CN116981900A

CN116981900A - Shaft kiln and method for burning carbonate-containing material in shaft kiln

Info

Publication number: CN116981900A
Application number: CN202280020771.XA
Authority: CN
Inventors: 汉内斯·皮林格; 帕特里克·布彻; 罗杰·沃利曼
Original assignee: Thyssenkrupp Polysius Ltd; Maerz Ofenbau AG; ThyssenKrupp AG
Current assignee: Thyssenkrupp Polysius Ltd; Maerz Ofenbau AG; ThyssenKrupp AG
Priority date: 2021-03-15
Filing date: 2022-03-07
Publication date: 2023-10-31
Also published as: DE102021202485A1

Abstract

The invention relates to a shaft kiln (1) for burning, in particular carbonate-containing, material, having a shaft (2) with a material inlet (3) in the direction of flow of the material, a preheating zone (21) for preheating the material, a combustion zone (20) for burning the material, a cooling zone (22) for cooling the burned material, and a material outlet (40) for discharging the material from the shaft kiln (1), wherein the shaft kiln (1) has an exhaust gas outlet (19) for discharging exhaust gas from the preheating zone of the shaft (2), and wherein the exhaust gas outlet (19) is connected to the combustion zone (20) for recovering the exhaust gas, wherein the shaft kiln (1) has a circulation device (54) for circulating a circulating gas in the combustion zone (20) and forming a downstream combustion zone (24) in the combustion zone.

Description

Shaft kiln and method for burning carbonate-containing material in shaft kiln

The present invention relates to a shaft kiln and a method for burning limestone or other carbonates using a shaft kiln having at least a burning zone and a cooling zone.

CH 378,217a discloses a shaft kiln for continuous combustion of mineral material having a combustion zone and a cooling zone, wherein hot gases of the combustion zone and cooling air for the burnt material are removed via extraction spaces formed in the transition zone between the combustion zone and the cooling zone.

DE 10 2010 060 866 B3 discloses a lime kiln comprising a combustion zone, the bottom end of which protrudes into the cooling zone of the shaft kiln. The maximum throughput of this configuration is only 250t/d. However, the lime industry currently demands lime shaft kilns in the order of 400t/d to 800t/d. In addition, it is desirable that lime be highly reactive and that the flue gas formed should have a high CO2 concentration for subsequent sequestration.

In order to produce burnt lime with high reactivity and at the same time produce exhaust gases with high concentration of CO2, the known processes generally lead to temperatures in the range of 1100 ℃ or higher, thus preventing the production of burnt lime with high reactivity.

The object of the present invention is therefore to specify a shaft kiln and a method for burning and/or calcining lump material, which method produces burnt lime with high reactivity in the most energy-efficient manner and at the same time separates out CO2.

This object is achieved according to the invention by a shaft kiln having the features of independent apparatus claim 1 and by a method having the features of independent method claim 13. Advantageous refinements are evident in the dependent claims.

According to a first aspect, a shaft kiln for burning, in particular carbonate-containing material, with a shaft comprises, in the direction of flow of the material, a material inlet, a preheating zone for preheating the material, a combustion zone for burning the material, a cooling zone for cooling the burned material, and a material outlet for discharging the material from the shaft kiln. The shaft kiln has an exhaust gas outlet for discharging exhaust gas from the preheating zone of the shaft. An exhaust outlet is connected to the combustion zone for recovering exhaust. The shaft kiln has a circulation device for circulating a circulating gas in the combustion zone and forming a concurrent (cocurrent) combustion zone in the combustion zone.

The advantage of such a circulation device is that a concurrent combustion zone is formed in the combustion zone, in which concurrent combustion zone the material to be combusted and the gas flow through the shaft in the same direction, i.e. from top to bottom. Along with the circulation of the circulating gas in a part of the combustion zone, the material can be calcined at a low temperature of about 900-1100 ℃ so that the final burnt material has higher reactivity and meets the requirements of applications such as steel plants.

The recycle gas is preferably a gas from the combustion zone, in particular from the lower region of the combustion zone adjacent to the cooling zone. The circulating gas being mainly composed of CO ₂ And H ₂ O composition, particularly because no cooling gas from the cooling zone enters the combustion zone. The combustion zone preferably has a counter-current (counter current) combustion zone and a downstream combustion zone immediately adjacent thereto in the direction of flow of the material. The recycle gas is preferably exclusively discharged from the forward combustion zone, in particular the recycle gas is exclusively fed back to the forward combustion zone. The recycle gas is composed in particular exclusively of the exhaust gases from the forward flow combustion zone. The circulation device is particularly configured to form a forward flow combustion zone.

The material to be burnt is, for example, limestone or dolomite, in particular having a particle size of from 10mm to 200mm, preferably from 15mm to 120mm, most preferably from 30mm to 100mm. Preferably the CO2 content in the exhaust gas is from 35% to 45%, preferably at least 90%, based on dry gas.

The material inlet is in particular arranged at the upper end of the shaft. A preheating zone for preheating the material is arranged upstream of the combustion zone in the flow direction of the material. The preheating zone is preferably located directly after the material inlet for the material into the shaft kiln and is used to preheat the material to a temperature of about 600 ℃ to 800 ℃. The combustion zone is preferably located directly after the preheating zone and is used for burning the material, wherein the material is preferably heated to a temperature of about 900 ℃ to 1100 ℃, in particular 1000 ℃. The cooling zone is preferably located directly after the combustion zone and is used to cool the burned material to a temperature of, for example, 100 ℃. The material outlet is arranged, for example, in the discharge hopper after the cooling zone, wherein the material outlet comprises, for example, a turntable or a slide table for discharging material from the cooling zone into the discharge hopper. Cooling air is preferably blown into the cooling zone of the shaft kiln via a cooling air inlet. The cooling air inlet is preferably arranged in the wall of the cooling zone.

The material inlet and/or the material outlet are in particular in the form of a sluice lock for introducing and/or discharging material into the shaft kiln. The material inlet is preferably designed in the form of a lock such that only the material to be burnt can enter the shaft, but ambient air cannot. The lock is preferably configured to seal the shaft from the environment in an airtight manner and to allow solids such as materials to be burned to enter the shaft.

One or more combustion chamber planes are preferably arranged in the combustion zone of the shaft, wherein the material-free space (in particular the combustion chamber) is preferably arranged circumferentially around the combustion zone. In each material free space, preferably in each combustion chamber, at least one gas inlet is arranged for introducing recirculated exhaust gas. The term "material free" is preferably understood to mean "material which is not useful for combustion". The material-free space is preferably a space free of material to be burned. The material-free space has, in particular, a plurality of gas inlets via which the recirculated exhaust gas is introduced into the combustion zone. The shaft kiln preferably has an oxidant feed conduit for conducting an oxidant, in particular an oxygen-enriched gas, into the combustion zone. The combustion chamber preferably has at least one burner arranged therein. For example, at least one additional burner, in particular a side burner in the form of a burner lance, is arranged in the combustion zone. The side burners preferably extend through the borehole wall into the combustion zone and are arranged in a variable manner, in particular in terms of the insertion depth.

The flue gas outlet is preferably arranged in the upper region of the shaft, in particular in the upper region of the preheating zone or the combustion zone and is connected in particular to an oxidant feed conduit for conducting the flue gas via the oxidant feed conduit into the combustion zone.

