Reduction of co2 emissions in cement clinker production

Abstract

The invention relates to a plant for producing cement clinker, comprising a feedstock supply facility 10, a mill 50, a preheater 60, a calciner 70, a kiln 80 and a material cooler 90, in which a material stream is conveyed from the feedstock supply facility 10 via the mill 50, the preheater 60, the calciner 70, the kiln 80 and the material cooler 90, characterized in that the material cooler 90 comprises a product outlet, the apparatus comprises a screening device 30 connected to a feedstock supply facility 10 to supply feedstock, the screening device 30 being configured to remove a coarse particle stream and a fine particle stream; the apparatus comprises a shaft kiln 40 to which the screening device 30 is connected to convey a stream of coarse particles, the shaft kiln 40 being connected to the mill 50 to convey the heat-treated feedstock.

Description

[0001] The present invention relates to a device and a process for simple partial removal of CO2 in the cement clinker production process.

[0002] One option is to strip the CO2 from the exhaust gas of any plant and remove it. Such processes can be generally applied. However, these processes are complicated by the high nitrogen content in the exhaust gas that is usually present. Therefore, there are some plants that operate with pure oxygen, for example, which ultimately forms almost pure CO2, so that no further removal is necessary. However, this usually requires a reconstruction of the plant.

[0003] Patents DE 10 2018 206 673 A1 and DE 10 2018 206 674 A1 disclose a cement clinker production plant which is operated with highly enriched oxygen, the exhaust gas of which therefore contains extremely pure carbon dioxide, which can be removed relatively easily for utilization or storage. However, the disadvantage is that existing plants must be completely remodeled or new plants must be built.

[0004] It is therefore desirable to retrofit existing plants in a simple manner in order to at least partially reduce CO2 emissions without having to build completely new plants. The focus is therefore on quick and simple retrofits, but correspondingly only partial abatement can be achieved.

[0005] Patent DE 10 2021 204 175 discloses a lime shaft kiln.

[0006] Patent DE 10 2021 202 485 discloses an annular shaft kiln.

[0007] Patent DE 11 2010 004 030 B4 discloses a vertical incineration kiln having three concentric cylinders.

[0008] Patent EP 2 018 353 B1 discloses a process and an apparatus for producing cement clinker.

[0009] Patent WO 2007 / 099 415 A1 discloses a process and an apparatus for drying and conveying wet mineral raw materials.

[0010] Patent DE 199 29 066 A1 discloses a cement clinker production plant.

[0011] Patent DE 198 45 495 A1 discloses a process for burning carbonate-containing rocks to generate a waste gas stream with a high CO 2 content, and a double shaft kiln for carrying out the process.

[0012] Patent DE 10 2008 059 370 A1 discloses a process and a device for cement production.

[0013] The object of the present invention is to provide a cement clinker production plant based on conventional plants which removes part of the CO2 in a simple manner.

[0014] This object is achieved by an apparatus having the features specified in claim 1, and by a process having the features specified in claim 6. Advantageous developments emerge from the dependent claims, the following description and the drawings.

[0015] The device of the present invention is used to produce cement clinker. The device includes a raw material supply facility, a mill, a preheater, a calciner, a kiln and a material cooler. The raw material supply facility can be a storage yard, a delivery point (such as an unloading station), a silo or a similar facility. The material flow passes through the mill, the preheater, the calciner, the kiln and the material cooler from the raw material supply facility. The material cooler includes a product outlet. Accordingly, the device is a traditional cement clinker production device. In particular, the device can also be an existing cement clinker production device, which is redesigned to achieve the purpose of the present invention by reducing part of the CO2 emissions through a simple method. Therefore, the cement clinker production device according to the introduction part is known to those skilled in the art.

[0016] According to the invention, a corresponding prior art plant is modified in order to remove part of the CO 2 in a simple manner, so that the climate impact is reduced quickly within the framework of simple measures.

[0017] The device comprises a screening device. The screening device is connected to the raw material supply facility for providing raw materials. The screening device is configured to remove a coarse particle flow and a fine particle flow. The separation between coarse particles and fine particles is preferably carried out between 5 mm and 50 mm, although the exact separation limit is not necessary and technically reasonable. For example, even during the screening process, fine particles may accidentally enter the coarse particle part. Therefore, the separation range of coarse particles and fine particles is between 5 mm and 50 mm. As a purely exemplary illustration, using a screen with an aperture size of 30 mm, ideally all fine particle parts with particles less than 30 mm and coarse particle parts with particles greater than 30 mm will be produced. Therefore, the fine particle part is present in the fine particle flow, and the coarse particle part is present in the coarse particle flow. The device comprises a vertical kiln. Vertical kilns are well-known devices; illustratively and preferably, the vertical kiln can be a kiln according to the description in patent DE 10 2021 204 175 or DE 10 2021 202 485. The screening device is connected to the vertical kiln to convey the coarse particle flow. In the shaft kiln, only the coarse fraction is heat treated. The shaft kiln is connected to the mill and is used to transport the heat treated raw material.

