Cement kiln system for coupling oxygen-enriched combustion with flue gas circulation enrichment and carbon dioxide capture

Abstract

The invention belongs to the field of efficient carbon emission reduction and carbon cyclic utilization, and discloses a cement kiln system for coupling oxygen-enriched combustion with flue gas cyclic enrichment and carbon dioxide capture. A grate cooler in the system adopts a three-section grate plate, a partition plate is arranged in the grate plate to form a three-section cavity, the first-section cavity and the second-section cavity are provided with mixed gas inlets for introducing mixed gas of oxygen-enriched gas and circulating flue gas, and the third-section cavity is provided with an air inlet; the oxygen supply system is communicated with related pipelines to provide oxygen-enriched gas for the cement kiln; the decomposing furnace comprises a main decomposing furnace and a pre-decomposing furnace and is special in structure and position; the flue gas circulating system comprises various parts, and the flow direction of flue gas is controlled according to the concentration of carbon dioxide. According to the invention, air mixing between secondary and tertiary air and hot air is avoided, so that the concentration of secondary and tertiary air oxygen-enriched gas can be independently controlled, the concentration of carbon dioxide in the cement kiln is improved through flue gas circulation, the trapping difficulty and cost are reduced, meanwhile, the flow and temperature of the oxygen-enriched gas and circulating flue gas in the kiln can be accurately controlled, and the device is suitable for efficient and continuous production of cement clinker.

Description

Technical Field

[0001] The present invention belongs to the field of efficient carbon emission reduction and carbon recycling, and specifically relates to a cement kiln system of oxygen-enriched combustion coupled with flue gas recycling enrichment and carbon dioxide capture. Background Art

[0002] As one of the industries with high carbon dioxide emissions, the cement industry is actively taking low-carbon emission reduction measures. The coupling of cement kiln oxygen-enriched combustion with flue gas circulation enrichment and carbon dioxide capture technology is an emission reduction path with broad development prospects. Compared with air combustion, oxygen-enriched combustion can significantly reduce the participation of nitrogen, thereby increasing the concentration of carbon dioxide in the flue gas at the kiln tail. After coupling the flue gas circulation, carbon dioxide continues to circulate and enrich in the cement kiln system, and the concentration gradually increases to 80%. The high-concentration carbon dioxide is recovered through the kiln tail capture device, which can improve the efficiency of carbon dioxide capture and reduce the capture cost, thereby achieving efficient and low-cost carbon dioxide emission reduction.

[0003] At present, the use of oxygen-enriched combustion technology in the cement industry is limited to primary air oxygen enrichment. There is no industrial application example for secondary and tertiary air oxygen enrichment. However, secondary and tertiary air oxygen enrichment has the advantages of improving combustion efficiency, improving clinker quality and reducing coal consumption, so secondary and tertiary air oxygen enrichment is very necessary. At the same time, secondary and tertiary air oxygen enrichment coupling circulating flue gas enters the cement kiln system through the high-temperature clinker cooling zone of the grate cooler, which is a very innovative solution. Unfortunately, there is an unbalanced problem of fan air pulling in the grate cooler, which makes it easy to mix and cross-wind between the secondary and tertiary air generated by heat exchange in the high-temperature section and the hot air exchanged in the medium and low temperature sections. This makes hot air containing nitrogen enter the cement kiln system through the secondary and tertiary air ducts, affecting the oxygen-enriched combustion conditions and reducing the circulating enrichment concentration of carbon dioxide in the kiln. It is also difficult to achieve the differentiated control of the preset oxygen-enriched gas concentration and flue gas circulation volume in the secondary and tertiary air ducts, so improving the structure of the grate cooler has become the key to implementing this technology. Summary of the invention

[0004] The purpose of the present invention is to provide a cement kiln system with oxygen-enriched combustion coupled with flue gas circulation enrichment and carbon dioxide capture, so as to solve the technical problems in the prior art that mixing and cross-winding easily occurs between the secondary air, the tertiary air and the hot air for heat exchange in the medium and low temperature sections, making it difficult to complete the oxygen enrichment transformation of the secondary and tertiary air with different concentrations, and the low carbon dioxide concentration in the kiln making it difficult to capture.

