Method and apparatus for using partially decarbonised material in clinker production as a sorbent for carbon dioxide separation

Abstract

The present invention relates to an apparatus for manufacturing cement, wherein the apparatus comprises a main preheater (10), a main calciner (20), and a kiln (30), wherein the main preheater (10) is connected to the main calciner (20) for conveying the raw meal, wherein the main calciner (20) and the kiln (30) are connected for conveying the raw meal, characterised in that a carbonation device (50) is arranged between the main calciner (20) and the kiln (30), wherein the main calciner (20) and the carbonation device (50) are connected for conveying partially decarbonised intermediate material (70), and wherein the carbonation device (50) and the kiln (30) are connected for conveying the partially decarbonised intermediate material (70).

Description

[0001] Method and apparatus for the use of partially decarbonized material in clinker production as a sorbent for carbon dioxide separation

[0002] The invention relates to a method for utilizing intermediate products generated within the clinker process, which are already largely decarbonated, to capture carbon dioxide from exhaust gas streams and, in particular, from the air. By returning the recarbonated material in this way to the clinker process, this additionally captured carbon dioxide, together with the large quantities of carbon dioxide generated in the clinker process, can be separated and reused in a climate-neutral manner, for example, by final disposal.

[0003] Direct air capture, or the separation of carbon dioxide, is comparatively complex and expensive, currently estimated at well over €300 per ton of CO2. However, it is considered a necessity to decarbonize CO2 from non-point sources such as road traffic or low-power heating systems. Nevertheless, the costs will remain far above the price of carbon dioxide certificates for the foreseeable future, making it financially unfeasible.

[0004] The cement industry is one of the largest sources of carbon dioxide, as carbon dioxide is released from the raw material, limestone. Technologies for carbon dioxide capture, such as oxyfuel technology, are being developed specifically for the cement industry. Therefore, the installation of such technologies at cement plants is expected relatively soon. The first projects are already underway.

[0005] From WO 2019 / 211 196 A1, an oxyfuel clinker production without recirculation of the preheater exhaust gases is known.

[0006] From WO 2023 / 002430 A1, an order for the reduction of CO2 emissions in clinker production plants is known.

[0007] An improved method for producing cement clinker and a corresponding apparatus are known from IT MI20 120 383 A1. A carbon dioxide capture process from a cement manufacturing process is known from US 2010 / 319586 A1.

[0008] From US patent 2012 / 141354 A1, a method and apparatus for the recovery of CCh gas in cement manufacturing plants and a method for the production of cement are known.

[0009] This therefore offers the possibility of modifying the carbon dioxide separation and storage technology used in the cement industry so that other gases, and especially the air itself, can also be depleted of carbon dioxide in a much simpler form.

[0010] The object of the invention is to provide a method for introducing carbon dioxide from an external source, in particular from the ambient air, into the cement process.

[0011] This problem is solved by the device with the features specified in claim 1 and by the method with the features specified in claim 7. Advantageous embodiments are described in the dependent claims, the following description, and the drawings.

[0012] The apparatus according to the invention is used for the production of cement. The apparatus comprises a main preheater, a main calciner, and a kiln. The raw meal is passed through the main preheater, the main calciner, and the kiln, where it is progressively heated and thereby converted into clinker. These components are connected to each other for the transfer of the raw meal. There are two variants for the gas-carrying connection of the components. The first variant directs the gas flow from the kiln through the main calciner into the preheater, i.e., in counterflow to the raw meal. This corresponds to the conventional setup. The second variant provides for the main calciner to be installed next to an existing system consisting of a main preheater and a kiln (usually with a previously used secondary calciner, which can be used or simply bypassed).In this case, the gas is routed from the furnace to the main preheater, while the main calciner has its own gas system and is operated, for example, and in particular, according to the oxyfuel principle for simplified CO2 separation. The main preheater is connected to the main calciner for transferring the raw meal. The main calciner is connected to the furnace for transferring the raw meal.

