Hydrogen reduction furnace for low-oxygen niobium powder preparation

Abstract

This application discloses a hydrogen reduction furnace for the preparation of low-oxygen niobium powder, belonging to the technical field of reduction furnace equipment. It includes a furnace body, heating system, temperature control system, and atmosphere system, and features a gradient composite insulated furnace body, independent zone heating, spatial array zoned PID temperature control, and atmosphere regulation. The three-layer gradient composite furnace body structure balances low-energy insulation with structural stability under high-temperature conditions. A twelve-point spatial infrared temperature measurement array combined with a main and auxiliary loop zoned PID compensation algorithm achieves high-precision uniform temperature control in the high-temperature reduction zone. Through full-process atmosphere optimization including hydrogen pre-purification, high-vacuum pre-evacuation and replacement, diffused gas distribution at the furnace bottom, and micro-positive pressure closed-loop pressure control, atmosphere dead zones and impurity residues are eliminated, preventing secondary oxidation of niobium powder. This invention can stably mass-produce ultra-low oxygen, highly consistent high-purity niobium powder, significantly improving equipment energy efficiency, temperature control accuracy, atmosphere purity, and adaptability to continuous industrial production, possessing extremely high engineering application and promotion value.

Description

Technical Field

[0001] This application relates to the field of reduction furnace equipment technology, and in particular to a hydrogen reduction furnace for the preparation of low-oxygen niobium powder. Background Technology

[0002] High-purity, low-oxygen niobium powder is a core raw material for preparing high-end niobium alloys, superconducting materials, electronic functional ceramics, and vacuum electronic devices. The oxygen content of niobium powder directly determines the mechanical properties, electrical stability, and high-temperature reliability of the end products. High-temperature hydrogen reduction is the core process for deoxidizing and purifying niobium powder and preparing low-oxygen, high-purity niobium powder. The overall performance of the hydrogen reduction furnace directly restricts the quality of the finished niobium powder. Existing conventional industrial hydrogen reduction furnaces are suitable for reducing ordinary metal powders. However, they have significant technical shortcomings and adaptation defects for the stringent requirements of ultra-high purity, low oxygen content, and high batch consistency of low-oxygen niobium powder: First, traditional furnace bodies mostly adopt a single-layer refractory insulation structure, which has limited heat insulation performance, large heat loss, and lacks a gradient heat-resistant structure and stress buffer design. Under the rapid cooling and heating conditions of continuous industrial production, problems such as cracking and peeling of the insulation layer and deformation of the furnace body are prone to occur, resulting in poor equipment operation stability and service life. Second, traditional equipment generally uses single-point or a small number of multi-point thermocouple contact temperature measurement. There are several issues with traditional methods. First, temperature measurement is delayed and has a large blind spot. Second, the uniform power heating mode cannot achieve precise temperature control in different zones. Third, the temperature difference in the high-temperature reduction zone is large and the temperature field is not uniform, resulting in uneven deoxidation of niobium powder in different areas and large fluctuations in the oxygen content of finished batches. Fourth, traditional gas supply methods are mostly direct gas supply from the top or side, which cannot fully penetrate the niobium powder layer. This easily creates dead air zones and residual oxygen in the furnace. In addition, there is no hydrogen pre-purification, high vacuum pretreatment, or precise micro-positive pressure closed pressure control system. The reducing atmosphere has a high impurity content, which can easily cause incomplete deoxidation of niobium powder and secondary oxidation at high temperature. Summary of the Invention

[0003] The present invention addresses the aforementioned problems in the existing technology by providing a hydrogen reduction furnace for the preparation of low-oxygen niobium powder.

