A low-nitrogen combustion decomposition furnace and lime calcining system

Abstract

The application provides a low-nitrogen combustion decomposition furnace and a lime calcining system, and belongs to the technical field of limestone calcining, and specifically comprises: a decomposition furnace body for calcining and decomposing limestone; a first material inlet, a second material inlet, a first combustion-supporting gas inlet, a second combustion-supporting gas inlet, a first fuel inlet and a second fuel inlet are arranged on the decomposition furnace body. By controlling the different proportions of the two routes of the material, the fuel and the combustion-supporting gas, a combustion decomposition zone and a hot carbon reduction zone are formed in the furnace cavity of the decomposition furnace body. In the combustion decomposition zone, the proportion of the combustion-supporting gas is relatively high, so that the material can be fully combusted; in the hot carbon reduction zone, the proportion of the combustion-supporting gas is relatively low, so that insufficient combustion is carried out in this zone, and the fuel is used for inhibition and reduction, so that the nitrogen oxides passing through this zone are subjected to a reduction reaction to become carbon dioxide and nitrogen gas and are discharged, the content of the nitrogen oxides is greatly reduced, and the treatment process of the nitrogen oxides by the subsequent exhaust process is reduced.

Description

Technical Field

[0001] This application relates to the field of limestone calcination technology, and more specifically, to a low-NOx combustion decomposition furnace and a limestone calcination system. Background Technology

[0002] Currently, domestic lime calcination systems mainly use vertical kilns and rotary kilns, employing lumpy limestone as raw material. The lumpy limestone is crushed to a suitable particle size for preheating and calcination. The calcined limestone decomposes into quicklime, which then needs to be cooled before storage and transportation. During the calcination process, due to the high combustion temperature, nitrogen oxides may be produced. Nitrogen oxides are highly harmful to both the environment and human health; therefore, there is an urgent need for a combustion system that can minimize the generation of nitrogen oxides. Utility Model Content

[0003] The purpose of this application is to provide a low-NOx combustion decomposition furnace and a lime calcination system, which aims to solve the problem that nitrogen oxides are easily generated when the material combustion temperature is high in related technologies.

[0004] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description or may be learned by practice of this application.

[0005] According to a first aspect of this application, a low-NOx combustion decomposition furnace is provided, comprising:

[0006] A decomposition furnace body used for calcining and decomposing limestone.

[0007] The decomposition furnace body is provided with a first material inlet, a second material inlet, a first combustion-supporting gas inlet, a second combustion-supporting gas inlet, a first fuel inlet, and a second fuel inlet.

[0008] The first combustion-supporting gas inlet is located at the bottom of the decomposition furnace body. The first material inlet and the first fuel inlet are located above the first combustion-supporting gas inlet. The second material inlet and the second fuel inlet are located between the first combustion-supporting gas inlet and the second combustion-supporting gas inlet, and are located above the first material inlet and the first fuel inlet.

[0009] In one exemplary embodiment of this application, the second combustion-supporting gas inlet is located at the upper part of the decomposition furnace body, and the first fuel inlet, the second fuel inlet, and the first material inlet are all located between the first combustion-supporting gas inlet and the second combustion-supporting gas inlet.

[0010] In one exemplary embodiment of this application, the first fuel inlet, the first material inlet, the second fuel inlet, and the second material inlet are arranged sequentially from bottom to top on the decomposition furnace body.

[0011] In one exemplary embodiment of this application, a first constriction structure is provided below the decomposition furnace body, the position of the first combustion-supporting gas inlet is lower than the position of the first constriction structure, the position of the first fuel inlet corresponds to the position of the first constriction structure, and the position of the first material inlet is higher than the position of the first constriction structure.

[0012] In one exemplary embodiment of this application, the decomposition furnace body is further provided with a second narrowing structure, located above the second material inlet;

[0013] The second fuel inlet is positioned corresponding to the second constriction structure;

[0014] The positions of the second material inlet and the second combustion-supporting gas inlet are both higher than the position of the second constriction structure, and the position of the second combustion-supporting gas inlet is higher than the position of the second material inlet;

[0015] A preheating decomposition zone is formed between the first constriction structure and the second constriction structure, and a hot carbon reduction zone and a combustion decomposition zone are formed sequentially above the second constriction structure.

[0016] In one exemplary embodiment of this application, the proportion of material entering the decomposition furnace body through the first material inlet and the second material inlet is 50%-90% in the upper layer and 10%-50% in the lower layer;

[0017] The upper layer of the combustion air entering the decomposition furnace body through the first combustion gas inlet and the second combustion gas inlet has a proportion of 50%-90%, and the lower layer has a proportion of 10%-50%.

