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

Abstract

The invention 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 invention relates to a lime kiln carbon enrichment system, in particular to a lime kiln system with independent circulation of carbon-rich flue gas, belonging to the technical field of lime kiln carbon enrichment and capture. Background Art

[0002] Active lime is an important industrial raw material, which is widely used in the steel industry, calcium carbide industry and alumina industry, and has huge demand. In the past decade, my country's lime production has continued to grow, and it is the focus of CO2 emission reduction and carbon capture in the industrial field.

[0003] Parallel flow regenerative double-chamber lime shaft kiln (see Figure 1 ) is currently the most advanced type of industrial lime production equipment and mainstream kiln type. It adopts double-chamber reversing heat storage technology. Compared with other kiln types such as rotary kilns and mechanized vertical kilns, it has the advantages of high system energy efficiency, uniform product roasting and low pollution emissions. However, the tail flue gas CO2 concentration produced by the current conventional lime production process is relatively low, generally below 20%. Since the cost of carbon capture increases with the decrease in the concentration of carbon dioxide in the capture source, its carbon capture cost is as high as 300 yuan / ton of carbon dioxide or more, causing most manufacturers to directly discharge tail gas into the atmosphere, causing great waste of resources and environmental pollution. Therefore, the low tail CO2 concentration greatly limits the large-scale application of carbon capture technology in lime kiln equipment.

[0004] In response to the above problems, technical personnel in the industry have proposed a carbon front-end enrichment technology, which is to obtain high-concentration CO2 flue gas by reducing or eliminating other gas components in the flue gas, thereby greatly reducing the cost of tail-end carbon capture and achieving near-zero emissions in lime production. The main technical feature of this method is that it uses circulating flue gas instead of cooling air to cool the high-temperature lime, and uses pure oxygen + circulating flue gas for calcination to obtain high-concentration CO2 flue gas. However, directly using high-concentration CO2 flue gas to cool high-temperature calcium oxide can easily lead to a reverse carbonization reaction between calcium oxide and CO2, regenerating calcium carbonate, and reducing the quality and output of lime products. However, the indirect cooling method also has 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, form a bridging effect, hinder the downward movement of materials, and disrupt the continuity of production; Second, indirect cooling can easily cause local uneven heating, that is, the material close to the cooling pipe is cooled faster, and the material farther away from the cooling pipe is cooled slower, resulting in excessively high local temperature of the outlet material, or more cooling resources are consumed in order to make all outlet material temperatures meet the requirements; Third, the cooling pipe is subjected to mechanical friction and thermal stress of high-temperature materials in the furnace, and is prone to cracking, bending, deformation and other wear and tear, and needs to be replaced frequently, resulting in forced interruption of production, reduced production efficiency and high maintenance costs. Summary of the invention

[0005] In view of the problems that the existing carbon front-end enrichment technology adopts a direct cooling method and has reverse reactions that affect product quality, and the method using a built-in cooling pipeline has poor production continuity, uneven cooling and poor operating stability, the present invention provides a lime kiln system with independent circulation of carbon-rich flue gas. The system arranges an indirect heat exchange mechanism between heat storage cold flue gas and cooling air between the vertical chambers of a double-chamber lime kiln, and separates the cooling air from the cooling section and the calcining flue gas from the calcining section from the annular channel (i.e., the hot flue gas connecting channel connecting the calcining chamber and the heat storage chamber). On the one hand, it can avoid the cooling airflow from merging into the calcining flue gas to dilute the carbon dioxide concentration in the flue gas. On the other hand, the heat storage cold flue gas absorbs the waste heat of the high-temperature cooling air and returns it to the combustion chamber for recycling. It can achieve the cyclic enrichment of carbon dioxide and the recycling of cooling waste heat without affecting product quality. It has the advantages of good production continuity, ensuring stable system operation and low equipment maintenance cost.

[0006] In order to achieve the above technical objectives, the technical solutions adopted by the present invention are specifically described as follows: A lime kiln system with independent circulation of carbon-rich flue gas, the lime kiln system comprising a first vertical chamber, a second vertical chamber and an indirect heat exchanger. The first vertical chamber and the second vertical chamber have the same structure, both comprising a combustion chamber and a cooling chamber connected in series from top to bottom. A first hot flue gas port is provided at the lower part of the side wall of the combustion chamber of the first vertical chamber, a first air port is provided at the upper part of the side wall of the cooling chamber of the first vertical chamber, a first cold flue gas port, a first material inlet, a first oxygen inlet and a first circulating flue gas inlet are also provided at the top of the combustion chamber of the first vertical chamber, and a first cooling air inlet is also provided at the bottom of the cooling chamber of the first vertical chamber. A second hot flue gas port is provided at the lower part of the side wall of the combustion chamber of the second vertical chamber, a second air port is provided at the upper part of the side wall of the cooling chamber of the second vertical chamber, a second cold flue gas port, a second material inlet, a second oxygen inlet and a second circulating flue gas inlet are also provided at the top of the combustion chamber of the second vertical chamber, and a second cooling air inlet is also provided at the bottom of the cooling chamber of the second vertical chamber.

