Method for switching kiln bodies in parallel flow regeneration shaft kiln

Abstract

The invention relates to a method for switching kiln bodies in a co-current regenerative shaft kiln (1), comprising the following steps: a, operating a first kiln body (2) as a combustion kiln body and a second kiln body (2) as a regenerative kiln body, b, stopping the supply of fuel through a first fuel supply line, thereby causing the fuel in the first kiln body (2) to burn out, c, closing a second exhaust gas outlet (6), after the start of step c and before the end of step c, the following steps d to f are started: 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 supply line, whereby the second kiln body (2) is operated as a combustion kiln body and the first kiln body (2) is operated as a regeneration kiln body.

Description

[0001] The present invention relates to a method for kiln switching in a parallel flow regeneration shaft kiln (PFR shaft kiln) to avoid mixing between kiln exhaust gas and lime cooling air. This keeps the carbon dioxide concentration in the kiln exhaust gas at a high level, thus simplifying the removal process.

[0002] Carbonate rock has been burned in PFR shaft kilns for about 60 years. Such a PFR shaft kiln, known, for example, from WO 2011 / 072894 A1, has two vertical, parallel kiln bodies, which are operated in a cyclic manner, with combustion taking place only in one of the kiln bodies, which becomes the combustion kiln body, while the other kiln body is operated as a regeneration kiln body. The combustion kiln body is supplied with oxidizing gas flowing parallel to the material and the fuel, and the hot exhaust gases produced are introduced into the exhaust kiln body together with the heated cooling air supplied from below through cross-channels, where they are directed upwards in counter-flow to the material and preheat the material in the process. The material is usually fed into the kiln body from above together with the oxidizing gas, and the fuel is injected into the combustion zone.

[0003] In each kiln body, the material to be burned usually passes through a preheating zone to preheat the material, then passes through a combustion zone to burn the material, and finally passes through a cooling zone to supply cooling air to the hot material.

[0004] In order to meet the quality requirements of high reactivity of burnt lime, for example in steel mills, the temperature in the combustion zone must not exceed 1100 ° C, preferably 1000 ° C. In addition, the demand for environmentally friendly production of slaked lime is increasing, so certain requirements for the CO2 content of the waste gases must be met in subsequent aftertreatment.

[0005] Therefore, a parallel flow regeneration shaft kiln was developed to produce exhaust gas with the highest possible carbon dioxide content, thereby minimizing the removal work. DE 10 2021 204 176 discloses such a parallel flow regeneration shaft kiln and a method for burning carbonate rocks. The parallel flow regeneration shaft kiln (PFR shaft kiln) is used to burn and cool materials such as carbonate rocks. The PFR shaft kiln comprises two kiln bodies, which are operated alternately as a combustion kiln body and a regeneration kiln body and are connected to each other by a connecting channel. Each kiln body has a preheating zone for preheating materials, a combustion zone for burning materials, and a cooling zone for cooling materials in the direction of material flow. Each kiln body also has an exhaust gas outlet for discharging exhaust gas from the kiln body. At least one exhaust gas outlet is connected to a gas inlet for allowing gas to enter at least one kiln body. Preferably, the PFR shaft kiln has a plurality of gas inlets for allowing exhaust gas to be extracted from at least one kiln body.

[0006] During operation, it was found that mixing of kiln exhaust gas and lime cooling air occurred during kiln switching, resulting in a temporary decrease in the carbon dioxide content in the exhaust gas.

[0007] RU 2 724 835 C1 discloses a method for calcining carbonate materials in a countercurrent kiln having two kiln bodies.

[0008] DE 10 2004 002 043 A1 discloses a method for burning granulated combustible mineral material.

[0009] For example, DE 10 2021 204 176 A1 discloses a parallel-flow regenerative shaft kiln and a method for burning carbonate rocks.

[0010] The object of the present invention is to provide a method for kiln switching in which mixing between kiln offgas and lime cooling air is substantially avoided, thereby avoiding a reduction in the carbon dioxide content in the offgas and thus allowing the removal of carbon dioxide in a simple manner.

[0011] This object is achieved by a method having the features specified in claim 1 and a control system having the functionality specified in claim 19. Advantageous developments are apparent from the dependent claims, the subsequent description and the drawings.

[0012] The method according to the method is used for kiln switching in a parallel flow regeneration shaft kiln. In a parallel flow regeneration shaft kiln (PFR shaft kiln), initially one kiln body is used as a combustion kiln body and the second kiln body is used as a regeneration kiln body. After one cycle, for example lasting 10 min to 60 min, in particular 10 min to 20 min, for example 15 min, the kiln body switching is carried out, and then the first kiln body is used as a regeneration kiln body and the second kiln body is used as a combustion kiln body. Here, for conventional plants, the PFR shaft kiln is usually switched under reduced pressure conditions, the combustion products are removed at the bottom, and the unburned products are supplied from the top. The advantage of the PFR shaft kiln is that this mutual operation leads to very efficient heat recovery and the process is therefore very energy-saving. According to the present invention, this prior art kiln switching method is completely changed. On the contrary, a certain gas flow and pressure are maintained in the PFR shaft kiln, as a result, even during the kiln switching, the exhaust gas constantly continues to have a high carbon dioxide concentration, so that removal, in particular subsequent liquefaction, is still easily feasible.

[0013] The parallel flow regeneration vertical kiln used in the method of the present invention has a first kiln body and a second kiln body. The first kiln body has a first preheating zone for preheating materials, a first combustion zone for burning materials, and a first cooling zone for cooling materials. The second kiln body has a second preheating zone for preheating materials, a second combustion zone for burning materials, and a second cooling zone for cooling materials. The first combustion zone and the second combustion zone are connected by 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 combustion lance, and the second combustion zone has at least one second combustion lance. At least one first combustion lance is connected to a first fuel supply device, and at least one second combustion lance is connected to a second fuel supply device.

