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

Abstract

The invention also relates to a parallel-flow regenerative (PFR) shaft kiln (1) for burning and cooling material, such as carbonate rock, said kiln having two shafts (2) which can be operated alternately as a combustion shaft (2a) and a regenerative shaft (2b) and are connected to each other by means of a connecting channel (19), wherein: each shaft (2) has, in the flow direction of the material, 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; each shaft (2) has an exhaust gas outlet (6) for discharging exhaust gas from the shaft (2); the PFR shaft kiln (1) has at least one cooling gas outlet (17) for discharging cooling gas from the shaft (2); and the cooling gas outlet (17) is located in the preheating zone (21) or the combustion zone (20). The invention also relates to a method for burning material, such as carbonate rock, in a parallel-flow regenerative shaft kiln (1) with two shafts (2) which are operated alternately as a burning shaft and a regenerative shaft and are connected to each other by means of a connecting channel (19), wherein: the material flows through a material inlet (3) into 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 in order to reach a material outlet (40); a cooling gas is introduced into the cooling zone; exhaust gas is discharged from one of the shafts (2) via an exhaust gas outlet (6); and the cooling gas is discharged from at least one of the shafts (2) via a cooling gas outlet (17) in the preheating zone (21) or the combustion zone (20).

Description

[0001] Co-current countercurrent regenerative furnace and process for burning carbonate rock

[0002] The invention relates to a cocurrent countercurrent regenerative shaft furnace (GGR shaft furnace) and a method for burning and cooling material, such as carbonate rocks, using a GGR shaft furnace.

[0003] The burning 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, with burning taking place only in one shaft, the respective combustion shaft, while the other shaft operates as a regenerative shaft. Oxidation gas is fed to the combustion shaft in cocurrent with the material and fuel. The resulting hot exhaust gases, together with the heated cooling air supplied from below, are channeled via the overflow channel into the regenerative shaft, where the exhaust gases are discharged upward in countercurrent to the material, preheating the material. The material is usually fed into the shaft from above together with the oxidation gas, with fuels being injected into the combustion zone.

[0004] In each shaft, the material to be burned usually passes through a preheating zone to preheat the material, a subsequent burning zone in which the material is burned and a subsequent cooling zone in which cooling air is supplied to the hot material.

[0005] To meet the quality requirements for high reactivity of the quicklime, as required in steelworks, for example, temperatures in the firing zone must not exceed 1100°C, preferably 1000°C. Furthermore, the demand for environmentally friendly quicklime production is also increasing, so certain requirements regarding the CO2 content of the exhaust gas for subsequent post-treatment must be met. However, the production of environmentally friendly lime should be as cost-effective as possible and require only minimal modifications to existing facilities. Furthermore, the operation of the lime kilns should be as energy-efficient as possible.Based on this, it is the object of the present invention 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 object is achieved 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 11. Advantageous further developments emerge from the dependent claims.

[0007] According to a first aspect, the invention comprises a cocurrent countercurrent regenerative shaft furnace for burning and cooling material, such as carbonate rocks, having two shafts that can be operated alternately as a burning shaft and as a regenerative shaft and are connected to one another by means of a connecting channel. Each shaft has, in the direction of flow of the material, a preheating zone for preheating the material, a burning zone for burning the material, and a cooling zone for cooling the material. Each shaft has an exhaust gas outlet for discharging exhaust gas from the shaft. The PGR shaft furnace has a cooling gas outlet for discharging cooling gas from the shaft, wherein the cooling gas outlet is arranged in the preheating zone or the burning zone. In particular, the cooling gas outlet is arranged entirely and exclusively in the preheating zone or the burning zone.

[0008] The material to be burned is preferably limestone or dolomite with a grain size of 10 mm to 200 mm, preferably 15 to 120 mm, and most preferably 30 mm to 100 mm. The cooling gas is, for example, air.

[0009] The cocurrent-countercurrent regenerative shaft furnace has at least two shafts, which are preferably arranged parallel to one another and vertically. The shafts can be operated alternately as a combustion shaft and as a regenerative shaft, with each shaft having, in the direction of flow of the material, a preheating zone for preheating the material, a combustion zone for burning the material, and a cooling zone for cooling the material. Each shaft preferably has a material inlet for admitting material to be burned into the shaft, with the material inlet being located in particular at the upper end of the respective shaft so that the material falls into the respective shaft by gravity. The material inlet and / or the material outlet is / are designed in particular as a lock for admitting and / or discharging material into the shaft furnace.A material inlet designed as a lock is preferably configured such that only the raw material to be burned enters the shaft, but not the ambient air. The material lock also prevents gas from escaping from the shaft via the material inlet. The lock is preferably designed such that it seals the shaft hermetically from the environment and allows 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 filled with material. Material-free spaces that are separated, for example, by a wall from the material-filled areas of the shaft are preferably not part of the preheating zone, combustion zone, or cooling zone.

[0010] The connecting channel is designed to provide a gas connection between the two shafts and preferably connects the combustion zones of the shafts. During operation of the GGR shaft furnace, one of the shafts is operated as a combustion shaft and is active, while the other shaft is operated as a regenerative shaft and is passive. The GGR shaft furnace is operated cyclically, with the function of the shafts being swapped after the cycle time has elapsed. This process is repeated continuously. In the active shaft operated as a combustion shaft, a fuel is introduced into the combustion zone via the burner lances. The material to be burned is heated in the preheating zone of the combustion shaft, preferably to a temperature of approximately 700°C. In the shaft operated as a combustion shaft, the combustion zone is designed as a cocurrent combustion zone, with the material to be burned flowing parallel to the gas.The gas flows within the combustion shaft from the preheating zone into the combustion zone and then via the connecting channel into the combustion zone and preheating zone of the regenerative shaft. In the öcnacnt, which operates as a regenerative shaft, the gas flows countercurrently to the material being burned in the preheating zone and the combustion zone.

[0011] In both the combustion shaft and the regenerative shaft, cooling gas is passed 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, so that preferably no or only a small amount of cooling gas flows into the exhaust outlet of the respective shaft. The cooling gas outlet is preferably arranged within the preheating zone or the combustion zone such that at least 60%, in particular at least 70%, preferably at least 80% to at least 90% of the cooling gas quantity supplied to the PFR shaft furnace is discharged from the shaft via the cooling gas outlet. The cooling gas outlet is preferably arranged separately from the exhaust outlet.In particular, the cooling gas outlet is arranged and designed within the preheating zone or the combustion zone such that 85% to 110%, in particular 90% to 105%, preferably 100% of the cooling gas quantity supplied to the PGR shaft furnace is discharged as cooling gas exhaust air via the cooling gas outlet.

