Lime kiln system for independent circulation of carbon-rich flue gas

Abstract

The utility model discloses a lime kiln system for independent circulation of carbon-rich flue gas, which is characterized in that an indirect heat exchange mechanism of heat storage cold flue gas and cooling air is arranged between vertical hearths of a double-hearth lime kiln, so that the cooling air from a cooling section and calcining flue gas from a calcining section are separated from a connecting channel; on one hand, cooling airflow can be prevented from converging into calcining flue gas to dilute the concentration of carbon dioxide in the flue gas, on the other hand, high-temperature cooling air is subjected to waste heat absorption through heat storage cold flue gas and then returns to a combustion chamber for recycling, and cyclic enrichment of carbon dioxide and cyclic utilization of cooling waste heat can be achieved while the product quality is not affected; the device has the advantages of good production continuity, high production efficiency, strong system stability, high concentration of carbon dioxide in flue gas, easiness in trapping, low equipment maintenance cost and the like.

Description

TECHNICAL FIELD

[0001] The utility model relates to lime kiln carbon enrichment system, concretely relates to a kind of lime kiln system of carbon-rich flue gas independent circulation, belong to lime kiln carbon enrichment and capture technical field. BACKGROUND

[0002] Active lime is an important industrial raw material, widely used in steel industry, calcium carbide industry and alumina industry, and the demand is huge. In the past ten years, China's lime production has been growing continuously, and the domestic lime production reached 300 million tons in 2020, with CO2 emissions reaching more than 330 million tons, which is the key object of CO2 emission reduction and carbon capture in the industrial field.

[0003] Parallel heat storage type double-chamber lime vertical kiln (see Figure 1 ) is the most advanced type of industrial lime production equipment and mainstream kiln at present, which adopts double-chamber reversing heat storage technology, and has the advantages of high system energy efficiency, uniform product calcination and low pollution emission compared with rotary kiln and mechanized vertical kiln and other kiln types. However, the current conventional process of lime production produces tail-end flue gas with low CO2 concentration, generally below 20%, and the carbon capture cost is as high as more than 300 yuan / ton of CO2 due to the increase of carbon capture cost with the decrease of CO2 concentration in the capture source, which leads to the direct emission of tail gas into the atmosphere by most manufacturers, causing great resource waste and environmental pollution, so the too low CO2 concentration in the tail end greatly limits the large-scale application of carbon capture technology in lime kiln equipment.

[0004] In view of the above problems, technical personnel in the industry put forward a carbon front-end enrichment technology, that is, by reducing or eliminating other gas components in the flue gas to obtain high-concentration CO2 flue gas, thereby greatly reducing the tail-end carbon capture cost and realizing near-zero emission of lime production. The main technical feature of this method is to use circulating flue gas instead of cooling air to cool high-temperature lime, and to use pure oxygen + circulating flue gas calcination to obtain high-concentration CO2 flue gas. However, directly using high-concentration CO2 flue gas to cool high-temperature calcium oxide can easily cause reverse carbonation reaction between calcium oxide and CO2 to regenerate calcium carbonate, reducing the quality and yield of lime products. Indirect cooling methods also have the following disadvantages: first, indirect cooling requires a large number of cooling pipes to be distributed in the material, which can easily cause material accumulation and form a bridging effect, hindering the downward movement of the material and disrupting the continuity of production; second, indirect cooling can easily cause uneven heating in some areas, that is, the material near the cooling pipe cools faster, while the material farther away from the cooling pipe cools slower, resulting in local overheating of the outlet material or the consumption of more cooling resources to ensure that the temperature of all outlet materials meets the requirements; third, the cooling pipe is subjected to mechanical friction and thermal stress of high-temperature material in the furnace, which can easily crack, bend and deform, and needs to be replaced frequently, resulting in forced interruption of production, reduced production efficiency and high maintenance cost. Practical new content

[0005] In view of the problems of the existing carbon front-end enrichment technology, such as the reverse reaction affecting the product quality by using the direct cooling mode, the poor production continuity, the uneven cooling and the poor running stability by using the built-in cooling pipeline mode, the utility model provides a lime kiln system with independent circulation of carbon-rich flue gas, which separates the cooling air from the cooling section and the calcination flue gas from the calcination section at the annular passage (i.e. the hot flue gas connecting passage connecting the calcination chamber and the regenerative chamber), on the one hand, can avoid the dilution of the carbon dioxide concentration in the flue gas by the cooling air flow merging into the calcination flue gas, on the other hand, the high-temperature cooling air is absorbed by the regenerative cold flue gas and then returns to the combustion chamber for recycling, which can realize the recycling enrichment of carbon dioxide and the recycling utilization of the cooling waste heat without affecting the product quality, has the advantages of good production continuity, stable system operation and low equipment maintenance cost.

[0006] To achieve the above technical purpose, the technical scheme adopted by the utility model is as follows:

[0007] A lime kiln system with independent circulation of carbon-rich flue gas, the lime kiln system comprises a first vertical chamber, a second vertical chamber and an indirect heat exchanger. The first vertical chamber and the second vertical chamber are the same structure and both comprise a combustion cavity and a cooling cavity connected in series from top to bottom. A first hot flue gas passage is formed in the lower part of the side wall of the combustion cavity of the first vertical chamber, a first air passage is formed in the upper part of the side wall of the cooling cavity of the first vertical chamber, a first cold flue gas passage, a first material inlet, a first oxygen inlet and a first circulating flue gas inlet are further formed in the top of the combustion cavity of the first vertical chamber, and a first cooling gas inlet is further formed in the bottom of the cooling cavity of the first vertical chamber. A second hot flue gas passage is formed in the lower part of the side wall of the combustion cavity of the second vertical chamber, a second air passage is formed in the upper part of the side wall of the cooling cavity of the second vertical chamber, a second cold flue gas passage, a second material inlet, a second oxygen inlet and a second circulating flue gas inlet are further formed in the top of the combustion cavity of the second vertical chamber, and a second cooling gas inlet is further formed in the bottom of the cooling cavity of the second vertical chamber.

