / or discharging the material from the shaft kiln. The sluice-like material inlet is preferably designed so that only the raw material to be combusted can enter the shaft, and not the ambient air. The material sluice also prevents gases from escaping the shaft through the material inlet. The sluice is preferably designed to seal the shaft gas-tight from the environment while allowing solids, such as the material to be combusted, to enter the shaft.

[0012] The connecting line is designed for gas connection between the two shafts and preferably connects the combustion zones of the shafts to each other. The flow channel is preferably connected to the connecting channel 19 for gas connection to the shafts and is particularly arranged at the lower end of the combustion zone so that fuel gas flows from the combustion zone into the flow channel. The post-calcination zone is preferably arranged between the combustion zone and the flow channel in the direction of fuel gas flow so that fuel gas flows from the combustion zone into the post-calcination zone, is preferably deflected therein, and is introduced directly into the flow channel downstream of the post-calcination zone.

[0013] During operation of a PFR shaft kiln, one of the shafts simultaneously operates as a combustion shaft and is active, while the corresponding shaft operates as a regenerative shaft and is inactive. PFR shaft kilns typically operate in cycles, with the shafts switching functions after the cycle time has expired. This process is repeated continuously. In the active shaft operating as a combustion shaft, fuel is introduced into the combustion zone via burner lances. The material to be combusted is heated to a temperature of preferably approximately 700°C in the preheating zone of the combustion shaft. In the shaft operating as a combustion shaft, the combustion zone is a co-current combustion zone, in which the material to be combusted flows parallel to the gas flow. Within the combustion shaft, the gas flows from the preheating zone into the combustion zone, then into the post-calcination zone and, via connecting lines, into the combustion zone and the preheating zone of the regenerative shaft. In the shaft operating as a regenerative shaft, the gas flow in the preheating zone and combustion zone is countercurrent to the material to be combusted.

[0014] In both the combustion shaft and the regenerative shaft, the cooling gas passes through the cooling zone in countercurrent to the material to be cooled and is preferably completely discharged from the shaft via the cooling gas outlet of the cooling gas removal device, so that preferably no cooling gas flows from the cooling zone into the combustion zone and the post-calcination zone.

[0015] Each shaft preferably has at least one exhaust gas outlet, for example, located at the upper end of the shaft within the preheating zone. The exhaust gas outlet is preferably arranged above the charge column in the preheating zone's charge-free area. Exhaust gas is preferably discharged from only one shaft, in particular the regenerative shaft. The discharged exhaust gas is preferably supplied to a corresponding further shaft, in particular the combustion shaft and / or the regenerative shaft, wherein the supply is effected, for example, via connecting lines at the level of the combustion zone or an inlet in the shaft wall. Preferably, only part of the exhaust gas discharged from the regenerative shaft is returned to at least one of the shafts. For example, part of the exhaust gas discharged from the regenerative shaft is discharged from the PFR shaft kiln and supplied, for example, for further treatment, such as storage. The exhaust gas preferably consists of CO2 and optionally H2O. The exhaust gas discharged from the shaft preferably has a CO2 content of greater than 90%, in particular from 95% to 99%, preferably 98%.

[0016] Recirculating the waste gas to at least one shaft allows for the production of highly reactive lime while simultaneously producing a process gas with a CO₂ content exceeding 90% (on a dry basis). This process waste gas can be liquefied and stored with relatively little complexity. For example, the liquefied process waste gas can be supplied to subsequent process steps or stored. The PFR shaft kiln described above can alternatively be used to produce waste gas with a lower CO₂ content, for example, 45% CO₂ for soda production, 35% CO₂ for sugar production, or 30% CO₂ for precipitated calcium carbonate production.

[0017] For example, the exhaust gas is introduced into the preheating zone or combustion zone of a shaft operating as a combustion shaft and / or into a connecting line and / or into the combustion zone or preheating zone of a shaft operating as a heat storage shaft. Each shaft preferably has a gas inlet, in particular a firing gas inlet, which is arranged in the upper region of the shaft in the preheating zone or combustion zone and is used to feed the gas required for firing. The temperature of the exhaust gas discharged from the shaft via the exhaust gas outlet is preferably about 60°C to 160°C, particularly preferably 100°C. Preferably, only part of the exhaust gas is introduced into the preheating zone or combustion zone of the combustion shaft. Recirculating the exhaust gas back into the preheating zone can increase the gas volume in the shaft while ensuring a high CO2 concentration in the exhaust gas.

[0018] Before being introduced into the shaft, in particular into the connecting line or into the combustion zone of a shaft operated as a heat storage shaft or combustion shaft, the exhaust gas is heated, for example, to a temperature of 900° C. to 1100° C., preferably 1000° C.

[0019] The cooling gas heated in the cooling zone is discharged from the cooling zone of the shaft, for example, via a cooling gas removal device. Specifically, the cooling gas fed into the cooling zone is completely discharged from the corresponding shaft via the cooling gas removal device. The cooling gas is preferably fed into the cooling zone from below via a cooling gas inlet arranged in the lower region of the cooling zone. The cooling gas removal device preferably has a cooling gas outlet for discharging the cooling gas from the shaft. The cooling gas outlet is preferably connected to a cooling gas removal line for conveying the removed cooling gas.

[0020] The shaft operating as a combustion shaft is preferably supplied with an oxidant. The oxidant is, for example, pure oxygen or an oxygen-enriched gas with an oxygen content of at least 70% to 95%, preferably 90%. The oxidant is preferably introduced into the preheating zone of the combustion shaft together with the exhaust gas. It is also conceivable for the shaft to have a separate oxidant inlet in the preheating zone for feeding the oxidant into the shaft separately from the exhaust gas. The oxidant is preferably supplied to the combustion zone together with the fuel. The oxidant line preferably has a control element, such as a valve or a damper, which can be used to adjust the amount of oxidant in the respective shaft.