[0005] The cement kiln system for oxygen-enriched combustion coupled with flue gas circulation enrichment and carbon dioxide capture comprises an oxygen supply system, a grate cooler (3), a rotary kiln (4), a decomposition furnace, a preheater (7), a flue gas circulation system and a carbon dioxide capture system; the grate cooler (3) adopts a three-stage clinker conveying grate plate, and a partition (306) is provided in the grate cooler (3) to separate the upper part of the space where the three-stage grate plates are located to form a corresponding first cavity, a second cavity and a third cavity, wherein a mixed gas inlet is provided below both the first cavity and the second cavity, and the mixed gas inlet inputs a mixed gas composed of oxygen-enriched gas and kiln tail circulating flue gas through a mixed gas pipeline (304), and the third cavity is provided with an air inlet (305) for inputting conventional air, and the first cavity is provided with a secondary gas pipeline (306) to input a mixed gas composed of oxygen-enriched gas and kiln tail circulating flue gas, and the third cavity is provided with an air inlet (305) for inputting conventional air, and the first cavity is provided with a secondary gas pipeline (306) to input a mixed gas composed of oxygen-enriched gas and kiln tail circulating flue gas, and the third cavity is provided with an air inlet (305) for inputting conventional air, and the first cavity is provided with a secondary gas pipeline (306) to input a mixed gas composed of oxygen-enriched gas and kiln tail circulating flue gas, and the third cavity is provided with a secondary gas pipeline (306) to input a mixed gas composed of oxygen-enriched gas and kiln tail circulating flue gas ... The air channel (307) is connected to the kiln head of the rotary kiln (4); the second section cavity is connected to the tertiary air duct (24) through the exhaust chamber (23); the oxygen supply system is connected to the burner primary air duct (25), the mixed gas ducts (304) on the first section cavity and the second section cavity through pipelines; the burner primary air duct (25) is located at the kiln head of the rotary kiln (4); the tertiary air duct (24) is connected to the decomposition furnace; the decomposition furnace is connected to the preheater (7) through a pipeline; the preheater (7) is connected to the flue gas circulation system through a pipeline; the flue gas circulation system is connected to the mixing chamber (9), the two mixed gas ducts (304) on the grate cooler (3) and the carbon dioxide capture system through pipelines; the mixing chamber (9) is connected to the decomposition furnace.

[0006] Preferably, the mixed gas pipeline (304) is a sleeve double-channel structure, including an external pipeline (3041) and an internal pipeline (3402), the external pipeline (3041) is connected to the flue gas circulation system for circulating the kiln tail circulating flue gas, the internal pipeline (3402) is connected to the oxygen supply system for circulating oxygen-rich gas, and a spiral guide structure (3043) is provided in the internal pipeline (3402).

[0007] Preferably, the oxygen supply system comprises an oxygen generator (1) and an oxygen diverter (2); the oxygen generator (1) is connected to the oxygen diverter (2) via a pipeline; the oxygen diverter (2) is respectively connected to the primary air duct (25) of the burner and the internal duct (3402) of the two mixed gas ducts (304) via three oxygen supply pipelines; the oxygen-enriched diverter diverts oxygen and mixes it with air to form three oxygen-enriched gases with different concentrations, which respectively enter the primary air system, the secondary air system and the tertiary air system.

[0008] Preferably, the decomposition furnace comprises a main decomposition furnace (6) and a pre-decomposition furnace (5), the pre-decomposition furnace (5) being mounted externally on the main decomposition furnace (6), the tertiary air duct (24) being connected to the pre-decomposition furnace (5) and receiving tertiary air containing oxygen-rich gas and recycled flue gas from the exhaust chamber (23); the pre-decomposition furnace (5) comprising a primary combustion zone (503), a reburning zone (504) and a coke chamber (505), the primary combustion zone (503) being arranged as an inclined box structure, the upper end of the primary combustion zone (503) being provided with an alternative fuel and mixed gas inlet (501) and the lower end being connected to the reburning zone (504), the reburning zone (504) being provided with a tertiary air inlet (502) at one end and a gas outlet (508) at the other end, the bottom of the reburning zone (504) being connected to the coke chamber (505), and the bottom of the coke chamber (505) being an inclined box structure.

[0009] Preferably, the pre-decomposition furnace (5) is specifically arranged above the first cone of the main decomposition furnace (6), and the gas outlet (508) is arranged at an eccentric position of the central axis of the decomposition furnace and is located above the first cone of the main decomposition furnace (6); the oxygen-enriched tertiary air carries the pyrolysis gas and part of the small-particle coke, and is sent into the furnace body through the tangential direction of the main decomposition furnace (6), forming a spiral airflow in the furnace body.

[0010] Preferably, the flue gas circulation system comprises a flue gas detection control valve (8), a fan 1 (14), a fan 2 (15), an air mixing chamber (9), a flue gas flow regulating valve 4 (21), a kiln tail chimney (22) and a fan 3 (16), wherein the flue gas detection control valve (8) is provided with an air inlet and two air outlets, wherein the air inlet is connected to the preheater (7) through a pipeline, and the two air outlets are respectively connected to the fan 1 (14) and the fan 2 (15) through pipelines, wherein the fan The second fan (15) is connected to the inlet of the kiln tail chimney (22) through a pipeline, and the outlet of the kiln tail chimney (22) is connected to the fourth fan (17) through a pipeline. The air outlet of the fourth fan (17) is connected to a kiln tail flue gas circulation pipeline with a branch pipe. The two branches of the kiln tail flue gas circulation pipeline are respectively connected to the external pipelines (3041) of the two mixed gas pipelines (304), and the two branches are respectively provided with a flue gas flow regulating valve one (18) and a flue gas flow regulating valve two (19).

