Parallel-flow regenerative shaft kiln and method for burning carbonate rock

Description

[0001] The invention relates to a direct-current counter-current regenerative shaft furnace (DGR shaft furnace) and a method for firing and cooling material, such as carbonate rocks, using a DGR shaft furnace.

[0002] The firing of carbonate rock in a GGR shaft kiln has been known for about 60 years. Such a GGR shaft kiln, known, for example, from DE 10 2021 204 176 A1, has two vertical, parallel shafts that operate cyclically. Firing takes place in only one shaft, the firing shaft, while the other shaft functions as a regeneration shaft. Oxide gas is fed into the firing shaft in co-current flow with the material and fuel. The resulting hot exhaust gases, together with the heated cooling air supplied from below, are routed via the overflow channel into the regeneration shaft. There, the exhaust gases are directed upwards in counter-current flow to the material, preheating it in the process. The material is typically fed into the shaft from above along with the oxidation gas, with fuel being injected into the firing zone. Other examples of known prior art are EP4182622B1 or US4740157A.

[0003] The material to be burned typically passes through a preheating zone in each shaft, followed by a combustion zone where the material is burned, and then a cooling zone where cooling air is supplied to the hot material.

[0004] Furthermore, the demand for environmentally friendly quicklime production is increasing, necessitating compliance with specific CO₂ content requirements in the exhaust gas for subsequent treatment. However, the production of environmentally friendly lime should be as cost-effective as possible and require only minimal modifications to existing plants. Additionally, the operation of the lime kilns should be as energy-efficient as possible. Therefore, the specific energy consumption of a GGR shaft kiln should be minimized, while simultaneously reducing technical complexity, particularly the number of maintenance-intensive components.

[0005] Starting from this, the object of the present invention is to provide a GGR shaft kiln and a method for burning carbonate rock with a GGR shaft kiln, with which lime with a high reactivity is produced with simultaneous CO2 separation from the exhaust gas, wherein the lime production is energy-efficient and cost-effective.

[0006] This problem is solved according to the invention by a device having the features of independent device claim 1 and by a method having the features of independent method claim 15. Advantageous embodiments are described in the dependent claims.

[0007] According to a first aspect, the invention comprises a co-current counter-current regenerative shaft furnace for firing and cooling materials such as carbonate rocks, with two shafts that can be operated alternately as firing shafts and regenerative shafts and are connected to each other by means of a transfer channel. Each shaft has, in the direction of material flow, a preheating zone for preheating the material, a firing zone for firing the material, and a cooling zone for cooling the material. Each shaft has an exhaust gas outlet for releasing exhaust gas from the shaft. The co-current counter-current regenerative shaft furnace has a cooling gas line for conveying cooling gas from the cooling zone to the preheating zone. The cooling gas line is, for example, designed as a bypass line to circumvent the firing zone. In particular, the cooling gas line is arranged parallel to the combustion gases of the firing zone. Each shaft preferably has a cooling gas line.

[0008] Such a cooling gas line offers the advantage that the heated cooling air is supplied to the preheating zone and can thus be used for material preheating. Additional recuperators for heat exchange with the cooling gas and / or the exhaust gas are not necessary. This significantly reduces the energy consumption of the GGR shaft furnace and also decreases its complexity.

[0009] The material to be burned is preferably limestone or dolomite with a grain size of 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 co-current counter-current regenerative shaft furnace has at least two shafts, preferably arranged parallel to each other and vertically. The shafts preferably each have a square, triangular, quadrilateral, rectangular, round, oval, polygonal, semicircular, partial circular, or circular cross-section. The shafts can be operated alternately as a firing shaft and as a regenerative shaft, with each shaft having, in the direction of material flow, a preheating zone for preheating the material, a firing zone for firing the material, and a cooling zone for cooling the material. Each shaft preferably has a material inlet for introducing material to be fired into the shaft, the material inlet being located, in particular, at the upper end of the respective shaft so that the material falls into the shaft by gravity.The material inlet and / or outlet is / are designed, in particular, as an airlock for introducing and / or discharging material into the shaft furnace. A material inlet designed as an airlock is preferably configured such that only the raw material to be burned enters the shaft, but not the ambient air. The airlock also prevents gas from escaping the shaft via the material inlet. Preferably, the airlock is designed to seal the shaft airtight against the environment while allowing solids, such as the material to be burned, to enter the shaft. The combustion zone, preheating zone, and cooling zone preferably refer to the areas of the shaft that are filled with material. Material-free spaces, separated from the material-filled areas of the shaft, for example, by a wall, are preferably not part of the preheating zone, combustion zone, or cooling zone.

[0011] The overflow channel is designed for the gas connection between the two shafts and preferably connects the combustion zones of the shafts. During operation of the GGR shaft kiln, one of the shafts is operated as the combustion shaft and is active, while the other shaft is operated as the regenerative shaft and is passive. The GGR shaft kiln is operated cyclically, with the function of the shafts being exchanged after the cycle time has elapsed. This process is repeated continuously. In the active shaft operated as the combustion shaft, fuel is introduced into the combustion zone via the burner lances. The material to be burned is preferably heated to a temperature of approximately 700°C in the preheating zone of the combustion shaft. In the shaft operated as the combustion shaft, the combustion zone is designed as a co-current combustion zone, with the material to be burned flowing parallel to the gas.Within the combustion shaft, the gas flows from the preheating zone into the combustion zone and then via the overflow channel into the combustion zone and the preheating zone of the regeneration shaft. In the shaft operated as a regeneration shaft, the gas flows counter-currently to the material being burned in the preheating zone and the combustion zone.

[0012] In both the combustion shaft and the regeneration shaft, cooling gas is passed counter-currently to the material being cooled through the cooling zone and preferably completely discharged from the cooling zone, particularly from the shaft, via the cooling gas line, so that preferably no cooling gas flows into the combustion zone. Preferably, the cooling gas line and / or the cooling gas outlet is arranged such that at least 60%, particularly at least 70%, preferably at least 80% to at least 90% of the cooling gas supplied to the GGR shaft furnace is discharged from the cooling zone, particularly from the shaft, via the cooling gas line. The cooling gas line is preferably arranged separately from the combustion zone, particularly the shaft.In particular, the cooling gas outlet and / or the cooling gas line is arranged and designed such that 85% to 115%, in particular 90% to 110%, preferably 105% of the cooling gas supplied to the GGR shaft furnace is discharged as cooling gas via the cooling gas outlet and the cooling gas line. It is also conceivable that all of the cooling air, or at least more cooling air than, is supplied to the combustion shaft than to the regeneration shaft. This prevents, for example, a portion of the furnace exhaust gas from flowing from the combustion shaft via the lower connecting channel. For example, 60–100% of the cooling air is supplied to the combustion shaft.

[0013] The exhaust gas is preferably discharged exclusively from one shaft, in particular the regeneration shaft. Control devices, such as dampers, fans, or valves, are preferably installed downstream of the exhaust gas outlets, allowing the amount of exhaust gas to be discharged to be adjusted. The discharged exhaust gas is preferably fed to the other shaft, in particular the combustion shaft. Preferably, only a portion of the exhaust gas discharged from the regeneration shaft is fed back into at least one shaft. A portion of the exhaust gas discharged from the regeneration shaft is, for example, discharged from the GGR shaft furnace and, for example, subjected to further treatment, such as sequestration. For example, the exhaust gas discharged from the regeneration shaft is fed to a buffer storage tank and temporarily stored therein. The exhaust gas preferably comprises CO₂ and optionally H₂O.The GGR shaft furnace preferably has a combustion gas inlet for introducing combustion gas into the preheating zone or the combustion zone, wherein the exhaust gas outlet is optionally connected to the combustion gas inlet via an exhaust gas recirculation line.

