A multi-pillar chemical vapor deposition furnace system

Abstract

The application discloses a multi-column chemical vapor deposition furnace system, which comprises a temperature control mechanism, a flow field regulation mechanism and a loading mechanism; the temperature control mechanism comprises a plurality of lateral heaters, a central heater and a bottom heater; the lateral heaters are uniformly arranged on the inner wall of a furnace chamber; the central heater is arranged in the central region of the deposition furnace; and the bottom heater is arranged at the bottom of the deposition furnace; the flow field regulation mechanism comprises a gas inlet pipeline, a heating device and a plurality of staged air supplementing devices; the gas outlet of the gas inlet pipeline is connected with the inlet of the heating device; the outlet of the heating device is communicated with the deposition chamber of the deposition furnace; and the gas outlet of the staged air supplementing device is arranged on the inner wall of the furnace chamber; the loading mechanism comprises a plurality of columns, and a plurality of spaces for placing workpieces to be treated are uniformly arranged on the columns; and the deposition furnace system can fundamentally improve the problem of poor densification uniformity of the deposition layer of the workpieces to be treated.

Description

Technical Field

[0001] This application relates to the field of chemical vapor deposition furnace technology, and more particularly to a multi-column chemical vapor deposition furnace system. Background Technology

[0002] A chemical vapor deposition furnace is a high-temperature processing equipment used in chemical vapor deposition processes. It can control the temperature, pressure and process gas supply conditions inside the furnace chamber, allowing gaseous reactants to undergo chemical reactions on the surface of the workpiece substrate, thereby depositing solid functional coatings or materials.

[0003] However, existing chemical vapor deposition furnaces are limited by the temperature field and process gas distribution inside the furnace, resulting in poor density and uniformity of the deposited layer formed on the workpiece surface. Summary of the Invention

[0004] The main objective of this application is to provide a multi-column chemical vapor deposition furnace system, which aims to solve the technical problem of poor densification and uniformity of the deposition layer formed on the workpiece surface in existing chemical vapor deposition furnaces.

[0005] This application provides a multi-column chemical vapor deposition furnace system, comprising: a temperature control mechanism, including multiple side heaters, a central heater, and a bottom heater, all used to supply heat to the deposition chamber of the deposition furnace; the multiple side heaters are uniformly arranged on the inner wall of the furnace chamber, the central heater is located in the central region of the deposition chamber, and the bottom heater is located at the bottom of the deposition furnace; a flow field control mechanism, including an inlet pipe connected to an external process gas source, a heating device for preheating the process gas, and multiple staged gas replenishment devices for replenishing process gas into the deposition furnace; the outlet of the inlet pipe is connected to the bottom of the deposition furnace and connected to the inlet of the heating device, and the outlet of the heating device is connected to the deposition chamber; the outlets of the multiple staged gas replenishment devices are uniformly arranged on the inner wall of the furnace chamber; and a loading mechanism, including multiple columns of material uniformly arranged in the deposition chamber, with multiple spaces uniformly provided on the columns for placing workpieces to be processed.

[0006] Optionally, the system also includes a control mechanism, comprising: multiple temperature sensors, one of which is installed on the furnace wall near the side heater, center heater, and bottom heater, for real-time acquisition of the temperature at corresponding measuring points within the furnace; a mass flow controller, installed on the delivery pipe of each staged gas supply device, for monitoring and adjusting the process gas flow rate of the corresponding delivery pipe; multiple pressure sensors, evenly distributed on the furnace wall, for real-time acquisition of the pressure at corresponding measuring points within the furnace; multiple gas concentration sensors, evenly distributed on the furnace wall, for real-time acquisition of the process gas concentration at corresponding measuring points within the furnace; and a controller electrically connected to the multiple temperature sensors, mass flow controller, pressure sensors, and gas concentration sensors; the controller adjusts the output power of the side heater, center heater, and bottom heater, and controls the process gas flow rate of the inlet pipe and each staged gas supply device based on the real-time acquired temperature, flow rate, pressure, and process gas concentration data.

[0007] Optionally, the outlet of the gas outlet pipe of the deposition furnace is connected to a tail gas treatment and waste heat recovery mechanism, which includes a high-temperature condenser, a tar filter, a fine filter, an internal combustion generator, a lithium bromide unit, and a tail gas purification device connected in series. The inlet of the high-temperature condenser is connected to the gas outlet pipe of the deposition furnace.

[0008] Optionally, the multiple side heaters are divided into N groups, N≥3, and the N groups of side heaters are spaced apart in the vertical direction; the number of side heaters in each group is M, M≥4, and the M side heaters in each group are evenly arranged on the inner wall of the furnace around the center line of the furnace.

[0009] Optionally, the central heater is a columnar body, and the centerline of the central heater coincides with the centerline of the deposition chamber.

[0010] Optionally, the heating device is made of graphite material and is cone-shaped. The heating device is installed at the bottom of the deposition furnace and located in the central area of ​​the bottom of the deposition chamber. The heating device has a labyrinth-type or spiral process gas flow channel. When the heating device is powered on, it preheats the process gas flowing through the process gas flow channel.