[0011] Preferably, the smoke flow regulating valve 1 (18) is located on the pipeline for conveying the circulating smoke from the kiln tail to the first section cavity, and is used to control the total air flow of the secondary air; the smoke flow regulating valve 2 (19) is located on the pipeline for conveying the circulating smoke from the kiln tail to the second section cavity; the smoke flow regulating valve 3 (20) is located on the pipeline for conveying the circulating smoke from the fan 1 (14) to the mixing chamber (9); the smoke flow regulating valve 2 (19) and the smoke flow regulating valve 3 (20) are used together to control the total air flow of the tertiary air mixture in the cement kiln system; the smoke flow regulating valve 4 (21) is located on the pipeline for conveying the tertiary air from the exhaust chamber (23) to the mixing chamber (9); the smoke flow regulating valve 4 (21) and the smoke flow regulating valve 3 (20) cooperate to control the temperature in the mixing chamber (9) and the air flow of the circulating smoke entering the mixing chamber (9).

[0012] Preferably, the cement kiln system further comprises a boiler (10), an outlet of the smoke detection control valve (8) is connected to the boiler (10) via a pipeline, and the outlet of the boiler (10) is respectively connected to the second fan (15) and the carbon dioxide capture system; the carbon dioxide capture system comprises a primary cyclone dust collector (11), a capture device (12) and a carbon dioxide storage tank (13), and the outlet of the boiler (10) is connected to the primary cyclone dust collector (11) and is connected to the capture device (12) and the carbon dioxide storage tank (13) in sequence via a pipeline.

[0013] The present invention has the following advantages: On the one hand, the present invention realizes the separation of the space where each section of the grate plate in the grate cooler is located in the top exhaust part, forming a multi-section cavity, avoiding the problem of mixed wind between the secondary and tertiary air generated by the heat exchange in the high-temperature section of the grate cooler and the hot air in the medium and low temperature sections due to the problem of unbalanced air pulling by the fan, ensuring that the secondary and tertiary air can achieve different concentrations of oxygen enrichment. On the other hand, the flue gas circulation system is added, the carbon dioxide concentration in the cement kiln system is increased, and the difficulty and cost of capturing carbon dioxide are reduced. At the same time, the configured mixed gas pipeline can enhance the mixing effect and heat exchange efficiency of the oxygen-enriched gas and the direct current flue gas by forming a swirl of the oxygen-enriched gas.

[0014] The decomposition furnace structure adopted by the present invention cooperates with the tertiary air system, so that the oxygen-rich tertiary air carries the pyrolysis gas and part of the small-particle coke, and is sent into the furnace body through the tangential direction of the main decomposition furnace (i.e. the circumferential tangent of the furnace body cross section here), forming a spiral airflow in the furnace body, fully stirring and mixing the alternative fuel, coal powder and materials, achieving rapid and uniform distribution of the solid phase and gas phase, and strengthening the combustion effect. Since all the tertiary air formed by the oxygen-rich gas first passes through the pre-decomposition furnace, the present invention, on the one hand, increases the amount of gas supplied to the pre-decomposition furnace, and on the other hand, since the combustion-supporting gas is oxygen-rich gas, it can quickly preheat the alternative fuel or pre-burn the alternative fuel, thereby increasing the disposal amount of the alternative fuel in the pre-decomposition furnace.

[0015] The present invention controls the flow direction and flow rate of circulating flue gas through a fan and a flue gas detection control valve. The fan provides traction for the flue gas to enter the circulation system. The flue gas detection control valve controls whether the flue gas enters the circulation enrichment system or the carbon dioxide capture system according to the carbon dioxide concentration in the flue gas. The present invention also realizes the control of the temperature in the system and the control of the tertiary air flow rate through the setting of the flue gas flow regulating valve, thereby meeting the gas volume requirements for secondary and tertiary air in actual production and ensuring the stable operation of the entire system. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic flow diagram of a cement kiln system of oxygen-enriched combustion coupled with flue gas circulation enrichment and carbon dioxide capture according to the present invention. In the figure, the dotted arrows represent the transmission line of the oxygen-enriched gas, and the solid arrows represent the transmission line of the general flue gas.

[0017] Figure 2 for Figure 1 Schematic diagram of the structure of the grate cooler in the structure shown.

[0018] Figure 3 for Figure 2 Structural schematic diagram of the mixed gas pipeline in the structure shown.

[0019] Figure 4 for Figure 3 Schematic diagram of the structure of the spiral guide structure in the structure shown.

[0020] Figure 5 for Figure 1 Schematic diagram of the structure of the pre-decomposition furnace in the structure shown.

