Use of thermal energy generated in the cement clinker manufacturing process in the operation of the stage where carbon dioxide (CO2) is recovered from the exhaust gas of the manufacturing process.

Abstract

The thermal energy generated from the cement clinker manufacturing process is used to operate a stage in which carbon dioxide (CO2) is separated from the process exhaust gas.

Description

Technical Field

[0001] The present invention relates to the utilization of thermal energy generated from a cement clinker production process that produces exhaust gas rich in carbon dioxide (CO2).

Background Art

[0002] In recent years, the harmful effects of anthropogenic carbon dioxide (CO2) emissions on the Earth's climate have become clear. Industrial sectors, including cement clinker manufacturing plants, remain one of the main sources of these anthropogenic CO2 emissions. As demand for cement increases, there is an urgent need for solutions to reduce the environmental impact associated with carbon dioxide (CO2) emissions in this important industry.

[0003] One of the key processes in cement clinker production is the calcination of limestone, which leads to large volumes of carbon dioxide (CO2) emissions in addition to the CO2 emitted from the combustion of fossil fuels. This is because carbon dioxide is thermally separated from limestone (calcium carbonate, CaCO3) to form quicklime (CaO), which is then further sintered with silicate rock. To remove the carbon dioxide (CO2) generated during cement clinker production from the exhaust gas, it is necessary to operate a carbon dioxide separation device, which requires considerable energy regardless of whether the separation is chemical or physical.

[0004] Amine scrubbing, as an example of an energy-intensive carbon dioxide (CO2) separation device, is a particularly well-known and effective exhaust gas purification method in industrial processes where exhaust gas components that adversely affect the climate, such as carbon dioxide (CO2) and sulfur dioxide (SO2), are emitted. This is a chemical absorption method that uses an aqueous amine solution to remove these pollutants from the exhaust gas via absorption.

[0005] The principle of amine scrubbing as an energy-intensive carbon dioxide (CO2) separation device is based on the ability of amine compounds to react with and absorb acidic components of exhaust gases (in this case, carbon dioxide (CO2)). In a typical amine scrubbing plant, the exhaust gas passes through a scrubber or absorber, where it comes into contact with an aqueous amine solution. The amine reacts with the acidic components (in this case, carbon dioxide (CO2)) in the exhaust gas to form a compound in the form of ammonium carbonate, which remains dissolved in the aqueous solution. Aqueous solutions of alkanamines such as monoethanolamine (MEA), diethanolamine (DEA), methyldiethanolamine (MDEA), and diglycolamine (DGA) are commonly used as amines.

[0006] The amine solution containing the separated contaminants is sent to a regeneration or desorption unit, where the amine solution is heated and the combined gas is released. In this process, the dissolved ammonium carbonate is separated into carbon dioxide (CO2) and amine. The carbon dioxide (CO2) is discharged to the gas head, and the amine remains as an aqueous solution. This amine washing process allows for the separation of carbon dioxide (CO2) from the exhaust gas in a pure form by its function of selectively transporting carbon dioxide (CO2). The separated carbon dioxide (CO2) can be further treated or safely disposed of. The purified amine solution, from which carbon dioxide (CO2) has been separated, is returned to the scrubber or absorption unit to continue the purification process. Thus, the amine solution plays a role in selectively transporting carbon dioxide (CO2) and remains within the scrubbing process cycle.

[0007] Amine washing, an example of an energy-intensive carbon dioxide (CO2) separator, offers several advantages as an exhaust gas purification technology. It can remove both carbon dioxide (CO2) and sulfur dioxide (SO2) with high efficiency, contributing to the reduction of greenhouse gas emissions and air pollution. Furthermore, it can remove other pollutants such as nitrogen oxides (NOx) and volatile organic compounds (VOCs) to some extent. This process is relatively flexible and can adapt to various exhaust gas compositions and quantities. However, amine washing, as an example of an energy-intensive carbon dioxide (CO2) separator, has several challenges. Specifically, because it uses amines as a solvent, it requires a regeneration process that consumes a large amount of energy. The absorption process in amine washing is an exothermic process and proceeds naturally, but the subsequent separation of the exhaust gas (in this case, carbon dioxide (CO2)) from the amine used for washing is an endothermic process that requires energy input. To release the absorbed carbon dioxide (CO2) from the absorbent, a process called "desorption" is required, either by lowering the pressure above the absorbent or by raising the temperature of the absorbent. The required temperature varies depending on the type of absorbent. A typical value listed in the literature is 120°C. The required energy input also varies depending on the absorbent selected, ranging from 2.2 to 3.4 MJ / kgCO2. The average value measured at the Norsem cement plant test site in Brevik was 2.8 MJ / kgCO2. To release absorbed carbon dioxide (CO2) from the absorbent, it is necessary to either lower the pressure above the absorbent or raise its temperature.