[0018] The process of firing carbonate rocks in a PFR shaft kiln has been known for about 60 years. For example, a PFR shaft kiln described in patent WO 2011 / 072894A1 comprises two vertically parallel shafts, which are operated in a cyclical manner, wherein combustion takes place only in one shaft, the corresponding combustion shaft, while the other shaft is operated as a regeneration shaft. The combustion shaft is supplied with oxidizing gas co-flowing with the material and the fuel, and the hot exhaust gas generated, together with the heated cooling air supplied from below, enters the exhaust gas shaft through an overflow channel, where the exhaust gas flows countercurrently to the material and is discharged upwards, while preheating the material in the process. The material is usually fed into the shaft from the top together with the oxidizing gas, and the fuel is injected into the combustion zone. The material to be fired usually passes in each shaft through a preheating zone for preheating the material, a combustion zone for firing the material, and then a cooling zone, where cooling air is supplied to the hot material.

[0019] It was found that, especially in the coarse fraction, CO2 can be easily removed from the starting material due to the large lime particles. In addition, another advantage is that the grindability of the material, especially the coarse particles, can be improved by thermal treatment. In this case, the shaft kiln does not need to achieve complete decarbonization. On the contrary, in order to maximize the efficiency of the entire system, it is advantageous to decarbonize the coarse fraction only to an extent of 80% to 90%. The material thermally treated by the shaft kiln is fed through the mill to the conventional operation of the preheater, calciner and kiln, so that the complete thermal treatment is completed here, especially in the kiln. However, due to the action of the shaft kiln, the fuel demand in the calciner is reduced, and the release of CO2 from the starting material is also reduced. Therefore, the existing equipment can remain unchanged; the removal of CO2 is limited to the CO2 emissions of the shaft kiln.

[0020] The lime kiln system, for example, comprises at least a shaft kiln for firing and cooling materials, such as carbonate rock, and the lime kiln system comprises two shafts and a passage extending between the two shafts. The shaft kiln comprises one of the shafts of the lime kiln system, the shaft having a material inlet for introducing materials into the shaft for firing, and a preheating zone for preheating the materials in the material flow direction, a combustion zone for firing the materials, a cooling zone for cooling the materials, and a material outlet for discharging the materials from the shaft. The passage has a closing device for closing the passage to block the gas and prevent the gas from flowing between the two shafts through the passage. The material for firing is preferably limestone or dolomite, with a particle size of 10 to 200 mm, preferably 15 to 120 mm, and more preferably 30 to 100 mm. The cooling gas comprises air, for example. The lime kiln system preferably comprises a shaft kiln, which can be operated as a co-current regeneration shaft kiln, wherein the passage for connecting the shaft, especially the shaft combustion zone, is closed. The lime kiln system comprises at least one shaft kiln. For example, the shaft kiln system comprises two shaft kilns, each of which contains precisely one shaft of the lime kiln system. The shaft kilns are preferably separated from each other in terms of gas, in particular they can be operated independently of each other to burn the material. The shaft of at least one shaft kiln of the lime kiln system preferably comprises a material inlet for introducing the burning material into the shaft, the material inlet being particularly located at the upper end of the shaft so that the material falls into the shaft under the action of gravity. The material inlet and / or the material outlet are particularly configured as locks for introducing and / or discharging the material into the shaft kiln. The material inlet configured as a lock is preferably designed to allow only the raw material for burning to enter the shaft, without allowing ambient air to enter. The lock is preferably configured to provide a gas-tight seal between the shaft and the environment and to allow solids such as combustion materials to enter the shaft. In the flow direction of the material, after passing through the material inlet, the material flows through a preheating zone, where the material is preheated to a temperature of, for example, about 600° C. to 800° C. The combustion zone follows the preheating zone, preferably directly connected, for burning the material, the material being heated to a temperature of about 900° C. to 1600° C. The cooling zone follows the combustion zone, preferably directly connected, and is used to cool the fired material to a temperature of about 100° C. The material outlet is, for example, located in an outlet hopper downstream of the cooling zone, and the material outlet includes, for example, a turntable or a push plate, for discharging the material from the cooling zone into the outlet hopper. The cooling gas is blown into the cooling zone of the shaft kiln, preferably through a cooling gas inlet. The cooling gas inlet is preferably located in the cooling zone, in particular below the turntable. A plurality of burners, in particular burner lances, are preferably arranged in the combustion zone of the shaft. It is also conceivable that the shaft includes a plurality of side burners, which extend through the shaft wall to the combustion zone. The side burners are preferably configured as burner lances, in particular tubular structures. They are used for the passage of fuel and preferably oxidants, which are introduced into the combustion zone together with the exhaust gases. The closing device preferably extends to the entire cross-section of the channel. Closing the gas passage of the channel using a closing device allows the two shafts of the lime kiln system to be operated independently.For a description of further embodiments, please refer to patent DE 10 2021 204 175.