[0021] The reference numerals in the drawings of the specification include: 1. oxygen production device, 2. oxygen flow distribution device, 3. grate cooler, 301. first grate plate, 302. second grate plate, 303. third grate plate, 304. mixed gas pipeline, 3041. external pipeline, 3042. internal pipeline, 3043. spiral guide structure, 305. air inlet, 306. partition, 307. secondary air channel, 308. tertiary air channel, 309. roller crusher, 4. rotary kiln, 5. precalciner, 501. alternative fuel and mixed gas inlet, 502. tertiary air inlet, 503. primary combustion zone, 504. reburning zone, 505. coke chamber, 506. , mobile slag pusher, 507, air cannon, 508, gas outlet, 509, coke outlet, 510, pressure sensor, 6, main decomposition furnace, 7, preheater, 8, flue gas detection control valve, 9, air mixing chamber, 10, boiler, 11, primary cyclone dust collector, 12, capture device, 13, carbon dioxide storage tank, 14, fan one, 15, fan two, 16, fan three, 17, fan four, 18, flue gas flow regulating valve one, 19, flue gas flow regulating valve two, 20, flue gas flow regulating valve three, 21, flue gas flow regulating valve four, 22, kiln tail chimney, 23, exhaust chamber, 24, tertiary air duct, 25, burner primary air duct. DETAILED DESCRIPTION

[0022] The specific implementation modes of the present invention are further explained in detail below by describing the embodiments with reference to the accompanying drawings, so as to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention.

[0023] like Figures 1 to 5As shown, the present invention provides a cement kiln system of oxygen-enriched combustion coupled with flue gas circulation enrichment and carbon dioxide capture, comprising an oxygen supply system, a grate cooler 3, a rotary kiln 4, a decomposition furnace, a preheater 7, a flue gas circulation system and a carbon dioxide capture system; the grate cooler 3 adopts a three-stage clinker conveying grate plate, and a partition 306 is provided in the grate cooler 3 to separate the upper part of the space where the three-stage grate plates are located to form a corresponding first cavity, a second cavity and a third cavity, wherein a mixed gas inlet is provided below both the first cavity and the second cavity, and the mixed gas inlet inputs a mixed gas composed of oxygen-enriched gas and kiln tail circulating flue gas through a mixed gas pipeline 304, and the third cavity is provided with an air inlet 305 for inputting conventional air, The first section cavity is connected to the kiln head of the rotary kiln 4 through the secondary air channel 307, the second section cavity is connected to the tertiary air duct 24 through the exhaust chamber 23, the oxygen supply system is connected to the burner primary air duct 25, the mixed gas duct 304 on the first section cavity and the second section cavity through pipelines, the burner primary air duct 25 is located at the kiln head of the rotary kiln 4, the tertiary air duct 24 is connected to the decomposition furnace, the decomposition furnace is connected to the preheater 7 through a pipeline, the preheater 7 is connected to the flue gas circulation system through a pipeline, the flue gas circulation system is respectively connected to the mixing chamber 9, the two mixed gas ducts 304 on the grate cooler 3 and the carbon dioxide capture system through pipelines, and the mixing chamber 9 is connected to the decomposition furnace.

[0024] The mixed gas pipeline 304 is a sleeve double-channel structure, including an external pipeline 3041 and an internal pipeline 3402. The external pipeline 3041 is connected to the flue gas circulation system for circulating the kiln tail circulating flue gas, and the internal pipeline 3402 is connected to the oxygen supply system for circulating the oxygen-enriched gas. A spiral guide structure 3043 is provided in the internal pipeline 3402. The spiral guide structure 3043 provides a swirl path for the oxygen-enriched gas, thereby enhancing the mixing effect of the oxygen-enriched gas and the direct current flue gas and the heat exchange efficiency thereof.

[0025] The oxygen supply system includes an oxygen generator 1 and an oxygen diverter 2. The oxygen generator 1 is connected to the oxygen diverter 2 through a pipeline. The oxygen diverter 2 is connected to the primary air duct 25 of the burner and the internal pipe 3402 of the two mixed gas pipes 304 through three oxygen supply pipes. The oxygen-enriched diverter diverts oxygen and mixes it with air to form three oxygen-enriched gases with different concentrations, which enter the primary air system, the secondary air system and the tertiary air system respectively. The primary air oxygen concentration range is 25%-40%, the secondary air oxygen concentration range is 25%-35%, and the tertiary air oxygen concentration range is 30%-40%. The kiln head air excess coefficient is controlled to 1.1-1.3, and the kiln tail air excess coefficient is set to 1.1-1.2. Such a setting can minimize the flue gas heat loss caused by the gas volume input to the system under the premise of ensuring sufficient oxygen supply for fuel combustion and the gas velocity requirements of the decomposition furnace, and can also control the outlet oxygen concentration and reduce the impact of oxygen-enriched combustion on pollutant emissions.

