A multi-layer fluidized bed and a downer device between bed layers of the multi-layer fluidized bed

Abstract

The present application belongs to the technical field of fluidized bed ironmaking, and discloses a multi-layer fluidized bed and a down feeder between the bed layers of the multi-layer fluidized bed. A gas cylinder is arranged directly below the outlet of the down feeder pipe, and a material control plug is arranged on the top of the gas cylinder. The piston is driven to move downward by the external gas driving part, and the piston is driven to move upward by the reset driving part after the gas driving part is depressurized, so as to drive the material control plug to move up and down, and the opening of the down feeder pipe can be accurately adjusted to continuously adjust the down feeder amount. In the present application, a gas slit is arranged between the piston rod and the gas cylinder, the external material is prevented from entering the compression cavity by the gas seal mode, the normal work of the gas cylinder is affected, and the gas is blown out from the gas slit to have the function of cooling the gas cylinder and other components, thereby prolonging the service life of the down feeder, and effectively ensuring the long-term operation of the gas cylinder and other components in the iron ore powder direct reduction environment.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, specifically relating to a feeding device between layers of a multi-layer fluidized bed and a multi-layer fluidized bed. Background Technology

[0002] Fluidized bed direct reduction (FDR) ironmaking technology is a highly efficient metallurgical method that involves contacting iron ore powder with reducing gases in a fluidized bed to reduce iron oxides into metallic iron. Compared to traditional blast furnace ironmaking processes, FDR offers advantages such as strong raw material adaptability, low energy consumption, and environmental friendliness, making it particularly suitable for the direct utilization of fine iron ore resources. In recent years, numerous domestic and international institutions have conducted systematic research in this field, proposing various fluidized bed reduction systems and methods. For example, a two-stage reduction process combining bubbling and circulating fluidized beds, using gas series operation to improve reduction efficiency, achieves highly efficient reduction of powdered iron ore.

[0003] Bubbling fluidized beds offer advantages such as thorough gas-solid contact, uniform temperature distribution, and stable operation. To expand production capacity and improve gas utilization efficiency, some organizations have adopted multi-stage bubbling fluidized bed technology. However, compared to multi-stage structures, multi-layer bubbling fluidized beds (referred to as multi-layer fluidized beds) have even greater advantages. They require less floor space, have lower construction costs, and higher heat utilization efficiency. Furthermore, multi-layer fluidized beds allow materials to pass sequentially between multiple bed layers, completing different processes such as drying, preheating, and multi-stage reduction. In a multi-layer fluidized bed structure, the feeding device between the bed layers becomes a key component affecting the stable operation of the entire system. Its performance directly relates to the smoothness of material flow, the maintenance of bed pressure differential, and the prevention of gas leakage.

[0004] Several technical solutions have been proposed to address the interlayer feeding problem in multi-layer fluidized beds. For example, the pneumatically controlled circumferential cone valve fluidized bed feeding leg adopts a structure with a central tube surrounding a 360° short cone tube, achieving material circulation and conveying through pneumatic control. It features simple structure, good axisymmetry, and strong self-balancing ability. Another study proposed a pneumatically controlled overflow pipe technology, which, under fluidized bed conditions, achieves feeding control without jamming, spraying, or gas leakage, and has a large discharge range. However, the above technical solutions mainly focus on feeding control of general powder materials. For the specific application scenario of direct reduction of iron ore powder, several problems remain to be solved: iron ore powder is prone to agglomeration and loss of flow under high-temperature reduction conditions; conventional feeding devices are prone to jamming and failure due to ore powder entering moving parts; in case of blockage, the feeding device lacks self-cleaning capability; the large interlayer pressure difference in multi-layer beds places high demands on the sealing performance of the feeding device; and the reducing atmosphere places higher demands on equipment reliability and service life.