[0011] Optionally, the bottom heater is annular and located above the heating device, and the upper surface of the bottom heater has multiple guide grooves extending radially along the bottom heater; the process gas output from the heating device flows upward through the central hole of the bottom heater to the upper surface of the bottom heater and flows outward along the guide grooves.

[0012] Optionally, the bottom heater includes multiple concentrically arranged heating rings and connecting ribs connecting each heating ring, with a process gas channel between two adjacent heating rings for process gas to pass through; the bottom heater is located above the heating device, and the process gas output from the heating device flows upward into the deposition chamber through the process gas channel.

[0013] Optionally, the staged gas supply device includes a delivery pipe and at least one nozzle. One end of the delivery pipe is connected to an external process gas source, and the other end is connected to all the nozzles. All the nozzles are located on the inner wall of the furnace and face the sedimentation chamber at a preset angle.

[0014] Optionally, the side heater, center heater, and bottom heater are all made of isostatic graphite or carbon / carbon composite material.

[0015] Compared with the prior art, this application has the following beneficial effects: 1. By setting up side heaters, center heaters and bottom heaters, multi-zone coordinated heating is achieved around the furnace, in the center of the deposition chamber and at the bottom of the furnace body. This effectively offsets the heat radiation shielding problem caused by the arrangement of multiple material columns, eliminates the temperature difference between the center and the periphery of the deposition chamber, and optimizes the overall temperature field distribution inside the furnace. It ensures that the carbon source gas of the workpiece in each area of ​​the furnace is fully pyrolyzed and the temperature conditions are consistent, fundamentally improving the problem of poor uniformity of the densification of the deposition layer.

[0016] 2. By setting up a flow field control mechanism, the distribution of process gas flow field in the furnace can be effectively optimized; by preheating the bottom air intake with a heating device, the temperature difference problem caused by the cold air flow entering the deposition chamber is eliminated. At the same time, combined with the bottom main air intake and the multi-position graded gas replenishment structure on the inner wall of the furnace, the concentration of process gas between the outer and inner layers of the material column, and between the upper and lower parts, can be balanced. This avoids the defects of excessive gas on the outer workpiece forming a shell quickly and the insufficient gas source on the inner workpiece causing a delay in densification. As a result, the workpieces at all positions can complete the densification deposition process stably and uniformly.

[0017] 3. By evenly arranging multiple material columns in the sedimentation chamber, more material columns can be set in the sedimentation chamber while ensuring the sedimentation quality of the sediment layer, thereby improving the space utilization rate of the sedimentation chamber. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a multi-column chemical vapor deposition furnace system proposed in an embodiment of this application; Figure 2 This is a schematic diagram of the structure of the temperature control mechanism installed inside the furnace according to an embodiment of this application; Figure 3 This is a schematic diagram of the structure of the charging mechanism installed inside the furnace according to an embodiment of this application; Figure 4 This is a schematic diagram of the flow field control mechanism and the charging mechanism installed inside the deposition furnace according to the embodiments of this application; Figure 5 This is a schematic diagram of the exhaust gas treatment and waste heat recovery mechanism proposed in the embodiments of this application.

[0019] The attached diagrams are labeled as follows: 1. Furnace wall; 2. Furnace cover; 3. Furnace bottom; 4. Vacuum mechanism; 5. Water cooling mechanism; 6. Controller; 7. Temperature control mechanism; 71. Side heater; 72. Center heater; 73. Bottom heater; 74. Temperature controller; 75. Temperature sensor; 8. Flow field control mechanism; 81. Inlet pipe; 82. Heating device; 83. Staged gas supply device; 84. Mass flow controller; 85. Gas collection hood; 86. Outlet pipe; 9. Tail gas treatment and waste heat recovery mechanism; 91. High-temperature condenser; 92. Tar filter; 93. Fine filter; 94. Internal combustion generator; 95. Lithium bromide generator unit; 96. Tail gas purification equipment; 97. Exhaust fan; 98. Chimney; 10. Charging mechanism; 101. Material column; 102. Workpiece placement rack; 103. Gas flow channel. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0021] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0022] In this application, unless otherwise expressly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0023] Furthermore, if the embodiments of this application involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed in this application.