[0026] The clinker enters the grate cooler 3 from the kiln head and is transported by the three-stage clinker conveying grate plate. It first passes through the first-stage grate plate 301, and is cooled and heat-exchanged with the mixed gas composed of oxygen-rich gas and kiln tail circulating flue gas. After the heat exchange, the mixed gas in the first-stage cavity enters the rotary kiln 4 as secondary air; then, the clinker is crushed by the roller crusher 309 and falls to the second-stage grate plate 302. After heat exchange with the mixed gas (including oxygen-rich gas and kiln tail circulating flue gas) input into this space, the mixed gas in the second-stage cavity is output from the tertiary air channel 308 and enters the tertiary air duct 24 through the exhaust chamber 23; the clinker is crushed by the roller crusher 309 and enters the third-stage grate plate 303. The clinker entering the third-stage cavity is medium-low temperature clinker, and conventional air heat exchange is adopted. The hot air after heat exchange enters the waste heat power generation system. In the structure of the grate cooler 3, the upper spaces of each section of the grate plate are isolated from each other. The secondary and tertiary air, as well as the tertiary air and the medium and low temperature hot air can be completely independent by cooperating with the kiln head fan to prevent cross-wind. Finally, the clinker temperature at the tail outlet of the grate cooler 3 is about 100°C.

[0027] The decomposition furnace includes a main decomposition furnace 6 and a pre-decomposition furnace 5. The pre-decomposition furnace 5 is externally mounted on the main decomposition furnace 6. The tertiary air duct 24 is connected to the pre-decomposition furnace 5 and receives tertiary air containing oxygen-rich gas and circulating flue gas from the exhaust chamber 23, so that the interior of the alternative fuel can be fully preheated and burned, thereby reducing the combustion pressure in the decomposition furnace. The pre-decomposition furnace 5 includes a primary combustion zone 503, a reburning zone 504 and a coke chamber 505. The primary combustion zone 503 is set as an inclined box structure. The upper end of the primary combustion zone 503 is provided with an alternative fuel and mixed gas inlet 501 and the lower end is connected to the reburning zone 504. The reburning zone 504 is provided with a tertiary air inlet 502 at one end and a gas outlet 508 at the other end. The bottom of the reburning zone 504 is connected to the coke chamber 505, and the bottom of the coke chamber 505 is an inclined box structure. The box body of the primary combustion zone 503 has an inclination angle between 20° and 30°, and the box body of the coke chamber 505 has an inclination angle between 10° and 15°. A mobile slag pusher 506 is provided at one end of the coke chamber 505 and a coke outlet 509 is provided at the other end. A pressure sensor 510 and an air cannon 507 are provided at the bottom of the coke chamber 505.

[0028] The precalcining furnace 5 is specifically arranged above the first cone of the main calcining furnace 6, and the gas outlet 508 is arranged at an eccentric position of the central axis of the calcining furnace and is located 2m above the first cone of the main calcining furnace 6. The purpose of such arrangement is to allow the oxygen-enriched tertiary air to carry pyrolysis gas and part of small-particle coke, and to be sent into the furnace body through the tangential direction of the main calcining furnace 6 (i.e. the tangential direction of the circumference of the furnace body section here), so as to form a spiral airflow in the main calcining furnace 6, fully stir and mix the alternative fuel, coal powder and materials, realize the rapid and uniform distribution of the solid phase and gas phase, and strengthen the combustion effect.

[0029] The flue gas circulation system inputs a mixed gas consisting of circulating flue gas and a certain amount of tertiary air into the precalciner 5 through a pipeline, and the mixed gas and the alternative fuel first enter the primary combustion zone 503 through the alternative fuel and mixed gas inlet 501. In the primary combustion zone 503, the alternative fuel is preheated and preliminarily burned; then the alternative fuel falls into the reburning zone 504, and the front end of the reburning zone 504 is connected to the tertiary air duct 24, and the alternative fuel is fully burned by the higher temperature tertiary air. The gas outlet 508 at the rear end of the reburning zone 504 is connected to the main calciner 6 to provide the high-temperature mixed gas provided by the combustion of the alternative fuel. The unburned coke and the fully preheated alternative fuel in the reburning zone 504 fall into the coke chamber 505. When the unburned alternative fuel accumulates at the bottom and the bottom pressure reaches the set value, the air cannon 507 is turned on, and the mobile slag pusher 506 is also started synchronously. The combination of the two pushes the coke and part of the unburned alternative fuel into the calciner.

