Enhanced decarbonisation of a cement plant

Abstract

The present invention relates to a method for decarbonising a process for operating an apparatus for thermally treating a mineral material, wherein the apparatus comprises a preheater (10), a calciner (20), and a kiln (30), wherein the mineral material is transferred into the preheater (10), from the preheater (10) into the calciner (20), and from the calciner (20) into the kiln (30), wherein, after the thermal treatment, the gas stream is supplied to a first carbon dioxide separation device (60), characterised in that the apparatus comprises a second carbon dioxide separation device (70), wherein the gas stream is conducted from the first carbon dioxide separation device (60) to the second carbon dioxide separation device (70), wherein bypass material and / or filter material is used as a carbon dioxide sorbent in the second carbon dioxide separation device (70).

Description

[0001] Increased decarbonation of a cement plant

[0002] The invention relates to a method for improved separation of carbon dioxide from an exhaust gas stream of a cement plant.

[0003] The cement industry is currently facing the challenge, within the context of global developments, of making the cement production process climate-neutral. To this end, plants are being retrofitted or newly constructed using various technologies. The three most relevant technologies at present are the oxyfuel process, carbonate looping, and amine scrubbing. However, all these processes only capture a certain percentage of the carbon dioxide, typically between 85 and 95%. While a further increase in capture efficiency would be desirable, it would drastically increase energy consumption, which in turn would more than offset the reduction in greenhouse gas emissions.

[0004] German patent KR 102 398 620 B1 discloses an IoT-based, highly efficient system for processing non-degradable exhaust gases and neutralizing carbon using industrial water. The system comprises a first scrubber for removing carbon dioxide and odors from an externally introduced exhaust gas; one or more second scrubbers for removing carbon dioxide and odors from an exhaust gas introduced by the first scrubber; and a third scrubber that discharges a purified gas to the outside. This effectively removes carbon dioxide, particulate matter, and poorly soluble odors.

[0005] Materials and methods for carbon dioxide sequestration are known from US patent 7 906 086 B2.

[0006] The object of the invention is to increase the separation rate in such a way that this is possible without significant additional effort, especially in terms of energy.

[0007] This problem is solved by the method with the features specified in claim 1 and by the device with the features specified in claim 9. Advantageous embodiments are described in the dependent claims, the following description, and the drawings.

[0008] The method according to the invention serves to decarbonate a process for operating a device for the thermal treatment of a mineral material. The process for operating a device for the thermal treatment of a mineral material is well known to those skilled in the art and can be carried out in all embodiments familiar to them. This can, for example, be a system based on the oxyfuel process or a conventional system with an exhaust-side amine scrubber (tailend circuit). The advantage is that the method according to the invention can be used for all these known processes to further increase the carbon dioxide separation efficiency. As is known to those skilled in the art, the device comprises a preheater, an optional calcinator, and a furnace. The calcinator is not a mandatory component – ​​the calcination of the material can also take place in the furnace.The mineral material is transferred to the preheater, from the preheater directly or via the optional calciner, and from the calciner to the furnace. After thermal treatment, the gas stream is fed to a first carbon dioxide separation device. The purpose of this first device is to obtain a carbon dioxide stream, usually in a liquefied and as pure a form as possible, for use or disposal. Due to the efficiency of the first carbon dioxide separation device, which is never 100%, the gas stream leaving the first device still contains carbon dioxide, which is typically released into the environment. The first carbon dioxide separation device is a state-of-the-art carbon dioxide separation device and can, for example, be a cryogenic separation unit.The goal of the first carbon dioxide separation device is to achieve the most complete possible capture of CO2 suitable for further use. Another example would be amine scrubbing. The essential point is that the first carbon dioxide separation device generates a usable CO2 stream for removal.