[0024] Carbon / carbon composites possess excellent properties such as high temperature resistance, high specific strength, and high specific modulus, and are widely used in many fields, including photovoltaic monocrystalline silicon production, aerospace thermal protection, aircraft brake components, and solid rocket engine throat liners. Chemical vapor deposition (CVD) is the core process for preparing carbon / carbon composites. It involves placing a carbon fiber preform inside a deposition furnace, introducing hydrocarbon process gases, and decomposing the gases at high temperatures to deposit carbonaceous structures on the carbon fiber surface, thus achieving the densification of the carbon fiber preform. With the photovoltaic monocrystalline silicon industry moving towards larger scales, the market demand for carbon / carbon thermal field components such as crucibles, flow guides, and insulation cylinders used in large monocrystalline furnaces has increased significantly. Large multi-column deposition furnaces are gradually being applied to the mass production of carbon / carbon composites. While existing large-scale multi-column deposition furnaces can meet the needs of simultaneous deposition of multiple workpieces, they still suffer from numerous structural and technological defects in actual use, severely restricting product quality, production efficiency, and energy-saving and environmental performance. Firstly, the temperature field uniformity within the furnace is poor. Large deposition furnaces have large furnace chambers and large quantities of material, making it easy for the heat radiated from the side heaters to the furnace center to be blocked by the material columns. This results in the temperature at the center of the deposition chamber being lower than the surrounding temperature, leading to insufficient pyrolysis of the carbon source gas in the low-temperature region. Furthermore, the existing heating structure relies solely on a single-layer side heater, failing to achieve precise and uniform temperature control within the deposition chamber, significantly affecting the densification uniformity of the deposited layer. Secondly, the flow field distribution within the furnace is uneven. Traditional deposition furnace processes have a single gas flow path, easily resulting in insufficient gas supply and densification of the outer layer of the workpiece. The problems include: rapid crusting and clogging of pores, insufficient gas in the inner layer and bottom of the workpiece, and delayed densification. At the same time, the equipment lacks a gas preheating structure, and the low temperature gas intake at the bottom can easily cause excessive temperature difference between the top and bottom of the furnace, further aggravating the defects in deposition uniformity. Third, the process energy efficiency and environmental protection are insufficient. The carbon source gas utilization rate of the deposition process is only 10% to 30%. A large amount of unreacted hydrocarbons and pyrolysis by-products are discharged with the tail gas. Existing equipment mostly directly discharges or simply treats the tail gas, which not only seriously wastes the chemical energy and waste heat in the tail gas, causing energy loss, but also increases the environmental treatment burden. Fourth, the furnace space utilization rate is low. The heater and material column layout design of the existing deposition furnace is unreasonable, and the effective space inside the furnace cannot be fully utilized. The single furnace charging capacity is limited, making it difficult to adapt to the needs of large-scale and large-volume production.

[0025] Reference Figures 1-5This embodiment provides a multi-column chemical vapor deposition furnace system, including: a temperature control mechanism 7, comprising multiple side heaters 71, a central heater 72, and a bottom heater 73, all used to supply heat to the deposition chamber of the deposition furnace; the multiple side heaters 71 are uniformly arranged on the inner wall of the furnace chamber of the deposition furnace, the central heater 72 is located in the central area of ​​the deposition chamber of the deposition furnace, and the bottom heater 73 is located at the bottom of the deposition furnace; a flow field control mechanism 8, comprising an inlet pipe 81 connected to an external process gas source, a heating device 82 for preheating the process gas, and multiple staged gas replenishment devices 83 for replenishing process gas into the deposition furnace; the outlet of the inlet pipe 81 is connected to the bottom of the deposition furnace and connected to the inlet of the heating device 82, and the outlet of the heating device 82 is connected to the deposition chamber of the deposition furnace; the outlets of the multiple staged gas replenishment devices 83 are uniformly arranged on the inner wall of the furnace chamber; and a loading mechanism 10, comprising multiple columns 101 uniformly arranged in the deposition chamber, each column 101 having multiple spaces uniformly provided for placing workpieces to be processed.

[0026] Specifically, before operation, the workpiece to be processed is placed in the placement space of the material column 101. During process operation, the side heater 71, center heater 72, and bottom heater 73 of the temperature control mechanism 7 work together to heat the furnace, providing heat to the deposition chamber from the side wall of the furnace, the center of the deposition chamber, and the bottom of the furnace, respectively, thereby improving the temperature uniformity inside the furnace. The external process gas source enters through the air inlet pipe 81 of the flow field control mechanism 8, and is preheated by the heating device 82 before being sent into the deposition chamber. At the same time, the staged gas replenishment device 83 replenishes the process gas into the furnace from multiple points on the inner wall of the furnace, compensating for gas consumption along the way, optimizing the flow field distribution inside the furnace, and ensuring a balanced carbon source gas concentration at each material column 101. The tail gas generated by the deposition reaction is sent to the tail gas treatment and waste heat recovery mechanism 9 through the gas outlet pipe 86. The tail gas treatment and waste heat recovery mechanism 9 purifies the tail gas and recovers the chemical energy and waste heat carried by the tail gas, realizing energy reuse and compliant tail gas emissions.

[0027] Specifically, the deposition furnace has a furnace cover 2 at the top and a furnace bottom at the bottom; the furnace body is connected to a vacuum mechanism 4 for evacuating the furnace chamber and a water cooling mechanism 5 for water cooling the furnace shell; a heating device 82 is located at the bottom of the deposition furnace; multiple material columns 101 are evenly arranged around the center line of the deposition chamber; a gas collecting hood 85 is provided at the top of the furnace chamber, the gas collecting hood 85 is a conical or hemispherical shell structure; multiple gas outlet pipes 86 are provided at the top of the furnace body, and the gas inlets of the multiple gas outlet pipes 86 extend into the gas collecting hood 85; the material column 101 is a frame structure, with a placement cavity arranged vertically inside; multiple workpiece placement racks 102 are arranged at equal intervals along the vertical direction in the placement cavity; the workpiece to be processed is placed on the workpiece placement rack 102; the space between adjacent workpiece placement racks 102 is for placing the workpiece to be processed; and a gas flow channel 103 for process gas flow is provided between adjacent material columns 101.