[0013] According to the invention, a carbonation device is arranged between the main calcinator and the furnace. The main calcinator and the carbonation device are connected for transferring the partially deacidified intermediate material. The connection between the carbonation device and the furnace can be direct, i.e., without any intervening elements. This variant is preferred when the entire system, consisting of the furnace, main calcinator, and main preheater, is operated as a single unit and a CO2 separator is operated downstream of the main preheater. This allows the CO2 absorbed in the carbonation device to be released back into the furnace and from there directed to the CO2 separator.In an embodiment with a laterally separated main calciner, the connection between the carbonation unit and the furnace is indirect, for example, via the main preheater or the main calciner. If the main calciner has a secondary preheater downstream in the gas flow direction, the carbonation unit and furnace can be indirectly connected via the secondary preheater. In this configuration, the CO2 absorbed in the carbonation unit is released again in the main calciner and separated in the CO2 separator downstream of the main calciner. The additional carbonation unit thus enables the introduction of CO2 from an external source into a cement process and therefore the possibility of using an existing cement plant as a CO2 sink. The advantage is that the cement production process is linear. Limestone passes through the process and is converted into clinker.In contrast, in carbonate looping, the calcium material is circulated in a loop, which in turn results in a continuous reduction in particle size, thus consuming material. This problem is eliminated in the device according to the invention, unlike carbonate looping, due to its linear design.

[0014] In a further embodiment of the invention, a heat exchanger is arranged between the main calciner and the carbonation unit. The heat exchanger is designed to cool the partially deacidified intermediate material leaving the main calciner. This contradicts the previous design, in which the intermediate material is transferred to the furnace at the highest possible temperature, as the material is heated further there. However, the heat exchanger makes it possible to lower the temperature of the intermediate material to, for example, 600 to 650 °C, which is ideal for absorbing CO2 from the air. Therefore, the air before and after the carbonation unit can also pass through an air heat exchanger to be heated to this temperature range upon entering the air heat exchanger and to transfer this heat as much as possible to the newly entering air upon exiting.

[0015] In a further embodiment of the invention, the heat exchanger is an oxygen preheater or connected in series with an oxygen preheater. Preferably, the device includes an oxygen source to operate the main calciner or the entire device according to the oxyfuel process. The oxygen from the oxygen source is then preheated in the heat exchanger or the oxygen preheater so that it can be supplied to the combustion process. In this way, the heat that is lost can be used effectively to bring the intermediate material to a temperature particularly suitable for recarbonation. Preferably, the heat exchanger or the oxygen preheater is connected to the main calciner to transfer the preheated oxygen.

[0016] In a further embodiment of the invention, a humidifier is arranged between the main calciner and the carbonation unit. Calcium oxide is thereby converted, at least partially, to calcium hydroxide, which, as a basic material, exhibits better binding properties for CO2. In a further embodiment of the invention, a dryer is arranged between the carbonation unit and the furnace. To improve recarbonation, humidification of the intermediate material is advantageous. This can preferably take place in the carbonation unit, but also upstream of the carbonation unit in a humidification unit. Drying removes this water, since, due to its high heat capacity, the water can influence the firing process in the furnace.

[0017] In another embodiment of the invention, the carbonation device and the furnace are connected via the main preheater for transferring the partially deacidified intermediate material. The advantage of this embodiment is that the recycled material can be returned to the process at the same temperature level. The disadvantage is that only a small portion of the material can be recarbonated in order to maintain the linear nature of the process.

[0018] In a further embodiment of the invention, the carbonation device has an air supply. This means that the supply of ambient air with an approximate CO2 concentration of 400 ppm is used directly for direct air capture. This enables a direct reduction of CO2 in the atmosphere and can be implemented in a technically efficient manner, since the CO2 is incorporated into the already very CO2-intensive cement process.

