System and method for low-energy-consumption carbon capture and purification of flue gas of full-system oxygen-fuel combustion cement kiln

Abstract

The invention discloses a system and a method for low-energy-consumption carbon capture and purification of flue gas of a full-system oxygen-fuel combustion cement kiln, the system comprises an oxygen-fuel combustion cement clinker production system and a carbon capture and purification system, an air outlet at the top end of a preheater is respectively connected with a cooling medium inlet of the front two sections of a cooler and the carbon capture and purification system; the carbon capture and purification system comprises a precooler, a steam-water separator, a first booster fan, a vacuum pressure swing adsorption system, a second booster fan, a flue gas deep purification system, a refrigerator and a rectification system, and the volume fraction of CO2 in gas recovered by the vacuum pressure swing adsorption system is 85-97%; a recovered gas outlet of the vacuum pressure swing adsorption system is sequentially connected with a second booster fan, a flue gas deep purification system, a refrigerator and a rectification system, and a gas outlet of the rectification system is connected with an inlet of the vacuum pressure swing adsorption system. According to the invention, stable operation of the full-system oxygen-fuel combustion system is realized, and meanwhile, the overall CO2 recovery rate of the carbon capture and purification system is improved, so that the carbon capture CO2 recovery rate is greater than or equal to 95%.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas carbon capture, and particularly to a system and method for low-energy consumption carbon capture and purification of flue gas from a cement kiln with full-system oxy-fuel combustion. Background Technique

[0002] Full-system oxy-fuel combustion is based on the existing industrial kiln system, using high-purity oxygen to replace the combustion-supporting air, and at the same time adopting flue gas recirculation to adjust the medium flow rate and heat transfer characteristics of the entire kiln system, and enriching all CO 2 during fuel combustion and raw material decomposition, and CO with a volume concentration of up to more than 80% can be obtained. 2 Flue gas, so that after being captured, purified and realized at a small cost, permanent sequestration or resource utilization of CO 2 can be achieved, and large-scale industrial CO 2 enrichment and emission reduction can be realized. Existing analyses have shown that compared with other carbon capture methods, the oxy-fuel combustion technology has advantages in terms of investment cost, operating cost, CO 2 emission reduction cost, large-scale and compatibility with existing technologies.

[0003] The oxy-fuel combustion technology is a research hotspot in the field of carbon emission reduction in the international cement industry. Compared with traditional air combustion, the oxy-fuel combustion technology can increase the CO 2 concentration at the outlet of the preheater at the kiln tail to more than 80%. However, simply relying solely on the oxy-fuel combustion technology to increase the CO 2 concentration in the flue gas will significantly increase the comprehensive energy consumption per unit of CO 2 preparation and increase the unit CO 2 preparation cost. CO 2 can be further purified and concentrated by other technical means. The flue gas from the cement kiln out of the oxy-fuel combustion system mainly consists of carbon dioxide and nitrogen after pretreatment such as desulfurization and denitrification. Therefore, the separation of the pre-purified flue gas is mainly the separation between carbon dioxide and nitrogen. Currently, the main CO 2 purification methods include cryogenic distillation separation, pressure swing adsorption and membrane separation. From the perspective of economy and investment scale, cryogenic distillation separation technology is more suitable for higher concentrations of CO 2 (>90%), suitable as the final purification step to prepare high-purity CO 2 products; membrane separation technology is highly dependent on membrane preparation technology, and the membrane itself may have problems such as easy fouling, easy damage and short service life. This technology is still in the development stage; pressure swing adsorption separation technology has simple equipment and mature technology, and is suitable for the purification process of medium and high concentrations of CO 2 (50% - 80%), with lower cost and energy consumption, and this technology has obvious advantages in the field of flue gas separation.

[0004] Chinese Patent Publication No. CN 115867515 A proposes a system and method for producing cement clinker by all-oxygen combustion. This patent uses the CO 2 recirculating flue gas discharged from the top of the preheater as a cooling medium and introducing it into the cooler, and after heat exchange, it is used as the fourth air and introduced into the bottom of the preheater. However, the relatively low-temperature CO 2 recirculating flue gas still carries acidic vapors such as water vapor, sulfur, chlorine, and fluorine. When directly introduced into the cooler, acid condensation is very likely to occur, and during long-term use, it will corrode the internal metal connectors, seals, anchor bolts, and ventilation pipelines of the cooler, weaken the sealing function, and shorten the service life of the device.

[0005] In addition, Chinese Patent Publication No. CN115164592A discloses a system and method for secondary all-oxygen combustion enrichment of CO 2 in a decomposition furnace, and proposes to use all-oxygen combustion combined with flue gas recirculation technology to achieve CO 2 enrichment in the raw material decomposition part. However, during the preparation of cement clinker, 5-10% of the raw materials still need to be decomposed in the firing stage, and a large amount of CO 2 generated by the coal powder combustion at the kiln head is not effectively enriched. Chinese Patent Publication No. CN115745438A discloses a system and method for all-oxygen combustion coupling low-energy consumption carbon purification in a cement kiln, and proposes to further purify the CO 2 in the flue gas at the outlet of all-oxygen combustion to 90%-95% by pressure swing adsorption. However, this method does not consider the problem that the exhaust gas outside the pressure swing adsorption tower still contains a large amount of low-concentration CO 2 that is not recycled, resulting in a reduction in the overall CO 2 recovery rate of the system. Chinese Patent Publication No. CN112608049A discloses a low-energy consumption carbon enrichment cement production system and method with circulating preheating, and this method realizes the CO 2 enrichment process in the entire system of the cement kiln furnace. However, this system does not have a special design for the clinker cooler, and air leakage may occur between each cooling section, affecting the CO 2 enrichment concentration and the overall CO 2 recovery rate of the system. Summary of the Invention

[0006] The purpose of the present invention is to provide a system and method for low-energy consumption carbon capture and purification of all-oxygen combustion cement kiln flue gas in the entire system, which solves the problems of direct emission of tail gas in the process of the existing all-oxygen combustion cement kiln furnace system, CO 2 escaping during the capture and purification process resulting in a decrease in the CO 2 recovery rate of the system, acid condensation caused by directly introducing relatively low-temperature CO 2 recirculating flue gas into the all-oxygen combustion system, and significantly increasing the unit CO 2Problems such as a significant increase in comprehensive energy consumption and production costs are addressed, and it has the advantages of low energy consumption and high carbon dioxide recovery rate.

[0007] The present invention is realized as follows. A low-energy carbon capture and purification system for the flue gas of an all-oxygen combustion cement kiln includes an all-oxygen combustion cement clinker production system and a carbon capture and purification system.

