METHOD FOR SHAFT CONVERSION OF A DC-COUNTER-CURRENT REGENERATIVE SHAFT KINDER

Description

[0001] The invention relates to a method for the shaft control of a co-current counter-current regenerative shaft kiln (CCT kiln) in order to prevent mixing between the kiln exhaust gas and the lime cooling air. This allows the carbon dioxide concentration in the kiln exhaust gas to be maintained at a high level, thus simplifying separation.

[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 WO 2011 / 072894 A1, has two vertical, parallel shafts that operate cyclically. Firing takes place in only one shaft at a time, the firing shaft, while the other shaft serves 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 exhaust gas 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 oxidizer gas, with fuel being injected into the firing zone.

[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] To meet the quality requirements for high reactivity of quicklime, as demanded, for example, in steelworks, the temperatures in the combustion zone must not exceed 1100 °C, preferably 1000 °C. Furthermore, the demand for environmentally friendly quicklime production is also increasing, meaning that certain requirements regarding the CO₂ content of the exhaust gas for subsequent treatment must be met.

[0005] Therefore, counter-current regenerative shaft kilns were developed to generate exhaust gas with the highest possible carbon dioxide content, thus minimizing the effort required for separation. Such a counter-current regenerative shaft kiln and a process for firing carbonate rock are known from DE 10 2021 204 176. The counter-current regenerative shaft kiln (CRK) is used for firing and cooling materials such as carbonate rocks. The CRK comprises two shafts, which are operated alternately as firing shafts and regenerative shafts and are connected by a connecting 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 also has an exhaust gas outlet for releasing exhaust gas from the shaft.The at least one exhaust gas outlet is connected to a gas inlet for introducing gas into at least one shaft. Preferably, the GGR shaft furnace has a plurality of gas inlets for introducing exhaust gas drawn from at least one of the shafts.

[0006] During operation, it was discovered that during shaft reversal, a mixing occurs between the furnace exhaust gas and the lime cooling air, which temporarily reduces the carbon dioxide content in the exhaust gas.

[0007] From RU 2 724 835 C1 a process for roasting carbonate material in a countercurrent furnace with two shafts is known.

[0008] From DE 10 2004 002 043 A1 a process for burning granular, mineral fuel is known.

[0009] For example, a direct current countercurrent regenerative shaft furnace and a method for burning carbonate rock are known from DE 10 2021 204 176 A1.

[0010] The object of the invention is to provide a method for shaft reversal in which mixing between the furnace exhaust gas and the lime cooling air is largely avoided in order to prevent a decrease in the carbon dioxide content in the exhaust gas and thus to enable carbon dioxide separation in a simple manner.

[0011] This problem is solved by the method with the features specified in claim 1. Advantageous further developments are described in the dependent claims, the following description, and the drawings.

[0012] The method according to the invention serves for the shaft switching of a direct-current counter-current regenerative shaft kiln. In a direct-current counter-current regenerative shaft kiln (DCT kiln), one shaft is initially used as the firing shaft and the second shaft as the regenerative shaft. After a cycle, which can last, for example, between 10 and 60 minutes, particularly between 10 and 20 minutes, for example, 15 minutes, the shaft switching takes place, and the first shaft is then used as the regenerative shaft and the second shaft as the firing shaft. In conventional systems, the DC kiln was typically depressurized, the fired product was removed from the bottom, and the product to be fired was fed in from the top. The advantage of the DC kiln is that this alternating operation results in very efficient heat recovery, making the process very energy-efficient.The invention radically departs from this previous method of shaft reversal. Instead, a certain gas flow and thus pressure is maintained in the GGR shaft furnace, which ensures that the exhaust gas remains at a consistently high carbon dioxide concentration even during shaft reversal, so that separation, in particular subsequent liquefaction, remains easily possible.

[0013] The co-current counter-current regenerative shaft furnace used for the process according to the invention has a first shaft and a second shaft. The first shaft has a first preheating zone for preheating the material, a first combustion zone for firing the material, and a first cooling zone for cooling the material. The second shaft has a second preheating zone for preheating the material, a second combustion zone for firing the material, and a second cooling zone for cooling the material. The first combustion zone and the second combustion zone are connected via a connecting channel. The first preheating zone has a first combustion gas inlet, and the second preheating zone has a second combustion gas inlet. The first preheating zone has a first exhaust gas outlet, and the second preheating zone has a second exhaust gas outlet. The first combustion zone has at least one first firing lance, and the second combustion zone has at least one second firing lance.At least one first burning lance is connected to a first fuel supply and at least one second burning lance is connected to a second fuel supply.

[0014] The procedure consists of the following steps: a) Operating the first shaft as a combustion shaft and the second shaft as a regeneration shaft, b) Stopping the fuel supply through the first fuel inlet and thus carrying out the combustion in the first shaft, c) Closing the second exhaust outlet, after the start of step c) and before the end of step c) Starting with the following steps d) to f) d) Opening the second combustion gas inlet, e) Closing the first combustion gas inlet, f) Opening the first exhaust outlet, g) Starting the fuel supply through the second fuel inlet and thus operating the second shaft as a combustion shaft and the first shaft as a regeneration shaft.

