METHOD AND PLANT FOR THE PRODUCTION OF CEMENT CLINKER

Description

[0001] The invention relates to a process for the production of cement clinker comprising the following steps: Burning raw materials to produce cement clinker in a kiln, preheating the raw materials with flue gases from the kiln.

[0002] Furthermore, the invention relates to a plant for the production of cement clinker, comprising: a furnace for burning raw materials to produce cement clinker, a preheater for preheating the raw materials with flue gases from the furnace.

[0003] Cement clinker production, as described, for example, in AT 14170, generates large volumes of flue gas, which are contaminated with pollutants such as mercury and climate-damaging greenhouse gases such as carbon dioxide (CO2). Therefore, the operation of cement plants is subject to strict regulations. The emission of pollutants and climate-damaging greenhouse gases is to be reduced. Energy efficiency requirements are also continuously being increased. These goals are contrasted with the high investment costs associated with the post-treatment of large volumes of flue gas.

[0004] WO 2010 / 025739 A2 discloses a method for cooling hot gases using a condensation heat exchanger.

[0005] CN210855854 describes a cement plant that has a carbon capture unit.

[0006] The invention aims to simplify the post-treatment of flue gas streams from cement clinker production.

[0007] This problem is solved by a method according to claim 1 and a system according to claim 10. Preferred embodiments of the invention are specified in the dependent claims.

[0008] The inventive method for producing cement clinker includes the following step: dehumidifying and cooling the flue gases of the furnace by means of a condensation heat exchanger.

[0009] Accordingly, the cement clinker production plant has a dehumidification and cooling stage with a condensation heat exchanger for dehumidifying and cooling the flue gases from the furnace.

[0010] Thus, flue gases generated in the furnace, particularly a rotary kiln, are fed to the condensation heat exchanger, which reduces the moisture content of the flue gases and cools them. A cooling fluid, particularly cooling water, is supplied to the condensation heat exchanger, cooling the flue gases below the dew point, especially the water vapor dew point, so that the condensable substances, particularly water vapor, condense. For this purpose, the condensation heat exchanger has at least one heat exchange wall, particularly made of metal, through which heat exchange between the flue gases and the cooling fluid is effected. A shell-and-tube heat exchanger can be used as the heat exchanger. Depending on the design, the shell-and-tube heat exchanger can, for example, be divided into two chambers by a baffle plate.This allows one chamber to be cleaned during operation while the other chamber is used for heat exchange. Thus, the flue gases transfer not only sensible heat but also latent heat to the coolant, which is heated accordingly through the heat exchange. The heated coolant is then discharged from the condensation heat exchanger. Depending on the design, the heated coolant can be transported to a heat sink where its heat can be utilized. Condensate, particularly wastewater, produced during the flow through the condensation heat exchanger is discharged and can be treated in a water purification system. The key advantage of the process according to the invention is that the post-treatment of the flue gases after the condensation heat exchanger is simplified because the flue gas volume flows are significantly reduced by dehumidification.

[0011] In the prior art, see in particular EP 1 946 006 B1, the use of a condensing heat exchanger for a remote application in biomass combustion was described. In this prior art, the aim of the condensing heat exchanger is to improve efficiency. For this purpose, water is deliberately injected into the hot exhaust gas to raise its dew point before it enters the condensing heat exchanger.

[0012] In contrast, in one variant of the inventive method, no additional water is injected into the flue gas stream from the outside, but only the moisture already present in the flue gases of the furnace is used for condensation.

[0013] In another variant of the process according to the invention, the spraying of water achieves the separation of pollutants such as acid gases and dust. Furthermore, the higher water content in the exhaust gas can increase the (latent) heat energy transfer at the condensation heat exchanger. This can lead to better heat recovery from the flue gas.

[0014] For the purposes of this disclosure, directional terms such as "before", "after" refer to the direction of flow of the flue gases.

[0015] The water vapor dew point depends in particular on the composition of the flue gas. If the flue gases are cooled to a temperature of less than 50°C, especially less than 45°C, for example, less than essentially 40°C, by means of the condensing heat exchanger, the desired condensation of the flue gases in cement clinker production can be reliably achieved.