[0028] Furthermore, the system also includes a control mechanism, comprising: multiple temperature sensors 75, one of which is installed on each of the furnace walls 1 of the deposition furnace near the side heaters 71, the central heater 72, and the bottom heater 73; the temperature sensors 75 are used to collect the temperature at the corresponding measuring points inside the furnace in real time; a mass flow controller 84, which is installed on the delivery pipe of each staged gas supply device 83; the mass flow controller 84 is used to monitor and adjust the process gas flow rate of the corresponding delivery pipe; and multiple pressure sensors, evenly distributed on the furnace walls 1 of the deposition furnace. The pressure sensors are used for... The pressure at corresponding measuring points inside the furnace is collected in real time; multiple gas concentration sensors are evenly arranged on the furnace wall 1 of the deposition furnace, and the gas concentration sensors are used to collect the process gas concentration at corresponding measuring points inside the furnace in real time; the controller 6 is electrically connected to multiple temperature sensors 75, a mass flow controller, multiple pressure sensors and multiple gas concentration sensors respectively; based on the real-time collected temperature, flow, pressure and process gas concentration data, the controller 6 adjusts the output power of the side heater 71, the center heater 72 and the bottom heater 73, and controls the process gas flow of the gas inlet pipeline 81 and each stage gas replenishment device 83.

[0029] Specifically, during the process operation, the temperature sensor 75, pressure sensor, and gas concentration sensor of the control mechanism collect the temperature, pressure, and process gas concentration signals at each measuring point in the furnace in real time and transmit them to the controller 6. Based on the real-time detection data, the controller 6 adjusts the output power of the side heater 71, the center heater 72, and the bottom heater 73 to regulate the furnace temperature distribution. On the other hand, it adjusts the process gas flow rate of the gas inlet pipe 81 and each staged gas supply device 83 through the mass flow controller 84, thereby coordinating the regulation of the temperature field, pressure field, and gas concentration field in the furnace to meet the deposition process requirements.

[0030] Specifically, the controller 6 is equipped with an optimization algorithm that dynamically adjusts the output power of the side heater 71, the center heater 72, and the bottom heater 73 based on real-time collected temperature, flow rate, pressure, and process gas concentration data. It also controls the process gas flow rate of the inlet pipe 81 and each staged gas supply device 83, thereby achieving coordinated control of the temperature field, flow field, and pressure field. Each of the side heater 71, the center heater 72, and the bottom heater 73 is equipped with an independent power supply and a temperature controller 74. The temperature sensor 75 feeds back the temperature data to the controller 6. The controller 6 and the temperature controller 74 are electrically connected. The controller sends power control commands to the temperature controller 74, and the temperature controller 74 controls the output power of the corresponding heater.

[0031] Furthermore, the outlet of the gas outlet pipe of the deposition furnace is connected to a tail gas treatment and waste heat recovery mechanism. The tail gas treatment and waste heat recovery mechanism 9 includes a high-temperature condenser 91, a tar filter 92, a fine filter 93, an internal combustion generator 94, a lithium bromide unit 95, and a tail gas purification device 96 connected in series. The inlet of the high-temperature condenser 91 is connected to the gas outlet pipe 86 of the deposition furnace.

[0032] Specifically, the exhaust gas from the deposition furnace enters the high-temperature condenser 91 through the exhaust pipe 86, and then passes through the tar filter 92 and the fine filter 93 to remove tar and particulate matter. The purified exhaust gas is then sent to the internal combustion generator 94 to recover chemical energy for power generation. The waste heat from the exhaust gas is utilized by the lithium bromide unit 95. Finally, the exhaust gas is treated by the exhaust gas purification equipment 96 to meet emission standards. The exhaust gas treatment and waste heat recovery mechanism 9 can separate and recover tar and carbon black from the exhaust gas, protecting downstream equipment; recovering the chemical energy and waste heat from the exhaust gas reduces production energy consumption; and the purified exhaust gas is discharged to reduce environmental pollution.