[0014] Fuel is preferably supplied to the combustion zone and / or preheating zone of the shaft operated as a combustion shaft via a fuel line. Preferably, the fuel is supplied to burner lances located 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 or biomass, or liquid fuels. In the combustion zone, the material is preferably heated to a temperature of approximately 1050°C.

[0015] Each shaft preferably has a plurality of burner lances that extend at least partially through the preheating zone and, in particular, open into the combustion zone of the respective shaft and serve to convey, for example, fuel and / or an oxidizing gas, such as air or oxygen-enriched air or pure oxygen. The GGR shaft furnace preferably has a combustion gas inlet connected to a combustion gas source comprising a combustion gas with an oxygen content of more than 60 vol%, preferably more than 75 vol%, and in particular more than 80 vol% to more than 95 vol% oxygen.

[0016] Each shaft preferably has a cooling gas inlet for introducing cooling gas into the cooling zone, to which a control element is assigned for adjusting the amount of cooling gas supplied at the respective cooling gas inlet. The control elements are set such that a larger quantity of cooling air is supplied to the combustion shaft than to the regeneration shaft. The control element is, for example, a continuously adjustable valve or a flap. The control element is, for example, located upstream of the cooling gas inlet and, in particular, arranged in a cooling gas line connected to the cooling air inlet. Preferably, the control elements are designed and configured such that 70% to 100%, preferably 90%, of the total amount of cooling gas supplied to the GGR shaft furnace is supplied to the combustion shaft.

[0017] Recirculating the exhaust gas into at least one shaft enables the production of highly reactive lime, while simultaneously generating process gas with a CO₂ content of more than 30 vol%, particularly more than 50 vol%, preferably more than 70 vol% or more than 90 vol%, based on dry gas. Such process gas can be liquefied and sequestered with less effort. For example, the liquefied process gas can be fed into further process steps or stored. Alternatively, the GGR shaft kiln described above can also be used to generate exhaust gas with a lower CO₂ content, for example, 40% to 50% for soda production or 30% to 35% based on dry gas for the production of beet sugar or precipitated calcium carbonate.

[0018] According to the inventors' findings, the oxygen-containing cooling gas flows essentially separately from the combustion gas within the shafts, especially within the preheating zone, so that there is only a very slight mixing of the gas flows of the combustion gas and the cooling gas.

[0019] According to a first embodiment, the cooling gas line is arranged either outside or inside the shaft. Preferably, the cooling gas line extends entirely outside the shaft and, in particular, runs parallel to the combustion zone of the respective shaft, especially the regeneration shaft. Optionally, the cooling gas line is arranged entirely inside the shaft and, in particular, is separated from the remaining area of ​​the combustion zone and / or the preheating zone by a separating element, such as a partition wall or a pipe. Preferably, in the case of a GGR shaft furnace with rectangular shaft cross-sections, the cooling gas line is arranged inside the shaft. In particular, the cooling gas line is arranged inside the shaft in a region near the shaft wall opposite the overflow channel.In comparison to known GGR shaft furnaces, the gases in the respective shaft are mixed less intensely, since the cooling gas does not flow through the combustion zone of the regenerative shaft.

[0020] According to a further embodiment, the shaft furnace has a cooling gas outlet for releasing cooling gas from the cooling zone, in particular from the shaft, wherein the cooling gas outlet is arranged within the cooling zone and is connected to the cooling gas line. The cooling gas outlet is preferably designed as an opening in the shaft wall. The cooling gas preferably flows completely out of the respective shaft through the cooling gas outlet, preferably exclusively from the cooling zone of the shaft. For example, the cooling gas outlet is slot-shaped and extends circumferentially, in particular horizontally, in the shaft wall of the cooling zone.

[0021] According to a further embodiment, the shaft furnace has a cooling gas inlet in the preheating zone for introducing cooling gas into the preheating zone, which is connected to the cooling gas line. The cooling gas outlet is connected, in particular via the cooling gas line, to a cooling gas inlet for introducing the cooling gas into the shaft. The cooling gas outlet is preferably located entirely within the cooling zone, with the cooling gas inlet being located within the preheating zone, particularly at the lower end of the preheating zone, of the respective shaft. Preferably, each shaft has one cooling gas outlet and one cooling gas inlet, which are connected to each other via the cooling gas line for conveying the cooling gas from the cooling gas outlet to the cooling gas inlet. In a GGR shaft furnace with a rectangular cross-section, the cooling gas inlet is located, in particular, on the shaft wall opposite the overflow channel.According to the inventors, within the preheating zone of the regenerative shaft, there is only minimal mixing of the cooling gas with the CO2-containing combustion gases from the combustion zone. Therefore, introducing the cooling gas into the preheating zone serves as an additional heat source for preheating the material and ensures energy-efficient furnace operation.

[0022] According to another embodiment, the cooling gas inlet is slot-shaped. For example, in a GGR shaft furnace with round shaft cross-sections, the cooling gas inlet extends circumferentially around the preheating zone, in particular completely around the entire preheating zone. Optionally, in a GGR shaft furnace with rectangular shaft cross-sections, the cooling gas inlet extends horizontally, in particular completely across the width of the shaft wall opposite the overflow channel.

[0023] According to a further embodiment, the shaft furnace has a partition wall arranged within the shaft, which at least partially forms the cooling gas line. The cooling gas line formed by the partition wall preferably extends completely within the shaft. In particular, each shaft has a partition wall. The partition wall preferably extends vertically, from the cooling zone or the combustion zone to the shaft ceiling. In particular, the lower end of the partition wall is arranged at the level of the overflow channel, with the upper end of the partition wall preferably abutting the shaft ceiling in a gas-tight manner. In particular, the partition wall extends over the entire width, and especially the depth, of the respective shaft and is preferably geometrically aligned parallel to the shaft wall opposite the overflow channel.

[0024] According to a further embodiment, the cooling gas outlet for releasing cooling gas from the cooling zone is designed between the partition wall and the inner wall of the shaft. The partition wall preferably forms the cooling gas line together with the inner wall of the shaft, particularly the regeneration shaft. The cooling gas line comprises, for example, approximately 20–40%, preferably approximately 33%, of the volume of the combustion zone and / or the preheating zone. Preferably, the cooling gas line has a combustion gas inlet for introducing oxygen-enriched exhaust gas. The GGR shaft furnace preferably has a further combustion gas inlet in each shaft, through which recirculated and oxygen-enriched exhaust gas is introduced into the combustion shaft outside the cooling gas line.Preferably, according to the inventors' findings, the cooling air flows exclusively along the outer shaft section opposite the overflow channel, so that it is separated from the combustion gas of the combustion zone by the partition wall. This reliably prevents the combustion gases and cooling gases from mixing.

[0025] According to a further embodiment, the shaft furnace has a cooling gas outlet for releasing the cooling gas from the shaft, wherein the cooling gas outlet is arranged in the preheating zone of the shaft. The cooling gas outlet is, for example, located at the upper end of the preheating zone. Preferably, the cooling gas outlet is located in the outer wall of the shaft. In particular, the cooling gas outlet extends completely through the outer wall of the shaft and is located, especially, in the outer wall surrounding the preheating zone or the combustion zone. Preferably, the GGR shaft furnace has a refractory lining that extends, for example, from the cooling zone to the preheating zone, and in particular to a lower region of the preheating zone. The cooling gas outlet is preferably located above the lining or at an upper end region of the lining.The cooling gas outlet is preferably located entirely within the preheating zone or the combustion zone, so that the cooling air flows completely from the cooling zone into the combustion zone. A cooling gas outlet located in the outer wall of the preheating zone or the combustion zone offers a structurally very simple solution for cooling gas extraction. Existing lime kilns can be retrofitted without significant effort.

