A continuous kiln and heat treatment method

Abstract

A continuous kiln and heat treatment method are disclosed, belonging to the field of lithium-ion battery material processing. The continuous kiln comprises a kiln, an airflow supply and exhaust device, and an airflow control device. The airflow supply and exhaust device and the airflow control device cooperate to control the atmosphere within the kiln cavity. The opposing air supply and exhaust nozzles in the airflow supply and exhaust device create a transverse airflow perpendicular to the length of the kiln, thereby maintaining a stable atmosphere within the kiln.

Description

Technical Field

[0001] The present application relates to the field of lithium-ion battery material processing, and in particular to a continuous kiln and a heat treatment or thermochemical treatment method. Background Art

[0002] Continuous kilns are one of the key equipment for producing positive electrode materials for lithium-ion batteries. They are primarily constructed of refractory materials, insulation materials, and building materials, and are tunnel-shaped kilns with openings at both ends.

[0003] During the production of lithium-ion battery cathode materials, specific gases (such as dry air, oxygen, or nitrogen) are typically introduced into a continuous kiln to create the required atmosphere for thermal or thermochemical treatment of the cathode materials. These gases are referred to as process gases. Furthermore, during the thermal or thermochemical treatment of the cathode materials within the kiln, gaseous byproducts (waste gases) are released during the reaction, such as water vapor and carbon dioxide, often containing residual corrosive substances or gases. These waste gases must be expelled from the kiln as quickly as possible, otherwise they will severely affect the atmosphere control within the kiln and deteriorate the performance of the calcined cathode materials. Summary of the Invention

[0004] In order to improve the existing problem of atmosphere control in a kiln, the present application proposes a continuous kiln and a heat treatment or thermochemical treatment method.

[0005] This application is implemented as follows:

[0006] In a first aspect, an example of the present application provides a continuous kiln, which includes a kiln furnace, an airflow supply and exhaust device, and an airflow control device.

[0007] The kiln has a furnace cavity extending in a first direction from the furnace head to the furnace tail. An airflow supply and exhaust device is used to form a directional airflow within the furnace cavity that can flow in a second direction from one furnace wall to the other furnace wall of the kiln. Furthermore, the airflow supply and exhaust device includes a supply and exhaust group, which includes an air supply nozzle and an air exhaust nozzle connected to the furnace wall and arranged in a matching and opposed manner. The air supply nozzle and the air exhaust nozzle are arranged in a third direction from the furnace top to the furnace bottom of the kiln. An airflow control device is connected to the airflow supply and exhaust device to control the air supply nozzle and the air exhaust nozzle.

[0008] In conjunction with the airflow control device, the airflow supply and exhaust device, through the cooperation of the air supply nozzle and the air exhaust nozzle, forms a directional airflow within the furnace chamber, thereby continuously maintaining the required process atmosphere within the furnace chamber, for example, ensuring that the gas concentration or pressure of the calcining atmosphere reaches the required level. Furthermore, the continuous supply of process gas through the air supply nozzle can refresh the atmosphere within the continuous kiln and exhaust waste gases. At the same time, heat loss can be controlled by controlling factors such as gas flow rate.

[0009] In some examples of the present application, a gas distributor is provided on the furnace wall at a location where the gas supply nozzle is connected, and the gas supply nozzle is in communication with an air cavity of the gas distributor.

[0010] The gas distributor can achieve the effect of simplifying the gas delivery structure and at the same time reduce the control difficulty of the airflow control device.

[0011] In some examples of the present application, the furnace wall has an air suction port at a location connected to the air suction nozzle, the air suction port is arranged along a third direction, and the air suction nozzle is in communication with the air suction port.

[0012] Optionally, the air inlet is long and narrow.

[0013] The narrow air inlet can provide a larger gas extraction area, corresponding to more air supply nozzles, thereby further improving the uniformity of air extraction and exhaust at various positions.

[0014] In some examples of the present application, the continuous kiln includes a sagger for containing materials, the sidewall of the sagger has notches, the notches form channels for directional airflow passing through the sagger, and the notches face the air intake port and the air delivery nozzle respectively.

[0015] Optionally, the mouth of the air delivery nozzle is close to the notch.

[0016] The gaps in the sagger are helpful for the flow of air, making it easier for the air to carry away the exhaust gas and reducing the turbulent flow of the air.

[0017] In some examples of the present application, the continuous kiln includes a detection device, which includes a furnace pressure sensor and / or a gas concentration sensor for detecting the kiln.

[0018] Optionally, the detection device includes a pressure sensor and / or a flow sensor, and one or both of the air suction nozzle and the air delivery nozzle are matched with a pressure sensor and / or a flow sensor.

[0019] Furnace pressure sensors and gas concentration sensors can reflect the atmosphere concentration and pressure within the furnace cavity, making it easier for users to detect the atmosphere inside the furnace cavity. Pressure sensors and flow sensors can reflect the working conditions of the air supply and exhaust nozzles, as well as the airflow entering and exiting the furnace cavity, making the control of the furnace cavity atmosphere more effective and efficient.

[0020] In some examples of the present application, the air flow control device includes an air supply valve and an exhaust valve, the air supply valve is matched and connected to the air supply nozzle, the exhaust valve is connected to the air suction nozzle, and the air supply valve and the exhaust valve are configured to be controlled in response to the detection device.