[0018] The proportion of fuel entering the upper layer of the decomposition furnace body through the first fuel inlet and the second fuel inlet is 50%-90%, and the proportion of fuel entering the lower layer is 10%-50%.

[0019] In one exemplary embodiment of this application, the combustion temperature of the combustion decomposition zone is controlled at 900℃-1000℃.

[0020] According to a second aspect of this application, a lime calcination system is provided, comprising the aforementioned low-NOx combustion decomposition furnace.

[0021] In one exemplary embodiment of this application, a preheating unit is further included, which is used to preheat the material, and the outlet of the preheating unit is divided into two paths and connected to the decomposition furnace body.

[0022] In one exemplary embodiment of this application, a cooling unit is further included. The cooling unit includes a suspension cooling furnace and a separation cyclone. The suspension cooling furnace is connected to the outlet of the decomposition furnace and is used to receive the calcined material. The separation cyclone is connected to the outlet of the suspension cooling furnace and is used to perform gas-solid separation on the cooled material. The separated gas is used as a combustion-supporting gas and is divided into two paths to enter the decomposition furnace.

[0023] The exemplary embodiments of this application may have some or all of the following beneficial effects:

[0024] The low-NOx combustion furnace provided in the example embodiment of this application includes a decomposition furnace body for calcining and decomposing limestone. The decomposition furnace body has a first material inlet, a second material inlet, a first combustion-supporting gas inlet, a second combustion-supporting gas inlet, a first fuel inlet, and a second fuel inlet. The first combustion-supporting gas inlet is located at the bottom of the decomposition furnace body, the first material inlet and the first fuel inlet are located above the first combustion-supporting gas inlet, and the second material inlet and the second fuel inlet are located between the first combustion-supporting gas inlet and the second combustion-supporting gas inlet. By providing two material inlets, two combustion-supporting gas inlets, and two fuel inlets on the decomposition furnace body, the material, combustion-supporting gas, and fuel enter the decomposition furnace body through two separate paths. By controlling the proportions of materials, combustion air, and fuel entering the decomposition furnace from two directions, a hot carbon reduction zone and a combustion decomposition zone are formed within the furnace cavity. The combustion decomposition zone is used to calcine the materials, while the hot carbon reduction zone is used to suppress and reduce nitrogen oxides produced during fuel combustion. For example, a higher proportion of combustion air in the combustion decomposition zone allows for complete combustion of the materials, while a lower proportion in the hot carbon reduction zone results in incomplete combustion. Simultaneously, the fuel suppresses and reduces nitrogen oxides in this zone, causing them to undergo a reduction reaction and be discharged as carbon dioxide and nitrogen, significantly reducing the nitrogen oxide content and alleviating the need for nitrogen oxide treatment in subsequent exhaust processes.

[0025] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0026] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0027] Figure 1 A schematic diagram of a low-NOx combustion decomposition furnace according to Embodiment 1 of this application is shown;

[0028] Figure 2 The diagram shows a schematic representation of the first narrowing structure and the second narrowing structure in Embodiment 1 of this application.

[0029] Figure 3 A schematic diagram of the lime calcination system in Embodiment 2 of this application is shown.

[0030] Explanation of reference numerals in the attached figures:

[0031] 1. Primary cyclone separator; 1-1. First flap valve; 1-2. Second flap valve; 2. Secondary cyclone separator; 2-1. Third flap valve; 3. Tertiary cyclone separator; 3-1. Fourth flap valve; 4. Quaternary cyclone separator; 4-1. Fifth flap valve; 4-2. Material distribution valve; 4-3. Sixth flap valve; 4-4. Seventh flap valve; 5. Fifth cyclone separator; 5-1. Eighth flap valve; 6. Decomposition furnace; 61. Material collection area; 62. Hot carbon reduction area; 63. Combustion decomposition area; 64. Second combustion gas inlet; 65. First combustion gas inlet; 66. First fuel inlet 67. First material inlet; 68. Second fuel inlet; 69. Second material inlet; 601. First narrowing structure; 602. Second narrowing structure; 603. Preheating decomposition zone; 6-1. Gate valve; 7. Fluidized bed suspension cooling furnace; 8. Separation cyclone; 8-1. Ninth flap valve; 10. Fluidizing blower; 11. Finished product conveyor; 12. Finished product warehouse; 13. High temperature blower; 14. Raw material mill; 15. Fuel mill; 16. Raw material warehouse; 17. Multi-stage suspension preheating unit; 18. Fluidized bed suspension cooling unit; 19. Suspension low-NOx combustion unit. Detailed Implementation

[0032] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this application will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore their detailed descriptions will be omitted. Furthermore, the drawings are merely illustrative of this application and are not necessarily drawn to scale.

