WO2022229120A1

WO2022229120A1 - Lime kiln system for burning carbonate rock, and method for converting a ggr shaft kiln into a lime kiln system comprising a shaft kiln

Info

Publication number: WO2022229120A1
Application number: PCT/EP2022/060931
Authority: WO
Inventors: Hannes Piringer; Patrick Bucher; Roger Wallimann
Original assignee: Maerz Ofenbau Ag; Thyssenkrupp Industrial Solutions Ag; Thyssenkrupp Ag
Priority date: 2021-04-27
Filing date: 2022-04-25
Publication date: 2022-11-03

Abstract

The invention relates to a lime kiln system (4) comprising at least one shaft kiln (1) for burning and cooling material, such as carbonate rock. The lime kiln system (4) comprises two shafts (2a, b) and a channel (19) which extends between the two shafts (2a, b), and the shaft kiln (1) comprises precisely one of the shafts (2a, b). The shaft (2a, b) has a material inlet (3) for admitting material to be burned into the shaft (2a, b) and, in the flow direction of the material, a pre-heating zone (21) for preheating the material, a burning zone (20) for burning the material, a cooling zone (22) for cooling the material, and a material outlet (40) for discharging the material out of the shaft (2a, b), wherein the channel (19) has a closure device (18) for closing the channel (19) in terms of gas flow so that a gas flow between the two shafts (2a, b) through the channel (19) is prevented by the closure device (18). The invention also relates to a method for converting a parallel flow counter current regenerative shaft kiln comprising two shafts (2a, b), which are connected together in terms of gas flow via a channel (19), into a lime kiln system (4) comprising at least one shaft kiln (1), each of which has precisely one shaft (2a, b), said method at least having the step of: - closing the channel (19) in a gas-tight manner by means of a closure device (18).

Description

Lime kiln system for burning carbonate rock and method of converting a PFR shaft kiln to a lime kiln system with a shaft kiln

The invention relates to a lime kiln system with at least one shaft kiln. The invention also relates to a method for converting a cocurrent-countercurrent regenerative shaft kiln (PFR shaft kiln) into a lime kiln system with at least one shaft kiln with exactly one shaft.

The firing of carbonate rock in a PFR shaft kiln has been known for about 60 years. Such a PFR shaft furnace, known for example from WO 2011/072894 A1, has two vertical, parallel shafts that work cyclically, only one shaft, the respective combustion shaft, being burned while the other shaft works as a regenerative shaft. The combustion shaft is supplied with oxidizing gas in cocurrent with the material and fuel, with the resulting hot exhaust gases being conducted together with the heated cooling air supplied from below via the overflow channel into the exhaust shaft, where the exhaust gases are discharged upwards in countercurrent to the material and the preheat the material. The material is usually fed into the shaft from above together with the oxidizing gas, with fuel being injected into the combustion zone.

In each shaft, the material to be burned usually passes through a preheating zone for preheating the material, a subsequent firing zone in which the material is burned and a subsequent cooling zone in which cooling air is supplied to the hot material.

In the future, it will be required to reduce and preferably completely avoid CO2 emissions into the atmosphere. When lime is calcined in conventional lime shaft kilns, about 1 ton of CO2 is produced per ton of lime, which is released into the atmosphere with the exhaust gas. In the future, the exhaust gas will no longer be released into the atmosphere but will be used for another purpose. One possibility is to produce methane or methanol from the CO2 in the exhaust gas in the future, or alternatively to sequester the CO2. So far, the CO2 concentrations in the exhaust gas have been around 20 to 25 percent by volume. Starting from this is a downstream Plant for the production of methane or methanol or an alternative sequestration very expensive, since the C02 would have to be separated by means of an amine wash.

Based on this, it is the object of the present invention to specify a shaft furnace for burning carbonate rock, with which lime can be produced in a simple manner, while at the same time a very high CO2 concentration in the exhaust gas is achieved, so that CO2 separation from the exhaust gas is as low as possible costs is made possible

According to the invention, this object is achieved by a device having the features of independent device claim 1 and by a method having the features of independent method claim 10 . Advantageous developments result from the dependent claims.

According to a first aspect, the invention comprises a lime kiln system having at least one shaft kiln for burning and cooling material such as carbonate rocks, the lime kiln system comprising two shafts and a duct extending between the two shafts. The shaft kiln comprises exactly one of the shafts of the lime kiln system, the shaft having a material inlet for admitting material to be burned into the shaft and, in the direction of flow of the material, a preheating zone for preheating the material, a firing zone for burning the material, a cooling zone for cooling the material and has a material outlet for discharging the material from the chute. The duct opens into the combustion zone and/or the cooling zone and has a closure device for the gas-technical closure of the duct, so that a gas flow between the two shafts through the duct is prevented by means of the closure device.