[0026] Each shaft preferably has at least one exhaust gas outlet, for example, at the upper end of the shaft within the preheating zone. Preferably, the exhaust gas outlet is located above the material column in a material-free area of ​​the preheating zone. Each shaft preferably has at least one cooling gas outlet, wherein preferably only the cooling gas outlet in the shaft operated as a regenerative shaft is open, and the cooling gas outlet of the combustion shaft is gas-tight. The GGR shaft furnace preferably has one or more burner lances arranged such that they open into the combustion zone, wherein the cooling gas outlet is located downstream of at least one of the burner lance openings in the gas flow direction of the regenerative shaft. Preferably, the cooling gas outlet is located downstream of all burner lance openings in the gas flow direction.

[0027] Preferably, each shaft has a cooling gas outlet, with each cooling gas outlet being assigned a control element for adjusting the amount of cooling gas to be discharged via the cooling gas outlet. The control element assigned to the cooling gas outlet of the combustion shaft is closed, so that preferably no cooling gas can be discharged via the cooling gas outlet of the combustion shaft. Preferably, the cooling gas outlet is connected to a cooling gas discharge line located outside the shaft. The control element is preferably connected to the cooling gas outlet via a gas supply line and is particularly located in the cooling gas discharge line. The control element is, for example, a flap or a valve that is continuously adjustable between an open and a closed position.The control element associated with the cooling gas outlet of the regeneration shaft is preferably designed and configured such that 85% to 115%, in particular 90% to 110%, preferably 105% of the cooling gas supplied to the GGR shaft furnace is discharged as cooling gas exhaust via the cooling gas outlet of the regeneration shaft. The cooling gas exhaust line is connected, for example, to the combustion gas inlet, in particular to the exhaust gas recirculation line, to the exhaust gas discharged from the exhaust gas outlet, so that the cooling gas discharged from the cooling gas outlet is fed to the combustion gas inlet, in particular to the combustion zone of the combustion shaft. Advantageously, with such a configuration, no CO₂-containing gas is released into the atmosphere via the cooling gas outlet; instead, the entire exhaust gas is preferably fed to further processing or storage via the exhaust gas outlet.

[0028] The cooling gas outlet is preferably located in a region of the outer wall of the preheating zone or the combustion zone facing away from the overflow channel. The GGR shaft furnace preferably has a direct or indirect overflow channel for directly or indirectly connecting the combustion shaft to the regeneration shaft. For example, the GGR shaft furnace has an annular channel that connects the shafts to each other gas-wise at the same level as the overflow channel. Alternatively, the GGR shaft furnace may not have an annular channel; in this case, the shafts are connected to each other gas-wise directly via the overflow channel. By way of example, the combustion zone and the preheating zone of the shafts have a cross-section that is substantially constant along the length of the shaft.The outer wall of the shafts, projecting radially outwards from the overflow channel, extends exclusively vertically over the entire length of the shaft, particularly over the length of the combustion zone and the cooling zone. The cooling zone preferably has a cross-section that increases in size towards the overflow channel and opens into it. Preferably, the shafts of the GGR shaft furnace are completely filled with material, so that, particularly in the combustion zone and the cooling zone, no material-free annular space is formed at the level of the overflow channel.

[0029] For example, the cooling gas outlet extends horizontally in the outer wall of the shaft. For example, the cooling gas outlet is designed as a horizontal slot. In particular, the cooling gas outlet extends across the entire width of the outer wall of the shaft opposite the overflow channel. For example, the cooling gas outlet comprises a plurality of openings in the shaft's outer wall, which are arranged horizontally next to each other and preferably at the same height. Optionally, the cooling gas outlet is designed as an annular channel. In a GGR shaft furnace with the partition described above, for example, recirculated and oxygen-enriched exhaust gas is introduced via the cooling gas outlet into the cooling gas line between the partition and the shaft wall opposite the overflow channel.

[0030] According to a further embodiment, at least one or more control elements are arranged in the cooling gas line, configured to control / regulate the amount of cooling air flowing from the cooling gas outlet and / or to the cooling gas inlet. These control elements may be, for example, a flap, a fan, or a valve. Preferably, a control device is provided that is connected to the control elements and configured to control / regulate the amount of cooling gas discharged via the cooling gas outlet and / or the amount of cooling gas flowing to the cooling air inlet, particularly depending on a desired CO₂ content in the exhaust gas. Preferably, the control elements are configured such that the cooling gas is supplied exclusively to the regeneration shaft, in particular to the preheating zone of the regeneration shaft, via the cooling gas inlet.

[0031] According to a further embodiment, the overflow channel has a first connecting channel and a second connecting channel, which are arranged parallel to each other in terms of gas flow. Preferably, the connecting channels are arranged separately from each other. The first connecting channel is, for example, arranged above the second connecting channel.

[0032] According to a further embodiment, the first connecting channel is arranged and designed such that only the exhaust gas from the combustion zone can flow into it. According to a further embodiment, the second connecting channel is arranged and designed such that only the cooling gas from the cooling zone can flow into it. This ensures that the cooling gas from the combustion chamber is introduced into the regeneration chamber independently of the combustion gases, reliably preventing the combustion gases from mixing with the cooling gases within the transfer channel.

[0033] The first connecting channel is designed, for example, as a direct connecting channel and the second connecting channel as an indirect connecting channel. The GGR shaft furnace, for example, has an annular channel designed as a material-free space, which is preferably connected to the overflow channel, in particular the first or the second connecting channel, via a gas supply.

[0034] The exhaust gas discharged from the shaft via the exhaust gas outlet preferably has a CO₂ content of at least 70 vol%, particularly at least 85 vol%, and preferably at least 90 to 95 vol%. Optionally, for example in the soda or sugar industries, the exhaust gas has a CO₂ content of 35 to 45 vol%, with in particular no exhaust gas recirculation into the combustion chamber.

[0035] The invention also includes a method for burning material, such as carbonate rocks, in a co-current counter-current regenerative shaft furnace, wherein the embodiments and advantages described with reference to the co-current counter-current regenerative shaft furnace also apply to the method in a procedurally appropriate manner.

[0036] In a process for firing materials such as carbonate rocks in a co-current counter-current regenerative shaft kiln with two shafts, which are operated alternately as firing shafts and regenerative shafts and are connected by a transfer channel, the material flows through a material inlet into a preheating zone for preheating the material, a firing zone for firing the material, and a cooling zone for cooling the material to a material outlet. A cooling gas is introduced into the cooling zone, and exhaust gas is released from one of the shafts via an exhaust gas outlet. The cooling gas is then conveyed from the cooling zone to the preheating zone via a cooling gas line.

[0037] The exhaust gas released from the shaft via the exhaust outlet is preferably fed to the combustion chamber. For example, the exhaust gas is introduced into the preheating zone of the shaft operated as a combustion chamber.

[0038] According to one embodiment, the cooling gas is routed separately from the combustion gases of the combustion zone in the cooling gas line to the preheating zone. Preferably, the cooling gas is routed parallel to the combustion gases of the combustion zone to the preheating zone.

[0039] According to another embodiment, the cooling gas is preferably released exclusively from the regeneration shaft.

[0040] According to a further embodiment, the cooling gas is drawn off from the cooling zone and introduced into the preheating zone. In particular, the cooling gas is introduced into the lower part of the preheating zone, adjacent to the combustion zone.

[0041] According to a further embodiment, the cooling gas introduced into the preheating zone via the cooling gas line is discharged from the preheating zone by means of a cooling gas outlet. In particular, the cooling gas is discharged from the shaft via the cooling gas outlet located at the upper end of the preheating zone. The amount of cooling gas discharged from the regeneration shaft via the cooling gas outlet is preferably adjusted by means of a control device. Preferably, 85% to 115%, in particular 90% to 110%, and preferably 105% of the amount of cooling gas supplied to the GGR shaft furnace is discharged as cooling gas exhaust via the cooling gas outlet.

