A high-concentration carbon dioxide capture system built on a cement kiln system and a low-carbon emission type cement clinker production line

Abstract

The present invention discloses a high-concentration carbon dioxide capture system built on a cement kiln system and a low-carbon emission type cement clinker production line. Among them, the high-concentration carbon dioxide capture system includes a first decomposing furnace, a preheater assembly, a first gas-solid separator, a second decomposing furnace device, and a second gas-solid separator; the feed end of the first decomposing furnace is connected to the discharge end of the preheater assembly, and the intake end of the first decomposing furnace is connected to the cement kiln system; the inlet end of the first gas-solid separator is connected to the outlet end of the first decomposing furnace, the discharge end of the first gas-solid separator is connected to the second decomposing furnace device, and the outlet end of the first gas-solid separator is connected to the intake end of the preheater assembly; the inlet end of the second gas-solid separator is connected to the second decomposing furnace device. The low-carbon emission type cement clinker production line includes a cement kiln system, a high-concentration carbon dioxide capture system, and a carbon monoxide generation system that are connected to each other. The present invention effectively realizes the series connection and circulation of the production of cement clinker, carbon dioxide, and carbon monoxide.

Description

Technical Field

[0001] The present invention relates to the technical field of cement clinker production, and specifically, to a high-concentration carbon dioxide capture system built on a cement kiln system and a low-carbon emission type cement clinker production line. Background Art

[0002] The cement industry is a major emitter of carbon dioxide. Theoretical analysis shows that, according to the current level of the cement industry, producing 1 ton of cement clinker emits approximately 940 kilograms of carbon dioxide. According to incomplete statistics, the carbon dioxide emitted by the cement industry accounts for about 20% of the total carbon dioxide emissions from industrial production in China. Therefore, the cement industry is facing great pressure to reduce carbon dioxide emissions.

[0003] To reduce carbon emissions, one is to cut overcapacity. About 75% of the carbon dioxide generated from the decomposition of limestone and coal combustion during the cement production process are the main carbon emission sources. According to the cement energy consumption level in China, about 0.7 - 0.8 tons of carbon dioxide are generated per ton of cement produced. Therefore, cutting overcapacity is the main measure for carbon emission reduction in the current cement industry in China.

[0004] The second is to seek alternative fuels. After more than 30 years of exploration, the technology and experience of alternative fuels in the cement industry have matured, becoming an important means for energy conservation and emission reduction in the cement industry of developed countries. 2 / 3 of the cement plants in developed countries use alternative fuels, and the average substitution ratio of combustible waste in the cement industry reaches 20%. A large number of production practices and experimental results in developed countries show that using alternative fuels and disposing of waste in the cement industry can avoid secondary pollution while producing qualified products, which is an effective way to meet both product quality and environmental protection indicators and is both technically and economically reasonable.

[0005] The third is to reduce the amount of clinker used in cement, such as the application of technologies such as limestone calcined clay cement (i.e., LC 3 low-carbon cement) currently being promoted.

[0006] However, the above methods have not well solved the contradiction between cement production and carbon emissions. Only by effectively capturing carbon dioxide within cement enterprises, enabling cement enterprises to produce cement and co-produce high-concentration carbon dioxide, and manufacturing a series of carbon dioxide products, is an effective strategy.

[0007] Main uses of carbon dioxide products:

[0008] 1. Main uses of industrial-grade carbon dioxide products

[0009] (1) Concrete mixing

[0010] When water and carbon dioxide meet, they will form carbonate ions, which combine with the free calcium ions that appear during the mixing of cement to form nano-scale calcium carbonate minerals. In this way, carbon dioxide is permanently sealed in the concrete in the form of minerals and will not re-enter the atmosphere even if the building is demolished many years later.

[0011] Generally speaking, for every 1 m 3 of concrete, about 15 kg of liquid carbon dioxide is required, and the cement consumption can be reduced by about 30 - 45 kg. Due to the use of carbon dioxide, the cost of each cubic meter of concrete can be reduced by more than 6 yuan. The annual concrete consumption in the country is about 2.5 billion cubic meters. If 10% of it uses carbon dioxide, the annual demand for liquid carbon dioxide can reach more than 3 million tons, and the concrete cost can be reduced by 1.5 billion yuan.

[0012] (2) Cement grinding aids

[0013] Most cement grinding aid enterprises in China now mainly use the production process of purchasing chemical raw materials for compounding. Utilizing carbon dioxide through chemical methods will promote the two-way linkage between the cement grinding aid and cement industries, forming a low-carbon circular industrial chain. Currently, with the continuous increase in the usage rate of cement grinding aids, the application rate of cement grinding aids in large and medium-sized cement enterprises in China will reach about 60% in the next one or two years. Calculated based on the total cement output of 1.7 billion t / a, with a powder grinding aid dosage of 4 kg / t and a liquid dosage of 1 kg / t, the market demand can reach more than 2 million t / a.

[0014] (3) Cold production of oil (such as shale oil, etc.)

[0015] According to the test and detection of a certain oilfield, using carbon dioxide flooding can increase crude oil production by 15% - 31%. Therefore, the amount of carbon dioxide required by the oilfield is difficult to estimate, and it is a market that is never saturated. The test shows that for successful carbon dioxide flooding, even for a small or medium-sized oil well, each injection of carbon dioxide requires more than 300 tons. Even if only one-tenth of the oilfields in China use carbon dioxide flooding, the annual demand for carbon dioxide will exceed 30 million tons.