[0007] The indirect heat exchanger is arranged between the first vertical chamber and the second vertical chamber, and an air inlet, an air outlet, a smoke inlet and a smoke outlet are provided on the indirect heat exchanger. The first hot smoke outlet is connected to the second hot smoke outlet through a hot smoke connecting channel. The first air outlet and the second air outlet are independently connected to the air inlet of the indirect heat exchanger. The air outlet of the indirect heat exchanger is connected to an air exhaust duct. The first cold smoke outlet and the second cold smoke outlet are each connected to the smoke inlet of the indirect heat exchanger through an independent pipeline, and each is connected to the second circulating smoke inlet and the first circulating smoke inlet through an independent pipeline. The smoke outlet of the indirect heat exchanger is connected to the hot smoke connecting channel.

[0008] Preferably, the first hot flue gas vent is opened at the bottom end of the side wall of the first vertical chamber combustion chamber, and the first air vent is opened at the top end of the side wall of the first vertical chamber cooling chamber. The second hot flue gas vent is opened at the bottom end of the side wall of the second vertical chamber combustion chamber, and the second air vent is opened at the top end of the side wall of the second vertical chamber cooling chamber. An airflow splitting regulating mechanism is independently provided between the first hot flue gas vent and the first air vent, and between the second hot flue gas vent and the second air vent.

[0009] Preferably, the air flow diversion and adjustment mechanism includes a fence-type air permeable plate and a vertical baffle. The first hot smoke outlet and the second hot smoke outlet are each independently provided with a fence-type air permeable plate. The vertical baffle is provided at the lower end of the fence-type air permeable plate and extends downward into the first air outlet or the second air outlet. Preferably, the vertical baffle is an adjustable telescopic baffle. Preferably, in the horizontal direction, there is a horizontal spacing between the vertical baffle and the first air outlet and between the vertical baffle and the second air outlet.

[0010] Preferably, the indirect heat exchanger is a plate heat exchanger having an air channel and a smoke channel which are not connected to each other. The inlet and outlet of the air channel are the air inlet and air outlet of the indirect heat exchanger, and the inlet and outlet of the smoke channel are the smoke inlet and smoke outlet of the indirect heat exchanger.

[0011] Preferably, a gas composition detector is provided at the air outlet of the indirect heat exchanger or on the exhaust pipe. An exhaust fan is connected to the exhaust end of the exhaust pipe.

[0012] Preferably, a plurality of first hot flue gas openings are provided along the circumferential direction of the side wall of the first vertical combustion chamber, and a plurality of second hot flue gas openings are provided along the circumferential direction of the side wall of the second vertical combustion chamber. One end of the hot flue gas connection channel surrounds the first vertical combustion chamber and is in communication with the plurality of first hot flue gas openings in both directions, and the other end of the hot flue gas connection channel surrounds the second vertical combustion chamber and is in communication with the plurality of second hot flue gas openings in both directions.

[0013] Preferably, the lime kiln system further includes a dust collector. The first cold flue gas port is connected to the air inlet of the dust collector through the first flue gas duct. The second cold flue gas port is connected to the air inlet of the dust collector through the second flue gas duct (or the second flue gas duct is connected to the first flue gas duct through a three-way reversing valve, and the air inlet of the dust collector is selectively connected to the first cold flue gas port or the second cold flue gas port through the three-way reversing valve). The exhaust port of the dust collector is connected to the flue gas inlet of the indirect heat exchanger through the third flue gas duct.

[0014] Preferably, the third smoke duct further leads to a fourth smoke duct connected to the first circulating smoke inlet and a fifth smoke duct connected to the second circulating smoke inlet. Preferably, the fifth smoke duct is a bypass duct of the fourth smoke duct or the fourth smoke duct is a bypass duct of the fifth smoke duct. That is, the fourth smoke duct (or the fifth duct) is connected to the fifth smoke duct (or the fourth smoke duct) through a three-way reversing valve, and the smoke from the third smoke duct is selectively transported to the first circulating smoke inlet or the second circulating smoke inlet through the three-way reversing valve.

[0015] Preferably, the lime kiln system further comprises a compressor, and a gas inlet of the compressor is connected to the third flue gas duct through a sixth flue gas duct.

[0016] Preferably, the lime kiln system further comprises a dehydrator. The dehydrator is arranged on the third flue gas duct. Gas valves are independently arranged on the first flue gas duct, the second flue gas duct, the third flue gas duct, the fourth flue gas duct, the fifth flue gas duct and the sixth flue gas duct.

[0017] In the prior art, in order to achieve the enrichment of carbon dioxide, 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 carbonization reaction between calcium oxide and CO2, regenerating calcium carbonate, and reducing the quality and output of lime products: CaO+CO2→CaCO3; Figure 5 As shown, according to 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 will undergo an obvious reverse reaction in the range of about 720-850°C in the furnace. Based on this, the present invention proposes an improved lime kiln system with independent circulation of carbon-rich flue gas, which can achieve stable operation of the new process of flue gas circulation oxygen-enriched combustion + air cooling + flue gas circulation heat exchange, and the lime kiln system does not need to change the traditional cooling section structure and cooling process, while achieving high-concentration enrichment of tail flue gas CO2 and making full use of the waste heat of the cooling section.