[0042] With the GGR shaft furnace described above and the method for operating the GGR shaft furnace, a CO₂ content in the exhaust gas of at least 30 vol%, in particular at least 50 vol%, preferably at least 70 vol% to at least 90 vol% is achieved. This enables further processing of the exhaust gas in other industrial processes or storage of the CO₂-containing exhaust gas. Beschreibung der Zeichnungen

[0043] The invention is explained in more detail below with reference to several exemplary embodiments and the accompanying figures. Fig. 1 shows a schematic representation of a GGR shaft furnace in a sectional view according to one embodiment. Figs. 2a and 2b each show a schematic representation of the gas flow path of a GGR shaft furnace in a longitudinal sectional view according to another embodiment. Fig. 3 shows a schematic representation of a GGR shaft furnace in a longitudinal sectional view according to another embodiment. Fig. 4a shows a schematic representation of a GGR shaft furnace in a longitudinal sectional view according to another embodiment. Fig. 4b shows a schematic representation of the gas flow path of a GGR shaft furnace in a cross-sectional view according to another embodiment. Fig. 5a shows a schematic representation of a GGR shaft furnace in a longitudinal sectional view according to another embodiment.Figure 5b shows a schematic representation of the gas flow path of a GGR shaft furnace in a cross-sectional view according to a further embodiment. Figure 6 shows a schematic representation of a GGR shaft furnace in a longitudinal section view according to a further embodiment.

[0044] Fig. 1 Figure 1 shows a GGR shaft furnace 1 with two parallel and vertically aligned shafts 2. The shafts 2 of the GGR shaft furnace 1 are essentially identical in construction, so that in Fig. 1 Only one of the two shafts 2 is fully designated with reference numerals, and for the sake of simplicity, only one of the two shafts 2 is usually described below. Each shaft 2 has a material inlet 3 for introducing material to be fired into the respective shaft 2 of the GGR shaft kiln 1. The material to be fired is, in particular, limestone and / or dolomite, preferably with a grain size of 10 to 200 mm, more preferably 15 to 120 mm, and most preferably 30 to 100 mm. The material inlets 3 are, for example, arranged at the upper end of the respective shaft 2, so that the material falls into the shaft 2 by gravity through the material inlet 3. The material inlet 3 is, for example, designed as an upper opening of the shaft 2 and, in particular, as a sluice gate 3, and preferably extends over the entire or a part of the cross-section of the shaft 2.A material inlet designed as an airlock 3 is preferably configured such that only the raw material to be burned enters the shaft 2, but not the ambient air. Preferably, the airlock 3 is designed to seal the shaft 2 airtight against the environment and to allow the entry of solids, such as the material to be burned, into the shaft.

[0045] Each shaft 2 has a combustion gas inlet 12 at its upper end for introducing combustion gas for the combustion of fuels. The combustion gas is, for example, dedusted exhaust gas from at least one of the shafts 2, optionally enriched with oxygen. Furthermore, each shaft 2 has an exhaust gas outlet 6 for releasing exhaust gases from the respective shaft 2. Each exhaust gas outlet 6 and combustion gas inlet 12 is, for example, assigned a control element. The amount of combustion gas entering the respective combustion gas inlet 12 and the amount of exhaust gas to be discharged via the respective exhaust gas outlet 6 can preferably be adjusted by means of control elements such as a flap, a valve, or a variable-flow compressor.The combustion gas inlet 12 and the exhaust gas outlet 6 are arranged by way of example at the same height level and in particular within the preheating zone 21 of the respective shaft 2.

[0046] At the lower end of shaft 2, a material outlet 40 is arranged for discharging the calcined material. The material outlet 40 is, for example, a lock as described with reference to the material inlet 3. The calcined material is directed, for example, into an outlet hopper 25, to which the material outlet 40 of shaft 2 is connected. The outlet hopper 25 is, for example, funnel-shaped. The outlet hopper 25 preferably has a cooling gas inlet 23 for introducing cooling gas into the respective shaft 2. The cooling gas is preferably directed into the cooling gas inlet 23 by means of a compressor 33.

[0047] Below the material inlet 3 and / or the combustion gas inlet 12, the preheating zone 21 of the respective shaft 2 adjoins it in the direction of material flow. In the preheating zone 21, the material and the combustion gas are preferably preheated to approximately 700°C. Preferably, the respective shaft 2 is filled with material to be incinerated. The material is preferably fed into the respective shaft 2 above the preheating zone 21. At least a portion of the preheating zone 21 and the portion of the respective shaft 2 adjoining it in the direction of material flow are, for example, surrounded by a refractory lining.

[0048] Optionally, a plurality of burner lances 10 are arranged in the preheating zone 21, each serving as an inlet for fuel, such as a fuel gas, oil, or ground solid fuel. Preferably, a plurality, for example twelve or more, of burner lances 10 are arranged in each shaft 2, spaced substantially evenly apart from one another. The burner lances 10 are, for example, L-shaped and preferably extend horizontally into the respective shaft 2 and vertically within the shaft 2, particularly in the direction of material flow. The ends of the burner lances 10 in a shaft 2 are preferably all arranged at the same level. Preferably, the plane on which the lance ends are arranged is the lower end of the respective preheating zone 21. The burner lances 10 are preferably connected to a fuel line 9 for supplying fuel to the burner lances 10.The fuel line 9 is, for example, at least partially configured as a ring line extending circumferentially around the respective shaft 2. Preferably, each shaft 2 has a fuel line 9 assigned to the burner lances 10 of the shaft 2, each of which in particular has a control element for adjusting the amount of fuel supplied to the burner lances 10.

[0049] The combustion zone 20 adjoins the preheating zone 21 in the direction of material flow. The burner lances 10, for example, open into the combustion zone 20. Preferably, the flame of the burner lances 10 extends into the combustion zone 20. In the combustion zone 20, the fuel is burned and the preheated material is fired at a temperature of approximately 1000°C. The combustion of the fuel takes place, for example, with an excess of air relative to stoichiometric combustion. Preferably, complete combustion of the fuel occurs exclusively within the combustion zone 20 of the combustion chamber. It is also conceivable that afterburning of fuel not completely combusted within the combustion zone 20 takes place in a transfer channel and / or the regeneration chamber.

[0050] The GGR shaft furnace 1 further includes, by way of example, a transfer channel 19 for connecting the two shafts 2 to each other for gas supply. The transfer channel 19 includes, by way of example, two connecting channels 19a and 19b. The connecting channels 19a and 19b are arranged, by way of example, parallel and separate from each other. By way of example, the connecting channels 19a and 19b are separated from each other for gas supply by a separating element 13, in particular a horizontal one, such as a partition wall. The shaft furnace 1 includes, by way of example, a first connecting channel 19a, which connects, in particular, directly to the combustion zone 20 and is preferably arranged above a second connecting channel 19b. The first connecting channel 19a is arranged and designed, by way of example, such that only the exhaust gas from the combustion zone 20 can flow into it.Optionally, the first connecting channel 19a and the second connecting channel 19b are each designed as a material-free space containing no combustible material. The second connecting channel 19b is preferably arranged below the first connecting channel 19a and, in particular, directly connected to the cooling zone 22 via flow characteristics. The second connecting channel 19b is, by way of example, arranged and designed such that only the cooling gas from the cooling zone 22 can flow into the second connecting channel 19b.

[0051] In the Fig. 1 An example of a GGR shaft furnace 1 with a transfer channel 19, which exemplarily comprises a first and a second connecting channel 19a, b, is shown. The shaft furnace 1 has, for example, a rectangular shaft cross-section. It is also conceivable that the shafts 2 of the GGR shaft furnace 1 have a triangular, square, rectangular, round, oval, polygonal, semicircular, semicircular, or circular cross-section. The transfer channel 19 forms, for example, a gas connection between the two shafts 2, wherein the cooling gas from the combustion shaft 2a, in particular separately from the fuel gas from the combustion shaft 2b, flows into the transfer channel 19 and subsequently into the regeneration shaft 2b. Preferably, the first connecting channel 19a is designed as a direct connecting channel 19a, wherein the second connecting channel 19b is also designed, by way of example, as a direct connecting channel 19b.