[0014] The method comprises the following steps:

[0015] a) operating the first kiln body as a combustion kiln body and operating the second kiln body as a regeneration kiln body,

[0016] b) stopping the fuel supply through the first fuel supply device, thereby burning out the fuel in the first kiln body,

[0017] c) close the second exhaust gas outlet,

[0018] After step c) starts and before step c) ends, the following steps d) to f) start

[0019] d) opening the second combustion gas inlet,

[0020] e) closing the first combustion gas inlet,

[0021] f) opening the first exhaust gas outlet,

[0022] g) Starting fuel supply through the second fuel supply device, thereby operating the second kiln body as a combustion kiln body and operating the first kiln body as a regeneration kiln body.

[0023] It is therefore essential that the supply of combustion gases and the discharge of exhaust gases must not be interrupted at any time. As a result, the PFR shaft kiln is not depressurized, i.e. does not reach ambient pressure. This in turn leads to a minimization of mixing between exhaust gases and cooling gases even during kiln changeovers. In particular, the cooling gases can be conveyed in an unchanged form through the PFR shaft kiln; in particular, there is absolutely no need to stop or change the cooling gas supply. As a result, the removal of CO2 from the exhaust gases remains very simple, since the CO2 concentration is always high.

[0024] Step a) corresponds to a normal combustion process. Step b) also corresponds to a normal procedure.

[0025] Step c) first starts with closing the second exhaust gas outlet. This in turn means that the PFR shaft kiln is not opened, i.e. it does not reach ambient pressure, but rather maintains pressure. During the closing period, the opening of the second combustion gas inlet in step d), the closing of the first combustion gas inlet in step e) and the opening of the first exhaust gas outlet in step f) are then started, overlapping in time. The effect is that the pressure in the connecting channel can be kept relatively constant, which in turn is a good indicator for avoiding mixing with the cooling gas.

[0026] While it has been customary to depressurize a PFR shaft kiln during the switchover, with the finished product removed at the bottom and new reactants fed in from the top, the kiln being at ambient pressure anyway, this is not the case with the method according to the invention. Here, in particular, the removal of the product and the feed of the reactants can also be carried out, for example, via a lock independently of the switchover process. The method according to the invention therefore does not have to be directly linked to the feed of reactants and / or the removal of the product; instead, it can be carried out separately.

[0027] In another embodiment of the invention, steps d) and e) are carried out synchronously. This can be achieved, for example, preferably by means of a switchable Y-switch. The gas flow to the combustion gas inlet is not interrupted; instead, the gas flow is supplied to the combustion gas inlet to be opened just to the extent that the combustion gas inlet to be closed is closed. Thus, during the switching process, the amount of gas flowing into the PFR shaft kiln can be kept constant in a very simple manner. However, since steps c) and f) are not carried out completely synchronously, but with a time offset, the gas discharge is actually reduced at a constant gas supply, which means that the pressure in the PFR shaft kiln is more likely to increase, so that, for example, no cooling gas can come out of the cooling zone.

[0028] In another embodiment of the invention, steps d) to f) are started simultaneously. This is preferred and ensures that the pressure in the connecting channel is particularly constant.

[0029] In another embodiment of the invention, steps c), d) and e) have a first time length t1. Step f) has a second time length t2, which is longer than the first time length t1. This means that the first exhaust gas outlet is opened slowly in step f). In particular in combination with the early start of closing the second exhaust gas outlet in step c), this ensures that the PFR shaft kiln is not depressurized, but rather that the pressure conditions, in particular in the combustion zone, remain sufficiently stable to particularly reliably avoid mixing with the cooling gas.

[0030] In another embodiment of the present invention, the second time length t2 is 1.5 to 5 times the first time length t1. Preferably, the second time length t2 is 2 to 3 times the first time length t1.

[0031] In another embodiment of the invention, step f) is started after the start and before the end of steps c), d) and e). Thus, although the gas discharge through the first and second waste gas outlets is permanently open, the gas discharge is initially reduced during the method, thereby ensuring that the pressure in the PFR shaft kiln is more likely to increase than to decrease in a simple manner, thereby reliably preventing mixing with the cooling air.

[0032] In another embodiment of the present invention, step c) has a first time length t1. Steps d), e) and f) start 1 / 4t1 to 3 / 4t1, in particular 1 / 3t1 to 2 / 3t1 after the start of step c). For example, steps d), e) and f) start exactly in the middle of step c), i.e. with a time offset of 1 / 2t1.

[0033] In another embodiment of the present invention, the supply of cooling gas and the discharge of cooling gas in the first cooling zone and the second cooling zone are continuously performed at a constant cooling gas flow rate. Here, in particular, the gas flow rate is kept constant in all steps. This allows the flow distribution and pressure distribution in the first cooling zone and the second cooling zone to remain constant.

[0034] In another embodiment of the present invention, the opening and closing in steps c), d), e) and f) are performed at variable speeds. In particular, the opening is performed relatively slowly at first and then speeds up as the steps progress. In particular, the closing is performed relatively quickly at first and then slows down as the steps progress.

[0035] In another embodiment of the invention, a first pressure is measured in the upper gas region of the first kiln body. In addition, a second pressure is measured in the upper gas region of the second kiln body. Optionally, the pressure in the connecting channel can be additionally measured. The measurement of the pressure allows control depending on the measured pressure.

[0036] In another embodiment of the invention, the opening and closing speeds in steps c), d), e) and f) are 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, priority is given to controlling the decreasing pressure. Thus, only a minimal pressure drop is detected in the connecting channel, which means that mixing with the cooling gas can be substantially avoided.

[0037] In another embodiment of the invention, the first rate is identical to the second rate in absolute value. The first rate and the second rate have opposite signs. "Identical in absolute value" is understood here in a technical sense, not in a precise mathematical sense. This achieves synchronous switching of the gas flow in the first kiln body and the second kiln body of the PFR shaft kiln.