[0015] It is therefore essential that the supply of combustion gas and the removal of exhaust gas are never interrupted. The GGR shaft furnace is thus not depressurized, i.e., brought down to ambient pressure. This, in turn, minimizes the mixing between the exhaust gas and the cooling gas, even during shaft reversal. In particular, it is possible to convey the cooling gas through the GGR shaft furnace in its unchanged form; specifically, the cooling gas supply does not need to be stopped or altered. This makes separating carbon dioxide from the exhaust gas very simple, as the carbon dioxide concentration remains consistently high.

[0016] Step a) corresponds to the normal firing process. Step b) also corresponds to the normal procedure.

[0017] In step c), the second exhaust gas outlet begins to close. This means that the GGR shaft furnace is not opened (i.e., brought to ambient pressure), but rather the pressure is maintained. While the second exhaust gas outlet is closing, the second combustion gas inlet opens in step d), the first combustion gas inlet closes in step e), and the first exhaust gas outlet opens in step f), all overlapping in time. The effect is that the pressure in the connecting channel can be kept relatively constant, which is a good indicator that mixing with the cooling gas is avoided.

[0018] While it was previously common practice to depressurize the GGR shaft furnace during changeover, simultaneously removing finished product from the bottom and feeding new feedstock from the top (where the furnace is already at ambient pressure), this is not the case with the method according to the invention. Here, in particular, the product removal and feedstock supply can be carried out independently of the changeover process, for example, via airlocks. Therefore, the method according to the invention does not need to be directly connected to the feedstock supply and / or product removal, but can be carried out separately.

[0019] According to the invention, steps d) and e) are performed synchronously. This can be achieved, for example, and preferably, via a switchable Y-type diverter valve. The gas flow to the combustion gas inlets is not interrupted, but rather supplied to the combustion gas inlet being opened to the same extent as the combustion gas inlet being closed. This allows the amount of gas flowing into the GGR shaft furnace to be kept constant during the switching process in a very simple manner. However, since steps c) and f) are not synchronous but staggered in time, the gas discharge is effectively reduced while the gas supply remains constant. This causes the pressure inside the GGR shaft furnace to rise, potentially preventing, for example, cooling gas from escaping the cooling zones.

[0020] In a further embodiment of the invention, steps d) to f) begin simultaneously. This is preferred and ensures a particularly consistent pressure in the connecting channel.

[0021] In a further embodiment of the invention, steps c), d), and e) have a first duration t1. Step f) has a second duration t2, wherein the second duration t2 is longer than the first duration t1. This results in a slower opening of the first exhaust gas outlet in step f). This, particularly in conjunction with the earlier start of the closing of the second exhaust gas outlet in step c), ensures that the GGR shaft furnace does not become depressurized, but rather that the pressure conditions, especially in the combustion zones, remain so stable that mixing with the cooling gases is reliably prevented.

[0022] In a further embodiment of the invention, the second time period t2 is 1.5 to 5 times longer than the first time period t1. Preferably, the second time period t2 is 2 to 3 times longer than the first time period t1.

[0023] According to the invention, step f) begins after the start and before the end of steps c), d) and e). Thus, although the gas discharge via the first exhaust outlet and the second exhaust outlet is permanently open, the gas discharge is initially reduced during the process, ensuring that the pressure inside the GGR shaft furnace rises rather than falls in a simple manner, thereby reliably preventing mixing with cooling air.

[0024] In a further embodiment of the invention, step c) has a first time duration t 1. Steps d), e) and f) begin 1 / 4 to 3 / 4 t 1, in particular 1 / 3 to 2 / 3 t 1, after the start of step c). For example, steps d), e) and f) begin exactly in the middle of step c), i.e. with a time offset of 1 / 2 t 1.

[0025] In a further embodiment of the invention, the supply and removal of cooling gas in the first and second cooling zones is continued continuously with a constant cooling gas flow rate. In particular, the gas flow rate is kept constant throughout all steps. This allows the flow and pressure profile in the first and second cooling zones to be maintained at a constant level.

[0026] In a further embodiment of the invention, the opening and closing in steps c), d), e) and f) takes place at a variable speed. In particular, the opening is initially slower and then accelerates over the course of the steps. In particular, the closing is initially faster and then slows down over the course of the steps.

[0027] In a further embodiment of the invention, a first pressure is measured in the upper gas region of the first shaft. A second pressure is then measured in the upper gas region of the second shaft. Optionally, the pressure in the connecting channel can also be measured. Measuring the pressure enables control based on the measured pressures.

[0028] In a further embodiment of the invention, the opening and closing speed in steps c), d), e), and f) is controlled such that the first pressure decreases at a constant first rate and / or the second pressure increases at a constant second rate. If only one pressure is controlled, the decreasing pressure is preferably controlled. This results in only a minimal pressure drop being detectable in the connecting channel, so that mixing with the cooling gas can be largely avoided.