[0033] Although relative terms such as "upper" and "lower" are used in this specification to describe the relative relationship of one component of an icon to another, these terms are used only for convenience, such as according to the orientation of the examples in the accompanying drawings. It is understood that if the device of the icon is flipped so that it is upside down, the component described as "upper" will become the component described as "lower." When a structure is "upper" of another structure, it may mean that the structure is integrally formed on the other structure, or that the structure is "directly" mounted on the other structure, or that the structure is "indirectly" mounted on the other structure through another structure.

[0034] The terms “a,” “one,” “the,” and “at least one” are used to indicate the existence of one or more elements / components / etc.; the terms “including” and “having” are used to indicate an open-ended inclusion and to mean that there may be other elements / components / etc. in addition to the listed elements / components / etc.; the terms “first” and “second” are used only as markers and are not a limitation on the number of objects.

[0035] Example 1

[0036] This embodiment provides a specific implementation of the low-NOx combustion decomposition furnace 6, such as... Figure 1 As shown, the furnace includes a decomposition furnace 6 for calcining and decomposing limestone. The decomposition furnace 6 has a first material inlet 67, a second material inlet 69, a first combustion gas inlet 65, a second combustion gas inlet 64, a first fuel inlet 66, and a second fuel inlet 68. The first material inlet 67, the first combustion gas inlet 65, and the first fuel inlet 66 are located at the lower part of the decomposition furnace 6. The second material inlet 69 and the second fuel inlet 68 are located between the first combustion gas inlet 65 and the second combustion gas inlet 64, and above the first material inlet 67 and the first fuel inlet 66.

[0037] Furthermore, the second combustion gas inlet 64 is located at the upper part of the decomposition furnace body 6. The first fuel inlet 66, the second fuel inlet 68, and the first material inlet 67 are all located between the first combustion gas inlet 65 and the second combustion gas inlet 64. Specifically, the first fuel inlet 66, the first material inlet 67, the second fuel inlet 68, and the second material inlet 69 are arranged sequentially from bottom to top on the decomposition furnace body 6. This arrangement allows different combustion zones to be formed between different inlets within the decomposition furnace body 6.

[0038] Furthermore, in the combustion decomposition zone 63, the proportion of combustion-supporting gas is relatively high, while the proportion of fuel and material is relatively low, allowing the material to burn completely. In the preheating decomposition zone 603, the proportion of combustion-supporting gas is relatively low, while the proportion of material and fuel is relatively high. Incomplete combustion of fuel produces carbon monoxide, which increases the combustion temperature of the material. As the material and fuel rise to the hot carbon reduction zone, the combustion-supporting gas is completely consumed. The nitrogen oxides produced in the preheating decomposition zone 603 are reduced here, converting them into carbon dioxide and nitrogen, reducing the need for exhaust gas treatment in subsequent processes and lowering environmental pollution. When the material rises to the combustion decomposition zone 63, the high proportion of combustion-supporting gas ensures complete combustion of the material.

[0039] Specifically, the furnace cavity of the decomposition furnace 6 is divided from bottom to top into a material collection zone 61, a preheating decomposition zone 603, a hot carbon reduction zone 62, and a combustion decomposition zone 63. The material collection zone 61 is used to collect the material deposited after calcination. The preheating decomposition zone 603 is used to heat the material. The combustion decomposition zone 63 is used to calcine the material (limestone). The hot carbon reduction zone 63 is used to suppress and reduce nitrogen oxides generated in the preheating decomposition zone 603 and fuel during combustion. The first material inlet 67, the first combustion gas inlet 65, and the first fuel inlet 66 are correspondingly set to the preheating decomposition zone 603. The material, combustion gas, and fuel are all divided into two streams and enter the decomposition furnace 6. The ratio of the material, combustion gas, and fuel entering the decomposition furnace 6 is controlled so that the hot carbon reduction zone 62 and the combustion decomposition zone 63 are formed in the furnace cavity of the decomposition furnace 6.

[0040] In this embodiment, the second combustion-supporting gas inlet is located above the thermal carbon reduction zone 62. When the combustion-supporting gas is introduced into the second gas inlet, a combustion decomposition zone 63 is formed above the thermal carbon reduction zone 62. Most of the combustion-supporting gas entering from the second gas inlet is in the combustion decomposition zone 63 above the thermal carbon reduction zone 62. When the materials and fuels flow upward under the carrying of the airflow, they will be fully burned and exhausted after passing through the combustion decomposition zone, thus avoiding the outflow of unburned materials and fuels.