[0021] Each shaft preferably contains at least one burner lance, wherein the exhaust gas is introduced, for example, into the burner lance. Each shaft preferably has multiple burner lances that extend at least partially through the preheating zone and, in particular, open into the combustion zone of the respective shaft and are used to carry, for example, fuel and / or oxidant gas, such as air, oxygen-enriched air, or pure oxygen. Fuel is preferably supplied to the combustion zone and / or preheating zone of the shaft operating as a combustion shaft via a fuel line. Fuel is preferably supplied via burner lances arranged in the combustion zone and / or preheating zone. The fuel is, for example, a fuel gas such as blast furnace gas or natural gas, or pulverized coal, biomass, or a liquid fuel. The material is preferably heated to a temperature of approximately 1100°C in the combustion zone. The exhaust gas is preferably introduced into the fuel line. To this end, the exhaust gas line is preferably connected to the fuel line and / or at least one burner lance. The exhaust gas is preferably introduced into the burner lances and / or fuel line downstream of a heat exchanger, wherein the heat exchanger is preferably used to heat the exhaust gas in countercurrent to the removed cooling gas. The exhaust gas is preferably introduced into the burner lances and / or fuel lines via control elements (such as dampers or valves) to regulate the exhaust gas flow in the burner lances and / or fuel lines. Each fuel line and / or burner lance is preferably equipped with a control element for regulating the exhaust gas flow in the corresponding burner lance and / or fuel line. The control element is preferably arranged in the exhaust gas line. The exhaust gas is particularly introduced into the burner lances of a shaft operating as a combustion shaft.

[0022] In a first embodiment, the post-calcination zone is at least partially or completely in the form of an annular space between the cooling gas removal device and the shaft wall.Preferably, only a very small proportion of cooling gas, if any, is present in the post-calcination zone.

[0023] In another embodiment, a gas separation zone for separating cooling gas and fuel gas is arranged between the post-calcination zone and the cooling zone. The gas separation zone is preferably used to separate the gases in the cooling zone from the combustion zone and the post-calcination zone. Preferably, the gas separation zone is located directly downstream of the post-calcination zone in the flow direction of the material, wherein the cooling zone is particularly located directly downstream of the gas separation zone. The gas separation zone is particularly arranged in a vertical shaft section with a substantially constant cross-section. Preferably, only the cooling gas from the cooling zone is introduced into the gas separation zone, wherein only a very small proportion of the fuel gas (if any, for example 0.5% to 10%, in particular 1% to 8%, preferably 2% to 6%) is passed from the combustion zone to the gas separation zone.

[0024] The configuration of the post-calcination zone and the optional gas separation zone ensures reliable separation of cooling gas and fuel gas, thus preventing re-carbonization. Post-calcination of the material also achieves a high degree of calcination.

[0025] In another embodiment, the length of the post-calcination zone extends in the direction of material flow, wherein the cooling zone is configured as an annular space surrounding the cooling gas removal device and has an outer diameter, and wherein the ratio of the length of the post-calcination zone to the outer diameter of the cooling zone, Ln / D1, is, for example, 0.4 to 0.8, particularly 0.5 to 0.7, and preferably 0.6. This ratio ensures that the fuel gas is reliably and completely deflected from the combustion zone within the post-calcination zone, so that only a very small proportion of the fuel gas (if any) enters the gas separation zone or the cooling zone, and the material can be almost completely calcined. The post-calcination zone, the gas separation zone, and the cooling zone are, for example, annular spaces, each having an outer diameter and an inner diameter.

[0026] In another embodiment, the length of the post-calcination zone extends in the direction of material flow, wherein the flow channel is configured as a material-free annular space and has an outer diameter, and wherein the ratio of the length of the post-calcination zone to the outer diameter of the flow channel, Ln / D5, is, for example, 0.3 to 0.7, preferably 0.4 to 0.6, and in particular 0.5. For example, in its upper region, the cross-sectional area of ​​the post-calcination zone is larger than that of the combustion zone, wherein the cross-sectional area of ​​the post-calcination zone decreases, in particular, in the direction of material flow. The combustion zone preferably extends from its lower region to the upper region of the post-calcination zone, thereby forming a flow channel in the form of an annular channel between the two shaft sections. The annular channel flow channel preferably forms a material-free space that does not contain the material to be combusted. The flow channel preferably extends circumferentially around the lower region of the combustion zone. For example, each shaft has a flow channel configured as an annular channel, which is in each case gaseously connected to the connecting channel and arranged at the same height as the connecting channel.

[0027] In another embodiment, the post-calcination zone configured as an annular space has an outer diameter that decreases in the direction of material flow at an angle of 0° to 30°, in particular 5° to 20°, preferably 10°, relative to the vertical direction, and / or the post-calcination zone has an inner diameter that decreases in the direction of material flow at an angle of 15° to 50°, in particular 25° to 35°, preferably 28°, relative to the vertical direction. This ensures optimal gravity-based material transport within the post-calcination zone, thereby preventing accumulation in the annular space and thus avoiding dust deposition and dust fouling.

[0028] In another embodiment, the cooling gas removal device comprises an inner cylinder having a cooling gas inlet arranged within the cooling zone. Furthermore, the cooling gas removal device preferably has a cover, which is arranged upstream of the cooling gas inlet in the direction of material flow. This cover thus reliably prevents material from entering the inner cylinder. The inner cylinder is preferably configured as a hollow cylinder and extends, in particular centrally, preferably coaxially with the cooling zone, through the zone, in particular to the level of the post-calcination zone. The inner cylinder is preferably connected to a cooling gas outlet for discharging the cooling gas from a shaft.

[0029] In another embodiment, the cooling gas removal device includes a particle separation device for separating material particles from the cooling gas flow. Preferably, the particle separation device is disposed within the inner drum of the cooling gas removal device, upstream of the cooling gas inlet, along the direction of gas flow. The particle separation device prevents material from entering the inner drum of the cooling gas removal device, thereby preventing clogging of the cooling gas removal device. Preferably, material particles having a size greater than 0.3 mm are separated from the cooling gas flow before the cooling gas enters the inner drum.

[0030] In another embodiment, the particle separation device is configured as a cooling air channel between the cover and the inner barrel, the channel leading to the cooling gas inlet. The particle separation device, in particular the cooling air channel, forms a gas connection between the inner barrel and the cooling area.