[0030] The main decomposition furnace 6 is provided with four coal injection pipes, two of which are located in the cone area of ​​the main decomposition furnace 6, and two of which are located 3m above the cone of the main decomposition furnace 6. The coke outlet 509 of the pre-decomposition furnace 5 is arranged above the coal injection pipe in the cone area of ​​the decomposition furnace. The mobile slag pusher 506 spreads coke or unburned alternative fuel into the furnace of the decomposition furnace, and can fall on the spatial position where the coal powder burns violently, ensuring that the coke can be mixed with the coal powder and fully burned as soon as it enters the decomposition furnace. The innovation point of the above structure is that all the tertiary winds formed by the oxygen-rich gas first pass through the pre-decomposition furnace 5, so that on the one hand, the amount of gas supplied to the pre-decomposition furnace 5 is large, and on the other hand, since the combustion-supporting gas is oxygen-rich gas, the alternative fuel can be quickly preheated or pre-burned, thereby increasing the disposal amount of the alternative fuel in the pre-decomposition furnace 5.

[0031] The flue gas circulation system includes a flue gas detection control valve 8, a fan 14, a fan 2 15, an air mixing chamber 9, a kiln tail chimney 22 and a fan 3 16. The flue gas detection control valve 8 is provided with an air inlet and two air outlets. The air inlet is connected to the preheater 7 through a pipeline. The two air outlets are respectively connected to the fan 14 and the fan 2 15 through pipelines. The fan 2 15 is connected to the inlet of the kiln tail chimney 22 through a pipeline. The outlet of the kiln tail chimney 22 is connected to the fan 4 17 through a pipeline. The air outlet of the fan 4 17 is connected to a kiln tail flue gas circulation pipeline with branches. The two branches of the kiln tail flue gas circulation pipeline are respectively connected to the external pipelines 3041 of two mixed gas pipelines 304. The two branches are respectively provided with a flue gas flow regulating valve 1 18 and a flue gas flow regulating valve 2 19.

[0032] The cement kiln system of oxygen-enriched combustion coupled with flue gas circulation enrichment and carbon dioxide capture also includes a boiler 10, one outlet of the flue gas detection control valve 8 is connected to the boiler 10 through a pipeline, and the outlet of the boiler 10 is respectively connected to the fan 2 15 and the carbon dioxide capture system. The carbon dioxide capture system includes a primary cyclone dust collector 11, a capture device 12 and a carbon dioxide storage tank 13, and the outlet of the boiler 10 is connected to the primary cyclone dust collector 11 and is connected to the capture device 12 and the carbon dioxide storage tank 13 in sequence through a pipeline.

[0033] In the flue gas circulation system, when the concentration of carbon dioxide in the flue gas is lower than 80%, the exhaust fan 14 and the exhaust fan 2 15 are started to open the flue gas circulation channel. The exhaust fan 14 is started to allow the flue gas to enter the air mixing chamber 9 through the pipeline, and the exhaust fan 2 15 allows the flue gas to enter the kiln tail chimney 22 after coming out of the boiler 10. The exhaust volume of the exhaust fan 2 15 must ensure the stability of the gas volume of the entire circulation system. Taking a cement clinker production line with a daily output of 5,000 tons as an example, the exhaust volume of the exhaust fan 2 is at least 150,000 Nm 3 / h. When the carbon dioxide concentration exceeds 80%, fan one 14 and fan two 15 stop working and fan three 16 is used to start the air pulling, thereby opening the channel of the carbon dioxide capture system. The flue gas comes out of the boiler 10 and passes through the first-level cyclone dust collector and then enters the capture device 12. Note that the dust content at the outlet of the first-level cyclone dust collector is controlled to be less than 1g / m3, and the carbon dioxide captured by the capture device 12 is stored in the carbon dioxide storage tank 13. Fan four 17 is arranged on the pipeline after the chimney 22 at the kiln tail to provide traction for the circulating flue gas at the kiln tail to enter the grate cooler 3. Among the above-mentioned fans, fan one 14, fan two 15 and fan three 16 are all high-temperature fans with an upper temperature resistance of 450-500℃, while fan four 17 is a normal temperature fan.

[0034] The system is equipped with four flue gas flow regulating valves to ensure accurate air flow and temperature control during the production process to meet the needs of efficient and continuous cement clinker production. The flue gas flow regulating valve 18 is located on the pipeline that transports the circulating flue gas from the kiln tail to the first section of the cavity. The first section of the cavity delivers secondary air to the kiln head of the rotary kiln 4 through the secondary air system. Therefore, the flue gas flow regulating valve 18 is used to control the total air flow of the secondary air. There are two aspects to the control factors of the secondary air: first, ensure that the gas volume of oxygen-enriched gas and the mixed flue gas from the kiln tail meets the continuous production needs of the cement clinker production line. Taking a cement clinker production line with a daily output of 5,000 tons as an example, the total air flow of the secondary air needs to be maintained at 70,000 Nm 3 / h, while maintaining the oxygen-rich gas concentration in the secondary air in the range of 25%-35%; secondly, ensure that the temperature of the secondary air after heat exchange with the clinker is not lower than 1200℃, and the first stage clinker is cooled to below 1200℃.