[0041] In this embodiment, the first combustion-supporting gas inlet 65 is located between the collection zone 61 and the preheating and decomposition zone 603. The position of the first fuel inlet 66 is higher than the position of the first combustion-supporting gas inlet 65, and the position of the first material inlet 67 is higher than the position of the first combustion-supporting gas inlet 65. This design allows the combustion-supporting gas to enter from the first combustion-supporting gas inlet 65 and flow upward, thereby mixing and burning the fuel and material above. It also prevents the material and fuel from entering from below the first combustion-supporting gas inlet 65, which would make it difficult to fully mix them using the flow of the combustion-supporting gas.

[0042] Furthermore, a first constriction structure 601 is provided between the material collection zone 61 and the preheating decomposition zone 603 of the decomposition furnace 6. The position of the first combustion-supporting gas inlet 65 is lower than the position of the first constriction structure 601, the position of the first fuel inlet 66 corresponds to the position of the first constriction structure 601, and the position of the first material inlet 67 is higher than the position of the first constriction structure 601. When the combustion-supporting gas enters from the first combustion-supporting gas inlet 65, it flows upward through the first constriction structure 601, which changes the flow velocity and forms turbulence, accelerating the mixing of fuel and material. The first fuel inlet 66 is set at the position of the first constriction structure 601. Since the flow velocity of the combustion-supporting gas is faster at the first constriction structure 601, the fuel can be quickly mixed with the material above.

[0043] In this embodiment, the decomposition furnace 6 body is provided with a second constriction structure 602, which is located above the second material inlet 69. The second fuel inlet 68 is positioned corresponding to the second constriction structure 602. The positions of the second material inlet 69 and the second combustion gas inlet 64 are both higher than the position of the second constriction structure 602, and the position of the second combustion gas inlet 64 is higher than the position of the second material inlet 69. A hot carbon reduction zone 62 is formed between the first constriction structure 601 and the second constriction structure 602, and a combustion decomposition zone 63 is formed above the second constriction structure 602.

[0044] In this embodiment, the proportion of material in the upper layer of the furnace cavity of the decomposition furnace 6 is 50%-90%, and the proportion in the lower layer is 10%-50%; the proportion of combustion-supporting gas in the upper layer is 50%-90%, and the proportion in the lower layer is 10%-50%; the proportion of fuel in the upper layer is 50%-90%, and the proportion in the lower layer is 10%-50%. By controlling the proportion range of material, combustion-supporting gas, and fuel in the lower hot carbon reduction zone 62 and the upper combustion decomposition zone 63, the material is fully combusted and nitrogen oxides are eliminated as much as possible.

[0045] In this embodiment, the combustion temperature of the combustion decomposition zone 63 is controlled between 900℃ and 1000℃ to avoid generating too much thermal nitrogen oxides.

[0046] In this embodiment, the material is limestone, which becomes slaked lime after being calcined in the decomposition furnace 6; the fuel is pulverized coal, which can accelerate the combustion and decomposition of limestone. At the same time, pulverized coal can also inhibit and reduce the nitrogen oxides produced.

[0047] In this embodiment, the combustion-supporting gas is air, which provides oxygen for the calcination of the decomposition furnace 6 by introducing air.

[0048] In this embodiment, as Figure 2 As shown, the ratio of the first constriction structure 601 to the second constriction structure 602 is d / D = 0.5-0.9 and h / H = 0-0.5. The first fuel inlet 66 and the second fuel inlet 68 are both located at the constricted position.

[0049] Example 2

[0050] This embodiment provides a specific implementation of a lime calcination system, including the low-NOx calcination decomposition furnace 6 in Embodiment 1, and also includes a preheating unit. The preheating unit is used to preheat the material to reduce the heating time of the low-NOx calcination decomposition furnace 6. The outlet of the preheating unit is divided into two paths that are connected to the decomposition furnace 6 body, and the two paths are respectively connected to the first material inlet 67 and the second material inlet 69.

[0051] In this embodiment, a cooling unit is also included. The cooling unit includes a suspension cooling furnace and a separating cyclone 8. The suspension cooling furnace is connected to the outlet of the decomposition furnace 6 and is used to receive the calcined material. The separating cyclone 8 is connected to the outlet of the suspension cooling furnace and is used to perform gas-solid separation on the cooled material. The separated gas is divided into two paths as combustion-supporting gas and enters the decomposition furnace 6, namely the first combustion-supporting gas inlet 65 and the second combustion-supporting gas inlet 64. At this time, the combustion-supporting gas has just completed the heat exchange with the material and has a certain temperature, which further reduces the heating time of the decomposition furnace 6 and improves the calcination efficiency of the material.