[0018] In the present invention, flow field calculation is carried out for a typical double-chamber lime kiln, and the calculation results are as follows: Figure 6As shown. According to the existing 600t / d typical double-chamber kiln production data, the flue gas volume in the calcining section is much larger than the gas flow in the cooling section, and the volume ratio is generally around 2.2~2.3. As can be seen from the figure, the flue gas flowing downward in the calcining chamber and the cooling airflow flowing upward in the cooling section converge at the annular channel (i.e., the hot flue gas connection channel) and form a dividing interface. Above the dividing interface is the high-temperature flue gas in the calcining section, and below the dividing interface is the high-temperature cooling airflow in the cooling section. In the prior art, both airflows are transported to the heat storage chamber through an annular channel for utilization. Since the concentration of carbon dioxide in the high-temperature cooling airflow is relatively low, the concentration of carbon dioxide in the high-temperature flue gas will be diluted after it is merged into the high-temperature flue gas. This is why the CO2 concentration of the flue gas at the tail end of the existing conventional lime kiln is relatively low. Therefore, in the present invention, by opening a hot flue gas vent at the lower part of the side wall of the calcining chamber and an air vent at the upper part of the side wall of the cooling chamber, the high-temperature flue gas in the calcining section and the high-temperature cooling airflow in the cooling section can be diverted, and the high-temperature flue gas in the calcining section is directly transported to the heat storage chamber through the hot flue gas connecting channel to store heat for the material, and the high-temperature cooling airflow from the cooling section is transported to the indirect heat exchanger to exchange heat with the cold flue gas discharged from the heat storage chamber and transfer heat to the cold flue gas. The cold flue gas after heat exchange eventually enters the heat storage chamber through the hot flue gas connecting channel to store heat for the material. In other words, the present invention realizes the recycling of waste heat by diverting the high-temperature cooling airflow in the cooling section and exchanging heat with the cold flue gas, while also ensuring that the carbon dioxide concentration in the flue gas is not diluted.

[0019] In the present invention, room temperature air is used to cool high temperature lime, enters the kiln body from the cooling air inlet at the bottom of the cooling section, exchanges heat with the high temperature lime, and cools the high temperature lime. The room temperature air is heated to above 900°C, enters the plate heat exchanger from the air outlet at the top of the cooling section, and transfers the waste heat to the cold flue gas discharged from the top of the heat storage chamber. It should be noted that when the system is running stably, the high-concentration CO2 flue gas of about 150°C discharged from the top of the heat storage chamber generally needs to be dedusted and dehydrated before circulation. A part (generally preferably about 20% of the total heat storage flue gas) of the heat storage flue gas enters the plate heat exchanger to exchange heat with the high-temperature air passing through the cooling section, recovering the waste heat of the high-temperature cooling air, and then enters the hot flue gas connecting channel to mix with the calcination flue gas and enters the heat storage chamber, exchanges heat with the limestone in the heat storage chamber, and is finally discharged from the top of the heat storage chamber; a part (generally preferably about 35% of the total heat storage flue gas) of the heat storage flue gas is sent to the calcination chamber to replace the nitrogen in the combustion-supporting air to adjust the flue gas temperature of pure oxygen combustion to meet the temperature requirements of limestone calcination (generally not exceeding 1200°C), and the remaining part of the heat storage flue gas is sent to the compressor for compression, condensation and purification to obtain high-purity CO2.

[0020] In the present invention, the first vertical chamber and the second vertical chamber periodically and alternately serve as the calcining chamber and the heat storage chamber. When either of the first vertical chamber and the second vertical chamber is the calcining chamber, the other is the heat storage chamber. It should be noted that when either of the first vertical chamber and the second vertical chamber is the calcining chamber, its hot flue gas vent, air vent, material inlet, oxygen inlet, circulating flue gas inlet and cooling air inlet are all in an open state, while the cold flue gas vent is in a closed state. When either of the first vertical chamber and the second vertical chamber is the heat storage chamber, its air vent, material inlet, oxygen inlet, circulating flue gas inlet and cooling air inlet are all in a closed state, while the hot flue gas vent and the cold flue gas vent are in an open state. It can be adjusted in real time according to the actual working conditions.

[0021] In the present invention, when the lime kiln system of the present invention is used for production, the combustion-supporting air is the circulating flue gas, in which the CO2 concentration will be greatly increased, but the flue gas volume in the calcining section will be slightly reduced. It can be known through calculation that when the CO2 concentration in the flue gas reaches about 80%, the volume ratio of the flue gas volume in the calcining 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 possibility of the flue gas in the calcining section entering the indirect heat exchanger downward is much greater than the possibility of the cooling air entering the annular channel upward. In order to solve this problem, the present invention improves the structure of the connection of the existing annular channel (i.e., the hot flue gas connection channel) as follows Figure 3 A fence-type air permeable plate and a vertical baffle are added at the connection between the first hot flue gas outlet, the second hot flue gas outlet and the hot flue gas connecting channel, in order to guide the flue gas from the upper calcining section to the hot flue gas connecting channel as smoothly as possible, and at the same time prevent the cooling air from the lower cooling section from entering the hot flue gas connecting channel upward, and ensure that the cooling air from the cooling section is guided to the plate heat exchanger as much as possible.

[0022] In the present invention, it should be noted that the fence-type air permeable plate is mainly arranged at the first hot flue gas outlet and the second hot flue gas outlet, and its grid hole is designed to be inclined from top to bottom, specifically, one end of the grid hole close to the hot flue gas connecting channel is lower than the other end. In other words, whether the first vertical chamber or the second vertical chamber acts as a calcining chamber, according to the direction of the flue gas, the inclined direction of the grid hole is from top to bottom, which is conducive to the hot flue gas being able to smoothly enter the hot flue gas connecting channel, and at the same time, it can also prevent the cooling airflow below from entering the hot flue gas connecting channel to a certain extent. The vertical baffle is suspended at the bottom end of the fence-type air permeable plate, that is, the vertical baffle extends downward below the hot flue gas outlet to form a baffle with a certain vertical height, which helps to prevent the hot flue gas from flowing downward and entering the plate heat exchanger.