[0021] According to the invention, the shaft kiln is designed to operate with a gas containing at least 50% oxygen.

[0022] In a further embodiment of the invention, the screening device is designed for separation between 5 mm and 50 mm. Therefore, the mesh size of the screening device is selected to be between 5 mm and 50 mm. In this case, the fine particle fraction is below the selected value and the coarse particle fraction is above the selected value.

[0023] In a further embodiment of the invention, the shaft kiln is designed to operate with a gas of at least 90% oxygen. In case of the use of pure oxygen (and no other gases from the raw materials), the exhaust gas stream resulting from the combustion and the CO2 released in the lime (after removal of water) will be pure carbon dioxide and can therefore be simply further utilized or stored. Considering that the conversion of an existing cement plant only requires the installation of an additional shaft kiln, the kiln can be designed to operate with highly enriched oxygen without the need to upgrade existing components such as preheaters, calciners and kilns. By using an oxygen-enriched gas, the removal of CO2 becomes very simple.

[0024] In a further embodiment of the invention, a CO2 deposition device is provided downstream of the shaft kiln. The device can be realized particularly simply if the shaft kiln is designed to operate with a gas containing at least 50% oxygen, preferably at least 90% oxygen. It is usually always necessary to remove moisture. A dust collector or other conventional pretreatment device can be provided upstream of the CO2 deposition device.

[0025] In a further embodiment of the invention, the apparatus comprises two shaft kilns. More specifically, these shaft kilns are implemented and operated alternately according to the description of patent DE 10 2021 204 175. This arrangement is known as a parallel flow regenerative lime shaft kiln.

[0026] In a further aspect, the present invention relates to a process for producing cement clinker. The process of the present invention is preferably implemented using the apparatus of the present invention. The process comprises the following steps:

[0027] a) screening the raw materials into a coarse particle portion and a fine particle portion;

[0028] b) heat treating the coarse fraction in a shaft kiln with a gas containing at least 50% oxygen;

[0029] c) mixing the fine particle portion with the heat-treated coarse particle portion and then grinding, or separately grinding the fine particle portion and the heat-treated coarse particle portion and then mixing;

[0030] d) Preheating materials;

[0031] e) calcining the material;

[0032] f) firing materials in a kiln;

[0033] g) Cooling the product.

[0034] In step a), the coarse fraction is removed. An optional additional possibility is to remove the oversized fraction, for example particles with a particle size of more than 100 to 200 mm. For example, before step a), the raw material is crushed in a crusher, in which case the oversized fraction is preferably fed back to the crusher. This prevents the coarse fraction from containing oversized particles.

[0035] The heat treatment step b) in the shaft kiln allows a significantly coarser particle fraction to be heat treated. In addition, the coarser particle fraction contains calcium carbonate in particular. This makes the heat treatment simpler, so that the CO2 produced in this step can be removed, and the further equipment can be operated unchanged according to the prior art. In addition to the removal of CO2 in a relatively simple manner, the grindability of the material is also improved, which in turn reduces the energy consumption, especially for the largest particles, and further increases the efficiency of the entire process.

[0036] In step c), there are two options. First, the fine particle fraction is mixed with the heat-treated coarse particle fraction and then ground together. Second, the two particle fractions are ground separately and then mixed. The key point is that the two particle fractions are mixed again at the end and fed to the cement clinker operation in steps d) to g).

[0037] An important point is that during the calcination in step e), less energy is required since part (the coarse particle part) is already decarbonized. Therefore, the calciner requires less energy and fuel, and accordingly less CO2 is generated, which is released into the environment according to the prior art. Therefore, according to the process of the invention, part of the CO2 from the fuel is also generated in the shaft kiln and removed.

[0038] In a further embodiment of the invention, the sieving size in step a) is between 5 mm and 50 mm, for example 30 mm. For common raw materials, this sieving result can provide a good initial material particle size distribution for the shaft kiln. At the same time, it provides a possibility to transfer 20% to 40% of the formed carbon dioxide to the shaft kiln, so that this carbon dioxide can be easily removed without the need to modify the subsequent equipment, especially the kiln and calciner. Therefore, a considerable part of the CO2 emissions can be avoided relatively simply and quickly.