The material to be burned is preferably limestone or dolomite with a grain size of 10 to 200 mm, preferably 15 to 120 mm, most preferably 30 to 100 mm. The cooling gas is air, for example. The lime kiln system is preferably a shaft kiln that can be operated as a cocurrent-countercurrent regenerative shaft kiln, the channel connecting the shafts, in particular the combustion zones of the shafts, being closed. The lime kiln system has at least one shaft kiln. For example, the shaft kiln system has two shaft kilns, each of which includes exactly one of the shafts of the lime kiln system. The shaft furnaces are preferably separated from one another in terms of gas technology and, in particular, can be operated separately from one another for burning material.

The shaft of the at least one shaft kiln of the lime kiln system preferably has a material inlet for letting material to be burned into the shaft, the material inlet being located in particular at the upper end of the shaft so that the material falls into the shaft under the force of gravity. The material inlet and/or the material outlet is/are designed in particular as a lock for letting in and/or letting out material into the shaft furnace. A material inlet designed as a lock is preferably designed in such a way that only the raw material to be burned gets into the shaft, but not the ambient air. The lock is preferably designed in such a way that it seals the shaft airtight against the environment and allows solids, such as the material to be burned, to enter the shaft.

In the flow direction of the material, following the material inlet, the material flows through a preheating zone for preheating the material to a temperature of, for example, approximately 600°C to 800°C. The firing zone is preferably directly connected to the preheating zone and is used for firing the material, which is preferably heated to a temperature of approximately 900°C to 1600°C. The cooling zone is preferably directly connected to the firing zone and is used to cool the fired material to a temperature of 100° C., for example. The material outlet is arranged, for example, in an outlet hopper adjoining the cooling zone, with the material outlet having, for example, a turntable or pusher tables for discharging material from the cooling zone into the outlet hopper. The cooling gas is preferably a cooling gas inlet in the Blow in the cooling zone of the shaft furnace. The cooling gas inlet is preferably arranged in the cooling zone, in particular below the turntable.

A plurality of burners, in particular burner lances, are preferably arranged in the combustion zone of the shaft. It is also conceivable that the shaft has a plurality of side burners that extend through the shaft wall into the combustion zone. The side burners are preferably designed as burner lances and are in particular tubular. They serve to conduct fuel and preferably an oxidizing agent which is introduced into the combustion zone together with exhaust gas.

The closure device preferably extends over the entire cross section of the channel. The gas-technical closure of the channel by means of a closure device enables the separate operation of the two shafts of the lime kiln system.

According to a first embodiment, the closing device comprises a wall or a steel sheet. The wall preferably has refractory bricks. The steel sheet preferably has a refractory coating and/or a refractory lining and, if required, a cooling device. The closure device is preferably permanently installed in the channel. It is also conceivable for the closure device to be releasably installed in the duct, so that a gas-related connection of the shafts via the duct is possible if required. The closure device is arranged, for example, centrally in the channel. The duct has, for example, a plurality of closure devices which are arranged in the duct. For example, a closure device is arranged at each end of the channel in front of the inlet into the respective shaft.

According to a further embodiment, the shaft furnace has an exhaust gas outlet for discharging exhaust gas from the shaft, and wherein the exhaust gas outlet for recirculating the exhaust gas is connected to the combustion zone of the respective shaft. The exhaust gas outlet is preferably arranged in the upper area of the shaft, in particular in the preheating zone or in the upper area of the combustion zone. That Exhausted flue gas is preferably returned to the stack from which it was withdrawn. Preferably, only part of the flue gas discharged from the stack is returned to the stack. Another part of the flue gas discharged from the stack is sent, for example, to further treatment such as sequestration. The exhaust gas preferably consists of CO 2 and optionally H 2 O.

The use of oxygen as an oxidizing agent makes it possible to produce a process gas with a CO 2 content of more than 90% based on dry gas. Furnace exhaust gas is also fed to the burners to avoid excessively high combustion temperatures. In the case of a process exhaust gas with a CO2 content of more than 90%, it is possible to use this cost-effectively for the production of methanol or methane or alternatively for sequestration. Alternatively, exhaust gas with a lower CO 2 content, for example 45% for soda production or 35% for sugar production or 30% for the production of precipitated calcium carbonate, can also be generated with the shaft furnace described above.

According to a further embodiment, the shaft has a cooling gas extraction device for letting out cooling gas from the shaft. The cooling gas discharge device preferably has a plurality of cooling gas outlets for discharging the cooling gas from the shaft, which preferably each or together open into a cooling gas discharge line for conducting the cooling gas. The cooling gas is preferably admitted into the cooling zone of the shaft via a cooling gas inlet and preferably completely discharged from the shaft via the cooling gas discharge device, so that in particular no cooling gas reaches the combustion zone or the preheating zone from the cooling zone.