[0029] In a further embodiment of the invention, the first rate is equal in magnitude to the second rate. The first and second rates have opposite signs. "Equal in magnitude" here is to be understood in a technical sense and not in a strictly mathematical sense. This achieves a synchronous switching of the gas flow in the first and second shafts of the GGR shaft furnace.

[0030] In a further embodiment of the invention, the first combustion gas inlet and the second combustion gas inlet are connected to a combustion gas line. The combustion gas line is connected to an oxidizer supply. In particular, the oxidizer supply can be connected to an air separation unit or another source of oxygen.

[0031] Preferably, oxygen with a purity of at least 90%, more preferably at least 95%, and more preferably at least 98%, is supplied via the oxidizing agent supply. After completion of steps c), d), e) and f) and before the start of step g), the oxidizing agent supply is opened.

[0032] In In another embodiment of the invention, the supply of oxidizing agent is closed during step b). Preferably, the closing of the supply of oxidizing agent is completed at the end of step b).

[0033] In In another embodiment of the invention, the opening speed is selected to increase in steps d) and f).

[0034] In In a further embodiment of the invention, the feedstock is supplied and the product is removed during step a). The supply and removal thus take place through a sluice gate in order to avoid negatively affecting either the gas composition or the pressure inside the GGR shaft furnace.

[0035] In In a further embodiment of the invention, the opening position of the first combustion gas inlet, the second combustion gas inlet, the first exhaust gas outlet, and the second exhaust gas outlet is detected. This allows the opening and closing speed to be actively controlled.

[0036] Furthermore, in the GGR shaft furnace, the gas inlet for carrying out the process can be arranged in the preheating zone of the shaft operated as a combustion shaft. The gas inlet in the preheating zone of the combustion shaft is preferably a combustion gas inlet, through which, in addition to the exhaust gas, an oxidizing agent is preferably introduced into the preheating zone. The gas inlet is preferably located at the upper end of the preheating zone.

[0037] Furthermore, in the GGR shaft furnace, the gas inlet for carrying out the process can be arranged in the connecting channel for the gas connection of the combustion zones of the shafts and / or in the combustion zone of the shaft, in particular the regeneration shaft, and / or in a material-free space within the shaft. In particular, the material-free space is designed as an outer annular space that extends circumferentially around, preferably, the upper area of ​​the cooling zone adjacent to the combustion zone.

[0038] Furthermore, in the GGR shaft furnace, a heat exchanger and / or a heating device, in particular an electric heating device, a solar heating device, or a combustion reactor, can be arranged between the exhaust gas outlet and the gas inlet in the connecting channel for the gas connection of the combustion zones of the shafts and / or in the combustion zone itself, to heat the exhaust gas. For example, the heat exchanger is arranged upstream of the heating device in the direction of exhaust gas flow. It is also conceivable that only a heat exchanger or a heating device for heating the exhaust gas is present.

[0039] Furthermore, in the GGR shaft furnace for carrying out the process, the cooling zone can have a cooling gas inlet for introducing cooling gas into the cooling zone and a cooling gas exhaust device for removing cooling gas from the shaft.

[0040] Furthermore, the GGR shaft furnace can have a material-free space within the cooling zone of the shaft for carrying out the process. In particular, the material-free space is designed as an external annular space that extends circumferentially around preferably the upper area of ​​the cooling zone adjacent to the combustion zone. The cooling gas outlet is located in this material-free annular space.

[0041] The material-free space of the cooling gas extraction device is, for example, designed as an inner cylinder that extends, in particular centrally and vertically, through the cooling zone. Specifically, the inner cylinder extends at least partially into the combustion zone. The cooling gas outlet for venting the cooling gas from the shaft is located within the inner cylinder. The inner cylinder preferably has a cooling gas inlet for introducing cooling gas from the cooling zones into the interior of the inner cylinder, the cooling gas inlet being preferably located below the cooling gas outlet within the inner cylinder. In particular, the cooling gas inlet is located at the lower end of the cooling zone, so that the cooling gas preferably flows through the entire cooling zone and then into the inner cylinder of the cooling gas extraction device. Within the inner cylinder, the cooling gas preferably flows downwards towards the cooling gas outlet and into the cooling gas extraction line.A cooling gas extraction device designed as an internal cylinder enables a low overall height of the cooling zone and a comparatively simple conversion of known GGR shaft furnaces.

[0042] The material-free space of the cooling gas extraction device is designed, for example, as a connecting channel for the gas connection of the cooling zones of the two shafts, with the cooling gas outlet preferably being arranged in the connecting channel, in particular centrally.

[0043] The cooling gas exhaust device is preferably designed to release all the cooling gas from the shaft, so that preferably no cooling gas enters the combustion zone or the connecting channel for linking the combustion zones of the shafts. In particular, the cooling gas exhaust device is connected to a control element, such as a flap or a valve, for adjusting the amount of cooling gas to be extracted.

[0044] Furthermore, in the GGR shaft furnace, the cooling gas exhaust system can be connected to a heat exchanger for heating the exhaust gas. The cooling gas exhaust system is connected to the heat exchanger, in particular via the cooling gas exhaust line. The heat exchanger preferably serves to heat the exhaust gas that has been discharged from the preheating zone of the regeneration shaft via the exhaust gas outlet. The heat exchanger is specifically connected to the exhaust gas outlet and the cooling gas outlet of the cooling gas exhaust system.