[0019] In a further embodiment of the invention, the main calciner is connected to a CO2 separation unit via gas flow. The main calciner is preferably connected to the CO2 separation unit via the main preheater or via a secondary preheater. In a preferred further development, the main calciner is connected to the CO2 separation unit via the secondary preheater and is operated according to the oxyfuel process, so that the CO2 separation can be a very simple CO2 separation process for very high CO2 concentrations. Additionally, the main preheater is connected to a further CO2 separation unit, wherein the further CO2 separation unit is designed for lower concentrations, for example, 15 to 25 vol% CO2. For example, the further CO2 separation unit is an amine scrubber. The process according to the invention is used for the production of cement, in particular for the production of clinker, especially from limestone.Such plants are found practically everywhere and, since they are among the largest sources of carbon dioxide (CCH) emissions, will soon be equipped with appropriate carbon dioxide capture technology and transport infrastructure. This allows for the process to easily utilize existing plants or those under construction or conversion. Like the clinker process, the process comprises the steps of preheating the feedstock in a main preheater, calcining the feedstock in a main calciner to produce an intermediate material, and firing the intermediate material in a kiln. The material flow direction from the preheater via the calciner to the kiln is opposite to the gas flow direction from the kiln via the calciner to the preheater. The main preheater is preferably multi-stage, and particularly preferably designed as a co-current heat exchanger with downstream separation cyclones.The main calciner is preferably designed as a fluidized-flow calciner with a separation cyclone. Various configurations of these components are known to those skilled in the cement industry.

[0020] According to the invention, after calcination, at least a partial stream of the intermediate material, which has been partially deacidified in the calciner, is withdrawn from the process and recarbonated with a carbon dioxide-containing gas in a carbonation device to form a carbonate material. The carbonate material is then fed back in before firing, i.e., before the furnace. This process takes advantage of the fact that, after the calciner, the starting material is 70 to 95% deacidified, i.e., decarbonized, meaning that the majority of the carbonate has already been converted to a reactive oxide. This material, in particular, can be used very efficiently to bind carbon dioxide. The material can be fed back in before firing directly into the furnace or further upstream in the material stream, for example, into the main preheater.

[0021] The process according to the invention bears a certain technical resemblance to the carbonate looping process, in which calcium oxide or calcium carbonate is circulated to separate carbon dioxide from one gas stream and concentrate it in another. Since the material in the process according to the invention undergoes this recarbonation step only once, or possibly only a small fraction of it multiple times, the problem of continuously comminuting the sorbent and thus the need for material consumption are eliminated. This distinguishes the process according to the invention significantly from the carbonate looping process. The process remains designed for the production of cement and thus for a linear process that leads from limestone to clinker and then to cement. Furthermore, in contrast to the regular carbonate looping process, this process does not place such high demands on the starting material.While the regular carbonate looping process requires a calcium carbonate content in the limestone of over 95 wt.%, ideally over 98 wt.%, the process according to the invention uses compositions typical for the clinker process, which contain less than 90 wt.%, and often even less than 80 wt.%, calcium carbonate. This means that significantly more cost-effective resources can be used. Furthermore, the existing carbon dioxide separation infrastructure for the clinker process is utilized, regardless of its integration into the process. Additionally, the intermediate material, i.e., the partially deacidified feedstock, is also produced within a suitable temperature range, enabling various methods for binding carbon dioxide from a gas stream without additional energy input and thus without additional energy expenditure.If the intermediate material is too warm for wet washing, for example, the heat can be recovered and used, thus eliminating the need for an additional heating step for the intermediate material before absorption. This makes the process according to the invention particularly suitable for direct air capture, i.e., the separation of CO2 from air where the CO2 content is only around 400 ppm. This makes the process both economically viable and technically effective.

[0022] The resulting advantage is that carbon dioxide from another source, such as air or another process, is bound to the calcined material and thus introduced into the highly CO2-intensive cement process, allowing it to be easily captured along with the carbon dioxide originating from the cement process itself. This synergistically utilizes the carbon dioxide separation process already required for the CO2-sensitive cement process, meaning that neither a high investment nor a high energy demand is required compared to today's direct air capture methods.

