Furnace and method for calcining a carbonate-containing material

Abstract

The invention relates to a furnace for calcining a carbonate-containing material, such as limestone or dolomite, the furnace comprising: a calcining chamber; a heating device; a transport device; and a CO2 collection device. The furnace comprises a closable inlet for carbonate-containing material and a closable outlet for calcined material, the transport device is located at least partly in the interior of the calcining chamber, and the CO2 collection device makes it possible to collect the CO2 produced while the carbonate-containing material is calcined. The furnace allows even large amounts of carbonate-containing material to be reacted with low or no CO2 emissions.

Description

[0001]February 7, 2025 Kiln and method for calcining a carbonate-containing material The present invention relates to a kiln for calcining a carbonate-containing material, such as limestone or dolomite, a method for calcining a carbonate-containing material, and burnt lime and / or burnt dolomite obtainable by this method. The calcination of carbonate-containing materials, such as limestone or dolomite, generally takes place in vertically operating ring or shaft kilns or in rotary kilns at high temperatures between 900 °C and 1300 °C. To generate these temperatures, fossil fuels such as coal, natural gas, or oil, which emit CO2 when burned, are generally used. The decomposition of the carbonate-containing materials during the combustion process into the corresponding oxide and CO2, produces additional CO2.When the kiln is fired directly, the CO2 produced during calcination mixes with gaseous oxidation products, such as nitrogen oxides (NOx), sulfur oxides (SOx), dioxanes, and furans, which are formed during the combustion of the corresponding fuels. To reduce the greenhouse effect caused by CO2 emissions, it is therefore desirable to reduce CO2 emissions during the calcination of carbonate-containing materials. Various processes for calcining carbonate-containing materials, such as limestone or dolomite, are known from the prior art and lead to reduced CO2 emissions. DE 843524 C describes a process for burning lime with simultaneous production of high-purity CO2 in an electric furnace.The lime is burned in a gas-tight kiln under reduced pressure, allowing the burning process to take place at lower burning temperatures, thereby reducing energy consumption. The resulting CO2 is expelled to the outside through a connecting pipe connected to a vacuum pump. The disadvantage of this process is that it is a batch process and its scalability is limited, meaning continuous, high throughputs are not possible. DE 4431508 A1 describes a lime burning process and a device for carrying out the process. Raw rock is fed into a raw rock bunker via a conveyor system, where it is preheated to approximately 100°C. The preheated raw material is then fed into the vacuum furnace via a rotary valve, and the vacuum furnace is sealed vacuum-tight.The deacidification temperature is lowered by applying a vacuum, enabling a more environmentally friendly and energy-efficient lime burning process. The CO2 formed during deacidification can be collected. The burnt lime is then cooled in a cooling tank. The disadvantage of this process is that it is a batch process, meaning that continuously high throughputs are not possible. It is only possible to arrange several vacuum furnaces in a cross-flow process or a circular circulation process so that they are each continuously fed individually from the raw rock bunker. Disadvantages of the prior art furnaces and processes for calcining carbonate-containing materials such as limestone or dolomite are that the processes generate high CO2 emissions, that they involve high energy consumption and / or that they do not allow for continuous process control and / or high throughput.The object of the present invention is to provide a kiln for calcining a carbonate-containing material, such as limestone or dolomite, which at least partially overcomes one or more disadvantages of the prior art. BU / dp 220297WO February 7, 2025 The calcination should result in as few as possible or no CO2 emissions and little energy, in particular little specific energy with respect to the carbonate-containing material, should be consumed. In particular, little or no fossil raw materials should be consumed during calcination. The kiln should be suitable for calcining industrial quantities of carbonate-containing material and enable continuous process control with high throughput. At the same time, the CO2 produced during calcination of the carbonate-containing material should be captured in the purest form possible and, if possible, without complex purification steps.Furthermore, the furnace should ensure high quality, in particular high reactivity, of the calcined material. A further object of the present invention is to provide a process for calcining a carbonate-containing material. The process should generate as few as possible or no CO2 emissions and consume little energy, in particular little specific energy with respect to the carbonate-containing material. In particular, little or no fossil raw materials should be consumed during calcination. The process should be suitable for calcining industrial quantities of carbonate-containing material and enable continuous processing with high throughput. At the same time, the CO2 generated during calcination of the carbonate-containing material should be captured in the purest possible form and, if possible, without complex purification steps.Furthermore, the process is intended to produce calcined material of high quality, particularly high reactivity. All or some of these objects are achieved according to the invention by a kiln according to claim 1, a process according to claim 36, and burnt lime and / or burnt dolomite according to claim 45. Advantageous embodiments of the invention are specified in the dependent claims and are explained in detail below. BU / dp 220297WO 7.February 2025 The invention provides a kiln for calcining a carbonate-containing material, such as limestone or dolomite, comprising i) a calcination chamber, ii) a heating device, iii) a transport device, and iv) a CO2 collection device, wherein the kiln comprises a closable inlet for carbonate-containing material and a closable outlet for calcined material, wherein the transport device is located at least partially inside the calcination chamber, and wherein the CO2 collection device enables the collection of the CO2 produced during calcination of the carbonate-containing material. Surprisingly, the kiln according to the invention has only low energy consumption, in particular a low consumption of specific energy with respect to the carbonate-containing material.At the same time, the furnace according to the invention enables continuous process control at high throughput, making it ideally suited for industrial scale. Furthermore, very little or no CO2 is emitted during the calcination of carbonate-containing material in the furnace according to the invention. The CO2 generated during the calcination of the carbonate-containing material is captured in high purity. Furthermore, material calcined in the furnace