[0012] Each shaft preferably has at least one exhaust gas outlet, for example at the upper end of the shaft within the preheating zone. The exhaust gas outlet is preferably arranged above the material column in a material-free region of the preheating zone. The exhaust gas is preferably discharged exclusively from one shaft, in particular the regenerative shaft. 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 regenerative shaft is fed back to at least one shaft. A portion of the exhaust gas discharged from the regenerative shaft is discharged, for example, from the PFR shaft furnace and fed, for example, to further treatment, such as sequestration. The exhaust gas preferably consists of CO2 and optionally H2O.The PGR shaft furnace preferably has a combustion gas inlet for admitting 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. A fuel is preferably supplied to the combustion zone and / or the preheating zone of a shaft operated as a combustion shaft via a fuel line. The fuel is preferably supplied to burner lances arranged in the combustion zone and / or the preheating zone. The fuel is, for example, a fuel gas, such as blast furnace gas, natural gas, pulverized coal, biomass, or liquid fuels. In the combustion zone, the material is preferably heated to a temperature of approximately 1050°C.

[0013] Each shaft preferably has a plurality of burner lances which extend at least partially through the preheating zone and in particular open into the combustion zone of the respective shaft and serve to conduct, for example, fuel and / or an oxidizing gas, such as air or oxygen-enriched air or pure oxygen.

[0014] Recirculating the exhaust gas into at least one shaft enables the production of lime with high reactivity, while simultaneously producing process gas with a CO2 content of more than 30 vol%, in particular more than 50 vol%, preferably more than 70 vol%, based on dry gas. Such process exhaust gas can be liquefied and sequestered with less effort. For example, the liquefied process exhaust gas is fed to further process steps or stored. Alternatively, the PFR shaft kiln described above can also be used to produce exhaust gas with a lower CO2 content, for example, 40% to 50% for soda production or 30% to 35% based on the dry gas for the production of beet sugar or precipitated calcium carbonate.

[0015] The cooling gas outlet is preferably arranged entirely within the preheating zone or the combustion zone, so that the cooling gas is conducted out of the preheating zone or the combustion zone through the cooling gas outlet. In particular, the cooling gas outlet is gas-connected to the preheating zone and / or the combustion zone, wherein the cooling gas outlet is preferably arranged downstream of the combustion zone within the regenerative shaft in the gas flow direction. Each shaft preferably has at least one cooling gas outlet, wherein preferably only the cooling gas outlet arranged in the shaft operated as a regenerative shaft is open, and the cooling gas outlet of the combustion shaft is gas-connected.

[0016] According to a discovery by the inventors, the oxygen-containing cooling gas flows essentially separately from the combustion gas within the shafts, resulting in only minimal mixing of the combustion gas and cooling gas streams. Extracting the cooling gas via the cooling gas outlet in the preheating zone or the combustion zone offers the advantage over extracting the cooling gas from the cooling zone in that the heat from the cooling gas is also available to the PFR shaft furnace in the combustion zone and the preheating zone for heating the material. In the PFR shaft furnace according to the invention, the cooling air preferably flows through a large portion, in particular almost the entire portion, of the material bed. This leads to an optimal heat balance, while no additional height of the PFR shaft furnace is required. Furthermore, a recuperator downstream of the cooling gas outlet for utilizing the waste heat can be dispensed with.

[0017] According to a first embodiment, the cooling gas outlet is arranged in the outer wall of the shaft. Preferably, the cooling gas outlet extends completely through the outer wall of the shaft and is in particular arranged in the outer wall surrounding the preheating zone or the combustion zone. Preferably, the PGR shaft furnace has a refractory lining that extends, for example, from the cooling zone to the preheating zone, in particular to a lower region of the preheating zone. The cooling gas outlet is preferably arranged above the lining or at an upper end region of the lining. The cooling gas outlet is preferably arranged completely in the preheating zone or the combustion zone, so that the cooling air flows from the cooling zone, in particular completely into the combustion zone. A cooling gas outlet arranged 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 converted without great effort. According to a further embodiment, the PGR shaft kiln has one or a plurality of burner lances arranged such that they open into the combustion zone, wherein the cooling gas outlet is arranged downstream of at least one of the burner lance mouths in the gas flow direction of the regenerative shaft. Preferably, the cooling gas outlet is arranged downstream of all burner lance mouths in the gas flow direction. The burner lances have, for example, covers arranged upstream of the burner lance inlets in the respective shaft in the flow direction of the material. Preferably, each burner lance is assigned a cover. The covers are designed and arranged such that they protect at least the upper region of the burner lances from contact, in particular impact, of the material on the burner lances.The cooling gas outlet is preferably located below the cover, particularly downstream of the cover in the material flow direction. The burner lances, particularly the burner lance covers, represent a flow obstacle for the cooling gas and combustion gas flowing toward the preheating zone, causing turbulence and mixing of the gas streams as they pass through the burner lances. Therefore, arranging the cooling gas outlet upstream of the burner lance covers in the gas flow direction is advantageous in order to discharge, as far as possible, only the cooling gas flow through the cooling gas outlet.

[0018] According to a further embodiment, each shaft has a cooling gas outlet, wherein each cooling gas outlet is assigned a control element for adjusting the amount of cooling gas to be discharged via the cooling gas outlet, and wherein 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. The cooling gas outlet is preferably connected to a cooling gas discharge line arranged outside the shaft. The control element is preferably gas-connected to the cooling gas outlet and is arranged in particular in the cooling gas discharge line. The control element is, for example, a flap or a valve that is continuously adjustable between an open position and a closed position.The control element associated with the cooling gas outlet of the regenerative shaft is preferably designed and configured such that 85% to 110%, in particular 90% to 105%, preferably 100%, of the cooling gas quantity supplied to the PGR shaft furnace is discharged as cooling gas exhaust air via the cooling gas outlet of the regenerative shaft. The cooling gas discharge line is connected, for example, to the combustion gas inlet, in particular to the exhaust gas recirculation line for conveying 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 connection, no CO2-containing gas is released into the atmosphere via the cooling gas outlet; instead, the entire exhaust gas is preferably fed via the exhaust gas outlet for further processing or storage.