[0031] The cover body is preferably arranged upstream of the cooling gas inlet in the flow direction of the material, thereby forming a material-free space around the cooling gas inlet, in particular a cooling air channel. The cover body preferably includes a first lower area, which is in the form of a hollow cylinder and extends coaxially around the inner cylinder. The first area preferably has a constant cross-section, in particular an inner diameter. The first area preferably ends at a height approximately the same as the cooling gas inlet or higher than the height of the cooling gas inlet. After the upper end of the first area, there is, for example, a second area, which is configured as a hollow cone, for example, with its tip facing upward. The inner diameter of the second area preferably narrows from the inner diameter of the first area in the flow direction of the material. The cone angle of the cover body is preferably 15° to 50° relative to the vertical direction, in particular 25° to 35°, more preferably 28°.

[0032] The cooling air channel preferably comprises an annular region between the first region of the cover and a hollow conical region between the second region and the inner barrel. The cooling air channel is particularly configured such that the cooling air is deflected by an angle of 90° to 200°, in particular 120° to 180°, before entering the cooling gas inlet of the inner barrel. A particle separation device in the form of the cooling air channel ensures that only particles smaller than approximately 0.3 mm, if any, in the material to be cooled, are allowed to pass into the inner barrel.

[0033] In another embodiment, the cooling air channel is configured such that the cooling air is deflected by an angle of 90° to 200°, in particular 120° to 180°, preferably 180°. This ensures reliable particle separation.

[0034] In another embodiment, the cooling gas removal device is connected to a heat exchanger for the exhaust gases. The PFR shaft kiln includes, for example, a heat exchanger that is gaseously connected to the exhaust gas outlet and the cooling gas removal device, so that the exhaust gases are heated in countercurrent to the cooling gases. The heat exchanger is, for example, a heat exchanger in the form of a regenerator or a heat exchanger. The heat exchanger is, for example, a plate heat exchanger or a shell-and-tube heat exchanger. The cooling gases discharged from the cooling zone are preferably fed to the heat exchanger for heating the exhaust gases. Before the exhaust gases are introduced into the combustion zone of the connecting channel and / or the regenerator shaft, the exhaust gases removed via the exhaust gas outlet are preferably heated in countercurrent to the removed cooling gases. The exhaust gases are preferably heated by the heat exchanger to a temperature of 400°C to 800°C, particularly preferably 600°C.

[0035] The present invention also relates to a method for burning a material, such as carbonate rock, in a co-current / countercurrent regenerative shaft kiln having two shafts, which are operated alternately as a combustion shaft and a regenerative shaft and are connected to one another by connecting lines. The material flows through a material inlet into a preheating zone for preheating the material, a combustion zone for burning the material, and a cooling zone for cooling the material, to a material outlet. Cooling gas is fed into the cooling zone, and cooling gas heated in the cooling zone is discharged from the cooling zone of the shaft via a cooling gas removal device. The combustion zone is gas-connected to the connecting lines. The material exiting the combustion zone is post-calcined in a post-calcination zone downstream of the combustion zone in the direction of material flow at an air temperature of 800° C. to 1100° C., in particular 900° C. to 1000° C., preferably approximately 850° C. to 950° C.

[0036] The combustion zone is gaseously connected to the connecting line, in particular via a flow channel. The material leaving the combustion zone is preferably post-calcined in a post-calcination zone located downstream of the flow channel in the direction of material flow. The post-calcination zone is preferably located immediately after the combustion zone, so that the material is post-calcined in the post-calcination zone immediately following the combustion zone.

[0037] The embodiments and advantages described with reference to the co-current / counter-current regenerative shaft kiln also apply in a corresponding manner to this method.

[0038] In one embodiment, the cooling air is introduced into the cooling gas removal device at a temperature below 900°C, in particular, between 700°C and 850°C, preferably between 725°C and 800°C. The PFR shaft kiln is preferably configured and adapted so that the temperature of the cooling air discharged from the shaft via the cooling gas removal device is below 900°C, in particular, between 700°C and 850°C, preferably between 725°C and 800°C. In another embodiment, the cooling gas discharged from the cooling zone is fed to a heat exchanger for heating the exhaust gas, wherein the cooling gas removal device is preferably connected to the heat exchanger so that the removed cooling air is fed to the heat exchanger at a temperature below 900°C, in particular, between 700°C and 850°C, preferably between 725°C and 800°C. This reliably prevents caking and fouling of the heat exchanger and ensures optimal operation and heat exchange with the exhaust gas.

[0039] In another embodiment, the cooling gas content in the post-calcination zone is set at 0.5% to 10%, particularly 1% to 8%, and preferably 2% to 6%. The cooling gas entering the post-calcination zone is preferably a diversion gas of the cooling gas that is unavoidable from a process engineering perspective. The diversion gas is preferably low enough to be negligible. This almost completely prevents recarbonization of the material.

[0040] In another embodiment, the fuel gas is deflected in the post-calcination zone by an angle of 90° to 180°, preferably 120° to 150°. The post-calcination zone is preferably configured and adapted to deflect the fuel gas by an angle of 90° to 180°, preferably 120° to 150°. The deflection of the fuel gas is preferably performed only in the post-calcination zone and not in the combustion zone, the cooling zone, or the gas separation zone. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Hereinafter, the present invention will be described in more detail by way of several exemplary embodiments with reference to the accompanying drawings.

[0042] Figure 1 A schematic cross-sectional view of a PFR shaft kiln is shown with a perspective view of a cooling gas removal device according to an exemplary embodiment.

[0043] Figure 2 Shown according to Figure 1 A schematic cross-sectional view of an exemplary embodiment of a PFR shaft kiln.

[0044] Figure 3a A schematic cross-sectional view of a PFR shaft kiln according to another exemplary embodiment is shown.

[0045] Figure 3b A schematic cross-sectional view of a subsection of a PFR shaft kiln according to another exemplary embodiment is shown.

[0046] Figure 4a -c shows a PFR shaft kiln according to another exemplary embodiment. Figure 3a Schematic cross-section diagram in the cross-section plane.