surprisingly exhibits high quality and, in particular, high reactivity. Without wishing to be bound to any specific scientific theory, the low energy consumption and high quality of the calcined material appear to be due to a shift in the chemical equilibrium toward the products of the calcination process caused by the CO2 collection device.Because the CO2 collection device enables the capture of the CO2 produced during calcination of the carbonate-containing material, it is removed from the chemical equilibrium. The resulting shift in chemical equilibrium toward the product side with more gaseous components makes calcination faster and more complete, ensuring that the calcined material maintains a consistently high quality even at increased throughputs. This appears to be due to the fact that, unlike conventional firing processes, the reverse reaction with existing CO2 (BU / dp 220297WO February 7, 2025) is inhibited by the continuous CO2 removal. The CO2 produced during calcination in the sealable calcination chamber and captured in the CO2 collection device can be reused and / or stored.The design of the kiln according to the invention enables the CO2 formed during the calcination process to be captured almost entirely, preventing it from being emitted into the environment. This allows for a particularly environmentally friendly process. If the kiln is operated exclusively with renewable energies or CO2-neutral fuels such as hydrogen, CO2 emissions can be reduced to zero. Without being bound to a specific scientific theory, the high purity of the CO2 captured in the CO2 collection device according to the invention can be explained by the fact that only little dust is produced in the calcination chamber according to the invention and only small amounts of other gases such as oxygen or nitrogen are present. In particular, the extensive exclusion of air allows the proportion of nitrogen in the captured CO2 to be reduced to a minimum.Consequently, the kiln exhaust gas does not need to be separated from nitrogen, oxygen, water vapor, and dust by complex purification steps such as drying, amine scrubbing, and / or membrane filtration, which involve high energy and cost expenditure. At the same time, only small amounts of oxygen are required for the calcination process compared to kilns where calcination is primarily achieved by introducing pure oxygen, which in particular allows the running costs of the calcination process to be kept low. The collected CO2 can be used, for example, as cooling or heating gas. A CO2 collection device here refers in particular to a device capable of absorbing and storing CO2. In particular, the CO2 collection device should be capable of storing CO2 at an elevated pressure of more than 1 bar, preferably more than 10 bar, more preferably more than 30 bar, and particularly preferably more than 50 bar.In a further embodiment, the CO2 in the CO2 collection device is present in a form liquefied under pressure. BU / dp 220297WO February 7, 2025 The term "transport device" is understood to mean a device suitable for transporting carbonate-containing material and / or calcined material. The transport device, which is located at least partially inside the calcination chamber, is preferably arranged such that it can transport carbonate-containing material and / or calcined material in the calcination chamber. The transport device is particularly preferably arranged such that it can transport carbonate-containing material and calcined material in the calcination chamber. This enables continuous process control and high throughput, since, depending on the size of the furnace, constantly large quantities of carbonate-containing material can be calcined.The closable inlet, which is arranged so that carbonate-containing material can enter the calcination chamber, and the closable outlet, which is arranged so that calcined material can leave the calcination chamber, ensure continuous calcination of the carbonate-containing material. The closable inlet and outlet limit or prevent uncontrolled escape of CO2 from the furnace. At the same time, the closable inlet and outlet allow the targeted removal of CO2 from the calcination chamber into the CO2 collection device. As a result, very little or none of the CO2 produced during the calcination of the carbonate-containing material is emitted into the environment. The term "calcination" refers here in particular to the heating of materials containing calcium and magnesium carbonate with the aim of decomposing them.In particular, "calcination" here means the conversion, i.e., deacidification, of carbonate-containing material to the corresponding oxide and carbon dioxide. An example of this is the conversion of calcium carbonate to calcium oxide with the release of carbon dioxide at high temperatures. BU / dp 220297WO February 7, 2025 The term "carbonate-containing material" refers here and elsewhere in particular to all types of mineral carbonates and / or mixtures thereof. Carbonate-containing material can be, for example, limestone, dolomite, magnesite, carbonate ore, or mixtures thereof. The average particle size (d50) of the carbonate-containing material used can vary within wide ranges. The carbonate-containing material preferably has an average particle size of 0.5 mm to 100 mm, particularly preferably of 10 mm to 50 mm. If the carbonate-containing material has a larger average particle size, complete calcination of the carbonate-containing material may require longer treatment times. If, however, the carbonate-containing material is smaller than the preferred particle size, dust formation may occur. Methods for determining the particle size distribution are generally known to those skilled in the art.For example, the particle size distribution can be determined by sieve experiments or sieve analysis, in particular by sieve analysis using DIN 66165-1 and / or DIN 66165-2. Furthermore, the particle size distribution or grain sizes can be determined, for example, according to DIN EN 933-1, 933-2 and / or 933-10. The term "calcined material" here refers to the material that is produced during the calcination of the carbonate-containing material. If, for example, limestone (CaCO3) is used as the carbonate-containing material, the calcined material is predominantly calcium oxide (CaO). According to a further preferred embodiment of the furnace according to the invention, the calcination chamber is an elongated container. The longitudinal direction here is the direction of movement of the carbonate-containing or calcined material in the calcination chamber.Preferably, the closable inlet and the closable outlet are located at opposite ends along the longitudinal direction. Such a geometry ensures that the calcination of the carbonate-containing material is complete, so that as little uncalcined material as possible is present when leaving the calcination chamber. For example, the elongated container can be a tube, a rectangular container, or a container that is flat at the bottom and rounded at the top. Preferably, the calcination chamber is made of brick or cast concrete. A brick or cast concrete calcination chamber offers the advantage of lower investment costs compared to a steel calcination chamber. In another embodiment, the calcination chamber is made of steel.A steel calcination chamber can be operated virtually gas-tight without additional sealing, allowing the kiln to be used as a direct reduction kiln without major effort. Preferably, the elongated vessel has an internal cross-section of 1 m perpendicular to the longitudinal direction of the vessel. 