Calcined cement clinker-based method and system for obtaining high-concentration carbon dioxide flue gas

Abstract

The present disclosure provides a calcined cement clinker-based method and system for obtaining a high-concentration carbon dioxide flue gas. The system comprises: a rotary kiln, provided with a smoke chamber and a kiln head cover, the rotary kiln surrounding an electromagnetic induction apparatus along the length direction, and a pressure sensor and a gas analyzer being disposed in the kiln head cover; an air cooling apparatus, configured to cool, by using air, a clinker produced by heating and calcining a raw material in the rotary kiln by means of the electromagnetic induction apparatus; a first heat exchange apparatus, configured to perform heat exchange between the raw material and a flue gas produced by calcining the raw material in the rotary kiln; a second heat exchange apparatus, configured to perform heat exchange between the raw material and the air after the heat exchange; a first fan being mounted in a flue gas pipeline and configured to discharge the flue gas after the heat exchange; a second fan being mounted in an air pipeline and configured to discharge the air after secondary heat exchange; and a control apparatus, configured to regulate rotation speeds of the first fan and the second fan, so that the carbon dioxide concentration is reduced to a threshold and the pressure value is reduced to a preset range. The system provided in the present disclosure can obtain a high-concentration carbon dioxide flue gas.

Description

Method and system for obtaining high-concentration carbon dioxide flue gas based on calcining cement clinker

[0001] Related applications

[0002] This disclosure claims priority to a Chinese patent application filed with the Patent Office of China on September 15, 2023, with application number CN202311194724.X and invention name “Method and system for obtaining high-concentration carbon dioxide flue gas based on calcining cement clinker”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present disclosure relates to the technical field of cement calcination, and in particular to a method and system for obtaining high-concentration carbon dioxide flue gas by calcining cement clinker. Background Art

[0004] Carbon dioxide capture systems are used to remove carbon dioxide from gas streams or separate it as a gaseous product. Capture is the first step in carbon capture and storage (CCS). Carbon dioxide needs to be present at a high purity during transportation and storage. However, in most cases, the concentration of carbon dioxide in industrial exhaust gases does not meet this requirement, so carbon dioxide must be separated from the exhaust gases. This process is called carbon dioxide capture. Carbon dioxide capture systems can be divided into several categories, including chemical absorption, physical absorption, physical adsorption, membrane separation, and cryogenic separation. When applied, the capture method and equipment must be selected based on the actual characteristics and parameters of the carbon dioxide emission source.

[0005] In the process of implementing the present disclosure, the inventors discovered that the prior art has at least the following problems:

[0006] Conventional rotary kiln cement calcination processes require fuel combustion, with air as the combustion medium. The resulting flue gas has a low CO2 concentration, typically between 18-25%. The investment and operating costs of a CO2 capture system are significantly affected by CO2 concentration. The low CO2 concentration produced by conventional rotary kiln cement calcination processes will significantly increase the investment and operating costs of a CO2 capture system.

[0007] Therefore, a method and system for obtaining high-concentration carbon dioxide flue gas based on calcining cement clinker is needed to at least partially solve the above technical problems.

[0008] Summary of the Invention

[0009] The embodiments of the present disclosure provide a method and system for obtaining high-concentration carbon dioxide flue gas based on calcining cement clinker, which can obtain high-concentration carbon dioxide flue gas with low energy consumption.

[0010] In a first aspect, the present disclosure provides a system for producing high-concentration carbon dioxide flue gas by calcining cement clinker, comprising: a rotary kiln, wherein a smoke chamber and a kiln head hood are respectively provided at the rear and head of the rotary kiln, and an electromagnetic induction device is surrounded along the length of the rotary kiln; a pressure sensor and a gas analyzer are provided in the kiln head hood;

[0011] an air cooling device, the air cooling device being connected to the kiln head cover and being used to cool the clinker produced by the rotary kiln heating and calcining the raw material via the electromagnetic induction device using air, the kiln head cover being provided with a hot air duct for conducting the air after heat exchange;

[0012] a first heat exchange device connected to the smoke chamber, for exchanging heat between raw meal and smoke generated by calcining the raw meal in the rotary kiln, the first heat exchange device comprising a first raw meal inlet for introducing raw meal and a first raw meal outlet for leading the raw meal after heat exchange to the smoke chamber;

[0013] a second heat exchange device connected to the smoke chamber and the hot air duct, respectively, for exchanging heat between the raw meal and the heat-exchanged air, the second heat exchange device comprising a second raw meal inlet for introducing the raw meal and a second raw meal outlet for leading the heat-exchanged raw meal out to the smoke chamber;

[0014] a flue gas duct connected to the first heat exchange device, wherein the flue gas duct is equipped with a first fan for discharging the flue gas after heat exchange;

[0015] an air duct connected to the second heat exchange device, wherein the air duct is equipped with a second fan for discharging the air after the secondary heat exchange;