[0021] In some examples of the present application, the airflow control device is configured to be able to control the air supply nozzle and the air exhaust nozzle in a coordinated manner, thereby being able to control the air intake and exhaust volumes in the kiln in a coordinated manner, making the strength of the directional airflow in the kiln more stable.

[0022] In some examples of the present application, all the exhaust nozzles in the multiple supply and exhaust groups are located on one side of the furnace wall, and all the exhaust nozzles in the multiple supply and exhaust groups are located on the other side of the furnace wall;

[0023] Alternatively, both one side furnace wall and the other side furnace wall are provided with exhaust nozzles and air supply nozzles, and in the third direction, the exhaust nozzles and air supply nozzles on the furnace wall on the same side are alternately arranged;

[0024] Alternatively, there are multiple air flow supply and exhaust devices and they are arranged along the first direction, the air supply nozzle of the same air flow supply and exhaust device is located on one of the furnace walls, and the air exhaust nozzle is located on another furnace wall, and in the first direction, the air exhaust nozzles and air supply nozzles in two adjacent air flow supply and exhaust devices are arranged alternately.

[0025] Different structural modes of the airflow supply and exhaust device can meet different modes of continuous kiln, and can also achieve different degrees of renewal and temperature regulation effects on the atmosphere in the furnace cavity.

[0026] In some examples of the present application, the continuous kiln includes a heater connected to the kiln furnace.

[0027] In some examples of the present application, the heaters are arranged along the third direction and connected to the furnace wall of the kiln. Optionally, the heaters are arranged along the third direction, and an air supply nozzle or an air exhaust nozzle is provided between two adjacent heaters.

[0028] In a second aspect, an example of the present application provides a method for performing a heat treatment or thermochemical treatment using the above-mentioned continuous kiln. The heat treatment or thermochemical treatment method includes: providing a heat treatment or thermochemical treatment temperature within a furnace chamber of the kiln; transporting an object to be heat treated or thermochemically treated within the furnace chamber via a loading tool along a first direction, and during the transport process, supplying a process gas into the furnace chamber via an airflow supply and exhaust device under the control of an airflow control device, and simultaneously exhausting the gas from the furnace chamber via the airflow control device to maintain a heat treatment or thermochemical treatment atmosphere within the furnace chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 A schematic diagram of the structure of a kiln body in a continuous kiln used as an example in this application;

[0031] Figure 2 A schematic structural diagram of a continuous kiln in an example of the present application is shown in a first perspective;

[0032] Figure 3 A schematic structural diagram of a continuous kiln in an example of the present application at a second viewing angle is shown;

[0033] Figure 4 A schematic diagram of the structure of a sagger used in a continuous kiln in an example is shown;

[0034] Figure 5 A schematic structural diagram of an air delivery nozzle with a cutout in an example is shown.

[0035] Icons: 101-kiln; 1011-furnace head; 1012-furnace tail; 1013-furnace chamber; 1014-furnace wall; 1015-furnace top; 1016-furnace bottom; 11-heater; 32-air supply nozzle; 202-injection device; 203-exhaust device; 31-gas distributor; 2-sagger; 38-gap; 39-air inlet; 40-exhaust valve; 42-air supply valve; 18-process gas; 37-exhaust nozzle; 44-waste gas. DETAILED DESCRIPTION

[0036] As one of the core materials of lithium-ion batteries, positive electrode active materials (hereinafter referred to as positive electrode materials) play a vital role in the safety, comprehensive performance and cost of batteries.

[0037] During the production process, the heat treatment or thermochemical treatment of the positive electrode material, especially the high-temperature calcination step, is a core step in determining the material performance. Moreover, during the calcination process, many positive electrode materials require the introduction of specific process gases into the calcination kiln to maintain a special atmosphere, and the special atmosphere must be strictly controlled. For example, for ternary positive electrode materials, especially high-nickel ternary materials, oxygen needs to be introduced; for lithium iron phosphate, nitrogen atmosphere protection is required. For this type of positive electrode material that requires a special atmosphere during calcination, the atmosphere control during the calcination process is one of the most important conditions, which will affect the performance of the positive electrode material after calcination. Therefore, positive electrode material manufacturers and related researchers have been working hard to improve the atmosphere control capabilities of the kiln during the calcination of positive electrode materials.

[0038] Currently, cathode materials are typically calcined in continuous kilns. Examples include pusher-plate tunnel kilns (pusher-plate kilns) and roller-hearth tunnel kilns (roller-hearth kilns). A tunnel kiln is a tunnel structure with two open ends, constructed from refractory, insulation, and building materials. Depending on the temperature and function, tunnel kilns are typically divided into heating, holding, and cooling zones. The kiln body is heated by electric heaters or by injecting fuel (such as natural gas or heavy oil). Materials to be heat-treated or thermochemically treated, or material carriers (such as saggers), are loaded onto a vehicle and enter the tunnel kiln from one end (the kiln head), moving through the heating, holding, and cooling zones before exiting the kiln from the other end (the kiln tail), completing the heat treatment process.

[0039] However, through practice, the inventors of the present application found that existing kilns all have defects to varying degrees, resulting in the calcination of positive electrode materials failing to meet demand.