A flue gas outlet conduit is preferably connected downstream of the flue gas outlet for conducting the flue gas discharged from the shaft, in particular from the preheating zone. The exhaust gas outlet conduit optionally has, for example, water injection means for humidifying the exhaust gas while cooling it, in the flow direction of the exhaust gas. The exhaust gas removed from the preheating zone via the exhaust gas outlet preferably has a temperature of about 400 ℃ and is cooled in the water injection device, for example to a temperature of 200 ℃, and the water content preferably is between 10% and 25%.

The exhaust gas outlet conduit has a compressor (in particular a fan) and an exhaust gas filter in the flow direction of the exhaust gas (e.g. downstream of the exhaust gas outlet). The cooling device (such as, for example, a heat exchanger with water cooling function) preferably follows the flow direction. The cooling device cools the exhaust gases, preferably to a temperature of 30 deg.c. Downstream of the cooling device, the exhaust gas outlet conduit preferably has a branch, wherein one substream of the exhaust gas is discharged via a fan or compressor and the other substream is fed (in particular recirculated) as drive gas to the combustion zone, preferably via at least one other fan or compressor and the drive gas conduit. Optionally, upstream of the cooling device, in the flow direction of the exhaust gases, branches for branching off the substreams of the exhaust gases are also arranged, so that only one substream of the exhaust gases is recirculated into the cooling device and the remaining substream of the exhaust gases is recirculated into the combustion zone.

At least a portion of the flue gas discharged from the shaft via the flue gas outlet is recycled to the combustion zone, so that the atmosphere in the combustion zone can be heated by the discharged CO 2-containing flue gas. It is therefore preferred to introduce pure CO2 into the combustion zone together with oxygen and optionally small amounts of water vapour and ensure that the proportion of CO2 in the exhaust gas is very high, for example in excess of 90%. Preferably, only a portion (e.g., about 20% to 50%) of the exhaust gas is fed back to the combustion zone, while the remainder of the exhaust gas is removed from the shaft kiln and stored, e.g., for subsequent sequestration. Alternatively, CO in exhaust gas ₂ The content is low, for example 45% in soda production, 35% in sugar production, or 30% in precipitated calcium carbonate production.

According to a first embodiment, the combustion zone has a recycle gas outlet for discharging recycle gas from the combustion zone and a recycle gas inlet for introducing the recycle gas discharged via the recycle gas outlet into the combustion zone, wherein the recycle device is connected to the recycle gas inlet and the recycle gas outlet. In particular, the recycle gas device is arranged between and directly connected to the recycle gas inlet and the recycle gas outlet. The recycle gas device is preferably configured to accelerate recycle gas outside the shaft, in particular outside the combustion zone, from the recycle gas outlet into the recycle gas inlet. In particular, the circulating gas apparatus is configured to generate a negative pressure at the circulating gas outlet.

The recycle gas outlet is preferably arranged below the recycle gas inlet in the flow direction of the material to be combusted, downstream of the recycle gas inlet. The recycle gas inlet and the recycle gas outlet are in particular arranged in the combustion zone, preferably in the forward flow combustion zone. The recycle gas inlet and the recycle gas outlet are preferably both present in the form of a material free space within the combustion zone. The material-free space is, for example, an annular space or chamber arranged radially outside the combustion zone.

In addition, in particular in the form of annular shaft kilns, the circulation device comprises an inner drum, which is arranged concentrically with and inside the shaft, for example. An inner drum is for example arranged in the combustion zone and extends from the forward combustion zone to the reverse combustion zone, preferably into the preheating zone, or in particular to the boundary between the preheating zone and the combustion zone, and extends through the shaft wall via one or more outlets and out of the shaft. The recycle gas outlet is preferably formed in the inner barrel within the forward flow combustion zone and is for introducing gas from the forward flow combustion zone into the inner barrel. The recycle gas is discharged from the forward flow combustion zone via a recycle gas outlet and fed to a recycle gas inlet for introducing the recycle gas into the combustion zone via a recycle device.

Shaft kilns, in particular annular shaft kilns, have, for example, a plurality of circulating gas inlets for introducing circulating gas into the combustion zone, these inlets preferably being arranged circumferentially around the combustion zone, in particular the forward flow combustion zone. The shaft kiln, in particular an annular shaft kiln, preferably has a plurality of circulation devices, each connected to a respective circulation gas inlet. The combustion zone is preferably annular.

According to another embodiment, the circulation device has an ejector for accelerating the circulation gas into the combustion zone in the direction of the circulation gas inlet. The injector preferably has a cross-sectional constriction or in particular takes the form of a nozzle. The acceleration of the circulating gas creates a negative pressure at the circulating gas outlet, thereby creating a gas flow in the combustion zone in the direction of the circulating gas outlet. This gas flow forms a forward flow combustion zone between the recycle gas inlet and the recycle gas outlet. Preferably, the temperature of the gas in the forward flow combustion zone is between about 900 ℃ and 1100 ℃. The material is calcined in a countercurrent combustion zone and subsequently further calcined at a temperature of up to around 1100 ℃ in a concurrent combustion zone, so that a highly reactive burnt lime is produced.

According to a further embodiment, the recirculation device is connected to the exhaust gas outlet via a drive gas conduit for conducting the exhaust gas, such that the exhaust gas is at least partly introduced into the combustion zone together with the recirculation gas. The drive gas conduit preferably branches off from the exhaust gas outlet conduit, in particular downstream of the cooling device, whereby the exhaust gas flowing in the drive gas conduit is conducted as drive gas to the circulation device, in particular the ejector, and is therefore referred to as drive gas in the following. The temperature of the driving gas is preferably around 30 ℃. The drive gas conduit is preferably connected to an oxidant conduit for introducing an oxidant into the drive gas conduit before the drive gas is introduced into the circulation device. The oxidizing agent is, for example, pure oxygen, air, oxygen-enriched air or a gas having an oxygen content of at least 90%.

According to a further embodiment, the drive gas conduit is connected to a heat exchanger for heating the exhaust gas flowing in the drive gas conduit, in particular the drive gas. The heat exchanger is preferably connected to a cooling gas discharge device such that the exhaust gases, in particular the drive gas, are heated in the heat exchanger, in particular counter-currently to the discharged cooling air. The drive gas is preferably heated in a heat exchanger to a temperature of about 400 to 600 ℃ (in particular 500 ℃). The oxidizing agent is preferably introduced into the drive gas conduit upstream of the heat exchanger in the flow direction of the drive gas.

According to a further embodiment, the drive gas conduit is connected to the injector such that the exhaust gas is introduced into the injector together with the recycle gas. The introduction of the driving gas into the circulation device, in particular the ejector, creates a negative pressure at the circulation gas outlet, whereby the circulation gas in the combustion zone flows into the circulation gas outlet.