[0016] a control device, the control device being respectively connected to the pressure sensor, the gas analyzer, the first fan, and the second fan, the control device being configured to: when the carbon dioxide concentration monitored by the gas analyzer is greater than a threshold value, control the rotational speed of the first fan to gradually increase until it remains at a rotational speed that reduces the carbon dioxide concentration to the threshold value, during which the pressure value monitored by the pressure sensor is within a preset range; if the pressure value monitored by the pressure sensor is greater than an upper limit of the preset range during the process of controlling the rotational speed of the first fan to gradually increase, control the rotational speed of the second fan to gradually decrease, at which point the rotational speed of the first fan remains unchanged, until the first and second fans remain at rotational speeds that reduce the carbon dioxide concentration to the threshold value and the pressure value to within the preset range; if the pressure value monitored by the pressure sensor is less than a lower limit of the preset range during the process of controlling the rotational speed of the second fan to gradually decrease, at which point the carbon dioxide concentration still does not reduce to the threshold value, control the rotational speed of the first fan to continue to gradually increase, at which point the rotational speed of the second fan remains unchanged; and repeat the above process until the first and second fans remain at rotational speeds that reduce the carbon dioxide concentration to the threshold value and the pressure value to within the preset range.

[0017] According to the system disclosed in the present invention, the raw material in the rotary kiln is heated and calcined by an electromagnetic induction device, and the raw material decomposes to release carbon dioxide gas. Compared with the traditional method of burning fuel, no air is introduced, and the carbon dioxide concentration in the generated carbon dioxide flue gas is high; at the same time, the rotation speed of the first fan and the second fan is regulated by the control device to control the carbon dioxide concentration to a threshold value and the pressure value to a preset range value, so that the carbon dioxide flue gas and the air after heat exchange each take their own paths and do not mix, further ensuring a high concentration of carbon dioxide; in addition, the entire system uses air to cool the clinker, and uses the carbon dioxide flue gas and the air after heat exchange to preheat the raw material, so that energy is reused and energy consumption is low.

[0018] Optionally, the first heat exchange device includes a plurality of cyclones arranged from top to bottom, the bottom material outlet of the lowest cyclone is connected to the smoke chamber, the gas inlet of the lowest cyclone is connected to the smoke chamber, and the top gas outlet of the highest cyclone is connected to the smoke duct; wherein the gas outlet of the lower cyclone is connected to the upper cyclone via a connecting duct, and the bottom material outlet of the upper cyclone is connected to the lower connecting duct;

[0019] The raw material is fed into the connecting pipe located at the top.

[0020] Optionally, the second heat exchange device also includes a plurality of cyclones arranged from top to bottom, the bottom material outlet of the lowest cyclone is connected to the smoke chamber, the gas inlet of the lowest cyclone is connected to the hot air duct, and the top gas outlet of the highest cyclone is connected to the air duct; wherein the gas outlet of the lower cyclone is connected to the upper cyclone through a connecting duct, and the bottom material outlet of the upper cyclone is connected to the lower connecting duct;

[0021] The raw material is fed into the connecting pipe located at the top.

[0022] Optionally, the air cooling device includes a grate cooler, and a blower for introducing air is provided at the bottom of the grate cooler.

[0023] Optionally, the ratio of raw materials fed into the first heat exchange device and the second heat exchange device is 1:(2-5).

[0024] Optionally, the flue gas discharged from the flue gas duct is further processed by a dust collector, and the processed flue gas can be connected to a carbon dioxide capture system.

[0025] Optionally, the flue gas duct and / or the air duct is further connected to a waste heat boiler.

[0026] In a second aspect, the present disclosure further provides a method for obtaining high-concentration carbon dioxide flue gas by calcining cement clinker. The system based on the above technical solution specifically comprises the following steps:

[0027] The raw material is heated and decomposed in a rotary kiln equipped with an electromagnetic induction device to produce carbon dioxide gas, while calcining it into clinker;

[0028] The flue gas containing the carbon dioxide gas generated by decomposition enters the first heat exchange device through the smoke chamber, and the clinker enters the air cooling device through the kiln head cover to exchange heat with the air for cooling, and the air after heat exchange enters the second heat exchange device;

[0029] Before entering the rotary kiln, the raw material is respectively put into the first heat exchange device and the second heat exchange device to exchange heat with the flue gas and air. After the heat exchange, it enters the rotary kiln through the smoke chamber for calcination. The flue gas and air after heat exchange are discharged through the flue gas duct and the air duct respectively. The flue gas discharged through the flue gas duct is a high-concentration carbon dioxide flue gas with a carbon dioxide concentration greater than 80%.