2 up to 100 m 2 , especially from 2 m 2 up to 50 m 2 or from 5 m 2 up to 25 m 2Such an internal cross-section enables high throughput and calcination on an industrial scale. An internal cross-section that is too small leads to low throughput and thus to an uneconomical process. The elongated container preferably has a length of 5 m to 400 m, in particular of 10 m to 200 m or of 20 m to 100 m. This ensures the most complete calcination possible and a high quality of the calcined material. The plant size, i.e. the internal cross-section and the length of the elongated container, can be selected depending on the desired residence time and amount of carbonate-containing material. According to a further preferred embodiment of the furnace according to the invention, the calcination chamber has a heat-insulating and / or refractory coating on the inner wall.Since few / no mechanical or corrosive forces act on the coating, a variety of coating materials known from the prior art can be selected, taking into account temperature resistance, thermal conductivity, material price, and assembly effort. The coating is preferably made of ceramic, phyllosilicate, olivine, mullite, aluminum oxide, silicon dioxide, magnesium oxide, zirconium dioxide, yttrium oxide, zirconium silicate, carbon, firebrick, refractory concrete, or a mixture thereof. This ensures a long service life of the calcination chamber and the kiln. According to a further preferred embodiment of the kiln according to the invention, the calcination chamber has a heat-insulating and / or heat-resistant coating on the outer wall. This allows the kiln to be operated particularly energy-efficiently, since less energy escapes from the calcination chamber of the kiln in the form of heat.According to a further preferred embodiment of the furnace according to the invention, the closable inlet comprises at least one closure device, in particular at least one or more locks. The closure device preferably comprises at least two airtight knife gate valves. With such a closure device, calcination can take place in a continuous process while preventing uncontrolled escape of CO2 from the calcination chamber. At the same time, new carbonate-containing material can be introduced into the calcination chamber without having to interrupt the process. This enables high throughput on an industrial scale. According to a further preferred embodiment of the furnace according to the invention, the closable outlet has at least one discharge device. The discharge device preferably comprises a double pendulum flap, a knife gate valve, a rotary valve, and / or a screw conveyor.In particular, the discharge device comprises a double pendulum flap. Such a discharge device allows for good sealing of differential pressures between the calcination chamber and the outlet environment. In particular, the uncontrolled escape of CO2 from the calcination chamber can be prevented with such a closure device. This enables a continuous process in which calcined material can leave the calcination chamber without having to interrupt the BU / dp 220297WO February 7, 2025 process. Thus, a high throughput on an industrial scale is possible. According to a further preferred embodiment of the furnace according to the invention, the heating device of the furnace according to the invention is located within the calcination chamber. Preferably, the heating device is located above and / or below the transport device. This allows the carbonate-containing material to be heated / irradiated directly, and energy can be saved.At the same time, uniform and / or double-sided heating of the material can be enabled, whereby the efficiency of calcination and the quality of the product can be increased through complete calcination. According to a further preferred embodiment of the furnace according to the invention, the heating device is an indirect heating device. An indirect heating device is, in particular, a heating device in which a material with good thermal conductivity, such as metal or ceramic, is heated and the heat is radiated from this material onto the carbonate-containing material. There is thus a spatial separation between the heat source and the carbonate-containing material. With such a heating device, damage or malfunctions of the heat source due to direct contact with CO2 or dust from the carbonate-containing material can be prevented. The heating device is preferably a radiant heating device.This radiant heating device can be operated electrically or by other means, as long as no other gas or substances enter the calcination chamber. For example, it can be a gas-fired radiant heating device with a closed gas supply and exhaust system. For example, hydrogen and air can be fed separately into the heater via two lines, ignited there, and exhaust gases can leave the heater via a third line. The lines can be routed to the outside through the casing of the calcination chamber. The heating device is particularly preferably an electric radiant heating device. This allows CO2 emissions to be further reduced if electricity from renewable energy sources is used. Consequently, the consumption of fossil fuels in the operation of the kiln can be completely eliminated.According to a further preferred embodiment of the furnace according to the invention, the transport device comprises at least one conveyor belt and / or at least one vibrating chute and / or at least one flat wagon on rails. This enables uniform process control with a constant and high throughput. Flat wagons on rails are understood to mean refractory flat wagons. The calcined material can be removed from the flat wagon using a scraper or a tiltable table surface. In a preferred embodiment, the flat wagon has a table surface with a hinge on one side that can be opened by a lifting rail on the other side of the table surface, whereby the table surface assumes an inclined position that allows the calcined material to slide into a hopper. This allows for a particularly efficient process design.A vibrating trough is understood to be a trough that is subject to periodic oscillation and is arranged such that the carbonate-containing material and / or calcined material can be transported in the desired direction. In this way, constant mixing of the bed of carbonate-containing material and / or calcined material is enabled and the carbonate-containing material is heated evenly. According to a further preferred embodiment of the furnace according to the invention, the transport device comprises at least one conveyor belt. Preferably, the at least one conveyor belt is arranged such that the transport of the carbonate-containing material and / or the calcined material takes place horizontally. According to a further preferred embodiment, the at least one conveyor belt is a plate conveyor belt or a ceramic-coated belt conveyor.Preferably, the at least one conveyor belt is