Optimised decarbonisation in clinker production

Abstract

The present invention relates to an apparatus for thermally treating a mineral material, wherein the apparatus comprises a preheater (10), a calciner (20), and a material cooler (40), wherein the preheater (10) is arranged upstream of the calciner (20) in the material flow direction and the calciner (20) is arranged upstream of the material cooler (40), wherein the apparatus comprises an oxygen gas source (70), wherein the oxygen gas source (70) is connected to the calciner (20), characterised in that a heat exchanger (60) is arranged between the oxygen gas source (70) and the calciner (20), wherein the heat exchanger (60) is arranged between the calciner (20) and the material cooler (40) in the material flow direction, wherein the oxygen gas source (70) and the heat exchanger (60) are connected for transferring an oxygen-containing gas, wherein the heat exchanger (60) and the calciner (20) are connected for transferring an oxygen-containing gas, and wherein the calciner (20) and the heat exchanger (60) are connected to one another for transferring a material stream.

Description

[0001] Optimized decarbonation in clinker production

[0002] The invention relates to a device for the thermal treatment of a mineral material, in particular for the calcination of carbonate material, for example limestone, which concentrates and separates the resulting carbon dioxide for separation.

[0003] In the current situation, reducing carbon dioxide emissions is a political, social, and economic imperative. Rapid implementation is crucial, particularly finding solutions that allow existing plants to be retrofitted to capture at least a significant portion of the carbon dioxide, thus focusing on a rapid, though not complete, reduction of carbon dioxide emissions. The cement industry offers significant potential in this regard, as the production of clinker from limestone releases substantial amounts of CO2 from the mineral material. This means that only about one-fifth of the CO2 emissions originate from the fuel itself, while simultaneously generating very high quantities of CO2.

[0004] One of the most interesting options for decarbonizing the cement and lime industries is oxyfuel technology, which uses the purest possible oxygen for combustion. Ideally, the combustion of organic material produces carbon dioxide and water. Water is very easy to separate, while nitrogen separation is considerably more complex. Therefore, reducing the nitrogen input significantly simplifies carbon dioxide removal.

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

[0006] One drawback of such a solution, however, is that the oxygen would be supplied to the calcinator at a low temperature. To ensure sufficient lifting capacity, the use of hot lifting gas at least 750 °C is advantageous to prevent the flow cross-sections from becoming too small and to simultaneously enable the ignition of fuel in the subsequent calciner. Therefore, burners or separate combustion chambers are currently used to preheat the oxygen and subsequently ignite the fuel supplied to the calciner. For technical reasons, however, only high-quality fuels such as pulverized coal or natural gas are suitable for this purpose, whereas alternative fuels, such as biomass, can often be used in the calciner itself. It would therefore be desirable to be able to forgo these primary resources for preheating the oxygen.

[0007] WO 2022 / 179847 A1 discloses a height-optimized device for the heat treatment of mineral substances.

[0008] From WO 2024 / 033831 A1 a process and a plant for the production of cement-like materials are known.

[0009] From DE 10 2022 209877 A1, the exclusive use of substitute fuels for the thermal treatment of mineral substances, in particular clays, is known.

[0010] From WO 2024 / 170265 A1, an optimized heat management system in a plant for the thermal treatment of mineral substances is known.

[0011] Calcination of carbonates is known from WO 2024 / 102480 A1.

[0012] The object of the invention is to adapt the oxygen supply to the calcinator in such a way that valuable primary fuels can be dispensed with.

[0013] This problem is solved by the device with the features specified in claim 1 and by the method with the features specified in claim 9. Advantageous embodiments are described in the dependent claims, the following description, and the drawing.

[0014] The device according to the invention is used for the thermal treatment of a mineral material, in particular a device for the calcination of limestone. The device comprises a preheater, a calciner, and a material cooler. The preheater is arranged upstream of the calciner in the material flow direction, and the calciner is arranged upstream of the material cooler. The calciner is also arranged upstream of the optional kiln in the material flow direction. This corresponds to the classic arrangement in a cement plant. The device includes an oxygen gas source. The oxygen gas source can, for example, and preferably, be an air separation plant, such as a cryogenic air separation process (Linde process). It can also be a tank for liquid oxygen. The oxygen gas source preferably contains oxygen with at least 50% by volume, more preferably at least 75% by volume, and more preferably at least 90% by volume.Provide at least 95% by volume of oxygen. The oxygen gas source is connected to the calcinator for transferring the oxygen-containing gas.