[0008] The indirect heat exchanger is arranged between the first vertical furnace and the second vertical furnace, and the indirect heat exchanger is provided with an air inlet, an air outlet, a flue gas inlet and a flue gas outlet. The first hot flue gas passage and the second hot flue gas passage are connected through a hot flue gas connecting channel. The first air passage and the second air passage are respectively connected to the air inlet of the indirect heat exchanger. The air outlet of the indirect heat exchanger is connected to an air exhaust pipeline. The first cold flue gas passage and the second cold flue gas passage are respectively connected to the flue gas inlet of the indirect heat exchanger through independent pipelines and are respectively connected to the second circulating flue gas inlet and the first circulating flue gas inlet through independent pipelines. The flue gas outlet of the indirect heat exchanger is connected to the hot flue gas connecting channel.

[0009] As a preferred, the first hot flue gas passage is arranged at the bottom end of the side wall of the first vertical furnace combustion chamber, and the first air passage is arranged at the top end of the side wall of the first vertical furnace cooling chamber. The second hot flue gas passage is arranged at the bottom end of the side wall of the second vertical furnace combustion chamber, and the second air passage is arranged at the top end of the side wall of the second vertical furnace cooling chamber. The airflow shunt adjusting mechanism is independently arranged between the first hot flue gas passage and the first air passage and between the second hot flue gas passage and the second air passage.

[0010] As a preferred, the airflow shunt adjusting mechanism includes a lattice air-permeable plate and a vertical baffle. The lattice air-permeable plate is independently arranged on the first hot flue gas passage and the second hot flue gas passage. The vertical baffle is arranged at the lower end of the lattice air-permeable plate and extends downward into the first air passage or the second air passage. Preferably, the vertical baffle is an adjustable telescopic baffle. Preferably, in the horizontal direction, the vertical baffle has a horizontal spacing with the first air passage and the second air passage.

[0011] As a preferred, the indirect heat exchanger is a plate heat exchanger, which has an air passage and a flue gas passage that are not communicated with each other. The inlet and outlet of the air passage are the air inlet and the air outlet of the indirect heat exchanger, and the inlet and outlet of the flue gas passage are the flue gas inlet and the flue gas outlet of the indirect heat exchanger.

[0012] As a preferred, a gas component detector is arranged at the air outlet of the indirect heat exchanger or on the exhaust pipeline. The exhaust end of the exhaust pipeline is also connected to an exhaust fan.

[0013] As a preferred, a plurality of first hot flue gas passages are arranged along the circumference of the side wall of the first vertical furnace combustion chamber, and a plurality of second hot flue gas passages are arranged along the circumference of the side wall of the second vertical furnace combustion chamber. One end of the hot flue gas connecting channel surrounds the first vertical furnace combustion chamber and is connected to the plurality of first hot flue gas passages, and the other end of the hot flue gas connecting channel surrounds the second vertical furnace combustion chamber and is connected to the plurality of second hot flue gas passages.

[0014] Preferably, the lime kiln system also includes a dust collector. A first cold flue gas inlet is connected to the dust collector's inlet via a first flue gas duct. A second cold flue gas inlet is connected to the dust collector's inlet via a second flue gas duct (or the second flue gas duct is connected to the first flue gas duct via a three-way reversing valve, which allows the dust collector's inlet to selectively connect to either the first or second cold flue gas inlet). The dust collector's exhaust outlet is connected to the flue gas inlet of an indirect heat exchanger via a third flue gas duct.

[0015] Preferably, a fourth flue gas duct is connected to the first circulating flue gas inlet, and a fifth flue gas duct is connected to the second circulating flue gas inlet, both extending from the third flue gas duct. Preferably, the fifth flue gas duct is a bypass duct of the fourth flue gas duct, or the fourth flue gas duct is a bypass duct of the fifth flue gas duct. That is, the fourth flue gas duct (or the fifth duct) is connected to the fifth flue gas duct (or the fourth flue gas duct) via a three-way reversing valve, and the three-way reversing valve selectively delivers the flue gas from the third flue gas duct to either the first circulating flue gas inlet or the second circulating flue gas inlet.

[0016] Preferably, the lime kiln system also includes a compressor. The compressor's gas inlet is connected to the third flue gas duct via a sixth flue gas duct.

[0017] Preferably, the lime kiln system also includes a dewatering device. The dewatering device is installed on the third flue gas duct. Gas valves are independently installed on the first, second, third, fourth, fifth, and sixth flue gas ducts.

[0018] In existing technologies, to achieve carbon dioxide enrichment, circulating flue gas calcination is generally used to obtain high-concentration CO2 flue gas. However, directly using high-concentration CO2 flue gas as a cooling medium to cool high-temperature calcium oxide can easily lead to a reverse carbonation reaction between calcium oxide and CO2, regenerating calcium carbonate and reducing the quality and yield of lime products: CaO + CO2 → CaCO3; Figure 5 As shown in the experimental results of the weight curve of high-temperature CaO during cooling in a pure CO2 atmosphere, it can be seen that CaO and CO2 undergo a significant reverse reaction within the furnace temperature range of approximately 720–850℃. Based on this, this invention proposes an improved lime kiln system with independent circulation of carbon-rich flue gas. This lime kiln system can achieve stable operation of a new process of flue gas circulation oxygen-enriched combustion + air cooling + flue gas circulation heat exchange. Furthermore, this lime kiln system does not require modification of the traditional cooling section structure and cooling process, while simultaneously achieving high-concentration enrichment of CO2 in the tail-end flue gas and fully utilizing the waste heat of the cooling section.