[0052] like Figure 3 As shown, the system includes a multi-stage suspension preheating unit 17, a suspension low-NOx combustion unit 19, and a fluidized bed suspension cooling unit 18. The multi-stage suspension preheating unit 17 includes multiple sets of cyclones connected by connecting pipes. The suspension low-NOx combustion unit 19 includes a decomposition furnace 6, which is connected to the cyclones in the multi-stage suspension preheating unit 17. The decomposition furnace 6 is used to receive materials conveyed from the cyclones. The fluidized bed suspension cooling unit 18 includes a fluidized bed suspension cooling furnace 7 and two parallel-connected separation cyclones 8. The fluidized bed suspension cooling furnace 7 is used to receive and cool the materials after combustion in the decomposition furnace 6 and gas-solid separation in the cyclones. The two parallel-connected separation cyclones 8 are used to perform gas-solid separation on the materials cooled by the fluidized bed suspension cooling furnace 7 for storage or transportation to the finished product warehouse 12.

[0053] In this application, two parallel cyclones are set in the cooling unit for single-stage gas-solid separation. The cooled material only needs to pass through one of the separation cyclones 8 to complete the separation, which greatly reduces the system's operating resistance, power consumption, and thus cost. The two parallel separation cyclones 8 reduce the system's operating resistance while meeting separation efficiency requirements. In this application, the fluidized bed suspension cooling furnace 7 can receive the material separated by the end cyclones and cool it. During the cooling process, cold air enters the fluidized bed suspension cooling furnace 7, mixes with the material for heat exchange, and lowers the material's temperature. The fully mixed material and cold air enter the separation cyclone 8 for further heat exchange and simultaneous gas-solid separation. The material separated in the separation cyclone 8 is the finished product, which can be used for storage and transportation. The cold air enters from the bottom of the fluidized bed suspension cooling furnace 7 and flows upward. During the upward flow, it mixes with the material and carries the material upward, finally carrying it into the separation cyclone 8 for gas-solid separation.

[0054] The high-temperature fan 13 is connected to the first-stage cyclone 1 in the multi-stage suspension preheating unit 17. The high-temperature fan 13 is used to draw hot air flowing from the fluidized bed suspension cooling unit 18, the suspension low-NOx combustion unit 19, and the multi-stage suspension preheating unit 17, so that the hot air in the system is discharged from the combustion cooling section after passing through the multi-stage suspension preheating unit 17. During the process of material being transported from the multi-stage suspension preheating unit 17 to the suspension low-NOx combustion unit 19, it first exchanges heat with the hot air to complete the preheating, so that the material has a certain temperature when it enters the suspension low-NOx combustion unit 19, reducing the heating time of the material by the suspension low-NOx combustion unit 19. The fuel mill 15 is used to transport fuel to the decomposition furnace 6. Only after the fuel is transported can the material in the decomposition furnace 6 be calcined. The raw material mill 14 is used to provide material to the raw material silo 16. The raw material silo 16 is connected to the multi-stage suspension preheating unit 17. The material is transported from the raw material silo 16 to the multi-stage suspension preheating unit 17. The finished product silo 12 is used to receive the finished material after it has been cooled by the separation cyclone 8.

[0055] In this embodiment, the multi-stage suspension preheating unit 17 includes a primary cyclone 1, a secondary cyclone 2, a tertiary cyclone 3, a quaternary cyclone 4, and a quinary cyclone 5. A high-temperature fan 13 is connected to the primary cyclone 1. The inlet of the primary cyclone 1 is connected to the raw material silo 16. A first connecting duct is provided between the inlet of the primary cyclone 1 and the inlet of the secondary cyclone 2; a second connecting duct is provided between the inlet of the secondary cyclone 2 and the inlet of the tertiary cyclone 3; and a connecting duct is provided between the inlet of the tertiary cyclone 3 and the inlet of the quaternary cyclone 4. A fourth connecting duct is provided between the inlet of the third connecting duct, the inlet of the fourth-stage cyclone 4, and the inlet of the fifth-stage cyclone 5. The outlet of the first-stage cyclone 1 is connected to the second connecting duct, the outlet of the second-stage cyclone 2 is connected to the third connecting duct, and the outlet of the third-stage cyclone 3 is connected to the fourth connecting duct through material pipelines. The outlet of the fifth-stage cyclone 5 is connected to the fluidized bed suspension cooling furnace 7. The outlet of the fourth-stage cyclone 4 is connected to the material inlet of the decomposition furnace 6. The inlet of the fifth-stage cyclone 5 is connected to the material outlet at the top of the decomposition furnace 6.