[0008] The all-oxygen combustion cement clinker production system includes a preheater, a decomposition furnace, a kiln tail smoke chamber, a rotary kiln, and a cooler connected in sequence. The air outlet at the top of the preheater is respectively connected to the first two sections of the cooling medium inlets of the cooler and the carbon capture and purification system. The dry-based CO discharged from the air outlet at the top of the preheater 2 CO with a concentration of 75 - 85% 2 Recycled flue gas;

[0009] The carbon capture and purification system includes a precooler, a steam-water separator, a first booster fan, a vacuum pressure swing adsorption system, a second booster fan, a flue gas deep purification system, a refrigerating machine, and a rectification system. The precooler, the steam-water separator, the first booster fan, and the vacuum pressure swing adsorption system are connected in sequence. The external exhaust outlet of the vacuum pressure swing adsorption recovery system is connected to the waste gas treatment system. The CO in the gas recovered by the vacuum pressure swing adsorption system 2 has a volume fraction of 85 - 97%. The recovered gas outlet of the vacuum pressure swing adsorption system is connected to the second booster fan, the flue gas deep purification system, the refrigerating machine, and the rectification system in sequence. The flue gas deep purification system includes a denitrification bed, a drying bed, and an adsorption bed connected in sequence. The rectification system includes a rectification tower, a reboiler, and a liquefied product storage tank. The purified gas outlet of the refrigerating machine is connected to the inlet of the rectification tower. The gas outlet of the rectification tower is connected to the cooling gas inlet of the refrigerating machine through multi-stage pressure reduction. The cooling gas outlet of the refrigerating machine is connected to the inlet of the vacuum pressure swing adsorption system. The liquid outlet of the rectification tower is connected to the reboiler and the liquefied product storage tank in sequence.

[0010] In the above technical solution, preferably, a flue gas pretreatment system is provided on the pipeline of the air outlet at the top of the preheater. The flue gas pretreatment system includes a dust removal and denitrification device, a wet desulfurization device, and a flue gas water washing system arranged in sequence. The flue gas water washing system includes a water storage tank, a water washing pump, and a flue gas water washing tower. The outlet of the wet desulfurization device is connected to the air inlet of the flue gas water washing tower. The water storage tank is connected to the water inlet of the flue gas water washing tower through the water washing pump. The water outlet of the flue gas water washing tower is connected to the inlet of the water washing pump. The air outlet of the flue gas water washing tower is respectively connected to the recycled flue gas pipeline and the carbon capture and purification system. The recycled flue gas pipeline is respectively connected to the first two sections of the cooling medium inlets of the cooler.

[0011] In the above technical solution, further preferably, a flue gas preheater is provided on the recycled flue gas pipeline for preheating the recycled flue gas above the dew point temperature. The recycled flue gas pipeline is made of corrosion-resistant stainless steel, and a heat insulation layer is provided on the outer side of the pipeline.

[0012] In the above technical solution, preferably, the cooler is divided into three sections from the clinker inlet to the outlet, namely the first section of the cooler, the second section of the cooler, and the third section of the cooler; the air outlet of the cyclone separator at the top of the preheater is connected to the air inlet of the first section of the cooler and the air inlet of the second section of the cooler, and a mixture of high-concentration O 2 and CO 2 circulating flue gas is introduced into the air inlet of the first section of the cooler. The secondary air intake and the tertiary air intake of the cooler are located in the first section of the cooler and are respectively connected to the rotary kiln and the decomposition furnace; only CO 2 circulating flue gas is introduced into the air inlet of the second section of the cooler. The quaternary air intake is located in the second section of the cooler and is connected to the inlet of the last-stage cyclone of the preheater; a medium-mounted roller crusher is arranged between the second section and the third section of the cooler, and steam generated by indirectly drying fuel is introduced into the air chamber below the medium-mounted roller crusher.

[0013] In the above technical solution, further preferably, a first resistance baffle for reducing the leakage of the O 2 / CO 2 mixture in the first section of the cooler from leaking into the second section of the cooler is arranged between the first section and the second section of the cooler; a second resistance baffle is arranged between the second section and the third section of the cooler; the height of the bottom ends of the first resistance baffle and the second resistance baffle is less than or equal to 300 mm from the corresponding cooler bed clearance, and the first resistance baffle and the second resistance baffle are rotating movable baffles.

[0014] In the above technical solution, further preferably, a high-concentration oxygen inlet is arranged on the channel at the air inlet of the first section of the cooler.

[0015] In the above technical solution, preferably, a tertiary air inlet, a raw material feeding point, and a fuel feeding point are arranged on the decomposition furnace. The tertiary air inlet is located in the middle and lower part of the decomposition furnace. At least one raw material feeding point and one fuel feeding point are arranged between the tertiary air inlet and the bottom constriction of the decomposition furnace, and the raw material feeding point is located above the fuel feeding point.

[0016] A method for low-energy-consumption carbon capture and purification of the flue gas of an all-oxygen combustion cement kiln includes the following steps:

[0017] Feed the raw material into the all-oxygen combustion preheater, and the raw material exchanges heat and undergoes gas-solid separation with the flue gas in the preheater to preheat the raw material to the decomposition temperature;

[0018] The preheated raw material enters the all-oxygen combustion decomposition furnace, and the heat released by the fuel combustion is used for the raw material in the decomposition furnace to absorb heat and decompose to obtain calcined raw material; the calcined raw material enters the rotary kiln for calcination to obtain hot clinker; the hot clinker is cooled in the cooler to obtain cement clinker;

[0019] The CO 2The recycled flue gas enters the preheater, and the low-temperature flue gas after heat exchange is discharged through the air outlet of the cyclone separator at the top of the preheater;

[0020] The CO discharged from the air outlet of the cyclone separator at the top of the preheater 2 The recycled flue gas is divided into two paths. One path enters the all-oxygen combustion cement clinker production system as a cooling medium and enters the cooler, and the other path enters the carbon capture and purification system;

[0021] The CO entering the carbon capture and purification system 2 The recycled flue gas is first precooled and cooled down to 0 - 10 °C, and free water is separated by gas-water separation. Subsequently, it enters the vacuum pressure swing adsorption system to concentrate and recover CO 2 The CO discharged from the vacuum pressure swing adsorption system 2 has a concentration range of 85 - 97%; the concentrated and recovered CO-rich 2 gas is pressurized and then enters the flue gas deep purification system, and is deeply purified through denitrification, drying and adsorption in sequence. The purified flue gas is cooled to -15 - -35 °C by a refrigerating machine and then introduced into the rectification column; the rectification column separates H 2 , CH 4 , CO, O 2 , N 2 and other light component impurities and non-condensable gases are discharged from the top of the rectification column, and after multi-stage decompression, they are used as the cooling gas of the refrigerating machine. After heat exchange and cold quantity recovery, they enter the vacuum pressure swing adsorption system again to control the CO 2 concentration in the exhaust gas outside the vacuum pressure swing adsorption system ≤ 20%; the liquid enters the liquefied product storage tank for storage, and the CO 2 purity in the liquid product ≥ 99.5%.

[0022] In the above technical solution, preferably, the CO 2 discharged from the air outlet of the cyclone separator at the top of the preheater, the recycled flue gas first undergoes dust removal and denitrification to control the dust particulate matter in the flue gas ≤ 5 mg / Nm 3 , NOx ≤ 50 mg / Nm 3 , then undergoes desulfurization to control the SO 2 in the flue gas ≤ 5 mg / Nm 3 , then undergoes water washing to reduce the flue gas temperature to ≤ 40 °C, reduce the water content in the flue gas to ≤ 10%, and the CO 2 wet basis concentration ≥ 80%. After that, it is divided into two paths and enters the all-oxygen combustion cement clinker production system and the carbon capture and purification system.

[0023] In the above technical solution, preferably, the CO 2 entering the all-oxygen combustion cement clinker production system, the recycled flue gas is first preheated to ≥ 60 °C.