[0030] In which, when the carbon dioxide concentration monitored by the gas analyzer is greater than the threshold value, the first fan gradually increases the speed until it stays at the speed when the carbon dioxide concentration drops to the threshold value, and the pressure value monitored by the pressure sensor is always within the preset range value during this period; in the above process, if the pressure value monitored by the pressure sensor is greater than the upper limit of the preset range value but the carbon dioxide concentration has not dropped to the threshold value during the process of gradually increasing the speed of the first fan, the second fan begins to gradually reduce the speed, while the first fan maintains the speed unchanged until the first fan and the second fan respectively stay at the speed when the carbon dioxide concentration drops to the threshold value and the pressure value drops to the preset range value; in the above process, if the carbon dioxide concentration still does not drop to the threshold value when the pressure value is less than the lower limit of the preset range value during the process of gradually reducing the speed of the second fan, the first fan continues to gradually increase the speed, while the second fan maintains the speed unchanged; repeat the above steps until the first fan and the second fan stay at the speed when the carbon dioxide concentration drops to the threshold value and the pressure value drops to the preset range value.

[0031] By utilizing the technical solution according to the embodiments of the present disclosure, the beneficial effects that can be obtained are at least:

[0032] 1. The raw material in the rotary kiln is heated and calcined by an electromagnetic induction device, and the raw material decomposes to release carbon dioxide gas. Compared with the traditional fuel combustion method, no air is introduced, no flue gas is generated from the burning fuel, the amount of waste gas is greatly reduced, and the carbon dioxide concentration in the generated carbon dioxide flue gas is high;

[0033] 2. By means of the control device, pressure sensor and gas analyzer, the rotation speed of the first fan and the second fan are regulated by the control device, and the carbon dioxide concentration is controlled to drop to a threshold value and the pressure value to drop to a preset range. The purpose is to prevent the carbon dioxide gas released by the decomposition of the raw material in the rotary kiln from mixing with the air after heat exchange, thereby further ensuring a high concentration of carbon dioxide.

[0034] Additional advantages, objects, and features of the present disclosure will be described in part in the following description and will become apparent to those skilled in the art upon study of the following or may be learned from practice of the present disclosure. The objects and other advantages of the present disclosure may be achieved and obtained by the structures specifically pointed out in the description and drawings.

[0035] Those skilled in the art will understand that the purposes and advantages that can be achieved by the present disclosure are not limited to the above specific descriptions, and the above and other purposes that can be achieved by the present disclosure will be more clearly understood from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The drawings described herein are intended to provide a further understanding of the present disclosure, constitute a part of the present disclosure, and do not constitute a limitation of the present disclosure. The components in the drawings are not drawn to scale, but are only for the purpose of illustrating the principles of the present disclosure. To facilitate the illustration and description of some parts of the present disclosure, the corresponding parts in the drawings may be enlarged, that is, they may be larger than other parts in the exemplary devices actually manufactured according to the present disclosure. In the drawings:

[0037] FIG1 is an overall schematic diagram of a system for obtaining high-concentration carbon dioxide flue gas by calcining cement clinker according to an embodiment of the present disclosure; and

[0038] 2 is a schematic diagram showing the connections between a control device and a pressure sensor, a gas analyzer, a first blower, and a second blower in a system for obtaining high-concentration carbon dioxide flue gas based on calcining cement clinker according to an embodiment of the present disclosure.

[0039] Explanation of the accompanying reference numerals: 100, system; 110, rotary kiln; 111, smoke chamber; 112, kiln head hood; 113, electromagnetic induction device; 114, pressure sensor; 115, gas analyzer; 120, grate cooler; 121, blower; 122, hot air duct; 130, first heat exchange device; 140, second heat exchange device; 150, flue gas duct; 151, first fan; 160, air duct; 161, second fan; 170, control device; 180, cyclone; 181, connecting pipe; 190, waste heat boiler; 191, dust collector; 192, carbon dioxide capture system. DETAILED DESCRIPTION

[0040] The purposes and functions of the present disclosure, as well as methods for achieving these purposes and functions, will be clarified by reference to exemplary embodiments. However, the present disclosure is not limited to the exemplary embodiments disclosed below; it can be implemented in various forms. The essence of the description is merely to help those skilled in the relevant art to comprehensively understand the specific details of the present disclosure.

[0041] It should be noted that the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the exemplary embodiments according to the present disclosure. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should also be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or combinations thereof.

[0042] Ordinal numbers such as “first” and “second” cited in the present disclosure are merely identifiers and do not have any other meanings, such as a specific order, etc. Moreover, for example, the term “first component” itself does not imply the existence of a “second component”, and the term “second component” itself does not imply the existence of a “first component”.

[0043] It should be noted that the terms "upper", "lower", "front", "back", "left", "right", "inside", "outside" and similar expressions used in this document are for illustrative purposes only and are not limiting.

[0044] In a first aspect, the present disclosure provides a system 100 for obtaining high-concentration carbon dioxide flue gas based on calcining cement clinker, which is applied in the field of cement calcining technology to solve the problem of low carbon dioxide concentration in flue gas generated by existing cement calcining processes.