[0015] According to the invention, a heat exchanger is arranged between the oxygen gas source and the calcinator. In the direction of material flow, the heat exchanger is arranged between the calcinator and the material cooler. The oxygen gas source and the heat exchanger are connected to transfer an oxygen-containing gas. Furthermore, the heat exchanger and the calcinator are connected to transfer an oxygen-containing gas. The calcinator and the heat exchanger are connected to transfer a material flow of the material calcined in the calcinator. This material has a very high temperature according to the calcination conditions.

[0016] According to the invention, the device comprises a material cooler but no furnace. This is sufficient, for example, in the lime industry when complete decarbonation is not necessary. In this case, the calciner is directly connected to the material cooler for transferring the material. The material cooler is preferably designed as a cyclone cooler. This device according to the invention thus represents a stand-alone solution for a calciner, i.e., without a furnace, for the production of calcined clinker. In a further embodiment of the invention, the heat exchanger is selected from the list comprising co-current or counter-current reactors, in particular a cyclone, a fluidized bed reactor, or a stationary or non-stationary fluidized bed reactor.

[0017] In a further embodiment of the invention, the heat exchanger comprises at least a first heat exchanger stage and a second heat exchanger stage. Such a cascaded design makes it possible to preheat the oxygen-containing gas to a higher temperature. Furthermore, the pure oxygen gas flow is comparatively small, so the capacity to support calcined, i.e., hot, material may be limited, and thus the maximum amount of heat that can be supplied is also limited. Due to the cascaded design, the oxygen-containing gas can be brought into contact with a larger amount of calcined, i.e., hot, material and thus heated more effectively if the capacity is insufficient.

[0018] In a further embodiment of the invention, the oxygen gas source and the first heat exchanger stage are connected for transferring the oxygen-containing gas. The first heat exchanger stage and the second heat exchanger stage are connected for transferring an oxygen-containing gas. Furthermore, the second heat exchanger stage and the calcinator are connected for transferring an oxygen-containing gas. The oxygen-containing gas thus cascades through the stages of the heat exchanger. The calcinator and the first heat exchanger stage are connected to each other for transferring the material flow. Furthermore, the calcinator and the second heat exchanger stage are also connected to each other for transferring the material flow. Thus, calcined material at the maximum temperature is fed into both heat exchanger stages. This differs from the usual practice of also cascading the solid material, but in counterflow to the gas flow.This ensures that the material passing through the heat exchanger is not cooled down as much and is therefore fed to the material cooler at a warmer temperature. Furthermore, this maximizes the temperature difference, which in turn accelerates the heating of the oxygen-containing gas and ultimately leads to a higher final temperature. The first heat exchanger stage and the material cooler are connected to each other for transferring the material flow, and the second heat exchanger stage and the material cooler are also connected to each other for transferring the material flow. Cooling to a suitable storage or transport temperature takes place in the material cooler.

[0019] In a further embodiment of the invention, an electric heating device for heating the oxygen-containing gas is arranged between the heat exchanger and the calcinator. Since the preheater can already achieve an elevated temperature, but this must always be lower than that in the calcinator, the difference can be made, if necessary, by an electric heating device, as this can be operated without the insertion of a new CO2 source. However, since electricity is usually more expensive than the fuels, only superheating after the heating in the preheater is advantageous here in order to keep costs as low as possible.

[0020] In a further embodiment of the invention, the calcinator is connected to the heat exchanger for the transfer of carbon dioxide-containing gas. This can occur directly or via the additional preheater and optionally further components, for example, a dust filter. By recirculating carbon dioxide, the volume flow in the calcinator can be increased, thus easily increasing the carrying capacity for solids. Preferably, the hot gas is used directly after the calcinator. However, the carbon dioxide-containing gas can also originate from an additional preheater located downstream of the calcinator in the gas flow direction. In this case, the carbon dioxide-containing gas can be fed to the oxygen-containing gas before, within, or after the preheater. To optimally utilize the temperature gradients, feeding the gas after the preheater is preferred.On the other hand, feeding material before the preheater allows for a higher solids loading and thus the feeding of more calcined material and therefore more heat.

[0021] In another embodiment of the invention, the calcinator is connected downstream of a carbon dioxide separation device.