[0016] (4) Chemical raw materials

[0017] Carbon dioxide can be used to synthesize a variety of inorganic and organic chemical products. The largest amount is used in the production of urea, ammonium bicarbonate, and soda ash. In addition, it can also react with ethylene oxide to prepare ethylene carbonate, and under certain conditions, it can be hydrolyzed to produce ethylene glycol, thereby obtaining the main raw material alcohol substances for cement grinding aids, biodegradable plastics, propylene carbonate, dimethyl carbonate and other products.

[0018] (5) Inert medium

[0019] In the processes of metal shielded welding, the new steelmaking technology of combined blowing from top and bottom in converter, fire extinguishing, animal anesthesia for slaughter, and replacement treatment of inflammable and explosive gas containers, a large amount of carbon dioxide gas is required.

[0020] 2. Main uses of food-grade carbon dioxide products

[0021] Food-grade carbon dioxide is mainly applied in the beverage and beer industries, the tobacco industry, anti-corrosion and preservation, and the cold chain transportation industry; high-purity carbon dioxide can be used in pharmaceuticals, electronics, biology, supercritical extraction, agricultural gas fertilizers, etc.

[0022] 3. Market demand potential of carbon dioxide products

[0023] Carbon dioxide is a valuable resource that can be utilized and has been listed by relevant organizations in the world as one of the most friendly gases to humans and is widely used in many fields such as chemistry, food, machining, and oil extraction. However, due to the high cost of capturing pure carbon dioxide, the annual utilization amount of carbon dioxide globally is less than 100 million tons at present, which is still a great waste.

[0024] According to relevant data reports, the production capacity of liquid carbon dioxide in the United States is 7.45 million t / a, in Japan is 1.17 million t / a, and the total consumption in Western Europe is 1.2 million t / a, while in China it is only 200,000 - 280,000 t / a at present. From the above data, it can be seen that the market demand potential of carbon dioxide in China is huge. It is predicted that in the next few years, the consumption of food-grade carbon dioxide in China will increase at an annual rate of 30%, and the total consumption will reach more than 10 million tons within 5 years.

[0025] 4. On carbon dioxide capture in the cement industry

[0026] In 2018, a 5000t / d cement clinker production line in China put into production a carbon dioxide project with an annual capture capacity of 50,000 tons using current conventional carbon capture and purification technology. However, because the carbon dioxide in the flue gas is very low (content 18 - 20%), this project can only produce industrial-grade liquid carbon dioxide. In addition, due to the high production cost and investment, except for a little contribution to carbon dioxide emission reduction, the overall investment return is not large, and it is impossible to achieve a balance among technology, cost, and return.

[0027] To sum up, it is necessary to design a technically feasible, stable, and reliable scheme for producing cement clinker from limestone and co-producing high-concentration carbon dioxide, so that not only can cement enterprises produce carbon dioxide series products as by-products in cement production (or recycle carbon dioxide into fuel to achieve ultra-low consumption of fuel in cement production), improve the efficiency of cement enterprises, but also it will be a great contribution to environmental protection. Summary of the Invention

[0028] In view of the deficiencies of the above-mentioned existing technologies, the present invention provides a high-concentration carbon dioxide capture system built on a cement kiln system and a low-carbon emission type cement clinker production line.

[0029] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0030] A high-concentration carbon dioxide capture system built on a cement kiln system includes a first decomposing furnace, a preheater assembly, and a first gas-solid separator; the feed end of the first decomposing furnace is connected to the discharge end of the preheater assembly, and the intake end of the first decomposing furnace is connected to the cement kiln system; the inlet end of the first gas-solid separator is connected to the outlet end of the first decomposing furnace, and the outlet end of the first gas-solid separator is connected to the intake end of the preheater assembly; it further includes a second decomposing furnace device and a second gas-solid separator, wherein:

[0031] The preheater assembly is used to introduce limestone powder and preheat it, and then introduce it into the first decomposing furnace, where it is preheated by the high-temperature kiln gas provided by the cement kiln system to the temperature at which the limestone powder is initially decomposed.

[0032] The discharge end of the first gas-solid separator is connected to the second decomposing furnace device; the first gas-solid separator performs gas-solid separation on the gas-solid mixture coming out of the first decomposing furnace. Among them, the separated high-temperature gas enters the preheater assembly to preheat the limestone powder, and the separated solid material enters the second decomposing furnace device.

[0033] The second decomposing furnace device is used to continue heating the solid material to fully decompose the solid material to obtain a gas-solid mixture containing carbon dioxide.

[0034] The inlet end of the second gas-solid separator is connected to the second decomposing furnace device, and is used to perform gas-solid separation on the gas-solid mixture containing carbon dioxide to achieve the capture of carbon dioxide.

[0035] Further, the second decomposing furnace device is connected to the cement kiln system through an atmospheric jet pump; under the action of the atmospheric jet pump, the second decomposing furnace device introduces balance air from the cement kiln system. This balance air is high-temperature air at a temperature of 900 - 950 °C and is used to assist the rapid discharge of carbon dioxide from the second decomposing furnace device.

[0036] Specifically, the second decomposing furnace device includes a second decomposing furnace and a heating device for providing heat source for the second decomposing furnace; the feed end of the second decomposing furnace is connected to the discharge end of the first gas-solid separator, and the outlet end of the second decomposing furnace is connected to the inlet end of the second gas-solid separator.

[0037] Still further, the second decomposing furnace is of a double-layer cylinder structure, with a sandwich between the inner cylinder and the outer cylinder. A heat conduction channel is arranged in the sandwich, and one end of the heat conduction channel is connected to the heating device and spirally wound around the inner cylinder.

[0038] Further, the other end of the heat conduction channel is connected to the inlet end of the first gas-solid separator.

[0039] Further, an electric heating device is also arranged in the interlayer.