[0040] After analysis, the inventor believes that this is mainly due to:

[0041] During the calcination process, the cathode material reacts with the process gas. Only when the process gas is in full contact with the calcined material can the reaction proceed fully. Furthermore, a large amount of process gas flowing over the surface of the material can quickly remove the gaseous byproducts produced by the reaction, promoting the reaction. However, the intake and exhaust systems of existing continuous kilns for calcining cathode materials, such as pusher kilns or roller hearth kilns, fail to fully meet these two critical requirements.

[0042] For example, lithium-ion battery cathode materials are typically in powder form before calcination. These powders are typically placed in a carrier. To increase kiln capacity, these saggers are stacked on the carrier, severely impacting airflow.

[0043] Taking the existing typical technology of taking in air from the bottom and side walls of the kiln and exhausting it from the top of the kiln as an example, the process gas entering from the air inlet of the side wall of the kiln will flow upward under the attraction of the negative pressure of the exhaust port on the top of the kiln and be discharged from the exhaust port on the top of the kiln.

[0044] The process gas entering the bottom air inlet is blocked by the bottom of the lower sagger, and most of it can only flow along the periphery of the sagger and merge into the upward airflow; a small part passes through the gap between the saggers and enters the exhaust port upward.

[0045] Since there is no obstruction on the top of the sagger, the material in the upper sagger can have relatively sufficient contact with the process gas; at the same time, the exhaust gas released by the material in the upper sagger can also be discharged relatively smoothly from the top exhaust port along with the main air flow.

[0046] However, the lower sagger is blocked by the upper sagger, preventing process gas from entering smoothly, and the waste gas released by the materials cannot be carried away smoothly by the airflow. The gas exchange between the inside and outside of the lower sagger is mainly completed by diffusion: a small amount of process gas around the lower sagger enters the sagger through the gaps at the edge of the sagger through diffusion. Similarly, the waste gas released from the material in the lower sagger also escapes from the sagger through the gaps at the edge of the sagger through diffusion, and then converges with the airflow around the sagger to the kiln top and is discharged from the exhaust port.

[0047] Similarly, the method of taking in air from the top of the kiln and exhausting it from the bottom in the existing typical technology cannot solve the problem of the exhaust of the materials in the lower sagger being blocked and the insufficient contact with the fresh process gas.

[0048] In short, when the saggers are stacked, since the upper sagger blocks the lower sagger, whether the process gas enters the lower sagger or the exhaust gas escapes from the lower sagger, it mainly relies on diffusion.

[0049] Therefore, the gas exchange efficiency inside and outside the lower sagger is very low. Moreover, the diffusion directions of the two gases are opposite, which further weakens the gas exchange, making the concentration of process gas in the lower sagger much lower than that in the upper sagger, while the accumulation of exhaust gas in the lower sagger is much higher than that in the upper sagger.

[0050] This results in significant differences in the atmosphere exposed to the materials in the upper and lower saggers, which in turn leads to significant differences in the performance of the cathode materials in the upper and lower saggers after calcination, resulting in poor product consistency. To make matters worse, as pressure to reduce costs drives cathode material manufacturers to stack more saggers in the kiln, this problem becomes increasingly severe as the number of saggers stacked increases.

[0051] Furthermore, because the air pressure at the kiln's air inlet is low, the process gas's velocity decreases significantly after entering the larger space within the kiln. This hinders exhaust emissions and the uniform distribution of the process gas. Furthermore, excessively high air inlet pressure can cause excessive disturbance of the cathode material powder, causing it to fly and hindering proper transportation.

[0052] In response to the current situation, the inventors proposed to form an orderly and highly directional airflow in the kiln so that the positive electrode active material can fully contact with the process gas for reaction, while also being able to promptly discharge the waste gas generated by the reaction to suppress the adverse effects of the waste gas on the reaction.

[0053] To achieve the above effects, the inventors in this application propose a continuous kiln, which includes a kiln furnace 101, an airflow supply and exhaust device, and an airflow control device, which will be described in detail below.

[0054] Kiln 101

[0055] The structure of the kiln 101 in the example is shown in FIG. Figure 1 , which has a furnace wall 1014, a furnace bottom 1016 and a furnace top 1015. In particular, in order to facilitate the control of the process gas 18 therein and reduce the ineffective consumption of the process gas 18, the cross-section inside the furnace 101 can be designed to be tall and thin, and the internal dome / furnace top 1015 of the furnace 101 ( Figure 2 The free space (space without sagger 2) in the arc-shaped top area of ​​the furnace cavity is smaller than the area of ​​the furnace cavity in the furnace wall area).

[0056] The flow direction of the process gas 18 in the continuous kiln of the present application is as follows: Figure 2 and Figure 3 For the convenience of explanation and understanding, the kiln 101 is defined in three directions, namely the first direction, the second direction and the third direction. Specifically, the first direction is defined by the furnace head 1011 to the furnace tail 1012, as shown in FIG. Figure 1 The second direction is defined by the furnace wall 1014 on one side to the furnace wall 1014 on the other side, as shown in the middle direction B (or the length direction); Figure 1 As shown in the direction C (or width direction); the third direction is defined by the furnace top 1015 to the furnace bottom 1016, as shown in the figure. Figure 1 As shown in direction A (or height direction).