[0024] In the above technical solution, preferably, the O 2 / CO 2 The mixed gas is used as secondary air and tertiary air respectively. The secondary air is introduced into the rotary kiln, and the tertiary air is introduced into the decomposition furnace. The CO discharged from the second section of the cooler 2 The recycled flue gas is introduced into the bottom of the preheater as the fourth air.

[0025] In the above technical solution, further preferably, the O in the secondary air and the tertiary air 2 concentration is 30% - 70%; the dry basis concentration of CO in the fourth air 2 is 75 - 85%, and the O 2 concentration is less than 5%.

[0026] In the above technical solution, preferably, the CO discharged from the air outlet of the cyclone separator at the top of the preheater 2 in the recycled flue gas, the CO 2 dry basis concentration is 75 - 85%, the temperature range is 300 - 400 °C, and the water content is 20% - 25%.

[0027] The advantages and positive effects of the present invention are:

[0028] 1. In the present invention, the CO entering the carbon capture and purification system 2 The recycled flue gas meets the inlet conditions of the raw material gas for the vacuum pressure swing adsorption (VPSA) process after pre-cooling, water removal, and compression. The vacuum pressure swing adsorption system purifies the CO gas through a series of steps including adsorption, equal pressure reduction, vacuum pumping, reflux flushing, equal pressure increase, and final pressure increase cycle 2 The resulting gas has a CO 2 volume fraction of 85 - 97%.

[0029] 2. In the present invention, the CO concentrated by the vacuum pressure swing adsorption system 2 is pressurized to the pressure required for the rectification process. After three - stage deep impurity removal, it enters the rectification system through low - temperature liquefaction. A liquid product with a CO concentration ≥ 99.5% is obtained at the bottom of the rectification column. The exhaust gas at the top of the rectification column is depressurized and then exchanges heat again to recover cold energy, and then is mixed with the raw material gas of the vacuum pressure swing adsorption system to complete the pressure swing adsorption concentration process in the column. The CO concentration in the exhaust gas of the vacuum pressure swing adsorption system is controlled to be ≤ 20%, improving the CO 2 recovery rate of the carbon capture and purification system, so that the CO 2 recovery rate of the carbon capture and purification system remains above 95%. 2 3. The present invention aims to increase the CO 2 enrichment concentration in the oxy - fuel combustion of the cement kiln. Special considerations are given to the air supply method and sealing form of the oxy - fuel combustion cooler, and the temperature of the flue gas entering the cooler is controlled to avoid the CO at a lower temperature

[0030] from entering the cooler. 2 entering the cooler, thus avoiding the CO at a lower temperature 2Directly introducing the circulating flue gas into the cooler is extremely likely to cause the problem of acid condensation. At the same time, by arranging rotating movable baffles, the flue gas flow resistance between each section of the cooler is increased, and the air leakage between the first and second sections of the cooler is avoided without affecting the movement of the grate bars of the material bed. 2 The steam generated by the drying system is introduced as a cooling medium into the lower air chamber of the center-mounted roller crusher to form a steam curtain, making the gas environments in the front and rear cooling zones of the roller crusher relatively independent at a relatively low cost, and avoiding the introduction of air into the system due to air leakage through the roller gap, which affects the system's CO 2 enrichment concentration. Description of the Drawings

[0031] Figure 1 It is a schematic diagram of the low-energy-consumption carbon capture and purification system for the flue gas of a full-system oxy-fuel combustion cement kiln provided in Embodiment 1 of the present invention.

[0032] In the figure: A - high-concentration oxygen; B - CO 2 circulating flue gas; C - air; D - steam; g2 - secondary air; g3 - tertiary air; g4 - quaternary air; g5 - air discharged from the third section of the cooler; F - fuel; R - raw material; K - cement clinker;

[0033] 1 - cooler; 101 - the first section of the cooler; 102 - the second section of the cooler; 103 - the third section of the cooler; 104 - center-mounted roller crusher; 1041 - the first resistance baffle; 1042 - the second resistance baffle; 1a - the material bed of the first section of the cooler; 1b - the material bed of the second section of the cooler; 1c - the material bed of the third section of the cooler;

[0034] 2 - rotary kiln; 3 - decomposition furnace; 4 - preheater; 5 - kiln tail flue gas chamber; 6 - dust removal and denitrification device; 7 - wet flue gas desulfurization device; 8 - tail exhaust fan; 9 - circulation fan; 10 - flue gas preheater; 11 - flue gas water washing system; 1101 - water storage tank; 1102 - water washing pump; 1103 - flue gas water washing tower; 12 - precooler; 13 - steam-water separator; 14 - first booster fan; 15 - vacuum pressure swing adsorption system; 16 - second booster fan; 17 - flue gas deep purification system; 1701 - denitrification bed; 1702 - drying bed; 1703 - adsorption bed; 18 - refrigerator; 19 - rectification system; 1901 - rectification tower; 1902 - reboiler; 1903 - liquefied product storage tank; 20 - multi-stage decompression; 21 - carbon circulation fan;

[0035] The dotted line with an arrow represents the air flow direction; the solid line with an arrow represents the material flow direction. Detailed Embodiments

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "inside", "outside", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0038] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0039] Example 1

[0040] See also Figure 1 An embodiment of the present invention provides a system for low-energy consumption carbon capture and purification of cement kiln flue gas using full-oxygen combustion, including a full-oxygen combustion cement clinker production system and a carbon capture and purification system.

[0041] The oxy-fuel combustion cement clinker production system comprises a preheater 4, a decomposition furnace 3, a kiln tail smoke chamber 5, a rotary kiln 2, and a cooler 1 which are connected in sequence.

[0042] The number of stages of the preheater is 4 to 7. The air inlet of the cyclone separator at the bottom of the preheater 4 is connected to the air outlet pipe of the decomposition furnace 3, and the air outlet of the cyclone separator at the top of the preheater 4 discharges dry CO. 2 CO concentration of 75-85% 2 Circulating flue gas B. A raw material feed port is provided on the connecting air duct between the top cyclone separator of the preheater 4 and the second stage cyclone separator, a discharge port of the penultimate stage cyclone separator of the preheater 4 is connected to the decomposition furnace 3, and a discharge port of the bottom cyclone separator of the preheater 4 is connected to the kiln tail smoke chamber 5.

[0043] Cement raw meal R is fed into the raw meal inlet of the preheater 4. The raw meal R is preheated step by step from top to bottom in the preheater until the hot raw meal enters the second-to-last-stage cyclone separator and then enters the decomposition furnace 3 through the downcomer. In order to regulate the temperature field distribution in the first decomposition furnace 3, the raw meal downcomer entering the decomposition furnace 3 can be set to multiple according to the number of coal injection points, which can be set by those skilled in the art according to actual needs. The hot raw meal is decomposed in the decomposition furnace, and then undergoes gas-solid separation by the bottom cyclone separator of the preheater 4, and then enters the rotary kiln 2 for calcination and the cooler 1 for cooling to produce the cement clinker K.

[0044] The top air outlet of the preheater 4 is respectively connected to the first two sections of the cooling medium inlets of the cooler 1 and the carbon capture and purification system. The dry-based CO discharged from the top air outlet of the preheater 4 2 CO with a concentration of 75-85% 2 Recirculating flue gas.