[0008] In a typical cement clinker manufacturing plant, all separation processes to remove carbon dioxide (CO2) from exhaust gases consume a large amount of energy. Combining a cement clinker manufacturing plant with a carbon dioxide (CO2) recovery system is desirable. However, amine washing, an example of an energy-intensive carbon dioxide (CO2) recovery system, consumes a very large amount of energy, making it, like all other carbon dioxide (CO2) recovery processes, unattractive in cement clinker manufacturing both energetically and economically.

[0009] As a reference for estimating the amount of energy required for carbon dioxide (CO2) capture, an example of a standard cement clinker manufacturing plant with a daily clinker production capacity of 3,000 tons is shown. This plant has five heat exchangers, an in-line firing furnace, and an efficiency of 74% (@0.8Nm). 2 It is equipped with a grate cooler (recovered air) of 3,134 kJ / kgKli. Here, it is assumed that the basic design of a typical cement clinker manufacturing plant is known. Such a plant is equipped with a so-called tertiary air duct, which sends air from the grate cooler inlet to the firing furnace, significantly heating the cooling air because the cement clinker to be cooled is still very hot, and recovers heat from the production process. In the reference plant, coal is used as fuel (Hu = 25,121 kJ / kgBr), and the total heat requirement is 3,134 kJ / kgKli.

[0010] A heat balance analysis of this plant revealed that the largest source of heat loss is the exhaust gases from the preheater and cooler. These two exhaust gases account for approximately 70% of the plant's heat loss, totaling 1,262 kJ / kgKli. CO2 emissions are 0.86 kgCO2 / kgKli, and this amount of heat provides 39% of the energy required to operate the amine scrubbing system in direct operation without the raw material mill, and 28% in combined operation with the raw material mill. The remaining heat required to operate the amine washing system must be supplied by an additional high-temperature gas generator or electric heater. [Overview of the Initiative] [Problems that the invention aims to solve]

[0011] The objective of this invention is to combine a cement clinker manufacturing process with a carbon dioxide (CO2) separation device to create an energy- and economically attractive system. [Means for solving the problem]

[0012] The above problem is solved by a process having the features of claim 1 of the present invention. Further advantageous embodiments are described in the dependent claims of claim 1.

[0013] The solution to the problems of the present invention can, in principle, be realized by four different designs (configurations) of a cement clinker manufacturing plant.

[0014] In the first embodiment of the present invention's process, the cement plant is unchanged from the prior art except for the tertiary air line. In this invention, a heat exchanger is installed in the tertiary air line, and the heat from the tertiary air is utilized in an amine scrubber. The cooled tertiary air is sent to the calcination furnace as cooled combustion air. This improved system has been shown to increase heat consumption by 21% compared to the standard plant, to 3782 kJ / kgKli. This increase in heat consumption is due to the increased amount of fuel supplied to the calcination furnace to maintain the calcination temperature. The energy extracted from the tertiary air line can absorb 52% of CO2 emissions when operated in conjunction with a raw material mill, and 62% when operated directly. The absorption rate of carbon dioxide (CO2) is determined by the amount of heat available for the desorption of carbon dioxide oxides (CO2). In this case, the available heat is insufficient to completely desorb the cleaning solution, so the carbon dioxide (CO2) bound as ammonium compounds is returned to the scrubber (absorption device).

[0015] A second embodiment of the present invention further improves upon the system of the first embodiment, enabling higher heat extraction. To this end, the number of heat exchange cyclones in the cyclone heat exchanger is reduced from five to three. This improvement increases the temperature of the exhaust gas discharged from the system. While the increased exhaust gas temperature reduces the efficiency of the cement plant in terms of energy input per kilogram of cement clinker, it increases the energy available for regenerating the absorption tower.

[0016] By reducing the number of heat exchange cyclones used in the preheating stage, the exhaust gas outlet temperature rises to approximately 480°C. In this concept, the system's heat demand increases by 36% compared to the standard plant, reaching 4255 kJ / kgKli. A downstream scrubber utilizing this recovered exhaust gas energy can absorb 68% of CO2 emissions when operating in conjunction with the raw material mill, and 77% of CO2 emissions when operating directly.