[0016] In a particularly preferred embodiment, the following process step is also carried out: cleaning the flue gases, for example with regenerative thermal oxidation (RTO) and / or with flue gas desulfurization (DeSOx) and / or denitrification (DeNOx), before dehumidifying and cooling the flue gases by means of the condensing heat exchanger. Various designs of cleaning stages for cleaning the furnace flue gases are known in the prior art. Thus, the flue gases can be cleaned before they are dehumidified by means of the condensing heat exchanger and thereby cooled from a temperature of 80°C to 300°C, in particular substantially 200°C, to a temperature of less than 50°C, in particular less than 45°C, for example less than 40°C.

[0017] The condensation heat exchanger is advantageously designed as a purification stage, which reduces residual amounts of acidic gases, especially sulfur dioxide (SO2) and / or hydrogen chloride (HCl) and / or heavy metals, especially mercury, in the flue gases after cleaning. Furthermore, odor reduction and plume removal from the flue gas can be achieved.

[0018] In another embodiment, the dehumidification and cooling of the flue gases by means of the condensing heat exchanger can take place between the preheating and cleaning stages. For this purpose, the condensing heat exchanger can be connected between a preheater for preheating the raw materials before they enter the furnace and a cleaning stage for cleaning the flue gases from the furnace, so that the flue gases are dehumidified and cooled by means of the condensing heat exchanger after the preheater, before they enter the cleaning stage. In a further embodiment, two condensing heat exchangers are provided, with one condensing heat exchanger arranged between the preheater and the cleaning stage, and the other condensing heat exchanger arranged after the cleaning stage.

[0019] In a preferred embodiment, the flue gases are recycled into the furnace after dehumidification and cooling via the condensing heat exchanger. A particular advantage is that the volume of the flue gas is reduced after condensation, which allows for a reduction in the dimensions of downstream system components such as filters, fans, mills, and, if necessary, a flue gas cleaning line.

[0020] According to the invention, after dehumidification and cooling by means of a condensing heat exchanger, the flue gases are fed to a Carbon Capture and Utilization (CCU) or Carbon Capture and Storage (CCS) unit for the separation of carbon dioxide. Dehumidification and cooling with the condensing heat exchanger offers the particular advantage that the flue gases have a minimal water content at low temperatures upon entering the CCU / CCS unit, thus ensuring sufficient sorption of the carbon dioxide within the CCU / CCS unit. Furthermore, the condensing heat exchanger can reduce the proportion of acidic gases and heavy metals to such an extent that the carbon dioxide (CO2) can be effectively separated by the CCU / CCS unit.

[0021] Upon entering the condensation heat exchanger, the flue gas from the furnace, preferably a rotary kiln, preferably has a carbon dioxide (CO2) content of 10 to 90% by volume (% v / v), particularly 15 to 30% v / v. Alternatively, especially in an oxyfuel process, the flue gas can have a CO2 content of more than 90% v / v.

[0022] In a first preferred embodiment, the CCU or CCS unit is configured for the absorption of carbon dioxide in a scrubbing liquid. Thus, the carbon dioxide can be absorbed by the scrubbing liquid. The scrubbing or absorption liquid can be an amine or aqueous solution of potassium hydroxide or amino acid salts, or an organic solvent such as methanol or polyglycol dialkyl ether. In a preferred embodiment, the CCU or CCS unit includes an amine scrubber. The amine scrubber preferably comprises an absorber and a desorber. An aqueous amine solution and the flue gases are introduced into the absorber. Energy in the form of heat is released through the chemical reaction of the absorbed CO₂ with the amine solution. The cleaned flue gas exits the absorber. The amine solution, loaded with CO₂ (and optionally with residues of other acidic gases), is fed into the desorber.In the desorber, the chemical equilibrium is reversed at high temperature through the application of thermal energy and low pressure, thus removing the bound CO2 from the amine solution. The CO2 can then be drawn off from the desorber. A condenser separates and recycles portions of the amine solution and water from the CO2 gas stream.

[0023] In another preferred embodiment, the CCU or CCS unit is configured for the adsorption of carbon dioxide onto a solid.

[0024] In one variant, the CCU / CCS unit is configured for a dry adsorption process using a solid sorbent, such as a zeolite, a functionalized polymer, or a metal-organic framework. In another variant, the CCU / CCS unit is configured for a cryogenic process in which the CO2 is separated by desublimation or liquefaction. In yet another variant, the CCU / CSU unit is configured for a membrane process for CO2 capture.