[0045] Specifically, the oxygen production system provides high-concentration oxygen A with ≥90%. The all-oxygen combustion decomposition furnace is a low-NOx type decomposition furnace, and the NOx at the furnace outlet is controlled to be ≤500 mg / Nm through gradient combustion self-denitrification 3 (@10% O 2 ); The all-oxygen combustion preheater outlet generates CO 2 Recirculating flue gas. The CO in the obtained flue gas 2 The volume fraction is 75%-85%, and the volume fraction of H 2 O is 15-20%, and the volume fraction of O 2 is 4%-6%. The volume fraction of SO 2 is 0.1-0.12%. The dust content of the flue gas is ≤100 g / Nm 3 , and the temperature range is 250-400 °C.

[0046] The carbon capture and purification system includes a precooler 12, a steam-water separator 13, a first booster fan 14, a vacuum pressure swing adsorption system 15, a second booster fan 16, a flue gas deep purification system 17, a refrigerator 18 and a rectification system 19. The precooler 12, the steam-water separator 13, the first booster fan 14, and the vacuum pressure swing adsorption system 15 are connected in sequence. The external exhaust outlet of the vacuum pressure swing adsorption recovery system 15 is connected to the waste gas treatment system. The CO in the gas recovered by the vacuum pressure swing adsorption system 15 2With a volume fraction of 85-97%, the recovery gas outlet of the vacuum pressure swing adsorption system 15 is successively connected to a second booster fan 16, a flue gas deep purification system 17, a refrigerating machine 18, and a rectification system 19. The flue gas deep purification system 17 includes a denitrification bed 1701, a drying bed 1702, and an adsorption bed 1703 connected in sequence. The rectification system 19 includes a rectification tower 1901, a reboiler 1902, and a liquefied product storage tank 1903. The purified gas outlet of the refrigerating machine 18 is connected to the inlet of the rectification tower 1901. The gas outlet of the rectification tower 1901 is connected to the cooling gas inlet of the refrigerating machine 18 through multi-stage decompression 20. The cooling gas outlet of the refrigerating machine 18 is connected to the inlet of the vacuum pressure swing adsorption system 15. The liquid outlet of the rectification tower 1901 is successively connected to the reboiler 1902 and the liquefied product storage tank 1903.

[0047] CO from the flue gas washing system 11 2 The circulating flue gas B enters the pre-cooler 12 and is cooled to 0-10°C, and then the moisture in the flue gas is removed by the steam-water separator 13, so that the water content in the flue gas ≤ 1.5%. After being compressed to 0.2-0.4 MPa in the first stage, it enters the vacuum pressure swing adsorption system 15. The CO in the flue gas 2 enters the vacuum pressure swing adsorption system 15 as a heavy component and is adsorbed by the adsorbent. The adsorbent is preferably silica gel. The unadsorbed N 2 and O 2 and other light components flow out from the top of the adsorption tower. According to the CO 2 concentration in the raw material gas, the vacuum pressure swing adsorption system 15 is in series with multiple towers, and the CO 2 concentration out of the vacuum pressure swing adsorption system 15 can reach 85-97%. Taking the first-stage vacuum pressure swing adsorption as an example, the adsorption-regeneration process of the adsorption tower follows the following procedure: The raw material gas CO 2 meeting the adsorption pressure is preferentially adsorbed and retained in the adsorption bed layer as a strongly adsorbed component, realizing the enrichment of CO 2 in the adsorption bed; The pressure energy is recovered through the equalizing pressure drop process, and the O 2 , N 2 and other light component gases are released in the forward release order and enter the tower in the regeneration process to reduce the pressure in the adsorption bed; After the forward release is completed, the light components are basically discharged out of the tower, and then the CO 2 gas in the adsorption bed is released in the reverse adsorption direction by means of vacuum pumping, and the adsorbent is regenerated. The CO 2 gas enters the buffer tank; After the reverse release is completed, the light component gas discharged from the tower in the adsorption step is used to flush the bed layer in the reverse adsorption direction to carry out the CO 2 remaining in the adsorbent and the dead zone of the bed layer out of the tower; After the flushing step is completed, the adsorption bed is successively subjected to the equalizing pressure increase and final pressure increase steps by using the exhaust gas during the equalizing pressure drop process of the adsorption tower that has completed adsorption, and then the next adsorption is carried out.

[0048] The heavy component product gas exiting the vacuum pressure swing adsorption system 15 is pressurized to 2.0 - 3.0 MPa through secondary compression. The pressurized gas enters from the bottom of the 1701st layer of the denitrification bed and passes through the adsorbent preset inside the bed layer to control NOx, C 6 H 6 、C 3 ~C 7 、CH 3 X and other hydrocarbon substances in the flue gas are at the ppm level, where NOx ≤ 2 ppm; TOC ≤ 40 ppm. The flue gas then enters the drying bed 1702 from the top of the denitrification bed 1701. After passing through the preset adsorbent, H 2 O and impurities such as HF in the flue gas are removed, making the saturated water content ≤ 30 ppmv and reducing HF to 0 ppmvF; the gas phase exits from the top of the drying bed 1702 and enters the adsorption bed 1703. After being treated with the preset adsorbent to remove solid particles, Hg, NH 3 ,Hg is reduced to ≤ 0.00015 ppmv, the metal particles are 0 ppmv, TOC is reduced to 0 ppm (v / v), and NH 3 is reduced to ≤ 10 ppmv. The purified flue gas exits from the top of the bed layer. The regeneration temperature of the three bed layers is 100 - 250 °C.

[0049] The purified flue gas is cooled to -15 - -35 °C by the refrigerator 18 and then introduced into the distillation column 1901. By adjusting the reflux ratio, H 2 、CH 4 、CO、O 2 、N 2 and other light component impurities and non-condensable gases are discharged from the top of the distillation column 1901, and the liquid enters the liquefied product storage tank 1903 for storage. The purity of CO 2 in the liquid product is ≥ 99.5%.

[0050] There is still 50 - 80% of CO 2 gas in the flue gas discharged from the top of the distillation column 1901. In order to improve the CO 2 recovery rate of the carbon capture and purification system, the flue gas discharged from the top of the distillation column 1901 is depressurized in multiple stages 20 to 0.2 - 0.3 MPa, so that the pressure of the discharged gas drops to the pressure of the raw material gas of the vacuum pressure swing adsorption system 15. After achieving pressure balance, it exchanges heat with the refrigerator 18 to recover the cold energy, and then enters the vacuum pressure swing adsorption system 15. It is mixed with the raw material gas entering the vacuum pressure swing adsorption system 15 and enters the adsorption tower. The vacuum pressure swing adsorption system 15 recovers CO 2 in the flue gas discharged from the top of the distillation column 1901, and controls the CO 2 concentration in the exhaust gas of the vacuum pressure swing adsorption system 15 to ≤ 20%, so that the CO 2 recovery rate of the carbon capture and purification system remains above 95%.