[0052] The combustion zone 20 extends, for example, within a shaft section with a substantially constant cross-section. The shaft section extends, for example, with its lower portion into the upper portion of the cooling zone 22 or directly adjoins it, so that an annular channel, in particular a channel 18, is formed between the combustion zone 20 and the cooling zone 22. The side channel 18 forms a material-free space in which no material to be burned is located. The side channel 18 preferably extends along the shaft wall facing away from the connecting channel, along the lower portion of the combustion zone 20 and / or the upper portion of the cooling zone 22. Preferably, the side channel 18 is arranged at the level of the overflow channel 19.The cross-section of the shaft section of the cooling zone 22 is, for example, larger than the cross-section of the lower area of ​​the combustion zone 20, so that at the upper end of the cooling zone 22 and adjacent to the combustion zone 20, the material-free space 18 is formed, in particular as a side channel, in which no material is arranged.

[0053] It is also conceivable that the combustion zone 20 and the preheating zone 21 of shafts 2a, b have a cross-section that is essentially constant along the shaft length. The outer wall of the shafts 2, which extends radially outwards from the overflow channel, extends exclusively vertically along the entire shaft length, particularly along the length of the combustion zone 20 and the cooling zone 22. The cooling zone 22 preferably has a cross-section that increases in size towards the connecting channel 19, which opens into the connecting channel 19. Optionally, the shafts 2 of the GGR shaft furnace 1 are completely filled with material, so that no material-free space is formed, particularly in the combustion zone 20 and the cooling zone 22.

[0054] Following the combustion zone 20 in the direction of material flow in each shaft 2, the cooling zone 22 extends to the material outlet 40. The cooling zone 22 is exemplified by a shaft section with a cross-section that is essentially constant or decreases downwards. Within the cooling zone 22, the material is cooled to approximately 100°C to 250°C in countercurrent flow to the cooling gas flowing through it.

[0055] The cooling gas flowing into the cooling zone 22 via the cooling gas inlet 23 preferably flows completely to a cooling gas outlet 42, which is preferably designed as an opening in the shaft wall or as a side channel. From the cooling gas outlet 42, the cooling gas flows, in particular, completely out of the respective shaft 2, preferably exclusively out of the cooling zone 22 of the shaft 2. The cooling gas outlet 42 is, for example, connected to a cooling gas line 44, which is arranged outside the shaft 2. The cooling gas outlet 42 is, in particular, connected via the cooling gas line 44 to a cooling gas inlet 43 for introducing the cooling gas into the shaft 2. The cooling gas outlet 42 is preferably arranged entirely within the cooling zone 22, in particular in the material-free side channel 18, wherein the cooling gas inlet 43 is arranged within the preheating zone 21, in particular at the lower end of the preheating zone 21, of the respective shaft 2a,b.Preferably, each shaft 2, the combustion shaft and the regeneration shaft, has a cooling gas outlet 42 and a cooling gas inlet 43, which are connected to each other via the cooling gas line 44 to guide the cooling gas from the cooling gas outlet 42 to the cooling gas inlet 43.

[0056] In the exemplary embodiment of the Fig. 1 The cooling gas discharged from the cooling zone 22 via the cooling gas outlet 42 is fed to the cooling gas inlet 43, particularly to the preheating zone 21, via a cooling gas line 44 designed as a bypass to the combustion zone 21. The cooling gas inlet 43 is preferably located in the preheating zone 21 and is preferably designed as an opening in the shaft wall of the preheating zone 21. The cooling gas inlet 43 is, for example, designed as a slot in the shaft wall, which extends, in particular, horizontally. The cooling gas line 44 has a control element 8, such as a flap or a valve, which is designed, for example, such that the amount of cooling gas discharged via the cooling gas outlet 42 is adjustable. Preferably, the control element 8 is set such that the entire amount of cooling gas from the cooling zone is discharged via the cooling gas outlet 42 and fed back to the cooling gas inlet 43.

[0057] The GGR shaft furnace 1 preferably has a cooling gas outlet 17 for releasing cooling gas from the shaft 2, in particular from the regeneration shaft 2b. The cooling gas outlet 17 is, by way of example, arranged in the preheating zone 21 of the GGR shaft furnace 1, in particular in the regeneration shaft 2b and / or the combustion shaft 2a. Preferably, each shaft 2 has a cooling gas outlet 17. In particular, the cooling gas outlet 17 is arranged in the outer wall of the shaft 2, preferably in the outer wall of the preheating zone 21 or the combustion zone 20, and extends completely through this wall and out of the respective shaft 2. The cooling gas outlet 17 is preferably arranged completely within the preheating zone 21, so that the cooling gas is discharged from the preheating zone 21 and the shaft 2 through the cooling gas outlet 17.The cooling gas outlet 17 is preferably connected to the preheating zone 21 via a gas connection, so that the cooling gas can preferably flow through the preheating zone 21 and subsequently through the cooling gas outlet 17. Preferably, the cooling gas outlet 17 is arranged in a region of the outer wall of the preheating zone 21 that faces away from the overflow channel 19. The cooling gas outlet 17 is preferably arranged in the outer wall of the shaft 2, in particular the regeneration shaft 2b, opposite the overflow channel 19.

[0058] A discharge device 41 is preferably arranged at the material outlet end of each shaft 2. The discharge devices 41 comprise, for example, horizontal plates, preferably a discharge table, which allow lateral passage of the material between the discharge table and the housing wall of the GGR shaft furnace. The discharge device 41 is preferably designed as a push or rotary table or as a table with a push scraper. This enables a uniform throughput rate of the material being fired through the shafts 2. The discharge device 41 further comprises, for example, the discharge hopper 25, which connects to the discharge table and at the lower end of which the material outlet 40 is located.

[0059] During operation of the GGR shaft kiln 1, the material to be fired flows from top to bottom through the respective shaft 2, while the cooling air flows from bottom to top, counter-current to the material, through the respective shaft 2. The kiln exhaust gas is discharged from the shaft 2 through the exhaust outlet 6. During operation of the GGR shaft kiln 1, one of the shafts 2 is active at any given time, while the other shaft 2 is passive. The active shaft 2a is designated as the firing shaft, and the passive shaft 2 is designated as the regeneration shaft 2b. The GGR shaft kiln 1 is operated primarily in cycles, with a typical number of cycles being, for example, 75 to 150 cycles per day. After the cycle time has elapsed, the function of the shafts 2 is reversed. This process is repeated continuously. Material such as limestone or dolomite is alternately fed into the shafts 2 via the material inlets 3.In the active shaft 2, operated as combustion shaft 2a, fuel is introduced into the combustion shaft 2 via the burner lances 10. The material to be burned is preferably heated to a temperature of approximately 700°C in the preheating zone 21 of combustion shaft 2a. In the exemplary embodiment of the . Fig. 1 The left shaft 2 will be operated as combustion shaft 2a, while the right shaft 2 will be operated as regeneration shaft 2b.

[0060] During operation of the GGR shaft furnace 1, the cooling gas flows in counterflow to the material to be cooled through the cooling zone 22 in both the combustion shaft 2a and the regeneration shaft 2b and is preferably completely directed into the cooling gas line 44, which is arranged separately from the combustion zone.

[0061] Within shaft 2, operated as combustion shaft 2a, the combustion gas flows through the combustion gas inlet 12 into the combustion shaft and, in cocurrent flow with the material within the combustion zone 20, into the overflow channel 19 and subsequently into shaft 2, operated as regeneration shaft 2b. Within regeneration shaft 2b, the gas flows from the connecting channel 19 countercurrently to the material to be burned through the combustion zone 20 into the preheating zone 21 and exits regeneration shaft 2b through the exhaust gas outlet 6 of regeneration shaft 2b. Preferably, the exhaust gas discharged from shaft 2 has a temperature of 60°C to 160°C, preferably 100°C.