[0038] In another embodiment of the present invention, the first combustion gas inlet and the second combustion gas inlet are connected to a combustion gas pipeline. The combustion gas pipeline is connected to an oxidant supply. In particular, the oxidant supply can be connected to an air separator or some other oxygen source. Preferably, oxygen with a purity of at least 90%, preferably at least 95%, more preferably at least 98% is supplied by the oxidant supply. The oxidant supply is opened after steps c), d), e) and f) are completed and before step g) begins.

[0039] In another embodiment of the invention, the oxidant supply is closed during step b). A procedure is preferred such that when step b) is finished, the closing of the oxidant supply has been completed.

[0040] In another embodiment of the invention, an increased opening speed is selected as the opening speed in steps d) and f).

[0041] In another embodiment of the invention, the supply of reactants and the removal of products are performed during step a). Thus, the supply and removal are performed through a lock so that neither the gas composition nor the pressure inside the PFR shaft kiln is adversely affected.

[0042] In another 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 also allows in particular active control of the speed of opening and closing.

[0043] Furthermore, in a PFR shaft kiln for carrying out the method, the gas inlet can be arranged in the preheating zone of a kiln body operated as a combustion kiln body. The gas inlet in the preheating zone of the combustion kiln body is preferably a combustion gas inlet, through which an oxidant is preferably introduced into the preheating zone in addition to the exhaust gas. The gas inlet is preferably arranged at the upper end of the preheating zone.

[0044] Furthermore, in a PFR shaft kiln for carrying out the method, the gas inlet can be arranged in a connecting channel for gas connection to the combustion zone of the kiln body and / or in the combustion zone of the kiln body, in particular the regeneration kiln body and / or in a material-free space in the kiln body. In particular, the material-free space is in the form of an outer annular space which preferably extends circumferentially around an upper region of the cooling zone adjacent to the combustion zone.

[0045] Furthermore, in a PFR shaft kiln for carrying out the method, arranged between the exhaust gas outlet and the gas inlet in the connecting channel for the gas connection of the combustion zone of the kiln body and / or in the combustion zone may be a heat exchanger and / or a heating device for heating the exhaust gas, in particular an electric heating device, a solar device or a combustion reactor. For example, the heat exchanger is arranged upstream of the heating device in the flow direction of the exhaust gas. It is also conceivable that only the heat exchanger or the heating device is used for heating the exhaust gas.

[0046] Furthermore, in a PFR shaft kiln for carrying out the method, the cooling zone may have a cooling gas inlet for introducing cooling gas into the cooling zone and a cooling gas extraction device for discharging cooling gas from the kiln body.

[0047] Furthermore, in a PFR shaft kiln for implementing the method, there may be a material-free space in the cooling zone of the kiln body. In particular, the material-free space is in the form of an outer annular space, which preferably extends circumferentially around an upper region of the cooling zone adjacent to the combustion zone. In particular, the cooling gas outlet is arranged in the material-free annular space.

[0048] The material-free space of the cooling gas extraction device is in the form of, for example, an inner barrel, which extends through the cooling zone, in particular in the center and in the vertical direction. In particular, the inner barrel extends at least partially into the combustion zone. A cooling gas outlet for discharging cooling gas from the kiln body is arranged in the inner barrel. The inner barrel preferably has a cooling gas inlet for introducing cooling gas from the cooling zone into the interior of the inner barrel, the cooling gas inlet being preferably arranged below the cooling gas outlet in the inner barrel. In particular, the cooling gas inlet is arranged at the lower end of the cooling zone so that the cooling gas preferably flows through the entire cooling gas zone and then flows into the inner barrel of the cooling gas extraction device. In the inner barrel, the cooling gas preferably flows downward in the direction of the cooling gas outlet and enters the cooling gas extraction line. The cooling gas extraction device in the form of an inner barrel enables a low structural height of the cooling zone and relatively easy retrofitting of known PFR shaft kilns.

[0049] The material-free space of the cooling gas extraction device is in the form of a connecting channel, for example for the gas connection of the cooling zones of two kiln bodies, the cooling gas outlet being preferably arranged in the connecting channel, in particular in the center.

[0050] The cooling gas extraction device is preferably configured so that it discharges all cooling gas from the kiln body, so that preferably no cooling gas enters the combustion zone or the connecting channel for connecting the combustion zone to the kiln body. In particular, the cooling gas extraction device is connected to a control element, such as a flap or a valve, to adjust the amount of cooling gas to be extracted.

[0051] Furthermore, in a PFR shaft kiln for implementing the method, the cooling gas extraction device can be connected to a heat exchanger for heating the exhaust gas. The cooling gas extraction device is connected to the heat exchanger in particular via a cooling gas extraction line. The heat exchanger is preferably used to heat the exhaust gas discharged from the preheating zone of the regeneration kiln body via the exhaust gas outlet. The heat exchanger is in particular connected to the exhaust gas outlet and the cooling gas outlet of the cooling gas extraction device.

[0052] Furthermore, in a PFR shaft kiln for implementing the method, each kiln body may have a combustion gas inlet for introducing combustion gas into the preheating zone and / or the combustion zone, the combustion gas inlet being connected to an oxidant line for introducing oxidant into the kiln body. The combustion gas inlet is preferably connected to an exhaust gas outlet for directing exhaust gas into the kiln body.

[0053] In another aspect, the invention relates to a control system for a co-current regenerative shaft kiln, which is designed to carry out the method according to the invention. Preferably, the control system has executable program instructions for carrying out the method according to the invention for this purpose. Thus, the control system is not only suitable for, but also capable of carrying out the method according to the invention.

[0054] The method according to the invention is explained in more detail below based on the exemplary embodiments shown in the drawings.

[0055] Figure 1 A first exemplary PFR shaft kiln for implementing the method is shown.

[0056] Figure 2 A second exemplary PFR shaft kiln for implementing the method is shown.

