Device and method for batch hot pressing and sintering of coated particle dispersion fuel pellets

Abstract

The present invention provides a batch hot pressing and sintering device for coated particle dispersion fuel pellets, comprising two furnace bodies, each of which is provided with a traveling mechanism at the bottom, wherein one of the furnace bodies is used for heating and pressurizing, and the other furnace body is used for cooling. The present invention also provides a batch hot pressing and sintering method for coated particle dispersion fuel pellets. The device and method provided by the present invention can improve the sintering efficiency and meet the needs of batch production of related fuels. The hot pressing and sintering device provided by the present invention shortens its cooling time to about 6 hours by arranging a double furnace body and a traveling mechanism and controlling the cooling of the furnace body through a helium flow rate of 1.5L / min, and matches the heating rate and hot pressing insulation time to about 6 hours.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel pellet preparation, and in particular to a device and method for batch hot pressing and sintering of coated particle dispersed fuel pellets. Background Art

[0002] Coated particle dispersion fuel pellets are TRISO particles encapsulated in a SiC matrix. Currently, the main method used is hot pressing of dispersion fuel pellets using a single furnace with heating and cooling and pressurization. The preparation throughput is 1 to 3 pieces per furnace, and the time required is relatively long, about 20 hours, which makes it difficult to meet the needs of mass production of related fuels. Summary of the Invention

[0003] The purpose of the present invention is to overcome the defects described in the prior art and thus provide a device and method for batch hot pressing and sintering of coated particle dispersion fuel pellets, which can improve the sintering efficiency and meet the needs of batch production of related fuels.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] A batch hot pressing and sintering device for coated particle dispersion fuel pellets comprises two furnace bodies. The bottom of each furnace body is provided with a traveling mechanism. One furnace body is used for heating and pressurizing, and the other furnace body is used for cooling.

[0006] The batch hot pressing and sintering device for coated particle dispersion fuel pellets further comprises a mold, the size of which is Φ (200-350) × 70 mm.

[0007] Furthermore, the furnace body has a size of Ø1.5m×1.7m.

[0008] Furthermore, heating elements are evenly distributed around the inner surface of the furnace body, and the furnace body is heated in 6 zones so that the temperature field in the furnace is evenly distributed.

[0009] Furthermore, the furnace body adopts a vertical structure and is fixed on the press platform, and copper water-cooled electrodes are arranged on the furnace door to supply power to the furnace door temperature zone.

[0010] Furthermore, both the furnace body and the furnace door need to adopt a double-layer water jacket structure, and a trapezoidal groove sealing structure is adopted between the furnace body and the furnace door.

[0011] Furthermore, the inner sleeves of the furnace body and the furnace door are made of stainless steel, and the outer sleeves are made of carbon steel.

[0012] Furthermore, the heating power of the furnace body is 200KW, and the hot pressing sintering pressure is 50T.

[0013] Furthermore, the two furnace bodies share a set of press, power supply, vacuum system and control system.

[0014] A batch hot pressing and sintering method for coated particle dispersion fuel pellets comprises the following steps:

[0015] Step 1: Use the mold to charge the material into the furnace;

[0016] Step 2: Vacuum and pre-press the mold: Turn on the pump group to vacuum, and when the pre-vacuum degree reaches below 20Pa, click the pressure head to rise to pre-press the mold;

[0017] Step 3: Clean the pipeline, open the valve on the gas charging pipeline to fill argon into the furnace, then close the gas charging valve to evacuate to below 20Pa, repeat this cycle 3 times, and close the valve on the gas charging pipeline;

[0018] Step 4: After cleaning the furnace body and pipes, turn on the pump set and pump down to below 5Pa;

[0019] Step 5: Set the sintering curve: temperature 1800-1950℃, holding time 2-3h, heating rate 10-15℃ / min, maximum pressure 20-25T, including 1400℃ holding time for 0.5h-1h, pressure increased to 14T at 0.1T / min, and the pressure was increased to the maximum pressure at a uniform rate during the subsequent process time;

[0020] Step 6: Click Process Run to start heating and pressurizing the sintering of the dispersed fuel pellets;

[0021] Step 7: After the insulation is completed, turn off the pump group, move the furnace body to the cooling station through the walking mechanism, and open the valve on the charging pipeline to fill the furnace body with helium at a helium flow rate of 1.5 to 5.0 L / min, so that the cooling time is controlled within 6 hours;

[0022] Step 8: The other furnace body can be loaded with materials in advance, and after the previous furnace body is moved out, it is moved to the press position and steps 1 to 7 are repeated for hot pressing and sintering.