[0062] The exhaust gas is directed into an exhaust gas line 39 connected to the exhaust gas outlet 6. The exhaust gas line 39 optionally includes an exhaust gas filter 31 downstream of the exhaust gas outlet 6 for filtering fine particles, especially dust, from the exhaust gas. The GGR shaft furnace 1 preferably has a plurality of control elements, wherein, in particular, one control element is assigned to each exhaust gas outlet 6 or combustion gas inlet 12 for regulating the flow to or from the exhaust gas outlet 6 and the combustion gas inlet 12. The control element is, for example, a throttle valve or a compressor. The combustion gas inlet 12 is preferably connected to an upstream control element, so that preferably only the combustion gas, in particular the oxidizer, together with the recirculated exhaust gas, is supplied to the combustion gas inlet 12 of the shaft 2, which is operated as a combustion shaft 2a.

[0063] The exhaust gas line 39 includes, for example, a compressor 34 and a cooling device 32 downstream of the exhaust gas filter 31. The exhaust gas is preferably discharged downstream of the cooling device 32. Preferably, the entire CO₂ quantity from calcination and combustion, as well as the water from combustion, is discharged from the GGR shaft furnace 1. The cooling device 32 is, for example, a heat exchanger, preferably operated in counterflow with a coolant such as water. For example, the cooling device 32 is a trickle cooler. The GGR shaft furnace 1 has an exhaust gas recirculation line 15 that branches off from the exhaust gas line 39 and feeds a portion of the exhaust gas to the combustion gas inlet 12 of the shaft 2, in particular the combustion chamber 2a. The exhaust gas recirculation line 15 is preferably connected to the combustion gas inlet 12 and branches off from the exhaust gas line 39, particularly downstream of the cooling device 32.The exhaust gas not supplied to the combustion gas inlet 12 via the exhaust gas recirculation line 15 is preferably discharged from the GGR shaft furnace 1. The exhaust gas recirculation line 15 is, for example, connected to an oxidizer line 14 for supplying an oxidizer to the exhaust gas recirculation line 15. The oxidizer is preferably air or pure oxygen. For example, the oxidizer is an oxygen-rich gas with an oxygen content of at least 30 vol%, in particular at least 50 vol% or 60 vol%, preferably 70 vol% to 100 vol%, preferably 92 vol%. The oxidizer line 14 is preferably connected to an oxidizer source and preferably includes a control device for adjusting the amount of oxidizer supplied to the exhaust gas recirculation line 15.

[0064] The GGR shaft furnace 1 preferably has a buffer tank 45, to which the exhaust gas not recirculated via the exhaust gas recirculation line 15 is preferably fed. The buffer tank 45 is designed to temporarily store a certain quantity of exhaust gas before it is drawn off, for example, for further processing. By way of example, at least one fan is arranged upstream and downstream of the buffer tank in the direction of exhaust gas flow.

[0065] Fig. 1 Figure 1 additionally shows the gas flow within the GGR furnace 1, with the CO₂-containing combustion gas represented by the black arrows and the oxygen-containing cooling gas by the white arrows. According to an insight of the inventors, the oxygen-containing cooling gas flows in the regeneration shaft 2b and / or the combustion shaft 2a along the outer wall of the regeneration shaft 2b opposite the overflow channel 19 into the preheating zone 21. Preferably, the oxygen-containing cooling gas flows essentially separately from the combustion gas within the shafts 2, so that there is only a very slight mixing of the combustion gas and cooling gas flows. Recirculating the extracted cooling gas into the preheating zone offers the advantage that the heat from the cooling gas is additionally available to the GGR shaft furnace 1 in the preheating zone 21 for heating the material.In the GGR shaft furnace 1 according to the invention, the cooling air preferably flows through a large part, in particular almost the entire height, of the material bed of the preheating zone and has a comparatively low outlet temperature. This results in an optimal heat balance, whereby no additional height of the GGR shaft furnace 1 is required. Furthermore, a recuperator downstream of the cooling gas outlet for utilizing the waste heat can be omitted.

[0066] The cooling gas outlet 17 is preferably arranged downstream of the ends, in particular the fuel outlets, of the burner lances 10 in the gas flow direction of the regeneration shaft 2b. Preferably, the cooling gas outlet 17 is arranged downstream of the exhaust gas outlet 6 in the material flow direction.

[0067] The cooling gas outlet 17 is, for example, slot-shaped. In particular, the cooling gas outlet 17 preferably extends horizontally across the entire width of the shaft's outer wall. It is also conceivable that the cooling gas outlet 17 has a plurality of openings extending through the outer wall of the shaft 2, especially the preheating zone 21, which are, for example, arranged horizontally side by side across the entire width of the shaft's outer wall and preferably spaced evenly apart from one another.

[0068] The burner lances 10, for example, have in Fig. 1 Covers (not shown) are arranged upstream of the burner lance inlets 10 in the respective shaft 2, in the direction of material flow. The covers are designed and arranged to protect at least the upper portion of the burner lances 10 from contact, particularly impact, of the material against the burner lances 10. The cooling gas outlet 17 is located above or below the cover. The shaft 2 preferably has a refractory lining, which in particular includes a refractory lining. The cooling gas outlet 17 is preferably located at the upper end of the refractory lining.

[0069] The GGR shaft furnace 1 preferably has a cooling gas exhaust line 11, which is connected to the cooling gas outlet 17 for directing the cooling air out of the shaft 2. The cooling gas exhaust line 11 is located outside the shaft 2 and is connected to a filter 16. The filter 16 is preferably a particle filter, in particular a dust filter. The cooling air extracted via the cooling air outlet 17 preferably has a temperature of 100°C to 300°C. By way of example, the cooling air exhaust line 11 of the GGR shaft furnace 1 includes a control element 8, such as a damper or a valve, for adjusting the amount of cooling air that is extracted from the preheating zone 21 via the cooling gas outlet. By way of example, air is supplied to the cooling gas exhaust line 11 via a compressor or fan.For example, the cooling gas exhaust line 11 comprises at least two control elements, each control element 8 being assigned to a cooling gas outlet 17 for adjusting the respective cooling gas quantity. Preferably, only the control element 8 assigned to shaft 2, which is operated as a regenerative shaft 2b, is open, while the control element 8 assigned to combustion shaft 2a is closed. Downstream of the filter 16, the cooling gas is preferably discharged from the GGR shaft furnace 1. It is also conceivable that the cooling gas exhaust line 11 is connected to the oxidizer line 14, in particular to the combustion gas inlet 12, so that the extracted cooling air is supplied to combustion shaft 2a as combustion gas. Advantageously, with such a connection, no CO₂ is released into the atmosphere via the cooling gas outlet 17, but rather the entire cooling gas is discharged together with the exhaust gas and subsequently preferably treated or stored.

[0070] The GGR shaft furnace 1 optionally features a heat exchanger 24, which is connected to the exhaust gas recirculation line 15 and the cooling air exhaust line 11. The GGR shaft furnace 1 of the Fig. 1 The exhaust gas preferably has a CO₂ content of more than 70 vol%, particularly more than 75 vol%, and especially more than 90 vol%. With such process exhaust gas, it is possible to liquefy and sequester it with less effort. For example, the liquefied process exhaust gas is fed to further process steps or stored. Alternatively, exhaust gas with a lower CO₂ content, for example 45% for soda production or 30% for the production of beet sugar or precipitated calcium carbonate, can also be generated with the GGR shaft furnace described above.