[0045] As shown in Figures 1 and 2, in a preferred embodiment, system 100 includes a rotary kiln 110, an air cooling device, a first heat exchanger 130, a second heat exchanger 140, a flue gas duct 150, an air duct 160, and a control device 170. The rotary kiln 110 is used to heat and calcine raw meal. The air cooling device is used to air-cool the clinker produced by the calcined raw meal. The first heat exchanger 130 is used to preheat the raw meal fed into the rotary kiln 110 using flue gas. The second heat exchanger 140 is used to preheat the raw meal fed into the rotary kiln 110 using air. The flue gas duct 150 is used to discharge the flue gas generated by the rotary kiln 110, producing a high-concentration carbon dioxide flue gas. The air duct 160 is used to discharge the heat-exchanged air. The control device 170 is used to control the pressure balance within the kiln hood 112 to prevent the carbon dioxide flue gas generated within the rotary kiln 110 from mixing with the air passing through the kiln hood 112, thereby maintaining a high concentration of carbon dioxide in the flue gas.

[0046] Specifically, a smoke chamber 111 and a kiln head hood 112 are provided at the rear and front ends of the rotary kiln 110, respectively. Raw material enters the rotary kiln 110 through the smoke chamber 111. Flue gas is discharged through the smoke chamber 111. Clinker is discharged through the kiln head hood 112. The rotary kiln 110 is a rotatable cylindrical structure. It may include an inlet section, a firing section, and a cooling section. An electromagnetic induction device 113, such as an electromagnetic induction coil, surrounds the rotary kiln 110 along its length. High-frequency alternating current passes through the coil, generating an alternating magnetic field that causes eddy current self-heating in the rotary kiln 110. Within the rotary kiln 110, the raw material is heated to decompose carbonates. As the raw material travels, the decomposition product, CaO, diffuses with SiO2, Fe2O3, Al2O3, and other components in the raw material, undergoing a solid-phase reaction to form clinker minerals. During this process, carbonate decomposition produces carbon dioxide.

[0047] A pressure sensor 114 and a gas analyzer 115 are installed in the kiln head hood 112. The pressure sensor 114 is used to monitor the pressure data in the kiln head hood 112 in real time. The gas analyzer 115 is used to monitor the carbon dioxide concentration in the kiln head hood 112 in real time. By monitoring whether the carbon dioxide concentration exceeds the normal carbon dioxide content in the air (the carbon dioxide content in the air is 0.03%), it can be determined whether the air in the kiln head hood 112 is mixed with smoke.

[0048] The air cooling device is connected to the kiln head hood 112. The air cooling device is used to use air to cool the clinker produced by heating and calcining raw materials in the rotary kiln 110 via the electromagnetic induction device 113. The kiln head hood 112 is provided with a hot air duct 122 for conducting the air after heat exchange. The air cooling device can be a conventional device. For example, the air cooling device can adopt a grate cooler 120. A blower 121 for introducing air can be provided at the bottom of the grate cooler 120. The cooling gas in this embodiment adopts air, and other cooling gases can also be adopted. The gas object monitored by the gas analyzer 115 can be adaptively adjusted accordingly.

[0049] The first heat exchange device 130 is connected to the smoke chamber 111. It is used to exchange heat between the raw meal and the flue gas generated by calcining the raw meal in the rotary kiln 110. The first heat exchange device 130 includes a first raw meal inlet for introducing the raw meal and a first raw meal outlet for discharging the heat-exchanged raw meal into the smoke chamber 111. The first heat exchange device 130 can be a conventional device.

[0050] The second heat exchange device 140 is connected to the smoke chamber 111 and the hot air duct 122. The second heat exchange device 140 is used to exchange heat between the raw meal and the heat-exchanged air. The second heat exchange device 140 includes a second raw meal inlet for introducing the raw meal and a second raw meal outlet for discharging the heat-exchanged raw meal into the smoke chamber 111. The second heat exchange device 140 can be a conventional device.

[0051] The flue gas duct 150 is connected to the first heat exchange device 130. The flue gas duct 150 is equipped with a first fan 151 for discharging the flue gas after heat exchange. Under normal circumstances, the first fan 151 operates at a certain speed.

[0052] The air duct 160 is connected to the second heat exchange device 140. The air duct 160 is equipped with a second fan 161 for discharging the air after the secondary heat exchange. Under normal circumstances, the second fan 161 operates at a certain speed.