[0023] In a further embodiment of the invention, the kiln and main preheater are operated in a main gas stream. The main calciner is operated in a calciner gas stream separate from the main gas stream of the kiln and main preheater. This is advantageous, for example, when an existing cement plant is equipped with a new oxyfuel calciner operating alongside the existing gas stream, based on the oxyfuel principle. In the calciner, a large proportion of the carbon dioxide bound in the limestone is released, and a similarly large proportion of the fuel is combusted. It is therefore relatively easy to reduce CO2 emissions by, for example, approximately 75% by separating only the CO2 emissions from the oxyfuel calciner.Oxyfuel technology is advantageous here because, by using the highest possible oxygen content, it is converted to carbon dioxide, which then does not need to be separated from nitrogen in a complex process, as is the case when using air as the oxidizing gas. At the same time, the material cooler and furnace do not require extensive retrofitting for oxyfuel technology, making this concept particularly advantageous for retrofitting existing systems. This also provides excellent opportunities to implement the process according to the invention in such a retrofitted system. The input material stream is fed at least partially from the main preheater to the main calciner.In such a retrofit arrangement, a portion of the flow can also be routed directly from the main preheater to the furnace through the existing, possibly no longer heated, old calciner, so that only a partial flow is directed to the main calciner. After being removed from the main calciner and before being fed into the furnace for firing, the intermediate material is recarbonated with a carbon dioxide-containing gas to form a carbonate material. The feed to the furnace can occur anywhere along the process chain before firing, i.e., not only directly in the furnace but also to the calciner or the preheater. The specific feed can be highly dependent on the type of recarbonation. In a further embodiment of the invention, the calciner gas flow supplied to the main calciner has an oxygen content of at least 50 vol.%, preferably 90 vol.%, and particularly preferably 99 vol.%, and is thus operated according to the oxyfuel process.This facilitates the separation of the carbon dioxide, as it no longer needs to be separated from nitrogen in a complex process. The calciner gas stream supplied to the main calciner has a carbon dioxide content of less than 30 vol%, preferably less than 5 vol%, and most preferably less than 0.1 vol%. The effect is that the warm feedstock coming from the main preheater enters a carbon dioxide-poor atmosphere, while the main preheater has a high CO2 content due to the gases originating from the furnace. This shift in equilibrium between the two atmospheres leads to spontaneous decarbonation, which can then be utilized.

[0024] In a further embodiment of the invention, the calcinator gas stream supplied to the main calcinator is preheated by the intermediate material removed from the main calcinator. This has two advantages. Firstly, the hot intermediate material is stimulated to further decarbonize by being introduced into an oxygen-rich and CO2-poor atmosphere. This increases the proportion of CO2 that can be separated via the main calcinator, since this CO2 is not released in the furnace and thus, in the case of CO2 separation, does not escape into the environment via the calcinator gas stream. Secondly, this achieves efficient preheating of the calcinator gas stream.

[0025] In a further embodiment of the invention, the intermediate material, slightly cooled by the heating of the calciner gas stream supplied to the main calciner, is fed to a further material cooler with a maximum solids temperature of less than 750 °C, and thus below a temperature at which carbon dioxide is released from the intermediate material. This allows the further material cooler to be designed simply, since no greenhouse gases are released at this stage. Further cooling of the intermediate product is advantageous if the carbon dioxide binding for recarbonation is to be carried out semi-dry or wet. In a further embodiment of the invention, at least a portion of the intermediate material removed from the main calciner is fed to the main preheater. This is particularly preferred if the intermediate material has been cooled down sufficiently, for example, for semi-dry or wet recarbonation.This is also preferred if the intermediate material is introduced at, for example, 600 °C in order to bind the carbon dioxide originating from the furnace and thus also to transfer some of the furnace exhaust gases into the calcinator gas stream, thereby optimizing carbon dioxide emission reduction.

[0026] In a further embodiment of the invention, a secondary calciner is arranged in the main gas stream between the furnace and the main preheater. This secondary calciner can, for example, be taken from existing equipment during a retrofit. The feed material stream from the main preheater is distributed proportionally between the main calciner and the secondary calciner. This is preferred when the recarbonated intermediate material is fed to the main preheater to avoid frequent material recycling. In a further development, the secondary calciner can also be unfired, i.e., not functionally operate as a calciner.

[0027] In a further embodiment of the invention, the starting material is heated to at least 750 °C in the main preheater. This allows the limestone to reach a temperature at which it can be converted to calcium oxide. However, due to the warm exhaust gases from the furnace, the correspondingly high carbon dioxide concentration in the main preheater shifts this reaction towards calcium carbonate. The starting material transferred from the main preheater is then transferred to an unheated section of the main calciner, specifically below a combustion unit, or to a calciner gas supply in the main calciner. Here, due to the significantly lower carbon dioxide concentration, an initial deacidification can occur even before the material reaches the main calciner, meaning carbon dioxide is released without the need for additional heat input, as the material remains in a low-carbon dioxide atmosphere at a sufficiently high temperature.In a further embodiment of the invention, the intermediate material removed from the main calciner is cooled at least partially in a material cooler. Further cooling of the intermediate product is advantageous, particularly if the carbon dioxide addition for recarbonation is to be carried out semi-dry or wet.