[0005] Therefore, developing a dedicated feeding device suitable for multi-layer fluidized bed direct reduction ironmaking process is of great significance for promoting the industrial application of multi-layer fluidized bed direct reduction ironmaking technology. This device can effectively prevent ore powder from entering the drive components, accurately control the feeding amount and speed between layers, and also have good sealing performance and long-term operational stability. Summary of the Invention

[0006] The purpose of this invention is to provide a feeding device between layers of a multi-layer fluidized bed and a multi-layer fluidized bed. By placing a cylinder directly below the outlet of the feeding pipe and a control plug at the top of the cylinder, an external gas drive unit drives the piston downwards. A reset drive unit, after depressurization of the gas drive unit, drives the piston upwards, thereby raising and lowering the control plug. This allows for precise adjustment of the feeding pipe opening and continuous regulation of the feeding amount. In this invention, an air gap is provided between the piston rod and the cylinder, using an air seal to prevent external materials from entering the compression chamber and affecting the normal operation of the cylinder. Furthermore, the gas blown out through the air gap serves to cool the cylinder and other components, thereby extending the service life of the feeding device and effectively ensuring the long-term operation of the cylinder and other components in the direct reduction environment of iron ore powder.

[0007] The technical problem to be solved by the present invention is achieved by the following technical solution: a feeding device between layers of a multi-layer fluidized bed, comprising a feeding pipe, a material control unit disposed below the feeding pipe, a gas driving unit and a reset driving unit; The feed pipe passes through the air distribution plate between two adjacent fluidized beds, and the lower end outlet of the feed pipe is set downward; The material control unit includes a material control plug, a cylinder, a piston, and a piston rod. The piston is slidably disposed inside the cylinder, and the piston rod is disposed above the piston. The cylinder is fixedly installed inside the fluidized bed and located below the outlet of the feed pipe. The material control plug is located at the top of the piston rod and is used to control the opening degree of the lower end outlet of the feed tube; The piston divides the cylinder into a compression chamber and a reset chamber, and an air gap is provided between the piston rod and the cylinder. The gas drive unit is connected to the compression chamber through the first delivery pipe, and is used to introduce compressed gas to drive the piston to move downward. The reset drive unit is used to apply a driving force to the piston after the gas drive unit is depressurized, so that the piston moves upward.

[0008] This invention utilizes a gas-driven unit and a reset-driven unit to control the up-and-down movement of a piston, thereby driving the material control plug to rise and fall. When the material control plug rises to contact the lower outlet of the discharge pipe, the discharge pipe is closed, stopping material feeding; when the material control plug descends and leaves the lower end of the discharge pipe, the discharge pipe opens, and the material falls by gravity. By controlling the stroke of the material control plug, the opening of the discharge pipe can be precisely adjusted, achieving continuous adjustment of the feeding amount.

[0009] The air gap has a dual function. On the one hand, the gas in the compression chamber will be continuously blown out from the air gap, which can prevent external materials from entering the compression chamber and affecting the normal operation of the cylinder. On the other hand, the gas is at room temperature, while the cylinder works in a high-temperature environment. The gas blown out from the air gap has the function of cooling the cylinder, piston rod and other components, thereby extending the service life of the feeding device.

[0010] Preferably, the reset driving part of the present invention is the elastic reset member, which is disposed in the cylinder, with one end connected to the lower end face of the piston and the other end connected to the bottom of the cylinder, and is used to drive the piston to reset upward when the gas driving part is depressurized; The reset chamber is equipped with an exhaust pipe connected to the outside of the fluidized bed; The first delivery pipeline is equipped with a servo pressure regulating valve and a servo venting valve; Preferably, the elastic reset element is a spring.

[0011] Its working principle is as follows: When the feed pipe needs to be opened, compressed air is injected into the compression chamber through the servo pressure regulating valve. The pressure in the upper air chamber increases, pushing the piston downward and compressing the elastic reset element in the reset chamber. At the same time, the air in the reset chamber is discharged through the connected exhaust pipe. When the feed pipe needs to be closed or the opening needs to be adjusted, the pressure in the compression chamber is released through the quick venting valve. The pressure in the reset chamber is equal to that of the atmosphere. The elastic reset element resets and pushes the piston upward, causing the material control plug to rise. Working scenario: When the material level in the upper bed fluctuates, the material level signal is fed back to the external control system. The control system regulates the servo pressure regulating valve and the servo venting valve to inject or release air into the compression chamber, precisely adjusting the pressure in the compression chamber and the compression amount of the elastic reset element. This precisely controls the position of the material control plug, adjusts the feed rate, and ultimately stabilizes the material level in the upper bed within a certain height.