[0047] Figure 5 Shown according to Figure 1 3 , a schematic cross-sectional view of a PFR shaft kiln. DETAILED DESCRIPTION

[0048] Figure 1 and Figure 2 The PFR shaft kiln 1 is shown in each case, which has two parallel and vertically oriented shafts 2. The shafts 2 of the PFR shaft kilns 1 are essentially identical in structure, so that Figure 1 Only one of the shafts 2 is designated by a reference numeral, and for simplicity, only one of the shafts 2 will be described below. Each shaft 2 has a corresponding material inlet 3 for feeding the material to be combusted into the corresponding shaft 2 of the PFR shaft kiln 1. The material to be combusted is specifically limestone and / or dolomite, and its particle size is preferably between 10 mm and 200 mm, more preferably between 15 mm and 120 mm, and most preferably between 30 mm and 100 mm. For example, the material inlet 3 is positioned at the upper end of the corresponding shaft 2, allowing the material to fall into the shaft 2 through the material inlet 3 under the action of gravity. The material inlet 3 can, for example, take the form of an upper opening in the shaft 2, specifically a sluice 3, and preferably extends across the entire cross-section or a portion of the cross-section of the shaft 2. The material inlet, in the form of a sluice 3, is preferably configured to allow only the raw material to be combusted to enter the shaft 2, while preventing the entry of ambient air. The sluice 3 is preferably configured to airtightly isolate the shaft 2 from the environment while allowing solids, such as the material to be combusted, to enter the shaft.

[0049] The upper end of each shaft 2 also has a firing gas inlet 12 for feeding firing gas for firing fuel. The firing gas is, for example, dust-removed exhaust gas from at least one shaft 2, and the exhaust gas is preferably rich in oxygen. In addition, each shaft 2 also has an exhaust gas outlet 6 for discharging exhaust gas from the corresponding shaft 2. For example, each exhaust gas outlet 6 and firing gas inlet 12 are equipped with corresponding control elements. Control elements (such as adjustable volume compressors) can preferably be used to adjust the amount of firing gas in the corresponding firing gas inlet 12 and the amount of exhaust gas removed through the corresponding exhaust gas outlet 6. The firing gas inlet 12 and the exhaust gas outlet 6 are, for example, arranged at the same height and are particularly located in the preheating zone 21 of the corresponding shaft 2.

[0050] The lower end of the shaft 2 is provided with a material outlet 40 for discharging the combustion material. The material outlet 40 is, for example, a gate associated with the material inlet 3.

[0051] The combustion material is directed, for example, to an outlet hopper 25 adjacent to the material outlet 40 of the shaft 2. For example, the outlet hopper 25 is funnel-shaped. The outlet hopper 25 preferably has a cooling gas inlet 23 for feeding cooling gas into the corresponding shaft 2. The cooling gas is preferably introduced into the cooling gas inlet by a compressor (not shown).

[0052] During operation of the PFR shaft kiln 1, the material to be combusted flows from top to bottom through the corresponding shaft 2, while cooling air flows from bottom to top through the corresponding shaft 2, partially countercurrent to the material. Kiln exhaust gas is discharged from the shaft 2 via the exhaust gas outlet 6. The CO2 content of the exhaust gas discharged from the shaft 2 is preferably at least 80%, in particular 90% to 99%, and preferably about 95%.

[0053] The preheating zone 21 of each shaft 2 is adjacent to the material inlet 3 and the combustion gas inlet 12 in the direction of material flow. The material and combustion gas are preferably preheated to approximately 700°C in the preheating zone 21. Each shaft 2 is preferably filled with the material to be combusted. The material is preferably supplied to each shaft 2 above the preheating zone 21. At least a portion of the preheating zone 21 and the portion of each shaft 2 adjacent thereto in the direction of material flow are surrounded, for example, by a refractory lining.

[0054] FIG3 shows in detail the Figure 1 and Figure 2 A PFR shaft kiln is provided, wherein a plurality of lances 10 are optionally arranged in the preheating zone 21, and each lance serves as an inlet for fuel (e.g., fuel gas, oil, or ground solid fuel). The PFR shaft kiln 1 includes, for example, a cooling device for cooling the lances 10. The cooling device comprises, for example, a plurality of annular cooling air ducts extending in a circular pattern around the shaft region in which the lances 10 are located. The cooling air for cooling the lances 10 preferably flows through the annular cooling air ducts. The lances 10 are preferably cooled by exhaust gas discharged through an exhaust gas outlet 6. The exhaust gas outlet 6 is preferably connected to the lances 10 for directing the exhaust gas to the lances 10.

[0055] A plurality of (e.g., more than twelve) lances 10 are preferably arranged in each shaft 2 at substantially uniform distances from one another. For example, the lances 10 are L-shaped and preferably extend horizontally into the respective shaft 2 and vertically (in particular, in the direction of material flow) into the shaft 2. The ends of the lances 10 of each shaft 2 are preferably all arranged at the same height. Preferably, the plane in which the lance ends are arranged is in each case the lower end of the respective preheating zone 21. The burner lances 10 are preferably connected to a fuel line (not shown) for supplying fuel to the burner lances 10. The fuel line is, for example, at least partially in the form of an annular line that extends circumferentially around the respective shaft 2. Preferably, each shaft 2 has a fuel line that is assigned to each burner lance 10 of that shaft 2 and, in particular, has corresponding control elements for regulating the amount of fuel supplied to the burner lances 10.

[0056] Preheating zone 21 adjoins combustion zone 20 along the material flow direction. In combustion zone 20, the fuel is burned, and the preheated material is combusted at a temperature of approximately 1000°C. PFR shaft kiln 1 also has connecting line 19 for gaseous connection of the two shafts 2. Specifically, connecting line 19 is free of material to be combusted.

[0057] The PFR shaft furnace 1 preferably has, in the flow direction of the material, a preheating zone 21 for preheating the material, a combustion zone 20 for burning the material, a post-calcining zone 9 for post-calcining the material, a gas separation zone 14 for gas separation between the cooling zone, the combustion zone and the post-calcining zone, and a cooling zone 22 for cooling the material.