For example, the content of oxygen and/or CO2 in the exhaust gas and/or the cooling gas is determined, with the amount of oxidizing agent supplied to the shaft and/or the amount of cooling gas being discharged from the cooling zone of the shaft being controlled via the cooling gas extraction device. The shaft furnace preferably has a gas analysis device for determining the oxygen and/or the CO content in the exhaust gas and/or cooling gas. The gas analysis device is arranged, for example, in the exhaust gas line. A gas analysis device is optionally or additionally arranged in the cooling gas discharge line, in particular downstream of the heat exchanger and, for example, of the filter. The gas analysis device is connected in particular to a control device for transmitting the determined oxygen and/or CO ₂ content of the exhaust gas and/or the cooling gas.

The oxidizing agent line preferably has a control element, such as a valve or a flap, via which the amount of oxidizing agent in the shaft can be adjusted. The control element is preferably connected to the control device, the control device being designed in particular in such a way that it regulates the amount of oxidizing agent in the shaft depending on the oxygen and/or CO ₂ content of the exhaust gas determined by the gas analysis device. The control device is preferably designed in such a way that it compares the oxygen and/or CO ₂ content determined by means of the gas analysis device with a respective predetermined limit value or limit range and, if the determined value deviates from the limit value or limit range, the quantity of oxidizing agent in increases or decreases the shaft.

The control is used in particular for complete combustion of the fuel that is fed to the shaft furnace via the fuel line. This prevents an undesirably high proportion of oxygen in the exhaust pipe. To control the desired C0 ₂ content in the exhaust pipe, the C0 ₂ content is also measured.

The cooling gas discharge line preferably has a regulating element, such as a valve or a flap, via which the quantity of cooling gas to be discharged via the cooling gas discharge device can be adjusted. The control element is preferably connected to the control device, with the control device being designed in particular in such a way that it determines the quantity of cooling gas discharged via the cooling gas extraction device as a function of the oxygen concentration determined by means of the gas analysis device. and/or regulates the C0 content of the cooling gas. The control device is preferably designed in such a way that it compares the oxygen and/or CO ₂ content determined by means of the gas analysis device with a respective predetermined limit value or limit range and, if the determined value deviates from the limit value or limit range, the quantity via the cooling gas extraction device increased or decreased cooling gas to be discharged.

The control is used in particular to remove the cooling gas from the shaft furnace as completely as possible while at the same time having as little or preferably no CO2 as possible in the cooling gas discharge line.

According to a further embodiment, the cooling air extraction device comprises a material-free space within the cooling zone. The material-free space is designed, for example, as an inner cylinder or annular space within the cooling zone. The inner cylinder is arranged centrally within the shaft, for example, and preferably extends from the cooling zone into the firing zone and optionally into the preheating zone, so that the cooling zone, the firing zone and optionally at least part of the preheating zone are designed as an annular shaft. This construction makes it easier to distribute the heat from the side burners evenly over the cross-section of the shaft.

The inner cylinder preferably has a cooling duct extending therethrough for directing cooling air through the inner cylinder. The cooling gas extraction device comprises, for example, at least part of the channel closed by means of the closing device, the cooling gas outlet being arranged at least partially or completely within the closed channel.

The cooling gas extraction device is preferably designed in such a way that it discharges all of the cooling gas from the shaft, so that preferably no cooling gas enters the combustion zone. In particular, the cooling gas extraction device is connected to a control element, such as a flap or a valve, for adjusting the amount of cooling gas to be extracted. According to a further embodiment, a heat exchanger for heating the exhaust gas is arranged between the exhaust gas outlet and the combustion zone. The heat exchanger is, for example, a countercurrent heat exchanger, with the exhaust gas being heated in countercurrent to a further gas or fluid flow. The heat exchanger is preferably designed in such a way that it heats the exhaust gas in particular to a temperature of 400°C to 800°C, preferably 600°C.

According to a further embodiment, the shaft is designed as an annular shaft and has a central displacement body which extends from the cooling zone into the combustion zone. The displacement body is designed, for example, as an inner cylinder and preferably has a cooling air channel that extends centrally through the displacement body in the vertical direction. The displacement body preferably extends from the cooling zone into the firing zone and optionally into the preheating zone, so that the cooling zone, the firing zone and optionally at least part of the preheating zone are designed as an annular shaft. A ring chute allows for even distribution and thermal treatment of the material.

According to a further embodiment, a direct current combustion zone is formed within the combustion zone. Within the co-current burning zone, the gas preferably flows in the same direction as the flow of material through the burning zone of the stack. In addition to the cocurrent firing zone, a countercurrent firing zone is preferably formed within the firing zone. In the countercurrent combustion zone, the material preferably flows through the stack counter to the gas flow. The countercurrent combustion zone is formed in particular above the cocurrent combustion zone and preferably above the burners of the combustion zone.

An overpressure is set inside the shaft, for example. The overpressure is, for example, about 300 mbar. To generate the overpressure, cooling gas and the recirculated exhaust gas are preferably blown into the shaft via one or more fans or compressors.