[0057] Figure 3 Shows the complete cycle

[0058] Figure 4 Shows kiln switching

[0059] Figure 5 Shows the pressure curve during kiln switching

[0060] In the drawings and reference symbols, there is no distinction between the first kiln body and the second kiln body. In each, the functions are interchanged between the two kiln bodies, and therefore, common reference symbols for the first kiln body and the second kiln body and corresponding parts are appropriate. DETAILED DESCRIPTION

[0061] Figure 1 A PFR shaft kiln 1 is shown with two parallel and vertically oriented kiln bodies 2. The kiln bodies 2 of the PFR shaft kilns 1 have essentially the same construction, so that Figure 1In the figure, only one of the two kiln bodies 2 is provided with a reference symbol, and for the sake of simplicity, only one of the two kiln bodies is described below. Each kiln body 2 has a respective material inlet 3 for introducing the material to be burned into the respective kiln body 2 of the PFR shaft kiln 1. The material to be burned is in particular limestone and / or dolomite, preferably with a particle size of 10 to 200 mm, preferably 15 to 120 mm, most preferably 30 to 100 mm. For example, the material inlet 3 is arranged at the upper end of the respective kiln body 2, so that the material falls into the kiln body 2 through the material inlet 3 due to gravity. The material inlet 3 is in the kiln body 2, for example, in the form of an upper opening, in particular in the form of a lock 3, and preferably extends over the entire or part of the cross section of the kiln body 2. The material inlet in the form of a lock 3 is preferably designed so that only the raw material to be burned enters the kiln body 2, but not the ambient air. The lock 3 is preferably configured so that it seals the kiln body 2 in the environment in a gas-tight manner and allows solids, such as the material to be burned, to enter the kiln body.

[0062] Each kiln body 2 also has a combustion gas inlet 12 at its upper end for introducing combustion gas for burning fuel. The combustion gas is, for example, dust removal exhaust gas from at least one kiln body 2, the exhaust gas preferably being enriched with oxygen. In addition, each kiln body 2 has an exhaust gas outlet 6 for discharging exhaust gas from the respective kiln body 2. For example, a corresponding control element is assigned to each exhaust gas outlet 6 and combustion gas inlet 12. A control element, such as a compressor 35 with adjustable volume, can preferably be used to adjust the amount of combustion gas in the respective combustion gas inlet 12 and the amount of exhaust gas extracted via the respective exhaust gas outlet 6. The combustion gas inlet 12 and the exhaust gas outlet are, for example, arranged at the same height level, in particular in the preheating zone 21 of the respective kiln body 2.

[0063] A material outlet 40 for discharging the burned material is arranged at the lower end of the kiln body 2. The material outlet 40 is, for example, the lock described with reference to the material inlet 3.

[0064] The burned material is introduced into, for example, an outlet funnel 25, which is adjacent to a material outlet 40 of the kiln body 2. As an example, the outlet funnel 25 is funnel-shaped. The outlet funnel 25 preferably has a cooling gas inlet 23 for introducing cooling gas into the corresponding kiln body 2. The cooling gas is preferably guided to the cooling gas inlet by a compressor 33.

[0065] During operation of the PFR shaft kiln 1 , material to be combusted flows from top to bottom through the respective kiln body 2 , while cooling air flows from bottom to top through the respective kiln body 2 in countercurrent to the material. Kiln exhaust gases are discharged from the kiln body 2 through the exhaust gas outlet 6 .

[0066] The preheating zone 21 of the respective kiln body 2 is adjacent below the material inlet 3 and the combustion gas inlet 12 in the material flow direction. The material and the combustion gas are preferably preheated to about 700° C. in the preheating zone 21. The respective kiln body 2 is preferably filled with the material to be combusted. The material is preferably fed into the respective kiln body 2 above the preheating zone 21. For example, at least a portion of the preheating zone 21 and a portion of the respective kiln body 2 adjacent thereto in the material flow direction are surrounded by a refractory lining.

[0067] A plurality of burner lances 10 are optionally arranged in the preheating zone 21 and each serves as an inlet for a fuel such as a fuel gas, oil or a ground solid fuel. The PFR shaft kiln 1 has, for example, a cooling device for cooling the burner lances 10. The cooling device comprises, for example, a plurality of cooling air annular lines extending annularly around the kiln body region where the burner lances 10 are arranged. The cooling air for cooling the burner lances 10 preferably flows through the cooling air annular lines. Preferably, the burner lances 10 are cooled by exhaust gases discharged via the exhaust gas outlet 6. The exhaust gas outlet 6 is preferably connected to the burner lances 10 for guiding the exhaust gases to the burner lances 10.

[0068] A plurality of, for example twelve or more, burner lances 10 are preferably arranged in each kiln body 2 at a substantially uniform distance from one another. By way of example, the burner lances 10 have an L-shape and preferably extend in the horizontal direction into the respective kiln body 2 and in the vertical direction, in particular in the direction of the material flow within the kiln body 2. The ends of the burner lances 10 of the kiln body 2 are preferably all arranged at the same height level. Preferably, the plane on which the lance ends are arranged is in each case the lower end of the respective preheating zone 21. The burner lances 10 are preferably connected to a fuel line 9 for conducting fuel to the burner lances 10. For example, the fuel line 9 is at least partially in the form of an annular line which extends circumferentially around the respective kiln body 2. Preferably, each kiln body 2 has a fuel line which is in each case assigned to a burner lance 10 of the kiln body 2 and in particular has a respective control element for regulating the amount of fuel to the burner lances 10.

[0069] The combustion zone 20 adjoins the preheating zone 21 in the material flow direction. In the combustion zone 20, the fuel is burned and the preheated material is burned at a temperature of about 1000° C. The PFR shaft kiln 1 also has a connecting channel 19 for gaseous connection of the two kiln bodies 2 to each other. In particular, there is no material to be burned in the connecting channel 19.