[0051] As a preferred embodiment, a flue gas pretreatment system is provided on the pipeline at the air outlet at the top of the preheater 4. The flue gas pretreatment system includes a dust removal and denitration device 6, a wet desulfurization device 7, and a flue gas water washing system 11 arranged in sequence. The flue gas water washing system 11 includes a water storage tank 1101, a water washing pump 1102, and a flue gas water washing tower 1103. The outlet of the wet desulfurization device 7 is connected to the air inlet of the flue gas water washing tower 1103. The water storage tank 1101 is connected to the water inlet of the flue gas water washing tower 1103 through the water washing pump 1102. The water outlet of the flue gas water washing tower 1103 is connected to the inlet of the water washing pump 1102. The air outlet of the flue gas water washing tower 1103 is respectively connected to a circulating flue gas pipeline and a carbon capture and purification system. The circulating flue gas pipeline is respectively connected to the inlet of the first two sections of the cooling medium of the cooler 1.

[0052] The dust removal and denitration device 6 includes a bag filter or a candle filter unit and an SCR reaction zone. The candle filter unit is composed of a high-temperature ceramic / metal fiber filter element, a pulse back-blowing dust cleaning system, and a conical ash hopper equipped with a double-layer pneumatic ash discharge valve. The SCR reaction zone uses a honeycomb catalyst module, and a V-W / Ti or V-Mo / Ti or a composite catalyst containing active elements such as Fe, Ce, Mn, Bi, and Cu can be selected. CO 2 The circulating flue gas B passes through the bag filter or the candle filter unit provided in the dust removal and denitration device 6 to control the dust particles in the flue gas to ≤5mg / Nm 3 , and uses SCR to remove NOx in the CO 2 circulating flue gas, and controls the NOx in the CO 2 circulating flue gas to ≤50mg / Nm 3 . Then, it undergoes a solid sulfur fixation reaction with the desulfurization agent slurry in the wet desulfurization device 7. The desulfurization agent can be selected from active components containing CaCO 3 or Ca(OH) 2 to control the SO 2 in the CO 2 circulating flue gas to ≤5mg / Nm 3 . At the same time, the wet desulfurization device 7 can reduce the flue gas temperature to ≤60°C. The water vapor in the flue gas condenses and removes the liquid water as the temperature decreases, reducing the water content in the flue gas to ≤20%. To meet the requirement of the water content in the flue gas for the carbon capture and purification system, the CO 2 circulating flue gas enters the flue gas water washing system 11 through the tail gas exhaust fan 8 for further cooling and water removal. The flue gas temperature is reduced to ≤40°C, and the water content in the flue gas is reduced to ≤10%. The CO 2 wet basis concentration ≥80%.

[0053] As a preferred embodiment, a flue gas preheater 10 is provided on the circulating flue gas pipeline to preheat the circulating flue gas above the dew point temperature. The circulating flue gas pipeline is made of corrosion-resistant stainless steel, and a heat insulation layer is provided on the outer side of the pipeline.

[0054] The remaining CO that has not entered the carbon capture and purification system 2 The circulating flue gas B is introduced into the cooler 1 as a clinker cooling medium by the circulating fan 9. In order to avoid the condensation of the flue gas during the long-distance transportation through the circulating pipeline, it is necessary to transform the water vapor in the flue gas into an unsaturated state. The dew point temperature of the circulating flue gas is determined by the Antoine equation (lgP = 8.07131 - 1730.63 / (T + 233.426), where P is the saturated vapor pressure, mmHg) to determine the CO 2 The flue gas is reheated to ≥60 by the installed flue gas reheater and then introduced into the cooler 1. During the process, the flue gas is always maintained above the dew point temperature. At the same time, the pipeline is considered to be made of corrosion-resistant stainless steel and an insulation layer is provided on the outside to ensure that the flue gas temperature is always maintained above the dew point temperature to the greatest extent and avoid condensation corrosion of the pipeline and equipment.

[0055] As a preferred implementation method, the combustion-supporting gas used in the all-oxygen combustion cement clinker production system enters the rotary kiln 2 and the decomposition furnace 3 respectively from the cooler 1. The cooler 1 is divided into three sections from the clinker inlet to the outlet (during the process of cooling the clinker), namely the first section 101 of the cooler, the second section 102 of the cooler, and the third section 103 of the cooler; the air outlet of the cyclone separator at the top of the preheater 4 is connected to the air inlet of the first section 101 of the cooler and the air inlet of the second section 102 of the cooler. The air inlet of the first section 101 of the cooler is introduced with high-concentration O 2 mixed with CO 2 The mixed gas of the circulating flue gas B. The secondary air intake and the tertiary air intake of the cooler are located in the first section of the cooler and are connected to the rotary kiln 2 and the decomposition furnace 3 respectively; the air inlet of the second section 102 of the cooler is only introduced with CO 2 circulating flue gas B. The quaternary air intake is located in the second section 102 of the cooler and is connected to the inlet of the last-stage cyclone of the preheater; a central roller crusher 104 is arranged between the second section and the third section of the cooler, and steam D generated by indirectly drying the fuel is introduced into the air chamber below the central roller crusher 104.

[0056] The high-concentration oxygen O of the oxygen production system 2 mixed with CO 2 circulating flue gas B enters the first section 101 of the cooler for mixing, and after heat exchange with the clinker, it enters the decomposition furnace 3 and the rotary kiln 2 as the secondary air g2 and the tertiary air g3 respectively. The air inlet of the second section 102 of the cooler is only introduced with CO 2 circulating flue gas B. After heat exchange with the clinker, it enters the last-stage cyclone of the preheater as the quaternary air g4, which can reduce the high CO in the decomposition furnace 2The decomposition temperature of the raw meal under partial pressure, and to avoid the problem of the inner wall of the last-stage cyclone in the preheater being blocked by the build-up of raw meal due to the increase in the decomposition temperature of the raw meal and the delayed combustion of the fuel. The cooling air of the third section 103 of the cooler is divided into two streams. The first stream is located in the front section of the third section of the cooler (the air chamber under the center roller crusher), and the steam D generated by drying the fuel moisture is introduced into the cooling air chamber under the center roller crusher 104. The second stream is located in the rear section of the third section of the cooler, and air C is introduced. The direct leakage of air between the recycled flue gas B and the air used in the rear section of the third section of the cooler can further control the air leakage between the second and third sections of the cooler, and to the greatest extent reduce the impact on the clinker cooling effect and ensure the clinker quality. Part of the steam discharged from the front section of the third section of the cooler is mixed with the four-time air through the gap of the center roller crusher and enters the preheater. The remaining steam is mixed with the air discharged from the rear section of the third section of the cooler and is directly discharged from the system as low-grade heat. 2 The direct cross-leakage of air between the recycled flue gas B and the air used in the rear section of the third section of the cooler can further control the air leakage between the second and third sections of the cooler, and to the greatest extent reduce the impact on the clinker cooling effect and ensure the clinker quality. Part of the steam discharged from the front section of the third section of the cooler is mixed with the four-time air through the gap of the center roller crusher and enters the preheater. The remaining steam is mixed with the air discharged from the rear section of the third section of the cooler and is directly discharged from the system as low-grade heat.