[0071] Preferably, each shaft 2 has a cooling gas inlet 23 arranged in the cooling zone 22, which is connected, in particular, to a cooling gas supply line 7. Each cooling gas inlet 23 is optionally assigned a control element 4, such as a flap or a valve, which is connected to the cooling gas supply line 7 to adjust the quantity of cooling gas supplied to the respective cooling gas inlet 23. Preferably, the control elements 4 and / or a compressor 33 are adjusted such that a larger quantity of cooling air is supplied to the combustion shaft 2a than to the regeneration shaft 2b. Preferably, approximately 20% to 100%, preferably 90%, of the total quantity of cooling gas supplied to the GGR shaft furnace 1 is supplied to the combustion shaft 2a.

[0072] Fig. 2a shows the GGR shaft furnace of the Fig. 1 and Fig. 2b shows a section AA of the GGR shaft furnace 1 of the Fig. 2a , where the gas flows of the cooling air K and the combustion gases V are shown. The GGR shaft furnace 1 of the Fig. 2a has the previously described overflow channel 19 with a direct connecting channel 19a for the combustion gas and a direct connecting channel 19b for the cooling gas, so that the cooling air in the regeneration shaft 2b flows along the side channel opposite the overflow channel 19 through the preheating zone 21 of the regeneration shaft 2b. Fig. 2b show a cross-section through the preheating zone 21, whereby the cooling gas flows exclusively along the shaft wall facing away from the overflow channel 19.

[0073] Fig. 3 shows another embodiment of a GGR shaft furnace, which is largely based on the Fig. 1 and 2This corresponds with the difference that the overflow channel 19 is designed merely as a simple connecting channel in which the exhaust gas from the combustion zone, in particular the combustion gas, and the cooling gas are carried together.

[0074] Fig. 4a und b show another embodiment of a GGR shaft furnace, which largely corresponds to the Fig. 1 and 2 corresponds and where identical elements are provided with the same reference numerals. The GGR shaft furnace 1 of the Fig. 4 The GGR shaft furnace 1 features, for example, shafts 2, each with a round, in particular circular, cross-section. Fig. 4 It features a cooling gas exhaust device comprising an inner cylinder 26 that extends at least partially from the cooling zone 22 into the combustion zone 20 and has a cooling gas outlet 42 connected to the cooling gas line 44. The cooling zone 22 is exemplified in a shaft section having an approximately constant cross-section. The material-free annular space of the GGR shaft furnace of the Fig. 1 , is in the exemplary embodiment of the Fig. 4a also trained. Each shaft 2 of the GGR shaft furnace 1 of the Fig. 4a It has an inner cylinder 26 that extends centrally in a vertical direction through the cooling zone 22. For example, the inner cylinder 26 extends from the discharge device 41 through the cooling zone 22 into the combustion zone 20 up to the level of the overflow channel 19.

[0075] The inner cylinder 26 of the cooling gas exhaust device has a cooling gas outlet 42, which extends radially outwards from the inner cylinder 26 through the shaft wall and serves to direct cooling gas from the inner cylinder into the cooling gas line 44. The inner cylinder 26 also has a cooling gas inlet 30 for introducing cooling gas from the cooling zone 22 into the inner cylinder 26. The cooling gas inlet 30 extends through the inner cylinder wall into the cooling zone 22 and connects the interior of the inner cylinder 26 with the cooling zone 22. The cooling gas inlet 30 is preferably arranged above the cooling gas outlet 42 in the cooling zone 22. During operation of the GGR shaft furnace 1, the cooling gas flows from bottom to top through the cooling zone 22 and into the cooling gas inlet 30 in the inner cylinder 26 of the cooling gas exhaust device.Preferably, all the cooling gas introduced into the cooling zone 22 flows through the cooling gas inlets 30 into the cooling gas exhaust device, so that no cooling gas enters the combustion zone 20. The cooling air outlet 42 of the inner cylinder 26 is preferably arranged in the lower region of the cooling zone 22. The cooling gas flows, in particular, from the cooling gas inlet 30 in the inner cylinder 26 downwards to the cooling gas outlet 42. The cooling gas line 44 includes, for example, at least or exactly two control elements 8. Preferably, one control element 8 is connected downstream of each cooling gas outlet 42 and is designed and configured such that the amount of cooling gas flowing through the cooling gas outlet 42 can be adjusted via the control element 8. A further control element 8 is preferably connected upstream of each cooling gas inlet 43 and is designed and configured such that the amount of cooling gas flowing into the cooling gas inlet 43 can be adjusted via the control element 8.The cooling gas inlet 43 and / or the cooling gas outlet 17 are each designed, for example, as a slot which preferably extends over the entire circumference of the preheating zone 21.

[0076] In the exemplary embodiment, the routing of the cooling gas extracted from cooling zone 22 and preheating zone 21 and the exhaust gas extracted from preheating zone 21 correspond to the Fig. 1 , 2 and 3 described wiring. Fig. 4b Figure 2b shows a cross-section through the preheating zone of the regenerative shaft 2b, showing the combustion gas V, in particular the exhaust gas from combustion zone 20, and the cooling gas K. According to the inventors, the cooling gas K flows through the preheating zone exclusively in the radially outer, wall-adjacent region of shaft 2.

[0077] Fig. 5a und b show another embodiment of a GGR shaft furnace, which largely corresponds to the Fig. 1 , 2 , 3 or 4corresponds and where identical elements are provided with the same reference numerals. The GGR shaft furnace of the Fig. 5a It also has a round, specifically a circular, cross-section. Analogous to the Fig. 3 and 4 The shaft furnace indicates Fig. 5a The system also includes an overflow channel 19, which is designed as a singular connecting channel 19. The combustion zone 20 extends, for example, into a first and a second shaft section, the first shaft section having a substantially constant cross-section or one that increases slightly towards the bottom. A second shaft section adjoins the first shaft section in the direction of material flow, and this second shaft section has a cross-section that decreases in the direction of material flow. The lower part of the first shaft section extends into the upper part of the second shaft section, so that a first material-free annular channel 18a is formed between the two shaft sections.The second shaft section has a larger cross-section in its upper region than the first shaft section, the cross-section of the second shaft section decreasing to that of the first shaft section in the direction of material flow and preferably forming the lower end of the combustion zone 20. The cooling zone 22 preferably has a further, second material-free annular space 18b, with a first annular space 18a being located at the level of the overflow channel 19 and a second annular space 18b being located below the overflow channel 19. The cooling gas outlet 42 is, by way of example, located in the second annular channel 18b and connected to the cooling gas line 44.

[0078] Fig. 5b Figure 1 shows a cross-section through the preheating zone of the regeneration shaft 2b, showing the combustion gas V, in particular the exhaust gas from the combustion zone 20, and the cooling gas K. According to the inventors' findings, the cooling gas K flows exclusively through the preheating zone 21 in the radially outer, wall-adjacent region of the shaft 2. In this embodiment, the routing of the cooling gas drawn from the cooling zone 22 and the preheating zone 21, and the exhaust gas drawn from the preheating zone 21, corresponds to the following: Fig. 1 , 2 , 3 and 4 described wiring.

[0079] Fig. 6 shows another embodiment of a GGR shaft furnace, which is largely based on the Fig. 1 bis 5 corresponds and where identical elements are provided with the same reference numerals. The overflow channel 19 comprises two parallel, direct connecting channels 19a and 19b. In contrast to the GGR shaft furnaces 1 described above, the GGR shaft furnace 1 of the Fig. 6 A cooling gas line 44 is arranged within the shaft 2. The GGR shaft furnace 1 has a partition wall 46 in each shaft 2, through which the cooling gas line 44 is separated. The partition wall 46 preferably extends vertically from the combustion zone 20 to the shaft ceiling. In particular, the lower end of the partition wall 46 is arranged at the level of the overflow channel 19, with the upper end of the partition wall 46, for example, abutting the shaft ceiling. In particular, the partition wall 46 extends over the entire width, and especially the depth, of the shaft and is preferably aligned parallel to the shaft wall opposite the overflow channel 19. The partition wall 46 preferably forms the cooling gas line 44 together with the inner wall of the shaft 2, especially of the regeneration shaft 2b. Preferably, the partition wall 46 is arranged in a region of the shaft 2 facing away from the overflow channel 19.The cooling gas line 44 comprises, for example, approximately 20-40%, preferably approximately 33% of the volume of the combustion zone 20 and the preheating zone 21.