[0053] The control device 170 is connected to the pressure sensor 114, the gas analyzer 115, the first fan 151, and the second fan 161, respectively. When the carbon dioxide concentration monitored by the gas analyzer 115 is greater than a threshold value (i.e., the carbon dioxide content in the air is 0.03%), the control device 170 controls the speed of the first fan 151 to gradually increase until it reaches the speed that reduces the carbon dioxide concentration to the threshold value. During this period, the pressure value monitored by the pressure sensor 114 remains within a preset range, for example, between -10 Pa and -35 Pa. During the above process, if the pressure value monitored by the pressure sensor 114 exceeds the upper limit of the preset range (i.e., -35 Pa) while the speed of the first fan 151 is gradually increased, the control device 170 controls the speed of the second fan 161 to gradually decrease. At this time, the speed of the first fan 151 remains unchanged (i.e., the speed at which the speed adjustment of the second fan 161 was initiated) until the first and second fans 151, 161 reach the speeds that reduce the carbon dioxide concentration to the threshold value and the pressure to within the preset range. If the CO2 concentration has not yet fallen below the threshold value when the pressure value monitored by pressure sensor 114 is less than the lower limit of the preset range while the speed of second fan 161 is being gradually reduced, control device 170 controls the speed of first fan 151 to continue to gradually increase, while the speed of second fan 161 remains unchanged (i.e., the speed at which the speed adjustment of first fan 151 was initially performed). This process is repeated until first fan 151 and second fan 161 remain at the speed that reduces the CO2 concentration to the threshold value and the pressure to within the preset range.

[0054] In the above process, the control device 170, in conjunction with the pressure sensor 114, the gas analyzer 115, the first fan 151 and the second fan 161, makes adjustments with the aim of achieving a pressure balance point in the rotary kiln 110 at the kiln outlet end (near the kiln head hood 112). In this way, the carbon dioxide gas generated by the thermal decomposition of the raw material in the rotary kiln 110 is discharged only through the rotary kiln 110, the smoke chamber 111 and the first heat exchange device 130, and the air that exchanges heat with the clinker passes through the kiln head hood 112 and is discharged only through the hot air duct 122 and the second heat exchange device 140. The two are not mixed, thereby ensuring a high concentration of carbon dioxide in the flue gas.

[0055] According to the system 100 disclosed in the present invention, the raw material in the rotary kiln 110 is heated and calcined by the electromagnetic induction device 113, and the raw material decomposes to release carbon dioxide gas. Compared with the traditional method of burning fuel, no air is introduced, and the carbon dioxide concentration in the generated carbon dioxide flue gas is high; at the same time, the rotation speed of the first fan 151 and the second fan 161 is regulated by the control device 170 to control the carbon dioxide concentration to a threshold value and the pressure value to a preset range value, so that the carbon dioxide flue gas and the air after heat exchange each take their own paths and do not mix, further ensuring a high concentration of carbon dioxide; in addition, the entire system 100 uses air to cool the clinker, and uses the carbon dioxide flue gas and the air after heat exchange to preheat the raw material, so that energy is reused and energy consumption is low.

[0056] Referring to Figure 1, in order to provide a first heat exchange device 130 with a good heat exchange effect, the first heat exchange device 130 may include a plurality of cyclones 180 arranged from top to bottom. The number of cyclones 180 is not limited, for example, it can be 5, 6 or other numbers. Among them, the bottom material outlet of the cyclone 180 located at the bottom is connected to the smoke chamber 111. The gas inlet of the cyclone 180 located at the bottom is connected to the smoke chamber 111. The top gas outlet of the cyclone 180 located at the top is connected to the flue gas duct 150. The gas outlet of the cyclone 180 located at the bottom is connected to the cyclone 180 located above through the connecting pipe 181. The bottom material outlet of the cyclone 180 located at the top is connected to the connecting pipe 181 at the bottom. Among them, the raw material is fed into the connecting pipe 181 located at the top.

[0057] Continuing to refer to Figure 1, in order to provide a second heat exchange device 140 with good heat exchange effect, the second heat exchange device 140 may also include a plurality of cyclones 180 arranged from top to bottom. The number of cyclones 180 is not limited, for example, it can be 5, 6 or other numbers. The bottom material outlet of the cyclone 180 located at the bottom is connected to the smoke chamber 111. The gas inlet of the cyclone 180 located at the bottom is connected to the hot air duct 122. The top gas outlet of the cyclone 180 located at the top is connected to the air duct 160. The gas outlet of the cyclone 180 located at the bottom is connected to the cyclone 180 located above through the connecting duct 181. The bottom material outlet of the cyclone 180 located at the top is connected to the connecting duct 181 at the bottom. The raw material is fed into the connecting duct 181 located at the top.

[0058] To ensure that the material-gas ratio in the first heat exchanger 130 and the second heat exchanger 140 is substantially the same, the ratio of raw meal fed into the first heat exchanger 130 and the second heat exchanger 140 is 1:(2-5). For example, about 1 / 4 of the raw meal is fed into the first heat exchanger 130, and about 3 / 4 of the raw meal is fed into the second heat exchanger 140.