[0040] Further, the carbon dioxide separated by the second gas-solid separator is discharged via the first high-temperature fan, and a heat exchanger is also connected between the air inlet of the first high-temperature fan and the air outlet end of the second gas-solid separator.

[0041] Based on the above high-concentration carbon dioxide capture system, the present invention also provides a low-carbon emission type cement clinker production line, including a cement kiln system, a high-concentration carbon dioxide capture system, and a carbon monoxide generation system; the second gas-solid separator in the high-concentration carbon dioxide capture system is connected to the cement kiln system, and the solid matter obtained by gas-solid separation of the second gas-solid separator is fed into the cement kiln system as the raw material of cement clinker; the carbon monoxide generation system is simultaneously connected to the high-concentration carbon dioxide capture system and the cement kiln system, and is used to feed the high-temperature gas provided by the cement kiln system and the carbon dioxide separated by the second gas-solid separator, and after converting the carbon dioxide into carbon monoxide, it is fed into the cement kiln system and / or the high-concentration carbon dioxide capture system as fuel.

[0042] Specifically, the carbon monoxide generation system includes a gasifier, two-stage cyclone separators, a waste heat boiler, a purification device, and a gas storage tank connected in sequence, and a heating jacket arranged outside the gasifier, wherein:

[0043] The gasifier is used to respectively feed coal, pure oxygen, and carbon dioxide from the high-concentration carbon dioxide capture system; the heating jacket is used to feed the high-temperature gas from the cement kiln system; under the action of high temperature, coal, pure oxygen, and carbon dioxide react in the furnace of the gasifier to generate a gas-solid mixture containing carbon monoxide;

[0044] The two-stage cyclone separators are used to feed the gas-solid mixture containing carbon monoxide and perform gas-solid separation, and the separated gas mixture containing carbon monoxide enters the waste heat boiler;

[0045] The waste heat boiler is used to cool the gas mixture and then send it into the purification device;

[0046] The purification device is used to purify the gas mixture to obtain carbon monoxide and then send it into the gas storage tank;

[0047] The gas storage tank is used to provide carbon monoxide to the cement kiln system and / or the first decomposition furnace.

[0048] Furthermore, the present invention further includes an auxiliary material preheater assembly. The air inlet end of the auxiliary material preheater assembly is connected to the air outlet end of the preheater assembly, and the material outlet end of the auxiliary material preheater assembly is connected to the inlet end of the second gas-solid separator. The auxiliary material preheater assembly preheats the cement auxiliary materials by using the high-temperature gas from the preheater assembly, and then enters the second gas-solid separator to be mixed with the gas-solid mixture containing carbon dioxide, and gas-solid separation is carried out. The separated calcium oxide and cement auxiliary material mixture is finally introduced into the cement kiln system.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] (1) The present invention can be directly built without substantially changing the existing cement kiln system and process, so as to realize the capture of high-concentration carbon dioxide on the cement clinker production line. In this way, cement enterprises only need low transformation costs to enable the cement clinker production line to have the ability to co-produce high-concentration carbon dioxide with limestone to produce cement clinker (or high-purity active calcium oxide), and the cost performance is very high. At the same time, the present invention also achieves the purpose of "N to N + 1" for the system (N represents the total number of preheaters + gas-solid separators on the original cement clinker production line, and 1 represents the newly added preheater or gas-solid separator), making the energy-saving effect of the entire production line better.

[0051] (2) In the present invention, before the limestone powder (mainly composed of calcium carbonate) enters the second decomposing furnace, due to the preheating effect of the preheater assembly and the first decomposing furnace, a good precondition is provided for the decomposition of the limestone powder. Therefore, when the second decomposing furnace continues to heat the limestone powder, it can be decomposed quickly and fully.

[0052] On this basis, the heating device in the present invention uses an external furnace heat transfer method to heat the limestone powder in the second decomposing furnace. The advantages are as follows: on the one hand, the external furnace heat transfer can be realized by selecting one or a combination of coal combustion, biomass combustion, hot air, electromagnetic heating, etc. according to the actual situation, which is very simple and feasible; on the other hand, after the gas-solid mixture coming out of the first decomposing furnace is subjected to gas-solid separation by the first gas-solid separator, the obtained solid material is introduced into the second decomposing furnace to continue heating and decomposing. At this time, since no other flue gas and impurities enter the second decomposing furnace, the gas decomposed contains a very high concentration of carbon dioxide, and finally is discharged after gas-solid separation by the second gas-solid separator. Experiments show that the carbon dioxide concentration in the gas discharged after gas-solid separation by the second gas-solid separator can reach more than 85%.

[0053] In this way, the present invention not only well retains the advantages of the original preheater, decomposition furnace and gas-solid separator on the cement clinker production line, but also combines the design of the second decomposition furnace device and the second gas-solid separator to greatly improve the concentration of captured carbon dioxide. In addition, the present invention is synchronized with the existing cement kiln system capacity and can fully realize the large-scale and large-scale capture of high-concentration carbon dioxide in the cement clinker production process, so that the carbon dioxide emission reduction rate of cement enterprises can reach more than 60%.

[0054] (3) The second decomposition furnace in the present invention adopts a double-layer structure design, and a heat conduction channel is set in the interlayer of the inner tube and the outer tube. The heat conduction channel is spirally wound on the inner tube. The heat source provided by the heating device heats the limestone powder in the form of radiation heat transfer through the heat conduction channel. This heating method can effectively prolong the heat exchange time and further ensure that the limestone powder is fully decomposed in the second decomposition furnace.