[0056] The material conveying process is as follows: Material in raw material silo 16 enters the primary cyclone separator 1 through the first connecting duct. During conveying in the first connecting duct, material undergoes gas-air heat exchange, and the material is carried by the airflow into the primary cyclone separator 1 for gas-solid separation. After separation, the material enters the second connecting duct between the tertiary cyclone separator 3 and the secondary cyclone separator 2 for gas-air heat exchange, and is then carried by the airflow into the secondary cyclone separator 2 for gas-solid separation. After separation, the material enters the third connecting duct between the quaternary cyclone separator 4 and the tertiary cyclone separator 3 for gas-air heat exchange, and is then carried by the airflow into the secondary cyclone separator 2 for gas-solid separation. The material is introduced into the three-stage cyclone separator 3 for gas-solid separation. After separation, the material enters the fourth connecting duct between the five-stage cyclone separator 5 and the four-stage cyclone separator 4 for gas-material heat exchange, and is then introduced into the four-stage cyclone separator 4 for gas-solid separation. The separated material then enters the decomposition furnace 6, where it is calcined and decomposed. The decomposed material is divided into two paths: one path enters the five-stage cyclone separator 5 with the rising airflow and, after separation, enters the fluidized bed suspension cooling furnace 7; the other path settles to the bottom of the decomposition furnace 6 and enters the fluidized bed suspension cooling furnace 7. The material passes through a multi-stage suspension preheating unit 17 before entering the decomposition furnace 6, which pre-heats the material and reduces the calcination time in the decomposition furnace 6.

[0057] In this embodiment, a fluidizing blower 10 is also included. The outlet of the fluidizing blower 10 is connected to the fluidized bed suspension cooling furnace 7. The connection point between the fluidizing blower 10 and the fluidized bed suspension cooling furnace 7 is lower than the connection point between the fifth-stage cyclone 5, the decomposition furnace 6 and the fluidized bed suspension cooling furnace 7. That is, the connection point between the fluidizing blower 10 and the fluidized bed suspension cooling furnace 7 is located at the bottom of the fluidized bed suspension cooling furnace 7, so that air can move upward from the bottom of the fluidized bed suspension cooling furnace 7, causing the material to be in a suspended fluidized state in the fluidized bed suspension cooling furnace 7. Gas-solid heat exchange is performed. The heated gas flow enters the parallel-connected separation cyclone 8 from the top of the furnace for gas-solid separation. The hot gas, as combustion air, enters the decomposition furnace 6 through two paths, one above and one below. The flue gas generated in the material decomposition furnace 6 enters the multi-stage suspension preheating unit 17 from the top of the decomposition furnace 6. The flue gas from the first-stage cyclone 1 serves as a drying heat source and enters the raw material mill 14 and fuel mill 15 respectively via the high-temperature fan 13. The material exiting from the outlet of the separation cyclone 8 is the finished product, which is stored or transported to the finished product warehouse 12. At the same time, placing the inlet of the fluidizing fan 10 at the bottom of the fluidized bed suspension cooling furnace 7 can also prevent material collapse. The fluidizing fan 10 blows air upwards from the bottom of the fluidized bed suspension cooling furnace 7, preventing material from accumulating at the bottom of the fluidized bed suspension cooling furnace 7.

[0058] In this embodiment, a high-temperature fan 13 is also included. The high-temperature fan 13 is connected to the outlet of the first-stage cyclone 1. The extraction by the high-temperature fan 13 makes the cyclone in the multi-stage suspension preheating unit 17 under negative pressure. The outlet of the high-temperature fan 13 can also be connected to the raw material mill 14 and the fuel mill 15. The hot gas blown out by the high-temperature fan 13 can be used to preheat the raw material mill 14 and the fuel mill 15.

[0059] In this embodiment, the material separated from the four-stage cyclone 4 enters the decomposition furnace 6 in two separate streams. The material is distributed in two layers in the decomposition furnace 6, with the upper layer accounting for 50%-90% and the lower layer accounting for 10%-50%. Furthermore, an upper combustion decomposition zone 63 and a lower hot carbon reduction zone 62 are formed in the decomposition furnace 6. The distribution ratio of combustion air in the upper layer of the decomposition furnace 6 is 50%-90%, and the distribution ratio of combustion air in the lower layer is 10%-50%. The distribution ratio of fuel in the upper layer of the decomposition furnace 6 is 50%-90%, and the distribution ratio of fuel in the lower layer is 10%-50%. Through the different proportions of materials, combustion air, and fuel in the upper and lower layers, an upper combustion decomposition zone 63 and a lower hot carbon reduction zone 62 are formed in the decomposition furnace 6. If there is more material in the lower layer of the decomposition furnace 6 and less combustion air and fuel, the material will not burn completely, forming the lower hot carbon reduction zone 62, where a reduction reaction will occur. Most of the NOx produced by the fuel will react with CO in the reduction zone to become N2 and CO2. When there is more material in the upper layer of the decomposition furnace 6 and more combustion air and fuel, the material will burn completely, forming the combustion decomposition zone 63.