[0019] In this invention, flow field calculations were performed for a typical double-chamber lime kiln, and the calculation results are as follows:Figure 6 According to the existing 600t / d typical double hearth kiln production data, the flue gas volume of the calcining section is much larger than that of the cooling section, and the volume ratio is generally about 2.2-2.3. As can be seen from the figure, the downward flowing flue gas in the calcining chamber and the upward flowing cooling gas in the cooling section meet at the annular passage (i.e. the hot flue gas connecting passage) and form a dividing surface, and the high-temperature flue gas in the calcining section is above the dividing surface, and the high-temperature cooling gas in the cooling section is below the dividing surface. In the prior art, both the two gas streams are transported to the regenerative chamber through the annular passage for utilization. Since the concentration of carbon dioxide in the high-temperature cooling gas is low, the concentration of carbon dioxide in the high-temperature flue gas will be diluted after the high-temperature cooling gas is mixed into the high-temperature flue gas, which is the reason why the CO2 concentration of the flue gas at the tail end of the existing conventional lime kiln is low. Therefore, in the utility model, the high-temperature flue gas in the calcining section and the high-temperature cooling gas in the cooling section are divided by opening the hot flue gas passage at the lower part of the side wall of the calcining chamber and the air passage at the upper part of the side wall of the cooling cavity, the high-temperature flue gas in the calcining section is directly transported to the regenerative chamber through the hot flue gas connecting passage to heat the material, and the high-temperature cooling gas from the cooling section is transported to the indirect heat exchanger to exchange heat with the cold flue gas discharged from the regenerative chamber and transfer heat to the cold flue gas, and the cold flue gas after heat exchange is finally transported to the regenerative chamber through the hot flue gas connecting passage to heat the material. That is to say, the utility model realizes the recycling of waste heat by dividing the high-temperature cooling gas in the cooling section and exchanging heat with the cold flue gas, and ensures that the concentration of carbon dioxide in the flue gas is not diluted.

[0020] In the utility model, the normal temperature air is used to cool the high-temperature lime, enters the kiln body from the cooling gas inlet at the bottom of the cooling section, exchanges heat with the high-temperature lime, cools the high-temperature lime, and the normal temperature air is heated to above 900 DEG C, enters the plate heat exchanger from the air passage at the top of the cooling section, and transfers the waste heat to the cold flue gas discharged from the top of the regenerative chamber. It should be noted that when the system runs stably, the high-concentration CO2 flue gas of about 150 DEG C discharged from the top of the regenerative chamber generally needs to be treated by dust removal and water removal before being recycled, a part (generally preferably about 20% of the total regenerative flue gas volume) of the regenerative flue gas enters the plate heat exchanger to exchange heat with the high-temperature air passing through the cooling section, recovers the waste heat of the high-temperature cooling air, and then enters the hot flue gas connecting passage to mix with the calcining flue gas and enter the regenerative chamber, exchanges heat with the limestone in the regenerative chamber, and finally is discharged from the top of the regenerative chamber; a part (generally preferably about 35% of the total regenerative flue gas volume) of the regenerative flue gas is sent into the calcining chamber to replace the nitrogen in the combustion-supporting air to adjust the temperature of the flue gas of pure oxygen combustion, so as to meet the temperature requirement (generally not more than 1200 DEG C) of the limestone calcination, and the remaining part of the regenerative flue gas is sent into the compressor for compression, condensation and purification to obtain high-purity CO2.

[0021] In this invention, the first and second vertical chambers periodically alternate as the calcining chamber and the heat storage chamber. When either the first or second vertical chamber is the calcining chamber, the other is the heat storage chamber. It should be noted that when either the first or second vertical chamber is the calcining chamber, its hot flue gas inlet, air inlet, material inlet, oxygen inlet, circulating flue gas inlet, and cooling gas inlet are all open, while the cold flue gas inlet is closed. When either the first or second vertical chamber is the heat storage chamber, its air inlet, material inlet, oxygen inlet, circulating flue gas inlet, and cooling gas inlet are all closed, while the hot flue gas inlet and cold flue gas inlet are open. Adjustments can be made in real time according to actual operating conditions.

[0022] In this invention, when the lime kiln system described herein is used for production, the combustion air is circulating flue gas, in which the CO2 concentration increases significantly, but the flue gas volume in the calcination section decreases slightly. Calculations show that when the CO2 concentration in the flue gas reaches approximately 80%, the volume ratio of the flue gas volume in the calcination section to the cooling air volume in the cooling section is still higher than 1.8. Therefore, at the junction of the two airflows, the probability of the flue gas in the calcination section entering the indirect heat exchanger downwards is much greater than the probability of the cooling air entering the annular channel upwards. To address this issue, this invention improves the structure of the connection point of the existing annular channel (i.e., the hot flue gas connection channel), as follows: Figure 3 As shown, a grid-type permeable plate and a vertical baffle are added at the connection points between the first hot flue gas inlet, the second hot flue gas inlet and the hot flue gas connection channel. The purpose is to guide as much of the flue gas from the upper calcination section as possible smoothly into the hot flue gas connection channel, while preventing the cooling air from the lower cooling section from entering the hot flue gas connection channel upwards, and ensuring that as much of the cooling air from the cooling section as possible is guided into the plate heat exchanger.

[0023] In this invention, it should be noted that the grid-type permeable plate is mainly installed at the first and second hot flue gas inlets, and its grid holes are designed to slope downwards, specifically, the end of the grid hole near the hot flue gas connection channel is lower than the other end. That is to say, whether the first or second vertical chamber acts as the calcining chamber, the slope of the grid holes is downwards according to the direction of the flue gas, which facilitates the smooth entry of hot flue gas into the hot flue gas connection channel, and also prevents the cooling airflow below from entering the hot flue gas connection channel to a certain extent. A vertical baffle is suspended at the bottom of the grid-type permeable plate, extending downwards below the hot flue gas inlet to form a baffle with a certain vertical height, which helps prevent hot flue gas from flowing downwards and entering the plate heat exchanger.

[0024] In the utility model, the indirect heat exchanger is a plate heat exchanger, the plate heat exchanger has air passage and flue gas passage which are not communicated with each other, the inlet and outlet of the air passage are air inlet and air outlet of the indirect heat exchanger, and the inlet and outlet of the flue gas passage are flue gas inlet and flue gas outlet of the indirect heat exchanger, the air passage is used for passing high-temperature cooling air flow from the cooling section, the flue gas passage is used for passing heat storage flue gas from the heat storage chamber, and the double-passage design of the air passage and the flue gas passage enables only heat exchange between the high-temperature cooling air flow from the cooling section and the heat storage flue gas from the heat storage chamber, and has little influence on the composition of the air.