[0012] The servo pressure regulating valve is used to precisely control the gas pressure entering the compression chamber, while the servo vent valve is used to quickly release the pressure in the compression chamber when the feed pipe needs to be closed. In case of abnormal conditions such as blockage in the feed pipe, the servo vent valve and servo pressure regulating valve can be quickly adjusted to release the pressure in the gas chamber, causing the spring to quickly return to its original position and push the piston upward. This causes the control plug to quickly impact the feed pipe, using the vibration effect to break up the bridging material in the feed pipe and promptly handle the abnormal conditions.

[0013] Preferably, the reset drive unit of the present invention includes a gas drive unit and an auxiliary elastic element. The gas drive unit is connected to the reset chamber through a second delivery pipe and is used to introduce compressed gas to drive the piston to move upward. The auxiliary elastic element is disposed inside the cylinder, with one end connected to the lower end face of the piston and the other end connected to the bottom of the cylinder, and is used to drive the piston to reset upward when the gas drive part is depressurized. Preferably, the auxiliary elastic element is a spring. The upward force of gas alone is insufficient to make the piston move upward normally; by simultaneously providing the auxiliary elastic element, an upward driving force is provided to the piston.

[0014] Preferably, the gas drive unit and the gas drive section adopt the same gas supply system, and the first delivery pipe and the second delivery pipe are connected to the gas supply system through a reversing valve.

[0015] Preferably, the cylinder is provided with a protective cover connected to the material control plug. The protective cover covers the upper part of the cylinder, and a gap is provided between the protective cover and the outer wall of the cylinder. The main function of the protective cover is to prevent mineral powder falling from the feed pipe or dust from the fluidized bed from entering the cylinder and hindering its normal operation. By isolating the cylinder from the material environment through the protective cover, mineral powder is effectively prevented from entering the moving parts, avoiding jamming failure, and significantly improving the long-term operational reliability of the device.

[0016] Preferably, the present invention further includes a position sensor and a control system, wherein the position sensor is disposed on the material control plug or piston; The control system is connected to the position sensor, the gas drive unit, and the reset drive unit respectively, and is used to control the gas drive unit and the reset drive unit according to the position signal of the position sensor. The fluidized bed is equipped with a material level measuring device. In adjacent fluidized bed layers, when the material level of the upper layer exceeds a preset height range, the material level measuring device collects the material level signal and feeds it back to the control system. The control system controls the position of the lower layer material control plug through the gas drive unit and the reset drive unit, adjusting the feed rate to stabilize the material level of the upper layer within the preset height range. A position sensor can detect the position of the material control plug or piston in real time and feed the signal back to the control system. Based on the material level signal of the upper layer, the control system controls the on / off and direction of the air path through a reversing valve, achieving closed-loop control of the feeding device. The reversing valve can be an electromagnetic reversing valve, facilitating integration with control systems such as PLCs.

[0017] Preferably, the material control plug of the present invention is a flat plate, a disc, or a cone with its tip pointing upwards; Preferably, the surface of the material control plug is provided with a wear-resistant layer. The flat plate structure is simple and suitable for general working conditions; the disc shape has a larger sealing contact surface and better sealing effect; the cone shape with the tip pointing upwards helps the material to be dispersed in all directions, avoiding the accumulation of material on the top of the plug, while the cone surface forms a line contact with the lower port of the feed pipe, resulting in excellent sealing performance and less likelihood of material jamming.

[0018] Preferably, the upper surface of the material control plug is provided with an annular retaining dam. Preferably, the annular retaining dam is a complete ring or an intermittent ring with gaps along the circumference; Preferably, the upper surface of the material control plug is provided with multiple coaxial annular baffles. The falling material forms a thin layer at the annular baffles, and the subsequent falling material rubs against the thin layer, achieving friction between materials, reducing the scouring of the material control plug and other parts by the falling mineral powder. The multiple coaxial annular baffles can effectively ensure the uniform distribution of furnace charge on the upper surface of the material control plug.