According to a further embodiment, the shaft furnace has an oxidizing agent line for conducting oxidizing agent, in particular one rich in oxygen Gas, into the burn zone. The oxidizing agent line is preferably connected to an exhaust gas line which is connected to the exhaust gas outlet, so that the oxidizing agent is introduced into the combustion zone together with the exhaust gas. Preferably, the off-gas line and the oxidant line are connected to the burner lances for directing the off-gas and oxidant to the burner lances. For example, the combustion zone has an oxidant inlet which is connected to the oxidant line so that the exhaust gas and the oxidant are introduced into the combustion zone separately from one another.

The oxidizing agent is, for example, pure oxygen or an oxygen-rich gas with an oxygen content of at least 70 to 95%, preferably 90%.

The invention also includes a method for converting a cocurrent countercurrent regenerative shaft kiln with two shafts, which are gas-connected to one another via a duct, to form a lime kiln system with at least one shaft kiln, each with exactly one shaft. The method has at least the step of sealing the channel leading into the combustion zone and/or the cooling zone in a gas-tight manner by means of a sealing device.

The embodiments and advantages described with reference to the lime kiln system also apply in accordance with the method to the method for converting a cocurrent/countercurrent regenerative shaft kiln.

According to one embodiment, the closing of the channel comprises laying a stone wall or inserting a steel sheet. For example, the channel is at least partially removed.

According to a further embodiment, a cooling gas extraction device is arranged in at least one shaft, the cooling gas extraction device having at least one material-free space and a cooling gas outlet for discharging cooling gas from the respective shaft. According to a further embodiment, an exhaust gas outlet for discharging exhaust gas from the respective shaft is formed in at least one shaft. The flue gas outlet is preferably formed at the top end within the preheating zone of the stack.

According to a further embodiment, the exhaust gas outlet of the shaft is gas-connected to the combustion zone of the respective shaft.

According to a further embodiment, the exhaust gas outlet is connected to a heat exchanger upstream of the combustion zone in the flow direction of the exhaust gas.

According to a further embodiment, the cooling gas outlet of the cooling gas extraction device is gas-technically connected to the heat exchanger, so that the cooling gas can flow through the heat exchanger for heating the exhaust gas and in countercurrent thereto.

Description of the drawings

The invention is explained in more detail below on the basis of several exemplary embodiments with reference to the attached figures.

1a shows a schematic representation of a lime kiln system with a shaft kiln in a sectional view according to an exemplary embodiment.

Fig. 1b to 1e each show schematic representations of the lime kiln system of Fig.

1a in cross-sectional views at the cutting planes marked in Fig. 1a.

2a, b shows a schematic representation of a lime kiln system with a shaft kiln in two longitudinal sectional views according to a further embodiment. 2c to 2e each show schematic representations of the lime kiln of FIGS. 2a and b in cross-sectional views at the sectional planes marked in FIG. 2a.

1a shows a lime kiln system 4 with a shaft kiln 1, the lime kiln system 4 comprising two parallel and vertically aligned shafts 2a, b. The shafts 2a, b of the lime kiln system 4 are designed differently, for example. In the exemplary embodiment, the lime kiln system 4 has a shaft kiln 1 which includes the right-hand shaft 2b. The shaft furnace 1 has exactly one shaft 2b. However, it is also conceivable that the lime kiln system 4 comprises two shaft kilns, each of which has exactly one of the shafts 2a, b. The shafts 2a, b can be constructed essentially identically. Lime kiln system 4 is a converted cocurrent/countercurrent regenerative shaft kiln (PFR shaft kiln). The lime kiln system 4 of Fig. 1a is a kiln formerly operated as a PFR shaft kiln, which has been converted into a lime kiln system 4 with, for example, a shaft kiln 1 with exactly one shaft 2b, with the shaft kiln 1 comprising the right-hand shaft 2b of the former PFR shaft kiln. It is also conceivable that the PFR shaft kiln is converted into a lime kiln system 4 with two shaft kilns 1, each of which includes exactly one of the shafts 2a, b. In the exemplary embodiment in FIG. 1, only the right-hand shaft 2b has been converted and can be operated as part of the shaft furnace 1, with the left-hand shaft 2a corresponding, for example, to a shaft 2a of a PFR shaft furnace. It is also conceivable that both shafts 2a, b are converted and correspond to the right-hand shaft 2b.

The right shaft 2b each has a material inlet 3 for letting in material to be burned into the shaft 2b of the shaft furnace 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. The material inlet 3 is arranged, for example, at the upper end of the chute 2b, so that the material falls through the material inlet 3 into the chute 2b due to the force of gravity. The material inlet 3 is designed, for example, as an upper opening of the shaft 2b and in particular as a lock 3 and preferably extends over all or part of the cross section of the shaft 2b. A material inlet designed as a lock 3 is preferably designed in such a way that only the raw material to be burned enters the shaft 2b, but not the ambient air. The lock 3 is preferably designed in such a way that it seals the shaft 2b airtight against the environment and allows solids, such as the material to be burned, to enter the shaft.