[0057] Relative to the conventional clinker burning system, the air volume of the secondary and tertiary air is 0.8 - 1.0 Nm 3 / kg.cl. In the oxy-fuel combustion system, the air volume of the secondary and tertiary air drops significantly to 0.4 - 0.6 Nm 3 / kg.cl. The remaining CO 2 The external discharge of the recycled flue gas will lead to a reduction in the heat recovery efficiency of the cooler. Therefore, the remaining CO 2 used as the clinker cooling medium is introduced into the preheater 4, which can improve the heat efficiency of the cooler while avoiding the direct introduction of this part of the flue gas into the furnace, resulting in an increase in the CO 2 partial pressure in the decomposition furnace and an increase in the carbonate decomposition temperature. On the other hand, it can avoid the problem of the inner wall of the lowest-stage cyclone in the preheater 4 being blocked due to an increase in the outlet temperature of the decomposition furnace.

[0058] As a preferred embodiment, a first resistance baffle 1041 is provided between the first section 101 and the second section 102 of the cooler to reduce the cross-leakage of the O 2 / CO 2 mixed gas from the first section 101 of the cooler into the second section of the cooler; a second resistance baffle 1042 and a center roller crusher 104 are provided between the second section 102 and the third section 103 of the cooler. The steam D generated by indirectly drying the fuel is introduced into the air chamber under the center roller crusher as a cooling medium to form an air curtain to further block the cross-leakage. The bottom height of the first resistance baffle 1041 and the second resistance baffle 1042 is less than or equal to 300 mm from the corresponding clinker bed gap of the cooler. The first resistance baffle 1041 and the second resistance baffle 1042 are rotating movable baffles.

[0059] To further reduce the cross-leakage problem caused by the difference in induced draft air pressure between the sections of the cooler, a first resistance baffle is provided between the first section 101 and the second section 102 of the cooler to reduce the cross-leakage of the O2 / CO 2 The mixed gas leaks into the first resistance baffle 1041 in the second section of the cooler, preventing O 2 from not being fully burned in the cement kiln and being introduced into the preheater by the fourth air and directly entering the carbon dioxide purification system, increasing the load of the oxygen production system and the power consumption of the carbon dioxide purification system; a second resistance baffle 1042 is arranged between the second section 102 and the third section 103 of the cooler. On the basis of using steam D cooling medium as an air curtain to block the leaking air in the lower air chamber of the center roller crusher 104, it further prevents the leakage of CO 2 between the circulating flue gas B cooling medium and the air C cooling medium, reducing the influence of air entering the second section of the cooler through the gap of the center roller crusher on the CO 2 enrichment concentration and the CO 2 circulating flue gas entering the third section of the cooler causing CO 2 escape and affecting the CO 2 recovery rate. The bottom height of the first resistance baffle 1041 and the second resistance baffle 1042 is ≤ 300 mm from the corresponding cooler bed gap. The first resistance baffle 1041 and the second resistance baffle 1042 are rotating movable baffles. When large clumps and large balls of clinker enter the cooler and the material layer contacts the baffle, hindering the reciprocating movement of the grate plate, they can rotate flexibly to avoid abnormal operation of the cooler.

[0060] As a preferred embodiment, a high-concentration oxygen inlet is arranged on the channel at the air inlet of the first section 101 of the cooler.

[0061] The existing cooling air volume required for cooling clinker by the cooler is 1.8 - 2.0 Nm 3 / kg.cl to achieve the clinker cooling effect. The O 2 and CO 2 circulating flue gas in the all-oxygen combustion system cooler can provide a cooling air volume of 0.4 - 0.6 Nm 3 / kg.cl. The remaining cooling media are provided by the water vapor generated by indirect drying of the fuel and the conventional air C respectively. And the cooling air chamber into which water vapor is introduced is arranged below the center roller crusher between the O 2 / CO 2 circulating flue gas and the conventional air cooling air chamber, avoiding the escape of CO 2 circulating flue gas to the outside during the heat exchange process with the raw meal.

[0062] As a preferred embodiment, a tertiary air inlet, a raw meal feeding point, and a fuel feeding point are arranged on the decomposition furnace 3. The tertiary air inlet is located in the middle and lower part of the decomposition furnace 3. At least one raw meal feeding point and one fuel feeding point are arranged between the tertiary air inlet and the bottom constriction of the decomposition furnace, and the raw meal feeding point is located above the fuel feeding point.

[0063] In this embodiment, a tertiary air regulating valve is provided on the pipeline between the tertiary air intake of the cooler 1 and the tertiary air inlet of the precalciner 3, which is used to regulate the amount of tertiary air entering the precalciner 3. A quaternary air regulating valve is provided on the pipeline between the quaternary air intake of the cooler 1 and the bottom air inlet of the preheater 4, which is used to distribute the amount of quaternary air leading to the preheater, so as to achieve adjustable air volume.

[0064] A method for low-energy carbon capture and purification of flue gas from an all-system oxy-fuel combustion cement kiln includes the following steps:

[0065] Feed the raw meal R into the oxy-fuel combustion preheater 4, where the raw meal exchanges heat with the flue gas and undergoes gas-solid separation in the preheater to preheat the raw meal to the decomposition temperature;

[0066] The preheated raw meal enters the oxy-fuel combustion precalciner 3, and the heat released by fuel combustion is used for the raw meal in the precalciner 3 to absorb heat and undergo carbonate decomposition reaction to release CO 2 And obtain the calcined raw meal; the calcined raw meal enters the rotary kiln 2 and is calcined within the temperature range of 1100 - 1450 °C to synthesize the mineral phase, obtaining the hot clinker; the hot clinker is cooled in the cooler 1 to obtain the cement clinker K;

[0067] CO generated by fuel combustion and raw meal decomposition 2 The circulating flue gas enters the preheater 4, and the low-temperature flue gas after heat exchange is discharged from the air outlet of the cyclone separator at the top of the preheater 4;

[0068] CO discharged from the air outlet of the cyclone separator at the top of the preheater 4 2 The circulating flue gas B is divided into two paths, one path enters the all-system oxy-fuel combustion cement clinker production system as a cooling medium and enters the cooler, and the other path enters the carbon capture and purification system;

[0069] CO entering the carbon capture and purification system 2 The circulating flue gas B is first precooled and cooled to 0 - 10 °C, and free water is separated by gas-water separation, and then enters the vacuum pressure swing adsorption system 15 to concentrate and recover CO 2 The CO discharged from the vacuum pressure swing adsorption system 15 2 The concentration range is 85 - 97%; the concentrated and recovered CO-rich 2 gas is pressurized and then enters the flue gas deep purification system 17, and is deeply purified in sequence through denitrification, drying and adsorption. The purified flue gas is cooled to -15 - 35 °C by the refrigerating machine 18 and then introduced into the distillation column 1901; the distillation column 1901 removes H 2 、CH 4 、CO、O 2 、N 2Light components such as impurities and non-condensable gases are discharged from the top of the distillation column 1901, and after being depressurized in multiple stages by 20, they are used as the cooling gas of the refrigerating machine. After heat exchange to recover the cold energy, they enter the vacuum pressure swing adsorption system 15 through the carbon circulation fan 21, and the CO in the exhaust gas outside the vacuum pressure swing adsorption system 15 is controlled. 2 The concentration ≤ 20%; the liquid then enters the liquefied product storage tank 1903 for storage, and the CO in the liquid product 2 The purity ≥ 99.5%.