[0019] According to a further embodiment, the cooling gas outlet is arranged in a region of the outer wall of the preheating zone or the combustion zone facing away from the connecting channel. The PFR shaft furnace preferably has a direct connecting channel for directly connecting the combustion shaft to the regenerative shaft. For example, the shafts each have a square, triangular, square, rectangular, round, oval, polygonal, semicircular, partially circular, or circular cross-section. The connecting channel preferably forms a direct gas connection between the two shafts, with the cooling gas from the combustion shaft flowing together with the fuel gas from the combustion shaft directly into the connecting channel and subsequently into the regenerative shaft.Preferably, the GGR shaft furnace does not have an annular channel in addition to and at the same height as the connecting channel, and the shafts are preferably directly connected to one another in terms of gas technology without one or more annular channels. For example, the combustion zone and the preheating zone of the shafts have a cross-section that is essentially constant over the shaft length. The outer wall of the shafts, which faces radially outwards away from the connecting channel, extends in particular exclusively vertically over the entire shaft length, in particular over the length of the combustion zone and the cooling zone. The cooling zone preferably has a cross-section that increases in the direction of the connecting channel and opens into the connecting channel. Preferably, the shafts of the GGR shaft furnace are completely filled with material, so that, in particular in the combustion zone and the cooling zone, no material-free annular space is formed at the level of the connecting channel.In a GGR shaft furnace with a direct connecting channel, the inventors have discovered that the oxygen-containing cooling gas flows from the cooling zone to the area of ​​the regenerative shaft opposite the connecting channel and upwards along the inside of the outer wall of the regenerative shaft. Preferably, the cooling gas flows essentially separately from the combustion gas of the combustion zone, so that only very minimal mixing of the gas streams occurs. A cooling gas outlet in the outer wall of the regenerative shaft facing away from the connecting channel allows for the removal of a large quantity, in particular almost the entire quantity of cooling gas, from the regenerative shaft, so that the exhaust gas discharged from the shaft via the exhaust outlet contains no or only a very small proportion of cooling air.

[0020] According to a further embodiment, the cooling gas outlet extends horizontally in the outer wall of the shaft. The cooling gas outlet is preferably 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 connecting channel. For example, the cooling gas outlet comprises a plurality of passage openings in the shaft outer wall, which are arranged horizontally next to one another, for example, and preferably at the same height.

[0021] According to a further embodiment, the GGR shaft furnace has a cooling gas extraction device which is connected to the cooling gas outlet for conducting the cooling gas and extends from the vertical center axis of the shaft to the cooling gas outlet. The GGR shaft furnace preferably comprises an indirect connecting channel. In a GGR shaft furnace with an indirect connecting channel, the connecting channel is connected to a material-free annular space which extends circumferentially around the lower end of the combustion zone. Preferably, both shafts have a material-free annular space at the level of the connecting channel and are gas-connected to the connecting channel. The cooling gas extraction device is preferably arranged entirely within the preheating zone or the combustion zone of the shaft and gas-connected to the cooling gas outlet. The cooling gas extraction device preferably extends radially through the preheating zone or the combustion zone of the regenerative shaft.In a PFR shaft furnace with an indirect cooling channel, the cooling gas flows centrally, particularly along the central longitudinal axis of the regenerative shaft, through the combustion zone and the preheating zone, essentially separately from the combustion gases flowing as a radially outer annular space. An arrangement of a cooling gas extraction device connected to the cooling gas outlet and extending radially outward from the central longitudinal axis offers a simple way to extract the cooling gas flowing separately from the combustion gases in the preheating zone or the combustion zone.

[0022] According to a further embodiment, the cooling gas extraction device comprises an exhaust hood and a line connected to it for gas purposes. The exhaust hood is preferably arranged coaxially with the shaft within the preheating zone and preferably has a round, in particular circular, cross-section. The exhaust hood is, for example, pot-shaped or funnel-shaped and preferably open downwards. The line preferably extends from the exhaust hood to the cooling gas outlet, in particular horizontally in the radial direction of the shaft. This enables the cooling gas to be extracted separately from the combustion gas from the preheating zone or the combustion zone.

[0023] According to a further embodiment, the PGR shaft furnace has a combustion gas inlet connected to a combustion gas source comprising a combustion gas having an oxygen content of more than 60 vol%, preferably more than 75 vol%, in particular more than 80 vol% to more than 95 vol% oxygen.

[0024] According to a further embodiment, each shaft has a cooling gas inlet, each of which is assigned a control element for adjusting the amount of cooling gas supplied to the respective cooling gas inlet. The control elements are adjusted such that a smaller amount of cooling air is supplied to the combustion shaft than to the regenerative shaft. The control element is, for example, a continuously adjustable valve or a flap. The control element is, for example, arranged upstream of the cooling gas inlet and, in particular, in a cooling gas line connected to the cooling air inlet. The control elements are preferably designed and configured such that 20% to 30%, preferably 25%, of the total amount of cooling gas supplied to the GuK secondary furnace is supplied to the combustion shaft.

[0025] The invention also includes a method for burning material, such as carbonate rocks, in a cocurrent countercurrent regenerative shaft furnace, wherein the embodiments and advantages described with reference to the cocurrent countercurrent regenerative shaft furnace also apply to the method in a process-related manner.

[0026] In a method for burning material, such as carbonate rocks, in a co-current countercurrent regenerative shaft furnace having two shafts which are operated alternately as a burning shaft and as a regenerative shaft and which are connected to one another by means of a connecting channel, the material flows through a material inlet into a preheating zone for preheating the material, a burning zone for burning the material and a cooling zone for cooling the material to a material outlet, wherein a cooling gas is admitted into the cooling zone, wherein exhaust gas is discharged from one of the shafts via an exhaust gas outlet and wherein the cooling gas is discharged from at least one of the shafts via a cooling gas outlet in the preheating zone or the burning zone.The cooling gas preferably flows in the regenerative shaft from the cooling zone into the combustion zone and then, together with the exhaust gas from the combustion zone, through the combustion zone into the preheating zone. It exits the shaft, in particular the regenerative shaft, through the cooling gas outlet located in the preheating zone or the combustion zone. The exhaust gas discharged from the shaft via the exhaust gas outlet is preferably fed to the combustion shaft. For example, the exhaust gas is introduced into the preheating zone of the shaft operating as a combustion shaft.

[0027] According to one embodiment, the cooling gas is discharged from the shaft via a cooling gas outlet arranged in the outer wall of the shaft.