[0070] As an example, Figure 1A PFR lime kiln 1 with a circular kiln body cross section is shown. However, the cross section of the kiln body can have different geometrical contours, such as circular, semicircular, elliptical, square or polygonal. The burner zone 20 extends, for example, in a first and a second kiln body part, wherein the cross section of the first kiln body part is essentially constant or slightly increases towards the bottom. The first kiln body part adjoins the second kiln body part in the material flow direction, and the kiln body cross section of the second kiln body part decreases in the direction of material flow. The lower area of ​​the first kiln body part extends to the upper area of ​​the second kiln body part, as a result of which an annular channel 18 is formed between the two kiln body parts. The annular channel 18 forms a material-free space in which no material to be burned is arranged. The upper area of ​​the second kiln body part has a larger cross section than the first kiln body part, the cross section of the second kiln body part decreases in the material flow direction to the cross section of the first kiln body part, and preferably forms the lower end of the combustion zone 20. The annular channel 18 preferably extends circumferentially around the lower area of ​​the first kiln body part of the combustion zone 20. For example, Figure 1 Each kiln body 2 has an annular channel 18 which is connected to a connecting channel 19 .

[0071] The combustion zone 20 is adjoined in the material flow direction in each kiln shell 2 by a cooling zone 22 which extends to a material outlet 40. The cooling zone is formed in a kiln shell portion whose cross section is substantially constant or tapers towards the bottom. The cross section of the kiln shell portion of the cooling zone 22 is larger than the cross section of the lower region of the combustion zone 20, with the result that a further material-free space 17, in particular an annular shoulder, is formed adjacent to the combustion zone 20 at the upper end of the cooling zone 22, where no material is arranged. The material is cooled in the cooling zone 22 to about 100° C. in countercurrent with the cooling gas flowing through the material. A preferably conical flow device is arranged at the lower end of the cooling zone 22, which serves to guide the material in the direction of the kiln shell wall.

[0072] Each cooling zone 22 is equipped with a corresponding cooling air outlet device 17 having a corresponding cooling gas outlet 29. Figure 1 In the exemplary embodiment of the present invention, the cooling air outlet device 17 is in the form of a material-free, in particular annular space 17. The cooling gas outlet 29 is preferably arranged in the kiln body wall at the upper end of the cooling zone 22 without the material space 17. The cooling gas flowing into the cooling zone 22 via the cooling gas inlet 23 preferably flows completely out of the corresponding kiln body 2 from the cooling gas outlet 29 of the cooling air outlet device 17.

[0073] The discharge device 41 is preferably arranged at the material outlet side end of each kiln body 2. The discharge device 41 comprises, for example, a horizontal plate, preferably a discharge table, which allows the material to pass laterally between the discharge table and the shell wall of the PFR shaft kiln. The discharge device 41 is preferably implemented as a push table or a rotating table, or as a table with a push-type scraping device. This makes the throughput rate of the material burned through the kiln body 2 uniform. For example, the discharge device 41 also includes an outlet funnel 25, which is adjacent to the discharge table and has a material outlet 40 attached to its lower end.

[0074] During operation of the PFR shaft kiln 1, one of the kiln shells 2 is active at any time and the other kiln shell 2 is passive. The active kiln shell 2 is referred to as the combustion kiln shell and the passive kiln shell 2 is referred to as the regeneration kiln shell. The PFR shaft kiln 1 is operated in particular in a cyclic manner, for example with a typical number of cycles of 75 to 150 cycles per day. After the cycle time has expired, the function of the kiln shell 2 is exchanged. This process is repeated continuously. Material, such as limestone or dolomite, is alternately fed to the kiln shell 2 via the material inlet 3. In the active kiln shell 2 operated as a combustion kiln shell, fuel is introduced into the combustion kiln shell 2 via the burner lances 10. The material to be combusted is heated to a temperature of about 700° C. in the preheating zone 21 of the combustion kiln shell. In the Figure 1 In the exemplary embodiment of the present invention, the left kiln body 2 is operated as a combustion kiln body, and the right kiln body 2 is operated as a regeneration kiln body.

[0075] During operation of the PFR shaft kiln 1, both in the combustion kiln body 2 and in the regeneration kiln body 2, cooling gas flows through the cooling zone 22 countercurrent to the material to be cooled and is preferably completely discharged from the kiln body 2 through the cooling gas outlet 29, so that preferably no cooling gas flows from the cooling zone 22 into the combustion zone 20.

[0076] In the kiln body 2 operated as a combustion kiln body, the combustion gas flows into the combustion kiln body through the combustion gas inlet 12 and flows into the material-free space in the form of the annular channel 18 in parallel with the material in the combustion zone 20. From the material-free space 18, the gas flows into the kiln body 2 operated as a regeneration kiln body via the connecting channel 19. In the regeneration kiln body, the gas flows from the connecting channel 19 and the material-free space 18 of the regeneration kiln body through the combustion zone 20 in countercurrent with the material to be burned into the preheating zone 21 and leaves the regeneration kiln body through the waste gas outlet 6 of the regeneration kiln body. The temperature of the waste gas discharged from the kiln body 2 is preferably 60° C. to 160° C., preferably 100° C.

[0077] The exhaust gas is introduced into the exhaust gas line 39 adjacent to the exhaust gas outlet 6. The exhaust gas line 39 optionally has an exhaust gas filter 31 downstream of the exhaust gas outlet 6 in the flow direction of the exhaust gas for filtering out fine particles, in particular dust, from the exhaust gas. Downstream of the exhaust gas filter 31, the exhaust gas line 39 has a branch point, in which part of the exhaust gas is guided to the combustion gas inlet 12 in the combustion gas line 4. In the flow direction of the exhaust gas, downstream of the branch point, the combustion gas line 4 has, for example, a control element, such as a butterfly valve and a compressor 35. The combustion gas line 4 is preferably connected to the combustion gas inlet 12 of the kiln body 2, and the exhaust gas is preferably supplied to the combustion gas inlet 12 of the kiln body 2 operated as a combustion kiln body only through the control element connected upstream of the combustion gas inlet 12. The combustion gas line 4 is preferably connected to the oxidant line 14, so that the oxidant (preferably pure oxygen) is introduced into the combustion gas line 4 and then introduced into the kiln body 2 via the combustion gas inlet 12 together with the exhaust gas. It is also conceivable to introduce oxygen-enriched gas having an oxygen content of at least 70% to 95%, preferably 90%, into the combustion gas line 4 as oxidant.