According to another embodiment, a heating device is arranged between the exhaust gas outlet and the combustion zone for heating the exhaust gas to a temperature of 800 to 1200 ℃ (in particular 1100 ℃). The heating means is preferably arranged between the exhaust gas outlet and the circulation device or the gas inlet for introducing the exhaust gas into the combustion zone. The heating device is used to heat the exhaust gases to a temperature of 800 to 1200 ℃ (in particular 1100 ℃), which has the advantage that a burner can be omitted in the combustion zone. The heating means preferably provides all the energy required for calcination. The heating means is preferably arranged outside the combustion zone such that the exhaust gases reach the temperature required for calcination already before being introduced into the combustion zone. For example, a shaft kiln has at least two or more heating devices, e.g. heating devices connected in parallel with each other and each heating a sub-stream of exhaust gas exiting via an exhaust gas outlet. The heating means preferably comprises electrical heating means, solar devices, combustion reactors and/or heat exchangers. The heating device is, for example, an electric heating device. In particular, the heating device is operated by solar energy and preferably comprises a solar receiver, in particular a photovoltaic system for generating electrical energy by solar energy. The heating means comprise, for example, a solar thermal system in which a heat exchanger fluid is heated, for example by means of solar energy, and recirculated exhaust gas is heated in the heat exchanger, preferably counter-currently to said exhaust gas. For example, the heating means comprise a solar receiver for heating the recirculating exhaust gases, in particular directly. To this end, the solar receiver comprises, for example, a portion of an exhaust gas outlet conduit. The heating device has, for example, a combustion reactor, which is preferably configured to burn renewable energy sources such as wood. The heating means preferably comprises a heat exchanger for heating the exhaust gas counter-current to the heat transfer fluid. For example, the heat transfer fluid is heated by solar energy and/or a combustion reactor.

According to a further embodiment, the combustion zone has a gas inlet for introducing exhaust gas removed via an exhaust gas outlet into the combustion zone. The gas inlet is preferably arranged separately from the recycle gas inlet in the combustion zone. For example, the gas inlet and the recycle gas inlet are arranged at the same level. The gas inlet is arranged in particular in the material-free space. The shaft kiln has, for example, a plurality of gas inlets for introducing exhaust gases into the combustion zone, the gas inlets preferably being arranged circumferentially around the combustion zone.

According to yet another embodiment, the circulation device has one or more burners. Preferably, the burner is arranged downstream of the injector such that gas flowing out of the injector into the recycle gas inlet is heated by the burner. The shaft kiln preferably has a fuel conduit for conducting fuel (such as, for example, methane) that is connected to the circulation device.

According to yet another embodiment, the shaft kiln has a cooling gas discharge device for discharging cooling air from the shaft. The cooling gas discharge device is preferably arranged separately from the circulation device and in particular is not in fluid connection with the circulation device. The cooling gas discharge device is preferably configured and arranged to completely discharge cooling air of the cooling zone from the shaft via the cooling gas discharge device such that the cooling air does not enter the combustion zone. The cooling gas discharge device is in the form of, for example, a material-free space within the cooling zone, wherein, for example, the material-free space is arranged laterally, radially around the cooling zone outside the shaft or the annular space. The cooling air discharge device is connected to, for example, a heat exchanger for heating the exhaust gas in countercurrent. The cooling air outlet device has, for example, a plurality of cooling air outlets for discharging cooling air from the shaft, which are arranged, for example, circumferentially around the shaft. The number of heat exchangers located downstream of the cooling gas discharge device corresponds in particular to the number of cooling gas outlets.

A cooling air inlet for introducing cooling air into the cooling zone is preferably arranged within the cooling zone, the cooling air inlet being connected to, for example, a compressor for generating positive pressure in the shaft kiln.

According to a further embodiment, the cooling gas discharge device is in the form of an inner drum within the cooling zone. The inner barrel preferably extends fully or partially centrally through the cooling zone such that the cooling zone is in the form of an annular well, either fully or partially. The inner barrel preferably has a cooling gas outlet extending from the inner barrel out of the shaft. In particular, the inner drum has a gas inlet in the cooling zone for introducing cooling gas from the cooling zone into the inner drum, the gas inlet preferably being arranged above the cooling gas outlet. The cooling air of the cooling zone is preferably completely discharged from the shaft via a cooling air discharge device, so that the cooling air does not enter the combustion zone.

According to a further embodiment, a heat exchanger is arranged between the exhaust gas outlet and the gas inlet of the combustion zone. In particular, two or more heat exchangers are arranged between the exhaust gas outlet and the gas inlet of the combustion zone, which heat exchangers are, for example, connected in parallel with each other and in particular each heat a substream of the exhaust gas. At least one heat exchanger is for example connected to the cooling air outlet device, in particular to the cooling gas outlet, so that the exhaust gas is heated in countercurrent to the discharged cooling air. At least one heat exchanger is for example connected to a gas outlet for discharging gas from the combustion zone such that the exhaust gas is heated in countercurrent to the gas discharged from the combustion zone.

The invention also comprises a method for burning in particular carbonate-containing material in a shaft kiln having a shaft, wherein the material flows through a material inlet into a preheating zone for preheating the material, a combustion zone for burning the material, a cooling zone for cooling the burned material, up to a material outlet, wherein cooling air is introduced into the cooling zone, wherein exhaust gas is discharged from the preheating zone of the shaft via an exhaust gas outlet, and wherein exhaust gas discharged from the preheating zone of the shaft via the exhaust gas outlet is at least partially conducted into the combustion zone. The circulating gas circulates within the combustion zone to form a forward flow combustion zone within the combustion zone.

The advantages and embodiments described with reference to shaft kiln are equally applicable to the method of burning material in a shaft kiln in terms of the corresponding method expression.

According to one embodiment, the recycle gas is discharged from the combustion zone via a recycle gas outlet, fed to the recycling device, and introduced into the combustion zone by the recycling device via a recycle gas inlet.

According to another embodiment, the circulating gas is accelerated by means of an ejector in the direction of the circulating gas inlet.

According to a further embodiment, the exhaust gas, in particular the drive gas, is at least partly led into the circulation device and is introduced into the combustion zone together with the circulation gas. A part of the flue gases discharged from the preheating zone of the shaft via the flue gas outlet is preferably introduced solely to a gas inlet arranged separately from the recycle gas inlet for introducing the gases into the combustion zone.

According to a further embodiment, the cooling air is discharged from the shaft via a cooling gas discharge device. Preferably, all the cooling air introduced into the cooling zone is completely discharged from the shaft via the cooling gas discharge device, so that in particular the cooling air does not enter the combustion zone.

According to yet another embodiment, the exhaust gas is fed to a heat exchanger before being introduced into the combustion zone. Within the combustion zone, a counter-current combustion zone and a forward-current combustion zone are preferably formed along the flow direction of the material. Positive pressure is preferably established in the shaft kiln.

Drawings

The invention will be described in more detail below based on a number of exemplary embodiments with reference to the accompanying drawings.

Fig. 1 shows two schematic views of a shaft kiln according to an exemplary embodiment, shown in a longitudinal sectional view and a longitudinal sectional view rotated by 90 °.

Fig. 2 shows two schematic views of a shaft kiln according to another exemplary embodiment, shown in a longitudinal sectional view and a longitudinal sectional view rotated by 90 °.

Fig. 3a to 3h show schematic views of the shaft kiln of fig. 1 or 2 according to another exemplary embodiment in a plurality of horizontal cross-sectional views.

Fig. 4a to 4b show two schematic views of a shaft kiln according to another exemplary embodiment in longitudinal cross-sectional view and horizontal cross-sectional view.

Fig. 5 shows a schematic view of a shaft kiln in the form of an annular well according to another exemplary embodiment in a longitudinal cross-sectional view.