[0028] According to a further embodiment, the cooling gas is preferably discharged exclusively from the regenerative shaft. According to a further embodiment, the amount of cooling gas discharged from the regenerative shaft via the cooling gas outlet is adjusted by means of a control device. Preferably, 85% to 110%, in particular 90% to 105%, and preferably 100% of the cooling gas quantity supplied to the PFR shaft furnace is discharged as cooling gas exhaust air via the cooling gas outlet.

[0029] According to a further embodiment, a combustion gas having an oxygen content of more than 60 vol%, preferably more than 75 vol%, in particular more than 80 vol% to more than 95 vol% oxygen is supplied to the PGR shaft furnace.

[0030] According to a further embodiment, a smaller amount of cooling air is supplied to the combustion shaft than to the regenerative shaft.

[0031] According to a further embodiment, preferably only the cooling gas flowing centrally through the preheating zone or the combustion zone is discharged from the shaft.

[0032] According to a further embodiment, preferably only the cooling gas flowing along the outer wall of the preheating zone is discharged from the shaft.

[0033] Preferably, each shaft has a gas inlet, in particular a combustion gas inlet, which is arranged in the upper region of the shaft in the preheating zone and serves to introduce the gas required for combustion. The gas inlet is preferably arranged above the material column in a material-free space of the preheating zone.

[0034] Preferably, an oxidizing agent is supplied to the shaft operated as a combustion shaft. The oxidizing agent is, for example, pure oxygen or an oxygen-rich gas with an oxygen content of more than 60 vol%, at least 70 to 95 vol%, preferably more than 80 vol% or more than 90%. The oxidizing agent is preferably introduced into the preheating zone of the combustion shaft together with the exhaust gas. It is also conceivable for the shaft in the preheating zone to have a separate oxidizing agent inlet for admitting the oxidizing agent into the shaft separately from the exhaust gas.

[0035] Optionally, the connecting channel is designed as an overflow channel, wherein the overflow channel has a first connecting channel and a second connecting channel 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 arranged, for example, above the second connecting channel.

[0036] For example, the first connecting channel is arranged and configured such that only the exhaust gas from the combustion zone can flow into the first connecting channel. According to a further embodiment, the second connecting channel is arranged and configured such that only the cooling gas from the cooling zone can flow into the second connecting channel. As a result, the cooling gas from the combustion shaft is introduced into the regenerative shaft independently of the combustion gases, and mixing of the combustion gases with the cooling gases within the overflow channel is reliably prevented.

[0037] The first connecting channel is designed, for example, as a direct connecting channel, and the second connecting channel as an indirect connecting channel. The PFR shaft furnace has, for example, an annular channel designed as a material-free space, which is preferably connected by gas to the overflow channel, in particular to the first or second connecting channel.

[0038] With the PGR shaft furnace described above and the method for operating the PGR 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%, is achieved. This enables further processing of the exhaust gas in other industrial processes or storage of the CO2-containing exhaust gas.

[0039] Description of the drawings The invention is explained in more detail below using several embodiments with reference to the enclosed figures.

[0040] Fig. 1 shows a schematic representation of a GGR shaft furnace in a sectional view according to an embodiment.

[0041] Fig. 2 shows a schematic representation of a GGR shaft furnace in a sectional view according to another embodiment.

[0042] Fig. 3a, b each show a schematic representation of a GGR shaft furnace in a longitudinal sectional view and a cross-sectional view according to a further embodiment.

[0043] Fig. 4a, b each shows a schematic representation of the gas flow pattern of a GGR shaft furnace in a longitudinal sectional view according to a further embodiment.

[0044] Fig. 5 shows a schematic representation of a GGR shaft furnace in a sectional view according to another embodiment.

[0045] Fig. 1 shows a GGR shaft kiln 1 with two parallel and vertically aligned shafts 2. The shafts 2 of the GGR shaft kiln 1 are essentially identical in design, so that in Fig. 1 only one of the two shafts 2 is fully provided with reference numerals and, for the sake of simplicity, only one of the two shafts 2 is described below. Each shaft 2 has a material inlet 3 for admitting 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 stone, preferably with a grain size of 10 to 200 mm, preferably 15 to 120 mm, most preferably 30 to 100 mm. The material inlets 3 are arranged, for example, at the upper end of the respective shaft 2, so that the material falls through the material inlet 3 into the shaft 2 due to gravity.The material inlet 3 is designed, for example, as an upper opening of the shaft 2 and in particular as a lock 3 and preferably extends over all or part of the cross-section of the shaft 2. A material inlet designed as a lock 3 is preferably configured such that only the raw material to be burned enters the shaft 2, but not the ambient air. The lock 3 is preferably designed such that it hermetically seals the shaft 2 against the environment and allows solids, such as the material to be burned, to enter the shaft.

[0046] Each shaft 2 further has a combustion gas inlet 12 at its upper end for admitting combustion gas for the combustion of fuels. The combustion gas is, for example, dedusted exhaust gas from at least one of the shafts 2, wherein the exhaust gas is optionally enriched with oxygen. Furthermore, each shaft 2 has an exhaust gas outlet 6 for discharging exhaust gases from the respective shaft 2. Each exhaust gas outlet 6 and combustion gas inlet 12 is assigned, for example, a control element. Using control elements, such as a quantity-adjustable compressor, the quantity of combustion gas into the respective combustion gas inlet 12 and the quantity of exhaust gas to be extracted via the respective exhaust gas outlet 6 can preferably be adjusted. The combustion gas inlet 12 and the exhaust gas outlet 6 are, for example, arranged at the same height and in particular within the preheating zone 21 of the respective shaft 2.

[0047] At the lower end of shaft 2, a material outlet 40 is arranged for removing the fired material. The material outlet 40 is, for example, a lock as described with reference to the material inlet 3. The fired material is, for example, guided into an outlet hopper 25, which is connected to the material outlet 40 of shaft 2. The outlet hopper 25 is, for example, funnel-shaped. The outlet hopper 25 preferably has a cooling gas inlet 23 for admitting cooling gas into the respective shaft 2. The cooling gas is preferably fed into the cooling gas inlet 23 by means of a compressor 33. During operation of the PFR shaft furnace 1, the material to be fired flows from top to bottom through the respective shaft 2, with the cooling air flowing from bottom to top, countercurrent to the material, through the respective shaft 2. The furnace exhaust gas is discharged from the shaft 2 through the exhaust gas outlet 6.