[0004] The objective of this invention is primarily achieved through the following approach: A hydrogen reduction furnace for the preparation of low-oxygen niobium powder includes a furnace body, a heating system, a temperature control system, and an atmosphere system. The furnace body forms a reduction furnace cavity that can accommodate a boat of niobium powder. The walls of the furnace body, from the inside out, consist of: The heat-resistant inner lining is assembled from high-purity alumina fiber modules, and the long-term working temperature of the inner surface facing the reduction furnace cavity is ≥1200℃. The intermediate heat-insulating layer is filled in the annular space between the heat-resistant inner lining and the outer wall. It is formed by compacting nano-level heat-insulating material and has an overall thermal conductivity of ≤0.03W / (m•K). The outer jacket layer is made of stainless steel and has an internal circulating water cooling channel, which is completely wrapped around the outside of the middle heat insulation layer. The heating system includes multiple groups of silicon molybdenum rod heating elements arranged in sections along the length of the reduction furnace cavity and in circumferential zones. Each group of heating elements is controlled and independently powered. The temperature control system includes: The infrared temperature measurement unit consists of a spatial temperature measurement array composed of no less than ten infrared temperature sensors. The measurement points of this array correspond to the space of the niobium powder area in the reduction furnace cavity, and are distributed on multiple axial sections and circumferential orientations. It is configured to automatically switch to closed-loop temperature control logic when the furnace temperature rises to the high-temperature reduction range of 800℃ and above. The zoned temperature control unit is configured to receive the distributed temperature signal from the infrared temperature measurement unit and calculate the power output correction of each heating element group through a PID intelligent algorithm, so that the uniformity of the working temperature field in the reduction furnace cavity is controlled within ±5℃. The atmosphere system includes: The gas distribution unit includes at least one gas distribution pipe extending into the bottom of the reduction furnace chamber and along the length of the material boat. The gas distribution pipe has micro-holes or slit-type gas outlets on its wall and is configured to allow the introduced reducing hydrogen gas to rise from below the material boat and pass through the material layer in a diffuse manner. The exhaust treatment unit is connected to the exhaust pipe at the top of the reduction furnace chamber, and a flame arrester, a condenser collector and a tail gas treatment device are connected in series along the exhaust flow direction. The pressure maintenance unit is configured to stably maintain the working pressure inside the reduction furnace chamber at a slightly positive pressure of 50–300 Pa relative to the outside environment.

[0005] Preferably, the high-purity alumina fiber modules in the heat-resistant lining layer have an Al2O3 content of ≥95wt% and a module density range of 0.6~1.2g / cm3. Individual modules are assembled on the inner side wall of the furnace body through a wedge-shaped interlocking structure. A ceramic paper buffer transition layer with a thickness of 1~3mm is provided between the heat-resistant lining layer and the intermediate heat-insulating layer.

[0006] Preferably, the nanoscale heat insulation material filled in the intermediate heat insulation layer is selected from nanoporous heat insulation board, fumed silica nano heat insulation powder or a composite of the two, and the bulk density after filling and compaction is not greater than 0.4 g / cm3. The radial thickness of the intermediate heat insulation layer is 40% to 80% of the radial thickness of the heat-resistant inner lining layer.

[0007] Preferably, the infrared temperature sensor has twelve points, and the measuring points of the twelve-point infrared temperature array are divided into at least three cross-sectional positions in the axial direction of the reduction furnace cavity: the feed end section, the middle section, and the discharge end section. Each section has 3 to 5 measuring points arranged circumferentially. The infrared light path axes of each measuring point intersect near the outer contour of the niobium powder accumulation space in the material boat but do not directly contact the niobium powder or the material boat. Each measuring point is provided with a high-temperature resistant quartz window isolation element.

[0008] Preferably, the partitioned PID intelligent temperature control unit is configured to operate in the following manner: In each temperature control cycle, the temperatures of all measuring points {T1, T2, ..., T} of the twelve-point infrared temperature measurement array are read. n} Calculate the average temperature T in the material zone p With any measuring point temperature T i deviation ΔT i =T i -T p ; The average temperature T in the material zone p As the feedback quantity of the main loop, the temperature deviation ΔT at each measuring point is used. i As compensation for each zone's secondary circuit, the conduction angle or duty cycle of the silicon molybdenum rod heating element group in the corresponding axial section and circumferential orientation are adjusted respectively. The target temperature range is set to 950-1100℃. When the temperature at any measuring point deviates from the set value by more than ±5℃, the output increment calculation of the heating element in that zone is triggered. If the deviation is within the allowable range, the power allocation weight of the previous temperature control cycle is maintained.