[0078] The part of the exhaust gas which is not returned to the combustion gas inlet 12 is supplied in the exhaust gas line 39 to the gas inlet 15 in the connecting channel 19. Downstream of the branch point of the combustion gas line 4 in the direction of the exhaust gas flow, the exhaust gas line 39 preferably has a compressor 36 with adjustable volume, a heat exchanger 43 and optionally a heating device 8 for heating the exhaust gas. For example, the heat exchanger 43 is in the form of a recuperator, in which the exhaust gas is heated in countercurrent to the extracted cooling gas and the cooling gas is cooled simultaneously. In particular, the heat exchanger 43 is connected to the cooling gas outlet 29 of the two kiln bodies 2 via the cooling gas extraction line 11, so that the exhaust gas in the heat exchanger 43 is preferably heated in countercurrent by the extracted cooling gas. Downstream of the heat exchanger, the cooling gas extraction line 11 optionally has a control element for regulating the amount of cooling gas to be extracted and a filter 16 for dust removal of the cooling gas. The exhaust gas is preferably heated to a temperature of about 900° C. to 1100° C., in particular 1000° C., in the heat exchanger 43 and / or the heating device 8. It is also conceivable that the exhaust gas line 39 has only a heat exchanger 43 or a heating device 8 for heating the exhaust gas. By way of example, the exhaust gas is heated to a temperature of about 600° C. in the heat exchanger 43 and then to a temperature of about 1000° C. in the heating device 8 .

[0079] The heating device 8 is, for example, an electrically operated heating device. In particular, the heating device is operated by solar energy. It is also conceivable that the heating device 8 comprises a heat exchanger, in which the countercurrently flowing heating medium is heated by solar energy. The heating device 8 is preferably in the form of a combustion reactor for burning a preferably renewable energy source, such as wood, wherein the combustion is preferably carried out in such a way that the combustion gases have a high proportion of CO2 of at least 90%.

[0080] Part of the exhaust gas is branched off upstream of the heat exchanger 43 and discharged via the cooling device 32 by means of a compressor 37. Preferably, the entire amount of CO2 from the calcination and combustion and the water from the combustion are discharged from the PFR shaft kiln 1. The cooling device 32 is, for example, a heat exchanger, which is preferably operated in countercurrent with a coolant such as water. For example, the exhaust gas line has compressors 34, 36 before and after the branching point of the exhaust gas to be discharged.

[0081] The connecting channel 19 has a gas inlet 15 for allowing the recirculated exhaust gas to enter the connecting channel 19. The gas inlet 15 is connected to the exhaust gas outlet 6 of the kiln body 2 via the exhaust gas pipeline 39, so that the dust-removed and heated exhaust gas discharged from the kiln body 2 is guided into the connecting channel 19. The gas inlet 15 is arranged, for example, at the center of the upper wall of the gas channel 15. It is also conceivable to arrange the gas inlet 15 at a position deviated from this position in the wall of the connecting channel 19 or the annular channel 18. It is also conceivable to install a plurality of gas inlets 15 in the connecting channel 19 or the annular channel 18, each gas inlet being connected to the exhaust gas pipeline 39.

[0082] Figure 1 Two gas analysis devices 45, 46 are further shown by way of example. The gas analysis devices 45, 46 are configured such that they each 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 branching point of the combustion gas line 4 and is configured to determine the oxygen and / or CO2 content of the exhaust gas. In particular, the gas analysis device 45 is connected to a control device (not shown) for transmitting the determined oxygen and / or CO2 content in the exhaust gas.

[0083] The oxidant line 14 preferably has a control element, such as a valve or a flap, which can be used to adjust the amount of oxidant in the combustion gas line 4. The control element is preferably connected to a control device, which is particularly configured to control the amount of oxidant in the combustion gas line 4 as a function of the oxygen and / or CO2 content of the exhaust gas determined by the gas analysis device 45.

[0084] This control is used in particular for complete combustion of the fuel supplied to the PFR shaft kiln 1 via the fuel line 9. Thus, an undesirably high proportion of oxygen in the off-gas line 39 is prevented. The CO2 content is also measured in order to control the desired CO2 content in the off-gas line 39.

[0085] The control device is preferably configured so that it compares the oxygen and / or CO2 content determined by the gas analysis device 45 with corresponding predetermined limit values ​​or limit ranges and, if the determined values ​​deviate from the limit values ​​or ranges, increases or decreases the amount of oxidant in the combustion gas pipeline.

[0086] If the determined oxygen content is below a limit value or a limit range, the amount of oxidant is preferably increased. If the determined oxygen content is above a limit value or a limit range, the amount of oxidant is preferably reduced.

[0087] A gas analysis device 46 is arranged, for example, in the cooling gas extraction line 11, in particular downstream of the heat exchanger 43 and, for example, the filter 16, and is configured to determine the oxygen and / or CO2 content of the exhausted cooling gas. In particular, the gas analysis device 46 is connected to a control device (not shown) for transmitting the determined oxygen and / or CO2 content of the cooling gas.

[0088] The cooling gas extraction line 11 preferably has a control element, such as a valve or a flap, which can be used to adjust the amount of cooling gas discharged via the cooling gas extraction device 17. The control element is preferably connected to a control device, which is particularly configured to control the amount of cooling gas discharged via the cooling gas extraction device 17 as a function of the oxygen and / or CO2 content of the cooling gas determined by the gas analysis device 46.

[0089] This control serves in particular to remove the cooling gases from the PFR shaft kiln 1 as completely as possible, while at the same time having as little CO 2 as possible or preferably no CO 2 in the cooling gas withdrawal line 11 .