[0058] Figure 1-Figure 5 A PFR shaft kiln 1 is shown, for example, with a circular shaft cross section. However, the shaft cross section may have a different geometrical profile, for example circular, semicircular, elliptical, square or polygonal. The combustion zone 20 extends, for example, in a shaft section of substantially constant or increasing cross section.

[0059] The combustion zone 20 is preferably configured so that the fuel gas extends in said area parallel to the shaft axis. The combustion zone 20 is preferably adjacent to the post-calcination zone 9 in the flow direction of the material, for example, the cross section of the post-calcination zone 9 in its upper area is larger than that of the combustion zone 20, wherein the cross section of the post-calcination zone 9 decreases in particular along the flow direction of the material. The combustion zone 20 preferably extends with its lower area to the upper area of ​​the post-calcination zone 9, thereby forming an annular channel 18 between the two shaft sections. The annular channel 18 preferably forms a material-free space in which no material to be burned is provided. The annular channel 18 preferably extends circumferentially around the lower area of ​​the combustion zone 20. For example, Figure 1 The shaft 2 in FIG. 4 has corresponding annular channels 18 , which are each connected to a connecting line 19 .

[0060] The post-calcination zone 9 preferably comprises a shaft region with a narrowed cross section along the flow direction of the material. Preferably, the post-calcination zone 9 extends from the annular channel 18 along the flow direction of the material to a shaft region with a constant cross section.

[0061] The gas separation zone 14 is arranged between the cooling zones 22 in the post-calcining zone 9 and is preferably used to separate gases from the cooling zone 22, the combustion zone 20, and the post-calcining zone 9. Preferably, the gas separation zone 14 is immediately downstream of the post-calcining zone 9 in the flow direction of the material, wherein the cooling zone 22 is particularly immediately downstream of the gas separation zone 14. The gas separation zone 14 is particularly arranged in a vertical shaft section having a substantially constant cross section.

[0062] The cooling zone 22 preferably extends to the discharge device 41 and is arranged in particular in a shaft section which has a substantially constant cross section or which narrows downwards.

[0063] A discharge device 41 is preferably provided at the material outlet end of each shaft 2. The discharge device 41 comprises, for example, a horizontal plate, preferably a discharge table, which allows the material to pass laterally between the discharge table and the shell wall of the PFR shaft kiln. The discharge device 41 is preferably designed as a sliding table, a rotating disk, or a table with a movable scraper. This allows the material to be combusted to pass through the shaft 2 at a uniform rate. For example, the discharge device 41 further comprises an outlet funnel 25, which is adjacent to the discharge table and has a material outlet 40 mounted at its lower end.

[0064] During operation of the PFR shaft kiln 1, one shaft 2 is always active, while the other shaft 2 is inactive. The active shaft 2 is called the combustion shaft, and the inactive shaft 2 is called the regenerative shaft. The PFR shaft kiln 1 operates in a cyclical manner, with a typical number of cycles, for example, ranging from 75 to 150 per day. After the cycle period, the function of the shaft 2 is switched. This process is repeated continuously. Material, such as limestone or dolomite, is alternately supplied to the shaft 2 via the material inlet 3. In the active shaft 2 operating as the combustion shaft, fuel is introduced into the combustion shaft 2 via the burner lances 10. The material to be combusted is heated to a temperature of approximately 700°C in the preheating zone 21 of the combustion shaft.

[0065] During operation of the PFR shaft kiln 1 , in both the combustion shaft 2 and the regenerative shaft 2 , the cooling gas flows through the cooling zone 22 in countercurrent to the material to be cooled and is preferably completely discharged from the shaft 2 via the cooling gas outlet 29 , so that preferably no cooling gas flows from the cooling zone 22 into the combustion zone 20 .

[0066] In the shaft 2 serving as the combustion shaft, combustion gas flows through the combustion gas inlet 12 and flows co-currently with the material in the combustion zone 20. From the combustion zone 20, the fuel gas flows into the post-calcination zone 9, where it is deflected and ultimately flows into the material-free space configured as an annular channel 18. From the material-free space 18, the gas flows through the connecting pipe 19 into the shaft 2 serving as the heat storage shaft. Within the heat storage shaft, the gas flows from the connecting pipe 19 and the material-free space 18 of the heat storage shaft into the post-calcination zone 9, where it is deflected and ultimately flows counter-currently through the combustion zone 20 into the preheating zone 21, leaving the heat storage shaft through the heat storage shaft's exhaust gas outlet 6. The exhaust gas discharged from the shaft 2 preferably has a temperature of 60°C to 160°C, preferably 100°C.

[0067] The exhaust gas is preferably passed into an exhaust gas duct immediately following the exhaust gas outlet 6. The exhaust gas duct optionally includes an exhaust gas filter for filtering particles, particularly dust, from the exhaust gas, particularly downstream of the exhaust gas outlet 6 in the direction of exhaust gas flow. A portion of the exhaust gas is preferably passed to the fuel gas inlet 12 in the fuel gas duct. The exhaust gas is preferably supplied only to the firing gas inlet 12 of the shaft 2, which is operated as a combustion shaft. The fuel gas duct is particularly connected to the oxidant duct, so that an oxidant (preferably pure oxygen) is introduced into the fuel gas duct and then, together with the exhaust gas, into the shaft 2 through the fuel gas inlet 12. It is also conceivable that the oxidant introduced into the firing gas duct 4 is an oxygen-enriched gas having an oxygen content of at least 70% to 95%, preferably 90%. It is also conceivable that a portion of the exhaust gas is supplied to the burner lances. The portion of the exhaust gas not circulated to the fuel gas inlet 12 is optionally supplied to the connecting line 19 or the burner lances. The exhaust gas duct optionally includes a heat exchanger for heating the exhaust gas. The heat exchanger is, for example, in the form of a heat exchanger in which the exhaust gas is heated in countercurrent to the removed cooling gas, while the cooling gas is cooled. The heat exchanger is connected in particular via cooling gas removal lines to the cooling gas outlets 29 of the two shafts 2, so that the exhaust gas is preferably heated in the heat exchanger in countercurrent to the removed cooling gas.

[0068] Preferably, part of the offgas is diverted and discharged. Preferably, all of the CO 2 produced by calcination and combustion, and optionally the water produced by combustion, is discharged from the PFR shaft kiln 1 .