[0022] In a further embodiment of the invention, the material cooler comprises at least one first material cooler stage. The material cooler can consist of this first material cooler stage or have further stages. The heat exchanger comprises at least one first heat exchanger stage. The heat exchanger can consist of this first heat exchanger stage or have further stages. The enclosed volume of the first material cooler stage is larger than the enclosed volume of the first heat exchanger stage. Preferably, the enclosed volume of the first material cooler stage is at least twice as large as the enclosed volume of the first heat exchanger stage. If the material cooler and / or the heat exchanger have further stages, this preferably applies to all stages. A second material cooler stage would also be larger than a second heat exchanger stage, and so on.

[0023] In another aspect, the invention relates to a method for the thermal treatment of a mineral material, particularly in the cement industry. The mineral material is successively preheated in a preheater, calcined in a calcinator, and cooled in a material cooler. This corresponds to the conventional method. Preferably, the oxygen-containing gas is an oxygen-enriched gas in order to operate the calcinator in the oxyfuel process. The oxygen-containing gas is preheated in a heat exchanger before entering the calcinator. This is advantageous to ensure a reliable ignition temperature in the calcinator, for example, and especially when using alternative fuels such as biomass. The material calcined in the calcinator is fed at least partially to the heat exchanger.There, the calcined material releases some of its heat, warming the oxygen-containing gas without the need for fuel. Due to the lower partial pressure of carbon dioxide compared to the calciner, the calcined material is further deacidified by being introduced into the oxygen-containing gas stream in the heat exchanger. This increases the area operated in the oxyfuel process and thus the total amount of carbon dioxide separated.

[0024] According to the invention, the mineral material is successively preheated in a preheater, calcined in a calcinator, and cooled in a material cooler. The material calcined in the calcinator is at least partially fed to the heat exchanger and from the heat exchanger to the material cooler. In a further embodiment of the invention, the heat exchanger has at least one first heat exchanger stage and one second heat exchanger stage. However, it can also have three or more stages. The oxygen-containing gas is first fed into the first heat exchanger stage and is then fed from the first heat exchanger stage into the second heat exchanger stage. If the heat exchanger has further stages, the oxygen-containing gas is also passed through these stages in a cascaded manner. From the second heat exchanger stage (possibly via further stages), the oxygen-containing gas is fed into the calcinator.Calcined material is fed from the calciner in parallel to the first and second heat exchanger stages, rather than cascaded in counterflow to the oxygen-containing gas. This ensures that each stage receives the mineral material at the highest temperature. Furthermore, the carrying capacity of the oxygen-containing gas is lower than that of the calcined material due to the smaller gas volume compared to the calciner, which generates large quantities of carbon dioxide. Therefore, by distributing the solids stream across the different stages, sufficient carrying capacity can be more easily guaranteed, allowing a larger proportion, or even the entire, of the solids stream to be used for preheating. The calcined material from the first and second heat exchanger stages is then recombined and fed to the material cooler.This ensures that the maximum amount of heat is available at each stage through the calcined material, making it easier to achieve a higher final temperature.

[0025] In an alternative embodiment, the mineral material is cascaded and passed in counterflow through the stages of the heat exchanger.

[0026] In a further embodiment of the invention, the oxygen-containing gas between the heat exchanger and the calcinator is electrically heated. Since the heat exchanger can only ever reach a lower temperature level than the material used for heating, in this case the calcined material, additional electric heating can be advantageous. The benefit of electric heating is that it is easier to integrate into a carbon dioxide reduction concept. In a further embodiment of the invention, the gas coming from the calcinator is heated by an electric heating element.

[0027] Carbon dioxide is separated in a carbon dioxide separation device.

[0028] In a further embodiment of the invention, the calcinator is operated according to the oxyfuel process. This means that the supplied oxygen-containing gas has at least 50 vol%, preferably at least 75 vol%, more preferably at least 90 vol%, and particularly preferably at least 95 vol% oxygen. Two different operating modes of the oxyfuel process are distinguished. In the first operating mode, carbon dioxide-containing gas is recirculated after the calcinator to its gas inlet. In simplified terms, the recirculated carbon dioxide essentially replaces the nitrogen from the air in the conventional process, so that the calcinator can be operated practically like a conventional one with regard to load-bearing capacity and combustion properties. In the second operating mode, no gas is recirculated.This reduces the amount of gas in the calcinator; the process must be adapted to the reduced amount of gas. However, the process is more efficient due to the lack of gas recirculation, because the calcinator and preheater can be built considerably smaller, the thermal efficiency of the process is significantly improved, the amount of air drawn in through recirculation and larger cross-sections is reduced, leading to a lower proportion of inert gases, such as nitrogen and argon, in the exhaust gas and improving the energy efficiency of the downstream CO2 purification.