[0035] The smoke flow regulating valve 2 19 is located on the pipeline for conveying the circulating smoke from the kiln tail to the second section cavity, and the smoke flow regulating valve 3 20 is located on the pipeline for conveying the circulating smoke from the fan 14 to the mixing chamber 9. The smoke flow regulating valve 2 19 and the smoke flow regulating valve 3 20 are used together to control the total gas flow of the tertiary air mixture in the cement kiln system. The smoke flow regulating valve 2 19 can control the gas flow of the tertiary air, while the smoke flow regulating valve 3 20 controls the gas flow of the circulating smoke mixed with the tertiary air. Taking a cement clinker production line with a daily output of 5,000 tons as an example, the smoke flow regulating valve 2 19 and the smoke flow regulating valve 3 20 cooperate to maintain the total gas flow of the tertiary air mixture at 100,000 Nm 3 / h, wherein the control factors of the flue gas flow regulating valve 219 also include maintaining the tertiary air temperature not lower than 1050°C, ensuring that the clinker in the second chamber is cooled to below 1050°C, and ensuring that the oxygen-rich gas content in the tertiary air is between 30% and 40%.

[0036] The flue gas flow regulating valve 4 21 is located on the pipeline for conveying tertiary air from the exhaust chamber 23 to the air mixing chamber 9, and the air mixing chamber 9 will also convey the mixed gas into the pre-decomposition furnace 5 after a part of the tertiary air is mixed with the circulating flue gas. The flue gas flow regulating valve 4 21 is used to control the air flow of the tertiary air in the exhaust chamber 23 entering the air mixing chamber 9. At the same time, the flue gas flow regulating valve 4 21 and the flue gas flow regulating valve 3 20 cooperate to control the temperature in the air mixing chamber 9 and the air flow of the circulating flue gas entering the air mixing chamber 9. The relevant control factors include: first, to keep the temperature in the air mixing chamber 9 between 550-850℃, and second, to ensure that the air flow of the circulating flue gas entering the air mixing chamber 9 is not less than one-third of the total air flow of the tertiary air, so as to ensure the smooth operation of the primary combustion zone 503 in the external pre-decomposition furnace 5.

[0037] The present invention is described above by way of example in conjunction with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the inventive concept and technical solution of the present invention, or the inventive concept and technical solution are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. Cement kiln system with oxygen-enriched combustion coupled with flue gas circulation enrichment and carbon dioxide capture, characterized by: The invention comprises an oxygen supply system, a grate cooler (3), a rotary kiln (4), a decomposition furnace, a preheater (7), a flue gas circulation system and a carbon dioxide capture system; the grate cooler (3) adopts a three-stage clinker conveying grate plate, and a partition plate (306) is provided in the grate cooler (3) to separate the upper part of the space where the three-stage grate plates are located to form a corresponding first-stage cavity, a second-stage cavity and a third-stage cavity, wherein the first-stage cavity and the second-stage cavity are both provided with a mixed gas inlet below, and the mixed gas inlet inputs a mixed gas composed of oxygen-enriched gas and kiln tail circulating flue gas through a mixed gas pipeline (304), and the third-stage cavity is provided with an air inlet (305) for inputting conventional air, and the first-stage cavity is connected to the rotary kiln (4) through a secondary air channel (307). 4), the second section cavity is connected to the tertiary air duct (24) through the exhaust chamber (23), the oxygen supply system is connected to the burner primary air duct (25), the mixed gas duct (304) on the first section cavity and the second section cavity through pipelines, the burner primary air duct (25) is located at the kiln head of the rotary kiln (4), the tertiary air duct (24) is connected to the decomposition furnace, the decomposition furnace is connected to the preheater (7) through a pipeline, the preheater (7) is connected to the flue gas circulation system through a pipeline, the flue gas circulation system is connected to the mixing chamber (9), the two mixed gas ducts (304) on the grate cooler (3) and the carbon dioxide capture system through pipelines, and the mixing chamber (9) is connected to the decomposition furnace.

2. The cement kiln system of oxygen-enriched combustion coupled with flue gas circulation enrichment and carbon dioxide capture according to claim 1 is characterized in that: The mixed gas pipeline (304) is a sleeve double-channel structure, including an external pipeline (3041) and an internal pipeline (3402). The external pipeline (3041) is connected to the flue gas circulation system for circulating the kiln tail circulating flue gas, and the internal pipeline (3402) is connected to the oxygen supply system for circulating oxygen-rich gas. A spiral guide structure (3043) is provided in the internal pipeline (3402).

3. The cement kiln system of oxygen-enriched combustion coupled with flue gas circulation enrichment and carbon dioxide capture according to claim 1 is characterized in that: The oxygen supply system comprises an oxygen generator (1) and an oxygen flow splitter (2); the oxygen generator (1) is connected to the oxygen flow splitter (2) via a pipeline; the oxygen flow splitter (2) is respectively connected to the primary air pipeline (25) of the burner and the internal pipeline (3402) of the two mixed gas pipelines (304) via three oxygen supply pipelines; the oxygen-enriched flow splitter splits the oxygen and mixes it with air to form three oxygen-enriched gases with different concentrations, which respectively enter the primary air system, the secondary air system and the tertiary air system.