[0025] In the utility model, the gas component detector is arranged at the air outlet of the plate heat exchanger or on the exhaust pipeline, so that the CO2 concentration in the cooling air can be monitored in real time, and whether the flue gas from the calcination section flows downward into the cooling air flow and the mixing proportion can be diagnosed in real time. In order to separate the calcination flue gas and the cooling air flow to the greatest extent, two modes can be adjusted in the utility model. The first mode is to design the vertical baffle as an adjustable telescopic baffle (for example, a folding telescopic baffle or a sleeved telescopic baffle), and the height of the vertical baffle is adjusted to control. For example, the composition of the cooling air is detected at the cooling air outlet of the plate heat exchanger, when the CO2 concentration is detected to be more than 10%, the height of the vertical baffle is increased downward (the height of the vertical baffle can be manually adjusted or an independent automatic driving device is additionally arranged to automatically feedback and adjust), and the calcination flue gas can be more effectively blocked from entering the heat exchanger, which is beneficial to the smooth entry of the calcination flue gas into the hot flue gas connecting passage. If the suspended baffle is adjusted to the maximum height, and the working condition requirement cannot be met, the second mode is started, that is, the flow resistance of the cooling air in the heat exchanger is increased (for example, a resistance control valve is arranged in front of the air passage of the heat exchanger, the system resistance is adjusted, and the inlet pressure is adjusted), at this time, the cooling air flow remains unchanged, and the kiln bottom cooling air supply air pressure also needs to be increased, through the above operation, the air pressure at the inlet of the plate heat exchanger is increased, and the calcination flue gas from the upper part can also be prevented from entering the plate heat exchanger.

[0026] In the utility model, it is necessary to explain that, when the plate heat exchanger is used for heat exchange treatment, a preferred operation scheme is that the plate heat exchanger transfers the heat of the hot air from the cooling section to the heat storage flue gas from the heat storage section, and the outlet temperature of the hot air of the plate heat exchanger is generally lower than 200 DEG C, and the outlet temperature of the heat storage flue gas is generally higher than 600 DEG C.

[0027] In the utility model, the height of the first vertical furnace and the second vertical furnace is 3-100m respectively, preferably 5-80m, more preferably 10-50m, and further preferably 20-30m. The inner diameter of the first vertical furnace and the second vertical furnace is 1-30m, preferably 2-20m, more preferably 3-15m, and further preferably 4-8m. The inner diameter of the hot flue gas connecting channel is 0.3-2m, preferably 0.5-1m, and more preferably 0.6-0.8m.

[0028] Compared with the prior art, the utility model has the beneficial technical effects as follows:

[0029] 1: the utility model discloses a separation disposal is carried out to the calcination section flue gas and cooling airflow, and the heat exchange is carried out to the heat storage flue gas and high temperature cooling airflow after being recycled, can be on the basis of not changing the existing furnace cooling section structure and avoiding the reverse reaction of high temperature lime, both guarantee the cooling effect and realize the circulation enrichment of carbon dioxide in the calcination flue gas, and then be favorable to realize the low -cost carbon dioxide capture operation.

[0030] 2: the utility model discloses still setting up gas composition detector real -time monitoring CO2 concentration in cooling wind in indirect heat exchanger air outlet place cooperates with the airflow shunt adjusting mechanism of flue gas outlet of the side wall bottom of combustion chamber, realizes the separation monitoring and flexible regulation and control of calcination flue gas and high temperature cooling airflow, and it is favorable to ensure that calcination flue gas and high temperature cooling airflow can possibly smoothly shunt, realizes the stable operation of system.

[0031] 3: the utility model discloses lime kiln system whole structure is simple, and the adjustment and convenient operation, and the system can realize continuous production, and the system cooling structure is fully retained and can realize the full even cooling of material. In addition, it also has the advantages of high overall production efficiency and low maintenance cost. ACCURACY

[0032] Figure 1 It is the existing parallel flow heat accumulating type double-furnace lime vertical kiln.

[0033] Figure 2 It is the structure diagram of the lime kiln system of the utility model.

[0034] Figure 3 It is the partial enlarged view of the hot flue gas pass and the air pass of the lime kiln system of the utility model.

[0035] Figure 4 It is the whole structure schematic view of the lime kiln system of the utility model.

[0036] Figure 5 It is the cooling and weight gain curve diagram of high temperature CaO cooling process.

[0037] Figure 6The application discloses a flow field distribution map in a parallel heat accumulating double-chamber lime shaft kiln.

[0038] The figure mark: 1: first vertical chamber; 101: first hot flue gas passage; 102: first air passage; 103: first cold flue gas passage; 104: first material inlet; 105: first oxygen inlet; 106: first circulating flue gas inlet; 107: first cooling gas inlet; 2: second vertical chamber; 201: second hot flue gas passage; 202: second air passage; 203: second cold flue gas passage; 204: second material inlet; 205: second oxygen inlet; 206: second circulating flue gas inlet; 207: second cooling gas inlet; 3: indirect heat exchanger; 301: air exhaust pipeline; 302: gas component detector; 303: air draught fan; 4: hot flue gas connecting passage; 5: air flow shunt adjusting mechanism; 501: fence type air permeable plate; 502: vertical baffle; 6: dust remover; 7: compressor; L1: first flue gas pipeline; L2: second flue gas pipeline; L3: third flue gas pipeline; L4: fourth flue gas pipeline; L5: fifth flue gas pipeline; L6: sixth flue gas pipeline. DETAILED DESCRIPTION

[0039] The technical scheme of the application is illustrated below, and the scope of protection of the application includes but is not limited to the following embodiments.