[0060] Furthermore, the combustion decomposition zone 63 is a concentrated heat release area. Adding materials to this zone can absorb heat and balance the temperature, keeping it stably controlled at 900-1000℃, thus avoiding the generation of excessive thermal nitrogen oxides. By controlling the temperature within this zone, limestone can be completely decomposed into lime (CaO) without the lime being over-burned into dead lime (lime calcined at temperatures above 1100℃). Unburned coal powder is ensured to burn completely by supplementing combustion air in the upper combustion decomposition zone 63.

[0061] In this embodiment, both the decomposition furnace 6 and the fluidized bed suspension cooling furnace 7 are equipped with a central constriction structure to create a jetting effect. When materials and fuel pass through the central constriction structure, the airflow velocity suddenly increases and the pressure changes, forming strong turbulence and mixing phenomena, avoiding laminar flow, and facilitating the full dispersion, mixing, and combustion of materials and fuel. Furthermore, the inlet of the fuel mill 15 on the decomposition furnace 6 is located at the constriction structure. Due to the limited space within the decomposition furnace 6, placing the fuel inlet at the constriction structure allows for greater dispersion of fuel upon entering the decomposition furnace 6. The increased airflow velocity at the central constriction structure position enables rapid fuel dispersion and combustion. Simultaneously, the fuel mill 15 enters the decomposition furnace 6 through two paths, upper and lower, preventing fuel accumulation within the decomposition furnace 6. This dual entry reduces fuel accumulation, accelerates the mixing of fuel and materials, and speeds up the combustion rate.

[0062] Furthermore, the central constriction structure is provided in multiple locations within the furnace, allowing a jetting effect to be generated at multiple locations within the furnace.

[0063] Furthermore, the outlet of the high-temperature fan 13 is connected to the raw material mill 14 and the fuel mill 15, so that the flue gas drawn from the primary cyclone 1 can be used as a drying heat source and transported to the raw material mill 14 and the fuel mill 15 to heat the materials and fuel respectively.

[0064] In this embodiment, the fuel provided by the fuel mill 15 is pulverized coal. Of course, other fuels besides pulverized coal can also be selected, as long as the overall structure and process flow are not affected.

[0065] In this embodiment, the separating cyclone 8 is connected to the lower hot carbon reduction zone 62 and the upper combustion decomposition zone 63 of the decomposition furnace 6 via connecting pipes. Each connecting pipe is equipped with a gate valve 6-1. By controlling the gate valve 6-1, the amount of combustion air delivered from the separating cyclone 8 to the decomposition furnace 6 can be controlled so that the proportion of combustion air in the decomposition furnace 6 can meet the proportion of the upper combustion decomposition zone 63 and the lower hot carbon reduction zone 62.

[0066] Furthermore, the separating cyclone 8 can separate the hot air after heat exchange. The combustion air used in the decomposition furnace 6 does not come from cold air in the atmosphere. After being separated by the five-stage cyclone 5, the heat of the high-temperature lime entering the cooling furnace is cooled by the fluidized bed suspension cooling furnace 7. Almost all the heat is carried away by the air entering the separating cyclone 8. This not only heats the air needed for coal combustion in the calcining furnace, thus saving coal, but also rapidly cools the high-temperature lime brought by the five-stage cyclone 5, making it easier to store, transport and use.

[0067] In this embodiment, the primary cyclone 1 consists of two cyclone ducts arranged side by side, and each cyclone duct is equipped with a flap valve between itself and the tertiary cyclone 3, namely the first flap valve 1-1 and the second flap valve 1-2; the secondary cyclone 2 is equipped with a third flap valve 2-1 between itself and the four-stage cyclone duct; the tertiary cyclone 3 is equipped with a fourth flap valve 3-1 between itself and the quinary cyclone 5; the quinary cyclone 4 and the decomposition furnace 6 are connected by a material distribution valve 4-2, which divides the material into two paths to enter the decomposition furnace 6; the quinary cyclone 4 and the material distribution valve 4-2 are equipped with a fifth flap valve 4-1; the material distribution valve 4-2 and the decomposition furnace 6 are equipped with a sixth flap valve 4-3 and a seventh flap valve 4-4, respectively; and the quinary cyclone 5 and the fluidized bed suspension cooling furnace 7 are equipped with an eighth flap valve 5-1.