[0048] Below the material inlet 3 and the combustion gas inlet 12, in the direction of material flow, is the preheating zone 21 of the respective shaft 2. 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 burned. 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 surrounded, for example, by a refractory lining.

[0049] A plurality of burner lances 10 are optionally arranged in the preheating zone 21, each serving as an inlet for fuel, such as a fuel gas, oil, or ground solid fuel. The PGR shaft furnace 1 has, for example, a cooling device for cooling the burner lances 10. The cooling device comprises, for example, a plurality of cooling air ring lines that extend in a ring around the shaft region in which the burner lances 10 are arranged. Cooling air for cooling the burner lances 10 preferably flows through the cooling air ring lines. For example, the burner lances 10 are cooled by means of the exhaust gas discharged via the exhaust gas outlet 6. The exhaust gas outlet 6 is preferably connected to the burner lances 10 for conducting exhaust gas to the burner lances 10.

[0050] Preferably, a plurality of, for example, twelve or more, burner lances 10 are arranged in each shaft 2 and are substantially evenly spaced 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, in particular in the direction of flow of the material. The ends of the burner lances 10 of a shaft 2 are preferably all arranged at the same height. Preferably, the plane at 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 designed as a ring line that extends circumferentially around the respective shaft 2.Preferably, each shaft 2 has a fuel line assigned to the burner lances 10 of the shaft 2, which in particular has a control element for adjusting the amount of fuel to the burner lances 10.

[0051] The preheating zone 21 is followed by the combustion zone 20 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 combusted, and the preheated material is fired at a temperature of approximately 1000°C. The PFR shaft furnace 1 further comprises a connecting channel 19 for the gas connection of the two shafts 2. In particular, no material to be burned is present in the connecting channel 19.

[0052] Fig. 1 shows, by way of example, a GGR shaft furnace 1 with a direct connecting channel 19, which, for example, has a square shaft cross-section. For example, the shafts 2 of the GGR shaft furnace 1 have a triangular, square, rectangular, round, oval, polygonal, semi-circular, partially circular, or circular cross-section. The connecting channel 19 forms a direct gas connection between the two shafts 2, wherein the cooling gas from the combustion shaft 2a, together with the fuel gas from the combustion shaft 2a, flows directly into the connecting channel 19 and subsequently into the regenerative shaft 2b. Preferably, the GGR shaft furnace 1 of Fig. 1 does not have an annular channel 18, as described with reference to Figs. 3a and b. For example, the combustion zone 20 and the preheating zone 21 of the shafts 2 have a cross-section that is essentially constant over the shaft length.The outer wall of the shafts 2, which points radially outward away from the connecting channel, extends in particular exclusively vertically over the entire shaft length, in particular over the length of the combustion zone 20 and the cooling zone 22. The cooling zone 22 preferably has a cross-section that increases in the direction of the connecting channel 19 and opens into the connecting channel 19. Preferably, the sections z of the PFR shaft furnace 1 of Fig. 1 are completely filled with material, so that no material-free space is formed, in particular in the combustion zone 20 and the cooling zone 22.

[0053] Adjacent to the combustion zone 20 in each shaft 2, in the direction of material flow, is the cooling zone 22, which extends to the material outlet 40. The cooling zone 22 is formed, for example, in a shaft section with a substantially constant or downwardly decreasing cross-section. The material is cooled within the cooling zone 22 to approximately 100°C in countercurrent to the cooling gas flowing through the material. The cooling gas flowing into the cooling zone 22 via the cooling gas inlet 23 preferably flows entirely into the combustion zone 20 and preferably the preheating zone 21 of the respective shaft 2.

[0054] 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 the material to pass laterally between the discharge table and the casing wall of the PFR shaft kiln. The discharge device 41 is preferably designed as a pusher or rotary table, or as a table with a pusher clearer. This enables a uniform throughput rate of the firing material through the shafts 2. The discharge device 41 further comprises, for example, the outlet hopper 25, which adjoins the discharge table and at whose lower end the material outlet 40 is attached.

[0055] During operation of the GGR shaft kiln 1, one of the shafts 2 is active at a time, while the other shaft 2 is passive. The active shaft 2a is referred to as the combustion shaft and the passive shaft 2 as the regenerative shaft 2b. The GGR shaft kiln 1 is operated in particular cyclically, 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 swapped. This process is repeated continuously. Material such as limestone or dolomite stone is alternately fed into the shafts 2 via the material inlets 3. In the active shaft 2, operated as combustion shaft 2a, a fuel is introduced into the combustion shaft 2 via the burner lances 10. The material to be burned is heated in the preheating zone 21 of the combustion shaft za, preferably to a temperature of approximately 700°C. In the embodiment shown in Fig.1, the left shaft 2 is operated as combustion shaft 2a, while the right shaft 2 is operated as regenerative shaft 2b.

[0056] During operation of the PGR shaft furnace 1, the cooling gas flows in both the combustion shaft 2a and the regenerative shaft 2b in countercurrent to the material to be cooled through the cooling zone 22 and is preferably completely directed into the combustion zone 20.

[0057] Within the shaft 2 operated as a combustion shaft 2a, the combustion gas flows through the combustion gas inlet 12 into the combustion shaft and, in cocurrent with the material within the combustion zone 20, into the connecting channel 19 and then into the shaft 2 operated as a regenerative shaft 2b. Within the regenerative shaft 2b, the gas flows from the connecting channel 19 in countercurrent to the material to be burned through the combustion zone 20 into the preheating zone 21 and exits the regenerative shaft 2b through the exhaust gas outlet 6 of the regenerative shaft 2b. The exhaust gas discharged from the shaft 2 preferably has a temperature of 60°C to 160°C, preferably 100°C.

[0058] The exhaust gas is fed into an exhaust line 39 adjoining the exhaust gas outlet 6. The exhaust line 39 optionally has an exhaust filter 31 adjoining the exhaust gas outlet 6 in the flow direction of the exhaust gas for filtering fine particles, in particular dust, from the exhaust gas. The PGR 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 controlling 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 oxidant line 14 so that an oxidant, preferably air or pure oxygen, is introduced into the combustion gas inlet 12.It is also conceivable for the oxidizing agent to be 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 95 vol%, preferably 90 vol%. The combustion gas inlet 12 is preferably connected to an upstream control element, so that the oxidizing agent is preferably supplied only to the combustion gas inlet 12 of the shaft 2 operated as a combustion shaft 2a.