[0057] The kiln 101 constitutes the main structure of the continuous kiln. Operations such as heat treatment or thermochemical treatment are primarily performed within this kiln 101. As the location for heat treatment or thermochemical treatment, the kiln 101 comprises a furnace chamber 1013 bounded by furnace walls 1014. In actual use, materials undergoing heat or thermochemical treatment enter the kiln 101 through the furnace head 1011, sequentially undergoing the various sections of the furnace chamber 1013 (e.g., the heating, holding, and cooling sections), and finally exiting through the furnace tail 1012. It should be noted that as equipment for heat or thermochemical treatment, the kiln 101 typically requires a certain degree of airtightness and sealing. Therefore, the furnace head 1011 and furnace tail 1012 are typically equipped with selectively openable and closable gates, etc. The kiln 101 can also be constructed to be airtight via an outer shell. This is not illustrated in the examples of this application. Those skilled in the art will appreciate that the aforementioned equipment can be provided by conventional techniques. To avoid unnecessary elaboration, this application provides a brief description.

[0058] To perform heating operations, kiln 101 typically requires a heating device. As previously mentioned, this heating device can directly heat selected locations within kiln 101 by injecting fuel. However, to address the potential introduction of foreign matter and its impact on the calcination reaction, an electric heater 11, such as a heating rod, or a combustion heating method with a heat radiant tube is typically used. The heating rod can be a specific product such as a resistance heater 11.

[0059] In this example, the continuous kiln is provided with a heater 11, and the heater 11 is connected to the kiln 101 (eg Figure 3 In some examples, the heater 11 can be inserted into the furnace chamber 1013 from the furnace top 1015, or the heater 11 can be inserted into the furnace chamber 1013 through the furnace bottom 1016 or the furnace wall 1014. Considering that the heater 11 may hinder the material to be calcined being transported in the furnace chamber 1013, in the example of the present application, the heater 11 is plugged and fixed near the furnace wall 1014 and plugged in along the direction A from the furnace top 1015 to the furnace bottom 1016, see Figure 1 and Figure 3 .

[0060] exist Figure 3 In the disclosure, heaters 11 are installed on both sides of the furnace wall 1014 of the kiln 101. The number of heaters 11 on each side of the furnace wall 1014 is equal, and they are opposite each other in direction C. On the same side of the furnace wall 1014, adjacent heaters 11 are separated by an appropriate distance. Of course, other options for the installation location and method of the heaters 11 are also possible, and this application does not impose specific limitations on this.

[0061] In addition, according to different needs, various appropriate devices and equipment, such as detection devices, can be selectively configured for the kiln 101.

[0062] For example, in different usage modes, if it is necessary to provide other atmospheres into the furnace chamber 1013 of the kiln 101 , other gas supply pipeline equipment may be optionally provided.

[0063] For example, in order to monitor the temperature in the furnace chamber 1013 of the kiln 101 and adjust the temperature in a timely manner, a temperature detection device, such as a temperature sensor, specifically an infrared temperature detector, etc., may be provided in the kiln 101 .

[0064] Since calcination in the furnace chamber 1013 requires the supply of process gas 18, a gas monitoring device may be provided in the kiln 101. The gas monitoring device may be a pressure detector, a concentration detector, or both. The pressure detector may be a furnace pressure sensor for monitoring the kiln 101; the concentration detector may be a gas concentration sensor for monitoring the concentration of the process gas 18 (e.g., oxygen) in the kiln 101.

[0065] In addition, the continuous kiln can also be equipped with equipment for containing and transporting calcined materials (such as positive electrode materials), such as sagger 2, such as Figure 4 To facilitate airflow through the sagger 2, a notch 38 is provided on the side wall of the sagger 2. Therefore, when a plurality of saggers 2 are stacked, the notches 38 of different saggers 2 can form a channel for directional airflow to pass through the sagger 2.

[0066] Air supply and exhaust device

[0067] In this example, the airflow supply and exhaust device primarily comprises an airflow input portion and an airflow exhaust portion. These two portions cooperate to form a continuous and directional airflow within the kiln 101. The term "directional" here refers to a direction C that intersects (e.g., crosses) with the direction B of the kiln 101, i.e., from one side of the kiln 101 wall 1014 to the other side. In other words, during the longitudinal transport of the calcined material from the kiln head to the kiln tail within the furnace chamber 1013, the airflow supply and exhaust device can generate a transverse airflow.

[0068] The airflow input portion is used to deliver process gas 18 into the furnace chamber 1013 of the kiln 101 to meet the reaction needs during the calcination process. The airflow discharge portion is used to discharge the exhaust gas 44 in the furnace chamber 1013 of the kiln 101 to the outside of the kiln 101.

[0069] The airflow supply and exhaust device can be used to refresh the atmosphere within the furnace chamber 1013 of the kiln 101, for example, by adding fresh process gas 18 while simultaneously exhausting exhaust gas 44. Furthermore, by controlling the airflow's delivery characteristics, such as flow rate and volume, the temperature within the furnace chamber 1013 can be controlled to a certain extent. Because the exhaust gas 44 can carry away some heat, the temperature of the freshly input process gas 18 may also absorb some heat.

[0070] The air supply and exhaust device comprises an air supply and exhaust group. The air supply and exhaust group includes any number of air supply nozzles 32 and air extraction nozzles 37. The air supply nozzles 32 and air extraction nozzles 37 are spaced apart and opposite each other, and are both connected to the furnace wall 1014. Therefore, the space between the air supply nozzles 32 and air extraction nozzles 37 serves as a channel for conveying calcined materials in the furnace chamber 1013.