[0023] Compared with the prior art, the apparatus and method for batch hot pressing and sintering of coated particle dispersion fuel pellets provided by the present invention have the following beneficial effects:

[0024] The device and method provided by the present invention can improve sintering efficiency and meet the needs of mass production of related fuels. The hot-pressing sintering device provided by the present invention utilizes a dual furnace body and a travel mechanism, and controls the cooling of the furnace body with a helium flow rate of 1.5 L / min. This shortens the cooling time to approximately 6 hours, matching the heating rate and hot-pressing holding time to approximately 6 hours.

[0025] Furthermore, the hot pressing sintering device provided by the present invention increases the furnace body size from the original Ф1.0m×1.5m to Ф1.5m×1.7m, and the heating power of the hot pressing sintering furnace is increased from the original 100KW to 200KW. The heating elements are evenly distributed around the inner furnace surface, and the temperature control is increased from the original 3 zones to 6 zones for zone heating, effectively ensuring the uniform distribution of the temperature field in the furnace, so that the uniform temperature zone is increased from the original Ф50×50mm to Ф350×350mm.

[0026] Furthermore, the hot pressing sintering device and method provided by the present invention increase the hot pressing sintering pressure from the original 25T to 50T, and the mold size from the original Ф50×50mm to Ф(200~350)×70mm; the number of mold layout layers is increased from the original single layer to 4 layers, and the charging amount is increased from the original 1~3 pieces per single furnace to 50~80 pieces.

[0027] The hot pressing and sintering device and method provided by the present invention can obtain dispersed fuel pellets with reliable quality, and the batch hot pressing efficiency of the coated particle dispersed fuel pellets is increased from the original 0.15 pellets / hour to 9 pellets / hour. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 A front view of a batch hot pressing and sintering apparatus for coated particle dispersion fuel pellets provided by an embodiment of the present invention;

[0030] Figure 2 A side view of a batch hot pressing and sintering apparatus for coated particle dispersion fuel pellets provided by an embodiment of the present invention;

[0031] Figure 3 A top view of a batch hot pressing and sintering apparatus for coated particle dispersion fuel pellets provided by an embodiment of the present invention;

[0032] Figure 4 A front view of a furnace body provided by an embodiment of the present invention;

[0033] Figure 5 A schematic structural diagram of a walking mechanism provided in an embodiment of the present invention;

[0034] Figure 6 A schematic structural diagram of a furnace door provided in an embodiment of the present invention;

[0035] Figure 7 A top view of a mold provided by an embodiment of the present invention;

[0036] Figure 8 A cross-sectional view of a mold provided in an embodiment of the present invention.

[0037] Description of reference numerals:

[0038] 1. First furnace body; 2. Second furnace body; 3. Traveling mechanism; 4. Mold; 5. Furnace door. DETAILED DESCRIPTION

[0039] The following is further explained in detail through specific implementation methods.

[0040] like Figures 1 to 8 As shown, the present invention provides a batch hot pressing sintering device for coated particle dispersion fuel pellets, which is mainly used for hot pressing sintering under high temperature and high pressure, including a furnace body, a furnace door, a heating body, upper and lower water-cooled pressure heads, a vacuum system, a press system and an electronic control system. The present invention has a double furnace structure, and a walking mechanism 3 is arranged at the bottom of each furnace body (such as Figure 5 As shown), the operation must be smooth through automatic program control, while the press remains stationary. After the hot pressing is completed, the furnace body is moved out through the walking mechanism 3 for cooling, removal from the furnace, and preparation for the next round of loading, while the other furnace body can be loaded with materials in advance, and after the previous furnace body is moved out, it moves to the press position for hot pressing and sintering.

[0041] The present invention sets two furnace bodies (a first furnace body 1 and a second furnace body 2) in the same hot pressing equipment, one furnace body is used for heating and pressurizing, and the other furnace body is used for cooling and lowering temperature. By matching the heating and cooling rates, the helium flow rate is controlled to (1.0-2.0) L / min, thereby shortening the cooling time of the cooling furnace body, making the hot pressing furnace body and the cooling furnace body time close, ensuring the connection between the two furnace bodies, further improving the preparation efficiency, achieving an effect close to continuous hot pressing, and meeting the batch production needs of relevant fuels.