[0059] The exhaust line 39 has, for example, a compressor 34 and a cooling device 32 downstream of the exhaust filter 31. The exhaust gas is preferably discharged downstream of the cooling device 32. Preferably, the entire amount of CO2 from the calcination and combustion, as well as the water from the combustion, is discharged from the PFR shaft furnace 1. The cooling device 32 is, for example, a heat exchanger, which is preferably operated in countercurrent with a coolant, such as water.

[0060] The oxidant line 14 preferably has a control element, such as a valve or a flap, via which the amount of oxidant in the combustion gas inlet 12 can be adjusted.

[0061] The exhaust gas of the PGR shaft furnace of Fig. 1 preferably has a CO2 content of 30vol%-40vol%, in particular 35vol%.

[0062] The GGR shaft furnace 1 preferably has a cooling gas outlet 17 for discharging cooling gas from the shaft 2, in particular from the regenerative shaft 2b. The cooling gas outlet 17 is arranged, for example, in the preheating zone 21 of the GGR shaft furnace 1, in particular the regenerative shaft 2b. 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 it 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 guided out of 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 gas communication, so that the cooling gas can preferably flow through the cooling zone 22 and the combustion zone 20 into the preheating zone 21 and then through the cooling gas outlet 17. The cooling gas outlet 17 is preferably arranged in a region of the outer wall of the preheating zone 21 that faces away from the connecting channel 19. The cooling gas outlet 17 is preferably arranged in the outer wall of the shaft 2, in particular the regenerative shaft 2b, opposite the connecting channel 19.

[0063] During operation of the GGR shaft furnace 1, the cooling gas preferably flows from the cooling zone 22 into the combustion zone 20 and then, together with the exhaust gas from the combustion zone 20, through the combustion zone 20 into the preheating zone 21 and leaves the shaft 2, in particular the regenerative shaft 2b, through the cooling gas outlet 17 arranged in the preheating zone 21. Fig. 1 additionally shows the gas flow within the GGR furnace 1, with the CO2-containing combustion gas being represented by the black arrows and the oxygen-containing cooling gas being represented by the white arrows. According to a finding of the inventors, the oxygen-containing cooling gas flows in the regenerative shaft 2b along the outer wall of the regenerative shaft 2b opposite the connecting channel 19 into the combustion zone 20 and 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 very minimal mixing of the gas streams of the combustion gas and the cooling gas. Discharging the cooling gas via the cooling gas outlet in the preheating zone or the combustion zone offers the advantage over discharging the cooling gas from the cooling zone that the heat quantity of the cooling gas is additionally available to the PFR shaft furnace 1 in the combustion zone 20 and the preheating zone 21 for heating the material. In the PFR shaft furnace 1 according to the invention, the cooling air preferably flows through a large portion, in particular almost the entire portion, of the material bed and has a comparatively low outlet temperature. This leads to an optimal heat balance, whereby no additional height of the PFR shaft furnace 1 is required.Furthermore, a recuperator downstream of the cooling gas outlet for utilizing the waste heat can be dispensed with.

[0064] The cooling gas outlet 17 is preferably arranged downstream of the ends, in particular fuel outlets, of the burner elements 10 in the gas flow direction of the regenerative shaft 2b. The cooling gas outlet 17 is preferably arranged downstream of the exhaust gas outlet 6 in the material flow direction. The cooling gas outlet 17 is, for example, slot-shaped. In particular, the cooling gas outlet 17 extends horizontally, preferably across the entire width of the shaft outer wall. It is also conceivable for the cooling gas outlet 17 to have a plurality of openings extending through the outer wall of the shaft 2, in particular the preheating zone 21, which openings are arranged, for example, horizontally next to one another across the entire width of the outer wall of the shaft 2 and are preferably evenly spaced from one another.

[0065] The burner lances 10 have covers (not shown in Fig. 1, for example) that are arranged upstream of the inlets of the burner lances 10 in the respective shaft 2 in the direction of material flow. The covers are designed and arranged such that they protect at least the upper region of the burner lances 10 from contact, in particular from impact of the material on the burner lances 10. The cooling gas outlet 17 is preferably arranged below the cover, in particular downstream of the cover in the direction of material flow.

[0066] The shaft 2 preferably has a lining, which in particular comprises a refractory lining. The cooling gas outlet 17 is preferably arranged at the upper end region of the lining.

[0067] The GGR shaft furnace 1 preferably has a cooling gas exhaust line 11 connected to the cooling gas outlet 17 for directing the cooling air out of the shaft 2. The cooling gas exhaust line 11 is arranged outside the shaft and connected to a filter 16. The filter 16 is preferably a particle filter, in particular a dust filter. The cooling air exhausted via the cooling air outlet 17 preferably has a temperature of 200°C to 400°C. For example, the cooling air exhaust line 11 of the GGR shaft furnace 1 comprises a control element 8, such as a flap or a valve, for adjusting the amount of cooling air exhausted from the preheating zone 21 or the combustion zone 20 via the cooling gas outlet. For example, air is supplied to the cooling gas exhaust line 11 via a compressor or fan.For example, the cooling gas discharge line 11 comprises at least two control elements, each control element 8 being assigned to a respective cooling gas outlet 17 for adjusting the respective cooling gas quantity. Preferably, only the control element 8 assigned to the shaft 2 operated as a regenerative shaft 2b is open, while the control element 8 assigned to the combustion shaft 2a is closed. Downstream of the filter 16, the cooling gas is preferably discharged from the PFR shaft furnace 1. It is also conceivable for the cooling gas discharge line 11 to be connected to the oxidant line 14, in particular the combustion gas inlet 12, so that the discharged cooling air is fed to the 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 exhaust gas is discharged via the exhaust gas outlet and subsequently preferably post-treated or stored.

[0068] 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. For example, each cooling gas inlet 23 is assigned a control element 4, such as a flap or a valve, which is connected to the cooling gas supply line 7 for adjusting the amount of cooling gas supplied to the respective cooling gas inlet 23. Preferably, the control elements 4 are adjusted such that a smaller amount of cooling air is supplied to the combustion shaft 2a than to the regenerative shaft 2b. Preferably, approximately 20% to 30%, preferably 25%, of the total amount of cooling gas supplied to the PFR shaft furnace 1 is supplied to the combustion shaft 2a.

[0069] The PGR shaft furnace 1 of Fig. 1 preferably has an exhaust gas with a CO2 content of more than 30vol%.