[0029] In a further embodiment of the invention, the oxygen-containing gas supplied to the calcinator is heated to at least 500 °C, preferably to at least 700 °C, particularly preferably to at least 1000 °C, before it is supplied to the calcinator.

[0030] In a further embodiment of the invention, a substitute fuel is supplied to the calcinator for combustion. Biomass is particularly preferably selected as the substitute fuel, so that, in combination with carbon dioxide separation, a negative carbon dioxide emission can be achieved for the calcinator in terms of net emissions. In a further embodiment of the invention, the heat exchanger is designed as a gravity separator. The heat exchanger is operated with a loading of at least 3 kg of solids per kg of gas, preferably at least 5 kg of solids per kg of gas, and particularly preferably at least 10 kg of solids per kg of gas.

[0031] In a further embodiment of the invention, the heat exchanger is designed as a multi-stage direct heat exchanger. The heat exchanger is operated with a loading of at most 3 kg of solids per kg of gas, preferably at most 2 kg of solids per kg of gas.

[0032] The device according to the invention is explained in more detail below with reference to an embodiment shown in the drawing.

[0033] Fig. 1 schematic exemplary device, not according to the invention.

[0034] Fig. 2 schematic further exemplary device, not according to the invention.

[0035] Fig. 3 schematic further exemplary device, according to the invention.

[0036] Figure 1 schematically shows an exemplary device not according to the invention. For example, the area shown on the right in the illustration can be an existing existing plant, while the area shown on the left shows the retrofit with a calcinator 20 operated according to the oxyfuel process with a carbon dioxide separation device 50, i.e., in particular a retrofit solution for an existing plant for a significant reduction of carbon dioxide emissions.

[0037] The raw material, in particular limestone, is fed into the preheater 10 and heated there by a gas stream from the kiln 30. The preheated material is transferred to the calciner 20 and calcined there. The calcined material is then transferred to the kiln 30, fired there, and subsequently cooled in the material cooler 40. The air from the material cooler 40 is preheated and supplied to the kiln 30. The material cooler 40, kiln 30, and preheater 10 are operated with normal ambient air, and the exhaust gases are released back into the environment. Optionally, a further calciner 22 can be provided, which may, for example, be existing equipment. This can be partially operated or simply used as a gas line.

[0038] The calcinator 20 is preferably operated according to the oxyfuel process in a gas stream separate from the furnace 30 and preheater 10. For this purpose, a gas with at least 95 vol% oxygen is provided by means of an oxygen gas source 70, for example by means of a membrane process. The oxygen-containing gas is transferred to the heat exchanger 60, which is configured here as a three-stage unit. The oxygen-containing gas is passed successively through the third heat exchanger stage 63, the second heat exchanger stage 62, and the first heat exchanger stage 61, and is thus preheated before entering the calcinator 20. The calcined material coming from the calcinator 20 serves to preheat the oxygen-containing gas in the heat exchanger 60. This material is fed in parallel, and thus at its highest temperature, to the first heat exchanger stage 61, the second heat exchanger stage 62, and the third heat exchanger stage 63, and is then fed to the furnace 30.The gas coming from the calcinator 20 is fed via a further preheater 12 to the carbon dioxide separator 50 for heat recovery. Since only small amounts of nitrogen or argon are introduced into the gas stream from the oxygen gas source 70, the gas at the inlet of the carbon dioxide separator 50 consists mainly of water vapor and carbon dioxide, which significantly simplifies the carbon dioxide separation.

[0039] Fig. 2 shows another exemplary device not according to the invention, which differs from the exemplary device shown in Fig. 1 in that the heat exchanger 60 is designed entirely in counterflow. The material flow is thus led from the calcinator 20 via the first heat exchanger stage 61, the second heat exchanger stage 62, and the third heat exchanger stage 63 into the furnace 30.