[0009] Preferably, the air outlet on the air distribution pipe is a uniformly distributed micropore with a diameter of 0.3 to 1.0 mm, or an axial slit with a width of 0.2 to 0.8 mm. The air distribution pipe is made of high-temperature heat-resistant stainless steel or alloy material, and a porous corundum protective sleeve is fitted on the outside of the air distribution pipe. The atmosphere system is also equipped with a pre-gas purification branch, in which a dehydrator, a deoxygenation molecular sieve column and a particulate filter are sequentially arranged along the gas inlet direction to ensure that the dew point of the hydrogen entering the reduction furnace cavity is not higher than -60°C.

[0010] Preferably, the circulating water cooling channel of the outer jacket layer adopts a spiral or axially meandering flow channel configuration. The cross-sectional area and flow velocity of the flow channel are designed so that the outer surface temperature of the outer jacket layer does not exceed 75°C when the reduction furnace is running continuously at the highest operating temperature of 1100°C. Furthermore, a metal foil heat reflector is provided between the outer jacket layer and the intermediate heat-insulating layer. The number of metal foil layers is ≥1, and the material is aluminum foil or 304 stainless steel polished thin strip.

[0011] Preferably, the furnace body is also equipped with a vacuum pre-evacuation subsystem, which includes a mechanical vacuum pump or Roots pump set and a vacuum isolation valve located on the exhaust pipe. It is configured to evacuate the reduction furnace chamber to a background vacuum of ≤10Pa before introducing reducing hydrogen, then perform one or more replacement purgings with inert gas, and then switch to reducing hydrogen gas intake to establish a slightly positive pressure atmosphere.

[0012] Preferably, the silicon molybdenum rod heating element of the heating system is arranged in a U-shaped suspension manner on the top and upper sides of the reduction furnace cavity, and is divided into an independently temperature-controlled preheating section, a high-temperature constant temperature section, and a slow cooling section along the length of the furnace cavity. The length of the high-temperature constant temperature section is not less than 50% of the total effective length of the reduction furnace cavity, and the infrared temperature measurement array corresponding to the high-temperature constant temperature section has the highest measurement point density.

[0013] Preferably, the ratio of the length to the inner diameter of the reduction furnace cavity is ≥4:1, and no exposed metal parts are exposed to the reducing atmosphere except for the heat-resistant inner lining. All electrical leads and gas connections passing through the furnace wall adopt a double-layer sealing structure: the inner layer is a metal bellows welded seal or ceramic-metal seal, and the outer layer is a fluororubber or perfluoroether O-ring forming a secondary seal.

[0014] In summary, compared with the prior art, the present invention has the following beneficial technical effects: (1) The present invention adopts a three-layer gradient heat insulation structure consisting of a high-alumina fiber inner lining, a nano-insulation middle layer, and a water-cooled jacket outer layer, combined with a heat reflector and a ceramic paper buffer transition layer. Compared with the traditional single-layer heat-insulating furnace body, it significantly reduces the heat loss of the furnace body and has a significant energy-saving effect. At the same time, relying on the thermal expansion matching characteristics and stress buffer structure of the multi-layer materials, it effectively adapts to the frequent temperature rise and fall conditions of industrial rapid cooling and heating, and eliminates faults such as furnace body deformation, cracking, and heat insulation layer falling off. The continuous operation stability, service life and production safety of the equipment are greatly improved, and the core problems of high energy consumption and poor working condition stability of traditional equipment are solved. (2) The present invention adopts a dedicated temperature control system with twelve-point spatial multidimensional temperature measurement, independent zone heating, and PID deviation compensation of main and auxiliary loops. Based on the segmented temperature control logic of 800℃ threshold, it takes into account both production efficiency and temperature control accuracy, and keeps the temperature field uniformity of the core reduction temperature zone within ±5℃. This solves the problems of large local temperature difference in the furnace, uneven reduction and deoxidation of niobium powder, and batch quality fluctuation, and significantly improves the consistency of low oxygen niobium powder finished products. (3) This invention constructs an ultra-low oxygen reduction system from all dimensions, including gas source purification, furnace background impurity removal, flow field optimization, pressure sealing, and tail gas purification. It eliminates problems such as atmosphere dead zones, oxygen residue, impure gas source, and external gas leakage in traditional equipment, effectively prevents secondary oxidation of niobium powder, ensures deep deoxygenation of niobium powder, and can stably prepare ultra-low oxygen high-purity niobium powder, meeting the stringent quality standards in the field of high-end new materials. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a module structure of the present invention. Detailed Implementation

[0016] The technical solution of the present invention will be further described in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the implementation of the present invention is not limited to the following embodiments, and any modifications and / or alterations made to the present invention will fall within the protection scope of the present invention.