[0070] Fig. 2 shows a further embodiment of a GGR shaft furnace, which largely corresponds to the GGR shaft furnace of Fig. 1. Identical elements are provided with the same reference numerals. In the GGR shaft furnace 1 of Fig. 2, the left shaft 2 is also operated as a combustion shaft 2a, for example. In contrast to the GGR shaft furnace of Fig. 1, the GGR shaft furnace 1 of Fig. 2 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 shaft 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, in particular downstream of the cooling device 32. The exhaust gas not fed to the combustion gas inlet 12 via the exhaust gas recirculation line 15 is preferably discharged from the PGR shaft furnace 1.The exhaust gas recirculation line 15 is connected, for example, to an oxidant line 14 for conveying an oxidant into the exhaust gas recirculation line 15. The oxidant is preferably air or pure oxygen. For example, the oxidant 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 95 vol%, preferably 90 vol%. The oxidant line 14 is preferably connected to an oxidant source and preferably has a control element for adjusting the amount of oxidant in the exhaust gas recirculation line 15.

[0071] The PGR shaft furnace 1 of Fig. 2, for example, has a heat exchanger 24 connected to the exhaust gas recirculation line 15 and the cooling air discharge line 11. Optionally, no heat exchanger 24 and preferably no fan for supplying air to the cooling gas discharge line 11 are provided. The PGR shaft furnace 1 of Fig. 1 preferably has an exhaust gas with a CO2 content of more than 70 vol%, in particular more than 75 vol%, whereby an exhaust gas with a CO2 content of approximately 50 vol% can preferably be achieved if the previously described heat exchanger 24 and preferably also the fan in the cooling gas discharge line 11 are omitted. With such a 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, the PGR shaft furnace described above can also be used to produce 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.

[0072] 3a and b show a further embodiment of a GGR shaft furnace 1, which largely corresponds to the GGR shaft furnace of FIGS. 1 and 2. Identical elements are provided with the same reference numerals. Fig. 8 shows a sectional view of the GGR shaft furnace at section AA shown in Fig. 3a. The cooling gas discharge line 11, the exhaust gas recirculation line 1 Ö, the fuel line 9 and the oxidant line 14 are not shown for the sake of simplicity. In contrast to the GGR shaft furnace of FIGS. 1 and 2, the GGR shaft furnace 1 of Fig. 3 has an indirect connecting channel 19. The combustion zone 20 extends, for example, in a shaft section with a substantially constant cross-section. The shaft section extends, for example, with its lower region into the upper region of the cooling zone 22, so that an annular channel 18 is formed between the combustion zone 20 and the cooling zone 22.The annular channel 18 forms a material-free space in which no material to be burned is arranged. The annular channel 18 preferably extends circumferentially around the lower region of the combustion zone 20. The shafts 2 of Fig. 3a, for example, each have an annular channel 18 which is connected to the connecting channel 19. The annular channel 18 is preferably arranged at the level of the connecting channel 19, so that the connecting channel 19 is designed as an indirect connecting channel. An indirect connecting channel 19 is understood to be a connecting channel which is gas-connected to an annular channel 18, so that the cooling gas flows together with the combustion gas from the combustion shaft 2a via the annular channel 18 of the combustion shaft 2a into the connecting channel 19 and then via the annular channel 18 of the regenerative shaft 2b into the regenerative shaft 2b.The cross-section of the shaft section of the cooling zone 22 is, for example, larger than the cross-section of the lower region of the combustion zone 20, so that at the upper end of the cooling zone 22 and adjacent to the combustion zone 20, another material-free space 18, in particular an annular shoulder in which no material is arranged, is formed. At the lower end of the cooling zone 22, a preferably conical flow device is arranged, which serves to guide the material toward the shaft wall.

[0073] The PGR shaft furnace 1 of Fig. 3a and b comprises, by way of example, a cooling gas extraction device 26 for conducting the cooling gas to the cooling gas outlet 17. The cooling gas extraction device 26 is preferably arranged at least partially or completely within the preheating zone 21. In particular, the cooling gas extraction device 26 extends radially outward from the vertical center axis of the shaft 2, in particular the preheating zone 21, to the cooling gas outlet 17 and is preferably connected thereto via gas communication. The cooling gas extraction device 26 preferably has a line 28, in particular a pipeline 28, which is connected to the cooling gas outlet 17 and extends at least partially or completely through the preheating zone 21 of the shaft 2, in particular the regenerative shaft 2b. The cooling gas extraction device 26 preferably also comprises an extraction hood 30, which is preferably arranged coaxially to the shaft 2 within the preheating zone 21.The extractor hood 30 preferably has a round, in particular circular, cross-section and is, for example, pot-shaped or funnel-shaped and preferably open downwards.

[0074] The shafts 2 of the PFR shaft furnace 1 shown in Figs. 3a and b preferably have a round, in particular circular, cross-section. The shafts may also have a fully circular, semicircular, or partially circular cross-section.

[0075] Fig. 4a shows the GGR shaft furnace of Figs. 1 and 2, and Fig. 4b shows the GGR shaft furnace 1 of Figs. 3a and b, illustrating the gas flows of the cooling air K and the combustion gases V. The GGR shaft furnace 1 of Fig. 4a has the direct connecting channel 19, so that the cooling air in the regenerative shaft 2b flows through the regenerative shaft 2b along the lateral outer wall opposite the connecting channel 19.

[0076] The PFR shaft furnace 1 shown in Fig. 4b has the indirect connecting duct 19, so that the cooling air in the regenerative shaft 2b flows through the regenerative shaft 2b along the vertical center axis of the shaft 2. Figs. 4a and b also show areas where the combustion gas mixes with the cooling gas. These areas are preferably very small, so that the exhaust gas has a very low oxygen content of approximately 10 vol% at most.

[0077] Fig. 5 shows a further embodiment of a GGR shaft furnace 1, which essentially corresponds to that of Fig. 2, wherein identical elements are provided with identical reference numerals. In contrast to the GGR shaft furnace of Fig. 2, the GGR shaft furnace 1 of Fig. 5 has an overflow channel 19, which comprises two connecting channels 19a and 19b. The connecting channels 19a and 19b are arranged, for example, parallel and separate from one another. For example, the connecting channels 19a and 19b are separated from one another in terms of gas flow by a special horizontal separating element 13, such as a partition wall. The shaft furnace 1 has, for example, a first connecting channel 19a, which in particular directly adjoins the combustion zone 20 and is preferably arranged above a second connecting channel 19b. The first connecting channel 19a is, for example, arranged and designed 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 in which no material to be burned is present. The second connecting channel 19b is preferably arranged below the first connecting channel 19a and, in particular, is directly fluidically connected to the cooling zone 22. The second connecting channel 19b is arranged and designed, for example, such that only the cooling gas from the cooling zone 22 can flow into the second connecting channel 19b.