[0028] In a further embodiment of the invention, a secondary preheater is arranged in the calcinator gas stream upstream of and downstream of the main calciner, both in the direction of material flow. A preheater is arranged upstream of the secondary preheater in the direction of material flow. The preheater is operated with the exhaust gas stream from the material cooler. Since carbon dioxide is not produced in the gas stream from the material cooler to the preheater, either through combustion or material conversion, air can simply be used and then released directly back into the environment without generating carbon dioxide emissions. At the same time, in contrast to a corresponding gas stream in the oxyfuel process, the procedure is very simple, as the introduction of false air or a gas leak is of only minor significance.

[0029] In a further embodiment of the invention, a first partial stream of the intermediate material is transferred directly from the main calciner to the furnace. A second partial stream is fed into a carbonation unit. After carbonation, the second partial stream is fed directly or indirectly to the furnace. Indirect feeding can occur, for example, via the main preheater. Intermediate storage before feeding into the furnace is also possible. Intermediate storage in air, in particular, allows for the further absorption of carbon dioxide from the ambient air.

[0030] In a further embodiment of the invention, the second partial stream is cooled and humidified between the main calciner and the carbonation unit. This allows the recarbonation to be carried out semi-dry or wet, which is advantageous for certain applications. The second partial stream is dried after the carbonation unit and fed to the main preheater. In a further embodiment of the invention, direct air capture takes place in the carbonation unit, i.e., carbon dioxide from the air is bound to the intermediate material. By utilizing the infrastructure currently being developed in the cement industry for the separation and storage of carbon dioxide from the clinker process, carbon dioxide can thus be removed from the air with a high degree of synergy, which is significantly advantageous compared to a purely direct air capture device.This makes it possible to remove carbon dioxide from the atmosphere even at lower CO2 certificate prices, thus reducing the man-made greenhouse effect.

[0031] In a further embodiment of the invention, the CCh content of the intermediate material is less than 25 wt.%, preferably less than 15 wt.%, and most preferably less than 5 wt.%. With very pure limestone, this would be around 44 wt.%, meaning the intermediate material is significantly deacidified or decarbonized.

[0032] In a further embodiment of the invention, recarbonation is carried out at 300 to 700 °C, preferably at 600 to 650 °C. This temperature range is ideally suited for binding carbon dioxide, in particular from exhaust gases, for example, also from the exhaust gases of the furnace. At the same time, the intermediate material is only cooled slightly, so that subsequent firing in the furnace can take place directly.

[0033] In a further embodiment of the invention, the recarbonation is carried out in the main preheater. For this purpose, the main preheater has a residence time extension device in order to make the uptake of carbon dioxide more efficient and achieve a higher absorption rate by extending the reaction time.

[0034] In a further embodiment of the invention, the recarbonation is carried out with an exhaust gas with a CO2 concentration of less than 30 vol.%.

[0035] The method according to the invention is explained in more detail below with reference to an embodiment illustrated in the drawings. Fig. 1 first example

[0036] Fig. 2 second example

[0037] Fig. 3 third example Fig. 4 fourth example Fig. 5 fifth example Fig. 6 sixth example

[0038] For the sake of simplicity, identical parts are given the same reference symbols in the various examples.

[0039] Figure 1 shows a typical cement plant for clinker production on the right. Raw material 60 is fed into a main preheater 10, introduced into the main calciner 20, where it is largely decarbonized. The intermediate material 70 is then fired in the kiln 30, usually a rotary kiln. The finished product is subsequently cooled in the product cooler 40. In the opposite direction to this material flow, a gas stream is first fed to the product cooler 40, preheated there, and then fed to the kiln 30. The kiln typically has the highest temperature. From there, the gas stream is fed into the main calciner 20 and from there to the main preheater 10.