[0040] A lime kiln system with independent circulation of carbon-rich flue gas, comprising a first vertical chamber 1, a second vertical chamber 2 and an indirect heat exchanger 3. The first vertical chamber 1 and the second vertical chamber 2 are identical in structure and each comprises a combustion chamber and a cooling chamber connected in series from top to bottom. A first hot flue gas passage 101 is formed in the lower part of the side wall of the combustion chamber of the first vertical chamber 1, a first air passage 102 is formed in the upper part of the side wall of the cooling chamber of the first vertical chamber 1, and a first cold flue gas passage 103, a first material inlet 104, a first oxygen inlet 105 and a first circulating flue gas inlet 106 are further formed in the top of the combustion chamber of the first vertical chamber 1, and a first cooling gas inlet 107 is further formed in the bottom of the cooling chamber of the first vertical chamber 1. A second hot flue gas passage 201 is formed in the lower part of the side wall of the combustion chamber of the second vertical chamber 2, a second air passage 202 is formed in the upper part of the side wall of the cooling chamber of the second vertical chamber 2, and a second cold flue gas passage 203, a second material inlet 204, a second oxygen inlet 205 and a second circulating flue gas inlet 206 are further formed in the top of the combustion chamber of the second vertical chamber 2, and a second cooling gas inlet 207 is further formed in the bottom of the cooling chamber of the second vertical chamber 2.

[0041] The indirect heat exchanger 3 is arranged between the first vertical furnace 1 and the second vertical furnace 2, and the air inlet, the air outlet, the flue gas inlet and the flue gas outlet are arranged on the indirect heat exchanger 3. The first hot flue gas passage 101 and the second hot flue gas passage 201 are connected through the hot flue gas connecting passage 4. The first air passage 102 and the second air passage 202 are respectively connected with the air inlet of the indirect heat exchanger 3. The air outlet of the indirect heat exchanger 3 is connected with the air exhaust pipeline 301. The first cold flue gas passage 103 and the second cold flue gas passage 203 are respectively connected with the flue gas inlet of the indirect heat exchanger 3 through independent pipelines, and are respectively connected with the second circulating flue gas inlet 206 and the first circulating flue gas inlet 106 through independent pipelines. The flue gas outlet of the indirect heat exchanger 3 is connected with the hot flue gas connecting passage 4.

[0042] As preferred, the first hot flue gas passage 101 is arranged at the bottom end of the side wall of the combustion chamber of the first vertical furnace 1, and the first air passage 102 is arranged at the top end of the side wall of the cooling chamber of the first vertical furnace 1. The second hot flue gas passage 201 is arranged at the bottom end of the side wall of the combustion chamber of the second vertical furnace 2, and the second air passage 202 is arranged at the top end of the side wall of the cooling chamber of the second vertical furnace 2. The airflow shunt adjusting mechanism 5 is independently arranged between the first hot flue gas passage 101 and the first air passage 102, and between the second hot flue gas passage 201 and the second air passage 202.

[0043] As preferred, the airflow shunt adjusting mechanism 5 includes a lattice type air permeable plate 501 and a vertical baffle 502. The lattice type air permeable plate 501 is independently arranged on the first hot flue gas passage 101 and the second hot flue gas passage 201. The vertical baffle 502 is arranged at the lower end of the lattice type air permeable plate 501 and extends downward into the first air passage 102 or the second air passage 202. Preferably, the vertical baffle 502 is an adjustable telescopic baffle. Preferably, in the horizontal direction, the vertical baffle 502 has a horizontal spacing with the first air passage 102 and the second air passage 202.

[0044] As preferred, the indirect heat exchanger 3 is a plate heat exchanger, which has an air passage and a flue gas passage that are not communicated with each other inside. The inlet and outlet of the air passage are the air inlet and the air outlet of the indirect heat exchanger 3, and the inlet and outlet of the flue gas passage are the flue gas inlet and the flue gas outlet of the indirect heat exchanger 3.

[0045] As preferred, a gas component detector 302 is arranged at the air outlet of the indirect heat exchanger 3 or on the exhaust pipeline 301. The exhaust end of the exhaust pipeline 301 is also connected with an exhaust fan 303.

[0046] As preferred, a plurality of first hot flue gas passages 101 are formed along the circumference of the side wall of the first vertical furnace 1 combustion chamber, and a plurality of second hot flue gas passages 201 are formed along the circumference of the side wall of the second vertical furnace 2 combustion chamber. One end of the hot flue gas connecting passage 4 surrounds the first vertical furnace 1 combustion chamber and communicates with the plurality of first hot flue gas passages 101, and the other end of the hot flue gas connecting passage 4 surrounds the second vertical furnace 2 combustion chamber and communicates with the plurality of second hot flue gas passages 201.

[0047] As preferred, the lime kiln system further comprises a dust collector 6. The first cold flue gas passage 103 is connected to the gas inlet of the dust collector 6 through a first flue gas pipe L1. The second cold flue gas passage 203 is connected to the gas inlet of the dust collector 6 through a second flue gas pipe L2. The gas outlet of the dust collector 6 is connected to the flue gas inlet of the indirect heat exchanger 3 through a third flue gas pipe L3.

[0048] As preferred, the third flue gas pipe L3 further leads out a fourth flue gas pipe L4 connected to the first circulating flue gas inlet 106 and a fifth flue gas pipe L5 connected to the second circulating flue gas inlet 206.

[0049] As preferred, the lime kiln system further comprises a compressor 7. The gas inlet of the compressor 7 is connected to the third flue gas pipe L3 through a sixth flue gas pipe L6.

[0050] As preferred, the lime kiln system further comprises a water separator 8. The water separator 8 is arranged on the third flue gas pipe L3. Gas valves are independently arranged on the first flue gas pipe L1, the second flue gas pipe L2, the third flue gas pipe L3, the fourth flue gas pipe L4, the fifth flue gas pipe L5 and the sixth flue gas pipe L6.