[0019] Preferably, the cylinder is fixedly mounted on the fluidized bed furnace shell via a bracket to ensure the stability and reliability of the device; or it can be directly connected to the feed pipe, simplifying the installation structure and making it suitable for space-constrained applications. Both installation methods can be flexibly selected based on the actual reactor structure and spatial layout. The material control unit can be installed on the furnace shell or the feed pipe, depending on the actual reactor structure and spatial layout, and can also be installed at multiple points as needed, offering strong adaptability. Compared with the prior art, the beneficial effects of the present invention are: 1. Simple structure and precise control: The cylinder structure directly drives the material control plug, with fewer transmission links and fast response speed; the gas drive and reset drive are controlled directly with the height of the upper bed material surface as the reference, so as to achieve precise adjustment of the feeding amount.

[0020] 2. Reliable sealing to prevent gas leakage: The material control plug is in direct contact with the lower end of the feed pipe for sealing, effectively preventing gas leakage between the upper and lower beds and maintaining stable bed pressure difference.

[0021] 3. Anti-blocking design, reliable and stable: The material control unit is in the form of a cylinder. If the feed pipe is blocked, the pressure in the compression chamber is released quickly, causing the material control blockage head to hit the feed pipe quickly, which can effectively solve the abnormal blockage of the feed pipe.

[0022] 4. Adaptable to high-temperature working conditions: The cylinder is filled with room temperature gas, which can cool the feeding device. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the feeding device between the layers of the multi-layer fluidized bed in Embodiment 1 of the present invention; Figure 2This is a schematic diagram of the feeding device between the multi-layer fluidized bed in Embodiment 2 of the present invention; Figure 3 This is a schematic diagram of the annular retaining dam in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the annular retaining dam in Embodiment 3 of the present invention; In the diagram, 1 is the feeding pipe, 2 is the material control unit, 21 is the material control plug, 22 is the cylinder, 23 is the piston, and 24 is the piston rod. 100 compression chamber, 200 reset chamber, 300 air gap; 101 First conveying pipe, 201 Second conveying pipe, 202 Exhaust pipe; 3. Elastic reset component, 4. Servo pressure regulating valve, 5. Servo venting valve, 6. Auxiliary elastic component, 7. Reversing valve, 8. Protective cover, 9. Position sensor, 10. Annular dam, 11. Support, 12. Fluidized bed furnace shell. Detailed Implementation

[0024] The present invention will be further explained and described below with reference to the accompanying drawings and specific embodiments. In the description of the present invention, it should be understood that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only a simplified description for ease of description, and should not be construed as a limitation of the present invention. Unless otherwise expressly specified and limited, the terms "connected," "linked," etc., can refer to a fixed connection, a detachable connection, or an integral connection.

[0025] Example 1 like Figure 1 As shown, a feeding device between layers of a multi-layer fluidized bed includes a feeding pipe 1, a material control unit 2 disposed below the feeding pipe 1, a gas drive unit, and a reset drive unit.

[0026] The feed pipe 1 passes through the air distribution plate (not shown in the figure) between two adjacent fluidized beds. The upper end of the feed pipe 1 opens into the space of the upper fluidized bed, so that the material of the upper bed can be transported to the lower bed through the feed pipe 1.

[0027] The material control unit 2 includes a material control plug 21, a cylinder 22, a piston 23, and a piston rod 24. The piston 23 is slidably disposed within the cylinder 22, and the piston rod 24 is disposed above the piston 23. A dynamic sealing structure is used to seal the piston 23 and the cylinder 22. The material control plug 21, the cylinder 22, the piston 23, and the piston rod 24 are all made of high-temperature resistant metal materials.

[0028] The piston rod 24 passes through the top housing of the cylinder 22, and the material control plug 21 is fixedly installed on the top of the piston rod 24, corresponding to the lower port of the feed pipe 1, and is used to control the opening of the lower outlet of the feed pipe 1. The material control plug 21 is coaxially arranged with the feed pipe 1.