[0071] The air supply nozzles 32 and exhaust nozzles 37 in the supply and exhaust group are arranged along the third direction from the top 1015 to the bottom 1016 of the kiln 101. That is, the air supply nozzles 32 and exhaust nozzles 37 are arranged along the height of the kiln. Therefore, when a tall calcined object is placed in the furnace chamber 1013 of the kiln 101, the arrangement of the air supply nozzles 32 and exhaust nozzles 37 along the third direction effectively covers the calcined object, ensuring that it is evenly affected and influenced by the directional airflow. As an improved solution, the notch 38 of the sagger 2 for holding the calcined material faces the air supply nozzle 32. Furthermore, the mouth (gas outlet) of the air supply nozzle 32 is close to the notch 38 (to the extent that it does not hinder the normal transportation of the sagger), thereby facilitating the accurate delivery of gas to the sagger 2.

[0072] Figure 2 FIG3 is a schematic cross-sectional view of a continuous kiln, showing a supply and exhaust group comprising eight supply nozzles 32 and three exhaust nozzles 37. In other examples, the number of supply nozzles 32 and exhaust nozzles 37 in a supply and exhaust group may be equal, or the number of supply nozzles 32 may be less than the number of exhaust nozzles 37. In other words, the supply nozzles 32 and exhaust nozzles 37 may be arranged one-to-one, one-to-many, or many-to-one.

[0073] The above description is based on the example of a continuous kiln having only one airflow supply and exhaust device. When the continuous kiln in other examples has multiple airflow supply and exhaust devices, it has multiple supply and exhaust groups accordingly. Therefore, in the case of multiple supply and exhaust groups, all supply and exhaust groups can be arranged along the length direction of the kiln 101, for example Figure 3 shown.

[0074] above Figure 2 and Figure 3 Only one arrangement of the delivery and discharge groups in this application is disclosed. In other examples, the delivery and discharge groups may also have other arrangements, which will be described in detail below.

[0075] Case 1: In direction A of the kiln 101 , in one supply and exhaust group, all the air supply nozzles 32 are arranged on one furnace wall 1014 , and all the air exhaust nozzles 37 are arranged on the other furnace wall 1014 .

[0076] Case 2: In direction A of the kiln 101, in one supply and exhaust group, some of the air supply nozzles 32 are located on one furnace wall 1014, and the remaining air supply nozzles 32 are located on the other furnace wall 1014. Correspondingly, in this supply and exhaust group, some of the air extraction nozzles 37 are located on one furnace wall 1014, and the remaining air extraction nozzles 37 are located on the other furnace wall 1014.

[0077] For a continuous kiln having only one airflow supply and exhaust device and correspondingly one supply and exhaust group, the air supply nozzle 32 and the air exhaust nozzle 37 can be arbitrarily constructed in the manner of the above-mentioned case 1 or case 2.

[0078] For continuous kilns with multiple (e.g., two or more) air supply and exhaust devices, there are also multiple air supply and exhaust groups. All air supply and exhaust groups are arranged along direction B of the kiln 101. Furthermore, the air supply nozzles 32 and air exhaust nozzles 37 in each air supply and exhaust group can be arranged in either scenario 1 or scenario 2, or a combination of scenario 1 and scenario 2.

[0079] In the illustrated embodiment of the present application, there are multiple air supply and exhaust groups, and the air supply nozzles 32 and the air exhaust nozzles 37 are arranged in a combination of the above-mentioned case 1 and case 2. In particular, two adjacent air supply and exhaust groups on the same side of the furnace wall 1014 are arranged in an alternating manner with the air supply nozzles 32 and the air exhaust nozzles 37. In this way, when more than one row ( Figure 3 When the saggers 2 (shown in two rows) pass through the kiln, the saggers 2 on each side have an equal chance of facing the gas injection device 202 or the exhaust device 203, that is, the carrier and the like have an equal chance of facing the air supply nozzle 32 and the air extraction nozzle 37. This can improve the consistency of calcining the materials in the saggers 2 in different rows, so that each sagger 2 will have air flow passing through it alternately from both sides. In order to ensure better consistency, the saggers 2 in the example of this application are stacked in two rows, such as Figure 3 shown.

[0080] When considering the arrangement of the air supply nozzles 32 and air extraction nozzles 37, their position and structure can be adjusted specifically based on the heaters 11 in the furnace. For example, an air supply nozzle 32 or air extraction nozzle 37 can be placed between two adjacent heaters 11. Specifically, in the example of multiple air supply and exhaust groups, the air supply nozzles 32 and air extraction nozzles 37 of two adjacent air supply and exhaust groups are arranged alternately. Therefore, the heaters 11 can be placed between the air supply nozzles 32 and air extraction nozzles 37. Accordingly, the air supply nozzles 32 or air extraction nozzles 37 are alternately "sandwiched" between the two heaters 11. The alternating arrangement can be one heater 11, one air supply nozzle 32, one heater 11, one air supply nozzle 32, or two heaters 11, two air supply nozzles 32, or other arrangements. This prevents direct injection of process gas 18 onto adjacent heaters 11, impacting their heating power, while also ensuring sufficient preheating of the process gas 18.

[0081] The arrangement of the air supply and exhaust group is described above, and the specific structures of the air supply nozzle and the air exhaust nozzle will be described in detail below.