Fig. 6 shows a schematic view of a shaft kiln in the form of an annular well according to another exemplary embodiment in a longitudinal cross-sectional view.

Fig. 7a to 7f show schematic diagrams of the shaft kiln of fig. 5 or 6 according to another exemplary embodiment in a plurality of horizontal cross-sectional views.

Fig. 1 shows two views of a shaft kiln 1, the shaft kiln 1 shown in the figure being preferably used for relatively low production, e.g. 250t/d. The shaft kiln 1 for burning particulate material comprises a shaft 2, the shaft 2 preferably extending in a vertical direction and, for example, having a substantially constant cross section. For example, the cross section of the shaft 2 is circular arc (round), in particular circular, or angular, in particular tetragonal. The shaft 2 is surrounded by shaft walls, which are made of, for example, steel and are adjacent to the bricked refractory inner walls. At the upper end of the shaft 2, the shaft 2 has a material inlet 3, the material inlet 3 being in the form of, for example, an upper opening of the shaft 2, in particular in the form of a lock 3, and preferably extending to the entire or a partial cross section of the shaft 2. The material inlet 3 is used for introducing material to be burned into the shaft kiln 1. The material inlet 3 in the form of a lock is preferably designed such that only the material to be burnt can enter the shaft 2, whereas ambient air cannot. The lock 3 is preferably configured to seal the shaft 2 from the environment in an airtight manner and to allow solids (such as material to be burned) to enter the shaft.

The shaft 2 has an offgas outlet 19 in the upper region for removing kiln offgas from the shaft 2. Exhaust gas is introduced from the exhaust gas outlet 19 into the exhaust gas outlet conduit 39. In the shaft 2, the material to be burnt passes through the shaft 2 from top to bottom under the influence of gravity, wherein the shaft 2 has a preheating zone 21 for preheating the material, a combustion zone 20 for burning the material and a cooling zone 22 for cooling the burnt material in the conveying direction of the material. The preheating zone 21 preferably extends from the material inlet 3 to the combustion zone 20 and serves to preheat the material prior to combustion. Unlike the preheating zone 21, in the combustion zone 20 the material is burned, in particular calcined, preferably by means of deacidification.

For example, the shaft 2 has four material-free spaces 16, 48, 49, 55, wherein the material-free space 16 which is first in the material flow direction is located in the combustion zone 20 (in particular at the transition between the combustion zone 20 and the preheating zone 21). The shaft 2 has a second material free space 55 in the combustion zone 20 and a third material free space 48 downstream of the lower region of the combustion zone 20. A fourth material free space 49 is arranged in the cooling zone 22. For example, the shaft 2 extends in four vertical sections offset parallel to each other, the material-free spaces 16, 48, 49, 55 each representing a partial cross-sectional enlargement of the shaft 2, into which material does not flow under the influence of gravity. For example, the material free spaces 16, 48, 49, 55 extend radially outwards and are partly separated from the shaft 2 by walls extending vertically from above between the material free spaces 16, 48, 49, 55 and the shaft 2.

The first material free space 16 has a gas outlet 12 for discharging exhaust gases from the combustion zone 20. For example, the second material-free space 55 in the combustion zone 20 has a gas inlet 15 for introducing the exhaust gases conveyed from the exhaust gas outlet 19 from the shaft 2 into the combustion zone 20. In addition, the second material free space 55 also has a recycle gas inlet 17 for introducing recycle gas from the combustion zone 20. The third material free space 48 has a recycle gas outlet 18 for discharging recycle gas from the combustion zone 20. The fourth material free space 49 is preferably in the form of a cooling gas discharge device and has, for example, a cooling gas outlet 36 for discharging cooling air via a cooling air discharge conduit 11 connected to the cooling gas outlet 36.

The circulating gas is a gas that circulates within the combustion zone 20. The gas is preferably discharged from the combustion zone 20 via a recycle gas outlet 18 and fed back to the recycle gas inlet 17. The circulation device 54 is arranged between the circulation gas outlet 18 and the circulation gas inlet 17, whereby the circulation gas is accelerated from the circulation gas outlet 18 into the circulation gas inlet 17 by means of the circulation device 54. The circulating gas outlet 18 is arranged downstream of the circulating gas inlet 17 in the flow direction of the material to be combusted. A negative pressure is preferably created at the recycle gas outlet 18 such that the recycle gas in the combustion zone 20 is compressed in the direction of the recycle gas outlet 18. The circulating gas entering the combustion zone 20 via the circulating gas inlet 17 flows partly counter-currently to the material to be combusted in the direction of the preheating zone 21 and partly counter-currently to the material in the direction of the circulating gas outlet 18. A forward flow combustion zone 24 is preferably formed within the combustion zone 20 between the recycle gas inlet 17 and the recycle gas outlet 18. The counter-flow combustion zone 23 is preferably formed upstream of the recycle gas inlet 17 in the flow direction of the material. The counter-current combustion zone 23 of the combustion zone 20 is preferably formed exclusively between the recycle gas inlet 17 and the preheating zone 21.

The recycle gas device 54 comprises, for example, an ejector 57, preferably in the form of a nozzle. By means of the ejector 57, the circulating gas is accelerated in the direction of the circulating gas inlet 17, creating a negative pressure at the circulating gas outlet 18, and preferably the negative pressure is adjustable.

At the lower end of the shaft 2 a material outlet 40 is arranged for removing burnt material. The material outlet 40 is, for example, a lock as described with reference to the material inlet 3. A discharge hopper 25, in particular a blanking silo, follows the cooling zone 22 in the material conveying direction and opens into a material outlet 40 for discharging material from the shaft kiln 1. For example, a discharge device 41 for discharging material from the cooling zone 22 of the shaft kiln 1 into the hopper 25 is arranged in the hopper 25. For example, the discharge device 41 is a turntable or a slide table.

The shaft kiln 1 has one or more cooling air inlets 7 for introducing cooling air into the shaft kiln 1. For example, a cooling air inlet 7 is arranged in the shaft kiln 1 in fig. 1, which introduces cooling air into the hopper 25. The cooling air is preferably blown into the discharge hopper 25 by means of a cooling air compressor 26 at a pressure of up to 500 mbar.

When the shaft kiln 1 is in operation, the material flows through the shaft 2 substantially under the force of gravity and is heat treated in countercurrent or partially concurrent flow.

The height of the shaft 2 is preferably determined by the residence time of the burnt material, which is determined by the discharge device 41 according to the method in connection with the setting of the conveying speed. These residence times are distributed over the upper preheating zone 21 after the material inlet 3, over the downwardly extending combustion zone 20 and at least over the cooling zone 22 of the discharge device 41. In the preheating zone 21, the material is preferably preheated to a temperature of up to about 800 ℃, the temperature of the combustion zone 20 being, for example, 800 ℃ to 1100 ℃, while in the cooling zone 22 the material is cooled back to about 100 ℃.

When the shaft kiln 1 is in operation, material supplied via the material feeder 3 forms a column of material in the combustion zone 20 of the shaft 2, wherein the material moves downwards under the influence of gravity and is taken out as calcination product (e.g. burnt lime) via the material outlet 40 in the region of the cooling zone 22. The material preferably fills the entire cross-section (preferably annular cross-section) of the combustion zone 20 and the cooling zone 22. The cooling gas flows through the material bed into the fourth material free space 49, in particular the cooling gas discharge device. Preferably, only the cooling gas is discharged from the shaft 2 via the cooling gas discharge device, without exhaust gases from the combustion zone 20. In particular, the cooling gas flows through the cooling zone 22 and then enters the cooling gas discharge device, so that the cooling gas is completely discharged from the shaft via the cooling gas discharge device without reaching the combustion zone 20.