[0033] Specifically, the high-temperature condenser 91 is equipped with a cooling water circulation pipe for cooling the high-temperature exhaust gas outside the cooling water circulation pipe; the bottom of the high-temperature condenser 91 is equipped with a discharge pipe, through which tar-like substances in the exhaust gas are discharged and collected; the tar filter 92 is equipped with a filter element to filter out the tar in the exhaust gas; the fine filter 93 is used to further filter out impurities in the exhaust gas, and then the exhaust gas is introduced into the internal combustion generator 94, where the combustibles in the exhaust gas are burned. When the fuel in the exhaust gas is insufficient, fuel gas is added to the internal combustion generator 94 through the fuel gas replenishment pipe; then the exhaust gas is purified by the exhaust gas purification equipment 96 to remove sulfur and nitrogen oxides. The exhaust gas purification equipment 96 includes a denitrification device and an alkaline absorption tower connected in series. The fine filter 93 is also connected to the induced draft fan 97, which acts as a power source to continuously push the exhaust gas to the internal combustion generator 94 for energy recovery; the outlet of the exhaust gas purification equipment 96 is also connected to a chimney 98, through which the exhaust gas is discharged into the atmosphere. Furthermore, the multiple side heaters 71 are divided into N groups, N≥3, and the N groups of side heaters are arranged at intervals in the vertical direction; the number of side heaters in each group is M, M≥4, and the M side heaters in each group are evenly arranged on the inner wall of the furnace around the center line of the furnace.

[0034] Specifically, in this embodiment, N is 3 and M is 6. During operation, each group of heaters can independently adjust its power to radiate heat to the deposition chamber from different circumferential and vertical positions. Together with the other heaters, they can jointly adjust the furnace temperature, realize zoned temperature control in the circumferential and vertical directions of the furnace, reduce the temperature difference between the upper and lower parts of the furnace and in the circumferential direction, improve the temperature uniformity of the deposition chamber, and enhance the consistency of workpiece deposition densification.

[0035] Furthermore, the central heater 72 is a columnar body, and the centerline of the central heater 72 coincides with the centerline of the deposition chamber.

[0036] Specifically, the central heater 72 extends along the furnace body axially, and its height is adapted to the effective deposition height. In this embodiment, the central heater 72 is a cylindrical cage-shaped frame structure assembled from multiple longitudinally arranged graphite rods and multiple annular graphite connectors. In other embodiments, the central heater 72 can also be a heat source formed by multiple vertical heating rods evenly arranged circumferentially along the center line. The central heater 72 is arranged coaxially with the deposition chamber and can radiate heat from the center of the furnace outward, making up for the deficiency of insufficient heating of the central area by the side heaters and reducing the radial temperature difference of the furnace.

[0037] Furthermore, the heating device 82 is made of graphite material and is cone-shaped. The heating device is installed at the bottom 3 of the deposition furnace and located in the central area of ​​the bottom of the deposition chamber. The heating device has a labyrinth-type or spiral process gas flow channel. When the heating device is powered on, it preheats the process gas flowing through the process gas flow channel.

[0038] Specifically, the heating device is shaped like a frustum or an umbrella, with its diameter gradually decreasing from bottom to top. The heating device is connected to a conductive cable for electrical connection with an external power source. When the conductive cable is connected to the external power source, the heating device, made of graphite material, generates heat to preheat the process gas in the process gas flow channel. The process gas is introduced into the labyrinthine or spiral process gas flow channel inside the heating device 82. The conical heating device is energized and generates heat to preheat the process gas flowing through the flow channel. The preheated process gas is then sent into the deposition chamber. The conical heating device is arranged at the center of the bottom of the deposition chamber. By using the internal flow channel, the gas heating path is extended, the process gas is fully preheated, and the problem of low temperature at the furnace bottom caused by cold air flow is avoided, thus improving the temperature and airflow distribution inside the furnace.

[0039] Furthermore, the bottom heater 73 is annular and located above the heating device. Multiple guide grooves extending radially along the upper surface of the bottom heater 73 are formed. The process gas output from the heating device flows upward through the central hole of the bottom heater 73 to the upper surface of the bottom heater 73 and flows outward along the guide grooves to the deposition chamber.

[0040] Specifically, the process gas flowing out from the heating device 82 passes through the central hole of the bottom heater 73 and reaches its upper surface. The gas diffuses and flows into the deposition chamber along the radially arranged guide grooves. The bottom heater 73 is energized and heats up to supplement the heat of the furnace bottom area. The guide grooves can disperse and guide the process gas, making the circumferential distribution of the bottom gas more uniform. The annular bottom heater 73 compensates for the heat of the furnace bottom, eliminates the cold zone at the bottom, and optimizes the temperature and flow field state at the bottom of the furnace.

[0041] Furthermore, in other embodiments, the bottom heater 73 includes a plurality of concentrically arranged heating rings and connecting ribs connecting each heating ring, and a process gas channel for process gas to pass through is provided between two adjacent heating rings; the bottom heater 73 is located above the heating device, and the process gas output from the heating device flows upward into the deposition chamber through the process gas channel.

[0042] Specifically, multiple concentric heating rings are connected by connecting ribs. The bottom heater 73 is composed of multiple layers of concentric heating rings and connecting ribs. The concentrically arranged heating rings can provide heat in zones, reducing the temperature difference at the bottom of the furnace. The process gas channel allows the gas to diffuse upwards evenly through multiple channels, improving the airflow distribution at the bottom of the furnace and enhancing the uniformity of the temperature field and flow field at the bottom of the deposition chamber.

[0043] Furthermore, the staged gas supply device 83 includes a delivery pipe and at least one nozzle. One end of the delivery pipe is connected to an external process gas source, and the other end is connected to all the nozzles. All the nozzles are located on the inner wall of the furnace and face the deposition chamber at a preset angle.