[0045] Furthermore, in the GGR shaft furnace for carrying out the process, each shaft can have a combustion gas inlet for introducing combustion gas into the preheating zone and / or the combustion zone, wherein the combustion gas inlet is connected to an oxidizer line for conveying an oxidizer into the shaft. The combustion gas inlet is preferably connected to the exhaust gas outlet for conveying the exhaust gas into the shaft.

[0046] For example, the method can be implemented using a control system for a direct-current counter-current regenerative shaft furnace, which is configured to execute the method according to the invention. Preferably, the control system includes executable program instructions for carrying out the method according to the invention. The control system is thus not only suitable but also capable of executing the method according to the invention.

[0047] The method according to the invention is explained in more detail below with reference to an embodiment shown in the drawings. Fig. 1 first exemplary GGR shaft furnace for carrying out the process Fig. 2 second exemplary GGR shaft furnace for carrying out the process Fig. 3 entire cycle Fig. 4 Shaft rerouting Fig. 5 Pressure profile during shaft reversing

[0048] The figures and reference symbols do not differentiate between the first and second shafts. With each cycle, the functions between the two shafts are exchanged, making a common reference symbol for both the first and second shafts, as well as their corresponding components, useful.

[0049] 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 designated with a reference numeral, and for the sake of simplicity, only one of the two shafts 2 will be 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 through the material inlet 3 by gravity. 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.

[0050] 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, the exhaust gas preferably being 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 optionally 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 the control elements, such as a variable-flow compressor 35. The combustion gas inlet 12 and the exhaust gas outlet are optionally arranged at the same height and, in particular, within the preheating zone 21 of the respective shaft 2.

[0051] 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 by means of a compressor 33.

[0052] During operation of the GGR shaft furnace 1, the material to be burned 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 furnace exhaust gas is discharged from the shaft 2 through the exhaust gas outlet 6.

[0053] Below the material inlet 3 and the combustion gas inlet 12, the preheating zone 21 of the respective shaft 2 adjoins the 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 material flow direction are, for example, surrounded by a refractory lining.

[0054] In the preheating zone 21, a plurality of burner lances 10 are optionally arranged, each serving as an inlet for fuel, such as a fuel gas, oil, or ground solid fuel. The GGR shaft furnace 1, for example, has 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 shape around the shaft area in which the burner lances 10 are arranged. Cooling air preferably flows through the cooling air ring lines to cool the burner lances 10. Preferably, the burner lances 10 are cooled by means of the exhaust gas discharged via the exhaust gas outlet 6. Preferably, the exhaust gas outlet 6 is connected to the burner lances 10 to direct exhaust gas to the burner lances 10.

[0055] Preferably, a plurality, for example twelve or more, of burner lances 10 are arranged in each shaft 2 at substantially uniform intervals. 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 of 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 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 each has a control device for adjusting the amount of fuel to the burner lances 10.

[0056] The combustion zone 20 adjoins the preheating zone 21 in the direction of material flow. In In combustion zone 20, the fuel is burned and the preheated material is fired at a temperature of approximately 1000 °C. The GGR shaft furnace 1 also has a connecting channel 19 for gas-technical connection of the two shafts 2. In In particular, there is no combustible material present in connecting channel 19.

[0057] The Fig. 1 Figure 1 shows an example of a GGR lime kiln 1 with round shaft cross-sections. However, the shaft cross-section can have a different geometric shape, such as round, semicircular, oval, square, or polygonal. 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, with a shaft 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, forming an annular channel 18 between the two shaft sections. The annular channel 18 forms a material-free space in which no material to be burned is located.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 annular channel 18 preferably extends circumferentially around the lower region of the first shaft section of the combustion zone 20. The shafts 2 of the . Fig. 1 For example, each has a ring channel 18 which is connected to the connecting channel 19.

[0058] In each shaft 2, a cooling zone 22 adjoins the combustion zone 20 in the direction of material flow and extends to the material outlet 40. The cooling zone is formed in a shaft section with a cross-section that is essentially constant or decreases downwards. The cross-section of the shaft section of the cooling zone 22 is larger than the cross-section of the lower part of the combustion zone 20, so that a further material-free space 17, in particular an annular step, is formed at the upper end of the cooling zone 22 and adjacent to the combustion zone 20. Within the cooling zone 22, the material is cooled to approximately 100 °C in countercurrent flow of cooling gas. A preferably conical flow device is arranged at the lower end of the cooling zone 22, which serves to direct the material towards the shaft wall.

[0059] Each cooling zone 22 has a cooling air outlet device 17, each with a cooling gas outlet 29. In the exemplary embodiment of the Fig. 1 The cooling air outlet device 17 is designed as a material-free, in particular annular, space 17. The cooling gas outlet 29 is preferably arranged in the shaft wall of the material-free space 17 at the upper end of the cooling zone 22. The cooling gas flowing into the cooling zone 22 via the cooling gas inlet 23 preferably flows completely out of the cooling gas outlet 29 of the cooling air outlet device 17 from the respective shaft 2.