[0082] In this example, the air supply nozzle 32 is constructed as a cylindrical hollow tube. One end of the nozzle is inserted into the furnace wall 1014, and the other end extends into the furnace cavity 1013. The air supply nozzle 32 can be used as an airflow channel through a pipe buried in the furnace wall 1014 (this pipe can be hollow refractory bricks spliced ​​together, a ceramic tube, or a high-temperature resistant metal tube lined with ceramic), so that the process gas 18 can be delivered by the blower. In other examples, the air supply nozzle 32 can also be placed outside the kiln 101, and an injection tube connected to the air supply nozzle 32 can be inserted into the furnace through a hole in the furnace wall 1014; alternatively, the furnace cavity 1013 is not equipped with an injection tube inserted into the furnace, and gas is injected from the air supply nozzle 32 outside the furnace through the hole in the furnace wall 1014. Alternatively, the kiln can be stacked with hollow bricks, and then air holes connected to the hollow structure are opened in the hollow bricks, and gas is injected through the air holes.

[0083] When the number of air supply nozzles 32 is large, providing an independent pipeline for each air supply nozzle 32 may lead to complex processes and structures. Therefore, in the example, a cavity is reserved in the furnace wall 1014, which can be directly supplied with gas by a pipeline. The air supply nozzle 32 can also be directly connected to the cavity. Functionally speaking, the cavity essentially constitutes a gas distributor 31. A heating plate can also be provided in the gas distributor 31 to heat the process gas 18 entering therein to prevent the cold process gas 18 from directly entering the furnace chamber 1013. Of course, the process gas 18 can also be preheated outside the continuous kiln, and then passed into the gas distributor 31, and then sprayed into the furnace chamber 1013 through the air supply nozzle 32.

[0084] In addition, as an improved solution, the structure of the hollow tube-shaped air supply nozzle 32 can also be improved and matched with the gas distributor 31. For example, in some examples, a notch is set at one end of the air supply nozzle 32 extending into the gas distributor 31, thereby forming an "L" end structure. In addition, the incident direction of the process gas 18 entering the gas distributor 31 is away from the notch of the air supply nozzle 32 and is opposite to each other, such as Figure 5 As shown, the time for the process gas 18 in the gas distributor 31 to enter the nozzle can be delayed, so that the process gas 18 can obtain a longer heating time in the distributor, thereby improving the heating effect.

[0085] Similarly, the exhaust nozzle 37 can also be constructed as a hollow pipe. The exhaust nozzle 37 can also be provided with a trough structure in the furnace wall 1014, for the exhaust pipe to discharge the exhaust gas 44 from the furnace cavity 1013. In the example of the present application, the furnace wall 1014 is provided with an air intake 39 at the exhaust nozzle 37. Obviously, the exhaust nozzle 37 is connected to the air intake 39. And the air intake 39 is arranged along the third direction (i.e., the depth direction of the furnace cavity 1013). In some examples, the air intake 39 is long and narrow, for example, it can be a structure with a rectangular cross-section, or a structure with an elliptical cross-section. When the furnace wall 1014 is provided with an air intake 39, one end of the exhaust nozzle 37 can be inserted into the air intake 39, and the other end can extend out of the kiln 101.

[0086] In addition, as the power source for delivering gas through the air supply nozzle 32 and the air extraction nozzle 37, the air supply and exhaust device can also be equipped with a matching exhaust fan, blower, exhaust fan, air pump, etc. In the example of this application, the continuous kiln is equipped with an injection device 202 corresponding to the air supply nozzle 32; and an exhaust device 203 corresponding to the air extraction nozzle 37.

[0087] Airflow control device

[0088] The airflow control device is a device that works in conjunction with the airflow supply and exhaust device. It controls the air supply nozzle 32 and the air extraction nozzle 37, ensuring that they operate in a coordinated manner. Specifically, the operating state of the air supply nozzle 32 is linked to the operating state of the air extraction nozzle 37. Adjusting the operating state of the air supply nozzle 32 adjusts the state of the air extraction nozzle 37 accordingly. In principle, the airflow control device adjusts the air intake volume of the air supply nozzle 32 to match the exhaust volume of the air extraction nozzle 37, for example, ensuring that the intake volume equals the exhaust volume.

[0089] In other words, under certain operating conditions, the airflow control device can control the air supply nozzle 32 and the air extraction nozzle 37 in a coordinated manner. Of course, in other examples, the airflow control device can also independently control the air supply nozzle and the air extraction nozzle. For example, when a certain automatic control in the linkage mechanism fails or the automatic control adjustment range cannot meet actual needs, or when manual operation is required in certain special circumstances, the system can be switched to manual mode through a program. Relying on the values ​​of field instruments (flow meter, differential pressure gauge, and pressure transmitter), the system can manually adjust the air intake control valve and the exhaust control valve to achieve gas balance in the furnace. Whether the gas is balanced is determined by the display of the oxygen partial pressure value.

[0090] By controlling the intake and exhaust volumes to match them, the strength of the directional airflow can be made more stable. Furthermore, this prevents excessive flue gas from being generated due to a relatively large exhaust volume, which would remove a large amount of heat from the kiln 101 and cause unnecessary energy loss. It also prevents excessive residual exhaust gas 44 from being generated due to a relatively small exhaust volume, which would cause excessive residual exhaust gas 44 in the kiln 101.