[0042] The structures of the first furnace body 1 and the second furnace body 2 are exactly the same, and the furnace bodies are independent of each other and have no connection. After heating and heat preservation are completed, the vacuum connection pneumatic valve is closed and the pressurizing device is raised to release the pressure. The connection between the vacuum system and the furnace body is manually disassembled, and the traveling mechanism is used to move it to the cooling station for cooling. At this time, the other furnace body is moved to the heating station through the traveling mechanism, the vacuum system is manually connected, and the pressurizing device is lowered for pressure sintering. By optimizing and matching the sintering and cooling process parameters, the heating and cooling time are basically consistent on the basis of ensuring the performance of the pellets, and cyclic batch hot pressing sintering is realized to meet the needs of high-throughput preparation of coated particle dispersion fuel pellets. The second method is that there is no need to disassemble the vacuum system. The vacuum system is located in the middle of the two furnace bodies, and the two furnace bodies are evacuated at the same time. The furnace body and the vacuum system are separated by a valve.

[0043] Preferably, the double sets of furnace bodies share one set of press, one set of power supply, one set of vacuum system, and one set of control system. During the operation, the press does not move, while the furnace body moves, and the operation is stable and reliable.

[0044] like Figure 4 As shown, the furnace body includes a furnace shell, a furnace door 5, a furnace door locking mechanism, etc. The furnace shell is equipped with various side pipes for controlling thermocouples, infrared, water-cooled electrodes, vacuum gauges and other parts, and is also equipped with a backfill valve, a breaker valve, a mechanical safety valve, etc. The mechanical safety valve has the function of automatic unloading in case of overpressure in the furnace body.

[0045] like Figure 6 As shown, the furnace door 5 includes a furnace door inner tube, a furnace door flange, a furnace door inner plate, a furnace door outer tube, a furnace door outer plate, an electrode pipe, a vacuum observation window, a heat insulation screen seat, a furnace body water nozzle, a reinforcement tube, a plate, a lifting lug, a handle and a hexagonal bolt.

[0046] The vacuum system consists of a ZJ300 Roots vacuum pump, a 2X-70 rotary vane pump, vacuum piping, and other required vacuum components. The vacuum system is program-controlled to accurately sequence pump startup and valve opening and closing, and features comprehensive electrical interlock protection, overload, overtemperature, and water shortage protection, ensuring high reliability and safety.

[0047] The press is a double-beam, four-column design with a large work platform for placing the furnace body. To ensure the flatness of the upper and lower rams, the water-cooled metal rams on the furnace body are connected to the oil cylinder using flanges. The upper and lower graphite rams are made of high-isostatic graphite and connected to the water-cooled metal rams. They can be moved up and down for hot pressing, ensuring easy installation and disassembly.

[0048] The control system consists of a programmable controller PLC, temperature controller, touch screen, paperless recorder, thyristor voltage regulator, vacuum gauge, etc. to realize power supply, control, recording, monitoring, alarm protection functions.

[0049] Preferably, the furnace body adopts a vertical structure with a front door, the furnace body is fixed on the press platform, and the furnace door 5 is opened by manual pushing and pulling.

[0050] Preferably, copper water-cooled electrodes are provided on the furnace door to supply power to the temperature zone of the furnace door.

[0051] Preferably, the device is provided with a temperature measuring hole for temperature measurement by a photoelectric pyrometer.

[0052] Preferably, both the furnace body and furnace door should adopt a double-layer water jacket structure, with the inner jacket made of stainless steel and the outer jacket made of carbon steel. A trapezoidal groove sealing structure is used between the furnace body and the furnace door to ensure easy replacement of the sealing ring and the sealing performance of the vacuum furnace.

[0053] Preferably, the bottom of the furnace body is equipped with a travel drive, which is automatically controlled by a program to ensure smooth operation.

[0054] The present invention addresses the problem of low preparation throughput in a single furnace by increasing the size of the uniform temperature zone by matching and increasing the heating power, the pressure head area, the press pressure range, the size of the heating element, etc., and ultimately increasing the number of core blocks prepared in a single furnace by increasing the size of the mold 4 and the number of layers.