[0017] In a third embodiment of the present invention, the cement clinker manufacturing plant does not use a preheater and calcination furnace, but instead operates using a fluidized bed reactor. The raw materials are heated and calcined in the fluidized bed reactor, and dust and exhaust gases are separated in a connected single cyclone. Downstream of the cyclone, both the raw materials and exhaust gases reach temperatures of up to 850°C. In this process configuration, the overall heat demand of the plant was calculated to increase by 60% compared to a standard plant, reaching 5000 kJ / kgKli. By installing a scrubber that utilizes the waste heat of this plant, 89% of CO2 emissions can be absorbed in combined operation with the raw material mill, and 98% in direct operation.

[0018] A fourth embodiment of the present invention is a further modification of the third embodiment, wherein in addition to operating a fluidized bed reactor, a heat exchanger is installed in the tertiary air line. In this embodiment of the present invention, the total heat demand of the cement clinker manufacturing plant increases by 72% compared to the standard plant, to 5388 kJ / kgKli. By using a scrubber that utilizes the waste heat of this plant, 100% of CO2 emissions can be absorbed when operated in conjunction with the raw material mill, and theoretically 108% of CO2 emissions can be absorbed when operated directly. This means that the scrubbing fluid in the desorber needs to be cooled again.

[0019] The process described here can be modified in various ways. Various substances can also be used as absorbents. Suitable absorbents include aqueous solutions of alkanolamines such as monoethanolamine (MEA) and diethanolamine (DEA), alkylalkanolamines such as methyldiethanolamine (MDEA), and / or diglycolamines (DGA). Furthermore, ammonia or ammonia solution in an organic solvent (i.e., ammonia instead of amines) can also be used. Liquid ammonia can also be used at low temperatures, i.e., below 33°C. If the size is appropriate, carbonic anhydrase can be used as a biological catalyst to enhance absorption by the absorbent.

[0020] The present invention will be described in more detail with reference to the following drawings. [Brief explanation of the drawing]

[0021] [Figure 1] A diagram of a typical conventional cement clinker manufacturing plant, shown as a reference plant. [Figure 2] A diagram illustrating the first individual measure of the present invention for extracting heat from the cement clinker manufacturing process. [Figure 3] A diagram illustrating a second individual measure of the present invention for extracting heat from the cement clinker manufacturing process. [Figure 4] A diagram illustrating a third individual measure of the present invention for extracting heat from the cement clinker manufacturing process. [Modes for carrying out the invention]

[0022] [Figure 1] shows a general cement clinker production plant 100 based on the prior art as a reference plant. This figure does not show material flows such as the flow from raw materials to finished cement clinker, or the gas flows from cooling gas and primary air to exhaust gas. For these details, reference should be made to relevant documents. A feature of this type of plant resides in a cyclone heat exchanger 110 equipped with five heat exchange cyclones 111, 112, 113, 114, and 115. The raw material passing through the five heat exchange cyclones 111, 112, 113, 114 and 115 is heated to just below the calcination temperature. Furthermore, this type of cement clinker production plant 100 includes a calciner 120. In this calciner 120, the preheated raw material is calcined, that is, converted to quicklime (CaO) by thermal removal of carbon dioxide (CO₂). The calciner is further followed by a rotary kiln 130 in which sintering is performed at high temperature, and a clinker cooler 140 for cooling the calcined cement clinker is arranged downstream of the calciner. The very high-temperature cooling air generated during cooling of the cement clinker is returned to the calciner 120 via the tertiary air supply 150, to resupply thermal energy to the process. Although various designs are adopted around the world, the energy conditions in a typical cement clinker production plant 100 are substantially equivalent. For example, since the performance of heat exchange cyclones is known, as a general rule five heat exchange cyclones 111, 112, 113, 114 and 115 are used, except when a different number of heat exchange cyclones is required for other plant types with specific process steps. The illustrated vertical mill 160 for raw material milling is often included in the energy analysis of the energy amount required per 1 kg of cement clinker produced, in order to evaluate the efficiency of the entire plant as an example of a raw material mill.

[0023] [Fig. 2] shows the first individual measure for extracting heat from the cement clinker manufacturing process according to the present invention. In the present invention, in order to supply heat to the scrubber 200 consisting of an absorber 201 and a desorber 202, heat is extracted from tertiary air using a heat exchanger 210 installed in the tertiary air duct 150. This heat is used to heat the desorber 202 in the scrubber 200. The exhaust gas discharged from the cyclone heat exchanger 110 passes through the scrubber 200 and is separated into carbon dioxide (CO2) and the remaining exhaust gas. Tests have shown that, compared to the reference plant shown in [Fig. 1], the total heat consumption of the cement clinker manufacturing plant modified in this way increases by 21% to 3782 kJ / kgKli. This increase in heat consumption is due to the increased required fuel supply to the calcining furnace, and cooler tertiary air is supplied to the calcining furnace to maintain the calcining temperature. The energy extracted from the tertiary air line can absorb 52% of CO2 emissions in combined operation with the raw material mill, and can absorb 62% in direct operation. is.