[0078] The overflow channel 19, for example, forms a gas connection between the two shafts 2, wherein the cooling gas of the combustion shaft 2a, in particular separately from the fuel gas of the combustion shaft 2a, flows into the overflow channel 19 and subsequently into the regenerative 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, for example, as a direct connecting channel 19b.

[0079] Furthermore, the PGR shaft furnace 1 of Fig. 5 has, for example, 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 such that it temporarily stores a certain amount of exhaust gas before it is withdrawn from the buffer tank 45, for example, for further processing. For example, at least one fan is arranged upstream and downstream of the buffer tank in the direction of flow of the exhaust gas.List of reference symbols 1 GGR shaft furnace 2 Shaft 2a Combustion shaft 2b Regenerative shaft 3 Material inlet / lock 4 Control element 6 Flue gas outlet 7 Cooling gas supply line 8 Control element 9 Fuel line 10 Burner lances 11 Cooling gas discharge line 12 Combustion gas inlet 13 Separating element 14 Oxidant line 15 Flue gas recirculation line 16 Filter 17 Cooling gas outlet 18 Annular duct / material-free space 19 Connecting duct / overflow duct 19a, b Connecting ducts 20 Combustion zone 21 Preheating zone 22 Cooling zone 23 Cooling gas inlet 24 Heat exchanger 25 Outlet funnel 26 Cooling gas discharge device 28 Line 30 Flue hood 31 Flue gas filter 32 Cooling device 33, 34 Compressor 39 Flue gas line 40 Material outlet / lock 42 Buffer tank K Cooling air V Combustion air.

Claims

Patent claims 1. Co-current countercurrent regenerative shaft furnace (1) for burning and cooling material, such as carbonate rocks, with two shafts (2) which can be operated alternately as a burning shaft (2a) and as a regenerative shaft (2b) and are connected to one another by means of a connecting 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 PGR shaft furnace (1) has a cooling gas outlet (17) for discharging cooling gas from the shaft (2) and wherein the cooling gas outlet (17) is arranged in the preheating zone (21) or the burning zone (20).

2. Co-current countercurrent regenerative shaft furnace (1) according to claim 1, wherein the cooling gas outlet (17) is arranged in the outer wall of the shaft (2).

3. Cocurrent countercurrent regenerative shaft furnace (1) according to one of the preceding claims, wherein one or a plurality of burner lances (10) are arranged such that they open into the combustion zone (20) and wherein the cooling gas outlet (17) is arranged downstream of at least one of the mouths of the burner lances (10) in the gas flow direction of the regenerative shaft (2b).

4. Co-current countercurrent regenerative shaft furnace (1) according to one of the preceding claims, wherein each shaft (2) has a cooling gas outlet (17) and wherein each cooling gas outlet (17) is assigned a control element for adjusting the amount of cooling gas to be discharged via the cooling gas outlet (17), and wherein the control element (8) assigned to the cooling gas outlet (17) of the combustion shaft (2a) is closed.

5. Co-current countercurrent regenerative night furnace (1) according to one of the preceding claims, wherein the cooling gas outlet (17) is arranged in a region of the outer wall of the preheating zone (21) or the combustion zone (20) facing away from the connecting channel (19).

6. Co-current countercurrent regenerative shaft furnace (1) according to claim 5, wherein the cooling gas outlet (17) extends in the outer wall of the shaft (2) in the horizontal direction.

7. Co-current countercurrent regenerative shaft furnace (1) according to one of the preceding claims, wherein the GGR shaft furnace (1) has a cooling gas discharge device (26) which is connected to the cooling gas outlet (17) for conducting the cooling gas and extends from the central axis of the shaft (2) to the cooling gas outlet (17).

8. Co-current countercurrent regenerative shaft furnace (1) according to claim 7, wherein the cooling gas extraction device (26) comprises an extraction hood (30) and a line (28) connected to the latter for gas purposes.

9. Cocurrent countercurrent regenerative shaft furnace (1) according to one of the preceding claims, wherein the PGR shaft furnace (1) has a combustion gas inlet (12) connected to a combustion gas source comprising a combustion gas having an oxygen content of more than 60vol%, preferably more than 75vol%, in particular more than 80vol% to more than 95vol% oxygen.

10. Co-current countercurrent regenerative shaft furnace (1) according to one of the preceding claims, wherein each shaft (2) has a cooling gas inlet (23) to which a control element (4) is assigned for adjusting the amount of cooling gas supplied to the respective cooling gas inlet (23), and wherein the control elements (4) are adjusted such that a smaller amount of cooling air is supplied to the combustion shaft (2a) than to the regenerative shaft (2b).

11. A method for burning material, such as carbonate rocks, in a co-current countercurrent regenerative shaft furnace (1) having two shafts (2) which are operated alternately as a burning shaft and as a regenerative shaft and are connected to one another by means of a connecting channel (19), wherein the material flows 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 discharged from at least one of the shafts (2) via a cooling gas outlet (17) in the preheating zone (21) or the burning zone (20).

12. The method according to claim 11, wherein the cooling gas is discharged from the shaft (2) via a cooling gas outlet (17) arranged in the outer wall of the shaft (2).

13. The method according to claim 11 or 12, wherein the cooling gas is discharged from the regenerative shaft (2b).

14. Method according to one of claims 11 to 13, wherein the amount of cooling gas discharged from the regenerative shaft (2b) via the cooling gas outlet (17) is adjustable by means of a control element (8).

15. The method according to any one of claims 11 to 14, wherein a combustion gas having an oxygen content of more than 60vol%, preferably more than 75vol%, in particular more than 80vol% to more than 95vol% oxygen is supplied to the GGR shaft furnace (1).

16. Method according to one of claims 11 to 15, wherein a smaller amount of cooling air is supplied to the combustion shaft (2a) than to the regenerative shaft (2b).

17. The method according to any one of claims 11 to 16, wherein the cooling gas flowing centrally through the preheating zone (21) is discharged.

18. The method according to any one of claims 11 to 16, wherein the cooling gas flowing along the Cooling gas flowing from the outer wall of the preheating zone (21) is discharged.

Images