[0091] As an example, the air flow control device includes an air supply valve 42 (which may be an automatically controlled valve, which may have a manual adjustment handle) and an air exhaust valve 40 (which may be an automatically controlled corrosion-resistant high-temperature valve, which may have a manual adjustment handle).

[0092] The air supply valve 42 is connected to the air supply nozzle 32, and the exhaust valve 40 is connected to the air extraction nozzle 37. Adjusting the opening of these two valves allows control of the delivery of process gas 18 and exhaust gas 44. Valves can be various butterfly valves, ball valves, regulating valves, throttle valves, and so on. To improve control accuracy and facilitate operation, proportional solenoid valves can be used for the exhaust valve 40 and the air supply valve 42.

[0093] Furthermore, the continuous kiln may be provided with a detection device, so that the air supply valve 42 and the exhaust valve 40 are configured to be controlled in response to the detection device. In other words, the air supply valve 42 and the exhaust valve 40 are adjusted accordingly based on the operating conditions of the continuous kiln detected by the detection device, thereby achieving the operation of the air supply nozzle 32 and the exhaust nozzle.

[0094] The detection device may include a pressure sensor and a flow sensor. The pressure sensor and flow sensor may be connected to the air supply piping system and located upstream of the air supply nozzle 32. Alternatively, the pressure sensor and flow sensor may be connected to the air extraction piping system and located downstream of the air extraction nozzle 37.

[0095] Furthermore, the furnace pressure sensor and the gas concentration sensor for the process gas 18 provided in the kiln 101 can also serve as components of the detection device. Thus, the detection device can accurately reflect the various states of the injected and exhausted gases, as well as the gas within the furnace chamber 1013 of the kiln 101, thereby enabling more accurate operation of the airflow control device.

[0096] To improve control automation, a controller can be used to control the air supply valve 42 and the exhaust valve 40. The detection device and the controller are then connected to coordinate the collection and processing of detection information and the transmission of control information. The controller can be any electronic component or combination thereof capable of storing and processing certain data. Examples include a central processing unit (CPU), a microcontroller unit (MCU), a programmable logic controller (PLC), a programmable automation controller (PAC), an industrial control computer (IPC), a field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), and the like. Through this structural design, the continuous kiln can achieve closed-loop operation of gas injection and exhaust.

[0097] The working principle of the controller can be:

[0098] The furnace pressure sensor and gas concentration sensor collect partial pressure data of the process gas 18 in the furnace chamber 1013. The controller determines the gas exchange efficiency within the furnace and then sets a target intake flow rate for the air supply valve 42 of the air supply nozzle 32 to adjust the actual intake flow rate. Simultaneously, the controller uses the flow rate data of the air supply valve 42 as a parameter to calculate the target opening of the exhaust system's exhaust valve 40, which is used to adjust the exhaust system's exhaust volume, achieving coordinated control of the exhaust and intake volumes.

[0099] When the partial pressure of process gas 18 falls below a certain percentage of the set value, the air supply valve 42 opens wider, and the exhaust control valve opens wider. When the partial pressure of process gas 18 rises above a certain percentage of the set value, the air intake flow control valve closes, and the exhaust control valve opens narrower. When the partial pressure of process gas 18 remains within a certain percentage of the set value, the air intake flow control valve and the exhaust control valve remain unchanged. Furthermore, to ensure smooth operation of this feedback system and prevent excessive or slow movements, the furnace pressure within the furnace chamber 1013 of the kiln 101 serves as an intermediate equilibrium constant, ensuring that any adjustments maintain the furnace pressure within a set fluctuation range.

[0100] In summary, the continuous kiln proposed in this application can achieve better use effects, making the concentration of the process gas 18 in the kiln evenly distributed, so that the calcined material can be in uniform and consistent contact with the process gas 18, thereby improving the consistency of the performance of the calcined product.

[0101] As an application example, the present application also proposes a method of heat treatment or thermochemical treatment, which includes:

[0102] Step 1: Provide a temperature for thermal treatment or thermochemical treatment in the furnace chamber 1013 of the kiln 101 .

[0103] The temperature of the heat treatment or thermochemical treatment can be provided by heaters 11 installed in the kiln 101 of the continuous kiln. The number and position of heaters 11 in operation can be adaptively adjusted for different temperature sections of the kiln 101 (heating section, heating section, cooling section, etc.).

[0104] Step 2: The object to be heat-treated or thermochemically treated is transported in the furnace chamber 1013 along a first direction through a loading tool. During the transportation process, process gas is input into the furnace chamber 1013 through the airflow supply and exhaust device under the control of the airflow control device, and gas is synchronously exhausted from the furnace chamber 1013 through the airflow control device to maintain the required process atmosphere in the furnace chamber 1013.

[0105] The loading vehicle, for example, is a sagger 2, which is transported via a conveyor such as a roller conveyor, a push plate, or a kiln car. To increase production while also maximizing the utilization of process gas 18, the saggers 2 on the conveyor are arranged in two rows, each with eight layers. The kiln car transports the saggers 2 from the kiln head through the heating zone, the holding zone, and the cooling zone. During this process, process gas 18 is continuously injected and exhaust gas 44 is continuously discharged until the saggers 2 are discharged from the kiln tail, completing the calcination process.