[0051] Embodiment 1

[0052] As preferred, the lime kiln system further comprises a dust collector 6. The first cold flue gas passage 103 is connected to the gas inlet of the dust collector 6 through a first flue gas pipe L1. The second cold flue gas passage 203 is connected to the gas inlet of the dust collector 6 through a second flue gas pipe L2. The gas outlet of the dust collector 6 is connected to the flue gas inlet of the indirect heat exchanger 3 through a third flue gas pipe L3. Figures 2-4As shown, a lime kiln system with carbon-rich flue gas independent circulation comprises a first shaft 1, a second shaft 2 and an indirect heat exchanger 3. The first shaft 1 and the second shaft 2 are identical in structure and each comprises a combustion chamber and a cooling chamber connected in series from top to bottom. A first hot flue gas passage 101 is formed at the lower part of the side wall of the combustion chamber of the first shaft 1, a first air passage 102 is formed at the upper part of the side wall of the cooling chamber of the first shaft 1, and a first cold flue gas passage 103, a first material inlet 104, a first oxygen inlet 105 and a first circulating flue gas inlet 106 are formed at the top of the combustion chamber of the first shaft 1, and a first cooling gas inlet 107 is formed at the bottom of the cooling chamber of the first shaft 1. A second hot flue gas passage 201 is formed at the lower part of the side wall of the combustion chamber of the second shaft 2, a second air passage 202 is formed at the upper part of the side wall of the cooling chamber of the second shaft 2, and a second cold flue gas passage 203, a second material inlet 204, a second oxygen inlet 205 and a second circulating flue gas inlet 206 are formed at the top of the combustion chamber of the second shaft 2, and a second cooling gas inlet 207 is formed at the bottom of the cooling chamber of the second shaft 2.

[0053] The indirect heat exchanger 3 is arranged between the first shaft 1 and the second shaft 2, and an air inlet, an air outlet, a flue gas inlet and a flue gas outlet are formed on the indirect heat exchanger 3. The first hot flue gas passage 101 and the second hot flue gas passage 201 are connected by a hot flue gas connecting channel 4. The first air passage 102 and the second air passage 202 are respectively connected to the air inlet of the indirect heat exchanger 3 independently. The air outlet of the indirect heat exchanger 3 is connected to an air exhaust pipe 301. The first cold flue gas passage 103 and the second cold flue gas passage 203 are respectively connected to the flue gas inlet of the indirect heat exchanger 3 by independent pipelines and are respectively connected to the second circulating flue gas inlet 206 and the first circulating flue gas inlet 106 by independent pipelines. The flue gas outlet of the indirect heat exchanger 3 is connected to the hot flue gas connecting channel 4.

[0054] Example 2

[0055] Example 1 is repeated, except that the first hot flue gas passage 101 is formed at the bottom end of the side wall of the combustion chamber of the first shaft 1, and the first air passage 102 is formed at the top end of the side wall of the cooling chamber of the first shaft 1. The second hot flue gas passage 201 is formed at the bottom end of the side wall of the combustion chamber of the second shaft 2, and the second air passage 202 is formed at the top end of the side wall of the cooling chamber of the second shaft 2. A flow shunt adjusting mechanism 5 is independently arranged between the first hot flue gas passage 101 and the first air passage 102 and between the second hot flue gas passage 201 and the second air passage 202.

[0056] Example 3

[0057] Example 4 is repeated, except that the air flow shunt adjusting mechanism 5 comprises a latticed air-permeable plate 501 and a vertical baffle 502. The latticed air-permeable plate 501 is arranged independently on the first hot flue gas passage 101 and the second hot flue gas passage 201. The vertical baffle 502 is arranged at the lower end of the latticed air-permeable plate 501 and extends downward into the first air passage 102 or the second air passage 202. Preferably, the vertical baffle 502 is an adjustable telescopic baffle.

[0058] Example 4

[0059] Example 3 is repeated, except that in the horizontal direction, there is a horizontal spacing between the vertical baffle 502 and the first air passage 102 and between the vertical baffle 502 and the second air passage 202.

[0060] Example 5

[0061] Example 4 is repeated, except that the indirect heat exchanger 3 is a plate heat exchanger, which has air passages and flue gas passages that are not in communication with each other inside the plate heat exchanger. The inlet and outlet of the air passages are the air inlet and air outlet of the indirect heat exchanger 3, and the inlet and outlet of the flue gas passages are the flue gas inlet and flue gas outlet of the indirect heat exchanger 3.

[0062] Example 6

[0063] Example 5 is repeated, except that a gas composition detector 302 is further arranged at the air outlet of the indirect heat exchanger 3 or on the exhaust duct 301. The exhaust end of the exhaust duct 301 is further connected with an exhaust fan 303.

[0064] Example 7

[0065] Example 6 is repeated, except that a plurality of first hot flue gas passages 101 are arranged along the circumference of the side wall of the combustion chamber of the first shaft 1, and a plurality of second hot flue gas passages 201 are arranged along the circumference of the side wall of the combustion chamber of the second shaft 2. One end of the hot flue gas connecting passage 4 surrounds the combustion chamber of the first shaft 1 and is in communication with each of the plurality of first hot flue gas passages 101, and the other end of the hot flue gas connecting passage 4 surrounds the combustion chamber of the second shaft 2 and is in communication with each of the plurality of second hot flue gas passages 201.

[0066] Example 8

[0067] Example 7 is repeated, except that the lime kiln system further comprises a dust collector 6. The first cold flue gas passage 103 is connected with the gas inlet of the dust collector 6 through a first flue gas duct L1. The second cold flue gas passage 203 is connected with the gas inlet of the dust collector 6 through a second flue gas duct L2. The gas outlet of the dust collector 6 is connected with the flue gas inlet of the indirect heat exchanger 3 through a third flue gas duct L3.

[0068] Example 9

[0069] Example 8 is repeated, except that a fourth flue L4 and a fifth flue L5 are further connected to the first circulating flue inlet 106 and the second circulating flue inlet 206, respectively.

[0070] Example 10

[0071] Example 9 is repeated, except that the lime kiln system further comprises a compressor 7. The gas inlet of the compressor 7 is connected to the third flue L3 through a sixth flue L6.