The shaft 2b preferably has an exhaust gas outlet 6 for discharging exhaust gases from the shaft 2b. The exhaust gas outlet 6 is followed by an exhaust gas line 39 for conducting the exhaust gas drawn off from the shaft 2b.

A material outlet 40 for discharging the burned material is arranged at the lower end of the shaft 2b. The material outlet 40 is, for example, a lock as described with reference to the material inlet 3 . The burned material is fed, for example, into an outlet funnel 25, which is followed by the material outlet 40 of the shaft 2b. The outlet funnel 25 is embodied in the form of a funnel, for example. The outlet funnel 25 preferably has a cooling gas inlet 23 for admitting cooling gas into the shaft 2b. The cooling gas is preferably fed into the cooling gas inlet by means of a compressor 33 .

During operation of the shaft furnace 1, the material to be burned flows from the top downwards through the shaft 2b, with a gas flow, preferably the cooling air and the combustion gases, flowing from the bottom upwards, in countercurrent to the material, through the shaft 2b. The furnace exhaust gas is discharged through the exhaust gas outlet 6 from the shaft 2b.

Below the material inlet 3, in the flow direction of the material, is the preheating zone 21 of the shaft 2b. In the preheating zone 21, the material is preferably preheated to about 700°C. The shaft 2b is preferably filled with material to be burned. The material is preferably fed into the shaft 2b above the preheating zone 21 . At least a part of the preheating zone 21 and the part of the respective shaft 2b adjoining it in the flow direction of the material are surrounded by a refractory lining, for example. The combustion zone 20 adjoins the preheating zone 21 in the flow direction of the material. In the combustion zone 20, fuel is burned and the preheated material is fired at a temperature of about 1100°C. The lime kiln system 4 has a channel 19 which extends between the two shafts 2a, b. In particular, there is no material to be burned in the channel 19 .

A plurality of burner lances 10 are optionally arranged in the combustion zone 20 and each serves as an inlet for fuel, such as a fuel gas, oil or ground solid fuel. The shaft furnace 1 has, for example, a cooling device for cooling the burner lances 10 . The cooling device comprises, for example, a plurality of cooling air ring lines which extend in a ring shape around the shaft area in which the burner lances 10 are arranged. Cooling air or a liquid such as cooling water or cooling water mixed with an antifreeze or thermal oil preferably flows through the cooling air ring lines to cool the burner lances 10.

A plurality, for example twelve, burner lances 10 are preferably arranged in the shaft 2b and are spaced apart from one another essentially uniformly. By way of example, the burner lances 10 are arranged in the combustion zone 20 and extend in particular essentially in the radial direction through the shaft wall into the combustion zone 20 . The ends of the burner lances 10 of the shaft 2b are preferably all arranged at the same level. The plane at which the lance ends are arranged is preferably the lower end of the countercurrent combustion zone. It is also conceivable to arrange the combustion lances in several levels, so that a different temperature profile can be set in the combustion zone. The burner lances 10 are preferably connected to a fuel line 9 for conducting fuel to the burner lances 10 . The fuel line 9 is designed, for example, at least partially as a ring line, which extends circumferentially around the respective shaft 2b. The shaft 2b preferably has a fuel line 9 assigned to the burner lances 10 of the shaft 2b, which in particular has a control element for adjusting the fuel quantity to the burner lances 10. 1a to e shows an example of a lime kiln system 4 with a shaft kiln 1 with a shaft 2b with a round shaft cross-section. However, the shaft cross-section can have a different geometric contour, such as round, oval, square, semi-round or polygonal. The combustion zone 20 extends, for example, in a shaft section with an essentially constant cross section.

A cooling zone 22 , which extends to the material outlet 40 , adjoins the combustion zone 20 in the flow direction of the material in each shaft 2b. The cooling zone 22 is formed, for example, in a shaft section with a cross section that widens in the direction of the combustion zone. The cross section of the shaft section of the cooling zone 22 is, for example, at the border to the combustion zone 20 larger than the cross section of the lower area of the combustion zone 20, so that at the upper end of the cooling zone 22 and adjacent to the combustion zone 20 there is a material-free space 17, in particular an annular space forms, in which no material is arranged. The material-free annular space 17 is gas-connected to the duct 19, for example. The material is cooled within the cooling zone 22 to about 100°C by means of cooling gas flowing countercurrently to the material.

At the lower end of the cooling zone 22 an inner cylinder 26 is arranged, for example, which extends from the cooling zone 22 into the combustion zone 20 and optionally into the preheating zone 21 . The inner cylinder 26 has a cooling air inlet 27 at its lower end for introducing cooling air into the interior of the inner cylinder 26 . The inner cylinder is preferably arranged concentrically to the shaft 2b, so that there is preferably an annular cooling zone 22 and an annular combustion zone within the shaft 2b

train 20 Optionally, at least part of the preheating zone 21 is ring-shaped. The inner cylinder 26 preferably serves as a flow guide so that the material in the burning zone 20 and the cooling zone 22 and optionally in the preheating zone

21 is evenly distributed and flows through the gas stream. The inner cylinder 26 also has a cooling air outlet 28 for discharging the cooling air from the inner cylinder 26 at its upper end, preferably at the level of the preheating zone 21 or the upper end of the combustion zone 20 . A cooling air line 7 is preferably connected to the cooling air outlet 28 and is used for conducting the cooling air heated in the inner cylinder 26 . The cooling air line 7 preferably has at least one, for example two, control elements 45, 46 for adjusting the amount of cooling air flowing through the inner cylinder.