[0040] According to the invention, a partial stream of the intermediate product 70 is extracted after the main calciner 20 and transferred to the carbonation device 50 shown on the left. There, a CO2-containing gas 80, for example, and preferably, combustion exhaust gas or alternatively air for direct air capture, is supplied. This causes a portion of the carbon dioxide contained in the gas to bind to the calcined intermediate material, thus forming the carbonate material 90. The CO2-poor gas 81 leaving the carbonation device 50 is therefore depleted of carbon dioxide. The carbonate material 90 has a (slightly) higher carbonate content compared to the intermediate material 70. The aim here is not to achieve the most complete possible recarbonation or the most complete possible removal of CO2 from the CO2-containing gas 80, but rather to realize an easily achievable, rapid benefit in reducing emissions in the

[0041] Overall context of a cement plant.

[0042] Fig. 2 shows a second example in which an existing conventional cement plant (right) has been supplemented by a new main calciner 20, which operates according to the oxyfuel process. For this purpose, the main calciner has a supply of oxygen 102, preferably with a purity of more than 90 vol.%, particularly preferably more than 95 vol.%, and most preferably more than 99 vol.%. This gas is preheated in the oxygen preheater 100 and reacted with fuel to form CO2 in the main calciner 20. Simultaneously, approximately 80% of the CO2 bound in the limestone is also released here. This CO2 can then be fed via a secondary preheater 12 to a CO2 separation unit 110, for example, a liquefaction unit for transport or storage, for heat recovery. This CO2 is thus not released into the environment.The starting material 60, preheated in the main preheater 10, is transferred, at least partially, as preheated starting material 62 to the main calciner 20. The intermediate material 70, decarbonized in the main calciner 20, is used, at least partially, to preheat the oxygen 102 in the oxygen preheater 100. Subsequently, the intermediate material 70 is transferred to a carbonation unit 50 and brought into contact with a CO2-containing gas 80. The resulting carbonate material 90 is fed to the furnace 30.

[0043] The third example shown in Fig. 3 differs from the second example in that a heat exchanger 120 is arranged upstream of the carbonation device 50, in which heat is transferred to an air stream. The heated air stream is directed to a pre-heater 14, where it transfers at least a portion of its thermal energy to the starting material 60, which is thus slightly preheated before entering the secondary preheater 12. The cooled intermediate material 70 can then be reacted with the CO2-containing gas 80 in the carbonation device 50, either semi-dry or wet. Before the carbonate material 90 is transferred to the furnace 30, it passes through a dryer 130 to prevent the temperature in the furnace from dropping too low. The fourth example shown in Fig. 4 differs from the example shown in Fig. 2 in that the carbonation device 50 is arranged downstream of the CO2 separation unit 110.This allows the CCh slip through the CO2 separation 110 to be efficiently reduced, thus further lowering the residual CO2 emission.

[0044] The fifth example shown in Fig. 5 differs from the third example shown in Fig. 3 in that the heat exchanger 120 and the dryer 130 are omitted and the low-CCh gas 81 is used directly for the preheater 14.

[0045] The sixth example shown in Fig. 6 differs from the third example shown in Fig. 3 in that the dryer 130 is omitted and the carbonate material 90 is introduced into the main preheater 10.

[0046] Reference sign

[0047] 10 main preheaters

[0048] 12 auxiliary preheaters

[0049] 14 pre-heaters

[0050] 20 Main calcinator

[0051] 22 Secondary calciner

[0052] 30 oven

[0053] 40 product coolers

[0054] 50 Carbonation device

[0055] 60 source materials

[0056] 62 preheated starting material

[0057] 70 Intermediate material

[0058] 80 CO2-containing gas

[0059] 81 Low-CO2 gas

[0060] 90 Carbonate material

[0061] 100 oxygen preheaters

[0062] 102 Oxygen

[0063] 110 CO2 separation

[0064] 120 Heat exchangers 130 Dryers

Claims

Patent claims 1. Device for the production of cement, wherein the device comprises a main preheater (10), a main calciner (20), and a kiln (30), wherein the main preheater (10) is connected to the main calciner (20) for transferring the raw meal, wherein the main calciner (20) and the kiln (30) are connected for transferring the raw meal, characterized in that a carbonation device (50) is arranged between the main calciner (20) and the kiln (30), wherein the main calciner (20) and the carbonation device (50) are connected for transferring the partially deacidified intermediate material (70), wherein the carbonation device (50) and the kiln (30) are connected for transferring the partially deacidified intermediate material (70).