[0090] The control device is preferably configured so that it compares the oxygen and / or CO2 content determined by the gas analysis device 46 with a corresponding predetermined limit value or limit range and, if there is a deviation between the determined value and the limit value or limit range, increases or decreases the amount of cooling gas discharged via the cooling gas extraction device 17.

[0091] If the determined CO2 content is below a limit value or a limit range, the amount of cooling gas is preferably increased. If the determined CO2 content is above a limit value or a limit range, the amount of cooling gas is preferably reduced.

[0092] Figure 2 Another exemplary embodiment of a PFR shaft kiln is shown, which corresponds largely to Figure 1 PFR shaft kiln. Identical components have the same reference symbols. For example, Figure 2 In the PFR shaft kiln 1, the left kiln body 2 is operated as a combustion kiln body. Figure 1 Compared with the PFR shaft kiln, Figure 2 The PFR shaft kiln 1 has a cooling gas extraction device 17 which comprises an inner barrel 26 which extends at least partially from the cooling zone 22 into the combustion zone 20 and has a cooling gas outlet 29 which is connected to the cooling gas extraction line 11 .

[0093] The cooling zone 22 is formed, for example, in a kiln body portion having a substantially constant cross section, the kiln body cross section of the cooling zone 22 corresponding to the kiln body cross section of the lower region of the combustion zone 20. Figure 2 In the exemplary embodiment, no Figure 1 The material-free annular space of the PFR shaft kiln. Figure 2 Each kiln body 2 of the PFR shaft kiln 1 has an inner barrel 29, which extends centrally through the cooling zone 22 in the vertical direction. For example, the inner barrel 29 extends from the discharge device 41 through the cooling zone 22 into the combustion zone 20 until the height of the connecting channel 19. In order to cool the inner barrel 29, a plurality of cooling air channels are formed in its outer wall and connected to the cooling air line 7 for guiding cooling air. The cooling air is preferably guided into the cooling air channels of the inner barrel 26 via the cooling air line 7 by a compressor 38. For example, the heated cooling air is introduced into the cooling gas extraction line 11 and is preferably supplied to the heat exchanger 43 to heat the exhaust gas. The inner barrels 26 each have a cooling air inlet 27 and a cooling air outlet 28 extending radially outwards, which are connected to the cooling air line 7.

[0094] The inner barrel 26 of the cooling gas extraction device 17 has a cooling gas outlet 29 extending radially outward from the inner barrel 26 through the kiln wall and for guiding cooling gas from the inner barrel into the cooling gas extraction line 11. The inner barrel 26 also has a cooling gas inlet 30 for introducing cooling gas from the cooling zone 22 into the inner barrel 26. The cooling gas inlet 30 extends through the inner barrel wall into the cooling zone 22 and connects the interior of the inner barrel 26 to the cooling zone 22. For example, each inner barrel 26 has four cooling gas inlets 30, each of which is formed at the same height in the inner barrel wall and preferably extends outwardly into the cooling zone 22 at uniform distances from each other in a star shape. The cooling gas inlet 30 is preferably arranged above the cooling gas outlet 29 in the cooling zone 22. During operation of the PFR shaft kiln 1, cooling gas flows from bottom to top through the cooling zone 22 into the cooling gas inlet 30 and enters the inner barrel 26 of the cooling gas extraction device 17. Preferably, all cooling gas introduced into the cooling zone 22 flows into the cooling gas extraction device 17 through the cooling gas inlet 30, so that no cooling gas enters the combustion zone 20. The cooling air outlet 29 of the inner barrel 26 is preferably arranged in the lower region of the cooling zone 22. In particular, the cooling gas flows downward from the cooling gas inlet 30 in the inner barrel 26 to the cooling gas outlet 29.

[0095] exist Figure 2 In the exemplary embodiment of the present invention, the conduction of the cooling gas extracted from the cooling zone 22 and the conduction of the exhaust gas extracted from the preheating zone 21 correspond to the reference Figure 1 Describe the interconnection.

[0096] Figure 3The timeline of one cycle V is shown. Before and after the cycle V is shown in dashed lines another cycle V. One cycle V lasts 15 minutes. The cycle V is divided into a combustion time W and a kiln switch X. The combustion time W is further divided into a fuel metering time Y, during which fuel is introduced into the combustion kiln, and a burnout time Z, during which no more fuel is introduced into the combustion kiln, but oxygen-containing gas continues to be supplied so that the fuel still present in the combustion kiln can be burned out.

[0097] Now, Figure 4 View in Figure 3 The steps occurring during the kiln switch X are shown. The purpose here is to demonstrate the method according to the invention using a specific example. In the example shown, the kiln switch X starts with the closing of the second exhaust gas outlet D, which extends over 4 seconds. 2 seconds later, 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 gas outlet G begin simultaneously. The opening of the second combustion gas inlet E and the closing of the first combustion gas inlet F both require the same length of time, just like the closing of the second exhaust gas outlet D, which lasts for 4 seconds. In the example shown, the opening of the first exhaust gas outlet G is slower and lasts for 10 seconds. Thereafter, the oxidant supply H is started. The next cycle V starts with the fuel supply I.

[0098] Figure 5 The pressure curve at the upper end of the first kiln body U, the pressure curve at the upper end of the second kiln body S and the pressure curve in the connecting channel T during the kiln body switching process are shown. Initially, the pressure in the first kiln body operated as a combustion kiln body is higher, for example, 1.3 bar. The pressure in the second kiln body operated as a regeneration kiln body is lower, about 1 bar. The pressure in the connecting channel T is between the two, about 1.25 bar. The method according to the present invention realizes such a situation that the pressure in the first kiln body decreases at a rate v, while the pressure in the second kiln body increases at a rate v. As can be seen from the figure, this does not mean the same mathematical rate v, on the contrary, the rate v is the same within a technically reasonable and controllable range. Constant is also not in a purely mathematical sense, but within a technically reasonable range. It can be clearly seen that this only works in the first approximation within the pressure fluctuation range conventionally used in technology and cannot be strictly understood mathematically. However, except for a slight decrease in the pressure in the connecting channel T when the pressure in the first kiln body U and the pressure in the second kiln body S intersect, the pressure in the connecting channel T remains constant, so that mixing with cooling air can be basically avoided. Finally, the second kiln, now operating as a combustion kiln, has a higher pressure of about 1.3 bar, and the kiln, now operating as a regeneration kiln, has a lower pressure of about 1 bar.