The fourth material free space 49 is preferably connected to the control element 46 via a cooling air discharge duct 11, the control element 46 being in the form of, for example, a baffle for controlling the amount of gas flowing through the fourth material free space 49, in particular the amount of gas flowing through the cooling air discharge duct 11 therebehind.

The exhaust gas outlet 19 for removing exhaust gas from the preheating zone 21 is preferably connected to an exhaust gas filter 31 via an exhaust gas outlet conduit 39 for de-dusting the exhaust gas and optionally to a cooling device 32 for cooling the hot exhaust gas. The offgas from the combustion zone 20 is at least partially or completely removed from the shaft 2 via an offgas outlet conduit 39. The offgas discharged from the shaft 2 via the offgas outlet 19 and the offgas outlet duct 39 is dedusted, in particular in the offgas filter 31, and is then removed as dedusted offgas by means of the fan 33, for example, for further treatment. Optionally, the exhaust gas is cooled in a cooling device 32 downstream of the exhaust gas filter 31. The exhaust gas removed upstream or downstream of the cooling device 32 is relatively high in CO2 content and may be used, for example, for sequestration and/or further industrial use such as, for example, the production of soda, sugar or precipitated calcium carbonate.

The cooled exhaust gas is preferably partly removed and partly introduced as a driving gas (preferably downstream from the cooling device 32) into the circulation device 54 via a driving gas conduit 43. For clarity, the connection of the drive gas duct 43 to the circulation device 54 is only shown in the left view of the shaft kiln 1. The drive gas conduit 43 is preferably connected to the ejector 57 such that the drive gas is introduced into the ejector 57, the height of the ejector 57 being lower than or equal to the height of the recycle gas outlet 18. The driving gas is optionally mixed with an oxidant before entering the circulation device 54. To this end, the drive gas duct 43 is connected to the oxidant duct 14, the amount of oxidant being adjustable, for example via a metering device such as, for example, a baffle in the oxidant duct 14. The oxidizing agent is, for example, pure oxygen, air, oxygen-enriched air or a gas having an oxygen content of at least 90%.

Alternatively and not shown in fig. 1, the drive gas conduit 43 is connected to a heat exchanger 35, the heat exchanger 35 being connected to the cooling gas outlet 36 such that the drive gas 43 is heated in countercurrent to the exiting cooling air before entering the circulation device 54. In such an embodiment, the oxidant is preferably introduced into the drive gas conduit 43 upstream of the heat exchanger 35 in the direction of flow of the drive gas.

The burner 10 is optionally arranged in a second material free space 55. For example, the burner 10 takes the form of a burner lance and is connected to a fuel conduit 13 for supplying fuel to the burner 10. The amount of fuel may be regulated, for example, via a metering device such as, for example, a baffle in the fuel conduit 13. The burner 10 is optionally arranged in a circulation device 54.

For example, a portion of the exhaust gas removed via the exhaust gas outlet conduit 39 is introduced into the combustion zone 20 via, for example, the gas inlet 15 into the combustion zone 20 to provide heat to the combustion zone 20 and to regulate the combustion temperature. Such recirculating exhaust gases are preferably branched upstream of the cooling device 32 and downstream of the exhaust gas filter 31.

The recirculating exhaust gases are preferably preheated to in particular 500 to 800 c in a heat exchanger 35 operated with the exiting cooling air before entering the combustion zone 20. In order to avoid a reduction of the heat transfer amount in the heat exchanger 35 due to deposits, it may be advantageous to cool the cooling gas (e.g. at a temperature of 900 ℃) discharged via the fourth material free space 49 to below 800 ℃, preferably below 700 ℃, in advance, for example, by mixing with air. The fan 51 or the compressor, in particular a high-pressure fan, a rotary piston compressor or a screw compressor, is preferably arranged for accelerating the recirculating exhaust gases in the direction of the heat exchanger 35. It is also contemplated that the recirculated exhaust gas is fed exclusively to a single heat exchanger, heat exchanger 35, prior to being introduced into combustion zone 20. The cooling device 32 in the form of a heat exchanger is preferably arranged downstream of the branch of the exhaust gas to be removed and, for example, upstream of the fan 33 in the flow direction of the exhaust gas.

The cooling air discharge duct 11 is connected in particular to the heat exchanger 35 and optionally to a filter 50 after the heat exchanger 35, so that the cooling air discharged via the fourth material free space 49 is cooled and dedusted. To further cool the discharged cooling air, a coolant (such as air) is preferably optionally mixed with the discharged cooling air before the cooling air enters the heat exchanger 35. Upstream of the control element 46, a filter for separating dust is optionally arranged in the flow direction of the discharged cooling air. Accordingly, the heat exchanger 35, the control element 46 and optionally the filter 50 upstream or downstream of the control element 46 are arranged in succession in the cooling gas discharge conduit 11. Also, it is conceivable that the discharged cooling air is not led through the heat exchanger 35, but is used for the purpose of power generation, drying of abrasives, heating, or the like.

For example, the gas removed from the combustion zone via the first material free space 16 is directed into the second heat exchanger 52 and then into the exhaust gas outlet conduit 39 for at least partial recirculation into the combustion zone 20. For example, the shaft kiln 1 has two heat exchangers 35 and 52, wherein a portion of the exhaust gas discharged via the exhaust gas outlet 19 is supplied to each heat exchanger for heating. The amount of exhaust gas substreams is preferably set in the exhaust gas outlet conduit 39 via a control device such as, for example, a baffle or valve. The heat exchangers 35 and 52 are preferably connected in parallel.

In the heat exchanger 52 the gas discharged via the first material free space 16 heats the substream of the exhaust gas, while in the other heat exchanger 35 the cooling gas discharged via the fourth material free space 49 heats the substream of the exhaust gas, in each case counter-currently. The exhaust gas substream heated by the gas discharged from the combustion zone 20 in the heat exchanger 52 is combined with the exhaust gas substream heated by the gas discharged from the cooling zone 22 in the heat exchanger 35 and is introduced into the combustion zone 20.

The exhaust gases are heated to a temperature of about 500 c to 800 c by means of the heat exchangers 35, 52 before they are introduced into the combustion zone 20, in particular into the gas inlet 15 of the second material-free space 55. Heating means are optionally arranged between the heat exchangers 35, 52 and the gas inlet 15 of the combustion zone 20 for heating the exhaust gases to a temperature of 800 to 1200 ℃, in particular 1100 ℃. The heating device is, for example, an electric heating device. In particular, the heating device is operated by means of solar energy. It is also conceivable that the heating device comprises a heat exchanger, which heats the counter-current flowing heating medium by solar energy. The heating means preferably takes the form of a combustion reactor for combusting preferably renewable energy sources, such as wood.

Optionally, in the shaft 2 (in particular in the combustion zone 20), no further heating devices (such as burners) are provided in addition to the heating means, so that the calcination takes place entirely via the hot exhaust gases recovered in the combustion zone 20. It is also contemplated that one or more burners may be disposed in the combustion zone 20 in addition to the heating device.