[0055] (4) The present invention also provides an electric heating device in the interlayer, which together with the heat conduction channel provides a heat source for the second decomposition furnace. The electric heating method is very advantageous in areas with conditions (such as small hydropower stations with cost advantages, or new energy power plants that mainly use photovoltaic and wind power generation). It can further stabilize the working conditions of the decomposition furnace without increasing the electricity cost to a small extent, so that the decomposition rate of the cement material can be stabilized to more than 96%, thereby achieving the purpose of "adapting measures to local conditions".

[0056] (5) In the present invention, the heat conduction channel is also connected to the first gas-solid separator. After heat transfer to the second decomposition furnace, the heat source is introduced from the first gas-solid separator into the preheater assembly, so that the remaining heat energy can continue to be utilized, further ensuring the preheating effect of the material and the stability of the preheating temperature.

[0057] (6) Since the decomposition of limestone powder in the second decomposition furnace will produce carbon dioxide (i.e.: CaCO3→CaO+CO2↑), and as carbon dioxide is continuously produced, a partial pressure will be formed. When the carbon dioxide partial pressure reaches a certain pressure, a side reaction will occur in the second decomposition furnace: CaO+CO2→CaCO3, which affects the decomposition of limestone powder. Therefore, the present invention also introduces a balancing wind from the cement kiln system to the second decomposition furnace, which utilizes the function of the atmospheric jet pump to realize forced ventilation in the second decomposition furnace, assist in the rapid discharge of carbon dioxide from the second decomposition furnace, and thereby prevent the calcium oxide after the decomposition of limestone powder from reacting with carbon dioxide to regenerate calcium carbonate.

[0058] (7) The present invention provides a carbon monoxide generation system. By reacting coal, pure oxygen, and carbon dioxide at high temperatures, and through processes such as gas-solid separation, cooling, and purification, high-purity carbon monoxide products can be obtained and supplied as fuel to the cement kiln system and / or the high-concentration carbon dioxide capture system. In this way, the present invention effectively realizes the internal circulation of carbon dioxide in the cement clinker production line and the ultra-low consumption of cement production fuel, achieving the goal of low carbon emissions. Moreover, it can also realize the sale of carbon assets, killing multiple birds with one stone and fully achieving the balance among technology, cost, and revenue.

[0059] (8) The present invention also provides an auxiliary material preheater assembly. By feeding limestone powder and cement auxiliary materials into different preheaters respectively, not only can the carbon dioxide concentration be further increased (the concentration can reach up to about 95%), but also since the limestone is ground separately, the fineness can be appropriately relaxed, thereby reducing the power consumption of raw meal grinding and further reducing the production cost.

[0060] (9) Each link of the present invention is closely interlocked, complementary, and tightly related. It effectively realizes the series connection and circulation of the production of cement clinker, high-purity active calcium oxide, carbon dioxide, and carbon monoxide. It can not only provide more product choices for cement enterprises and bring greater revenue, but also make a great contribution to environmental protection. Therefore, the present invention is very suitable for large-scale popularization and application in the cement industry. Description of the Drawings

[0061] Figure 1 It is a schematic structural diagram of Embodiment 1 of the present invention.

[0062] Figure 2 It is a schematic structural diagram of the second decomposition furnace in Embodiment 1 of the present invention.

[0063] Figure 3 It is a schematic structural diagram of Embodiment 2 of the present invention.

[0064] Figure 4 It is a schematic structural diagram of Embodiment 4 of the present invention.

[0065] Among them, the component names corresponding to the reference numerals are:

[0066] 1 - First decomposing furnace, 2 - Preheater assembly, 3 - Auxiliary material preheater assembly, 4 - First gas-solid separator, 5 - Second decomposing furnace, 6 - Heat conduction channel, 7 - Atmosphere jet pump, 8 - Heating device, 9 - Second gas-solid separator, 10 - Heat exchanger, 11 - First high-temperature fan, 12 - Cement kiln system, 1201 - Rotary kiln, 1202 - Tertiary air duct, 1203 - Grate cooler, 1204 - AQC boiler, 13 - Carbon monoxide generation system, 1301 - Coal bunker, 1302 - Gasifier, 1303 - Heating jacket, 1304 - Two-stage cyclone separator, 1305 - Waste heat boiler, 1306 - Purification device, 1307 - Gas storage tank, 1308 - Second high-temperature fan, 1309 - Cold slag cooler, 1310 - High-pressure blower. Specific embodiments

[0067] The present invention will be further described below in conjunction with the accompanying drawings and embodiments. The embodiments of the present invention include but are not limited to the following embodiments.

[0068] Embodiment 1

[0069] This embodiment provides a carbon dioxide capture system, which can directly capture high-concentration carbon dioxide on an existing cement clinker production line. As Figure 1 shown, this embodiment mainly includes a first decomposing furnace 1, a preheater assembly 2, a first gas-solid separator 4, a second decomposing furnace device and a second gas-solid separator 9 in terms of structure. The feed end of the first decomposing furnace 1 is connected to the discharge end of the preheater assembly 2, and the intake end of the first decomposing furnace 1 is connected to the cement kiln system; the inlet end of the first gas-solid separator 4 is connected to the outlet end of the first decomposing furnace 1, the discharge end of the first gas-solid separator 4 is connected to the second decomposing furnace device, and the outlet end of the first gas-solid separator 4 is connected to the intake end of the preheater assembly 2. The first decomposing furnace 1, the preheater assembly 2 and the first gas-solid separator 4 in this embodiment are all equipment on the original cement clinker production line. In this embodiment, the preheater assembly 2 is composed of preheaters C1 - C4; the first gas-solid separator 4 adopts a cyclone separator and is used for gas-solid separation of the gas-solid mixture conveyed from the first decomposing furnace 1.