[0070] As a preferred embodiment, the CO discharged from the air outlet of the cyclone separator at the top of the preheater 4 2 Circulating flue gas B is first subjected to dust removal and denitrification to control the dust particles in the flue gas ≤ 5mg / Nm 3 , NOx ≤ 50mg / Nm 3 , and then the SO in the flue gas is desulfurized 2 Controlled ≤ 5mg / Nm 3 , and then washed with water to reduce the flue gas temperature to ≤ 40°C, the water content in the flue gas is reduced to ≤ 10%, and the CO 2 Wet basis concentration ≥ 80%, and then it is divided into two paths to enter the all-oxygen combustion cement clinker production system and the carbon capture and purification system.

[0071] As a preferred embodiment, the CO entering the all-oxygen combustion cement clinker production system 2 Circulating flue gas B is first preheated to ≥ 60°C.

[0072] As a preferred embodiment, the O discharged from the first stage 101 of the cooler 2 / CO 2 The mixed gas is used as the secondary air g2 and the tertiary air g3 respectively. The secondary air g2 is introduced into the rotary kiln 2, and the tertiary air g3 is introduced into the decomposition furnace 3. The CO 2 Circulating flue gas B is used as the fourth air g4 and introduced into the bottom of the preheater. CO 2 The circulating flue gas is used as the fourth air g4 and introduced into the preheater, which can be used as a control means to reduce the raw material decomposition temperature under the high CO 2 Partial pressure and avoid the problem of scaling and blockage in the last-stage cyclone of the preheater due to the increase in the raw material decomposition temperature and the lagging combustion of the fuel.

[0073] Among them, the O in the secondary air g2 and the tertiary air g3 2 The concentration is 30% - 70%; the CO in the fourth air g4 2 Dry basis concentration 75 - 85%, O 2 The concentration is less than 5%.

[0074] The CO discharged from the air outlet of the cyclone separator at the top of the preheater 2 The CO in the circulating flue gas B 2The dry basis concentration is 75 - 85%, the temperature range is 300 - 400 °C, and the water content is 20% - 25%.

[0075] The flue gas generated in the all - oxygen combustion system is in the opposite direction to the material flow direction. In the all - oxygen combustion environment, the CO generated by fuel combustion and raw meal decomposition 2 The recycled flue gas serves as the main cooling medium of the cooler. The combustion - supporting gas used in the all - oxygen combustion system is high - concentration oxygen A, and the oxygen concentration obtained by the oxygen - making system is ≥90%, O 2 Except for a small amount introduced as the primary air into the burners set in the all - oxygen combustion decomposition furnace 3 and the rotary kiln 2, the remaining O 2 Is introduced into the all - oxygen combustion system from the cooler air chamber, and after exchanging heat with the hot clinker in the cooler, it enters the rotary kiln 2 and the all - oxygen combustion decomposition furnace 3 respectively as the secondary air g2 and the tertiary air g3 by the cooler 1.

[0076] The CO discharged from the all - oxygen combustion pre - heater 2 The recycled flue gas B is discharged through the air outlet of the cyclone separator at the top of the pre - heater. The CO after being pretreated by the flue gas pretreatment system 2 The recycled flue gas B is divided into two paths. One path enters the cooler as the cooling medium; the remaining CO 2 The recycled flue gas B enters the carbon capture and purification system.

[0077] The CO that enters the cooler as the cooling medium 2 The recycled flue gas B, the first path is combined with high - concentration O 2 To enter the first stage 101 of the cooler; the second path enters the second stage 102 of the cooler as the clinker cooling gas.

[0078] The CO that enters the carbon capture and purification system 2 The recycled flue gas B meets the process feed gas inlet conditions of the vacuum pressure swing adsorption system after pre - cooling and water removal. The vacuum pressure swing adsorption system purifies the CO gas through adsorption, equal - pressure reduction, vacuum pumping, reflux flushing, equal - pressure increase, and final increase cyclic steps 2 The gas obtained, the volume fraction of CO in the gas 2 Is 85 - 97%;

[0079] The concentrated CO 2 The flue gas is pressurized to the pressure required for the rectification process, and after three - stage deep impurity removal, it enters the rectification system through low - temperature liquefaction. The liquid product with a CO concentration ≥99.5% is obtained at the bottom of the rectification tower 1901 and enters the liquefied product storage tank 1903. The exhaust gas discharged from the top of the rectification tower is depressurized, exchanges heat with the refrigerating machine to recover the cold energy, and then is mixed with the feed gas of the vacuum pressure swing adsorption system to complete the pressure swing adsorption concentration process in the tower, improving the CO 2 Recovery rate. 2 Recovery rate.

[0080] During the concentration process of the vacuum pressure swing adsorption system, the light component gas is discharged after the volatile organic compounds are removed in the waste gas treatment system.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features, and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A system for low-energy carbon capture and purification of full-system oxyfuel combustion cement kiln flue gas, comprising a full-system oxyfuel combustion cement clinker production system and a carbon capture and purification system; the full-system oxyfuel combustion cement clinker production system comprises a preheater, a decomposition furnace, a kiln tail smoke chamber, a rotary kiln, and a cooler connected in sequence, characterized in that: The top air outlet of the preheater is respectively connected to the first two cooling medium inlets of the cooler and the carbon capture and purification system, and the top air outlet of the preheater discharges CO2 circulating flue gas with a dry basis CO2 concentration of 75-85%; The carbon capture and purification system comprises a precooler, a steam-water separator, a first booster fan, a vacuum pressure swing adsorption system, a second booster fan, a flue gas deep purification system, a refrigerator and a distillation system. The precooler, the steam-water separator, the first booster fan and the vacuum pressure swing adsorption system are connected in sequence. The external exhaust outlet of the vacuum pressure swing adsorption recovery system is connected to the waste gas treatment system. The volume fraction of CO2 in the gas recovered by the vacuum pressure swing adsorption system is 85-97%. The recovery gas outlet of the vacuum pressure swing adsorption system is connected to the second booster fan, the flue gas deep purification system, the refrigerator and the distillation system in sequence. The flue gas deep purification system comprises a denitration bed, a drying bed and an adsorption bed connected in sequence. The distillation system comprises a distillation tower, a reboiler and a liquefied product storage tank. The purified gas outlet of the refrigerator is connected to the inlet of the distillation tower. The gas outlet of the distillation tower is connected to the cooling gas inlet of the refrigerator through multi-stage decompression. The cooling gas outlet of the refrigerator is connected to the inlet of the vacuum pressure swing adsorption system. The liquid outlet of the distillation tower is connected to the reboiler and the liquefied product storage tank in sequence.

2. The system for low-energy carbon capture and purification of cement kiln flue gas by full-oxygen combustion according to claim 1 is characterized in that: A flue gas pretreatment system is arranged on the pipeline of the air outlet at the top of the preheater, and the flue gas pretreatment system includes a dust removal and denitrification device, a wet desulfurization device, and a flue gas water washing system which are arranged in sequence. The flue gas water washing system includes a water storage tank, a water washing pump, and a flue gas water washing tower. The outlet of the wet desulfurization device is connected to the air inlet of the flue gas water washing tower, the water storage tank is connected to the water inlet of the flue gas water washing tower through the water washing pump, the water outlet of the flue gas water washing tower is connected to the inlet of the water washing pump, the air outlet of the flue gas water washing tower is respectively connected to the circulating flue gas pipeline and the carbon capture and purification system, and the circulating flue gas pipeline is respectively connected to the first two cooling medium inlets of the cooler.