[0060] 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 whose lower end the material outlet 40 is located.

[0061] In the 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 2 is referred to as the firing shaft, and the passive shaft 2 as the regeneration shaft. The GGR shaft kiln 1 is operated 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 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, which is operated as the firing shaft, fuel is introduced into the firing shaft 2 via the burner lances 10. The material to be fired is heated to a temperature of approximately 700 °C in the preheating zone 21 of the firing shaft. In the exemplary embodiment of the Fig. 1 The left shaft 2 will be operated as a combustion shaft, while the right shaft 2 will be operated as a regeneration shaft.

[0062] 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 2 and the regeneration shaft 2 and is preferably completely discharged from the shaft 2 via the cooling gas outlet 29, so that preferably no cooling gas flows from the cooling zone 22 into the combustion zone 20.

[0063] Within shaft 2, which is operated as a combustion shaft, 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 material-free space designed as an annular channel 18. From the material-free space 18, the gas flows via the connecting channel 19 into shaft 2, which is operated as a regeneration shaft. Within the regeneration shaft, the gas flows from the connecting channel 19 and the material-free space 18 of the regeneration shaft, countercurrent to the material to be burned, through the combustion zone 20 into the preheating zone 21 and exits the regeneration shaft through the exhaust gas outlet 6 of the regeneration shaft. Preferably, the exhaust gas discharged from shaft 2 has a temperature of 60 °C to 160 °C, preferably 100 °C.

[0064] The exhaust gas is routed into an exhaust gas line 39 connected to the exhaust gas outlet 6. Downstream of the exhaust gas outlet 6, the exhaust gas line 39 optionally includes an exhaust gas filter 31 for filtering fine particles, particularly dust, from the exhaust gas. Downstream of the exhaust gas filter 31, the exhaust gas line 39 has a branch, whereby a portion of the exhaust gas is routed in a combustion gas line 4 to the combustion gas inlet 12. Downstream of the branch, the combustion gas line 4 includes, for example, a control element, such as a throttle valve, and a compressor 35, in the direction of exhaust gas flow. The combustion gas line 4 is preferably connected to the combustion gas inlets 12 of the shaft 2, whereby, via a control element upstream of the combustion gas inlet 12, the exhaust gas is preferably supplied only to the combustion gas inlet 12 of the shaft 2, which is operated as a combustion shaft.The combustion gas line 4 is preferably connected to an oxidizing agent line 14, so that an oxidizing agent, preferably pure oxygen, is introduced into the combustion gas line 4 and subsequently, together with the exhaust gas, into the shaft 2 via the combustion gas inlet 12. It is also conceivable that an oxygen-rich gas with an oxygen content of at least 70 to 95%, preferably 90%, is introduced into the combustion gas line 4 as the oxidizing agent.

[0065] The portion of the exhaust gas that is not returned to the combustion gas inlet 12 is fed into a gas inlet 15 in the connecting channel 19 of the exhaust gas line 39. Downstream of the branch of the combustion gas line 4, in the direction of exhaust gas flow, the exhaust gas line 39 preferably has a flow-controllable compressor 36, a heat exchanger 43, and optionally a heating device 8 for heating the exhaust gas. The heat exchanger 43 is, for example, designed as a recuperator, in which the exhaust gas is heated in counterflow to the extracted cooling gas, and the cooling gas is simultaneously cooled. The heat exchanger 43 is connected, in particular, via a cooling gas discharge line 11 to the cooling gas outlets 29 of both shafts 2, so that the exhaust gas is heated in the heat exchanger 43 by means of the extracted cooling gas, preferably in counterflow.Downstream of the heat exchanger, the coolant exhaust line 11 optionally includes a control device for adjusting the amount of coolant to be extracted and a filter 16 for removing dust from the coolant. The exhaust gas is heated in the heat exchanger 43 and / or the heating device 8, preferably to a temperature of approximately 900 °C to 1100 °C, particularly 1000 °C. It is also conceivable that the exhaust line 39 comprises only a heat exchanger 43 or a heating device 8 for heating the exhaust gas. For example, the exhaust gas is heated in the heat exchanger 43 to a temperature of approximately 600 °C and then in the heating device 8 to a temperature of approximately 1000 °C.

[0066] The heating device 8 is, for example, an electrically operated heating device. In particular, the heating device is operated using solar energy. It is also conceivable that the heating device 8 comprises a heat exchanger, wherein the heat transfer medium flowing in counterflow is heated by solar energy. The heating device 8 is preferably designed as a combustion reactor for the combustion of preferably renewable energy sources, such as wood, wherein the combustion preferably takes place in such a way that the combustion gas has a high CO₂ content of at least 90%.

[0067] Upstream of the heat exchanger 43, a portion of the exhaust gas is diverted and discharged via a cooling device 32 by means of a compressor 37. Preferably, the entire CO₂ quantity from the calcination and combustion, as well as the water from the combustion, is discharged from the GGR shaft furnace 1. The cooling device 32 is, for example, a heat exchanger, which is preferably operated in counterflow with a coolant such as water. The exhaust gas line has, by way of example, a compressor 34, 36, both before and after the diversion of the exhaust gas to be discharged.