[0017] like Figure 1 As shown, this invention discloses a technical solution for a hydrogen reduction furnace used in the preparation of low-oxygen niobium powder. The furnace cavity adopts a narrow and elongated closed structure with a length-to-diameter ratio of 4.5:1. This narrow and elongated structure effectively extends the residence time of the hydrogen gas flow, ensuring sufficient contact and reaction between the reducing gas and the niobium powder, and avoiding the problems of short-circuiting gas flow and insufficient reduction in short-cavity furnaces. The furnace wall adopts a three-layer gradient composite heat insulation structure, assembled layer by layer from the inside out: the innermost layer is a heat-resistant lining layer, made of high-purity alumina fiber modules with an Al2O3 content of 96wt% and a module density of 0.9g / cm³. 3 Each module is assembled and fixed to the inner wall of the furnace using a standardized wedge-shaped interlocking assembly structure. The wedge-shaped interlocking structure effectively avoids problems such as module loosening, falling off, and heat leakage through gaps under high-temperature conditions. The inner lining layer as a whole can withstand a high-temperature hydrogen reduction environment above 1200℃ for a long time, and the material has low gas release and no metal impurities are released, thus eliminating niobium powder contamination from a structural perspective. A 2mm thick alumina ceramic paper buffer transition layer is laid on the outside of the heat-resistant inner lining layer. This buffer layer can effectively absorb thermal stress under alternating high and low temperature conditions, buffer the slight difference in thermal expansion of the multi-layer structure, and avoid interlayer cracking and delamination failure.

[0018] The buffer transition layer is surrounded by an intermediate heat-insulating layer. In this embodiment, fumed silica nano-insulating powder and nanoporous heat insulation board are composite filling and compacted, and the overall bulk density after filling is controlled at 0.35 g / cm³. 3 The overall thermal conductivity was measured to be 0.028 W / (m•K), which is better than the limit of ≤0.03 W / (m•K). The radial thickness of the intermediate heat-insulating layer is set to 60% of the radial thickness of the heat-resistant inner lining. The above-mentioned stepped structure achieves step-by-step blocking of heat radiation and heat conduction, maximizing the reduction of static heat loss of the furnace body. A layer of 304 stainless steel polished thin strip heat reflector is laid on the outside of the intermediate heat-insulating layer, which can efficiently reflect the high-temperature infrared heat radiation in the furnace, further reducing radiative heat loss and enhancing the overall heat insulation effect.

[0019] The outermost layer is a stainless steel water-cooled jacket, integrally welded from 304 stainless steel. Internally, it employs an axially meandering water-cooled flow channel structure, with the flow channel cross-sectional area precisely matched to the cooling water flow rate. Under the equipment's maximum continuous operating temperature of 1100℃ and full-load production conditions, the furnace outer surface temperature is stably controlled below 70℃, far below the 75℃ threshold. This ensures the safety of high-temperature operation and locks the temperature field outside the furnace body through water cooling, preventing external temperature fluctuations from interfering with the reduction process inside the furnace. Furthermore, all electrical leads, hydrogen inlet pipes, vacuum lines, and detection interfaces penetrating the furnace wall utilize a double-layer composite sealing structure. The inner layer uses a ceramic-metal seal for high-temperature airtightness, while the outer layer uses a perfluoroether O-ring for secondary redundant sealing, solving the defects of traditional furnace body wall penetrations such as easy leakage and oxygen infiltration. Moreover, apart from the alumina fiber heat-resistant lining layer, no exposed metal structures inside the furnace cavity are exposed to the high-temperature hydrogen reducing atmosphere, effectively avoiding high-temperature hydrogen evolution corrosion of metals and impurity shedding that contaminates niobium powder.