heat-resistant up to at least 1200°C. According to a further preferred embodiment of the furnace according to the invention, the at least one conveyor belt comprises a preheating device. This ensures that the carbonate-containing material is heated upon contact with the conveyor belt. As a result, the residence time of the carbonate-containing material in the calcination chamber can be shortened, yet complete calcination of the carbonate-containing material can be achieved. This allows for efficient process design, as an increased material throughput is enabled. According to a further preferred embodiment of the furnace according to the invention, the transport device comprises a plurality of conveyor belts, in particular a plurality of slightly rising conveyor belts. By arranging a plurality of slightly rising conveyor belts one behind the other, the carbonate and / or calcined material is dropped from a leading belt onto a following belt.This leads to better mixing of the material bed, as the material is subjected to mixing and repositioning due to the discharge. This allows the carbonate-containing material to be heated and calcined more evenly. Maintenance of the conveyor belts is also made easier. A slight incline is understood to mean an incline at an angle of less than 30° to the horizontal plane. According to a further preferred embodiment of the furnace according to the invention, the furnace comprises a height limiter arranged to limit the height of carbonate-containing material on the conveyor device. This enables the direct heating / irradiation of as much carbonate-containing material as possible at the same time. Furthermore, uniform calcination and thus a high and consistent quality of the calcined material are enabled. BU / dp 220297WO 7 is preferably used.February 2025 The height of the bed consisting of carbonate-containing material is limited to the average particle size (d50) of the carbonate-containing material used. This ensures that a single layer (monolayer) of the carbonate-containing material is produced, which guarantees particularly uniform heating of the carbonate-containing material. According to a further preferred embodiment of the furnace according to the invention, the furnace comprises a blackening device for blackening carbonate-containing material, in particular for blackening with iron oxide and / or soot. The blackening device applies a thin layer of a dark surface coating, in particular soot or iron oxide, to the surface of the carbonate-containing material. The blackening improves the IR absorption of the carbonate-containing material. Consequently, the carbonate-containing material absorbs heat more efficiently.This allows the reaction rate during calcination to be increased, thus enabling a higher process throughput. At the same time, less energy is required for heating due to the more effective IR absorption of the carbonate-containing material. According to a further preferred embodiment of the furnace according to the invention, the furnace comprises a first injection device for treating carbonate-containing material with steam and / or hydrogen. An injection device refers to a device suitable for introducing vapors and / or gases into the calcination chamber. During the treatment of the carbonate-containing material and / or the calcined material with vapors or gases, the surface of the material is gassed or vaporized. The injection of hydrogen leads to a direct reduction of the carbonate-containing material into the corresponding oxide.An example of direct reduction is the conversion of calcium carbonate to calcium oxide in the presence of hydrogen and heat. Direct reduction of the carbonate-containing material produces the gaseous products CO, CO2, and H2O. The first injection device for treating carbonate-containing material with steam and / or hydrogen allows the furnace to be operated as a direct reduction furnace using hydrogen. Direct reduction of the carbonate-containing material occurs at a lower temperature than calcination without hydrogen. This reduces heating energy consumption and reduces CO2 emissions. Treating the carbonate-containing material with steam increases the reaction rate during calcination, enabling a higher process throughput.According to a further preferred embodiment of the furnace according to the invention, the furnace comprises a second injection device for treating the calcined material with oxygen. By injecting oxygen, soot located on the surface of the calcined material is burned off to form CO2. Soot that is created in the calcination chamber or introduced by a blackening device can be removed in this way. This ensures high quality and reactivity of the calcined material. According to a further preferred embodiment of the furnace according to the invention, the furnace comprises a preheater arranged to enable the heating of carbonate-containing material before it enters the calcination chamber, in particular a shaft preheater arranged to enable the heating of carbonate-containing material before it enters the calcination chamber.By preheating carbonate-containing material before it enters the calcination chamber, the material's residence time in the calcination chamber can be reduced, enabling higher throughput. Preferably, the preheater is a heat exchanger, in particular a heat exchanger that uses heat from the CO2 produced during calcination of the carbonate-containing material to heat the carbonate-containing material. This results in a particularly efficient process design. Hot CO2 is produced during calcination of carbonate-containing material. With such a heat exchanger, the thermal energy of this hot carbon dioxide can be used to preheat new carbonate-containing material. This allows further energy and CO2 emissions to be saved. Preferably, the preheater is connected to the CO2 collection device, in particular, the preheater is connected to the CO2 collection device via a pipeline.The preheater reduces the temperature of the hot CO2 originating from the carbonate-containing material, allowing the CO2 to be more effectively compressed in the CO2 collection device. This allows for greater process efficiency compared to direct transfer of CO2 from the calcination chamber to the CO2 collection device. Preferably, the CO2 flows upwards from the calcination chamber through the preheater into the CO2 collection device, with the CO2 stream being driven by its continuous formation in the calcination chamber and / or by a fan installed upstream of the CO2 collection device. A fan is understood to be an externally driven turbomachine, which can also be a compressor. Using a fan can accelerate the heat exchange between the preheater and the calcination chamber, thus saving energy and reducing CO2 emissions.In particular, the fan is adjusted so that CO2 generated in the calcination chamber is driven by the preheater into the CO2 collection device and does not flow toward the closable outlet of the calcination chamber. This prevents CO2 from escaping from the closable outlet. According to a further preferred embodiment of the furnace according to the invention, CO2 is continuously removed from the calcination chamber and transferred to the CO2 collection device. By continuously removing CO2 