[0024] [Fig. 3] shows the second individual measure for extracting heat from the cement clinker manufacturing process. In this improved plant, only three heat exchange cyclones 111, 112, 113 are used in the cyclone heat exchanger 110 for preheating raw meal. Due to the small number of heat exchange cyclones, the cooling effect that the exhaust gas receives from the raw meal is reduced, and the exhaust gas outlet temperature rises to about 480°C. This exhaust gas is cooled by the heat exchanger 211. The heat recovered in this process is used in the desorber 202, and the cooled exhaust gas is sent to the absorber 201. It is also possible to utilize the waste heat recovered from the exhaust gas temperature of the desorber 202 when this individual measure is implemented.

[0025] When this individual measure is used in conjunction with the heat extraction measures from the cement clinker manufacturing process shown in Figure 1, the plant's heat demand increases by 36% compared to the standard plant, reaching 4255 kJ / kgKli. The downstream scrubber 200, which utilizes the recovered exhaust gas energy, can absorb 68% of CO2 emissions when operated in conjunction with the raw material mill, and 77% of CO2 emissions when operated directly.

[0026] Figure 4 shows a third individual measure for heat extraction from the cement clinker manufacturing process. In this modified plant, the cyclone heat exchanger 110 and calcination furnace 120 are replaced with a fluidized bed reactor 121. Instead of preheating the raw materials before calcination, cold raw materials are fed into the fluidized bed reactor 121 and heated and calcined in a single step. The temperature of both the raw materials and exhaust gas after passing through the cyclone of the fluidized bed reactor 121 reaches a maximum of 850°C. With this process configuration, the overall heat demand of the plant is calculated to increase by 60% compared to the standard plant, reaching 5000 kJ / kgKli. By utilizing this waste heat in the scrubber 200, 89% of CO2 emissions can be absorbed when operated in conjunction with the raw material mill 160, and 98% of CO2 emissions can be absorbed when operated directly. It is also possible to utilize the waste heat recovered from the exhaust gas temperature when this individual measure is implemented in the desorber 202.

[0027] When this measure is used in conjunction with the measure shown in Figure 2, the total heat demand of the cement clinker manufacturing plant increases by 72% compared to the standard plant, reaching 5388 kJ / kgKli. By utilizing the waste heat of this system with the Scrubber 200, 100% of CO2 emissions can be absorbed when operating in conjunction with the raw material mill, and theoretically 108% of CO2 emissions can be absorbed when operating directly. This means that the scrubbing fluid needs to be cooled again in the desorber. [Explanation of Symbols]

[0028] 100 plants 110 Cyclone heat exchanger 111 Heat exchanger cyclone 112 Heat exchanger cyclone 113 Heat exchanger cyclone 114 Heat exchanger cyclone 115 Heat exchanger cyclone 120 firing furnaces 121 Fluidized Bed Reactor 130 Rotary Kiln 140 Clinker cooling system 150 Tertiary air duct 160 Vertical Mill 200 Scrubber 201 Absorption device 202 Detachable device 210 Heat exchanger 211 Heat exchanger 212 Heat exchanger

Claims

1. Carbon dioxide (CO2) 2 The thermal energy obtained from the cement clinker manufacturing process, which generates exhaust gas containing a large amount of carbon dioxide (CO2) from the exhaust gas of the above process, 2 Use in the operation stage where ) is separated.

2. The cement clinker manufacturing process consists of the following steps: - A process of preheating raw materials in a heat exchanger. - The process of firing the raw materials during the firing stage. - A process in which the fired raw materials are sintered during the sintering stage. - A process of cooling the sintered cement clinker during the cooling stage. The use of thermal energy according to claim 1, characterized in that thermal energy is recovered from the cooling stage and used in the above process.

3. Thermal energy, a) A heat exchanger located in a tertiary air line that transports thermal energy from the cooling stage to the firing stage, and / or b) A heat exchanger placed at the outlet of an exhaust gas containing a large amount of carbon dioxide, The use of thermal energy according to claim 2, characterized by extraction by means of...