[0106] By using the continuous kiln proposed in this application, for heat treatment or thermochemical treatment operations in which a higher number of saggers 2 are stacked, the saggers 2 in the lower layer can be exposed to an increased concentration of the process gas 18, and the accumulation of the exhaust gas 44 in the lower sagger 2 is reduced, thereby improving the consistency of the atmosphere in the upper and lower saggers 2 and the consistency of the performance of the product after calcination. In addition, by selectively controlling the intake and exhaust volumes, the strength of the directional airflow is stabilized; by staggering the gas injection device 202 and the exhaust device 203 on each side of the kiln wall, it is ensured that when multiple rows of saggers 2 are stacked, the outermost saggers 2 can face the gas injection device 202 and the exhaust device 203 with equal probability, which also improves the consistency of the atmosphere in the saggers 2 on both sides.

[0107] It should be noted that although the continuous kiln is used to produce positive electrode materials for lithium-ion batteries by calcining in the examples of this application, this does not mean that this application is intended to limit its use to this purpose. In other examples, the continuous kiln can also be used to sinter ceramic materials or other alloy materials.

[0108] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A continuous kiln, characterized in that: include: The kiln has a furnace cavity extending in a first direction from a furnace head to a furnace tail; an air supply and exhaust device for forming a directional airflow in the furnace cavity that can flow in a second direction from one side wall of the kiln to the other side wall of the kiln, the air supply and exhaust device comprising a supply and exhaust group, the supply and exhaust group comprising an air supply nozzle and an air exhaust nozzle connected to the furnace wall and matched with each other and opposite to each other, the air supply nozzle and the air exhaust nozzle being arranged along a third direction from the top to the bottom of the kiln; An airflow control device, connected to the airflow supply and exhaust device, so as to control the air supply nozzle and the air extraction nozzle; All the exhaust nozzles in the supply and exhaust group are located on the furnace wall on one side, and all the air supply nozzles in the supply and exhaust group are located on the furnace wall on the other side; Alternatively, the exhaust nozzles and the air supply nozzles are both provided on the furnace wall on one side and the furnace wall on the other side, and in the third direction, the exhaust nozzles and the air supply nozzles on the furnace wall on the same side are alternately arranged at intervals; Alternatively, there are multiple airflow supply and exhaust devices and they are arranged along the first direction, the air supply nozzle of the same airflow supply and exhaust device is located on one of the furnace walls, and the air exhaust nozzle is located on another furnace wall, and in the first direction, the air exhaust nozzles and air supply nozzles in two adjacent airflow supply and exhaust devices are arranged alternately.

2. The continuous kiln according to claim 1, characterized in that The furnace wall is provided with a gas distributor at a location connected to the gas supply nozzle, and the gas supply nozzle is communicated with the air cavity of the gas distributor.

3. The continuous kiln according to claim 1 or 2, characterized in that The furnace wall has an air intake port at a location connected to the air extraction nozzle. The air intake port is arranged along the third direction, and the air extraction nozzle is in communication with the air intake port.

4. The continuous kiln according to claim 3, characterized in that The air inlet is in a long and narrow shape.

5. The continuous kiln according to claim 3, characterized in that The continuous kiln comprises a sagger for containing materials. The side wall of the sagger is provided with a notch, which forms a channel for the directional airflow to pass through the sagger. The notches face the air intake port and the air delivery nozzle respectively.

6. The continuous kiln according to claim 5, characterized in that The mouth of the air supply nozzle is close to the notch.

7. The continuous kiln according to claim 1, characterized in that The continuous kiln includes a detection device, which includes a furnace pressure sensor and / or a gas concentration sensor for detecting the kiln.

8. The continuous kiln according to claim 7, characterized in that The detection device includes a pressure sensor and / or a flow sensor, and one or both of the air suction nozzle and the air delivery nozzle are matched with the pressure sensor and / or flow sensor.

9. The continuous kiln according to claim 7, characterized in that The air flow control device includes an air supply valve and an exhaust valve, the air supply valve is matched and connected to the air supply nozzle, the exhaust valve is connected to the air suction nozzle, and the air supply valve and the exhaust valve are configured to be controlled in response to the detection device.

10. The continuous kiln according to claim 9, characterized in that The air flow control device is configured to be able to control the air supply nozzle and the air exhaust nozzle in a linked manner, thereby controlling the air intake and exhaust volumes in the kiln in a linked manner.

11. The continuous kiln according to claim 1, characterized in that The continuous kiln includes a heater connected to the kiln furnace.

12. The continuous kiln according to claim 11, characterized in that The heater is arranged along the third direction and connected to a furnace wall of the kiln.

13. The continuous kiln according to claim 12, characterized in that The heaters are arranged along the third direction, and an air supply nozzle or an air exhaust nozzle is provided between two adjacent heaters.

14. A heat treatment method implemented by the continuous kiln according to any one of claims 1 to 13, characterized in that: The heat treatment method comprises: Providing a temperature required for heat treatment in the furnace chamber of the kiln; The object to be heat-treated or thermochemically treated is transported in the furnace chamber along the first direction through a loading tool, and during the transportation process, gas is input into the furnace chamber through the airflow supply and exhaust device under the control of the airflow control device, and gas is synchronously exhausted from the furnace chamber through the airflow control device to maintain the process atmosphere of the heat treatment in the furnace chamber.

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