[0070] The second decomposing furnace device is connected to the first gas-solid separator 4. The inlet end of the second gas-solid separator 9 is connected to the second decomposing furnace device. The second gas-solid separator 9 in this embodiment also adopts a cyclone separator. Both the second decomposing furnace device and the second gas-solid separator 9 are newly added devices on the original cement clinker production line and are key equipment for capturing high-concentration carbon dioxide. Specifically, the second decomposing furnace device includes a second decomposing furnace 5 and a heating device 8, where: the feeding end of the second decomposing furnace 5 is connected to the discharging end of the first gas-solid separator 4, and the outlet end of the second decomposing furnace 5 is connected to the inlet end of the second gas-solid separator 9. In this embodiment, the second decomposing furnace 5 has a double-layer cylinder structure, with a sandwich between the inner cylinder (lining) and the outer cylinder. A heat conduction channel 6 is arranged in the sandwich. One end of the heat conduction channel 6 is connected to the heating device 8 and spirally winds around the inner cylinder; the outer cylinder is made of heat-insulating and refractory materials to achieve heat insulation, and the inner cylinder is made of high-temperature-resistant materials, such as Figure 2 shown. The heating device 8 in this embodiment adopts the solution recorded in the patent publication number CN219530903U and is used to provide heat source for the second decomposing furnace 5, that is, the heating device 8 uses coal gangue as raw material, and after decarbonization and desulfurization treatment, high-temperature gas is supplied to the second decomposing furnace 5. And based on the characteristics of the solution recorded in CN219530903U, this embodiment can not only realize the high-value utilization of coal gangue in the co-production of cement clinker and carbon dioxide, but also greatly reduce the cost of co-producing high-concentration carbon dioxide with cement clinker.

[0071] In addition, the outlet end of the second gas-solid separator 9 is connected to a heat exchanger 10, and the outlet end of the heat exchanger 10 is also connected to a first high-temperature fan 11.

[0072] The process of capturing high-concentration carbon dioxide in this embodiment is as follows:

[0073] 1. Initially, the cement kiln system feeds high-temperature kiln gas into the first decomposing furnace 1. The high-temperature kiln gas enters the preheater assembly 2 through the first decomposing furnace 1 and the first gas-solid separator 4 and flows along the path of "C4 - C3 - C2 - C1". At the same time, cement raw materials (mainly a mixed powder of limestone and cement auxiliary materials) are fed into the preheater assembly 2 and preheated by the high-temperature kiln gas. The specific preheating process is as follows: The cement raw materials are fed into the air inlet pipe of the preheater C1. Under the action of the high-temperature kiln gas, the cement raw materials are preheated and carried into the preheater C1. Then, the cement raw materials and the gas flow rotate in C1, and gas-solid separation occurs. The cement raw materials enter the air inlet pipe of the preheater C2 through the discharge port of C1.

[0074] The raw cement meal entering the air inlet pipe of preheater C2 also undergoes the same process as described above under the action of high-temperature kiln gas, that is, the process of "C2 air inlet pipe - C2 - C2 discharge port - C3 air inlet pipe - C3 - C4 air inlet pipe - C4". Finally, it enters the first decomposing furnace 1 through the C4 discharge port, while the high-temperature kiln gas in the preheater assembly 2 is discharged through C1 after cooling and is further processed by the backend systems and equipment (such as SP boiler).

[0075] 2. In the first decomposing furnace 1, under the action of high-temperature kiln gas, the raw cement meal continues to be preheated to the temperature at which the limestone powder is initially decomposed, and then enters the first gas-solid separator 4 for gas-solid separation. Among them, the separated high-temperature gas enters the preheater assembly 2 to continue preheating the subsequent incoming raw cement meal, while the separated solid mixture enters the second decomposing furnace 5. The decomposition of limestone is a physical and chemical process affected by various factors, and its specific temperature range varies due to different external conditions and limestone characteristics. A large number of past studies have shown that: the decomposition temperature of the vast majority of limestone is usually in the range of 850 - 1000 °C, and a small amount of decomposition begins when the temperature approaches 800 °C. Therefore, in combination with practice, the raw cement meal can be preheated to about 830 °C. At this time, not only is the initial decomposition effect of the limestone powder the best, but it is also beneficial for the solid mixture to enter the second decomposing furnace 5 under the action of the gas flow.

[0076] 3. In the second decomposing furnace 5, the high-temperature gas provided by the heating device 8 enters the heat conduction channel 6 to flow. Under the action of radiative heat transfer in the heat conduction channel 6, the solid mixture continues to be heated until the limestone powder is fully decomposed to obtain a gas-solid mixture. In this gas-solid mixture, the solid is mainly calcium oxide and cement additives, and the gas is mainly carbon dioxide. Practice has shown that when heated to 900 - 950 °C, the effect of full decomposition of the limestone powder is the best, and the solid materials in the gas-solid mixture are also easily transported to the next stage under the action of the gas flow. If the heating temperature is too high, for example, exceeding 1200 °C, it is easy to cause local melting of the solid materials, resulting in blockage in the decomposing furnace and being unfavorable for the transportation of the solid materials.