[0023] In the present invention, the indirect heat exchanger is a plate heat exchanger, and the plate heat exchanger has an air channel and a smoke channel that are not connected to each other. The inlet and outlet of the air channel are the air inlet and air outlet of the indirect heat exchanger, and the inlet and outlet of the smoke channel are the smoke inlet and smoke outlet of the indirect heat exchanger. The air channel is for the high-temperature cooling airflow from the cooling section to pass through, and the smoke channel is for the heat storage flue gas from the heat storage chamber to pass through, that is, through the dual-channel design of the air channel and the smoke channel, the high-temperature cooling airflow from the cooling section and the heat storage flue gas from the heat storage chamber can only achieve heat exchange, and almost no effect on the atmosphere composition of each of the two.

[0024] In the present invention, a gas component detector is provided at the air outlet of the plate heat exchanger or on the exhaust pipe to monitor the CO2 concentration in the cooling air in real time, and it is possible to diagnose in real time whether the flue gas from the calcining section flows downward and enters the cooling air flow and the proportion of the mixture. In order to separate the calcining flue gas and the cooling air flow to the greatest extent, the present invention can be adjusted in two ways. The first way is to design the vertical baffle as an adjustable telescopic baffle (such as a folding telescopic plate or a sleeve-type telescopic plate), and control it by adjusting the height of the vertical baffle. For example, the cooling air component is detected at the cooling air outlet of the plate heat exchanger. When the CO2 concentration is detected to be more than 10%, the downward height of the vertical baffle is increased (the adjustment of the height of the vertical baffle can be manually adjusted or an independent automatic drive device can be additionally provided for automatic feedback adjustment), which can more effectively block the calcining section flue gas from entering the heat exchanger, and facilitate the calcining section flue gas to smoothly enter the hot flue gas connection channel. If the operating conditions are still not met when the hanging baffle is adjusted to the maximum height, the second solution is to increase the flow resistance of the cooling air in the heat exchanger (for example, by installing a resistance control valve in front of the air outlet of the heat exchanger to adjust the system resistance and thus the inlet pressure). At this time, the cooling air flow remains unchanged, and the cooling air supply pressure at the bottom of the kiln also needs to be increased accordingly. Through the above operations, the air pressure at the inlet of the plate heat exchanger increases, which can also prevent the calcination flue gas from above from entering the plate heat exchanger.

[0025] In the present invention, it should be noted that when a plate heat exchanger is used for heat exchange treatment, the preferred operating scheme is to use a plate heat exchanger to transfer the heat of the hot air from the cooling section to the heat storage flue gas from the heat storage section, and the hot air outlet temperature of the plate heat exchanger is generally designed to be lower than 200°C, and the heat storage flue gas outlet temperature is generally above 600°C.

[0026] In the present invention, the height of the first vertical chamber and the second vertical chamber is 3-100 m, preferably 5-80 m, more preferably 10-50 m, and further preferably 20-30 m. The inner diameter of the first vertical chamber and the second vertical chamber is 1-30 m, preferably 2-20 m, more preferably 3-15 m, and further preferably 4-8 m. The inner diameter of the hot flue gas connecting channel is 0.3-2 m, preferably 0.5-1 m, and further preferably 0.6-0.8 m.

[0027] Compared with the prior art, the beneficial technical effects of the present invention are as follows: 1: The present invention separates and disposes the calcination section flue gas from the cooling airflow, and circulates the heat storage flue gas and the high-temperature cooling airflow after heat exchange. On the basis of not changing the existing furnace cooling section structure and thus avoiding the reverse reaction of high-temperature lime, it not only ensures the cooling effect but also realizes the cyclic enrichment of carbon dioxide in the calcination flue gas, which is conducive to realizing low-cost carbon dioxide capture operations.

[0028] 2: The present invention also realizes the separate monitoring and flexible regulation of calcination flue gas and high-temperature cooling airflow by arranging a gas composition detector at the air outlet of the indirect heat exchanger to monitor the CO2 concentration in the cooling air in real time and coordinates the airflow diversion regulating mechanism at the flue gas outlet at the bottom of the side wall of the combustion chamber, which is beneficial to ensure that the calcination flue gas and the high-temperature cooling airflow are diverted as smoothly as possible and realize the stable operation of the system.

[0029] 3: The lime kiln system of the present invention has a simple overall structure, is easy to adjust and operate, and can realize continuous production. At the same time, the cooling structure of the system is fully retained to achieve sufficient and uniform cooling of the material. In addition, it also has the advantages of high overall production efficiency and low maintenance cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is an existing parallel flow regenerative double-chamber lime shaft kiln.

[0031] Figure 2 It is a simplified structural diagram of the lime kiln system of the present invention.

[0032] Figure 3 It is a partial enlarged view of the hot flue gas vent and the air vent of the lime kiln system of the present invention.

[0033] Figure 4 It is a schematic diagram of the overall structure of the lime kiln system of the present invention.