[0009] According to the invention, the device comprises a second carbon dioxide separation device. The gas stream is routed from the first carbon dioxide separation device to the second carbon dioxide separation device. At least one material, preferably a bypass material and / or a filter material, which is at least partially deacidified within the device, is used as the carbon dioxide sorbent in the second carbon dioxide separation device. Another example of a partially deacidified material is, for example, preheated material. In a bypass between the furnace and the calciner, a portion of the gas stream is separated, and chlorine in the form of chlorine-containing compounds is deposited on the dust by cooling. This prevents the chloride introduced from the mineral feedstock from accumulating in the cycle between the furnace and the calciner, as these chlorides evaporate at the temperatures prevailing in the furnace and then recrystallize at lower temperatures.Similarly, in the cooler, at least a gas stream, such as an air stream, is usually used for the final cooling stage. This gas is also laden with dust, and this dust is separated before the air is released back into the environment. Both dust streams, one from the bypass and one from the cooler exhaust air, are highly decarbonated / deacidified, making these materials ideally suited for binding carbon dioxide. Therefore, using these materials for a second decarbonation stage is very advantageous, as they are generated anyway and typically already precipitate at elevated temperatures, which in turn accelerates the absorption of the carbon dioxide. Since not both material streams from the bypass and the exhaust filter are necessarily generated, it is not essential, but beneficial, to utilize both streams.At least partially deacidified or at least partially decarbonated means that at least 5 mol% of the starting carbonate has been converted to an oxide, which also includes complete conversion, something that is particularly likely in the case of the bypass and the filter dust. The terms deacidified and decarbonated are used synonymously. Since the quantity of bypass material and / or filter material will be too small in most cases, it will preferably be combined with other at least partially deacidified material. Additionally, further material can be added externally, as described below. For primary CO2 capture in the first carbon dioxide separation device, the connection to partially deacidified material would not be sufficient to enable high capture and efficient further use. Therefore, the first and second carbon dioxide separation devices differ fundamentally.The second carbon dioxide separation unit serves only to separate and bind a small residual amount of CO2. After separation, the CO2 is bound to the partially deacidified material; unlike after the first carbon dioxide separation unit, it is not available as a CO2 stream for use or storage. The capacity is minimal, especially if one intends to add this CO2-laden, partially deacidified material to the product. It must be considered that the process requires the separation of at least the entire amount of carbon dioxide (CCh) originating from the limestone, plus the amount of CCh from the fuel. Therefore, even the entire (partially) deacidified material would not be sufficient to bind the CO2.

[0010] The first and second carbon dioxide separation devices are based on different technologies and therefore produce very different products. The advantage of this combination is that in the first carbon dioxide separation device, the main stream is separated and made available as a pure CCh stream for use and / or storage. In contrast, the second carbon dioxide separation device utilizes an existing material to remove residual CO2, i.e., only very small amounts, from the already purified gas. Preferably, the CO2 separation in the first carbon dioxide separation device is at least 90%, more preferably at least 95%, and further preferably at least 99%.Preferably, the second carbon dioxide separation device separates less than 10% of the amount of CO2 separated in the first carbon dioxide separation device; more preferably, the second carbon dioxide separation device separates less than 5% of the amount of CO2 separated in the first carbon dioxide separation device; more preferably, the second carbon dioxide separation device separates less than 2% of the amount of CO2 separated in the first carbon dioxide separation device.

[0011] The recarbonated product is preferably added to the product, thereby permanently binding both the product and the bound carbon dioxide. Furthermore, direct incorporation into the product also allows for the removal of pollutants, such as those originating from a bypass. Alternatively, the recarbonated product can be fed into the furnace to release the bound carbon dioxide, which is then separated via the first carbon dioxide separation device.