[0068] The connecting channel 19 has a gas inlet 15 for introducing recirculated exhaust gas into the connecting channel 19. The gas inlet 15 is connected to the exhaust gas outlet 6 of the shaft 2 via the exhaust pipe 39, so that dedusted and heated exhaust gas discharged from the shaft 2 is directed into the connecting channel 19. The gas inlet 15 is shown, by way of example, arranged centrally in the upper wall of the gas channel 19. It is also conceivable that the gas inlet 15 is arranged at a different position in the wall of the connecting channel 19 or in the annular channels 18. It is also conceivable that a plurality of gas inlets 15 are installed in the connecting channel 19 or in the annular channels 18, each connected to the exhaust pipe 39.

[0069] Fig. 1 Figure 45 further shows two gas analysis devices 45 and 46 as examples. The gas analysis devices 45 and 46 are designed to determine the oxygen and / or CO₂ content of the respective gas. One gas analysis device 45 is arranged, for example, in the exhaust gas line 39 downstream of the branch of the combustion gas line 4 and is designed to determine the oxygen and / or CO₂ content of the exhaust gas. The gas analysis device 45 is connected, in particular, to a control device (not shown) for transmitting the determined oxygen and / or CO₂ content of the exhaust gas.

[0070] The oxidizer line 14 preferably has a control element, such as a valve or a flap, by which the amount of oxidizer in the combustion gas line 4 can be adjusted. The control element is preferably connected to the control device, the control device being configured in particular to regulate the amount of oxidizer in the combustion gas line 4 depending on the oxygen and / or CO₂ content of the exhaust gas determined by means of the gas analysis device 45.

[0071] The control system primarily serves to ensure complete combustion of the fuel, which is supplied to the GGR shaft furnace 1 via fuel line 9. This prevents an undesirably high oxygen content in the exhaust gas line 39. The CO₂ content in the exhaust gas line 39 is also measured to monitor the desired CO₂ level.

[0072] The control device is preferably designed such that it compares the oxygen and / or CO2 content determined by means of the gas analysis device 45 with a respective predetermined limit value or limit range and, in the event of a deviation of the determined value from the limit value or limit range, increases or decreases the amount of oxidizing agent in the combustion gas line.

[0073] Preferably, the amount of oxidizing agent is increased if the limit or limit range of the determined oxygen content is not reached. Preferably, the amount of oxidizing agent is decreased if the limit or limit range of the determined oxygen content is exceeded.

[0074] A gas analysis device 46 is arranged, for example, in the cooling gas discharge line 11, in particular downstream of the heat exchanger 43 and, for example, the filter 16, and is designed to determine the oxygen and / or CO₂ content of the discharged cooling gas. The gas analysis device 46 is connected, in particular, to the control device (not shown) for transmitting the determined oxygen and / or CO₂ content of the cooling gas.

[0075] The cooling gas discharge line 11 preferably has a control element, such as a valve or a flap, by which the amount of cooling gas to be discharged via the cooling gas discharge device 17 can be adjusted. The control element is preferably connected to the control device, the control device being designed in particular to regulate the amount of cooling gas discharged via the cooling gas discharge device 17 as a function of the oxygen and / or CO₂ content of the cooling gas determined by means of the gas analysis device 46.

[0076] The regulation serves in particular to ensure the most complete possible extraction of the cooling gas from the GGR shaft furnace 1 while simultaneously minimizing or preferably eliminating CO 2 in the cooling gas extraction line 11.

[0077] The control device is preferably designed such that it compares the oxygen and / or CO2 content determined by means of the gas analysis device 46 with a respective predetermined limit value or limit range and, in the event of a deviation of the determined value from the limit value or limit range, increases or decreases the amount of cooling gas to be discharged via the cooling gas discharge device 17.

[0078] Preferably, the amount of refrigerant is increased when the limit or limit range of the determined CO₂ content is undershot. Preferably, the amount of refrigerant is decreased when the limit or limit range of the determined CO₂ content is exceeded.

[0079] Fig. 2 shows another embodiment of a GGR shaft furnace, which is largely based on the GGR shaft furnace of the Fig. 1 This corresponds to the following: Identical elements are marked with the same reference symbols. In the GGR shaft furnace 1 of the Fig. 2 For example, the left shaft 2 is operated as a firing shaft. In contrast to the GGR shaft kiln of the Fig. 1 The GGR shaft furnace 1 of the Fig. 2 a cooling gas exhaust device 17 comprising an inner cylinder 26 extending at least partially from the cooling zone 22 into the combustion zone 20 and having a cooling gas outlet 29 connected to the cooling gas exhaust line 11.