Fig. 2 shows another exemplary embodiment of a shaft kiln 1, which shaft kiln 1 corresponds substantially to the shaft kiln 1 in fig. 1. Fig. 2 also shows two views of the shaft kiln 1 in order to clearly see the position of the circulation device 54. Unlike fig. 1, the shaft kiln 1 in fig. 2 has a plurality of burners, in particular side burners 38, which side burners 38 extend transversely into the shaft 2 through the wall of the shaft, for example. The side burner 38 is preferably arranged in the combustion zone 20, in particular in the counter-flow combustion zone 23. For example, all side burners 38 are arranged at the same level, preferably at the lower end region of the forward flow combustion zone 23. The side burners 38 are preferably evenly spaced from each other around the perimeter of the combustion zone 20. The side burners 38 are each connected to the fuel conduit 13 via a fuel circuit. The side burner 38 is preferably connected to a drive gas conduit 43, wherein a part of the exhaust gases conducted in the drive gas conduit 43 is branched upstream of the recirculation device 54, in particular upstream of the heat exchanger 35, and fed to the circuit for supply to the side burner 38. The side burner 38 is preferably connected to the oxidant conduit 14 for conducting oxidant to the side burner 38. In particular, an oxidizing agent is introduced into the drive gas conduit 43, the amount of oxidizing agent preferably being adjustable via a metering device.

Fig. 3a to 3h show a plurality of horizontal cross-sectional views, the cross-sectional planes of which are shown in fig. 1 and 2. Fig. 3a shows a cross section taken along the first material free space 16, wherein the gas outlet 12 for discharging gas from the combustion zone 20 is centrally arranged in the radially outward side wall of the first material free space 16. Fig. 3f shows an exemplary embodiment in which a plurality of, in particular three, gas outlets 12 are arranged in the side wall. The gas outlets 12 are preferably evenly spaced from each other, in particular arranged at the same level.

Fig. 3b and 3g each show an exemplary embodiment of a second material-free space 55, wherein, for example, in the circulation device 54, in particular in the ejector 57, a burner 10 is arranged, in particular a second burner 10 is arranged in the material-free space 55. Fig. 3g shows an exemplary embodiment, for example, in which three burners 10 are arranged in the second material-free space 55, preferably equidistant from one another, in particular at the same level.

Fig. 3c shows a horizontal cross section taken along the third material free space 48 with the recycle gas outlet 18. For example, the recycle gas outlet has a rectangular cross section with a smaller cross-sectional area than the recycle gas inlet 17.

Fig. 3d and 3h show an exemplary embodiment of a fourth material free space 49, respectively, wherein, for example, the cooling gas outlet 36 is arranged centrally in a radially outward side wall of the fourth material free space 49. In fig. 3h, for example, a plurality of, in particular three, cooling gas outlets 36 are arranged at a height level in the radially outward side wall of the fourth material free space 49 and are evenly spaced from one another.

Fig. 3e shows a horizontal cross section along the counter-flow combustion zone 23 in fig. 2, wherein the combustion zone 23 has a plurality of burners, in particular side burners 38. For example, the eight side burners 38 are arranged in a plane, and are preferably arranged in a substantially uniform manner from one another.

Fig. 4a shows another exemplary embodiment of a shaft kiln 1, wherein identical elements are identified by identical reference numerals. In fig. 4a, the material free space 16, 48, 49, 55 is in the form of an annular space. For example, the combustion zone 20, and in particular each of the counter-flow combustion zone 23 and the forward-flow combustion zone 24, and the cooling zone 22 are funnel shaped, with the upper regions of the combustion zones 23, 24 and the cooling zone 22 each having a larger diameter than the lower region.

For example, the preheating zone 21 in fig. 4a is cylindrical and its lower region extends partly into the upper region of the combustion zone 20, in particular the countercurrent combustion zone 23, so that a first material-free space 16 is formed between the outer wall of the preheating zone 21 and the inner wall of the countercurrent combustion zone 23. The upper region of the combustion zone 20 is in the form of a counter-flow combustion zone 23 and preferably extends with its lower region into the upper region of the forward-flow combustion zone 24 such that a second material-free space 55 is formed as an annular space between the outer wall of the counter-flow combustion zone 23 and the inner wall of the forward-flow combustion zone 24. The upper region of the forward flow combustion zone 24 preferably extends into the upper region of the cooling zone 22 together with the lower region thereof, thereby forming a fourth material free space 49 between the outer wall of the forward flow combustion zone 24 and the inner wall of the cooling zone 22. For example, the forward flow combustion zone 24 is formed by two funnel-shaped portions with the third material free space 48 forming an annular space therebetween. The material-free spaces 16, 48, 49, 55 are each in the form of an annular space and are each arranged circumferentially around the vertically extending shaft 2 through which the material to be combusted flows, so that no material flows through the material-free spaces 16, 48, 49, 55 but gas can flow through. According to the exemplary embodiment of fig. 1 and 2, the second material free space 55 has a recycle gas inlet 17 and the third material free space 48 has a recycle gas outlet 18.

The shaft kiln 1 in fig. 4a also has a circulation device 54, which circulation device 54 essentially corresponds to the circulation device 54 in fig. 1 and 2 and is arranged between the circulation gas inlet 17 and the circulation gas outlet 18.

The shaft kiln 1 in fig. 4a has a plurality of side burners 38, which side burners 38 essentially correspond to the side burners 38 in fig. 2. Fig. 4b shows a horizontal cross-sectional view at the cross-section shown in fig. 4 a. For example, the side burners 38 are circumferentially arranged about the combustion zone 20 and are substantially equally spaced from one another. For example, the side burners 38 have different insertion depths, wherein each two side burners 38 preferably have the same insertion depth. In particular, the side burner is mounted so as to be displaceable in the radial direction, so that the insertion depth can be adjusted.

The conduits for recirculating exhaust gases and for conducting gas flows, oxidants and fuels essentially correspond to the conduits in fig. 2 or fig. 1.

Fig. 5 shows another exemplary embodiment of a shaft kiln 1. Shaft kiln 1 is preferably used to achieve high throughput and corresponds generally to the shaft kiln of fig. 1-4, except that shaft kiln 1 in fig. 5 is in the form of an annular shaft kiln. For example, the exhaust gas is discharged via a material-free annular gap 37. In contrast to fig. 1 to 4, the second and third material-free spaces in the combustion zone 20 of the shaft 2 are preferably in the form of combustion chamber planes 8, 9, at least one combustion chamber 4, 5 being arranged in each combustion chamber plane 8, 9. In fig. 5, for example, two combustion chamber planes 8, 9 are arranged in the shaft 2. It is also conceivable that there is only one combustion chamber plane 8, 9 or more than two combustion chamber planes. The combustion chamber planes 8, 9 are described in detail with reference to fig. 7a to 7 f. For example, a burner 10 is mounted in each combustion chamber 4, 5 of the combustion chamber planes 8, 9. The burner 10 is, for example, a burner lance extending substantially horizontally into the combustion chamber 4, 5. The combustion chambers 4, 5 each have a gas inlet for introducing recirculated exhaust gas. The exhaust gases are preferably mixed with the oxidant via an oxidant conduit 14 before being introduced into the combustion chambers 4, 5. The exhaust gas outlet conduit 39 is preferably configured with reference to the above-mentioned figures such that a portion of the exhaust gas is branched into drive gas via the drive gas conduit 43 and is preferably fed to the ejector 57 of the circulation device via the heat exchanger 35.