[0068] In this embodiment, the separating cyclone 8 is connected to the finished product conveyor 11. After the finished product material comes out of the separating cyclone 8, it is transported to the finished product warehouse 12 by the finished product conveyor 11. A ninth flap valve 8-1 is provided between the two separating cyclones 8 and the finished product conveyor 11.

[0069] Other embodiments of this application will readily conceive of by those skilled in the art upon consideration of the specification and practice of the embodiments thereof. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not claimed in this application. The specification and embodiments are to be considered exemplary only, and the true scope and spirit of this application are indicated by the appended claims.

Claims

1. A low-NOx combustion decomposition furnace, characterized in that, include: A decomposition furnace body used for calcining and decomposing limestone. The decomposition furnace body is provided with a first material inlet, a second material inlet, a first combustion-supporting gas inlet, a second combustion-supporting gas inlet, a first fuel inlet, and a second fuel inlet. The first combustion-supporting gas inlet is located at the bottom of the decomposition furnace body. The first material inlet and the first fuel inlet are located above the first combustion-supporting gas inlet. The second material inlet and the second fuel inlet are located between the first combustion-supporting gas inlet and the second combustion-supporting gas inlet, and are located above the first material inlet and the first fuel inlet.

2. The low-NOx combustion decomposition furnace according to claim 1, characterized in that, The second combustion-supporting gas inlet is located at the upper part of the decomposition furnace body, and the first fuel inlet, the second fuel inlet, and the first material inlet are all located between the first combustion-supporting gas inlet and the second combustion-supporting gas inlet.

3. The low-NOx combustion decomposition furnace according to claim 2, characterized in that, The first fuel inlet, the first material inlet, the second fuel inlet, and the second material inlet are arranged sequentially from bottom to top on the decomposition furnace body.

4. The low-NOx combustion decomposition furnace according to claim 3, characterized in that, The decomposition furnace body is provided with a first narrowing structure at the bottom. The position of the first combustion-supporting gas inlet is lower than the position of the first narrowing structure. The position of the first fuel inlet corresponds to the position of the first narrowing structure. The position of the first material inlet is higher than the position of the first narrowing structure.

5. The low-NOx combustion decomposition furnace according to claim 4, characterized in that, The decomposition furnace body is also provided with a second narrowing structure, located above the second material inlet; The second fuel inlet is positioned corresponding to the second constriction structure; The positions of the second material inlet and the second combustion-supporting gas inlet are both higher than the position of the second constriction structure, and the position of the second combustion-supporting gas inlet is higher than the position of the second material inlet; A preheating decomposition zone is formed between the first constriction structure and the second constriction structure, and a hot carbon reduction zone and a combustion decomposition zone are formed sequentially above the second constriction structure.

6. The low-NOx combustion decomposition furnace according to claim 1, characterized in that, The proportion of material entering the decomposition furnace body through the first material inlet and the second material inlet is 50%-90% in the upper layer and 10%-50% in the lower layer; The proportion of combustion air entering the upper layer of the decomposition furnace body through the first combustion gas inlet and the second combustion gas inlet is 50%-90%, and the proportion in the lower layer is 10%-50%. The proportion of fuel entering the upper layer of the decomposition furnace body through the first fuel inlet and the second fuel inlet is 50%-90%, and the proportion of fuel entering the lower layer is 10%-50%.

7. The low-NOx combustion decomposition furnace according to claim 5, characterized in that, The combustion temperature in the combustion decomposition zone is controlled at 900℃-1000℃.

8. A lime calcination system, characterized in that, The low-NOx combustion decomposition furnace includes any one of claims 1-7.

9. The lime calcination system according to claim 8, characterized in that, It also includes a preheating unit, which is used to preheat the material, and the outlet of the preheating unit is divided into two paths that are connected to the decomposition furnace body.

10. The lime calcination system according to claim 8, characterized in that, It also includes a cooling unit, which includes a suspension cooling furnace and a separation cyclone. The suspension cooling furnace is connected to the outlet of the decomposition furnace and is used to receive the calcined material. The separation cyclone is connected to the outlet of the suspension cooling furnace and is used to perform gas-solid separation on the cooled material. The separated gas is used as a combustion-supporting gas and is divided into two paths to enter the decomposition furnace.

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