[0059] In a preferred embodiment, the flue gas discharged from the flue gas duct 150 may be further subjected to dust removal treatment by a dust collector 191. The flue gas after dust removal treatment may be connected to a carbon dioxide capture system 192 for use by the carbon dioxide capture system 192.

[0060] Furthermore, the flue gas duct 150 and the air duct 160 may also be connected to the waste heat boiler 190 to utilize waste heat.

[0061] 1 , the working process of the system 100 will be described below by taking the first heat exchange device 130 and the second heat exchange device 140 as an example in which six cyclones 180 are provided.

[0062] Raw meal is fed into the first heat exchange device 130 through connecting pipes 181 between cyclones C2A and C1-A1 and C1-A2, and between C2B and C1-B1 and C1-B2. Approximately one-quarter of the raw meal is fed into connecting pipe 181 between C2A and C1-A1 and C1-A2, while three-quarters is fed into connecting pipe 181 between C2B and C1-B1 and C1-B2. The raw meal is dispersed and heat-exchanged within connecting pipe 181 before entering cyclones C1-A1, C1-A2, C1-B1, and C1-B2 along with the airflow. The raw meal is separated in cyclones 180 and discharged from the top of cyclones 180. Cyclones C1-A1 and C1-A2 discharge high-concentration carbon dioxide flue gas, while cyclones C1-B1 and C1-B2 discharge hot air. The raw meal is collected in the cone of the cyclone 180 and discharged.

[0063] The raw meal discharged from the cones of the C1-A1 and C1-A2 cyclones is fed into the connecting pipe 181 between C2A and C3A. The raw meal discharged from the cones of the C1-B1 and C1-B2 cyclones is fed into the connecting pipe 181 between C2B and C3B. The raw meal is dispersed and heat-exchanged within connecting pipe 181, then enters the C2A and C2B cyclones along with the airflow. The raw meal is separated within cyclones 180 and discharged from the tops of cyclones 180. The C2A cyclone discharges high-concentration carbon dioxide flue gas, while the C2B cyclone discharges hot air. The raw meal is collected in the cones of the C2A and C2B cyclones and discharged. Similarly, the raw meal passes through the C3A, C3B, C4A, C4B, C5A, C5B, and C6A, C6B cyclones. After heating, the raw meal is finally discharged from the cones of the C6A and C6B cyclones and fed into the smoke chamber 111.

[0064] After heating, the raw material is fed into the smoke chamber 111 and then into the rotary kiln 110. High-frequency alternating current flows through the coils, generating an alternating magnetic field that causes eddy currents and self-heating in the rotary kiln 110. Within the kiln, the raw material is heated, causing carbonate decomposition. As the material travels, the decomposition product, CaO, diffuses with SiO₂, Fe₂O₃, Al₂O₃, and other components in the raw material, undergoing a solid-phase reaction to form clinker minerals. The material then passes through the kiln, completing the clinker calcination process. During this process, carbon dioxide gas produced by carbonate decomposition is transported from the kiln and the kiln tail smoke chamber 111 to the inlet of cyclone C6A.

[0065] The calcined clinker is fed into the front section of the grate cooler 120. The clinker continuously moves from the inlet to the outlet of the grate cooler 120, while simultaneously exchanging heat with the air entering from the blower 121 at the bottom of the grate cooler 120, completing the cooling of the clinker and heat recovery. High-temperature hot air at 700-850 degrees Celsius enters the inlet of the cyclone C6B through the kiln head hood 112 and the hot air duct 122. By controlling the rotational speed of the high-temperature first and second fans 151, 161, the pressure equilibrium point in the kiln is located at the kiln outlet (near the kiln head hood 112). This ensures that the CO2 decomposed in the kiln only travels through the rotary kiln 110 and enters the kiln tail smoke chamber 111, while the high-temperature hot air only enters the hot air duct 122 through the kiln head hood 112, ensuring that the two gases follow their own paths and do not mix.

[0066] The excess preheat at the tail end of the grate cooler 120 is discharged from the tail end and can enter the waste heat boiler 190 or be used for drying materials, etc.

[0067] The high-concentration CO2 flue gas from the outlets of cyclones C1-A1 and C1-A2, which has undergone heat exchange, enters the waste heat boiler 190 for waste heat utilization. It then enters the high-temperature first fan 151 and dust collector 191, and is fed into the CO2 capture system 192 for further CO2 purification. The hot air from the outlets of cyclones C1-B1 and C1-B2, which has undergone heat exchange, enters the waste heat boiler 190 for waste heat utilization, then enters the high-temperature second fan 161, is fed into the raw material drying and exhaust gas treatment systems, and is finally discharged through the chimney after dust removal.

[0068] In a second aspect, the present disclosure further provides a method for obtaining high-concentration carbon dioxide flue gas by calcining cement clinker, and a system 100 based on the above technical solution. The method specifically comprises the following steps:

[0069] The raw material is heated and decomposed in the rotary kiln 110 provided with the electromagnetic induction device 113 to generate carbon dioxide gas, and is calcined into clinker at the same time.