A counter-current combustion zone 23 is preferably formed in the combustion zone 20, wherein the material flows through the shaft 2 counter to the gas flow. For example, a counter flow combustion zone 23 is formed above the lower combustion chamber plane 9. In addition, a downstream combustion zone 24 is formed in the combustion zone 20, wherein the gas flow and the material flow through the shaft 2 in the same direction. For example, a forward flow combustion zone 24 is formed below the lower combustion chamber plane 9. The arrangement of the forward flow combustion zone 24 and the reverse flow combustion zone may vary depending on the flow rates of the material and gas streams, wherein the reverse flow combustion zone 23 is preferably formed always above the forward flow combustion zone 24.

In particular for forming the forward flow combustion zone 24, the shaft kiln 1 in fig. 5 has a circulation device 54 for circulating a circulating gas in the combustion zone 20. For example, the circulation device 54 comprises an inner cylinder 58 arranged therein concentrically with the shaft 2. An inner drum 58 is arranged within the combustion zone 20 and extends from the forward combustion zone 24 to the reverse flow combustion zone 23, preferably into the preheating zone 21 or in particular to the boundary between the preheating zone 21 and the combustion zone 20, and extends through the borehole wall out of the shaft 2 via one or more outlets 59. The arrangement of one or more outlets 59 is shown in fig. 7 a. The inner barrel 58 extends through the borehole wall 2, for example to the gas outlet or beyond the gas outlet, for discharging gas from the shaft 2. In the forward flow combustion zone 24, the inner barrel has a gas inlet for introducing gas from the forward flow combustion zone 24 into the inner barrel 58. The gas inlet has the function of a recycle gas outlet 18 with reference to the above figures. The recycle gas is discharged from the combustion zone 20, in particular the forward flow combustion zone 24, via the recycle gas outlet 18 and is fed to the recycle gas inlet 17 for introducing the recycle gas into the combustion zone 20 via the injector 57. The gas outlets are preferably arranged at the level of the height of the combustion zone 20. The combustion zone 20 of the shaft 2 is preferably at least partially or wholly in the form of an annular space arranged concentrically with the inner barrel 58 of the circulation device 54. The inner tube 58 is connected to the ejector 57 so that the circulation gas discharged through the inner tube 58 flows into the ejector 57. The circulation device 54 creates a negative pressure at the circulation gas outlet 18 such that the circulation gas within the combustion zone 20 flows from the circulation gas inlet 17 to the circulation gas outlet 18 and forms the forward flow combustion zone 24.

For cooling the inner cylinder 58, the shaft 2 preferably has a cooling air inlet through which cooling air is introduced into the cooling air duct 47 from above the discharge device 41 by means of the cooling air compressor 27. The cooling air duct 47 preferably extends along the inner barrel 58, in particular along the outer wall of the inner barrel 58, and preferably leads to the cooling air discharge duct 11. The inner barrel 58 is particularly closed at the top such that no material to be combusted enters the inner barrel 58. The combustion zone 20 has in particular a circular cross section, wherein the width of the ring is about 0.5m to 2m, preferably about 1m.

The shaft 2 also has a cooling gas discharge 29 for removing at least part of the cooling air from the shaft 2. For example, the cooling air discharge device 29 of the shaft kiln 1 in fig. 5 takes the form of an annular space surrounding the lower part of the combustion zone 20, in particular the forward flow combustion zone 24. A cooling gas discharge device 29 is formed between the outer wall of the forward flow combustion zone 24 and the inner wall of the cooling zone 22 and is free of material when the shaft kiln 1 is in operation. All of the cooling air flowing through the cooling zone 22 is discharged via the cooling gas outlet 36 and fed to the heat exchanger 35, preferably by means of the cooling air discharge conduit 11, to heat the recirculating exhaust gases. Downstream of the heat exchanger 35, the cooling air is dedusted and removed by means of a filter 50. As with reference to fig. 1, the amount of cooling air to be discharged may be adjusted via the control element 46.

The shaft kiln 1 optionally also has an upper inner barrel 6 extending from the combustion zone 20 at least partly through the preheating zone 21 and arranged above the cooling gas discharge device 29. The upper inner cylinder 6 has an outlet 12 for discharging gas from the shaft 2. As with the above figures, when the shaft kiln 1 is in operation, the upper inner barrel 6 serves to equalize the material flow in the preheating zone 21 and has the function of a first material free space 16. Gas is removed from the combustion zone 20, in particular the counter-current combustion zone 23, from the shaft 2 via the upper inner drum 6 via the gas outlet 12 and is preferably fed to a heat exchanger 52 for heating the recirculating exhaust gases before they enter the combustion zone 20. A cooling air inlet for cooling the upper inner drum 6 is preferably arranged in the preheating zone 21. The cooling air, preferably accelerated by means of a fan 28, flows through the cooling air inlet into a circuit arranged around the preheating zone 21 and/or into a cooling air duct at least partially installed in the upper inner drum 6. For example, cooling air is fed to cooling air duct 47.

Fig. 6 shows another embodiment of a shaft kiln substantially corresponding to that in fig. 5. Unlike fig. 5, the shaft kiln 1 in fig. 6 has a cooling gas discharging device 29, but the cooling gas discharging device 29 has a lower inner cylinder 53 including a cooling gas outlet 36. The lower inner drum 53 is disposed below the inner drum 58 of the circulation device 54 and extends through the cooling zone 22. The lower inner cylinder 53 has a gas inlet for introducing cooling air into the lower inner cylinder 53, which gas inlet is arranged above the cooling gas outlet 36.

The horizontal cross section of the shaft kiln 1 in fig. 5 and 6 is shown in fig. 7a to 7f, and the sectional plane is shown in fig. 5 and 6. Fig. 7a shows an outlet 59 for discharging the recycle gas from the inner barrel 58 into the ejector 57. For example, the inner barrel 58 has four outlets 59, which outlets 59 extend radially outwardly in a star shape in a uniformly spaced manner from one another. Each outlet 59 is connected to an ejector 57, and the discharged recycle gas is fed to the recycle gas inlet 17 via the ejector 57.

Fig. 7b shows a horizontal cross section taken along the upper combustion chamber plane 8. For example, the combustion chamber plane 8 has four combustion chambers 4, each combustion chamber 4 having a burner 10, preferably arranged in a star shape in a combustion zone 20, in particular a counter-flow combustion zone 23, and uniformly spaced from each other. It is also conceivable that one or more combustion chamber planes have more or less than four combustion chambers 4. For example, the combustion chambers 4 of the combustion chamber plane 8 are arranged offset from each other at an angle of about 45 °. Arrangements other than this are also conceivable. The combustion chamber 4 is preferably delimited by lateral transverse walls and is open at the top and bottom in the direction of the shaft 2, so that the gas heated in the combustion chamber 4 flows into the combustion zone 20. Passages are arranged between adjacent combustion chambers 4 so that material and gas can flow along the shaft 2. Another embodiment is shown in fig. 7e, in which a plurality of side burners 38 are arranged in each case between the combustion chambers 4. For example, two side burners 38 are arranged in each case between two combustion chambers 4, but a different number, such as one or three side burners 38, is also possible.