The cooling zone 22 preferably has a cooling gas extraction device 17 with a cooling gas outlet 29 in each case. In the exemplary embodiment in FIG. 1, the cooling gas extraction device 17 is designed as a material-free, in particular annular, space 17 . The cooling gas outlet 29 is preferably arranged in the shaft wall of the material-free space 17 at the upper end of the cooling zone 22 . The cooling gas flowing into the cooling zone 22 via the cooling gas inlet 23 preferably flows completely out of the cooling gas outlet 29 of the cooling gas extraction device 17 from the shaft 2b. The cooling gas extraction device 17 is preferably connected to a cooling gas extraction line 11 for conducting the cooling air extracted via the cooling gas extraction device 17 . In particular, the cooling air outlet 28 of the inner cylinder 26, in particular the cooling air line 7, is connected to the cooling gas discharge line 11, so that the cooling air flowing out of the shaft 2b through the inner cylinder 26 is preferably mixed with the cooling gas drawn off via the cooling gas discharge device 17.

A discharge device 41 is preferably arranged at the end of the shaft 2b on the material outlet side. The discharge device 41 comprises, for example, horizontal plates, preferably a discharge table, which allow the material to pass through laterally between the discharge table and the housing wall of the shaft furnace 1 . The discharge device 41 is preferably designed as a pusher or rotary table or as a table with a pusher scraper. This enables a uniform throughput rate of the material to be burned through shaft 2b. The discharge device 41 also includes, for example, the outlet funnel 25, which is connected to the discharge table and at the lower end of which the material outlet 40 is attached.

During operation of the shaft furnace 1, material such as limestone or dolomite is fed into the shaft 2b via the material inlet 3 and fuel is introduced into the shaft 2b via the burner lances 10. The material to be burned is preferably heated to a temperature of about 700° C. in the preheating zone 21 of the shaft 2b. During operation of the shaft furnace 1, the cooling gas flows through the cooling zone 22 in countercurrent to the material to be cooled and is preferably completely discharged from the shaft 2b via the cooling gas outlet 29, so that preferably no cooling gas flows from the cooling zone 22 into the combustion zone 20.

Within the shaft 2b, the combustion gas flows, for example, through the burner lances 10 or optionally through a combustion gas inlet, preferably into the combustion zone 20 of the shaft 2b and in particular in countercurrent to the material within the combustion zone 20. Below the burner lances 10, for example, a direct current combustion zone forms, which preferably extends to the end of the combustion zone 20 adjacent to the cooling zone 22 . Following the combustion zone 20, the gas flows into the preheating zone 21 and through the exhaust gas outlet 6 of the shaft 2b. Preferably, the exhaust gas discharged from the stack 2b has a temperature of 100°C to 400°C.

The exhaust gas is conducted into an exhaust gas line 39 which is connected to the exhaust gas outlet 6 . The exhaust gas line 39 optionally has an exhaust gas filter 31 for filtering fine particles, in particular dust, from the exhaust gas downstream of the exhaust gas outlet 6 in the flow direction of the exhaust gas.

At least part of the exhaust gas is preferably fed via the exhaust pipe 39 to the combustion zone 20 of the shaft 2b. For this purpose, the exhaust gas line 39 is connected to the burner lances 10 , for example, preferably via a ring line 8 . It is also conceivable that a gas inlet is arranged in the combustion zone 20, via which the exhaust gas is introduced into the combustion zone. The exhaust gas line 39 preferably has a heat exchanger 43 downstream of the exhaust gas filter 31 in the flow direction of the exhaust gas and optionally a heating device (not shown) for heating the exhaust gas. The off-gas line 39 is preferably connected to an oxidizing agent line 14 so that an oxidizing agent, preferably pure oxygen, is introduced into the off-gas line 39 and then together with the off-gas into the shaft 2b, in particular the combustion zone 20 of the shaft 2b. It is also conceivable that an oxygen-rich gas with an oxygen content of at least 70 to 95%, preferably 90% is introduced into the exhaust pipe 39. The oxidizing agent is preferably introduced into the exhaust pipe 39 upstream of the heat exchanger 43 . Optionally, the oxidizing agent line has a regulating element 47 for adjusting the quantity of oxidizing agent to be introduced into the exhaust gas line 39 . The exhaust pipe 39 has in particular a plurality of fans or compressors 35, 36 for accelerating the exhaust gas.