[0025] In the aforementioned embodiments, it is advantageous for the flue gases to be pre-cooled, for example, from 200 °C to a lower temperature of 40 °C. In cryogenic processes, the condensation heat exchanger can be the first of several cooling stages. Dehumidification prevents the formation of ice, which could clog the equipment. Pre-cooling the flue gas or exhaust gas stream is also advantageous when using temperature-sensitive membranes or sorbents. Generally, in sorption-based processes (whether absorption in scrubbing liquids or adsorption on solid sorbents), sorption works better at lower temperatures, as it is usually an exothermic process. Both absorption and adsorption processes can incorporate a desorber in which the CO2 is separated from the respective sorbent.The energy required for desorption can be provided in the form of heat.

[0026] The heat obtained during the dehumidification and cooling of the flue gases using the condensation heat exchanger is preferably used for the desorption of carbon dioxide.

[0027] To improve the energy balance, it is particularly advantageous if the heat recovered during the dehumidification and cooling of the flue gases via the condensing heat exchanger is used for the desorption of carbon dioxide, preferably in the amine scrubber. For example, the temperature of the heated cooling fluid from the condensing heat exchanger can be raised to the required temperature level for desorption using a heat pump.

[0028] The flue gas is fed to the condensing heat exchanger in the direction of flue gas flow after the preheater, particularly with a CO2 content of 10 to 90% v / v, especially 15 to 30% v / v, dehumidified and cooled by the condensing heat exchanger and subsequently fed to the CCU / CCS unit in the direction of flue gas flow.

[0029] Additionally or alternatively, heat obtained during the dehumidification and cooling of the flue gases using the condensation heat exchanger can be used to dry the raw materials and / or fuel of the furnace.

[0030] The plant for the production of cement clinker preferably has a flue gas cleaning stage, in particular an RTO and / or desulfurization stage, which is connected between the preheater and the dehumidification and cooling stage.

[0031] In a particularly preferred embodiment, the condensation heat exchanger has an inlet and outlet for a cooling liquid, wherein the outlet is preferably connected to a CCU / CCS unit, preferably to an amine scrubber, in particular to an evaporator of a desorber of the amine scrubber.

[0032] The invention is further explained below with reference to examples shown in the drawings.

[0033] Fig. 1 shows a functional diagram of a plant in which the flue gases are dehumidified and cooled after flue gas cleaning using a condensation heat exchanger, before the flue gases are used to dry the raw materials or fuel or are recycled in the rotary kiln.

[0034] Fig. 2 shows a functional diagram of an embodiment according to the invention, in which the dehumidified and cooled flue gases are fed to a CCU / CCS unit for the separation of the carbon dioxide.

[0035] Fig. 1 Figure 1 shows a plant 1 for the production of cement clinker, which is part of a cement plant. Plant 1 includes a kiln 2, in particular a rotary kiln, in which raw material, especially raw meal, is sintered into cement clinker. Furthermore, a preheater 3, in particular a preheating tower, preferably with a cyclone cascade with several cyclones connected in series (not shown), is provided. In the preheater 3, the raw material is preheated before entering the kiln 2 using flue gases from the kiln 2. The flue gases are drawn off at the top of the preheater 3. As is typical, plant 1 includes a cleaning stage 4, with which the flue gases drawn off from the preheater 3 can be cleaned. For example, an RTO (Regenerative Thermal Oxidation) stage can be provided as cleaning stage 4. The flue gases leave cleaning stage 4 at temperatures of, for example, approximately 200°C (see arrow 5).

[0036] In the embodiment shown, the flue gases are fed to a condensing heat exchanger 6 after cleaning stage 4. This heat exchanger has an inlet 7 for a cooling liquid, preferably with a temperature of less than 20°C, and an outlet 8 for the heated cooling liquid, preferably with a temperature of more than 40°C. Furthermore, the condensing heat exchanger 6 has a drain 9 for the condensate that forms during the condensation of the flue gases in the heat exchanger 6. The drain 9 can be connected to a water treatment stage. The flue gases coming from cleaning stage 4 are dehumidified and cooled by means of the condensing heat exchanger 6. Preferably, the temperature of the flue gases at the outlet of the condensing heat exchanger 6 is less than 40°C (see arrow 10).The heat content of the cleaned, dehumidified and cooled flue gases can be used with the help of a drying stage 11 to dry, for example, raw materials or fuel.

[0037] Additionally or alternatively, the flue gases can be recycled after the condensation heat exchanger 6 into the cement clinker production process, particularly into the rotary kiln (see the dashed line 12). This design is especially suitable for the so-called oxyfuel process, in which the flue gases are recirculated into the kiln and pure oxygen is simultaneously supplied to maintain combustion. This increases the CO2 content in the flue gases, thereby significantly enhancing the CO2 capture potential. The recirculation of the flue gases also serves to transport heat in the cement process.