[0072] Example 11

[0073] Example 10 is repeated, except that the lime kiln system further comprises a water remover 8. The water remover 8 is arranged on the third flue L3. Gas valves are arranged on the first flue L1, the second flue L2, the third flue L3, the fourth flue L4, the fifth flue L5 and the sixth flue L6, respectively, for adjusting the gas flow of each flue.

[0074] Application Example 1

[0075] The lime kiln system with the carbon-rich flue gas circulating independently as described in Example 11 is used for lime production and carbon dioxide enrichment and recovery:

[0076] The first shaft 1 is used as a combustion shaft, and the second shaft 2 is used as a regenerative shaft. The first hot flue port 101, the first air port 102, the first material inlet 104, the first oxygen inlet 105, the first circulating flue inlet 106 and the first cooling gas inlet 107 of the first shaft 1 are opened, and the first cold flue port 103 is closed. The second hot flue port 201 and the second cold flue port 203 of the second shaft 2 are opened, and the second air port 202, the second material inlet 204, the second oxygen inlet 205, the second circulating flue inlet 206 and the second cooling gas inlet 207 are closed.

[0077] The lime raw material and coal powder are both fed into the combustion chamber from the first material inlet 104, and pure oxygen and part (specifically, about 35% of the total amount of regenerative flue gas) of the regenerative flue gas discharged from the regenerative chamber are introduced into the combustion chamber through the first oxygen inlet 105 and the first circulating flue gas inlet 106 as combustion-supporting gas to calcine the fed lime raw material, and the calcination temperature is 1100°C. The calcined material descends into the cooling chamber, and is in countercurrent contact with the normal-temperature air introduced from the first cooling gas inlet 107 to be cooled by heat exchange, and is discharged from the material outlet at the bottom of the cooling chamber; during the calcination and cooling processes, the calcination flue gas generated in the combustion chamber enters the regenerative chamber through the first hot flue gas passage 101, the hot flue gas connecting passage 4 and the second hot flue gas passage 201 to preheat the material in the regenerative chamber; the high-temperature cooling gas generated in the cooling chamber enters the plate heat exchanger through the first air passage 102, and is in countercurrent heat exchange with part (specifically, about 20% of the total amount of regenerative flue gas) of the regenerative flue gas discharged from the second cooling gas passage 203 at the top of the regenerative chamber after being subjected to dust removal and water removal, and after the heat exchange, the regenerative flue gas is raised to about 760°C and enters the hot flue gas connecting passage 4 to combine with the calcination flue gas and then enters the regenerative chamber, and the high-temperature cooling gas after the heat exchange is cooled to about 155°C (which can be further utilized for waste heat and then discharged). After the system is stably operated, the concentration of carbon dioxide in the regenerative flue gas is detected to be stably above 80%, at this time, part (specifically, about 45% of the total amount of regenerative flue gas) of the regenerative flue gas can be compressed, condensed and purified to obtain high-purity CO2.

Claims

1. A lime kiln system with independent circulation of carbon-rich flue gas, characterized by: The lime kiln system comprises a first shaft (1), a second shaft (2) and an indirect heat exchanger (3); the first shaft (1) and the second shaft (2) are identical in structure and each comprises a combustion chamber and a cooling chamber connected in series from top to bottom; a first hot flue gas passage (101) is formed at the lower part of the side wall of the combustion chamber of the first shaft (1), a first air passage (102) is formed at the upper part of the side wall of the cooling chamber of the first shaft (1), a first cold flue gas passage (103), a first material inlet (104), a first oxygen inlet (105) and a first circulating flue gas inlet (106) are further formed at the top of the combustion chamber of the first shaft (1), and a first cooling gas inlet (107) is further formed at the bottom of the cooling chamber of the first shaft (1); a second hot flue gas passage (201) is formed at the lower part of the side wall of the combustion chamber of the second shaft (2), a second air passage (202) is formed at the upper part of the side wall of the cooling chamber of the second shaft (2), a second cold flue gas passage (203), a second material inlet (204), a second oxygen inlet (205) and a second circulating flue gas inlet (206) are further formed at the top of the combustion chamber of the second shaft (2), and a second cooling gas inlet (207) is further formed at the bottom of the cooling chamber of the second shaft (2); The indirect heat exchanger (3) is arranged between the first shaft (1) and the second shaft (2) and is provided with an air inlet, an air outlet, a flue gas inlet and a flue gas outlet; the first hot flue gas passage (101) and the second hot flue gas passage (201) are connected through a hot flue gas connecting channel (4); the first air passage (102) and the second air passage (202) are respectively connected to the air inlet of the indirect heat exchanger (3) independently; the air outlet of the indirect heat exchanger (3) is connected to an air exhaust pipeline (301); the first cold flue gas passage (103) and the second cold flue gas passage (203) are respectively connected to the flue gas inlet of the indirect heat exchanger (3) through independent pipelines and are respectively connected to the second circulating flue gas inlet (206) and the first circulating flue gas inlet (106) through independent pipelines; the flue gas outlet of the indirect heat exchanger (3) is connected to the hot flue gas connecting channel (4).

2. The lime kiln system of claim 1, wherein: The first hot flue gas passage (101) is formed at the bottom end of the side wall of the combustion chamber of the first shaft (1), the first air passage (102) is formed at the top end of the side wall of the cooling chamber of the first shaft (1); the second hot flue gas passage (201) is formed at the bottom end of the side wall of the combustion chamber of the second shaft (2), the second air passage (202) is formed at the top end of the side wall of the cooling chamber of the second shaft (2); a gas flow shunt adjusting mechanism (5) is independently arranged between the first hot flue gas passage (101) and the first air passage (102) and between the second hot flue gas passage (201) and the second air passage (202).

3. The lime kiln system of claim 2, wherein: The air flow shunt adjusting mechanism (5) comprises a fence type air permeable plate (501) and a vertical baffle (502); the fence type air permeable plate (501) is independently arranged on the first hot flue gas passage (101) and the second hot flue gas passage (201); the vertical baffle (502) is arranged at the lower end of the fence type air permeable plate (501) and extends downward into the first air passage (102) or the second air passage (202).