The heat exchanger 43 is connected in particular via a cooling gas discharge line 11 to the cooling gas outlets 29 of the shaft 2b, so that the exhaust gas in the heat exchanger 43 is heated by the cooling gas drawn off, preferably in counterflow. Following the heat exchanger 43, the cooling gas discharge line 11 optionally has a regulating element 48 for adjusting the quantity of cooling gas to be drawn off and a filter 16 for removing dust from the cooling gas. The exhaust gas is preferably heated to a temperature of approximately 400° C. to 800° C., in particular 600° C., in the heat exchanger 43 and/or the heating device. A gas analysis device 51, which is designed to determine the oxygen content and/or the CO 2 content in the exhaust gas, is connected downstream of the filter 16, for example. The gas analysis device is preferably connected to a control device which is designed in such a way that it controls the quantity of cooling gas discharged via the cooling gas outlet 29 as a function of the determined CO 2 content and/or oxygen content. For example, the amount of cooling gas is increased or decreased when the CO 2 content and/or the oxygen content deviates from a certain limit value or limit range.

The heating device is, for example, an electrically operated heating device. In particular, the heating device is operated using solar energy. It is also conceivable that the heating device comprises a heat exchanger, with the heating medium flowing in countercurrent being heated by solar energy. The heating device is preferably designed as a combustion reactor for the combustion of preferably renewable energy sources, such as wood, with the combustion preferably taking place in such a way that the combustion gas has a high CO 2 content of at least 90%. A portion of the exhaust gas is branched off upstream of the heat exchanger 43 and discharged via a cooling device 32 by means of a compressor 37 . The cooling device 32 is, for example, a heat exchanger, which is preferably operated with a coolant, such as water, in countercurrent.

The channel 19 preferably has a closure device 18 for sealing the channel 19 in a gas-tight manner, so that the shafts 2a and 2b are separated from one another in terms of gas technology. A gas flow through the channel 19 from one of the shafts 2a, b to the respective other shaft 2a, b is prevented by the closure device 18. The closure device 18 is, for example, a wall made of, in particular, refractory bricks. It is also conceivable that the duct 19 is at least partially or completely absent, in particular that it was removed when the PFR shaft kiln was converted into a lime kiln system 4 . The closure device is, for example, a steel sheet that extends completely over the diameter of the channel 19 and has a refractory lining, for example a brick lining, in particular on at least one or both sides. The steel sheet may be equipped with a cooling device driven by air, for example, as needed.

The shaft 2a on the left essentially corresponds to the shaft 2b, for example. In the embodiment of FIG. 1a, the left shaft 2a has not been converted and corresponds to the shaft of a PFR shaft furnace.

FIGS. 1b to 1e show sectional views of the lime kiln system 4 of FIG. 1a at the sectional planes marked in FIG. 1a.

When converting a PFR shaft kiln to a lime kiln system 4 with a shaft kiln 1 with exactly one shaft 2a or 2b, or to two parallel shaft kilns 1 each with exactly one shaft 2a, b, the channel 19, which is in the PFR Shaft furnace serves as a connecting channel for the gas connection of the shafts 2a, b and in particular connects the combustion zones 20 of the two shafts 2a, b to one another, closed by means of a closure device 18. 2a and b show a further exemplary embodiment of a lime kiln system 4, this largely corresponding to the lime kiln system of FIG. 1a. The same elements are provided with the same reference symbols. As an example, only the right-hand shaft 2b has been modified. In contrast to the shaft furnace 1 of FIG. 1a, the shaft furnace 1 of FIG. 2a does not have an inner cylinder 26, so that the shaft 2b has, for example, a rectangular or circular cross section and is not designed as an annular shaft. The cooling gas extraction device 17 of the shaft furnace 1 includes, for example, the channel 19 that is closed by means of the closing device 18 , the cooling gas outlet 29 being arranged at least partially or completely within the closed channel 19 .

The shaft cross-section of the cooling zone 22 widens, for example, in the direction of the channel 19, the cooling gas extraction device 17 being designed as a material-free space inside the channel 19 and around the cooling gas outlet 29.

The line of the cooling gas drawn off from the cooling zone 22 and the exhaust gas drawn off from the preheating zone 21 correspond to the circuit described with reference to FIG. 1 in the exemplary embodiment of FIGS. 2a, b.

FIGS. 2c to 2e show sectional views of the lime kiln system 4 of FIG. 2a at the sectional planes marked in FIG. 1a. The cross section of the shaft 2b is rectangular, for example, although a round cross section is also conceivable.