[0038] In another embodiment, the condensation heat exchanger 6 can be connected between the preheater 3 and the flue gas cleaning stage 4, so that the flue gases are dehumidified and cooled after the preheater 3 by means of the condensation heat exchanger 6 before the flue gases enter the cleaning stage 4.

[0039] In another embodiment, two condensation heat exchangers 6 are provided, wherein one condensation heat exchanger 6 is located between preheater 3 and cleaning stage 4 and the other condensation heat exchanger 6 is located after cleaning stage 4.

[0040] Fig. 2Figure 1 shows an alternative embodiment in which the flue gases, after dehumidification and cooling by means of the condensing heat exchanger, are fed to a Carbon Capture and Utilization (CCU) or Carbon Capture and Storage (CCS) unit 13. This CCU / CCS unit 13 is configured to separate the carbon dioxide in the flue gases. In a preferred embodiment, the CCU / CCS unit 13 includes an amine scrubber. The amine scrubber comprises an absorber and a desorber, which can be connected to the line 8 for the heated cooling liquid of the condensing heat exchanger 6 in order to provide heat for the desorption of the carbon dioxide from the amine solution.

Claims

1. A method for producing cement clinker, comprising the steps of: burning raw materials to form cement clinker in a furnace (2), preheating the raw materials with flue gases from the furnace (2), characterised by dehumidifying and cooling flue gases from the furnace (2) by means of a condensing heat exchanger (6), wherein the flue gases, after dehumidifying and cooling by means of the condensing heat exchanger (6), are supplied to a Carbon Capture and Utilisation (CCU) or Carbon Capture and Storage (CCS) unit (13) for separating carbon dioxide.

2. The method according to claim 1, characterised in that the flue gases are cooled by means of the condensing heat exchanger (6) to a temperature of less than 50°C, in particular less than 45°C, for example less than substantially 40°C.

3. The method according to claim 1 or 2, characterised by cleaning the flue gases, for example with a Regenerative Thermal Oxidation (RTO) and / or with a flue gas desulphurisation (DeSOx) before dehumidifying and cooling the flue gases by means of the condensing heat exchanger (6).

4. The method according to on of the claims 1 to 3 , characterised in that the CCU or CCS unit (13) is configured for absorption of carbon dioxide in a scrubbing liquid.

5. The method according to one of the claims 1 to 4, characterised in that the CCU or CCS unit (13) comprises an amine scrubber.

6. The method according to one of the claims 1 to 3, characterised in that the CCU or CCS unit (13) is configured for adsorption of carbon dioxide on a solid.

7. The method according to any one of claims 1 to 6, characterised in that heat obtained during dehumidifying and cooling of the flue gases by means of the condensing heat exchanger (6) is used for the desorption of the carbon dioxide.

8. The method according to claim 7 with claim 5, characterised in that heat obtained during dehumidifying and cooling of the flue gases by means of the condensing heat exchanger (6) is used for desorption of the carbon dioxide in the amine scrubber.

9. The method according to any one of claims 1 to 8, characterised in that heat obtained during dehumidifying and cooling of the flue gases by means of the condensing heat exchanger (6) is used to dry the raw materials and / or a fuel of the furnace (2).

10. A plant (1) for producing cement clinker, comprising: a furnace (2) for burning raw materials to form cement clinker, a preheater (3) for preheating the raw materials with flue gases from the furnace (2), characterised by a dehumidifying and cooling stage comprising a condensing heat exchanger (6) for dehumidifying and cooling flue gases of the furnace (2), wherein in flowing direction of the flue gases, after the condensing heat exchanger (6), a Carbon Capture and Utilisation (CCU) or Carbon Capture and Storage (CCS) unit (13) for separating carbon dioxide is arranged.

11. The plant (1) for producing cement clinker according to claim 10, characterised by a flue gas cleanup stage (4), in particular an RTO and / or desulphurisation stage, which is interposed between the preheater and the dehumidifying and cooling stage.

12. The plant (1) for producing cement clinker according to claim 10 or 11, characterised in that the condensing heat exchanger (6) comprises a feed line (7) and a discharge line (8) for a cooling liquid, wherein the discharge line (8) is preferably connected to a CCU or CCS unit (13), preferably to an amine scrubber, in particular to an evaporator of a desorber of the amine scrubber.