[0020] The heating system uses high-temperature resistant U-shaped silicon molybdenum rods as the core heating elements. All silicon molybdenum rods are suspended at the top and upper sides of the furnace cavity to avoid material obstruction, dust accumulation, and corrosion, thus extending the service life of the heating elements. In this embodiment, the furnace cavity is precisely divided into three independent temperature control zones along its length: a preheating zone, a high-temperature constant-temperature zone, and a slow-cooling zone. The heating elements in each zone have independent wiring, independent power supply, and independent closed-loop power control, ensuring no interference between them. The high-temperature constant-temperature zone is the core deoxidation and reduction area for niobium powder, accounting for 55% of the total effective length of the furnace cavity, ensuring that most of the niobium powder is in a stable high-temperature reduction range. At the same time, the density of infrared thermometers deployed in the high-temperature constant-temperature zone is higher than that in the preheating and slow-cooling zones, achieving ultra-high-precision temperature monitoring and control of the core reaction zone. During equipment operation, the preheating section is responsible for rapidly raising the temperature of the materials in the furnace from room temperature to the pre-reaction temperature, avoiding niobium powder agglomeration and quality deterioration caused by rapid heating; the high-temperature constant-temperature section stably maintains the constant high-temperature environment required for deep deoxidation of niobium powder; the slow cooling section realizes the gradient cooling of materials, avoiding powder cracking and oxygen content rebound caused by rapid cooling. The three-stage zoned heating structure is perfectly adapted to the standardized reduction process of low-oxygen niobium powder of "heating-constant temperature-slow cooling".

[0021] In this embodiment, the temperature control system strictly employs a twelve-point spatially distributed infrared temperature measurement array. Three monitoring sections—the feed end, the middle section, and the discharge end—are evenly distributed axially, with four infrared temperature measurement points evenly distributed circumferentially in each section, totaling twelve measurement points. This provides comprehensive coverage of the core reaction space where the niobium powder boat is piled up inside the furnace. Each measurement point is equipped with a high-temperature resistant transparent quartz window isolation structure. This ensures complete transparency of the infrared temperature measurement light path, eliminates measurement lag, and prevents interference, while maintaining the overall airtightness of the furnace cavity. Simultaneously, it achieves non-contact temperature measurement, completely eliminating the defects of traditional thermocouple contact temperature measurement, such as probe oxidation, dust contamination, measurement lag, and single-point blind spots.

[0022] This invention employs threshold-based segmented temperature control logic, dividing the overall operation of the equipment into two temperature control stages: the first stage is a low-temperature rapid heating stage, where the system adopts a constant power rapid heating mode when the furnace temperature is below 800℃, maximizing equipment production efficiency and shortening non-process waiting time; the second stage is a high-precision closed-loop temperature control stage, where the system automatically switches to a zoned PID intelligent closed-loop control mode when the temperature at any measuring point in the furnace reaches the 800℃ threshold, entering the exclusive temperature control logic for high-temperature deep deoxidation of niobium powder.

[0023] Within the target high-temperature reduction range of 950–1100℃, the system continuously collects all temperature data from the twelve-point array at a fixed temperature control cycle, and calculates the average temperature T of the niobium powder working material zone inside the furnace in real time. p Simultaneously calculate the temperature deviation ΔT between the relative average temperature of each independent measuring point. i =T i -T p The control system employs a dual-closed-loop PID control logic with a main loop for constant temperature control and a secondary loop for deviation compensation, using the average temperature T in the material zone as the control threshold. p As the main feedback quantity to ensure the stability of the overall temperature range, the deviation ΔT of the measuring points in each zone is used. i As a secondary loop compensation, the conduction angle and power duty cycle of the silicon molybdenum rod heating element in the corresponding axial section and circumferential orientation are adjusted accordingly. When the temperature at any measuring point deviates from the process set value by more than ±5℃, the system immediately triggers the corresponding zone power increment correction calculation to quickly compensate for the local temperature difference. When the temperature deviation is within the allowable range, the power allocation weight of the previous cycle is maintained to avoid temperature oscillations caused by frequent fine-tuning. Through this dedicated control logic, this embodiment can stably control the uniformity of the temperature field throughout the furnace within ±5℃, solving the problems of uneven deoxidation of niobium powder and batch quality fluctuations caused by local overheating and insufficient local temperature change in traditional equipment.