[0070] The flue gas containing the decomposed carbon dioxide gas enters the first heat exchange device 130 through the smoke chamber 111. The clinker enters the air cooling device through the kiln head hood 112 to exchange heat with the air for cooling. The air after heat exchange enters the second heat exchange device 140.

[0071] Before entering the rotary kiln 110, the raw material is respectively put into the first heat exchange device 130 and the second heat exchange device 140 to exchange heat with the flue gas and air. After the heat exchange, the raw material enters the rotary kiln 110 through the smoke chamber 111 for calcination. The flue gas and air after the heat exchange are discharged through the flue gas duct 150 and the air duct 160 respectively; among them, the flue gas discharged through the flue gas duct 150 is high-concentration carbon dioxide flue gas, and the carbon dioxide concentration in the flue gas is greater than 80%.

[0072] When the carbon dioxide concentration monitored by the gas analyzer 115 is greater than a threshold value, the first fan 151 gradually increases its speed until it reaches the speed at which the carbon dioxide concentration drops to the threshold value, and during this period, the pressure value monitored by the pressure sensor 114 remains within a preset range. During this process, if, while the first fan 151 is gradually increasing its speed, the pressure value monitored by the pressure sensor 114 is greater than the upper limit of the preset range but the carbon dioxide concentration has not dropped to the threshold value, the second fan 161 begins to gradually decrease its speed, while the first fan 151 maintains its speed unchanged, until the first fan 151 and the second fan 161 respectively reach the speeds at which the carbon dioxide concentration drops to the threshold value and the pressure drops to within the preset range value. During this process, if, while the second fan 161 is gradually decreasing its speed, the pressure value is less than the lower limit of the preset range value but the carbon dioxide concentration has not dropped to the threshold value, the first fan 151 continues to gradually increase its speed, while the second fan 161 maintains its speed unchanged. The above steps are repeated until the first fan 151 and the second fan 161 reach the speeds at which the carbon dioxide concentration drops to the threshold value and the pressure drops to within the preset range value.

[0073] Other embodiments of the present disclosure will be readily apparent to those skilled in the art from the description and practice of the present disclosure disclosed herein. The description and embodiments are intended to be exemplary only, with the true scope and spirit of the present disclosure being defined by the claims.

Claims

1. A system for obtaining high-concentration carbon dioxide flue gas based on calcining cement clinker, characterized in that: The system comprises: A rotary kiln, wherein a smoke chamber and a kiln head cover are respectively arranged at the tail and the head of the rotary kiln, and the rotary kiln is surrounded by an electromagnetic induction device along the length direction; a pressure sensor and a gas analyzer are arranged in the kiln head cover; an air cooling device, the air cooling device being connected to the kiln head cover and used for cooling the clinker produced by the rotary kiln heating and calcining the raw material via the electromagnetic induction device by air, the kiln head cover being provided with a hot air duct for guiding out the air after the heat exchange; A first heat exchange device connected to the smoke chamber, used for heat exchange between raw meal and smoke generated by calcining the raw meal in the rotary kiln, the first heat exchange device comprising a first raw meal inlet for introducing raw meal and a first raw meal outlet for leading the raw meal after heat exchange to the smoke chamber; a second heat exchange device connected to the smoke chamber and the hot air duct respectively, used for exchanging heat between the raw meal and the air after heat exchange, the second heat exchange device comprising a second raw meal inlet for introducing the raw meal and a second raw meal outlet for leading the raw meal after heat exchange to the smoke chamber; A flue gas duct connected to the first heat exchange device, wherein the flue gas duct is provided with a first fan for discharging the flue gas after heat exchange; An air duct connected to the second heat exchange device, wherein the air duct is equipped with a second fan for discharging air after secondary heat exchange; Among them, when the carbon dioxide concentration monitored by the gas analyzer is greater than the threshold value, the first fan gradually increases the speed until the carbon dioxide concentration drops to the threshold value; if the pressure value monitored by the pressure sensor is greater than the upper limit of the preset range value during the process of gradually increasing the speed of the first fan, the second fan begins to gradually reduce the speed until the carbon dioxide concentration drops to the threshold value and the pressure value drops to within the preset range value; if the carbon dioxide concentration has not dropped to the threshold value when the pressure value is less than the lower limit of the preset range value during the process of gradually reducing the speed of the second fan, the first fan continues to gradually increase the speed; repeat the above process until the carbon dioxide concentration drops to the threshold value and the pressure value drops to within the preset range value.