[0069] Each cooling zone 22 has a cooling gas removal device 17 with a corresponding cooling gas outlet 29 arranged therein. Cooling gas removal device 17 includes an inner drum 26 that extends at least partially from cooling zone 22 to post-calcination zone 9 and gas separation zone 14 and is connected to cooling gas outlet 29. Inner drum 26 extends, for example, from discharge device 41 through cooling zone 22 and gas separation zone 14 to post-calcination zone 9, up to the level of connecting line 19. To cool inner drum 26, its outer wall preferably has a plurality of cooling channels 7 arranged therein, which are connected to cooling air ducts for conducting cooling air. Inner drum 26 of cooling gas removal device 17 includes cooling gas outlet 29, which is configured as a duct and extends centrally downward from inner drum 26, through discharge device 41, and then radially outward through discharge funnel 25 and shaft wall 31. It is used to direct cooling gas from inner drum 26 and out of shaft 2.

[0070] The inner barrel 26 is preferably open at the top and has a cooling gas inlet 30 at its upper end for feeding cooling gas from the cooling zone 22 into the inner barrel 26. The inner barrel 26 is preferably arranged coaxially with the shaft 2 within the cooling zone 22 and includes, for example, a refractory lining 8, whose wall thickness increases, particularly in the direction of material flow. This causes the inner diameter of the cooling zone, configured as an annular space, to increase in the direction of material flow. Above the inner barrel 26, and to prevent material from entering the cooling gas inlet 30, the cooling gas removal device 17 has a cover 27. The cover 27 is arranged upstream of the cooling gas inlet 30 in the direction of material flow, thereby forming a material-free space around the cooling gas inlet 30, specifically the cooling air channel 15. The cooling air channel 15 is arranged between the cover 27 and the inner barrel 26.

[0071] For example, the cover 27 includes a first, lower region 16 in the form of a hollow cylinder that extends coaxially around the inner barrel 26. The first region 16 preferably has a constant cross-section, particularly an inner diameter. The first region preferably terminates at a height approximately equal to or higher than the cooling gas inlet 30. Following the upper end of the first region 16 is a second region 28, which is configured, for example, as a hollow cone with an upward-pointing tip. The inner diameter of the second region preferably narrows from the inner diameter of the first region in a direction countercurrent to the flow of the material. The first and second regions 16, 28 form, for example, a single-piece cover 27. The cooling air passage 15 preferably includes an annular region between the first region 16 of the cover 27 and a hollow conical region between the second region 28 and the inner barrel 26. The cooling air passage 15 is particularly configured so that the cooling air is deflected by an angle of 90° to 200°, particularly 120° to 180°, before entering the cooling gas inlet 30 of the inner barrel 26. Therefore, cooling air passage 15 functions as a particle separation chamber, allowing only a minimal amount (if any) of particles in the material to be cooled to enter inner barrel 26. Cooling air passage 15 is preferably configured and adjusted so that only particles with diameters less than 0.4 mm to 0.5 mm, particularly less than 0.3 mm, enter the interior of inner barrel 26. The flow rate within cooling air passage 15 is specifically set so that only particles with diameters less than 0.4 mm to 0.5 mm, particularly less than 0.3 mm, enter the interior of inner barrel 26. The tip of cover 27 is preferably spaced apart from the lower end of combustion zone 20, with the spacing being approximately 0.5 to 1.5 times the length Ln of post-calcination zone 9. It is also conceivable to arrange tip 28 of the cover at the level of the lower end of combustion zone 20.

[0072] The cover 27 has, for example, a plurality of cooling channels 7 which extend along the cover wall and are used to guide a cooling fluid (preferably cooling air). The cover 27 is preferably formed at least partially from a refractory material.

[0073] Figure 4a Shown according to Figure 3a The cross section through the shaft 2 in the section AA is located at the level of the connecting channel 19 and the annular channel 18. The annular channel has a preferably constant inner diameter D5.

[0074] Figure 4b Shown according to Figure 3a The cross section through the shaft 2 in section BB is shown. Preferably, the cover 27, in particular the second region 28, is attached to the inner barrel 26 via radial struts 33. The cooling gas removal device 17 has, for example, four struts 33 that are evenly spaced apart from one another in the circumferential direction. The cooling gas channel 7 also extends through the struts 33.

[0075] The cooling gas removal device 17 preferably comprises a plurality of support elements 38 arranged such as Figure 1 and Figure 2 The cooling zone 22 is shown. A support element 38 extends, for example, from the bottom of the cooling zone 22 , in particular from the discharge device 41 , to the cover 27 , wherein the cover 27 is supported in particular on the support element 38 . Figure 4c Shown according to Figure 3a FIG. 1 shows a cross section through the shaft 2 in a cross section CC, wherein in the exemplary embodiment four support elements 38 are arranged, which are preferably evenly spaced apart from one another in the circumferential direction and each of which optionally comprises at least one cooling channel 7 for guiding cooling gas through the support element 38. The configuration of all support elements 38 is preferably identical. The outer diameter of the support elements 38 increases in particular in the flow direction of the material.

[0076] The cooling gas inlet 30 is preferably located above the cooling gas outlet 29 in the cooling zone 22. During operation of the PFR shaft kiln 1, cooling gas flows upward from the bottom through the cooling zone 22 and into the cooling gas inlet 30, entering the inner barrel 26 of the cooling gas removal device 17. Preferably, all cooling gas introduced into the cooling zone 22 flows into the cooling gas removal device 17 through the cooling gas inlet 30, so that no cooling gas enters the post-calcination zone 9 and the combustion zone 20. The cooling air outlet 29 of the inner barrel 26 is preferably located below the cooling zone 22. Specifically, cooling gas flows downward from the cooling gas inlet 30 in the inner barrel 26 to the cooling gas outlet 29.

[0077] The post-calcination zone 9, the gas separation zone 14, and the cooling zone 22 are preferably configured as an annular space surrounding the cooling gas removal device 17, wherein the annular space each has an outer diameter and an inner diameter.