[0024] The atmosphere system is a key module for ensuring deep deoxygenation of low-oxygen niobium powder and preventing secondary oxidation. This embodiment adopts a closed-loop atmosphere control process that includes gas source purification, vacuum impurity removal, diffused gas distribution, micro-positive pressure sealing, and tail gas purification. First, a dedicated pre-gas purification branch is configured at the hydrogen inlet. The hydrogen gas passes sequentially through a dehydrator, a deoxygenating molecular sieve column, and a high-precision particulate filter, removing water vapor, trace amounts of oxygen, and solid particulate impurities from the hydrogen gas in a step-by-step manner. After treatment, the hydrogen dew point is stable at ≤-60℃, ensuring high purity and low impurity of the reducing gas source from the source, and preventing impurity gases from participating in the reduction reaction and affecting the quality of niobium powder.

[0025] The furnace gas distribution structure adopts a bottom-dispersed upward gas distribution scheme. High-temperature alloy gas distribution pipes are arranged along the length of the material boat at the bottom of the furnace cavity. The pipe walls are uniformly perforated with micropores of 0.6mm diameter. A porous corundum protective sleeve is fitted over the gas distribution pipes to effectively prevent niobium powder dust from clogging the micropores and to protect the gas distribution structure from high-temperature oxidation and corrosion. High-purity hydrogen gas penetrates the niobium powder layer from the bottom of the material boat upwards through the micropores in a dispersed and uniform state, completely covering the powder accumulation area. This completely eliminates the problems of dead airflow and insufficient local hydrogen concentration that exist in traditional top-blowing and side-blowing gas inlets, allowing hydrogen gas to come into full and complete contact with niobium powder particles, ensuring that the deoxidation and reduction reaction proceeds uniformly and thoroughly.

[0026] Before the formal reduction process begins, the equipment first performs a pre-vacuum evacuation of the furnace chamber using a Roots pump set and a vacuum isolation valve. This stabilizes the background vacuum level inside the furnace to below 8 Pa, meeting the high vacuum impurity removal requirement of ≤10 Pa. Then, high-purity argon is introduced for two full-area replacement purging cycles to thoroughly remove residual air, water vapor, trace amounts of oxygen, and other impurities, fundamentally avoiding niobium powder oxidation caused by initial impurities. After replacement, high-purity reducing hydrogen is introduced, and the furnace pressure is dynamically adjusted in real time by the pressure maintenance unit to maintain a stable working pressure of 150 Pa slightly positive, within the optimal slightly positive pressure range of 50–300 Pa. This stable slightly positive pressure environment effectively prevents outside air from seeping into the furnace chamber through the sealed gaps, eliminating secondary oxidation of the niobium powder during the reduction process.

[0027] Meanwhile, a multi-stage exhaust gas treatment unit is installed at the top of the furnace cavity. The exhaust pipe is connected in series with a flame arrester, a condenser collector, and an exhaust gas combustion exhaust device along the flow direction. This can effectively capture byproducts such as niobium oxide dust and water vapor generated by the reduction reaction, and treat the reduction exhaust gas in a timely and harmless manner. This not only ensures the dynamic balance of airflow in the furnace, but also avoids the accumulation of byproducts that may affect the purity of the atmosphere in the furnace, and continuously maintains an ultra-low oxygen and high purity reduction environment in the furnace.

[0028] This embodiment achieves standardized reduction preparation of low-oxygen niobium powder through the aforementioned structure and control process. The overall equipment operates stably and the process has strong repeatability. Multiple batches of industrial-scale testing have verified that the composite gradient furnace structure of this invention, compared to traditional single-layer refractory and insulation furnaces, reduces overall heat loss, resulting in significant energy savings. It can withstand continuous mass production conditions with frequent rapid heating and cooling without furnace deformation, insulation layer detachment, or cracking. The temperature field uniformity within the furnace during the high-temperature reduction zone is stably controlled within ±5℃, and the deoxidation degree of niobium powder in each batch is highly consistent, with no localized incomplete reduction issues. Relying on a full-process high-purity atmosphere control system, the prepared niobium powder has extremely low oxygen content, high powder purity, and excellent batch consistency, solving the industry pain points of high oxygen content, large quality fluctuations, and low yield rates in traditional reduction furnaces. Simultaneously, the equipment exhibits excellent overall sealing performance, with no air leakage or oxygen permeation issues during long-term operation. Its structural stability, process adaptability, and industrial mass production capacity are far superior to existing traditional equipment.