[0012] In a further embodiment of the invention, preheated mineral material is additionally fed to the second carbon dioxide separation device after the preheater as a carbon dioxide sorbent. Although this material has a lower degree of decarbonation, usually between 5% and 25%, it is obtained at a temperature between 600 and 650 °C, which is ideal for dry decarbonation. Furthermore, the material flows from the bypass are usually too small for the amount of carbon dioxide still to be reduced, making the addition of further material advantageous. This also allows a simple way to achieve a blended temperature for the material flows of the carbon dioxide sorbents used for decarbonation. If the preheating is multi-stage, the material is drawn off, for example, and preferably, after the last or the penultimate stage of the preheater.Material from the calciner can also be used, which has a very high degree of decarbonation, typically around 80%, and a higher temperature, for example, 850 °C. The advantage of this material stream is that comparatively less material needs to be moved to bind the same amount of CO2.

[0013] In a further embodiment of the invention, waste cement dust from lime production and / or quicklime are additionally fed to the second carbon dioxide separation device as a carbon dioxide sorbent. This is readily available and can thus be put to a value-adding use.

[0014] In a further embodiment of the invention, the product carbonated in the second carbon dioxide separation device is fed directly to the product of the device for the thermal treatment of a mineral material. Besides clinker, cement also contains other components, so these materials, which are only slightly recarbonated here, can be directly added back to the finished product in a value-adding manner, thus ensuring that the bound carbon dioxide remains securely bound in the long term. In another aspect, the invention relates to a device for the thermal treatment of a mineral material. The device comprises a preheater, optionally a calciner, and a furnace, as is familiar to those skilled in the art for such systems. The preheater is arranged in the material flow direction either upstream of the calciner and the calciner upstream of the furnace, or directly upstream of the furnace, as is customary.Downstream of the preheater, a first carbon dioxide separation device is arranged in the direction of gas flow. This first carbon dioxide separation device can be of any type known from the prior art. In particular, it can be a tail-end amine scrubber, which has no feedback to the rest of the plant and can therefore be integrated very easily as a retrofit solution. Alternatively, it can be a carbon dioxide separation device based on the carbonate looping process, whereby the material removed from the carbonate loop can be fed directly into a cement process. Preferably, the overall process is operated according to the oxyfuel process, so that the exhaust gases are already very rich in carbon dioxide, allowing the carbon dioxide separation device to be correspondingly simple and, in the extreme case, could consist only of water separation and liquefaction.Each of these carbon dioxide separation processes naturally has an efficiency of less than 100%. Therefore, the gas stream leaving the first carbon dioxide separation device always still contains a residual amount of carbon dioxide.

[0015] According to the invention, the device comprises a second carbon dioxide separation device. The second carbon dioxide separation device is arranged downstream of the first carbon dioxide separation device. The second carbon dioxide separation device is connected to a component that provides at least partially decarbonated material within the device, for example, and preferably, a bypass filter and / or a dust filter, but also the preheater or the calcinator. This allows the transfer of the at least partially decarbonated material. In particular, the by-streams of already decarbonated material that are generated anyway are used to further decarbonate the residual gas stream, thereby achieving a higher overall separation efficiency and thus further reducing the remaining carbon dioxide emissions.In a further embodiment of the invention, the preheater is connected to the second carbon dioxide separation device for the transfer of the preheated material. This allows very warm, only partially decarbonated material to be used for decarbonating the exhaust gas. Simultaneously, this allows for an increased mixing temperature with the material coming from the bypass filter and / or the dust filter. Furthermore, the quantity of material coming from the bypass filter and / or the dust filter will generally not be sufficient on its own.

[0016] In a further embodiment of the invention, the second carbon dioxide separation device for transferring the recarbonated material is connected to a product outlet. For the purposes of this invention, "product outlet" is to be understood broadly and can simply be the point at which the material is discharged. This could be a storage area, such as a silo, a mill, a truck loading point, or something else. The product outlet can also be directly connected to a feedstock inlet of another, downstream processing device. This achieves long-term stable binding of the carbon dioxide. While recirculation, for example into the furnace, would also be conceivable, the chlorine load would then be returned from the bypass material, thus preventing the removal of the chlorine load.