[0078] The post-calcination zone 9 is preferably formed between the cover 27 of the cooling gas removal device 17 and the shaft wall 31. In particular, the post-calcination zone 9 is formed only between the upper region 28 of the cover 27 and the shaft wall 31. The post-calcination zone 9 preferably has a length Ln in the direction of material flow, wherein the cooling zone 22 has an outer diameter D1, and wherein the ratio of the length Ln of the post-calcination zone 9 to the outer diameter D1 of the cooling zone 22 (Ln / D1) is, for example, 0.4 to 0.8, in particular 0.5 to 0.6. The annular channel 18 preferably has an outer diameter D5, wherein the ratio of the length Ln of the post-calcination zone 9 to the outer diameter D5 of the annular channel 18 (Ln / D5) is, for example, 0.3 to 0.7, preferably 0.4 to 0.6, in particular 0.5.

[0079] In the post-calcination zone 9, an air temperature of 900°C to 1100°C, particularly 850°C to 1000°C, and / or a CO₂ content of at least 90%, particularly at least 98%, is preferably set. At these temperatures, the combustible material that was not completely calcined in the combustion zone 20 is post-calcined, allowing the combustible material to be post-calcined even in a gas flow with a very high CO₂ content, with little, if any, recarbonization, thereby producing good lime quality. The post-calcination zone 9 is preferably configured so that the fuel gas is deflected by an angle of, in particular, 90° to 180°, preferably 120° to 150°.

[0080] In the post-calcination zone, the angle W1 between the shaft wall 31 and the vertical direction is preferably 0° to 30°, particularly 5° to 20°, and preferably 10°. The cone angle W2 between the second tapered region 28 of the cover 27 and the vertical direction is preferably 15° to 50°, particularly 25° to 35°, and preferably 28°.

[0081] The length Lg of the gas separation zone 14 preferably extends in the direction of material flow. The ratio of the inner diameter D2 of the gas separation zone 14 to the outer diameter D1 of the cooling zone (D2 / D1) is, for example, particularly 0.4 to 0.9, preferably 0.5 to 0.8, and particularly preferably 0.7. The outer diameter of the gas separation zone preferably corresponds to the outer diameter D1 of the cooling zone 22. The ratio of the length Lg of the gas separation zone 14 to the outer diameter D1 of the cooling zone 22 is particularly 0 to 1, preferably 0.3.

[0082] For example, the outer diameter of cooling zone 22 increases along the flow direction of the material, particularly until the material is discharged. The upper end of cooling zone 22 preferably has an outer diameter D1, and the lower end preferably has an outer diameter D6, wherein the ratio D6 / D1 of the lower end outer diameter to the upper end outer diameter is, for example, 0.8 to 1.2, preferably 1.05. This ratio ensures that the material can descend easily and evenly in cooling zone 22 under the action of gravity and be easily discharged through discharge device 41. For example, the inner diameter of cooling zone 22 increases along the flow direction of the material, particularly until the material is discharged. The upper end of cooling zone 22 preferably has an inner diameter D4, and the lower end preferably has an inner diameter D7, wherein the ratio D7 / D4 of the lower end inner diameter to the upper end inner diameter is, for example, 1 to 4, preferably 2 to 3. This ratio also ensures that the material descends evenly in cooling zone 22.

[0083] The cooling gas is preferably removed from the cooling zone 22 via the cooling gas removal device 17 at a temperature of 900°C to 650°C, particularly 700°C to 750°C, and preferably 725°C. The PFR shaft kiln 1 preferably has a heat exchanger connected to the cooling gas removal device 17 for supplying the removed cooling gas. This prevents dust from adhering to the inner walls of the cooling gas removal device 17 and to the downstream heat exchanger. The cooling gas is preferably supplied to the heat exchanger at a temperature below 750°C, thereby enabling cost-effective operation of the heat exchanger. Another advantage is that the length Lk of the cooling zone 22 can be shortened, thereby making it more cost-effective to supply large amounts of cooling air.

[0084] use Figure 1 The PFR shaft kiln 1 shown in FIG4 produces highly reactive lime and a process gas with a CO2 content exceeding 90% (on a dry basis). This process waste gas can be liquefied and stored with relatively little complexity. For example, the liquefied process waste gas can be fed to subsequent process steps or stored. Alternatively, the PFR shaft kiln can also be used to produce waste gas with a lower CO2 content, for example, 45% for soda production, 35% for sugar production, or 30% for precipitated calcium carbonate production.

[0085] Figure 5 Shown Figure 1 3 shows a schematic diagram of a PFR shaft kiln 1, in which the flow of gas streams inside the PFR shaft kiln is shown. For example, the left shaft is operated as a combustion shaft and the right shaft is operated as a regenerative shaft. Figure 5 It is shown that a deflection of the gas flow is achieved in the post-calcination zone 9 .