[0080] Cooling zone 22 is exemplified in a shaft section with an approximately constant cross-section, where the shaft cross-section of cooling zone 22 corresponds to the shaft cross-section of the lower region of combustion zone 20. The material-free annular space of the GGR shaft furnace of the Fig. 1 , is therefore in the exemplary embodiment of the Fig. 2 not trained. Each shaft 2 of the GGR shaft furnace 1 of the Fig. 2 The inner cylinder 29 has an inner cylinder 29 that extends centrally and vertically through the cooling zone 22. For example, the inner cylinder 29 extends from the discharge device 41 through the cooling zone 22 into the combustion zone 20 up to the level of the connecting channel 19. To cool the inner cylinder 29, a plurality of cooling air channels are formed in its outer walls, which are connected to a cooling air line 7 for conveying cooling air. The cooling air is preferably directed by means of a compressor 38 via the cooling air line 7 into the cooling air channels of the inner cylinder 26. The heated cooling air is directed, for example, into the cooling gas exhaust line 11 and preferably into the heat exchanger 43 to heat the exhaust gas. The inner cylinders 26 each have a cooling air inlet 27 extending radially outwards and a cooling air outlet 28, which are connected to the cooling air line 7.

[0081] The inner cylinder 26 of the cooling gas exhaust device 17 has a cooling gas outlet 29 that extends radially outward from the inner cylinder 26 through the shaft wall and serves to direct cooling gas from the inner cylinder into the cooling gas exhaust line 11. 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. For example, each inner cylinder 26 has four cooling gas inlets 30, each formed at the same height in the inner cylinder wall and preferably spaced evenly apart from one another, extending outward in a star shape into the cooling zone 22. The cooling gas inlet 30 is preferably arranged above the cooling gas outlet 29 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 17. Preferably, all of the cooling gas introduced into the cooling zone 22 flows through the cooling gas inlets 30 into the cooling gas exhaust device 17, so that no cooling gas enters the combustion zone 20. The cooling air outlet 29 of the inner cylinder 26 is preferably located in the lower region of the cooling zone 22. The cooling gas flows, in particular, downwards from the cooling gas inlet 30 in the inner cylinder 26 to the cooling gas outlet 29.

[0082] In the exemplary embodiment, the routing of the cooling gas extracted from cooling zone 22 and the exhaust gas extracted from preheating zone 21 correspond to the Fig. 2 which with reference to Fig. 1 described wiring.

[0083] In Fig. 3 The timeline of a cycle V is shown. Further cycles V are indicated by dashed lines before and after cycle V. A cycle V lasts, for example, 15 minutes. The cycle V is divided into a combustion time W and a combustion chamber reversal X. The combustion time W is further subdivided into a fuel dosing time Y, during which the fuel is introduced into the combustion chamber, and a burn-out time Z, during which no further fuel is introduced into the combustion chamber, but an oxygen-containing gas continues to be supplied so that the fuel still contained in the combustion chamber can burn off.

[0084] Fig. 4 Now consider the steps taken during the in Fig. 3 The shaft control X shown in the diagram is used to demonstrate the inventive method using a specific example. The shaft control X begins with the closing of the second exhaust outlet D, which takes 4 seconds in the example shown. After 2 seconds, the opening of the second combustion gas inlet E, the closing of the first combustion gas inlet F, and the opening of the first exhaust outlet G begin simultaneously. The opening of the second combustion gas inlet E and the closing of the first combustion gas inlet F both take the same amount of time, as does the closing of the second exhaust outlet D, which takes 4 seconds. The opening of the first exhaust outlet G is slower and takes 10 seconds in the example shown. Following this, the oxidizer supply H begins. The next cycle V begins with the start of the fuel supply I.

[0085] In Fig. 5The pressure profile at the upper end of the first shaft U, the pressure profile at the upper end of the second shaft S, and the pressure profile in the connecting channel T along the shaft reversal process are shown. Initially, the pressure in the first shaft, which is operated as a combustion shaft, is higher, for example, at 1.3 bar. The pressure in the second shaft, which is operated as a regeneration shaft, is lower, at approximately 1 bar. The pressure in the connecting channel T lies between these two, at approximately 1.25 bar. The method according to the invention achieves a pressure decrease in the first shaft at a rate v while simultaneously the pressure in the second shaft increases at a rate v. It is graphically evident that this does not refer to a mathematically identical rate v, but rather to a rate v that is equal to a technically practical and controllable extent. Similarly, the constancy is not achieved in a purely mathematical sense, but rather to the extent that is technically feasible.It is clearly evident that this only approximates the technically normal pressure fluctuations and cannot be interpreted in strictly mathematical terms. However, apart from a very small drop in pressure in the connecting channel T at the point where the pressure in the first shaft U and the pressure in the second shaft S cross, the pressure in the connecting channel T remains constant, thus largely preventing mixing with the cooling air. Ultimately, the second shaft, now operating as a combustion shaft, has the higher pressure of approximately 1.3 bar, while the shaft now operating as a regeneration shaft has the lower pressure of approximately 1 bar. Reference sign