from the calcination chamber, the chemical equilibrium between the carbonate-containing material and the calcined material is shifted to the product side, and a back reaction of the calcined material with CO2 is inhibited. The calcination proceeds more completely. This allows for higher product quality. BU / dp 220297WO 7.February 2025 According to a further preferred embodiment of the furnace according to the invention, the furnace comprises a CO2 separation system, in particular a CO2 separation system, which is installed between the CO2 collection device and the blower connected via a direct pipeline. The CO2 separation system allows CO, which is produced during calcination or direct reduction of the carbonate-containing material, to be separated from CO2 and water. The pure CO can be used in the chemical industry, in particular as a component of synthesis gas. According to a further preferred embodiment of the furnace according to the invention, the furnace comprises a cooler arranged to enable the cooling of calcined material after it has passed through the closable outlet, in particular a shaft cooler arranged to enable the cooling of calcined material after it has passed through the closable outlet.Preferably, the cooler is connected to a heat exchanger that uses the heat released during the cooling of calcined material in the cooler. This allows the thermal energy released by the calcined material during cooling to be used to preheat or dry carbonate-containing material. This saves energy and further reduces CO2 emissions. Preferably, the preheater and / or the cooler are counterflow heat exchangers. More preferably, both the preheater and the cooler are counterflow heat exchangers. More preferably, the cooler is arranged so that air can flow from bottom to top through the calcined material in the cooler, can be fed to a heat exchanger after passing through the cooler, and can be fed back into the cooler from bottom to top, creating an air cycle.This process control is particularly advantageous when working with a closed system using a cooling medium other than air, such as CO2. This can increase the efficiency of the heat exchange and further BU / dp 220297WO February 7, 2025 energy can be saved. Alternatively, the outside air can be used as the cooling medium. According to a further embodiment of the furnace according to the invention, the air circulation is driven by a fan. This can accelerate the heat exchange between the cooler and the heat exchanger, whereby the material can be cooled more quickly. More preferably, the heat exchanger is protected by at least one filter system. Such a filter system increases the service life and durability of the heat exchanger and the furnace.According to a further embodiment of the furnace according to the invention, the preheater and the cooler are connected by a pipeline arranged to allow the transport of hot gas from the cooler to the preheater, in particular through a well-insulated, substantially gas-tight or a well-insulated, gas-tight pipeline. As a result, the thermal energy released by the calcined material during cooling can be used to preheat carbonate-containing material. Thus, energy can be saved and CO2 emissions can be further reduced. According to a further preferred embodiment of the furnace according to the invention, the furnace comprises a feeding device for feeding carbonate-containing material into the calcination chamber, in particular a vibratory feeding device.Such a feeding device enables uniform feeding of the calcination chamber, so that calcination can take place continuously, evenly, and with a consistently high throughput. According to a further preferred embodiment of the kiln according to the invention, the kiln comprises a first silo for storing carbonate-containing material. Such a silo ensures a constant supply of carbonate-containing material and thus long-term, continuous operation of the kiln without constant personnel expenditure. BU / dp 220297WO February 7, 2025 According to a further preferred embodiment of the kiln according to the invention, the kiln comprises a second silo for storing calcined material. Such a silo enables a constant removal of calcined material from the calcination chamber, and thus long-term, continuous operation of the kiln without constant personnel expenditure.The invention further provides a process for calcining a carbonate-containing material, such as limestone or dolomite, comprising at least the steps of: a) providing a carbonate-containing material, b) introducing the carbonate-containing material into a furnace according to the invention, c) feeding the carbonate-containing material into the calcination chamber, d) calcining the carbonate-containing material in the calcination chamber, e) removing the calcined material from the furnace. The process steps are preferably carried out in the order specified above. The above statements regarding the furnace according to the invention apply analogously to the furnace, the calcination chamber, the carbonate-containing material, and the calcined material. Surprisingly, it has been found that such a process consumes particularly little energy, in particular little specific energy with respect to the carbonate-containing material.The process according to the invention can be used to calcine industrial quantities of carbonate-containing material in a continuous, high-throughput process. Furthermore, such a process results in low or no CO2 emissions. Furthermore, the CO2 produced during the calcination of the carbonate-containing material can be captured in high purity. Finally, it has been surprisingly found that calcined material produced using the process according to the invention is of high quality, in particular highly reactive. BU / dp 220297WO February 7, 2025. Calcination in process step d) of the process according to the invention preferably takes place at a temperature of 800°C to 1400°C, in particular of 800°C to 1300°C or of 900°C to 1200°C.According to a further preferred embodiment of the process according to the invention, the process comprises, before process step c), the step of preheating the carbonate-containing material to a temperature of 400°C to 900°C, in particular of 500°C to 800°C. By preheating carbonate-containing material to this temperature before feeding it into the calcination chamber, the residence time of the material in the calcination chamber can be reduced, thus enabling a higher throughput. Preheating preferably takes place at atmospheric pressure. Preheating preferably takes place in a preheater. The above statements regarding the preheater of the furnace according to the invention preferably apply analogously to the preheater.According to a further preferred embodiment of the process according to the invention, the process comprises, between process steps d) and e), the step of cooling the calcined material to a temperature of 10°C to 300°C, in particular from 20°C to 200°C or from 50°C to 100°C. Cooling preferably takes place at atmospheric pressure. Cooling preferably takes place in a cooler. What has been said above regarding the cooler of the furnace according to the invention preferably applies analogously to the cooler. According to a further preferred embodiment