[0044] Specifically, the process gas source is delivered to each nozzle of the staged gas replenishment device 83 through the delivery pipeline. The nozzles spray the process gas into the deposition chamber at a preset angle, replenishing the carbon source gas at different positions in the furnace, compensating for gas consumption along the way, balancing the gas concentration in various parts of the furnace, alleviating the problem of excessively dense and rapid crusting on the outer layer of the workpiece, and improving the uniformity of workpiece deposition.

[0045] Furthermore, the side heater 71, the center heater 72, and the bottom heater 73 are all made of isostatic graphite or carbon / carbon composite material.

[0046] Specifically, isostatically pressed graphite and carbon / carbon composite materials have suitable high-temperature resistivity. When energized, they generate radiant heat through the resistance effect and transfer heat to the deposition chamber through thermal radiation. They can withstand the high-temperature environment of CVD furnaces ranging from 800 to 2200°C. All heaters include a heater body made of graphite and a conductive device connected to an external power source. The conductive device is connected to the heater body, and heating is performed by energizing the heater body.

[0047] In addition, this embodiment also provides a specific application of a multi-column chemical vapor deposition furnace system, which is mainly used for the batch preparation of large cylindrical carbon / carbon composite hot zone crucibles (outer diameter 800mm~1200mm, height 600mm~1000mm).

[0048] Furnace structure and material column layout: The furnace has an inner diameter of 2200mm and an effective deposition height of 1800mm. It is equipped with 6 material columns 101, each with an independent frame structure. Eight layers of workpiece placement racks 102 are arranged from top to bottom, each layer can hold one large cylindrical carbon fiber preform, and the spacing between each layer is 150mm. A gas guide channel with a width of 80~120mm is reserved between adjacent material columns 101 to ensure that the gas can flow evenly from the center to the edge.

[0049] Temperature control mechanism 7: Side heaters 71: Three sets of side heaters 71 are arranged along the furnace body axis, located at the lower part (200mm from the furnace bottom), middle part (900mm from the furnace bottom), and upper part (1600mm from the furnace bottom) of the furnace body, respectively. Each set of side heaters 71 consists of 6 units evenly arranged around the circumference of the furnace body; each side heater 71 is an arc-shaped graphite plate, 40mm thick, with an arc length of approximately 400mm and a height of 250mm; each side heater 71 is independently connected to a 30kW medium-frequency induction power supply and equipped with an S-type double platinum-rhodium thermocouple (PtRh30-PtRh6) for temperature measurement; Center heater 72: Adopts a cylindrical cage structure, with an outer diameter of 400mm and a height of 1800mm, consisting of 8 longitudinal graphite rods and 4 layers of annular graphite connectors. The central heater 72 is independently connected to a 100kW medium-frequency induction power supply, and four thermocouples are arranged along its height (located at positions 0.3H, 0.5H, 0.7H, and 0.9H from the bottom, respectively, where H is the total height of the deposition chamber); the bottom heater 73 is located in the central area of ​​the furnace bottom, and is a circular plate structure (600mm in diameter and 30mm in thickness). The upper surface is provided with radial guide ribs (10mm in height and 8mm in width, a total of 12 ribs), which are independently connected to a 20kW power supply and equipped with a thermocouple.

[0050] Flow field control mechanism 8: The furnace bottom is equipped with 14 independent air inlet pipes 81 (inner diameter 15mm, 316L stainless steel), evenly distributed around the circumference and center of the furnace bottom. Each pipe converges into a heating device 82 (graphite material, bottom diameter 500mm, top diameter 300mm, height 200mm), which has multiple layers of spiral airflow preheating channels inside (channel cross-section 10mm×10mm, spiral number 5 turns). After the gas is heated to 1000±20℃ in the channel, it flows upwards evenly along the guide plate (8mm diameter, 15mm spacing) at the top of the heating device 82. The staged gas replenishment device 83 has four layers of replenishment rings along the height of the furnace sidewall, located at 300mm, 700mm, 1100mm, and 1500mm from the furnace bottom. Each replenishment ring consists of eight circumferentially distributed nozzles, each with a 6mm diameter, spraying at a 45° downward angle to the horizontal plane into the furnace. Each replenishment ring is equipped with an independent mass flow controller (range 0~20L / min, accuracy ±1%FS), which can be adjusted according to the working conditions. The process requires the addition of natural gas, propane, or argon dilution gas; the charging mechanism 10: an independent gas supply pipe (6mm inner diameter) is installed at the upper part of each material column 101 (between the 7th and 8th layers), which is introduced from the top of the furnace and a micro nozzle is installed at the end, which can individually adjust the gas microenvironment at the top of each material column, with a flow control range of 0~5L / min; a conical gas collecting hood (cone angle 90°, lower diameter 2000mm, upper diameter 300mm) is installed at the top of the furnace, with 7 independent gas outlets at the top of the gas collecting hood, corresponding to 7 material columns respectively. Each gas outlet is connected to an independent gas outlet pipe 86 and a manual ball valve, which facilitates the adjustment of the gas extraction rate on different material columns.