[0034] Figure 5 This is the temperature reduction and weight gain curve of high-temperature CaO cooling process.

[0035] Figure 6 This is the flow field distribution diagram of the parallel flow regenerative double-chamber lime shaft kiln.

[0036] Figure numerals: 1: first vertical chamber; 101: first hot flue gas outlet; 102: first air outlet; 103: first cold flue gas outlet; 104: first material inlet; 105: first oxygen inlet; 106: first circulating flue gas inlet; 107: first cooling air inlet; 2: second vertical chamber; 201: second hot flue gas outlet; 202: second air outlet; 203: second cold flue gas outlet; 204: second material inlet; 205: second oxygen inlet; 206: second circulating flue gas outlet Air inlet; 207: second cooling air inlet; 3: indirect heat exchanger; 301: air exhaust duct; 302: gas composition detector; 303: exhaust fan; 4: hot flue gas connection channel; 5: air flow diversion adjustment mechanism; 501: fence-type air permeable plate; 502: vertical baffle; 6: dust collector; 7: compressor; L1: first flue gas duct; L2: second flue gas duct; L3: third flue gas duct; L4: fourth flue gas duct; L5: fifth flue gas duct; L6: sixth flue gas duct. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is illustrated below by way of example, and the scope of protection requested by the present invention includes but is not limited to the following embodiments.

[0038] A lime kiln system with independent circulation of carbon-rich flue gas, the lime kiln system 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 have the same structure, both comprising a combustion chamber and a cooling chamber connected in series from top to bottom. A first hot flue gas vent 101 is provided at the lower part of the side wall of the combustion chamber of the first vertical chamber 1, a first air vent 102 is provided at the upper part of the side wall of the cooling chamber of the first vertical chamber 1, a first cold flue gas vent 103, a first material inlet 104, a first oxygen inlet 105 and a first circulating flue gas inlet 106 are also provided at the top of the combustion chamber of the first vertical chamber 1, and a first cooling air inlet 107 is also provided at the bottom of the cooling chamber of the first vertical chamber 1. A second hot flue gas vent 201 is opened at the lower part of the side wall of the second vertical chamber 2 combustion chamber, a second air vent 202 is opened at the upper part of the side wall of the second vertical chamber 2 cooling chamber, a second cold flue gas vent 203, a second material inlet 204, a second oxygen inlet 205 and a second circulating flue gas inlet 206 are also opened at the top of the second vertical chamber 2 combustion chamber, and a second cooling air inlet 207 is also opened at the bottom of the second vertical chamber 2 cooling chamber.

[0039] The indirect heat exchanger 3 is arranged between the first vertical chamber 1 and the second vertical chamber 2, and an air inlet, an air outlet, a smoke inlet and a smoke outlet are provided on the indirect heat exchanger 3. The first hot smoke outlet 101 and the second hot smoke outlet 201 are connected through a hot smoke connecting channel 4. The first air outlet 102 and the second air outlet 202 are independently connected to the air inlet of the indirect heat exchanger 3. The air outlet of the indirect heat exchanger 3 is connected to an air exhaust duct 301. The first cold smoke outlet 103 and the second cold smoke outlet 203 are each connected to the smoke inlet of the indirect heat exchanger 3 through an independent pipeline, and each is connected to the second circulating smoke inlet 206 and the first circulating smoke inlet 106 through an independent pipeline. The smoke outlet of the indirect heat exchanger 3 is connected to the hot smoke connecting channel 4.

[0040] Preferably, the first hot flue gas vent 101 is opened at the bottom end of the combustion chamber side wall of the first vertical chamber 1, and the first air vent 102 is opened at the top end of the cooling chamber side wall of the first vertical chamber 1. The second hot flue gas vent 201 is opened at the bottom end of the combustion chamber side wall of the second vertical chamber 2, and the second air vent 202 is opened at the top end of the cooling chamber side wall of the second vertical chamber 2. An airflow splitting regulating mechanism 5 is independently provided between the first hot flue gas vent 101 and the first air vent 102, and between the second hot flue gas vent 201 and the second air vent 202.

[0041] Preferably, the air flow diversion and adjustment mechanism 5 includes a fence-type air permeable plate 501 and a vertical baffle 502. The first hot smoke outlet 101 and the second hot smoke outlet 201 are each independently provided with a fence-type air permeable plate 501. The vertical baffle 502 is provided at the lower end of the fence-type air permeable plate 501 and extends downward into the first air outlet 102 or the second air outlet 202. Preferably, the vertical baffle 502 is an adjustable telescopic baffle. Preferably, in the horizontal direction, there is a horizontal spacing between the vertical baffle 502 and the first air outlet 102 and between the vertical baffle 502 and the second air outlet 202.

[0042] Preferably, the indirect heat exchanger 3 is a plate heat exchanger having an air channel and a smoke channel which are not connected to each other. The inlet and outlet of the air channel are the air inlet and air outlet of the indirect heat exchanger 3, and the inlet and outlet of the smoke channel are the smoke inlet and smoke outlet of the indirect heat exchanger 3.

[0043] Preferably, a gas component detector 302 is provided at the air outlet of the indirect heat exchanger 3 or on the exhaust pipe 301. An exhaust fan 303 is also connected to the exhaust end of the exhaust pipe 301.