2. The system according to claim 1, characterized in that Also includes: a control device, the control device being connected to the pressure sensor, the gas analyzer, the first blower and the second blower respectively, and the control device being used for: when the carbon dioxide concentration monitored by the gas analyzer is greater than When the carbon dioxide concentration reaches the threshold, the speed of the first fan is controlled to increase gradually until it stays at the speed at which the carbon dioxide concentration can be reduced to the threshold, during which the pressure value monitored by the pressure sensor is within the preset range; if the pressure value monitored by the pressure sensor is greater than the upper limit of the preset range during the process of controlling the speed of the first fan to increase gradually, the speed of the second fan is controlled to decrease gradually, and the speed of the first fan is controlled to remain unchanged until the first fan and the second fan stay at the speed at which the carbon dioxide concentration can be reduced to the threshold and the pressure value can be reduced to the preset range; if the carbon dioxide concentration has not yet dropped to the threshold when the pressure value monitored by the pressure sensor is less than the lower limit of the preset range during the process of controlling the speed of the second fan to decrease gradually, the speed of the first fan is controlled to continue to increase gradually, and the speed of the second fan is controlled to remain unchanged; repeat the above process until the first fan and the second fan stay at the speed at which the carbon dioxide concentration can be reduced to the threshold and the pressure value can be reduced to the preset range.

3. The system according to claim 1 or 2, characterized in that: The first heat exchange device comprises a plurality of cyclones arranged from top to bottom, the bottom material outlet of the cyclone located at the bottom is connected to the smoke chamber, the gas inlet of the cyclone located at the bottom is connected to the smoke chamber, and the top gas outlet of the cyclone located at the top is connected to the smoke duct; wherein the gas outlet of the cyclone located at the bottom is connected to the cyclone located at the top through a connecting duct, and the bottom material outlet of the cyclone located at the top is connected to the connecting duct at the bottom; The raw material is fed into the connecting pipe located at the top.

4. The system according to claim 3, characterized in that The second heat exchange device also includes a plurality of cyclones arranged from top to bottom, the bottom material outlet of the cyclone located at the bottom is connected to the smoke chamber, the gas inlet of the cyclone located at the bottom is connected to the hot air duct, and the top gas outlet of the cyclone located at the top is connected to the air duct; wherein the gas outlet of the cyclone located at the bottom is connected to the cyclone located at the top through a connecting duct, and the bottom material outlet of the cyclone located at the top is connected to the connecting duct at the bottom; The raw material is fed into the connecting pipe located at the top.

5. The system according to claim 4, characterized in that The wind cooling device comprises a grate cooler, and a blower for introducing air is arranged at the bottom of the grate cooler.

6. The system according to claim 5, characterized in that The ratio of raw materials fed into the first heat exchange device and the second heat exchange device is 1:(2-5).

7. The system according to claim 1, characterized in that The flue gas discharged from the flue gas duct is further processed by a dust collector, and the processed flue gas can be connected to a carbon dioxide capture system.

8. The system according to claim 1, characterized in that The flue gas duct and / or the air duct are also connected to a waste heat boiler.

9. A method for obtaining high-concentration carbon dioxide flue gas based on calcining cement clinker, based on the system according to any one of claims 1 to 8, characterized in that: The method comprises: The raw material is heated and decomposed in a rotary kiln equipped with an electromagnetic induction device to produce carbon dioxide gas, while being calcined into clinker; The flue gas containing the carbon dioxide gas generated by decomposition enters the first heat exchange device through the smoke chamber, and the clinker enters the air cooling device through the kiln head cover to exchange heat with the air for cooling, and the air after heat exchange enters the second heat exchange device; Before entering the rotary kiln, the raw material is put into the first heat exchange device and the second heat exchange device respectively to exchange heat with the flue gas and the air. After the heat exchange, the raw material enters the rotary kiln through the smoke chamber for calcination. The flue gas and air after the heat exchange are discharged through the flue gas duct and the air duct respectively; wherein, the flue gas discharged through the flue gas duct is a high-concentration carbon dioxide flue gas, and the carbon dioxide concentration in the flue gas is greater than 80%; Among them, when the carbon dioxide concentration monitored by the gas analyzer is greater than the threshold value, the first fan gradually increases the speed until it stays at the speed when the carbon dioxide concentration drops to the threshold value, and the pressure value monitored by the pressure sensor during this period is always within the preset range value; in the above process, if the pressure value monitored by the pressure sensor is greater than the upper limit of the preset range value but the carbon dioxide concentration has not dropped to the threshold value while the first fan is gradually increasing the speed, the second fan begins to gradually reduce the speed, while the first fan maintains the speed unchanged, until the first fan and the second fan respectively stay at the speeds when the carbon dioxide concentration drops to the threshold value and the pressure value drops to the preset range value; in the above process, if the second fan is gradually reducing the speed, the carbon dioxide concentration still does not drop to the threshold when the pressure value is less than the lower limit of the preset range value, the first fan continues to gradually increase the speed, while the second fan maintains the speed unchanged; repeat the above steps until the first fan and the second fan stay at the speeds when the carbon dioxide concentration drops to the threshold value and the pressure value drops to the preset range value.

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