[0080] The cooling gas drain 42 for draining cooling gas from the cooling zone 22 is in the exemplary embodiment of the Fig. 6 formed between the partition wall 46 and the shaft wall opposite the overflow channel 19. The shaft furnace 1 of the Fig. 6 It also has a cooling gas outlet 17, which is arranged at an upper end of the preheating zone 21. The cooling gas outlet 17 of the combustion chamber 2a is preferably connected to the exhaust gas recirculation line, so that during combustion operation of the respective chamber 2, recirculated and oxygen-enriched exhaust gas is introduced into the combustion chamber 2a via the cooling gas outlet 17. In particular, recirculated and oxygen-enriched exhaust gas is introduced via the cooling gas outlet 17 into the cooling gas line 44 between the partition wall 46 and the chamber wall opposite the overflow channel 19. The GGR shaft furnace 1 of the Fig. 6 The device preferably has a further combustion gas inlet 12 in each shaft, through which recirculated and oxygen-enriched exhaust gas is introduced into the combustion shaft 2a outside the cooling gas line 44. Preferably, according to an insight of the inventors, the cooling air flows exclusively along the outer shaft section opposite the overflow channel 19, so that it is separated from the combustion gas of the combustion zone 20 by the partition wall 46. Mixing of the combustion gases and the cooling gases is thus reliably prevented.

[0081] The shaft furnace 1 of the Fig. 6 preferably has a plurality of material inlets 3. In particular, the shaft furnace 1 has at least two material inlets 3 in each shaft 2, wherein at least one material inlet is assigned to the cooling gas line 44 and is arranged such that material to be burned is supplied to the cooling gas line 44. In the exemplary embodiment, the lines for the cooling gas drawn from the cooling zone 22 and the preheating zone 21 and the exhaust gas drawn from the preheating zone 21 correspond to the Fig. 1 bis 5 described wiring. Bezugszeichenliste

[0082] 1GGR shaft furnace 2Shaft 2aCombustion shaft 2bRegeneration shaft 3Material inlet / airlock 4Control element 6Exhaust gas outlet 7Cooling gas supply line 8Control element 9Fuel line 10Burner lances 11Cooling gas discharge line 12Combustion gas inlet 13Separating element 14Oxidizing agent line 15Exhaust gas recirculation line 16Filter 17Cooling gas outlet 18Side channel / annular channel / material-free space 19Overflow channel 19aFirst connecting channel 19bSecond connecting channel 20Combustion zone 21Preheating zone 22Cooling zone 23Cooling gas inlet 24Heat exchanger 25Outlet hopper 26Inner cylinder 30Cooling gas inlet 31Exhaust gas filter 32Cooling unit 33, 34, 35Compressor 39 Exhaust pipe 40 Material outlet / airlock 41 Discharge device 42 Cooling gas outlet 43 Cooling gas inlet 44 Cooling gas line 45 Buffer tank 46 Partition wall Cooling air Combustion exhaust

Claims

1. Parallel flow counterflow regenerative shaft kiln (1) for burning and cooling material, such as carbonate rocks, with two shafts (2) that can be operated alternately as a burning shaft (2a) and as a regenerative shaft (2b) and are connected to each other by means of an overflow channel (19), wherein each shaft (2) has, in the direction of flow of the material, a preheating zone (21) for preheating the material, a burning zone (20) for burning the material, and a cooling zone (22) for cooling the material, wherein each shaft (2) has an exhaust gas outlet (6) for discharging exhaust gas from the shaft (2), characterized in that the parallel flow counterflow regenerative shaft kiln (1) has a cooling gas line (44) for conducting cooling gas from the cooling zone (22) into the preheating zone (21).

2. Parallel flow counterflow regenerative shaft kiln (1) according to claim 1, wherein the cooling gas line (44) is arranged outside or inside the shaft (2).

3. Parallel flow counterflow regenerative shaft kiln (1) according to one of the preceding claims, wherein the shaft kiln (1) has a cooling gas outlet (42) for discharging cooling gas from the cooling zone (22), and wherein the cooling gas outlet (42) is arranged inside the cooling zone (22) and is connected to the cooling gas line (44) in a gas-technical manner.

4. Parallel flow counterflow regenerative shaft kiln (1) according to one of the preceding claims, wherein the shaft kiln (1) has a cooling gas inlet (43) in the preheating zone (21) for admitting cooling gas into the preheating zone (21), which is connected to the cooling gas line (44) in a gas-technical manner.

5. Parallel flow counterflow regenerative shaft kiln (1) according to claim 4, wherein the cooling gas inlet (43) is designed in the form of a slot.

6. Parallel flow counterflow regenerative shaft kiln (1) according to one of claims 1 to 3, wherein the shaft kiln (1) has a partition wall (46) which is arranged inside the shaft (2) and at least partially forms the cooling gas line (44).

7. Parallel flow counterflow regenerative shaft kiln (1) according to claim 6, wherein the cooling gas outlet (44) for discharging cooling gas from the cooling zone (22) is formed between the partition wall (46) and the inner wall of the shaft (2).

8. Parallel flow counterflow regenerative shaft kiln (1) according to one of the preceding claims, wherein the shaft kiln (1) has a cooling gas outlet (17) for discharging the cooling gas from the shaft (2) and wherein the cooling gas outlet (17) is arranged in the preheating zone (21) of the shaft (2).

9. Parallel flow counterflow regenerative shaft kiln (1) according to one of the preceding claims, wherein at least one or a plurality of control elements (8) are arranged in the cooling gas line (44), which are designed in such a way that they control / regulate the amount of cooling air from the cooling gas outlet (42) and / or to the cooling gas inlet (43).

10. Parallel flow counterflow regenerative shaft kiln (1) according to one of the preceding claims, wherein the overflow channel (19) comprises a first connecting channel (19a) and a second connecting channel (19b), which are arranged parallel to each other in terms of gas flow.

11. Parallel flow counterflow regenerative shaft kiln (1) according to claim 10, wherein the first connecting channel (19a) is arranged and designed such that only the exhaust gas from the combustion zone (20) can flow into the first connecting channel (19a).

12. Parallel flow counterflow regenerative shaft kiln (1) according to claim 10 or 11, wherein the second connecting channel (19b) is arranged and designed such that only the cooling gas from the cooling zone (22) can flow into the second connecting channel (19b).

13. Method for burning material, such as carbonate rocks, in a Parallel flow counterflow regenerative shaft kiln (1) with two shafts (2) which are operated alternately as a burning shaft and as a regenerative shaft and are connected to each other by means of a connecting channel (19), wherein the material is fed through a material inlet (3) into a preheating zone (21) for preheating the material, a burning zone (20) for burning the material, and a cooling zone (22) for cooling the material to a material outlet (40), wherein a cooling gas is admitted into the cooling zone, wherein exhaust gas is discharged from one of the shafts (2) via an exhaust gas outlet (6), and characterized in that the cooling gas is fed from the cooling zone (22) into the preheating zone (21) by means of a cooling gas line (44).

14. Method according to claim 13, wherein the cooling gas is fed separately from the combustion gases of the combustion zone (20) into the cooling gas line (44).

15. Method according to claim 13 or 14, wherein the cooling gas is extracted from the cooling zone (22) and fed into the preheating zone (21).

16. Method according to one of claims 13 to 15, wherein the cooling gas introduced into the preheating zone (21) via the cooling gas line (44) is discharged from the preheating zone (21) by means of a cooling gas outlet (17).