[0044] Preferably, a plurality of first hot flue gas openings 101 are provided along the circumferential direction of the combustion chamber side wall of the first vertical chamber 1, and a plurality of second hot flue gas openings 201 are provided along the circumferential direction of the combustion chamber side wall of the second vertical chamber 2. One end of the hot flue gas connection channel 4 surrounds the combustion chamber of the first vertical chamber 1 and is in communication with the plurality of first hot flue gas openings 101 in both directions, and the other end of the hot flue gas connection channel 4 surrounds the combustion chamber of the second vertical chamber 2 and is in communication with the plurality of second hot flue gas openings 201 in both directions.

[0045] Preferably, the lime kiln system further includes a dust collector 6. The first cold flue gas port 103 is connected to the air inlet of the dust collector 6 through the first flue gas duct L1. The second cold flue gas port 203 is connected to the air inlet of the dust collector 6 through the second flue gas duct L2. The exhaust port of the dust collector 6 is connected to the flue gas inlet of the indirect heat exchanger 3 through the third flue gas duct L3.

[0046] Preferably, a fourth smoke duct L4 connected to the first circulating smoke inlet 106 and a fifth smoke duct L5 connected to the second circulating smoke inlet 207 are led out from the third smoke duct L3.

[0047] Preferably, the lime kiln system further comprises a compressor 7. The gas inlet of the compressor 7 is connected to the third flue gas duct L3 through the sixth flue gas duct L6.

[0048] Preferably, the lime kiln system further comprises a dehumidifier 8. The dehumidifier 8 is arranged on the third flue gas duct L3. Gas valves are independently arranged on the first flue gas duct L1, the second flue gas duct L2, the third flue gas duct L3, the fourth flue gas duct L4, the fifth flue gas duct L5 and the sixth flue gas duct L6. Example 1

[0049] like Figure 2-4As shown, a lime kiln system with independent circulation of carbon-rich flue gas, the lime kiln system includes 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 have the same structure, both including a combustion chamber and a cooling chamber connected in series from top to bottom. A first hot flue gas vent 101 is provided at the lower part of the side wall of the combustion chamber of the first vertical chamber 1, a first air vent 102 is provided at the upper part of the side wall of the cooling chamber of the first vertical chamber 1, a first cold flue gas vent 103, a first material inlet 104, a first oxygen inlet 105 and a first circulating flue gas inlet 106 are also provided at the top of the combustion chamber of the first vertical chamber 1, and a first cooling air inlet 107 is also provided at the bottom of the cooling chamber of the first vertical chamber 1. A second hot flue gas vent 201 is opened at the lower part of the side wall of the second vertical chamber 2 combustion chamber, a second air vent 202 is opened at the upper part of the side wall of the second vertical chamber 2 cooling chamber, a second cold flue gas vent 203, a second material inlet 204, a second oxygen inlet 205 and a second circulating flue gas inlet 206 are also opened at the top of the second vertical chamber 2 combustion chamber, and a second cooling air inlet 207 is also opened at the bottom of the second vertical chamber 2 cooling chamber.

[0050] The indirect heat exchanger 3 is arranged between the first vertical chamber 1 and the second vertical chamber 2, and an air inlet, an air outlet, a smoke inlet and a smoke outlet are provided on the indirect heat exchanger 3. The first hot smoke outlet 101 and the second hot smoke outlet 201 are connected through a hot smoke connecting channel 4. The first air outlet 102 and the second air outlet 202 are independently connected to the air inlet of the indirect heat exchanger 3. The air outlet of the indirect heat exchanger 3 is connected to an air exhaust duct 301. The first cold smoke outlet 103 and the second cold smoke outlet 203 are each connected to the smoke inlet of the indirect heat exchanger 3 through an independent pipeline, and each is connected to the second circulating smoke inlet 206 and the first circulating smoke inlet 106 through an independent pipeline. The smoke outlet of the indirect heat exchanger 3 is connected to the hot smoke connecting channel 4. Example 2

[0051] Example 1 is repeated, except that the first hot flue gas port 101 is opened at the bottom end of the combustion chamber side wall of the first vertical chamber 1, and the first air port 102 is opened at the top end of the cooling chamber side wall of the first vertical chamber 1. The second hot flue gas port 201 is opened at the bottom end of the combustion chamber side wall of the second vertical chamber 2, and the second air port 202 is opened at the top end of the cooling chamber side wall of the second vertical chamber 2. An airflow splitting regulating mechanism 5 is independently provided between the first hot flue gas port 101 and the first air port 102, and between the second hot flue gas port 201 and the second air port 202. Example 3

[0052] Example 2 is repeated, except that the airflow splitting and regulating mechanism 5 includes a fence-type air permeable plate 501 and a vertical baffle 502. The fence-type air permeable plate 501 is independently provided on the first hot smoke outlet 101 and the second hot smoke outlet 201. The vertical baffle 502 is provided at the lower end of the fence-type air permeable plate 501 and extends downward into the first air outlet 102 or the second air outlet 202. Preferably, the vertical baffle 502 is an adjustable telescopic baffle. Example 4

[0053] The third embodiment 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 . Example 5

[0054] Example 4 is repeated, except that the indirect heat exchanger 3 is a plate heat exchanger, and the plate heat exchanger has an air channel and a smoke channel that are not connected to each other. The inlet and outlet of the air channel are the air inlet and air outlet of the indirect heat exchanger 3, and the inlet and outlet of the smoke channel are the smoke inlet and smoke outlet of the indirect heat exchanger 3. Example 6