4. The lime kiln system of claim 3, wherein: The vertical baffle (502) is an adjustable telescopic baffle.

5. The lime kiln system of claim 3, wherein: In the horizontal direction, the vertical baffle (502) has a horizontal spacing with the first air passage (102) and the second air passage (202).

6. The lime kiln system according to any one of claims 1-5, characterized in that: The indirect heat exchanger (3) is a plate type heat exchanger, which has an air passage and a flue gas passage that are not communicated with each other; the inlet and outlet of the air passage are the air inlet and air outlet of the indirect heat exchanger (3), and the inlet and outlet of the flue gas passage are the flue gas inlet and flue gas outlet of the indirect heat exchanger (3).

7. The lime kiln system according to any one of claims 1-5, characterized in that: A gas composition detector (302) is arranged at the air outlet of the indirect heat exchanger (3) or on the exhaust pipe (301); and an exhaust fan (303) is further connected to the exhaust end of the exhaust pipe (301).

8. The lime kiln system of claim 6, wherein: A gas composition detector (302) is arranged at the air outlet of the indirect heat exchanger (3) or on the exhaust pipe (301); and an exhaust fan (303) is further connected to the exhaust end of the exhaust pipe (301).

9. The lime kiln system according to any one of claims 1-5, 8, characterized in that: A plurality of first hot flue gas passages (101) are arranged along the circumference of the side wall of the combustion chamber of the first vertical furnace (1), and a plurality of second hot flue gas passages (201) are arranged along the circumference of the side wall of the combustion chamber of the second vertical furnace (2); one end of the hot flue gas connecting passage (4) surrounds the combustion chamber of the first vertical furnace (1) and is communicated with the plurality of first hot flue gas passages (101), and the other end of the hot flue gas connecting passage (4) surrounds the combustion chamber of the second vertical furnace (2) and is communicated with the plurality of second hot flue gas passages (201).

10. The lime kiln system according to any one of claims 1-5, 8, characterized in that: The lime kiln system further comprises a dust collector (6); the first cold flue gas passage (103) is connected to the air inlet of the dust collector (6) through a first flue gas pipe (L1); the second cold flue gas passage (203) is connected to the air inlet of the dust collector (6) through a second flue gas pipe (L2); and the exhaust port of the dust collector (6) is connected to the flue gas inlet of the indirect heat exchanger (3) through a third flue gas pipe (L3).

11. The lime kiln system of claim 6, wherein: The lime kiln system further comprises a dust collector (6); the first cold flue gas passage (103) is connected to the air inlet of the dust collector (6) through a first flue gas pipe (L1); the second cold flue gas passage (203) is connected to the air inlet of the dust collector (6) through a second flue gas pipe (L2); and the exhaust port of the dust collector (6) is connected to the flue gas inlet of the indirect heat exchanger (3) through a third flue gas pipe (L3).

12. The lime kiln system of claim 7, wherein: The lime kiln system further comprises a dust remover (6); the first cold flue gas passage (103) is connected with the gas inlet of the dust remover (6) through the first flue gas pipeline (L1); the second cold flue gas passage (203) is connected with the gas inlet of the dust remover (6) through the second flue gas pipeline (L2); the gas outlet of the dust remover (6) is connected with the flue gas inlet of the indirect heat exchanger (3) through the third flue gas pipeline (L3).

13. The lime kiln system of claim 9, wherein: The lime kiln system further comprises a dust remover (6); the first cold flue gas passage (103) is connected with the gas inlet of the dust remover (6) through the first flue gas pipeline (L1); the second cold flue gas passage (203) is connected with the gas inlet of the dust remover (6) through the second flue gas pipeline (L2); the gas outlet of the dust remover (6) is connected with the flue gas inlet of the indirect heat exchanger (3) through the third flue gas pipeline (L3).

14. The lime kiln system of claim 10, wherein: The fourth flue gas pipeline (L4) connected with the first circulating flue gas inlet (106) and the fifth flue gas pipeline (L5) connected with the second circulating flue gas inlet (206) are further led out on the third flue gas pipeline (L3).

15. The lime kiln system according to any one of claims 11-13, characterized in that: The fourth flue gas pipeline (L4) connected with the first circulating flue gas inlet (106) and the fifth flue gas pipeline (L5) connected with the second circulating flue gas inlet (206) are further led out on the third flue gas pipeline (L3).

16. The lime kiln system of claim 10, wherein: The lime kiln system further comprises a compressor (7); the gas inlet of the compressor (7) is communicated with the third flue gas pipeline (L3) through the sixth flue gas pipeline (L6).

17. The lime kiln system according to any one of claims 11-14, characterized in that: The lime kiln system further comprises a compressor (7); the gas inlet of the compressor (7) is communicated with the third flue gas pipeline (L3) through the sixth flue gas pipeline (L6).

18. The lime kiln system of claim 10, wherein: The lime kiln system further comprises a water remover (8); the water remover (8) is arranged on the third flue gas pipeline (L3); the gas valves are independently arranged on the first flue gas pipeline (L1), the second flue gas pipeline (L2), the third flue gas pipeline (L3), the fourth flue gas pipeline (L4), the fifth flue gas pipeline (L5) and the sixth flue gas pipeline (L6).

19. The lime kiln system according to any one of claims 11-14, 16, characterized in that: The lime kiln system further comprises a water remover (8); the water remover (8) is arranged on the third flue gas pipeline (L3); the gas valves are independently arranged on the first flue gas pipeline (L1), the second flue gas pipeline (L2), the third flue gas pipeline (L3), the fourth flue gas pipeline (L4), the fifth flue gas pipeline (L5) and the sixth flue gas pipeline (L6).

20. The lime kiln system of claim 15, wherein: The lime kiln system further comprises a water remover (8); the water remover (8) is arranged on the third flue gas pipeline (L3); the gas valves are independently arranged on the first flue gas pipeline (L1), the second flue gas pipeline (L2), the third flue gas pipeline (L3), the fourth flue gas pipeline (L4), the fifth flue gas pipeline (L5) and the sixth flue gas pipeline (L6).

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