[0029] The piston 23 divides the cylinder 22 into a compression chamber 100 and a reset chamber 200. An annular air gap 300 is provided between the piston rod 24 and the cylinder 22. This gap ensures that the piston rod 24 can move freely up and down, while also allowing the gas ejected from the compression chamber 100 to cool and purge the gap and piston rod 24, preventing material dust from falling into the upper compression chamber 100 and thus disrupting the normal operation of the cylinder 22. The piston is made of high-temperature resistant stainless steel or similar material; the piston and cylinder are sealed, and the compression chamber 100 contains cold air. The cold, high-pressure air source carries away heat, cooling the piston and cylinder.

[0030] The gas drive unit is connected to the compression chamber 100 via the first delivery pipe 101, and is used to introduce compressed gas to drive the piston 23 to move downward. The gas supply system of the gas drive unit is a gas supply pump located outside the fluidized bed, which directly uses air as the gas source.

[0031] The reset drive unit is used to apply a driving force to the piston 23 after the gas drive unit is depressurized, so that the piston 23 moves upward.

[0032] The reset drive unit is the elastic reset member 3, which is disposed inside the cylinder 22. One end of the elastic reset member is connected to the lower end face of the piston 23, and the other end is connected to the bottom of the cylinder 22. It is used to drive the piston 23 to reset upward when the gas drive unit is depressurized. The elastic reset member 3 is a spring made of high-temperature resistant metal material. The upper end of the spring 5 abuts against the piston 23, and the lower end abuts against the bottom of the cylinder 24. The reset chamber 200 is connected to the atmosphere through an exhaust pipe to ensure that the air in the reset chamber 200 can be smoothly discharged when the piston 24 moves downward.

[0033] The reset chamber 200 is provided with an exhaust pipe 202 that is connected to the outside of the fluidized bed.

[0034] The first conveying pipeline 101 is equipped with a servo pressure regulating valve 4 and a servo venting valve 5.

[0035] A protective cover 8 is provided on the outside of the cylinder 22 and connected to the material control plug 2. The protective cover 8 has an annular baffle structure and covers the upper part of the cylinder 22. A gap is provided between the protective cover 8 and the outer wall of the cylinder 22. The protective cover 8 moves up and down together with the material control plug 21. Its main function is to prevent mineral powder falling from the feed pipe 1 or dust in the fluidized bed from entering the cylinder 22 area, to prevent dust from entering the gap between the piston 23 and the cylinder wall and causing jamming, and to prevent dust from adhering to the surface of the piston rod 24 and being carried into the cylinder 22.

[0036] The feeding device between the layers of the multi-layer fluidized bed also includes a position sensor 9 and a control system. The position sensor 9 is mounted on the control plug 21 or the piston 23. In this embodiment, the position sensor 9 is mounted on the piston 23.

[0037] The control system is connected to position sensor 9, gas drive unit, and reset drive unit (not shown in the figure) respectively. It controls the gas drive unit and reset drive unit based on the position signal from position sensor 9, enabling closed-loop automatic control of the feeding device. Without a position sensor, the control system can determine the spring height based on the air pressure inside the cylinder; or it can adjust the cylinder and control the position of the plug by adjusting the height of the upper bed layer to regulate the feeding amount. The fluidized bed is equipped with a material level measuring device (not shown in the figure). In adjacent fluidized bed layers, when the material level of the upper bed layer exceeds the preset height range, the material level measuring device collects the material level signal and feeds it back to the control system. The control system then controls the position of the lower layer material control plug through the gas drive unit and reset drive unit, adjusting the feeding amount to stabilize the material level of the upper bed layer within the preset height range. The material level measuring device is a position sensor installed inside the fluidized bed to measure the material level.

[0038] The material control plug 21 is a flat plate, a disc, or a cone with its tip pointing upwards. In this embodiment, the material control plug 21 is a cone with its tip pointing upwards.

[0039] The surface of the material control plug 21 is provided with a wear-resistant layer, which is formed by spraying a high-temperature resistant wear-resistant material. The high-temperature resistant wear-resistant spraying material is commercially available.

[0040] A ring-shaped retaining dam 10 is provided on the upper surface of the material control plug 21.