[0040] Fig. 3 shows a solution according to the invention that operates without a furnace 30. Therefore, the material cooler 40 in the example shown is three-stage, consisting of a first material cooler stage 41, a second material cooler stage 42, and a third material cooler stage 43. The device also includes a preheater 80. This allows the material cooler 40 and the preheater 80 to be operated, for example, with a gas stream of air without introducing unwanted gases into the calciner 20. Reference numerals

[0041] 10 preheaters

[0042] 12 additional preheaters 20 Calcinators

[0043] 22 more Calcinators

[0044] 30 oven

[0045] 40 material coolers

[0046] 41 First material cooler stage 42 Second material cooler stage

[0047] 43 third material cooling stage

[0048] 50 Carbon dioxide separator

[0049] 60 heat exchangers

[0050] 61 First heat exchanger stage 62 Second heat exchanger stage

[0051] 63 third heat exchanger stage

[0052] 70 Oxygen gas source

[0053] 80 pre-heaters

Claims

Patent claims 1. Device for the thermal treatment of a mineral material, wherein the The device comprises a preheater (10), a calcinator (20), and a material cooler (40), wherein the preheater (10) is arranged upstream of the calcinator (20) in the material flow direction, and the calcinator (20) is arranged upstream of the material cooler (40), wherein the device comprises an oxygen gas source (70), wherein the oxygen gas source (70) is connected to the calcinator (20), characterized in that a heat exchanger (60) is arranged between the oxygen gas source (70) and the calcinator (20), wherein in The material flow direction of the heat exchanger (60) is arranged between the calcinator (20) and the material cooler (40), wherein the oxygen gas source (70) and the heat exchanger (60) are connected for the transfer of an oxygen-containing gas, wherein the heat exchanger (60) and the calcinator (20) are connected for the transfer of an oxygen-containing gas, wherein the calcinator (20) and the heat exchanger (60) are connected to each other for the transfer of a material flow.

2. Device according to claim 1, characterized in that the material cooler is designed as a cyclone cooler.

3. Device according to one of the preceding claims, characterized in that the heat exchanger (60) is selected from the list comprising a co-current or counter-current reactor, in particular a cyclone, a fluidized bed reactor, a stationary or non-stationary fluidized bed reactor.

4. Device according to one of the preceding claims, characterized in that an electric heating device for heating the oxygen-containing gas is arranged between the heat exchanger (60) and the calcinator (20).

5. Device according to one of the preceding claims, characterized in that the calcinator (20) is connected to the heat exchanger (60) for transferring carbon dioxide-containing gas.

6. Device according to one of the preceding claims, characterized in that the calcinator (20) is connected downstream of a carbon dioxide separation device (50).

7. Device according to one of the preceding claims, characterized in that the material cooler (40) has at least one first material cooler stage (41), wherein the heat exchanger (60) has at least one first heat exchanger stage (61), wherein the enclosed volume of the first material cooler stage (41) is larger than the enclosed volume of the first heat exchanger stage (61).

8. Device according to claim 7, characterized in that the enclosed volume of the first material cooler stage (41 ) is at least a factor of 2 larger than the enclosed volume of the first heat exchanger stage (61 ).

9. Method for the thermal treatment of a mineral material, wherein the mineral material is successively preheated in a preheater (10) and calcined in a calcinator (20) and cooled in a material cooler (40), wherein an oxygen-containing gas is supplied to the calcinator (20), wherein the oxygen-containing gas is preheated in a heat exchanger before the calcinator (20), and wherein at least a proportion of the material calcined in the calcinator (20) is supplied to the heat exchanger.

10. Method according to claim 9, characterized in that the oxygen-containing gas is electrically heated between the heat exchanger and the calcinator (20).

11. Method according to one of claims 9 to 10 characterized in that the carbon dioxide coming from the calcinator (20) is separated in a carbon dioxide separation device (50).

12. Method according to one of claims 9 to 11, characterized in that the oxygen-containing gas supplied to the calcinator (20) is heated to at least 500 °C, preferably to at least 700 °C, particularly preferably to at least 1000 °C, before it is supplied to the calcinator (20).

13. A method according to any one of claims 9 to 12, characterized in that a substitute fuel is supplied to the calcinator (20) for combustion.

14. A method according to any one of claims 9 to 13, characterized in that the heat exchanger (60) is designed as a gravity separator, wherein the heat exchanger (60) is operated with a loading of at least 3 kg of solids per kg of gas, preferably at least 5 kg of solids per kg of gas, and particularly preferably at least 10 kg of solids per kg of gas.

15. Method according to one of claims 9 to 13, characterized in that the heat exchanger (60) is designed as a multi-stage direct heat exchanger (60), wherein the heat exchanger (60) is operated with a loading of at most 3 kg of solids per kg of gas, preferably at most 2 kg of solids per kg of gas.

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