[0029] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A hydrogen reduction furnace for the preparation of low-oxygen niobium powder, characterized in that, This includes the furnace body, heating system, temperature control system, and atmosphere system; The furnace body forms a reduction furnace cavity that can accommodate a boat of niobium powder. The walls of the furnace body, from the inside out, consist of: The heat-resistant inner lining is assembled from high-purity alumina fiber modules, and the long-term working temperature of the inner surface facing the reduction furnace cavity is ≥1200℃. The intermediate heat-insulating layer is filled in the annular space between the heat-resistant inner lining and the outer wall. It is formed by compacting nano-level heat-insulating material and has an overall thermal conductivity of ≤0.03W / (m·K). The outer jacket layer is made of stainless steel and has an internal circulating water cooling channel, which is completely wrapped around the outside of the middle heat insulation layer. The heating system includes multiple groups of silicon molybdenum rod heating elements arranged in sections along the length of the reduction furnace cavity and in circumferential zones. Each group of heating elements is controlled and independently powered. The temperature control system includes: The infrared temperature measurement unit consists of a spatial temperature measurement array composed of no less than ten infrared temperature sensors. The measurement points of this array correspond to the space of the niobium powder area in the reduction furnace cavity, and are distributed on multiple axial sections and circumferential orientations. It is configured to automatically switch to closed-loop temperature control logic when the furnace temperature rises to the high-temperature reduction range of 800℃ and above. The zoned temperature control unit is configured to receive the distributed temperature signal from the infrared temperature measurement unit and calculate the power output correction of each heating element group through a PID intelligent algorithm, so that the uniformity of the working temperature field in the reduction furnace cavity is controlled within ±5℃. The atmosphere system includes: The gas distribution unit includes at least one gas distribution pipe extending into the bottom of the reduction furnace chamber and along the length of the material boat. The gas distribution pipe has micro-holes or slit-type gas outlets on its wall and is configured to allow the introduced reducing hydrogen gas to rise from below the material boat and pass through the material layer in a diffuse manner. The exhaust treatment unit is connected to the exhaust pipe at the top of the reduction furnace chamber, and a flame arrester, a condenser collector and a tail gas treatment device are connected in series along the exhaust flow direction. The pressure maintenance unit is configured to stably maintain the working pressure inside the reduction furnace chamber at a slightly positive pressure of 50–300 Pa relative to the outside environment.

2. The hydrogen reduction furnace for preparing low-oxygen niobium powder according to claim 1, characterized in that, The high-purity alumina fiber modules in the heat-resistant lining layer have an Al2O3 content ≥95wt% and a module density ranging from 0.6 to 1.2 g / cm³. 3 The individual modules are assembled on the inner side wall of the furnace body through a wedge-shaped interlocking structure; a ceramic paper buffer transition layer with a thickness of 1 to 3 mm is provided between the heat-resistant inner lining layer and the intermediate heat-insulating layer.

3. The hydrogen reduction furnace for preparing low-oxygen niobium powder according to claim 1, characterized in that, The intermediate heat-insulating layer is filled with nanoscale heat-insulating material selected from nanoporous heat-insulating boards, fumed silica nano-insulating powder, or a composite of the two, and the bulk density after filling and compaction is not greater than 0.4 g / cm³. 3 The radial thickness of the intermediate heat-insulating layer is 40% to 80% of the radial thickness of the heat-resistant inner lining.

4. The hydrogen reduction furnace for preparing low-oxygen niobium powder according to claim 1, characterized in that, The infrared temperature sensor is provided with twelve points. The measuring points of the twelve-point infrared temperature array are divided into at least three cross-sectional positions in the axial direction of the reduction furnace cavity: the feed end section, the middle section, and the discharge end section. Each section is provided with 3 to 5 measuring points in the circumferential direction. The infrared light path axes of each measuring point intersect near the outer contour of the niobium powder accumulation space in the material boat, but do not directly contact the niobium powder or the material boat. Each measuring point is provided with a high-temperature resistant quartz window isolation component.