[0041] like Figure 3 As shown, the annular retaining dam 10 is a complete annular plate structure. The annular retaining dam 10 is also made of high-temperature resistant metal material.

[0042] As needed, multiple coaxially arranged annular retaining walls 10 (not shown in the figure) can be provided on the upper surface of the material control plug 21.

[0043] The cylinder 22 is fixedly installed on the fluidized bed furnace shell 12 by the bracket 11. As another installation method, the cylinder 22 can also be directly connected to the feed pipe 1, which is suitable for specific occasions.

[0044] The working principle of this embodiment is as follows: When the feed pipe 1 needs to be opened, high-pressure medium (compressed air is used in this embodiment) is injected into the compression chamber through the servo pressure regulating valve. The pressure in the compression chamber increases, pushing the piston to move downward and compressing the spring in the reset chamber 200. At the same time, the air in the reset chamber 200 is discharged to the atmosphere through the first conveying pipe 101. The piston drives the material control plug to move downward through the piston rod 24, and the lower port of the feed pipe 1 is opened, and the material falls by gravity.

[0045] When it is necessary to close the feed pipe 1, the pressure in the compression chamber is quickly released by the servo vent valve. The spring returns and pushes the piston upward, which in turn drives the control plug to rise until the control plug is in close contact with the lower end of the feed pipe 1, thus closing the feed pipe and stopping the feeding.

[0046] When the material flow rate needs to be adjusted, the pressure in the compression chamber is precisely controlled by the servo pressure regulating valve, and the compression of the spring is adjusted to precisely control the material control plug at a certain intermediate position, thereby achieving continuous adjustment of the opening of the material pipe 1 and thus controlling the material flow rate. Working scenario: When the material level in the upper bed fluctuates, the material level signal is fed back to the external control system. The control system regulates the servo pressure regulating valve 4 and the servo venting valve 5 to pressurize or release air into the compression chamber 100, precisely adjusting the pressure in the compression chamber 100 and adjusting the compression of the spring, thereby precisely controlling the position of the material control plug, adjusting the material flow rate, and ultimately stabilizing the upper bed material level within a certain height.

[0047] A multi-layer fluidized bed, employing the feeding device between the multi-layer fluidized bed as described in this embodiment, is used for direct reduction ironmaking.

[0048] Example 2 like Figure 2 As shown, the difference from Embodiment 1 is that the reset drive unit includes a gas drive unit and an auxiliary elastic element 6. The gas drive unit is connected to the reset chamber 200 through the second delivery pipe 201 and is used to introduce compressed gas to drive the piston 23 to move upward. The auxiliary elastic element 6 is disposed inside the cylinder 22, with one end connected to the lower end face of the piston 23 and the other end connected to the bottom of the cylinder 22, and is used to drive the piston 23 to return to its original position when the gas drive part is depressurized. The auxiliary elastic element 6 is a spring.

[0049] The gas drive unit and the gas drive section share the same gas supply system. The first delivery pipe 101 and the second delivery pipe 201 are connected to the gas supply system via a reversing valve 7. The reversing valve 7 is used to automatically switch the gas path. In this embodiment, the piston's rise and fall are both driven and controlled by compressed gas. The gas supply system is a gas pump located outside the fluidized bed, directly utilizing air as the gas source.

[0050] Example 3 like Figure 4 As shown, the difference from Embodiment 1 is that the annular retaining dam 10 is an intermittent annular plate structure with notches along the circumference.

Claims

1. A feeding device between layers of a multi-layer fluidized bed, characterized in that: It includes a feeding pipe (1), a material control unit (2) disposed below the feeding pipe (1), a gas drive unit and a reset drive unit; The feed pipe (1) passes through the air distribution plate between two adjacent fluidized beds, and the lower outlet of the feed pipe (1) is set downward; The material control unit (2) includes a material control plug (21), a cylinder (22), a piston (23) and a piston rod (24). The piston (23) is slidably disposed inside the cylinder (22), and the piston rod (24) is disposed above the piston (23). The cylinder (22) is fixedly installed inside the fluidized bed and located below the outlet of the feed pipe (1); The material control plug (21) is fixedly installed on the top of the piston rod (24); The piston (23) divides the cylinder (22) into a compression chamber (100) and a reset chamber (200), and an air gap (300) is provided between the piston rod (24) and the cylinder (22). The gas drive unit is connected to the compression chamber (100) through the first delivery pipe (101) and is used to introduce compressed gas to drive the piston (23) to move downward. The reset drive unit is used to apply a driving force to the piston (23) after the gas drive unit is depressurized, so that the piston (23) moves upward.