[0017] If the material fed into the second carbon dioxide separation device is predominantly or completely carbonated (more than 80 mol% carbonate, less than 20% oxide), the material from the second carbon dioxide separation device can be directly mixed with the cement. This is particularly preferred if bypass filter dust and / or recycled cement paste are fed into the second carbon dioxide separation device.

[0018] In a further embodiment of the invention, the second carbon dioxide separation device is connected to the furnace or the optional calciner for transferring the recarbonated material. This is preferred when no bypass material is used, as otherwise the chlorine load would be returned to the cycle. In a further embodiment of the invention, the device includes a third carbon dioxide separation device, which is connected downstream of the second carbon dioxide separation device in terms of gas flow. For example, the second carbon dioxide separation device can be a dry carbon dioxide separation device and the third carbon dioxide separation device a wet carbon dioxide separation device. In this case, it is sufficient if only the second carbon dioxide separation device is operated with a material that is at least partially deacidified in the device.The third carbon dioxide separation device can be operated with material that is at least partially deacidified within the device, material coming from outside, or a mixture.

[0019] The use of a wet carbon dioxide separation device is particularly preferred when using bypass dust, as chlorides, alkali salts and many sulfur compounds dissolve in the water and are thus removed from the cycle.

[0020] In a further embodiment of the invention, the second carbon dioxide separation device has a feed for recycled cement bricks. In addition to internal material flows, the use of recycled concrete and recycled cement bricks obtained from recycled concrete is also a useful source of carbon dioxide sorbent. This is particularly relevant since it can be incorporated into the cement as a clinker substitute and thus also reused.

[0021] In a further embodiment of the invention, the second carbon dioxide separation device has a feed for dust from lime production or a feed for quicklime. These exhibit very high reactivity and are therefore very well suited, and the carbonated material can also be very well integrated into the finished product.

[0022] The device according to the invention is explained in more detail below with reference to exemplary embodiments shown in the drawings.

[0023] Fig. 1 first exemplary device Fig. 2 second exemplary device

[0024] Figure 1 shows a first exemplary apparatus. The mineral material, for example, and in particular limestone, is introduced into the preheater 10, preheated there, and then introduced, still preheated, into the calciner 20. The calcined and thus largely deacidified material is then transferred from the calciner 20 to the furnace 30, fired there, and subsequently cooled in a material cooler 40 and conveyed to the product outlet 50. At the end of the material cooler 40, ambient air is used for final cooling, and the air is then passed through a dust filter 90. The countercurrent gas flow is fed to the material cooler 40 and, preheated from there, fed to the furnace 40. From the furnace, the gas is mostly fed to the calciner 20; a portion passes through a bypass to separate the chloride-containing components in a bypass filter 80.After the calciner 20, the gas is fed to the preheater 10 and from the preheater 10 to the first carbon dioxide separator 60. In this separator, a (usually liquefied) carbon dioxide stream is separated. The remaining exhaust gas is fed to the second carbon dioxide separator 70, where further carbon dioxide is separated using a carbon dioxide sorbent. The carbon dioxide sorbent used is a mixture of material from the bypass filter 80 and the dust filter 90, both of which have a very high degree of decarbonation. Additionally, warm material is extracted after the preheater 10 and mixed with material from the bypass filter 80 and the dust filter 90. Optionally, material from a waste cement block storage area 100 can also be added. The carbon dioxide extracted in the second carbon dioxide separator 70 is then recarbonated and fed to the product outlet 50. The product outlet 50 can, for example, be a silo.