[0099] Reference Symbols

[0100] 1 PFR vertical kiln

[0101] 2 Kiln body

[0102] 3 Material access / lock

[0103] 4 Combustion gas pipeline

[0104] 6 Exhaust gas outlet

[0105] 7 Cooling air lines

[0106] 8 Heating device

[0107] 9 Fuel lines

[0108] 10 Burner gun

[0109] 11 Cooling gas extraction line

[0110] 12 Combustion gas inlet

[0111] 14 Oxidant pipeline

[0112] 15 Gas inlet

[0113] 16 Filters

[0114] 17 No material space / cooling gas extraction device 18 Annular channel / no material space

[0115] 19 Connection Channels

[0116] 20 Burning Zone

[0117] 21 Preheating Zone

[0118] 22 Cooling Zone

[0119] 23 Cooling gas inlet

[0120] 25 Exit Funnel

[0121] 26 Inner tube

[0122] 27 Cooling air inlet

[0123] 28 Cooling air outlet

[0124] 29 Cooling gas outlet

[0125] 30 Cooling gas inlet

[0126] 31 Exhaust filter

[0127] 32 Cooling device

[0128] 33-38 Compressor

[0129] 39 Exhaust pipe

[0130] 40 Material outlet / lock

[0131] 41 discharge device

[0132] 42a, b connecting channel

[0133] 43Heat exchanger / regenerator

[0134] 45, 46 Gas analysis device.

Claims

1. A method for switching kiln bodies in a parallel flow regeneration shaft kiln (1), wherein: The vertical kiln is not depressurized during kiln body switching, wherein the parallel flow regeneration vertical kiln (1) comprises a first kiln body (2) and a second kiln body (2), wherein the first kiln body (2) comprises a first preheating zone (21) for preheating materials, a first combustion zone (20) for burning the materials and a first cooling zone (22) for cooling the materials, wherein the second kiln body (2) comprises a second preheating zone (21) for preheating materials, a second combustion zone (20) for burning the materials and a second cooling zone (22) for cooling the materials, wherein the first combustion zone (20) and the second combustion 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 combustion zone (20) has at least one first combustion lance and the second combustion zone (20) has at least one second combustion lance, wherein the at least one first combustion lance is connected to a first fuel supply device and the at least one second combustion lance is connected to a second fuel supply device, the method comprising the following steps: a) operating the first kiln body (2) as a combustion kiln body, and operating the second kiln body (2) as a regeneration kiln body, b) stopping the fuel supply through the first fuel supply device, thereby causing the fuel in the first kiln body (2) to burn out, c) closing the second exhaust gas outlet (6), After step c) starts and before step c) ends, the following steps d) to f) start 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 supply device, thereby operating the second kiln body (2) as a combustion kiln body and operating the first kiln body (2) as a regeneration kiln body.

2. The method according to claim 1, characterized in that Steps d) to f) are started simultaneously.

3. The method according to any one of the preceding claims, characterized in that Steps d) and e) are performed simultaneously.

4. A method according to any one of the preceding claims, characterised in that Steps c), d) and e) have a first time length t1, and step f) has a second time length t2, which is longer than the first time length t2.

5. The method according to claim 4, characterized in that The second time length t2 is 1.5 to 5 times the first time length t1.

6. A method according to any one of the preceding claims, characterised in that Step f) begins after steps c), d) and e) have begun and before steps c), d) and e) have ended.

7. A method according to any one of the preceding claims, characterised in that Step c) has a first time length t1, and steps d), e) and f) start 1 / 4 t1 to 3 / 4 t1 after the start of step c).

8. A method according to any one of the preceding claims, characterised in that In the first cooling zone (22) and the second cooling zone (22), supply of cooling gas and discharge of cooling gas are continuously performed at a constant cooling gas flow rate.

9. A method according to any one of the preceding claims, characterised in that The opening and closing in steps c), d), e) and f) are performed at variable speeds.

10. The method according to any one of the preceding claims, characterized in that A first pressure is measured in the upper gas region of the first kiln body (2), and a second pressure is measured in the upper gas region of the second kiln body (2).

11. The method according to claim 8 in combination with claim 9, characterized in that The opening and closing speeds in steps c), d), e) and f) are controlled so that the first pressure decreases at a constant first rate and / or the second pressure increases at a constant second rate.

12. The method according to claim 11, characterized in that The first rate is the same as the second rate in absolute value, and the first rate and the second rate have opposite signs.

13. A method according to any one of the preceding claims, characterised in that The first combustion gas inlet (12) and the second combustion gas inlet (12) are connected to a combustion gas pipeline (4), and the combustion gas pipeline (4) is connected to an oxidant supply device, which is opened after steps c), d), e) and f) are completed and before step g) begins.

14. The method according to claim 13, characterized in that During step b) the oxidant supply is closed.

15. The method according to claim 14, characterized in that When step b) is finished, the closing of the oxidant supply means has been completed.

16. A method as claimed in any one of the preceding claims, characterised in that An increased opening speed is selected as the opening speed in steps d) and f).

17. A method according to any one of the preceding claims, characterised in that During step a) the reactants are fed and the products are removed.

18. A method according to any one of the preceding claims, characterised in that The opening positions 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) are detected.

19. A control system for a parallel-flow regenerative shaft kiln (1), designed to carry out the method according to any of the preceding claims.

Images