[0055] The embodiment 5 is repeated, except that a gas component detector 302 is further provided at the air outlet of the indirect heat exchanger 3 or on the exhaust pipe 301. An exhaust fan 303 is further connected to the exhaust end of the exhaust pipe 301. Example 7

[0056] Example 6 is repeated, except that a plurality of first hot flue gas openings 101 are opened along the circumferential direction of the side wall of the combustion chamber of the first vertical chamber 1, and a plurality of second hot flue gas openings 201 are opened along the circumferential direction of the side wall of the combustion chamber of the second vertical chamber 2. One end of the hot flue gas connection channel 4 surrounds the combustion chamber of the first vertical chamber 1 and is in communication with the plurality of first hot flue gas openings 101 in both directions, and the other end of the hot flue gas connection channel 4 surrounds the combustion chamber of the second vertical chamber 2 and is in communication with the plurality of second hot flue gas openings 201 in both directions. Example 8

[0057] Example 7 is repeated, except that the lime kiln system further includes a dust collector 6. The first cold flue gas port 103 is connected to the air inlet of the dust collector 6 through the first flue gas duct L1. The second cold flue gas port 203 is connected to the air inlet of the dust collector 6 through the second flue gas duct L2. The exhaust port of the dust collector 6 is connected to the flue gas inlet of the indirect heat exchanger 3 through the third flue gas duct L3. Example 9

[0058] The embodiment 8 is repeated, except that a fourth smoke duct L4 connected to the first circulating smoke inlet 106 and a fifth smoke duct L5 connected to the second circulating smoke inlet 207 are led out from the third smoke duct L3. Example 10

[0059] Example 9 is repeated, except that the lime kiln system further includes a compressor 7. The gas inlet of the compressor 7 is connected to the third flue gas duct L3 through the sixth flue gas duct L6. Embodiment 11

[0060] Example 10 is repeated, except that the lime kiln system further includes a dehumidifier 8. The dehumidifier 8 is arranged on the third flue gas duct L3. The first flue gas duct L1, the second flue gas duct L2, the third flue gas duct L3, the fourth flue gas duct L4, the fifth flue gas duct L5 and the sixth flue gas duct L6 are all independently provided with air valves for adjusting the airflow size of each duct.

[0061] Application Example 1 The lime kiln system with independent circulation of carbon-rich flue gas described in Example 11 is used to produce lime and enrich and recover carbon dioxide: The first vertical chamber 1 is used as a combustion chamber, and the second vertical chamber 2 is used as a heat storage chamber. The first hot flue gas vent 101, the first air vent 102, the first material inlet 104, the first oxygen inlet 105, the first circulating flue gas inlet 106, and the first cooling gas inlet 107 of the first vertical chamber 1 are all opened, while the first cold flue gas vent 103 is closed. The second hot flue gas vent 201 and the second cold flue gas vent 203 of the second vertical chamber 2 are opened, while the second air vent 202, the second material inlet 204, the second oxygen inlet 205, the second circulating flue gas inlet 206, and the second cooling gas inlet 207 are all closed.

[0062] The lime raw material and coal powder are introduced into the combustion chamber from the first material inlet 104, and pure oxygen and a part of the heat storage flue gas discharged from the heat storage chamber (specifically, the flue gas accounting for about 35% of the total heat storage flue gas) are introduced through the first oxygen inlet 105 and the first circulating flue gas inlet 106 as a combustion-supporting gas to calcine the lime raw material, and the calcination temperature is 1100°C. The calcined material goes down into the cooling chamber and is contacted with the room temperature air blown in from the first cooling air inlet 107 for countercurrent heat exchange and cooling, and is then discharged from the material outlet at the bottom of the cooling chamber. During the calcination and cooling process, the calcination flue gas generated in the combustion chamber passes through the first hot flue gas port 101, the hot flue gas connecting channel 4 and the second hot flue gas port 201 in turn and enters the heat storage chamber to preheat the material therein. The high-temperature cooling airflow generated in the cooling chamber passes through the first air port 102 and enters the plate heat exchanger to conduct countercurrent heat exchange with the part of the heat storage flue gas (specifically, the flue gas accounting for about 20% of the total amount of the heat storage flue gas) discharged from the second cold flue gas port 203 at the top of the heat storage chamber that has been subjected to dust removal and water removal treatment in turn. After the heat exchange, the heat storage flue gas is heated to about 760°C and enters the hot flue gas connecting channel 4 to merge with the calcination flue gas and then enters the heat storage chamber. The high-temperature cooling airflow after heat exchange is cooled to about 155°C (it can be further discharged after waste heat utilization). After the system runs stably, it is detected that the concentration of carbon dioxide in the thermal storage flue gas is stable at above 80%. At this time, part of the thermal storage flue gas (specifically, the flue gas accounting for about 45% of the total thermal storage 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 in that: The lime kiln system comprises 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) have the same structure, both comprising a combustion chamber and a cooling chamber connected in series from top to bottom; a first hot flue gas vent (101) is provided at the lower part of the side wall of the combustion chamber of the first vertical chamber (1), a first air vent (102) is provided at the upper part of the side wall of the cooling chamber of the first vertical chamber (1), and a first cold flue gas vent (103), a first material inlet (104), a first oxygen inlet (105) and a first circulating flue gas inlet (106) are also provided at the top of the combustion chamber of the first vertical chamber (1). A first cooling air inlet (107) is provided at the bottom of the cooling chamber of the first vertical chamber (1); a second hot flue gas outlet (201) is provided at the lower part of the side wall of the combustion chamber of the second vertical chamber (2); a second air outlet (202) is provided at the upper part of the side wall of the cooling chamber of the second vertical chamber (2); a second cold flue gas outlet (203), a second material inlet (204), a second oxygen inlet (205) and a second circulating flue gas inlet (206) are provided at the top of the combustion chamber of the second vertical chamber (2); and a second cooling air inlet (207) is provided at the bottom of the cooling chamber of the second vertical chamber (2); The indirect heat exchanger (3) is arranged between the first vertical chamber (1) and the second vertical chamber (2), and is provided with an air inlet, an air outlet, a smoke inlet and a smoke outlet on the indirect heat exchanger (3); the first hot smoke outlet (101) and the second hot smoke outlet (201) are connected via a hot smoke connecting channel (4); the first air outlet (102) and the second air outlet (202) are independently connected to the air inlet of the indirect heat exchanger (3); the air outlet of the indirect heat exchanger (3) is connected to an air exhaust duct (301); the first cold smoke outlet (103) and the second cold smoke outlet (203) are each connected to the smoke inlet of the indirect heat exchanger (3) via an independent pipeline, and are each connected to the second circulating smoke inlet (206) and the first circulating smoke inlet (106) via an independent pipeline; the smoke outlet of the indirect heat exchanger (3) is connected to the hot smoke connecting channel (4).