[0025] The exemplary apparatus shown in Fig. 2 differs from the first exemplary apparatus shown in Fig. 1 in that the material from the second carbon dioxide separation device 70 is returned to the furnace 30. Therefore, using material from a bypass, which is not shown in this second exemplary apparatus, would be disadvantageous, as this would result in the chlorine load being returned. As a second variation, the material is taken not after the preheater 10, but after the calcinator 20 and fed to the second carbon dioxide separation device 70. This results in a significantly higher degree of decarbonation of the material, enabling efficient separation of carbon dioxide from the gas stream, thus requiring less material to bind the carbon dioxide. Reference numerals

[0026] 10 preheaters

[0027] 20 Calcinator

[0028] 30 oven

[0029] 40 Material cooler 50 Product outlet

[0030] 60 first carbon dioxide separation device

[0031] 70 second carbon dioxide separation device

[0032] 80 Bypass filters

[0033] 90 dust filters, 100 old cement block storage

Claims

Patent claims 1. A method for decarbonating a method for operating a device for the thermal treatment of a mineral material, wherein the device comprises a preheater (10), an optional calcinator (20) and a furnace (30), wherein the mineral material is transferred into the preheater (10), from the preheater (10) directly or via the optional calcinator (20) into the furnace (30), wherein the gas stream after the thermal treatment is fed to a first carbon dioxide separation device (60), characterized in that the device comprises a second carbon dioxide separation device (70), wherein the gas stream is directed from the first carbon dioxide separation device (60) to the second carbon dioxide separation device (70), wherein at least one material that is at least partially deacidified in the device is used as the carbon dioxide sorbent in the second carbon dioxide separation device (70).

2. Method according to claim 1, characterized in that a bypass material and / or a filter material is selected as the partially deacidified material.

3. Method according to one of the preceding claims, characterized in that preheated mineral material is additionally supplied to the second carbon dioxide separation device (70) after the preheater (10) as carbon dioxide sorbent.

4. Method according to one of the preceding claims, characterized in that waste cement stone, dust from lime production, burnt lime, is additionally supplied to the second carbon dioxide separation device (70) as a carbon dioxide sorbent.

5. Method according to one of the preceding claims, characterized in that the product carbonated in the second carbon dioxide separation device (70) is directly fed to the product of the device for the thermal treatment of a mineral material.

6. Method according to one of the preceding claims, characterized in that the first carbon dioxide separation device (60) and the second carbon dioxide separation device (70) use different technologies.

7. Method according to one of the preceding claims, characterized in that in the first carbon dioxide separation device (60) at least 90% of the CO2, preferably at least 95% of the CO2, more preferably at least 99% of the CO2 are separated.

8. Method according to one of the preceding claims, characterized in that the second carbon dioxide separation device (70) separates less than 10% of the amount of CO2 that is separated in the first carbon dioxide separation device (60), preferably less than 5% of the amount of CO2, more preferably less than 2% of the amount of CO2.

9. Device for the thermal treatment of a mineral material, the device comprising a preheater (10), optionally a calciner (20) and a furnace (30), wherein the preheater (10) is arranged in the material flow direction directly or via the optional calciner (20) upstream of the furnace (30), wherein a first carbon dioxide separation device (60) is arranged downstream of the preheater (10) in the gas flow direction, characterized in that the device comprises a second carbon dioxide separation device (70), wherein the second carbon dioxide separation device (70) is arranged downstream of the first carbon dioxide separation device (60), wherein the second carbon dioxide separation device (70) is connected to a bypass filter (80) and / or a dust filter (90) and / or the preheater and / or the calciner for transferring the bypass material and / or the filter material and / or partially deacidified material.

10. Device according to claim 9, characterized in that the preheater (10) is connected to the second carbon dioxide separation device (70) for transferring the preheated material.

11. Device according to any one of claims 9 to 10, characterized in that the second carbon dioxide separation device (70) is connected to a product outlet (50) for transferring the recarbonated material.

12. Device according to any one of claims 9 to 11, characterized in that the second carbon dioxide separation device (70) has a feed for waste cement bricks, a feed for dust from lime production, or a feed for quicklime.

13. Device according to any one of claims 9 to 12, characterized in that the first carbon dioxide separation device (60) is different from the second carbon dioxide separation device (70).

14. Device according to claim 13, characterized in that the first carbon dioxide separation device (60) performs cryogenic separation or a It's an amine wash.

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