3. The system for low-energy carbon capture and purification of cement kiln flue gas by full-system oxyfuel combustion according to claim 2 is characterized in that: The circulating flue gas duct is provided with a flue gas preheater for preheating the circulating flue gas to a temperature above the dew point. The circulating flue gas duct is made of corrosion-resistant stainless steel, and an insulation layer is provided on the outside of the duct.

4. The system for low-energy carbon capture and purification of cement kiln flue gas by full-oxygen combustion according to claim 1 is characterized in that: The cooler is divided into three sections from the clinker inlet to the outlet, which are the first section of the cooler, the second section of the cooler and the third section of the cooler in sequence; the air outlet of the top cyclone separator of the preheater is connected to the air inlet of the first section of the cooler and the air inlet of the second section of the cooler, and a mixed gas of high-concentration O2 and CO2 circulating flue gas is introduced into the air inlet of the first section of the cooler. The secondary air intake and the tertiary air intake of the cooler are located in the first section of the cooler and are connected to the rotary kiln and the decomposition furnace respectively; the air inlet of the second section of the cooler only introduces CO2 circulating flue gas, and the quaternary air intake is located in the second section of the cooler and is connected to the inlet of the last stage cyclone of the preheater; a central roller crusher is arranged between the second section and the third section of the cooler, and the steam generated by indirect drying of the fuel is introduced into the wind chamber at the bottom of the central roller crusher.

5. The system for low-energy carbon capture and purification of cement kiln flue gas by full-system oxyfuel combustion according to claim 4 is characterized in that: A first resistance baffle is arranged between the first section and the second section of the cooler to reduce the blowby of the O2 / CO2 mixed gas in the first section of the cooler into the second section of the cooler; a second resistance baffle is arranged between the second section and the third section of the cooler; the height of the bottom ends of the first resistance baffle and the second resistance baffle and the gap with the corresponding cooler material bed are ≤300mm, and the first resistance baffle and the second resistance baffle are rotating movable baffles.

6. The system for low-energy carbon capture and purification of cement kiln flue gas by full-system oxyfuel combustion according to claim 4 is characterized in that: A high-concentration oxygen inlet is arranged on the channel at the air inlet of the first section of the cooler.

7. The system for low-energy carbon capture and purification of cement kiln flue gas by full-oxygen combustion according to claim 1 is characterized in that: The decomposition furnace is provided with a tertiary air inlet, a raw meal feeding point and a fuel feeding point. The tertiary air inlet is located in the middle and lower part of the decomposition furnace. At least one raw meal feeding point and one fuel feeding point are arranged between the lower part of the tertiary air inlet and the constriction at the bottom of the decomposition furnace, and the raw meal feeding point is located above the fuel feeding point.

8. A method for low-energy carbon capture and purification of flue gas from a cement kiln using full oxygen combustion in a whole system, based on the system for low-energy carbon capture and purification of flue gas from a cement kiln using full oxygen combustion in a whole system as claimed in any one of claims 1 to 7, characterized in that: The steps include: The raw meal is fed into the oxyfuel combustion preheater, where the raw meal is heat exchanged with the flue gas and the gas-solid is separated to preheat the raw meal to the decomposition temperature; The preheated raw meal enters the full oxygen combustion decomposition furnace, and the heat released by the fuel combustion is used for the raw meal in the decomposition furnace to absorb heat and decompose to obtain calcined raw meal; the calcined raw meal enters the rotary kiln for calcination to obtain hot clinker; the hot clinker is cooled in the cooler to obtain cement clinker; The CO2 circulating flue gas generated by fuel combustion and raw material decomposition enters the preheater, and the low-temperature flue gas after heat exchange is discharged through the air outlet of the cyclone separator at the top of the preheater; The CO2 circulating flue gas discharged from the outlet of the cyclone separator at the top of the preheater is divided into two paths. One path enters the oxyfuel combustion cement clinker production system as a cooling medium and enters the cooler. The other path enters the carbon capture and purification system. The CO2 circulating flue gas entering the carbon capture and purification system is pre-cooled to 0-10°C, and free water is separated from the gas and water, and then enters the vacuum pressure swing adsorption system to concentrate and recover the CO2. The CO2 concentration range of the vacuum pressure swing adsorption system is 85-97%; the concentrated and recovered CO2-rich gas enters the flue gas deep purification system after pressurization, and is deeply purified by denitrification, drying and adsorption in sequence. The purified flue gas is cooled to -15--35°C by a refrigerator and then introduced into a distillation tower; the distillation tower discharges light component impurities and non-condensable gases such as H2, CH4, CO, O2, N2 in the flue gas from the top of the distillation tower, and is used as cooling gas for the refrigerator after multi-stage decompression. After heat exchange and recovery of cold, it enters the vacuum pressure swing adsorption system to control the CO2 concentration in the exhaust gas outside the vacuum pressure swing adsorption system to ≤20%; the liquid enters the liquefied product storage tank for storage, and the CO2 purity in the liquid product is ≥99.5%.

9. The method for low-energy carbon capture and purification of cement kiln flue gas by full-system oxyfuel combustion according to claim 8, characterized in that: The CO2 circulating flue gas discharged from the outlet of the cyclone separator at the top of the preheater is first subjected to dust removal and denitrification to control the dust particles in the flue gas to ≤5mg / Nm 3 、NOx≤50mg / Nm 3 After desulfurization, the SO2 in the flue gas is controlled to ≤5mg / Nm 3 , and then washed with water to reduce the flue gas temperature to ≤40℃, the water content in the flue gas to ≤10%, and the CO2 wet basis concentration to ≥80%. After that, it is divided into two routes to enter the full oxygen combustion cement clinker production system and the carbon capture and purification system.

10. The method for low-energy carbon capture and purification of cement kiln flue gas by full-system oxy-fuel combustion according to claim 8, characterized in that: The CO2 circulating flue gas entering the oxy-fuel combustion cement clinker production system is first preheated to ≥60℃.

11. The method for low-energy carbon capture and purification of cement kiln flue gas by full-system oxy-fuel combustion according to claim 8, characterized in that: The O2 / CO2 mixed gas out of the first section of the cooler is used as secondary air and tertiary air respectively. The secondary air is introduced into the rotary kiln, and the tertiary air is introduced into the decomposition furnace. The CO2 circulating flue gas out of the second section of the cooler is introduced into the bottom of the preheater as quaternary air.

12. The method for low-energy carbon capture and purification of cement kiln flue gas by full-system oxy-fuel combustion according to claim 11, characterized in that: The O2 concentration in the secondary air and the tertiary air is 30% to 70%; the CO2 dry basis concentration in the quaternary air is 75 to 85%, and the O2 concentration is less than 5%.

13. The method for low-energy carbon capture and purification of cement kiln flue gas by full-system oxy-fuel combustion according to claim 8, characterized in that: The CO2 circulating flue gas discharged from the air outlet of the cyclone separator at the top of the preheater has a CO2 dry basis concentration of 75-85%, a temperature range of 300-400° C., and a water content of 20%-25%.

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