2. Device according to claim 1, characterized in that between the Main calcinator (20) and carbonation device (50) Heat exchanger (120) is arranged.

3. Device according to claim 2, characterized in that the heat exchanger (120) is an oxygen preheater (100) or is connected in series with an oxygen preheater (100).

4. Device according to one of the preceding claims, characterized in that the carbonation device (50) and the furnace (30) are connected via the main preheater (10) for transferring the partially deacidified intermediate material (70).

5. Device according to one of the preceding claims, characterized in that the carbonation device (50) has an air supply.

6. Device according to one of the preceding claims, characterized in that the main calcinator (20) is connected to a CO2 separation (110) via gas flow technology.

7. A process, wherein the process is used for the production of cement, comprising the steps of preheating the starting material (60) in a main preheater (10), calcining the starting material (60) in a main calciner (20) to form an intermediate material (70), and firing the intermediate material (70) in a kiln (30), characterized in that, after calcining, at least a partial stream of the intermediate material (70) partially deacidified in the calciner is withdrawn from the process and recarbonated with a carbon dioxide-containing gas in a carbonation device (50) to form a carbonate material (90), wherein the carbonate material (90) is returned to the kiln (30) before firing in the kiln (30).

8. Method according to claim 7, characterized in that the furnace (30) and The main preheater (10) is operated in a main gas stream, wherein the main calciner (20) is operated in a calciner gas stream separate from the main gas stream of the furnace (30) and main preheater (10), wherein the initial material stream from the main preheater (10) is fed at least partially to the main calciner (20), wherein the intermediate material (70) is recarbonated to a carbonate material (90) with a carbon dioxide-containing gas after being removed from the main calciner (20) and before being fed to the furnace (30) for firing, wherein the calciner gas stream supplied to the main calciner (20) has an oxygen content of at least 50 vol%, wherein the calciner gas stream supplied to the main calciner (20) has a carbon dioxide content of less than 30 vol%, and wherein the calciner gas stream supplied to the main calciner (20) is fed through the The intermediate material (70) taken from the main calcinator (20) is preheated, whereby the intermediate material (70) is supplied to a further material cooler with a temperature of less than 850 °C by the heating of the calcinator gas stream supplied to the main calcinator (20).

9. Method according to one of claims 7 to 8, characterized in that the intermediate material (70) taken from the main calcinator (20) is fed at least partially to the main preheater (10).

10. Method according to one of claims 7 to 9, characterized in that the intermediate material (70) taken from the main calcinator (20) is cooled at least partially in a heat exchanger (120).

11. Method according to claim 10, characterized in that a secondary preheater (12) is arranged in the calcinator gas stream upstream of and downstream of the main calcinator (20) in the material flow direction, wherein a preheater (14) is arranged upstream of the secondary preheater (12) in the material flow direction, wherein the preheater (14) is operated with the exhaust gas stream of the heat exchanger (120).

12. Method according to one of claims 7 to 11, characterized in that a first partial stream of the intermediate material (70) is transferred directly from the main calciner (20) to the furnace (30), wherein a second partial stream is fed into a carbonation device (50), wherein the second partial stream is fed directly or indirectly to the furnace (30) after carbonation.

13. Method according to claim 12, characterized in that the second partial stream is cooled and humidified between the main calcinator (20) and the carbonation device (50), wherein the second partial stream is dried after the carbonation device (50) and fed to the main preheater (10).

14. Method according to one of claims 12 to 13, characterized in that in the carbonation device (50) a Direct Air Capture takes place, i.e. a binding of carbon dioxide from the air to the intermediate material (70).

15. Method according to any one of claims 7 to 14, characterized in that the CO2 content of the intermediate material (70) is less than 25 wt.%, preferably less than 15 wt.%, most preferably less than 5 wt.%.

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