[0077] In addition, during the decomposition process, as carbon dioxide is continuously generated, a partial pressure will be formed. When the carbon dioxide partial pressure reaches a certain level, side reactions are likely to occur, regenerating calcium carbonate (i.e., CaO + CO2 → CaCO3). Therefore, to effectively prevent this phenomenon, in this embodiment, the intake end of the second decomposer 5 is connected to the cement kiln system through an air ejector pump 7. Under the action of the air ejector pump, a part of the high-temperature gas in the cement kiln system is introduced and forms a balance air flow (high-temperature air) that is introduced into the second decomposer 5. Relying on the flow of the balance air, it can assist in quickly discharging carbon dioxide from the second decomposer, minimizing the occurrence of side reactions as much as possible, ensuring the smooth progress of the main reaction (i.e., CaCO3 → CaO + CO2↑), and enabling the limestone powder to be basically completely decomposed. At the same time, considering that the introduction of the balance air will reduce the temperature in the second decomposer 5, the temperature of the balance air introduced into the second decomposer 5 is 900 - 950°C, which is basically equivalent to the temperature in the second decomposer 5, with a difference of no more than 35°C between the two.

[0078] In addition, to further make full use of the heat source of the heating device 8, the other end of the heat conduction channel 6 is connected to the inlet end of the first gas-solid separator 4. The high-temperature gas flows in the heat conduction channel 6, and after heating the second decomposer 5, it enters the preheater assembly 2 through the first gas-solid separator 4 for heat energy reuse.

[0079] 4. The gas-solid mixture decomposed by the second decomposer 5 enters the second gas-solid separator 9, where gas-solid separation is carried out under the action of the second gas-solid separator 9. Among them, the separated gas (the concentration of carbon dioxide in which can reach 85 - 90%) is cooled by the heat exchanger 10 and then discharged by the first high-temperature fan 11, and then further processed by the backend system, such as purifying carbon dioxide to obtain various high-purity carbon dioxide products; or used for producing other products (such as producing carbon monoxide). The mixture of calcium oxide and cement auxiliary materials separated is then introduced into the cement kiln system, and finally, cement clinker products are obtained after being processed by the cement kiln system.

[0080] In addition, if cement clinker is not produced, cement auxiliary materials can be not added, and the separated calcium oxide is not introduced into the cement kiln system, thereby obtaining high-purity active calcium oxide products and co-producing high-concentration carbon dioxide. Thus, this embodiment enables the cement clinker production line to have the ability to co-produce cement clinker (or high-purity active calcium oxide) and high-concentration carbon dioxide from limestone. At the same time, this embodiment also achieves the purpose of "changing 5 to 6" for the preheater on the cement clinker production line, making the energy-saving effect of the entire production line better.

[0081] Embodiment 2

[0082] As Figure 3As shown in the figure, the difference from Embodiment 1 is that in this embodiment, the preheaters C3 and C4 are combined as the preheater assembly 2, the preheaters C1 and C2 are combined as the auxiliary material preheater assembly 3, and the discharge port of C2 is connected to the inlet end of the second gas-solid separator 9. In this way, the limestone powder and the cement auxiliary materials can be fed into the air inlet pipes of C3 and C1 respectively. Among them, the preheating process of the limestone powder is: C3 air inlet pipe - C3 - C3 discharge port - C4 air inlet pipe - C4 - C4 discharge port, and finally it enters the first decomposing furnace 1, and the subsequent process is the same as that of Embodiment 1; the preheating process of the cement auxiliary materials is: C1 air inlet pipe - C1 - C1 discharge port - C2 air inlet pipe - C2 - C2 discharge port. The cement auxiliary materials are preheated (usually the best effect is achieved when preheated to about 500 °C), and then enter the second gas-solid separator 9, where they are mixed with the gas-solid mixture coming out of the second decomposing furnace 5. At this time, according to the principle of instantaneous heat transfer, the temperature of the cement auxiliary materials can basically reach the same as that of the gas-solid mixture instantaneously, and then enter the subsequent process, and the subsequent process is the same as that of Embodiment 1.

[0083] Compared with Embodiment 1, in this embodiment, the limestone powder and the cement auxiliary materials are fed into the preheater assembly 2 and the auxiliary material preheater assembly 3 respectively. Subsequently, not only can the carbon dioxide concentration be further increased (the concentration can reach up to about 95% at most), but also because the limestone is ground separately, the fineness can be appropriately relaxed, thereby reducing the power consumption of raw meal grinding.

[0084] Embodiment 3

[0085] The difference from Embodiment 1 or 2 is that in this embodiment, an electric heating device is also provided in the interlayer of the second decomposing furnace 5, which together with the heat conduction channel 6 provides heat source for the second decomposing furnace 5. The electric heating device in this embodiment adopts the existing technology, and can be preferably adopted according to the actual situation in areas with conditions (such as small hydropower stations with cost advantages, or new energy power plants mainly using photovoltaic and wind power). On this basis, the solution of this embodiment has more advantages than Embodiment 1 or 2, because it can further stabilize the working condition of the decomposing furnace on the premise that the increase in electricity cost is not large, so that the decomposition rate of the cement material can be stably above 96%.

[0086] Embodiment 4

[0087] This embodiment provides a low-carbon emission type cement clinker production line, which mainly includes three major parts: the cement kiln system 12, the high-concentration carbon dioxide capture system, and the carbon monoxide generation system 13. As Figure 4As shown, the cement kiln system 12 is the same as that of the prior art and mainly consists of a rotary kiln 1201, a tertiary air duct 1202, a grate cooler 1203, and an AQC boiler 1204; the high-concentration carbon dioxide capture system is the same as that of Embodiment 2, wherein: the air inlet end of the second decomposer 5 is connected to the kiln tail of the rotary kiln 1201, and the balance air in the second decomposer 5 is provided by the tertiary air duct 1202; the calcium oxide and cement auxiliary materials separated by the second gas-solid separator 9 enter the rotary kiln 1201 and are calcined into cement clinker.