of the process according to the invention, the process comprises, before process step c), the step of blackening the carbonate-containing material. The blackening of the carbonate-containing material is preferably carried out with soot or iron oxide and / or with solutions of soot or iron oxide. By blackening the carbonate-containing material, it can better absorb thermal radiation BU / dp 220297WO February 7, 2025.As a result, calcination can be carried out more quickly and completely, while also consuming less energy. A higher throughput of high-quality calcined material can thus be achieved. Preferably, blackening takes place in a blackening device. The above statements regarding the blackening device of the furnace according to the invention preferably apply analogously to the blackening device. According to a further preferred embodiment of the process according to the invention, the carbonate-containing material is treated with steam and / or hydrogen during process step d). The treatment with hydrogen enables direct reduction of the carbonate-containing material into the corresponding oxide. The furnace can be operated as a direct reduction furnace. The direct reduction of the carbonate-containing material proceeds at a lower temperature than calcination without hydrogen.This means less energy is used for heating and CO2 emissions can be saved. By treating the carbonate-containing material with steam, the reaction rate during calcination can be increased, so that a higher throughput of the process is possible. The carbonate-containing material is preferably treated using an injection device. The above statements regarding the first injection device of the furnace according to the invention preferably apply analogously to the injection device. According to a further preferred embodiment of the process according to the invention, the carbonate-containing material is treated with oxygen between process steps d) and e). Soot that is produced in the calcination chamber or introduced by a blackening device can be removed in this way. This ensures a high quality and reactivity of the calcined material.What was said in connection with the process according to the invention for the kiln also applies to the kiln according to the invention. BU / dp 220297WO February 7, 2025 Finally, the invention also relates to burnt lime and / or burnt dolomite obtainable by the process according to the invention. Surprisingly, it has been found that burnt lime and / or burnt dolomite produced by the process according to the invention exhibits particularly high quality and reactivity. This appears to be due to the complete calcination of the material. Without wishing to be bound to a specific scientific theory, this appears to be attributable to the fact that, unlike in conventional firing processes, the CO2 produced is collected and thus removed from the chemical equilibrium, thereby inhibiting the reverse reaction to carbonate. The same applies to hydrates produced from the burnt lime and / or burnt dolomite according to the invention.The invention is explained in more detail below with reference to a drawing which does not limit the subject matter of the invention but merely represents a preferred embodiment. Fig. 1A shows a schematic representation of the upper part of a possible furnace according to the invention, as can also be used in the process according to the invention. Fig. 1B is a continuation of Fig. 1A and shows a schematic representation of the lower part of a possible furnace according to the invention, as can also be used in the process according to the invention. Carbonate-containing material 1 is converted into calcined material 2 in the furnace. Calcination takes place in the calcination chamber 3. The calcination chamber 3 is preferably an elongated container. The heating device 4 heats the carbonate-containing material 1 so that it is converted into calcined material 2.The heating device 4 is preferably a radiant heating device, in particular an electric radiant heating device. BU / dp 220297WO February 7, 2025 The CO2 collection device 6, which is connected to the calcination chamber 3 via a preheater 16, collects the CO2 produced during the calcination of the carbonate-containing material. The CO2 produced in the calcination chamber 3 is driven from the calcination chamber into the CO2 collection device 6, firstly by its continuous formation in the calcination chamber, which can create a slight overpressure in the calcination chamber 3, and secondly by a fan 14, which is located between the CO2 collection device 6 and the cooler 13 and can generate a slight negative pressure. The transport device 5 comprises a conveyor belt 5.1 and transports carbonate-containing material 1 and calcined material 2 through the calcination chamber 3. The conveyor belt 5.1 is preheated by a preheating device 23.Carbonate-containing material 1 enters the calcination chamber 3 via the closable inlet 7. Calcined material 2 leaves the calcination chamber 3 via the closable outlet 8. The closable inlet 7 has a closure device comprising at least one lock 9 and airtight knife gate valves 9.1. The closable outlet 8 has at least one discharge device 17. Preferably, the discharge device 17 is a double pendulum flap. The closable inlet 7 and the closable outlet 8 prevent the uncontrolled escape of CO2 from the calcination chamber 3. The blackening device 10 blackens the carbonate-containing material 1. Blackening is preferably carried out with soot. A first injection device 11 treats the carbonate-containing material 1 with hydrogen. A second injection device 15 treats the calcined material 2 with oxygen.The height limiter 12 is arranged such that it limits the height of carbonate-containing material 1 on the conveyor belt 5.1. BU / dp 220297WO February 7, 2025 In the preheater 13, carbonate-containing material 1 is preheated before entering the calcination chamber 3. The preheater 13 is preferably a shaft preheater. In the cooler 16, calcined material 2 is cooled after leaving the calcination chamber 3 and the closable outlet 8. The cooler 16 is preferably a shaft cooler. In the cooler 16, cold air is passed from bottom to top through the calcined material 2. The hot air is passed through a filter 20 into a heat exchanger 18. After passing through the heat exchanger 18, the cooled air is fed back to the cooler 16. The air circulation is driven by a fan 14 located downstream of the heat exchanger 18. Carbonate-containing material 1 is fed to the preheater 13 via the feeding device 19.In the first silo 21, carbonate-containing material 1 is stored before calcination. In the second silo 22, calcined material 2 is stored after calcination. BU / dp 220297WO February 7, 2025 List of reference symbols 1 Carbonate-containing material 2 Calcined material 3 Calcining chamber 4 Heating device 5 Transport device 5.1 Conveyor belt 6 CO2 collection device 7 Closable inlet 8 Closable outlet 9 Lock 9.1 Airtight knife gate valve 10 Blackening device 11 First injection device 12 Height limiter 13 Preheater 14 Blower 15 Second injection device 16 Cooler 17 Discharge device 18 Heat exchanger 19 Feeding device 20 Filter 21 First silo 22 Second silo 23 Preheating device BU / dp 220297WO February 7, 2025.