[0051] Exhaust gas treatment and waste heat recovery mechanism 9: High-temperature condenser 91: Vertical cylindrical structure (volume 1.5m³), equipped with internal cooling coils (cooling water inlet temperature ≤25℃, outlet temperature ≤40℃), condensed tar is periodically collected from the bottom of the tank (tar collection rate ≥80%); Tar filter 92: Internally equipped with multiple layers of metal wire mesh (two layers each of 20 mesh, 40 mesh, and 80 mesh) and high-temperature resistant non-woven fabric filter element (pore size 5μm). Filtration accuracy ≥95%; Fine filter 93: Employs a ceramic membrane filter (membrane pore size 0.2μm) to further remove submicron carbon black particles; The purified exhaust gas (hydrogen content approximately 50%-80%) enters the internal combustion generator 94 (rated power 500KW). When the calorific value of the exhaust gas is insufficient, it is supplemented by natural gas combustion pipeline. The three-phase AC power generated by the internal combustion generator 94 is inverted and regulated before being fed into the CVD furnace to power it. The exhaust gas temperature of the internal combustion generator 94 is about 300-500℃. It is connected to the flue gas driven lithium bromide unit 95 through pipeline for cooling / heating, which can provide air conditioning / heating for the factory equipment and office areas, further improving energy utilization efficiency. Exhaust gas purification: After combustion, the flue gas is treated by an alkaline spray absorption tower (5% NaOH solution, gas-liquid ratio 1:2) to remove SO2 and a denitrification device to remove nitrogen oxides. After meeting the standards, it is discharged through a 15m chimney. Control mechanism: The Siemens PCS7 distributed control system is adopted. The central controller is embedded with a feedforward + feedback control algorithm based on a multi-field coupling model. Taking the temperature field as an example, 23 temperature measurement points are collected in real time (18 points for the peripheral heaters, 4 points for the central heaters, and 1 point for the bottom). The temperature distribution of the entire deposition chamber is predicted by a radial basis function neural network. Then, with "minimizing temperature difference" as the objective function (the objective is that the temperature difference between each column is ≤ ±5℃, and the temperature difference between different height layers of the column is ≤ ±8℃), the power distribution of each heater is dynamically adjusted. In terms of flow field control, based on the gas composition (concentration of methane, ethane, propane, hydrogen, etc.) at different locations in the furnace detected online by the gas chromatograph, the total gas intake at the bottom and the opening of each stage gas supply hole are adjusted to ensure that the carbon source gas concentration fluctuates by <10% along the height direction.

[0052] Process results: With a deposition cycle of 300 hours, the final average density of the carbon / carbon composite material is 1.52 g / cm³, and the maximum density deviation of different workpieces within the column is 4.8%. Compared with traditional single-heater CVD furnaces, the energy consumption per unit product is reduced by 28%, the tar recovery rate is 82%, the tail gas power generation meets 35% of the furnace auxiliary heating energy consumption, and the tail gas waste heat meets the cooling / heating needs of the plant's air conditioning system.

[0053] In addition, to shorten the deposition cycle, this embodiment uses a mixed gas source of "natural gas + propane" and a segmented variable parameter strategy for testing.

[0054] Process parameters: Heating phase (0~8h): Increase to 900℃ at 5℃ / min, under argon protection.

[0055] Pre-deposition stage (8-80h): Temperature 900-1050℃, pressure 1.5kPa-2.0kPa, natural gas flow rate 30L / min per column, propane flow rate 0L / min. This stage mainly involves slow deposition of pyrolytic carbon to avoid premature surface crusting.

[0056] Mid-deposition (80~200h): The temperature gradually rises to 1100℃, and the propane ratio gradually increases: natural gas:propane = 2:1 (volume ratio), the total carbon source flow rate per column is 50L / min, the pressure is 2.0kPa~2.5kPa, and the bottom first and second stage gas replenishment rings are opened at the same time, with each gas replenishment flow rate of 5~10L / min.

[0057] During the later stages of deposition (200~280h): the temperature was kept constant at 1150℃, the ratio of natural gas to propane was 1:2, the total carbon source flow rate per column was 70L / min, the pressure was 2.5kPa~3.0kPa, all four-stage gas supply rings were activated, and the independent gas supply flow rate of the column was finely adjusted (2L / min~4L / min) based on the online gas analysis results at the top of the column.

[0058] Results: The deposition period was shortened to 280 hours, the average density increased to 1.58 g / cm³, and the density deviation was ≤3.2%. The tar collection rate increased to 86%, and the proportion of waste heat power generation in auxiliary heating energy consumption increased to 40%.

[0059] Comparative example: A comparative furnace with the same furnace body size but without a central heater, without staged gas replenishment, and with traditional single-path gas inlet, requires a deposition cycle of 420 hours, with an average density of only 1.35 g / cm³, and a density deviation of up to 18% within the material column. It is also accompanied by defects such as surface crusting and internal porosity in the later stage. Therefore, the multi-column chemical vapor deposition furnace system of this application can fundamentally improve the problem of poor uniformity of deposited layer densification and the problem of insufficient tail gas treatment capacity.