[0086] 1GGR shaft furnace 2 Shaft 3 Material inlet / airlock 4 Combustion gas line 6 Exhaust gas outlet 7 Cooling air line 8 Heating unit 9 Fuel line 10 Burner lances 11 Cooling gas exhaust line 12 Combustion gas inlet 14 Oxidizing agent line 15 Gas inlet 16 Filter 17 Material-free space / Cooling gas exhaust unit 18 Ring duct / Material-free space 19 Connecting duct 20 Combustion zone 21 Preheating zone 22 Cooling zone 23 Cooling gas inlet 25 Outlet hopper 26 Inner cylinder 27 Cooling air inlet 28 Cooling air outlet 29 Cooling gas outlet 30 Cooling gas inlet 31 Exhaust gas filter 32 Cooling unit 33 - 38 Compressor 39 Exhaust gas line 40 Material outlet / airlock 41 Discharge unit 42a,b Connection channels 43 Heat exchanger / recuperator 45, 46 Gas analysis unit

Claims

1. A method for shaft switchover in a parallel flow regenerative shaft kiln (1), in which the shaft kiln is not depressurized during shaft switchover, wherein the parallel flow regenerative shaft kiln (1) has a first shaft (2) and a second shaft (2), wherein the first shaft (2) has a first preheating zone (21) for preheating the material, a first burning zone (20) for burning the material and a first cooling zone (22) for cooling the material, wherein the second shaft (2) has a second preheating zone (21) for preheating the material, a second burning zone (20) for burning the material and a second cooling zone (22) for cooling the material, wherein the first burning zone (20) and the second burning zone (20) are connected via a connecting channel (19), wherein the first preheating zone (21) has a first combustion gas inlet (12) and the second preheating zone (21) has a second combustion gas inlet (12), wherein the first preheating zone (21) has a first exhaust gas outlet (6) and the second preheating zone (21) has a second exhaust gas outlet (6), wherein the first burning zone (20) has at least one first burning lance and the second burning zone (20) has at least one second burning lance, wherein the at least one first burning lance is connected to a first fuel feed and the at least one second burning lance is connected to a second fuel feed, the method comprising the following steps: a) operating the first shaft (2) as a burning shaft and the second shaft (2) as a regenerative shaft, b) stopping the fuel supply through the first fuel feed and thus carrying out burnout in the first shaft (2), c) closing the second exhaust gas outlet (6), after the start of step c) and before the end of step c), starting the following steps d) to f) d) opening the second combustion gas inlet (12), e) closing the first combustion gas inlet (12), f) opening the first exhaust gas outlet (6), g) starting the fuel supply through the second fuel feed and thus operating the second shaft (2) as a burning shaft and the first shaft (2) as a regenerative shaft, wherein steps d) and e) are carried out synchronously, wherein step f) starts after the start and before the end of steps c), d) and e).

2. The method as claimed in claim 1, characterized in that steps d) to f) start at the same time.

3. The method as claimed in any of the preceding claims, characterized in that steps c), d) and e) have a first length of time t1, and step f) has a second time length of time t2, the second length of time t2 being longer than the first length of time t1.

4. The method as claimed in claim 3, characterized in that the second length of time t2 is 1.5 to 5 times as long as the first length of time t1.

5. The method as claimed in any of the preceding claims, characterized in that step c) has a first length of time t1, and steps d), e) and f) start 1 / 4 t1 to 3 / 4 t1 after the start of step c).

6. The method as claimed in any of the preceding claims, characterized in that the supply of cooling gas and the discharge of cooling gas in the first cooling zone (22) and in the second cooling zone (22) is continued continuously at a constant flow of cooling gas.

7. The method as claimed in any of the preceding claims, characterized in that the opening and closing in steps c), d), e) and f) is carried out at variable speed.

8. The method as claimed in any of the preceding claims, characterized in that a first pressure is measured in the upper gas region of the first shaft (2) and in that a second pressure is measured in the upper gas region of the second shaft (2).

9. The method as claimed in claim 6 in combination with claim 7, characterized in that the speed of opening and closing in closing in steps c), d), e) and f) is controlled such that the first pressure falls at a constant first rate and / or the second pressure rises at a constant second rate.

10. The method as claimed in claim 9, characterized in that the first rate is identical in terms of absolute value to the second rate, the first rate and the second rate having opposite signs.

11. The method as claimed in any of the preceding claims, characterized in that the first combustion gas inlet (12) and the second combustion gas inlet (12) are connected to a combustion gas line (4), the combustion gas line (4) being connected to an oxidizing agent supply, the oxidizing agent supply being opened after completion of steps c), d), e) and f) and before the start of step g).

12. The method as claimed in claim 11, characterized in that the oxidizing agent supply is closed during step b).

13. The method as claimed in claim 12, characterized in that the closing of the oxidizing agent supply has been completed when step b) is ended.

14. The method as claimed in any of the preceding claims, characterized in that a rising opening speed is selected for the opening speed in steps d) and f).

15. The method as claimed in any of the preceding claims, characterized in that the feeding of reactant and the removal of product are carried out during step a).

16. The method as claimed in any of the preceding claims, characterized in that the opening position of the first combustion gas inlet (12), the second combustion gas inlet (12), the first exhaust gas outlet (6) and the second exhaust gas outlet (6) is detected.