Claims

February 7, 2025 Patent Claims 1. A furnace for calcining a carbonate-containing material (1), such as limestone or dolomite, comprising: i) a calcination chamber (3), ii) a heating device (4), iii) a transport device (5), iv) a CO2 collection device (6), wherein the furnace comprises a closable inlet (7) for carbonate-containing material (1) and a closable outlet (8) for calcined material (2), wherein the transport device (5) is located at least partially inside the calcination chamber (3) and wherein the CO2 collection device (6) enables the collection of the CO2 produced during the calcination of the carbonate-containing material (1).

2. A furnace according to claim 1, characterized in that the calcination chamber (3) is an elongated container.

3. Oven according to claim 2, characterized in that the elongated container (3) has an internal cross-section of 1 m perpendicular to the longitudinal direction of the elongated container (3). 2 up to 100 m 2, especially from 2 m 2 up to 50 m 2 or from 5 m 2 up to 25 m 2 4. Furnace according to claim 2 or 3, characterized in that the elongated container (3) has a length of 5 m to 400 m, in particular of 10 m to 200 m or of 20 m to 100 m. - 2 - 5. Furnace according to one of the preceding claims, characterized in that the calcination chamber (3) has a heat-insulating and / or refractory coating on the inner wall, in particular a coating made of ceramic, phyllosilicate, olivine, mullite, aluminum oxide, silicon dioxide, magnesium oxide, zirconium dioxide, yttrium oxide, zirconium silicate, carbon, firebrick, refractory concrete, or a mixture thereof.

6. Furnace according to one of the preceding claims, characterized in that the closable inlet (7) comprises at least one closure device, in particular at least one or more locks (9).

7. Furnace according to claim 6, characterized in that the closure device comprises at least two airtight slide valves (9.1).

8. Furnace according to one of the preceding claims, characterized in that the closable outlet (8) comprises at least one discharge device (17). 9.Kiln according to claim 8, characterized in that the discharge device (17) comprises a double-pendulum flap, a plate slide, a rotary valve, and / or a screw, in particular a double-pendulum flap.

10. Kiln according to one of the preceding claims, characterized in that the heating device (4) is located within the calcination chamber (3).

11. Kiln according to claim 10, characterized in that the heating device (4) is located above and / or below the transport device (5).

12. Kiln according to claims 1 to 9, characterized in that the heating device (4) is an indirect heating device. BU / dp 220297WO February 7, 2025. - 3 - 13. Oven according to one of the preceding claims, characterized in that the heating device (4) is a radiant heating device, in particular an electric radiant heating device.

14. Oven according to one of the preceding claims, characterized in that the transport device (5) comprises at least one conveyor belt (5.1) and / or at least one vibrating chute and / or at least one flat car on rails.

15. Oven according to claim 14, characterized in that the at least one conveyor belt (5.1) is a plate conveyor or a ceramic-coated belt conveyor.

16. Oven according to claim 14 or 15, characterized in that the at least one conveyor belt (5.1) is heat-resistant up to at least 1200°C.

17. Oven according to claims 14 to 16, characterized in that the at least one conveyor belt (5.1) comprises a preheating device (23). 18.Furnace according to claims 15 to 17, characterized in that the transport device (5) comprises a plurality of conveyor belts (5.1), in particular a plurality of slightly rising conveyor belts.

19. Furnace according to one of the preceding claims, characterized in that the furnace comprises a height limiter (12) arranged such that the height of carbonate-containing material (1) on the transport device (5) is limited.