Fig. 7c shows a cross section taken along the second combustion chamber plane 9, for example, the second combustion chamber plane 9 having four combustion chambers 5 arranged and configured as described with reference to fig. 7b, except that each combustion chamber has a circulating gas inlet 17, each inlet 17 being connected to a respective injector 57 (not shown). Thus, the shaft kiln 1 has, for example, four circulating gas inlets 17 arranged circumferentially around the combustion zone 20. Another embodiment is shown in fig. 7f, in which a plurality of side burners 38 are arranged in each case between the combustion chambers 5. For example, two side burners 38 are arranged in each case between two combustion chambers 5, but a different number, such as one or three side burners 38, is also possible.

Fig. 7d shows a cross-sectional view taken in the plane of the cooling gas outlet 36 in fig. 6. For example, the shaft kiln 1 has only one cooling gas outlet 36 for discharging cooling gas from the cooling zone 22. The cooling gas outlet 36 is in particular tubular and extends radially outwardly from the lower inner barrel 53.

List of reference numerals

1. Shaft kiln

2. Vertical shaft

3. Material inlet/gate lock

4. Combustion chamber with upper combustion chamber plane

5. Combustion chamber with lower combustion chamber plane

6. Upper inner cylinder

7. Cooling air inlet

8. Upper combustion chamber plane

9. Lower combustion chamber plane

10. Burner with a burner body

11. Cooling air exhaust duct

12. Gas outlet

13. Fuel conduit

14. Oxidant conduit

15. Gas inlet

16. First material-free space

17. Recycle gas inlet

18. Recycle gas outlet

19. Exhaust gas outlet

20. Combustion zone

21. Preheating zone

22. Cooling zone

23. Countercurrent combustion zone

24. Concurrent combustion zone

25. Discharging hopper

26. Cooling air compressor

27. Cooling air compressor

28. Compressor/fan

29. Cooling air exhaust device

30. Compressor/fan

31. Exhaust gas filter

32. Cooling apparatus

33. Compressor/fan

34. Compressor/fan

35. First heat exchanger

36. Cooling air outlet

37. Annular gap

38. Side burner

39. Exhaust gas outlet conduit

40. Material outlet/gate lock

41. Discharge device

43. Drive gas conduit

44. Control apparatus

46. Control element

47. Cooling air duct

48. Third material-free space

49. Fourth material-free space

50. Filter device

51. Compressor/fan

52. Second heat exchanger

53. Lower inner cylinder

54. Circulation device

55. Second material-free space

57. Ejector device

58. Inner cylinder

59. An outlet

Claims

1. Shaft kiln (1) for burning in particular carbonate-containing material, with a shaft (2), comprising in the flow direction of the material:

a material inlet (3),

a preheating zone (21) for preheating the material,

a combustion zone (20) for combusting said material,

a cooling zone (22) for cooling the burned material,

and a material outlet (40) for discharging the material from the shaft kiln (1),

wherein the shaft kiln (1) has an exhaust gas outlet (19) for discharging exhaust gas from a preheating zone of the shaft (2) and

wherein the exhaust gas outlet (19) is connected to the combustion zone (20) for recovering the exhaust gas,

it is characterized in that the method comprises the steps of,

the shaft kiln (1) has a circulation device (54) for circulating a circulating gas in the combustion zone (20) and forming a concurrent combustion zone (24) in the combustion zone (20).

2. Shaft kiln (1) according to claim 1, wherein the combustion zone (20) has a circulating gas outlet (18) for discharging circulating gas from the combustion zone (20) and a circulating gas inlet (17) for introducing circulating gas discharged via the circulating gas outlet (18) into the combustion zone (20), and wherein the circulating device (54) is connected to the circulating gas inlet (17) and the circulating gas outlet (18).

3. Shaft kiln (1) according to any of the preceding claims, wherein the circulation device (54) has an ejector (57) for accelerating the circulation gas into the combustion zone (20) in the direction of the circulation gas inlet (17).

4. Shaft kiln (1) according to any of the preceding claims, wherein the circulation device (54) is connected to the exhaust gas outlet (19) via a drive gas conduit (43) for conducting the exhaust gas such that the exhaust gas is at least partly introduced into the combustion zone (20) together with the circulation gas.

5. Shaft kiln (1) according to claim 4, wherein the drive gas conduit (43) is connected to a heat exchanger (35) for heating the exhaust gases.

6. Shaft kiln (1) according to claim 4 or 5, wherein the drive gas conduit (43) is connected to the injector (57) such that the exhaust gas is introduced into the injector (57) together with the circulating gas.

7. Shaft kiln (1) according to any of the preceding claims, wherein a heating device (54) is arranged between the exhaust gas outlet (19) and the combustion zone (20), the heating device (54) being used for heating the exhaust gas to a temperature of 800 to 1200 ℃, in particular 1100 ℃.

8. Shaft kiln (1) according to any of the preceding claims, wherein the combustion zone (20) has a gas inlet (15), the gas inlet (15) being for introducing exhaust gas discharged via the exhaust gas outlet (19) into the combustion zone (20).

9. Shaft kiln (1) according to any of the preceding claims, wherein the circulation device (54) has a burner (10).

10. Shaft kiln (1) according to any of the preceding claims, wherein the shaft kiln (1) has a cooling gas discharge device (29), the cooling gas discharge device (29) being adapted to discharge cooling air from the shaft (2).

11. Shaft kiln (1) according to claim 10, wherein the cooling gas discharge device (29) is in the form of an inner cylinder within the cooling zone (22).

12. Shaft kiln (1) according to any of the preceding claims, wherein a heat exchanger (35, 52) is arranged between the exhaust gas outlet (19) and the gas inlet (15) of the combustion zone (20).

13. A method for burning in particular carbonate-containing material in a shaft kiln (1) having a shaft (2), wherein the material flows via a material inlet (3) into a preheating zone (21) for preheating the material, a combustion zone (20) for burning the material and a cooling zone (22) for cooling the burned material up to a material outlet (40),

wherein cooling air is introduced into the cooling zone (22),

wherein the exhaust gas is discharged from the preheating zone of the shaft (2) via an exhaust gas outlet (19) and

wherein the exhaust gases discharged from the preheating zone of the shaft (2) via the exhaust gas outlet (19) are at least partially conducted into the combustion zone (20),

it is characterized in that the method comprises the steps of,

a circulating gas circulates within the combustion zone (20) to form a forward flow combustion zone (24) within the combustion zone (20).

14. A method according to claim 13, wherein a recycle gas is discharged from the combustion zone (20) via a recycle gas outlet (18), fed to a recycle device (54), and introduced into the combustion zone (20) by the recycle device (54) via a recycle gas inlet (17).

15. The method according to any one of claims 13 and 14, wherein the circulating gas is accelerated in the direction of the circulating gas inlet (17) by means of an ejector (57).

16. The method according to any one of claims 13 to 15, wherein the exhaust gas is at least partially led into the recirculation device (54) and is introduced into the combustion zone (20) together with the recirculation gas.

17. The method according to any one of claims 13 to 16, wherein the cooling air is discharged from the shaft (2) via a cooling gas discharge device (29).

18. A method according to any one of claims 13 to 17, wherein the exhaust gas is fed to a heat exchanger (32, 35) before being introduced into the combustion zone (20).