2. The feeding device between the layers of a multi-layer fluidized bed according to claim 1, characterized in that: The reset drive unit is the elastic reset member (3), which is disposed in the cylinder (22). One end of the elastic reset member (3) is connected to the lower end face of the piston (23), and the other end is connected to the bottom of the cylinder (22). It is used to drive the piston (23) to reset upward when the gas drive unit is depressurized. The reset chamber (200) is provided with an exhaust pipe (202) connected to the outside of the fluidized bed; The first conveying pipeline (101) is equipped with a servo pressure regulating valve (4) and a servo venting valve (5); Preferably, the elastic reset element (3) is a spring.

3. The feeding device between the layers of a multi-layer fluidized bed according to claim 1, characterized in that: The reset drive unit includes a gas drive unit and an auxiliary elastic element (6). The gas drive unit is connected to the reset chamber (200) through a second delivery pipe (201) and is used to introduce compressed gas to drive the piston (23) to move upward. The auxiliary elastic element (6) is disposed inside the cylinder (22), with one end connected to the lower end face of the piston (23) and the other end connected to the bottom of the cylinder (22), and is used to drive the piston (23) to reset upward when the gas drive unit is depressurized; Preferably, the auxiliary elastic element (6) is a spring.

4. The feeding device between the layers of a multi-layer fluidized bed according to claim 3, characterized in that: The gas drive unit and the gas drive section adopt the same gas supply system. The first delivery pipe (101) and the second delivery pipe (201) are connected to the gas supply system through a reversing valve (7).

5. The feeding device between the layers of a multi-layer fluidized bed according to claim 1, characterized in that: The cylinder (22) is provided with a protective cover (8) connected to the material control plug (2) on the outside. The protective cover (8) covers the upper part of the cylinder (22) and there is a gap between the protective cover (8) and the outer wall of the cylinder (22).

6. The feeding device between layers of a multi-layer fluidized bed according to claim 1, characterized in that: It also includes a position sensor (9) and a control system, wherein the position sensor (9) is disposed on the material control plug (21) or piston (23); The control system is connected to the position sensor (9), the gas drive unit and the reset drive unit respectively, and is used to control the gas drive unit and the reset drive unit according to the position signal of the position sensor (9); The fluidized bed is equipped with a material level measuring device. In two adjacent fluidized bed layers, when the material level of the upper layer exceeds the preset height range, the material level measuring device collects the material level signal and feeds it back to the control system. The control system controls the position of the material control plug in the lower layer of the fluidized bed through the gas drive unit and the reset drive unit, and adjusts the feeding amount to keep the material level of the upper layer stable within the preset height range.

7. The feeding device between layers of a multi-layer fluidized bed according to claim 1, characterized in that: The material control plug (21) is a flat plate, a disc, or a cone with its tip pointing upwards; Preferably, the surface of the material control plug (21) is provided with a wear-resistant layer.

8. The feeding device between layers of a multi-layer fluidized bed according to claim 1, characterized in that: The upper surface of the material control plug (21) is provided with an annular retaining dam (10). Preferably, the annular retaining dam (10) is a complete ring or an intermittent ring with gaps along the circumference; Preferably, the upper surface of the material control plug (21) is provided with multiple coaxially arranged annular retaining walls (10).

9. The feeding device between layers of a multi-layer fluidized bed according to claims 1 to 8, characterized in that: The cylinder (22) is fixedly installed on the fluidized bed furnace shell (12) by a bracket (11); Or it can be directly connected to the feed pipe (1).

10. A multi-layer fluidized bed, employing the feeding device between the multi-layer fluidized bed as described in claims 1-9, characterized in that: Used for direct reduction iron smelting.

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