[0088] The carbon monoxide generation system 13 mainly uses the gas provided by the high-concentration carbon dioxide capture system (the carbon dioxide concentration therein can reach up to about 95%), and then converts carbon dioxide into carbon monoxide to provide fuel for the cement kiln system 12 and / or the high-concentration carbon dioxide capture system, thereby realizing the fuel recycling in the production process of cement clinker.

[0089] Specifically, the carbon monoxide generation system in this embodiment includes a coal bunker 1301, a gasifier 1302, two-stage cyclone separators 1304, a waste heat boiler 1305, a purification device 1306, and a gas storage tank 1307 connected in sequence, a heating jacket 1303 arranged outside the gasifier 1302, and a second high-temperature fan 1308 and a slag cooler 1309 both connected to the gasifier 1302, wherein:

[0090] The coal bunker 1301 is used to feed in coal (such as low-rank coal or semi-coke) that has been homogenized and crushed, and then it is fed into the gasifier 1302 by a screw feeder. In addition to coal, pure oxygen (purity ≥ 99%) and carbon dioxide discharged from the high-concentration carbon dioxide capture system (introduced through the second high-temperature fan 1308 and blown into the gasifier through the air distribution plate and air caps) are respectively fed into the gasifier 1302. The gasifier 1302 in this embodiment adopts an atmospheric circulating fluidized bed pulverized coal gasifier (or a new type of continuous gasifier), uses carbon dioxide and oxygen as gasification media (when the coal used is low-rank coal, the water vapor generated by the heat of its own moisture is also one of the gasification media), realizes the gasification of various coals at high temperature, the gas flow velocity in the furnace is between 5 and 7 m / s, and has a very high heat and mass transfer rate, and the gasification pressure is controlled at about 0.15 MPa.

[0091] The heating jacket 1303 outside the gasifier 1302 is fed with tertiary air (temperature: 1000 - 1100 °C) shunted from the kiln head of the cement kiln system. Under the action of high temperature, the coal, pure oxygen, and carbon dioxide in the furnace of the gasifier 1302 react to generate a gas-solid mixture containing carbon monoxide. The coal slag discharged from the gasifier 1302 can be used as a cement admixture after being cooled by the slag cooler 1309 for the production of, for example, LC 3 Low-carbon cement products.

[0092] The main reactions in the furnace of the gasifier 1302 are as follows:

[0093] C + O2 → CO2

[0094] C + CO2 → 2CO

[0095]

[0096] Among them, in addition to participating in the reaction, carbon dioxide also acts as a heat carrier and a temperature regulator, controlling the maximum temperature in the furnace below the ash fusion point of the coal to prevent caking of coal slag.

[0097] In addition, when using low-rank coal, in addition to the above main reactions, there are also the following reactions:

[0098] C + H2O = CO + H2

[0099] This reaction also produces carbon monoxide and can also displace some hydrogen.

[0100] Moreover, after the high-temperature gas in the heating jacket 1303 cools down, it can be recycled to the AQC boiler 1204 of the cement kiln system 12 by the high-pressure blower 1310 for power generation.

[0101] The two-stage cyclone separator 1304 is used to introduce the above-mentioned gas-solid mixture containing carbon monoxide and perform gas-solid separation. The separated gas mixture containing carbon monoxide enters the waste heat boiler 1305; the separated solid matter (mainly unburned pulverized coal) returns to the gasifier 1302 to continue participating in the reaction.

[0102] The waste heat boiler 1305 is used to cool down the incoming gas mixture and then send it into the purification device 1306. The steam generated by the waste heat boiler during cooling can be used as steam for power generation.

[0103] The purification device 1306 is used to purify the cooled gas mixture to obtain carbon monoxide and then send it into the gas storage tank 1307. The purification device 1306 in this embodiment adopts an existing MDEA decarbonization device + desulfurization equipment. First, the carbon dioxide in the gas mixture is removed by the MDEA technology (the removed carbon dioxide can return to the gasifier 1302 to participate in the reaction), and then desulfurization and deoxidation treatments are carried out to obtain carbon monoxide gas with a purity of about 95%. Finally, it is stored in the gas storage tank 1307 and provided as fuel to the cement kiln system 12 and / or the first decomposition furnace 1, enabling the recycling of carbon dioxide.

[0104] Although the present invention seems simple, it is not easy to conceive. Only by continuously delving deep in the fields of cement production and related chemical engineering technologies can an effective series connection and formation of a cycle be achieved between a cement clinker production line and other product production lines with a simple, reliable, and industrialization- and scale-suitable solution, thereby providing more product options for cement enterprises and bringing greater revenue generation, and also contributing to environmental protection. Therefore, compared with the prior art, the present invention has prominent substantive features and remarkable progress.

[0105] The above embodiments are only the preferred embodiments of the present invention and should not be used to limit the protection scope of the present invention. Any meaningless modifications or polishings made on the main design concept and spirit of the present invention, as long as the technical problems solved are still the same as those of the present invention, should be included within the protection scope of the present invention.