[0060] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A multi-column chemical vapor deposition furnace system, characterized in that, include: The temperature control mechanism includes multiple side heaters, a central heater, and a bottom heater, all used to transfer heat to the deposition chamber of the deposition furnace; the multiple side heaters are evenly arranged on the inner wall of the furnace chamber of the deposition furnace, the central heater is located in the central area of ​​the deposition chamber of the deposition furnace, and the bottom heater is located at the bottom of the deposition furnace; The flow field control mechanism includes an inlet pipe connected to an external process gas source, a heating device for preheating the process gas, and multiple staged gas replenishment devices for replenishing process gas into the deposition furnace; the outlet of the inlet pipe is connected to the bottom of the deposition furnace and connected to the inlet of the heating device, and the outlet of the heating device is connected to the deposition chamber of the deposition furnace; the outlets of the multiple staged gas replenishment devices are evenly arranged on the inner wall of the furnace. The loading mechanism includes multiple material columns evenly arranged in the deposition chamber, and multiple spaces for placing the workpieces to be processed are evenly provided on the material columns.

2. The multi-column chemical vapor deposition furnace system as described in claim 1, characterized in that, It also includes a control mechanism, which comprises: Multiple temperature sensors are provided, with one temperature sensor installed on each of the furnace walls near the side heater, the center heater, and the bottom heater. These temperature sensors are used to collect the temperature of the corresponding measuring points inside the furnace in real time. A mass flow controller is provided on the delivery pipeline of each of the staged gas supply devices. The mass flow controller is used to monitor and adjust the process gas flow rate of the corresponding delivery pipeline. Multiple pressure sensors are evenly arranged on the furnace wall of the deposition furnace. The pressure sensors are used to collect the pressure at corresponding measuring points in the furnace in real time. Multiple gas concentration sensors are evenly arranged on the furnace wall of the deposition furnace. The gas concentration sensors are used to collect the process gas concentration at the corresponding measuring points in the furnace in real time. The controller is electrically connected to multiple temperature sensors, a mass flow controller, multiple pressure sensors, and multiple gas concentration sensors. Based on real-time collected temperature, flow rate, pressure, and process gas concentration data, the controller adjusts the output power of the side heater, the center heater, and the bottom heater, and controls the process gas flow rate of the inlet pipeline and each staged gas supply device.

3. The multi-column chemical vapor deposition furnace system as described in claim 1, characterized in that, The outlet of the gas outlet pipe of the deposition furnace is connected to a tail gas treatment and waste heat recovery mechanism. The tail gas treatment and waste heat recovery mechanism includes a high-temperature condenser, a tar filter, a fine filter, an internal combustion generator, a lithium bromide unit, and a tail gas purification device connected in series. The inlet of the high-temperature condenser is connected to the gas outlet pipe of the deposition furnace.

4. The multi-column chemical vapor deposition furnace system as described in claim 1, characterized in that, The multiple side heaters are divided into N groups, N≥3, and the N groups of side heaters are spaced apart in the vertical direction; each group has M side heaters, M≥4, and the M side heaters in each group are evenly arranged circumferentially around the center line of the furnace on the inner wall of the furnace.

5. The multi-column chemical vapor deposition furnace system as described in claim 1, characterized in that, The central heater is cylindrical, and its centerline coincides with the centerline of the deposition chamber.

6. The multi-column chemical vapor deposition furnace system as described in claim 1, characterized in that, The heating device is made of graphite and is cone-shaped. It is installed at the bottom of the deposition furnace and located in the central area of ​​the bottom of the deposition chamber. The heating device has a labyrinth-type or spiral process gas flow channel. When the heating device is powered, it preheats the process gas flowing through the process gas flow channel.

7. The multi-column chemical vapor deposition furnace system as described in claim 6, characterized in that, The bottom heater is annular and located above the heating device. Multiple guide grooves extending radially along the upper surface of the bottom heater are formed. The process gas output from the heating device flows upward through the central hole of the bottom heater to the upper surface of the bottom heater and flows outward along the guide grooves.

8. The multi-column chemical vapor deposition furnace system as described in claim 6, characterized in that, The bottom heater includes multiple concentrically arranged heating rings and connecting ribs connecting each heating ring. There is a process gas channel between two adjacent heating rings for process gas to pass through. The bottom heater is located above the heating device, and the process gas output from the heating device flows upward into the deposition chamber through the process gas channel.

9. The multi-column chemical vapor deposition furnace system as described in claim 1, characterized in that, The graded gas supply device includes a delivery pipe and at least one nozzle. One end of the delivery pipe is connected to an external process gas source, and the other end is connected to all the nozzles. All the nozzles are located on the inner wall of the furnace and face the deposition chamber at a preset angle.

10. The multi-column chemical vapor deposition furnace system as described in claim 1, characterized in that, The side heater, center heater, and bottom heater are all made of isostatic graphite or carbon / carbon composite material.

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