[0039] In a further embodiment of the present invention, the raw material is crushed before the screening in step a).

[0040] In a further embodiment of the invention, the heat treatment in step b) is carried out in alternating order in two shafts of the PFR shaft kiln. With regard to the realization of two shaft kilns, DE 10 2021 204 175 is hereby mentioned by way of example and in particular.

[0041] In a further embodiment of the invention, the coarse fraction after treatment in the shaft kiln has a carbon dioxide content of between 1% and 8% by mass, preferably between 3% and 5%. The carbon dioxide is present in the form of carbonates and is therefore chemically bound. This means that during further treatment in the calciner and kiln, the coarse fraction will release carbon dioxide from the carbonates. This range allows, on the one hand, a maximum removal of CO2, and, on the other hand, the residual content after actual treatment leads to a better quality product.

[0042] The device of the present invention is explained in more detail below by means of a working example shown in the drawings.

[0043] Figure 1 Schematic diagram of a device

[0044] Figure 1 A device is shown in schematic form. The raw materials for producing cement clinker are provided by a raw material supply facility 10. Such raw materials contain, in particular, calcium carbonate, for example. The raw materials are crushed in an optional crusher 20 and screened in a screening device 30. The coarse particle fraction - for example, all particles larger than 20 mm - is supplied to a shaft kiln 40 for heat treatment. The fine particle fraction from the screening device 30 is supplied to a mill 50 together with the heat-treated material from the shaft kiln 40, where they are mixed and ground together at the same time. The product ground in the mill 50 is preheated in a preheater 60, deacidified in a calciner 70, and finally fired in a kiln 80, in particular a rotary kiln. The fully fired cement clinker is cooled in a material cooler 90.

[0045] Importantly, compared to conventional plants, it may only be necessary to add a screening device 30 and in particular a shaft kiln 40. This means that the transformation is very simple and existing plants can be quickly and easily upgraded, thereby reducing at least part of the CO2 emissions.

[0046] Reference Mark

[0047] 10 Raw material supply facilities

[0048] 20 Crusher

[0049] 30 Screening device

[0050] 40 Vertical Kiln

[0051] 50 Mill

[0052] 60 Preheater

[0053] 70 Calcination furnace

[0054] 80 Kiln

[0055] 90 Material cooler.

Claims

1. A plant for producing cement clinker, the plant comprising a raw material supply facility (10), a mill (50), a preheater (60), a calciner (70), a kiln (80) and a material cooler (90), wherein a material flow is transmitted from the raw material supply facility (10) via the mill (50), the preheater (60), the calciner (70), the kiln (80) and the material cooler (90), wherein the material cooler (90) comprises a product outlet, characterized in that The apparatus comprises a screening device (30), the screening device (30) being connected to a raw material supply facility (10) to supply raw materials, the screening device (30) being configured to remove a coarse particle flow and a fine particle flow; the apparatus comprises a vertical kiln (40), the screening device (30) being connected to the vertical kiln (40) to transfer the coarse particle flow, the vertical kiln (40) being connected to the mill (50) to transfer the heat-treated raw materials, wherein the vertical kiln (40) is designed to operate with a gas containing at least 50% oxygen.

2. The device according to claim 1, characterized in that The shaft kiln (40) is designed to operate with a gas of at least 90% oxygen.

3. The device according to claim 1 or 2, characterized in that The screening device (30) is designed to separate particles between 5 mm and 50 mm.

4. A device as claimed in any preceding claim, characterised in that A CO2 deposition device is provided downstream of the vertical kiln (40).

5. A device as claimed in any preceding claim, characterised in that The plant comprises two shafts of a PFR shaft kiln (40).

6. A process for producing cement clinker, the process comprising the following steps: a) screening the raw materials into a coarse particle portion and a fine particle portion; b) thermally treating the coarse fraction in a shaft kiln (40) with a gas containing at least 50% oxygen; c) mixing the fine particle portion with the heat-treated coarse particle portion and then grinding, or separately grinding the fine particle portion and the heat-treated coarse particle portion and then mixing; d) Preheating materials; e) calcining the material; f) firing materials in a kiln; g) Cooling the product.

7. The process according to claim 6, characterized in that The sieving size in step a) is 5 mm to 50 mm.

8. The process according to claim 6 or 7, characterized in that In step a), the raw material is crushed before screening.

9. The process according to any one of claims 6 to 8, characterized in that The heat treatment in step b) is carried out in alternating order in the two shafts of the PFR (40).

10. The process according to any one of claims 6 to 9, characterized in that After treatment in the shaft kiln, the carbon dioxide content of the coarse fraction is between 1 and 8% by mass, preferably between 3 and 5%.

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