[0086] Reference Mark List

[0087] 1 PFR shaft kiln

[0088] 2 Shaft

[0089] 3 Material inlet / gate

[0090] 4 Firing gas pipeline

[0091] 6 Exhaust gas outlet

[0092] 7 Cooling channels

[0093] 8. Refractory lining

[0094] 9 Post-calcination area

[0095] 10 Burner gun

[0096] 11 Cooling gas removal pipe

[0097] 12 Firing gas inlet

[0098] 14 Gas Separation Zone

[0099] 15 Cooling air channel

[0100] 16. First area of ​​the cover

[0101] 17 Cooling gas removal device

[0102] 18 ring pipes / no material space

[0103] 19 Connecting pipes

[0104] 20 Burning Zone

[0105] 21 Preheating Zone

[0106] 22 Cooling Zone

[0107] 23 Cooling gas inlet

[0108] 24 Another connecting pipe of cooling zone

[0109] 25 outlet funnel

[0110] 26 inner tube

[0111] 27 Cover

[0112] 28. Second area of ​​the cover

[0113] 29 Cooling gas outlet

[0114] 30 Cooling gas inlet

[0115] 31 Shaft Wall

[0116] 32 Cooling device

[0117] 33 Pillars

[0118] 38 Support elements

[0119] 40 Material outlet / gate

[0120] 41 Discharge device

[0121] Ln Length of post-calcination zone

[0122] Lg Length of the gas separation zone

[0123] Lk Length of cooling zone

[0124] D1 Outer diameter of cooling zone, upper end

[0125] D2 Inner diameter of the gas separation zone

[0126] D3 Outer diameter of cooling air passage

[0127] D4 Inner diameter of cooling zone, upper end

[0128] D5 outer diameter of the annular channel

[0129] D6 Outer diameter of cooling zone, lower end

[0130] D7 Inner diameter of cooling zone, lower end

Claims

1. A co-current-countercurrent regenerative shaft kiln (1) for burning and cooling materials such as carbonate rocks, comprising two shafts (2) which can be used alternately as a combustion shaft and a regenerative shaft and are connected to each other via a connecting pipe (2). in, Along the flow direction of the material, each shaft (2) includes a preheating zone (21) for preheating the material, a combustion zone (20) for burning the material, and a cooling zone (22) for cooling the material; as well as wherein the cooling zone (22) comprises a cooling gas inlet (23) for feeding cooling gas into the cooling zone (22) and a cooling gas removal device (17) for discharging cooling gas from the shaft (2), It is characterized by A post-calcination zone (9) is configured downstream of the combustion zone (20) along the flow direction of the material, and the post-calcination zone is configured and adapted so that it post-calcines the material leaving the combustion zone (20) at an air temperature of 800°C to 1100°C, in particular 900°C to 1000°C, preferably about 850°C to 950°C, wherein the post-calcination zone (9) has a length (Ln) extending along the flow direction of the material, wherein the cooling zone (22) is configured as an annular space surrounding the cooling gas removal device (17) and has an outer diameter (D1), and wherein the ratio (Ln / D1) of the length (Ln) of the post-calcination zone (9) to the outer diameter (D1) of the cooling zone is 0.4 to 0.8, in particular 0.5 to 0.7, preferably 0.

6.

2. The downstream-countercurrent regenerative shaft kiln (1) according to claim 1, wherein: The post-calcination zone (9) is configured at least partially as an annular space between the cooling gas removal device (17) and the shaft wall (31).

3. The co-current-countercurrent regenerative shaft kiln (1) according to any one of the preceding claims, wherein: A gas separation zone (14) for separating the cooling gas and the fuel gas is arranged between the post-calcination zone (9) and the cooling zone (22).

4. The co-current-countercurrent regenerative shaft kiln (1) according to any one of the preceding claims, wherein: The post-calcination zone (9) has a length (Ln) extending in the flow direction of the material, and wherein the flow channel (18) is configured as an annular space without material and has an outer diameter (D5), and wherein the ratio (Ln / D5) of the length (Ln) of the post-calcination zone (9) to the outer diameter (D5) of the flow channel (18) is 0.3 to 0.7, preferably 0.4 to 0.6, and in particular 0.

5.

5. The co-current-countercurrent regenerative shaft kiln (1) according to any one of the preceding claims, wherein: The outer diameter of the post-calcination zone (9) decreases at an angle W1 of 0° to 30°, particularly 5° to 20°, preferably 10° relative to the vertical direction along the flow direction of the material, and / or the inner diameter of the post-calcination zone (9) decreases at an angle W2 of 15° to 50°, particularly 25° to 35°, preferably 28° relative to the vertical direction along the flow direction of the material.

6. The co-current-countercurrent regenerative shaft kiln (1) according to any one of the preceding claims, wherein: The cooling gas removal device (17) comprises an inner cylinder (26) having a cooling gas inlet (30) and a cover (27) arranged in the cooling zone (22), wherein the cover (27) is arranged upstream of the cooling gas inlet (30) along the flow direction of the material.

7. The co-current-countercurrent regenerative shaft kiln (1) according to any one of the preceding claims, wherein: The cooling gas removal device (17) includes a particle separation device for separating material particles from the cooling gas flow.

8. The co-current-countercurrent regenerative shaft kiln (1) according to claims 6 and 7, wherein: The particle separation device is configured as a cooling air passage (15) located between the cover (27) and the inner cylinder (26), the cooling air passage leading to the cooling gas inlet (30).

9. The downstream-countercurrent regenerative shaft kiln (1) according to claim 8, wherein: The cooling air channel (15) is configured such that the cooling air is deflected at an angle of 90° to 200°, in particular 120° to 180°.

10. The co-current-countercurrent regenerative shaft kiln (1) according to any one of the preceding claims, wherein: The cooling gas removal device (17) is connected to a heat exchanger (43) for heating the exhaust gas.

11. A method for burning a material such as carbonate rock in a co-current / counter-current regenerative shaft kiln (1), the co-current / counter-current regenerative shaft kiln having two shafts (2) which are used alternately as combustion shafts and regenerative shafts and are connected to each other via a connecting line (19), wherein: The material flows through the material inlet (3) into the preheating zone (21) for preheating the material, the combustion zone (20) for burning the material, the cooling zone (22) for cooling the material, and finally into the material outlet (40). wherein cooling gas is fed into the cooling zone, and wherein the cooling gas heated in the cooling zone (22) is discharged from the cooling zone (22) of the shaft (2) via a cooling gas removal device (17), and wherein each vertical shaft (2) is gas-connected to the connecting pipeline (19); It is characterized by: The material leaving the combustion zone (20) is post-calcined in a post-calcination zone (9) downstream of the combustion zone (20) along the flow direction of the material at an air temperature of 800°C to 1100°C, in particular 900°C to 1000°C, preferably about 850°C to 950°C.

12. The method according to claim 11, wherein The cooling air is introduced into the cooling gas removal device (17) at a temperature below 900°C, in particular 700°C to 850°C, preferably 725°C to 800°C.

13. The method according to claim 11 or 12, wherein: A cooling gas content of 0.5% to 10%, in particular 1% to 8%, preferably 2% to 6%, is set in the post-calcination zone (9).

14. The method according to any one of claims 11 to 13, wherein The fuel gas is deflected in the post-calcination zone (9) at an angle of 90° to 180°, preferably 120° to 150°.

15. The method according to claim 11, wherein The cooling gas discharged from the cooling zone (22) is supplied to a heat exchanger (43) to heat the exhaust gas.

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