4. The following steps - The process of compressing exhaust gases, - A step of introducing compressed exhaust gas into the absorber (201) which acts as a reactor for the scrubber (200), - Steps to inject cleaning solution into the absorber (201), - A process of transporting the scrubbing liquid from the absorber (201) to the desorber (202), which acts as another reactor for the scrubber. - A step of heating the scrubbing fluid in the detacher (202), - Carbon dioxide (CO2) released by heating the scrubbing solution 2 ) process of discharge - A step of returning the scrubbing fluid from the desorber (202) to the absorber (201), The use of thermal energy according to claim 2 or 3, characterized in that the delinker (202) is heated with waste heat from a cement clinker manufacturing plant, including the use of thermal energy according to claim 2 or 3.

5. The use of thermal energy according to claim 4, characterized in that the desorber (202) is heated with heat extracted from a cement clinker manufacturing plant via a heat exchanger (210) and a tertiary air line (150).

6. The use of thermal energy according to claim 5, characterized in that the cement clinker manufacturing plant achieves an exhaust gas temperature sufficient for the complete regeneration of the delinker by eliminating the heat exchange cyclones (114, 115), the number of heat exchange cyclones (114, 115) is from one to four, and the exhaust gas temperature is preferably set to 360°C to 850°C by selecting the number of heat exchange cyclones (111, 112, 113, 114), thereby additionally heating the delinker (202) using heat extracted from the exhaust gas line of the cement clinker manufacturing plant via the heat exchanger (211).

7. The use of thermal energy according to claim 4 or 5, characterized in that the cement clinker manufacturing plant does not have a firing furnace (120) and a heat exchanger (110), and uses a fluidized bed reactor (121) to exhibit an exhaust gas temperature exceeding 800°C, wherein the desorber (202) is heated by heat extracted from the exhaust gas line of the cement clinker manufacturing plant via a heat exchanger (212).

8. The use of thermal energy according to any one of claims 4 to 7, characterized in that an alkanolamine such as monoethanolamine (MEA), diethanolamine (DEA), or an aqueous solution of alkyl alkanolamine (methyldiethanolamine (MDEA) and / or diglycolamine (DGA)) is used as the absorbent in the absorber (201), or ammonia or a solution of ammonia in an organic solvent or ammonia at a low temperature, i.e., below 33°C is used as the absorbent in the absorber (201), and / or carbonic anhydrase is used as a catalyst to promote the absorption of the absorbent in the absorber (201).

9. The use of thermal energy according to any one of claims 4 to 8, characterized in that a tertiary air line (150) for guiding high-temperature exhaust gas from a clinker cooler (140) to a firing furnace (120) has a heat exchanger (210) for transporting waste heat and heating a decoupler (202).

10. A cement manufacturing plant for implementing the use described in any one of claims 4 to 8, characterized in that the cyclone heat exchanger (110) of the cement clinker manufacturing plant has three heat exchange cyclones (111, 112, 113), thereby increasing the exhaust gas temperature compared to when five heat exchange cyclones (111, 112, 113, 114, 115) are used, and the heat exchanger (211) uses waste heat from the exhaust gas to heat the decoupler (202).

11. A tertiary air line (150) for sending high-temperature exhaust gas from the clinker cooler (140) to the firing furnace (120) has a heat exchanger (210) that transfers waste heat to heat the decoupler (202). A cement manufacturing plant for carrying out the use according to any one of claims 4 to 8, characterized in that the cyclone heat exchanger (110) of the cement clinker manufacturing plant has three heat exchange cyclones (111, 112, 113), thereby increasing the exhaust gas temperature compared to when five heat exchange cyclones (111, 112, 113, 114, 115) are used, wherein the heat exchanger (211) transfers waste heat from the exhaust gas to heat the decoupler (202).

12. A cement manufacturing plant for carrying out the use according to any one of claims 4 to 8, characterized in that a fluidized bed reactor (121) is provided instead of a cyclone heat exchanger (110) and a calcination furnace (120), thereby increasing the exhaust gas temperature, the heat exchanger (212) transfers waste heat from the exhaust gas to heat the decoccone (202).

13. A cement manufacturing plant for carrying out the use according to any one of claims 4 to 8, characterized in that a tertiary air line (150) for leading high-temperature exhaust gas from a clinker cooler (140) to a firing furnace (120) has a heat exchanger (210) that transports waste heat to heat a desorber (202), and instead of a cyclone heat exchanger (110) and a firing furnace (120), a fluidized bed reactor (121) is provided, thereby increasing the exhaust gas temperature, and a heat exchanger (212) transports waste heat from the exhaust gas to heat the desorber (202).

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