Claims

1. A high-concentration carbon dioxide capture system built on a cement kiln system, comprising a first decomposition furnace (1), a preheater assembly (2), and a first gas-solid separator (4); the feed end of the first decomposition furnace (1) is connected to the discharge end of the preheater assembly (2), and the air inlet end of the first decomposition furnace (1) is connected to the cement kiln system; the inlet end of the first gas-solid separator (4) is connected to the outlet end of the first decomposition furnace (1), and the air outlet end of the first gas-solid separator (4) is connected to the air inlet end of the preheater assembly (2); characterized in that, It also includes a second decomposition furnace device and a second gas-solid separator (9), wherein: The preheater assembly (2) is used to introduce limestone powder and preheat it, and then introduce it into the first decomposition furnace (1), and the high-temperature kiln gas provided by the cement kiln system is preheated to the temperature at which the limestone powder is initially decomposed; The discharge end of the first gas-solid separator (4) is connected to the second decomposition furnace device; the first gas-solid separator performs gas-solid separation on the gas-solid mixture discharged from the first decomposition furnace, wherein the separated high-temperature gas enters the preheater assembly to preheat the limestone powder, and the separated solid material enters the second decomposition furnace device; The second decomposition furnace device is used to continue heating the solid material so that the solid material is fully decomposed to obtain a gas-solid mixture containing carbon dioxide; the second decomposition furnace device comprises a second decomposition furnace (5) and a heat supply device (8) for providing a heat source for the second decomposition furnace; the feed end of the second decomposition furnace (5) is connected to the discharge end of the first gas-solid separator (4), and the outlet end of the second decomposition furnace (5) is connected to the inlet end of the second gas-solid separator (9); the second decomposition furnace (5) is a double-layer cylinder structure, with an interlayer between the inner cylinder and the outer cylinder, a heat conduction channel (6) is provided in the interlayer, and one end of the heat conduction channel (6) is connected to the heat supply device (8); The second gas-solid separator (9) is used to perform gas-solid separation on the gas-solid mixture containing carbon dioxide, thereby capturing the carbon dioxide; The second decomposition furnace (5) is connected to the cement kiln system via an atmospheric jet pump (7); under the action of the atmospheric jet pump, the second decomposition furnace (5) introduces balancing air from the cement kiln system, the temperature of the balancing air differing from the temperature in the second decomposition furnace (5) by no more than 35°C, and is used to assist in the rapid discharge of carbon dioxide from the second decomposition furnace, so as to reduce the occurrence of the side reaction: CaO+CO2→CaCO3, ensure the smooth progress of the main reaction: CaCO3→CaO+CO2↑, and enable the limestone powder to be basically completely decomposed.

2. A high concentration carbon dioxide capture system built on a cement kiln system according to claim 1, characterized in that: The balanced wind is high temperature air with a temperature of 900-950°C.

3. A high concentration carbon dioxide capture system built on a cement kiln system according to claim 1 or 2, characterized in that: The heat conducting channel (6) is spirally wound on the inner cylinder.

4. A high concentration carbon dioxide capture system built on a cement kiln system according to claim 1 or 2, characterized in that: The other end of the heat-conducting channel (6) is connected to the inlet end of the first gas-solid separator (4).

5. A high concentration carbon dioxide capture system built on a cement kiln system according to claim 4, characterized in that: An electric heating device is also arranged in the interlayer.

6. A high concentration carbon dioxide capture system built on a cement kiln system according to claim 1, 2 or 5, characterized in that: The carbon dioxide separated by the second gas-solid separator (9) is discharged via a first high-temperature fan (11), and a heat exchanger (10) is also connected between the air inlet of the first high-temperature fan (11) and the air outlet of the second gas-solid separator (9).

7. A low-carbon emission cement clinker production line, comprising a cement kiln system, characterized in that: It also includes the high-concentration carbon dioxide capture system as described in any one of claims 1 to 6, and a carbon monoxide generation system; the second gas-solid separator in the high-concentration carbon dioxide capture system is connected to the cement kiln system, and the solid matter obtained by gas-solid separation by the second gas-solid separator is introduced into the cement kiln system as a raw material for cement clinker; the carbon monoxide generation system is connected to the high-concentration carbon dioxide capture system and the cement kiln system at the same time, and is used to introduce the high-temperature gas provided by the cement kiln system and the carbon dioxide separated by the second gas-solid separator, and after converting the carbon dioxide into carbon monoxide, it is introduced into the cement kiln system and / or the high-concentration carbon dioxide capture system as fuel.

8. A low-carbon emission cement clinker production line according to claim 7, characterized in that: The carbon monoxide generation system comprises a gasifier (1302), a two-stage cyclone separator (1304), a waste heat boiler (1305), a purification device (1306) and a gas storage cabinet (1307) connected in sequence, and a heating jacket (1303) arranged outside the gasifier (1302), wherein: The gasifier is used to introduce coal, pure oxygen and carbon dioxide from a high-concentration carbon dioxide capture system respectively; the heating jacket is used to introduce high-temperature gas from a cement kiln system; under the action of high temperature, coal, pure oxygen and carbon dioxide react in the furnace of the gasifier to generate a gas-solid mixture containing carbon monoxide; The two-stage cyclone separator is used to introduce a gas-solid mixture containing carbon monoxide and perform gas-solid separation, and the separated mixed gas containing carbon monoxide enters the waste heat boiler; The waste heat boiler is used to cool the mixed gas and then send it to the purification device; The purification device is used to purify the mixed gas to obtain carbon monoxide, which is then sent into the gas storage cabinet; The gas storage cabinet is used to provide carbon monoxide to the cement kiln system and / or the first decomposition furnace.

9. A low-carbon emission cement clinker production line according to claim 7 or 8, characterized in that: The invention also comprises an auxiliary material preheater component (3), the air inlet end of the auxiliary material preheater component (3) is connected to the air outlet end of the preheater component (2), and the discharge end of the auxiliary material preheater component (3) is connected to the inlet end of the second gas-solid separator (9); the auxiliary material preheater component uses the high-temperature gas from the preheater component to preheat the cement auxiliary material, and then the auxiliary material enters the second gas-solid separator to be mixed with the gas-solid mixture containing carbon dioxide, and the gas-solid separation is carried out, and the separated calcium oxide and cement auxiliary material mixture is finally introduced into the cement kiln system.

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