2. The lime kiln system according to claim 1, characterized in that: The first hot flue gas vent (101) is provided at the bottom end of the side wall of the combustion chamber of the first vertical chamber (1), and the first air vent (102) is provided at the top end of the side wall of the cooling chamber of the first vertical chamber (1); the second hot flue gas vent (201) is provided at the bottom end of the side wall of the combustion chamber of the second vertical chamber (2), and the second air vent (202) is provided at the top end of the side wall of the cooling chamber of the second vertical chamber (2); and airflow splitting and regulating mechanisms (5) are independently provided between the first hot flue gas vent (101) and the first air vent (102), and between the second hot flue gas vent (201) and the second air vent (202), respectively.

3. The lime kiln system according to claim 2, characterized in that: The airflow splitting and regulating 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 smoke outlet (101) and the second hot smoke outlet (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 outlet (102) or the second air outlet (202); preferably, the vertical baffle (502) is an adjustable telescopic baffle; preferably, in the horizontal direction, there is a horizontal spacing between the vertical baffle (502) and the first air outlet (102) and between the vertical baffle (502) and the second air outlet (202).

4. The lime kiln system according to any one of claims 1 to 3, characterized in that: The indirect heat exchanger (3) is a plate heat exchanger having an air channel and a smoke channel which are not interconnected; the inlet and outlet of the air channel are the air inlet and air outlet of the indirect heat exchanger (3), and the inlet and outlet of the smoke channel are the smoke inlet and smoke outlet of the indirect heat exchanger (3).

5. The lime kiln according to any one of claims 1 to 4, characterized in that: A gas composition detector (302) is also provided at the air outlet of the indirect heat exchanger (3) or on the exhaust pipe (301); and an exhaust fan (303) is also connected to the exhaust end of the gas exhaust pipe (301).

6. The lime kiln system according to any one of claims 1 to 5, characterized in that: A plurality of first hot flue gas openings (101) are opened along the circumferential direction of the side wall of the combustion chamber of the first vertical chamber (1), and a plurality of second hot flue gas openings (201) are opened along the circumferential direction of the side wall of the combustion chamber of the second vertical chamber (2); one end of the hot flue gas connection channel (4) surrounds the combustion chamber of the first vertical chamber (1) and is in communication with the plurality of first hot flue gas openings (101) in all directions, and the other end of the hot flue gas connection channel (4) surrounds the combustion chamber of the second vertical chamber (2) and is in communication with the plurality of second hot flue gas openings (201) in all directions.

7. The lime kiln system according to any one of claims 1 to 6, characterized in that: The lime kiln system also includes a dust collector (6); a first cold flue gas outlet (103) is connected to an air inlet of the dust collector (6) via a first flue gas duct (L1); a second cold flue gas outlet (203) is connected to an air inlet of the dust collector (6) via a second flue gas duct (L2); and an exhaust port of the dust collector (6) is connected to a flue gas inlet of an indirect heat exchanger (3) via a third flue gas duct (L3).

8. The lime kiln system according to claim 7, characterized in that: A fourth smoke duct (L4) connected to the first circulating smoke inlet (106) and a fifth smoke duct (L5) connected to the second circulating smoke inlet (207) are also led out from the third smoke duct (L3).

9. The lime kiln system according to claim 7 or 8, characterized in that: The lime kiln system also includes a compressor (7); a gas inlet of the compressor (7) is connected to the third flue gas duct (L3) through a sixth flue gas duct (L6).

10. The lime kiln system according to any one of claims 7 to 9, characterized in that: The lime kiln system further comprises a dehydrator (8); the dehydrator (8) is arranged on the third flue gas duct (L3); and gas valves are independently arranged on the first flue gas duct (L1), the second flue gas duct (L2), the third flue gas duct (L3), the fourth flue gas duct (L4), the fifth flue gas duct (L5) and the sixth flue gas duct (L6).

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