5. The hydrogen reduction furnace for preparing low-oxygen niobium powder according to claim 4, characterized in that, The partitioned PID intelligent temperature control unit is configured to operate in the following manner: In each temperature control cycle, the temperatures of all measuring points {T1, T2, ..., T} of the twelve-point infrared temperature measurement array are read. n } Calculate the average temperature T in the material zone p With any measuring point temperature T i deviation ΔT i =T i -T p ; The average temperature T in the material zone p As the feedback quantity of the main loop, the temperature deviation ΔT at each measuring point is used. i As compensation for each zone's secondary circuit, the conduction angle or duty cycle of the silicon molybdenum rod heating element group in the corresponding axial section and circumferential orientation are adjusted respectively. The target temperature range is set to 950-1100℃. When the temperature at any measuring point deviates from the set value by more than ±5℃, the output increment calculation of the heating element in that zone is triggered. If the deviation is within the allowable range, the power allocation weight of the previous temperature control cycle is maintained.

6. The hydrogen reduction furnace for preparing low-oxygen niobium powder according to claim 1, characterized in that, The air outlet on the air distribution pipe is a uniformly distributed micropore with a diameter of 0.3 to 1.0 mm, or an axial slit with a width of 0.2 to 0.8 mm. The air distribution pipe is made of high-temperature heat-resistant stainless steel or alloy material, and a porous corundum protective sleeve is fitted on the outside of the air distribution pipe. The atmosphere system is also equipped with a pre-gas purification branch, in which a dehydrator, a deoxygenation molecular sieve column and a particulate filter are sequentially arranged along the gas inlet direction to ensure that the dew point of the hydrogen entering the reduction furnace cavity is not higher than -60°C.

7. The hydrogen reduction furnace for preparing low-oxygen niobium powder according to claim 1, characterized in that, The circulating water cooling channel of the outer jacket layer adopts a spiral or axially meandering flow channel configuration. The cross-sectional area and flow velocity of the flow channel are designed so that the outer surface temperature of the outer jacket layer does not exceed 75°C when the reduction furnace is running continuously at the highest operating temperature of 1100°C. Furthermore, a metal foil heat reflector is provided between the outer jacket layer and the intermediate heat insulation layer. The number of metal foil layers is ≥1, and the material is aluminum foil or 304 stainless steel polished thin strip.

8. The hydrogen reduction furnace for preparing low-oxygen niobium powder according to claim 1, characterized in that, The furnace body is also equipped with a vacuum pre-evacuation subsystem, which includes a mechanical vacuum pump or Roots pump set and a vacuum isolation valve located on the exhaust pipe. It is configured to evacuate the reduction furnace chamber to a background vacuum of ≤10Pa before introducing reducing hydrogen, then perform one or more replacement purgings with inert gas, and then switch to reducing hydrogen gas intake to establish a slightly positive pressure atmosphere.

9. The hydrogen reduction furnace for preparing low-oxygen niobium powder according to claim 1, characterized in that, The silicon molybdenum rod heating element of the heating system is arranged in a U-shaped suspension on the top and upper sides of the reduction furnace cavity. Along the length of the furnace cavity, it is divided into an independently temperature-controlled preheating section, a high-temperature constant temperature section, and a slow cooling section. The length of the high-temperature constant temperature section is not less than 50% of the total effective length of the reduction furnace cavity, and the infrared temperature measurement array corresponding to the high-temperature constant temperature section has the highest measurement point density.

10. The hydrogen reduction furnace for preparing low-oxygen niobium powder according to any one of claims 1 to 9, characterized in that: The ratio of the length to the inner diameter of the reduction furnace cavity is ≥4:

1. Except for the heat-resistant inner lining, no bare metal parts are exposed to the reducing atmosphere on the inner wall of the furnace cavity. All electrical leads and gas line joints that pass through the furnace wall adopt a double-layer sealing structure: the inner layer is a metal bellows welded seal or ceramic-metal seal, and the outer layer is a fluororubber or perfluoroether O-ring forming a secondary seal.

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