4. The cement kiln system of oxygen-enriched combustion coupled with flue gas circulation enrichment and carbon dioxide capture according to claim 1 is characterized in that: The decomposition furnace comprises a main decomposition furnace (6) and a pre-decomposition furnace (5), wherein the pre-decomposition furnace (5) is externally mounted on the main decomposition furnace (6), wherein the tertiary air duct (24) is connected to the pre-decomposition furnace (5) and receives tertiary air containing oxygen-rich gas and circulating flue gas from the exhaust chamber (23); the pre-decomposition furnace (5) comprises a primary combustion zone (503), a reburning zone (504) and a coke chamber (505), wherein the primary combustion zone (503) is arranged as an inclined box structure, wherein the upper end of the primary combustion zone (503) is provided with an inlet (501) for alternative fuel and mixed gas and the lower end is connected to the reburning zone (504), wherein the reburning zone (504) has a tertiary air inlet (502) at one end and a gas outlet (508) at the other end, wherein the bottom of the reburning zone (504) is connected to the coke chamber (505), and the bottom of the coke chamber (505) is an inclined box structure.

5. The cement kiln system of oxygen-enriched combustion coupled with flue gas circulation enrichment and carbon dioxide capture according to claim 4 is characterized in that: The pre-calcining furnace (5) is specifically arranged above the first cone of the main calcining furnace (6); the gas outlet (508) is arranged at an eccentric position of the central axis of the calcining furnace and is located above the first cone of the main calcining furnace (6); the oxygen-enriched tertiary air carries the pyrolysis gas and part of the small-particle coke and is sent into the furnace body through the tangential direction of the main calcining furnace (6), forming a spiral airflow in the furnace body.

6. The cement kiln system of oxygen-enriched combustion coupled with flue gas circulation enrichment and carbon dioxide capture according to claim 1 is characterized in that: The smoke circulation system comprises a smoke detection control valve (8), a fan 1 (14), a fan 2 (15), an air mixing chamber (9), a smoke flow regulating valve 4 (21), a kiln tail chimney (22) and a fan 3 (16), wherein the smoke detection control valve (8) is provided with an air inlet and two air outlets, wherein the air inlet is connected to the preheater (7) through a pipeline, and the two air outlets are respectively connected to the fan 1 (14) and the fan 2 (15) through pipelines, wherein the fan 2 (15) The inlet of the kiln tail chimney (22) is connected through a pipeline, and the outlet of the kiln tail chimney (22) is connected to the fan four (17) through a pipeline. The air outlet of the fan four (17) is connected to a kiln tail flue gas circulation pipeline with a branch pipe. The two branches of the kiln tail flue gas circulation pipeline are respectively connected to the external pipelines (3041) of the two mixed gas pipelines (304), and the two branches are respectively provided with a flue gas flow regulating valve one (18) and a flue gas flow regulating valve two (19).

7. The cement kiln system of oxygen-enriched combustion coupled with flue gas circulation enrichment and carbon dioxide capture according to claim 6 is characterized in that: The first smoke flow regulating valve (18) is located on the pipeline for conveying the circulating smoke from the kiln tail to the first section cavity, and is used to control the total gas flow of the secondary air; the second smoke flow regulating valve (19) is located on the pipeline for conveying the circulating smoke from the kiln tail to the second section cavity, and the third smoke flow regulating valve (20) is located on the pipeline for conveying the circulating smoke from the fan (14) to the mixing chamber (9), and the second smoke flow regulating valve (19) and the third smoke flow regulating valve (20) are used together to control the total gas flow of the tertiary air mixed gas in the cement kiln system; The smoke flow regulating valve four (21) is located on the pipeline for conveying tertiary air from the exhaust chamber (23) to the air mixing chamber (9). The smoke flow regulating valve four (21) and the smoke flow regulating valve three (20) cooperate to control the temperature in the air mixing chamber (9) and the air flow rate of the circulating smoke entering the air mixing chamber (9).

8. The cement kiln system of oxygen-enriched combustion coupled with flue gas circulation enrichment and carbon dioxide capture according to claim 1 is characterized in that: It also includes a boiler (10), one of the gas outlets of the smoke detection control valve (8) is connected to the boiler (10) through a pipeline, and the gas outlet of the boiler (10) is respectively connected to the second fan (15) and the carbon dioxide capture system; the carbon dioxide capture system includes a primary cyclone dust collector (11), a capture device (12) and a carbon dioxide storage tank (13), and the outlet of the boiler (10) is connected to the primary cyclone dust collector (11) and is connected to the capture device (12) and the carbon dioxide storage tank (13) in sequence through a pipeline.

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