The lime produced with the above-described shaft furnace 1 of FIGS. 1 and 2 has a medium or low reactivity, while at the same time process gas with a CO 2 content of more than 90% based on dry gas is produced. Alternatively, lime with high reactivity can also be produced, with the mode of operation being set in such a way that a cocurrent combustion zone is formed under the combustion lances 10 and part of the kiln exhaust gas flows from the combustion zone into the cooling gas discharge line 11 . In the case of a process exhaust gas with a CQ2 content of more than 90% it is possible to provide this inexpensively for the production of methane or methanol or alternatively for sequestration. Alternatively, exhaust gas with a lower CO 2 content, for example 45% for soda production or 35% for sugar production or 30% for the production of precipitated calcium carbonate, can also be generated with the shaft furnace 1 described above.

reference list

1 shaft furnace

2a, b shaft

3 material inlet / sluice

4 Lime kiln system 6 Exhaust outlet

7 cooling air duct

8 ring line

9 fuel line

10 burner lances 11 cooling gas discharge line 14 oxidant line 16 filter

17 material-free space / cooling gas extraction device

18 locking device

19 channel

20 firing zone 21 preheating zone 22 cooling zone 23 cooling gas inlet

25 outlet funnel

26 inner cylinder

27 cooling air intake

28 Cooling air outlet 29 Cooling gas outlet

31 exhaust filter

32 cooling device

33 - 38 Compressor/Fan

39 exhaust pipe

40 material outlet

41 discharge device 43 heat exchanger

44 - 48 control organ

51 gas analysis device

Claims

patent claims

1. Lime kiln system (4) with at least one shaft kiln (1) for burning and cooling material such as carbonate rocks, the lime kiln system (4) having two shafts (2a, b) and a channel (19) extending between the two shafts ( 2a, b) extends, and wherein the shaft furnace (1) includes exactly one of the shafts (2a, b) and the shaft

(2a, b) a material inlet (3) for admitting material to be burned into the

shaft (2a, b) and in the flow direction of the material a preheating zone (21) for preheating the material, a firing zone (20) for firing the material, a cooling zone (22) for cooling the material and a material outlet (40) for discharging the material from the shaft (2a, b), characterized in that the duct (19) opens into the combustion zone (20) and/or the cooling zone (22) and the duct (19) has a closure device (18) for gas-technical closure of the Channel (19), so that a gas flow between the two shafts (2a, b) through the channel (19) by means of the closure device (18) is prevented.

2. Lime kiln system (4) according to claim 1, wherein the closure device (18) comprises a wall or a steel sheet.

3. Lime kiln system (4) according to any one of the preceding claims, wherein the shaft kiln (1) has an exhaust gas outlet (6) for discharging exhaust gas from the shaft (2a, b), and wherein the exhaust gas outlet (6) for recirculating the exhaust gas with the Combustion zone (20) of the respective shaft (2a, b) is connected.

4. Lime kiln system (4) according to any one of the preceding claims, wherein the chute (2a,b) has cooling gas discharge means (17) for discharging cooling gas from the chute (2a,b).

5. Lime kiln system (4) according to claim 4, wherein the cooling air extraction means (17) comprises a material-free space within the cooling zone (22).

6. Lime kiln system (4) according to claim 3, wherein a heat exchanger (43) for heating the exhaust gas is arranged between the exhaust gas outlet (6) and the combustion zone (20).

7. Lime kiln system (4) according to any one of the preceding claims, wherein the shaft (2a, b) is designed as an annular shaft and has a central displacement body which extends from the cooling zone into the combustion zone.

8. Lime kiln system (4) according to any one of the preceding claims, wherein a co-current burning zone (24) is formed within the burning zone (20).

9. Lime kiln system (4) according to one of the preceding claims, wherein the shaft kiln (1) has an oxidizing agent line (14) for conducting oxidizing agent, in particular oxygen-rich gas, into the combustion zone (20).

10. A method for converting a cocurrent countercurrent regenerative shaft kiln with two shafts (2a, b), which are gas-technically connected to one another via a duct (19), to form a lime kiln system (4) with at least one shaft kiln (1), each with exactly a shaft (2a, b), having at least the step:

- Gas-tight sealing of the channel (19) opening into the combustion zone (20) and/or the cooling zone (22) by means of a sealing device (18).

11. The method according to claim 10, wherein the closing of the channel (19) comprises laying a stone wall or inserting a steel sheet.

12. The method according to claim 10 or 11, wherein in at least one shaft (2a, b) a cooling gas extraction device (17) is provided and wherein the Cooling gas extraction device (17) has at least one material-free space and a cooling gas outlet (29) for letting out cooling gas from the respective shaft (2a, b).

13. The method according to any one of claims 10 to 12, wherein in at least one

Shaft (2a, b) an exhaust gas outlet (6) for the outlet of exhaust gas from the respective shaft (2a, b) is formed.

14. The method according to claim 13, wherein the exhaust gas outlet (6) of the shaft (2a, b) is gas-connected to the combustion zone (20) of the respective shaft (2a, b).

15. The method according to claim 14, wherein the exhaust gas outlet (6) in the direction of flow of the exhaust gas is connected to a heat exchanger (43) before the combustion zone (20).

16. The method according to claim 12 and 15, wherein the cooling gas outlet (29) of the cooling gas extraction device (17) is gas-technically connected to the heat exchanger (43), so that the cooling gas can flow through the heat exchanger (43) to heat the exhaust gas and in countercurrent to it .