20. Furnace according to one of the preceding claims, characterized in that the furnace comprises a blackening device (10) for blackening carbonate-containing material (1), in particular for blackening with iron oxide and / or soot. BU / dp 220297WO February 7, 2025. - 4 - 21. Furnace according to one of the preceding claims, characterized in that the furnace comprises a first injection device (11) for treating carbonate-containing material (1) with steam and / or hydrogen.

22. Furnace according to one of the preceding claims, characterized in that the furnace comprises a second injection device (15) for treating the calcined material (2) with oxygen.

23. Furnace according to one of the preceding claims, characterized in that the furnace comprises a preheater (13) arranged to enable the heating of carbonate-containing material (1) before entering the calcination chamber (3), in particular a shaft preheater (13) arranged to enable the heating of carbonate-containing material (1) before entering the calcination chamber (3). 24.Kiln according to claim 23, characterized in that the preheater (13) is a heat exchanger, in particular a heat exchanger that uses heat from the CO2 produced during calcination of the carbonate-containing material (1) to heat carbonate-containing material (1).

25. Kiln according to claim 23 or 24, characterized in that the preheater (13) is connected to the CO2 collection device (6), in particular that the preheater (13) is connected to the CO2 collection device (6) via a pipeline.

26. Kiln according to claims 23 to 25, characterized in that the CO2 flows from the calcination chamber (3) upwards through the preheater (13) to the CO2 collection device, wherein the CO2 flow is driven by the continuous generation on the transport device (5) and / or by a blower (14) mounted upstream of the CO2 collection device (6). BU / dp 220297WO February 7, 2025. - 5 - 27. Furnace according to one of the preceding claims, characterized in that the furnace has a CO2 separation system, in particular a CO2 separation system installed between the CO2 collection device (6) and the blower connected via a direct pipeline.

28. Furnace according to one of the preceding claims, characterized in that the furnace comprises a cooler (16) arranged to allow the cooling of calcined material (2) after passing through the closable outlet (8), in particular a shaft cooler (16) arranged to allow the cooling of calcined material (2) after passing through the closable outlet (8).

29. Furnace according to claim 28, characterized in that the cooler (16) is connected to a heat exchanger (18) which uses the heat released in the cooler (16) during the cooling of calcined material (2). 30.Furnace according to claim 28 or 29, characterized in that the cooler (16) is arranged such that air can flow from bottom to top through the calcined material (2) located in the cooler (16), can be fed to a heat exchanger (18) after passing through the cooler (16), and can be introduced again from below into the cooler (16), thereby creating an air circuit.

31. Furnace according to claim 30, characterized in that the air circuit is driven by a fan (14).

32. Furnace according to claims 29 to 31, characterized in that the heat exchanger (18) is protected by at least one filter system (20). BU / dp 220297WO February 7, 2025. - 6 - 33. Kiln according to one of the preceding claims, characterized in that the kiln comprises a feeding device (19) for feeding carbonate-containing material (1) into the calcination chamber (3), in particular a vibratory feeding device (19).

34. Kiln according to one of the preceding claims, characterized in that the kiln comprises a first silo (21) for storing carbonate-containing material (1).

35. Kiln according to one of the preceding claims, characterized in that the kiln comprises a second silo (22) for storing calcined material (2).

36. A method for calcining a carbonate-containing material (1), such as limestone or dolomite, comprising at least the steps: a. providing a carbonate-containing material (1), b. introducing the carbonate-containing material (1) into a kiln according to one of claims 1 to 33, c. feeding the carbonate-containing material (1) into the calcination chamber (3), d.Calcining the carbonate-containing material (1) in the calcination chamber (3), e. Removing the calcined material (2) from the furnace.

37. The method according to claim 36, characterized in that the calcination in process step d) takes place at a temperature of 800°C to 1400°C, in particular from 800°C to 1300°C or from 900°C to 1200°C.

38. The method according to claim 36 or 37, characterized in that the method comprises the step of preheating the carbonate-containing material (1) to a temperature of 400°C to 900°C, in particular from 500°C to 800°C, before process step c). BU / dp 220297WO February 7, 2025. - 7 - 39. Process according to claim 38, characterized in that the preheating takes place in a preheater (13) as described in any one of claims 23 to 25.

40. Process according to any one of claims 36 to 39, characterized in that the process comprises, between process steps d) and e), the step of cooling the calcined material (2) to a temperature of 10°C to 300°C, in particular of 20°C to 200°C or of 50°C to 100°C.

41. Process according to claim 40, characterized in that the cooling takes place in a cooler (16) as described in any one of claims 28 to 32.

42. Method according to one of claims 36 to 41, characterized in that the method comprises the step of blackening the carbonate-containing material (1) before method step c), in particular that the blackening is carried out with a blackening device according to claim 20. 43.Process according to one of claims 36 to 42, characterized in that the carbonate-containing material (1) is treated with steam and / or hydrogen during process step d), in particular with a first injection device (11) according to claim 21.

44. Process according to one of claims 36 to 43, characterized in that the calcined material (2) is treated with oxygen between process steps d) and e), in particular with a second injection device (15) according to claim 22.

45. Burnt lime and / or burnt dolomite obtainable by a process according to one of claims 36 to 44. BU / dp 220297WO 7 February 2025.

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