[0055] In order to increase the size of the uniform temperature zone and the pressing pressure, the size of the furnace body is increased from the original Ф1.0m×1.5m to Ф1.5m×1.7m; the heating elements are evenly distributed around the inner surface of the furnace body, and the temperature control is increased from the original 3 zones to 6 zones for zone heating, which effectively ensures the uniform distribution of the temperature field in the furnace; the heating power of the hot pressing sintering furnace is increased from the original 100KW to 200KW; the hot pressing sintering pressure is increased from the original 25T to 50T; due to the increase in the size of the uniform temperature zone, the size of the mold 4 can be increased from the original Ф50×50mm to Ф(200~350)×70mm (such as Figure 7 and Figure 8 The number of layers of the mold 4 is increased from the original single layer to 4 to 5 layers.

[0056] In addition, the present invention also provides a method for batch hot pressing and sintering of coated particle dispersion fuel pellets.

[0057] Step 1: Use optimized mold to load the material into the furnace;

[0058] Step 2: Vacuum and pre-press the mold: Turn on the pump group to vacuum, and when the pre-vacuum degree reaches below 20Pa, click the pressure head to rise to pre-press the mold;

[0059] Step 3: Clean the pipeline, open the valve on the gas charging pipeline to fill argon into the furnace, then close the gas charging valve and evacuate to below 20Pa, repeat this cycle 3 times, and close the valve on the gas charging pipeline;

[0060] Step 4: After cleaning the furnace body and pipes, turn on the pump set and pump down to below 5 Pa;

[0061] Step 5: Set the sintering curve: temperature (1800-1950°C), holding time (2-3) hours, heating rate (10-15)°C / min, maximum pressure (20-25)T, wherein the temperature is kept at 1400°C for 0.5-1 hour, and the pressure is increased to 14T at a rate of 0.1T / min. The pressure is then increased to the maximum pressure at a uniform rate during the subsequent process time.

[0062] Step 6: Click Process Run to start heating and pressurizing the sintering of the dispersed fuel pellets.

[0063] Step 7: After the insulation is completed, the pump group is turned off, the furnace body is moved to the cooling station through the walking mechanism 3, and the valve on the charging pipeline is opened to charge helium into the furnace body at a helium flow rate of 1.5 to 5.0 L / min, so that the cooling time is controlled within 6 hours;

[0064] In step 8, the other furnace body can be loaded with materials in advance, and after the previous furnace body is moved out, it is moved to the press position to repeat steps 1 to 7 for hot pressing and sintering.

[0065] Example

[0066] (1) By increasing the furnace size from the original 1.0m×1.5m to 1.5m×1.7m, the heating power of the hot pressing sintering furnace was increased from the original 100KW to 200KW, and the heating elements were evenly distributed around the inner furnace surface. The temperature control was increased from the original 3 zones to 6 zones, and the uniform temperature zone was increased from the original 50×50mm to 350×350mm.

[0067] (2) The hot pressing sintering pressure is increased from the original 25T to 50T, the outer diameter of the mold 4 is increased from the original Φ50mm to Φ200~300×70mm, and the number of single-layer core blocks is increased from the original 1 to 14. In addition, since the height of the uniform temperature zone is increased to 350mm, multiple layers of molds can be stacked. A 10mm thick graphite plate is added between the molds of different layers to ensure that the upper punch of the layer is flush with the graphite plate, preventing the occurrence of problems such as punch breakage or incomplete pressing due to unevenness of the upper punch during the hot pressing process. In this way, a maximum of 4 layers of molds can be loaded;

[0068] (3) The cooling of the furnace body was controlled by a helium flow rate of 1.5 L / min, shortening the cooling time to about 6 hours, and matching the heating rate and hot pressing holding time to about 6 hours.

[0069] (4) A double furnace body is set up through hot pressing equipment, wherein a walking mechanism 3 is configured at the bottom of the furnace body. Through automatic program control, it is necessary to ensure smooth operation while the press remains stationary. After the hot pressing is completed, the furnace body is moved out through the walking mechanism 3 for cooling, removal from the furnace, and preparation for the next round of loading, while the other furnace body can be loaded with materials in advance and moved to the press position for hot pressing and sintering after the previous furnace body is moved out.

[0070] (5) Use optimized mold Φ200×70mm to load the material into the furnace;

[0071] (6) Vacuuming and pre-pressing the mold: Turn on the pump group to vacuum, and when the pre-vacuum degree reaches below 20Pa, click the pressure head to rise to pre-press the mold;

[0072] (7) Clean the pipeline, open the valve on the gas charging pipeline to fill the furnace with argon, then close the gas charging valve and evacuate to below 20Pa, repeat this cycle 3 times, and close the valve on the gas charging pipeline;

[0073] (8) After cleaning the furnace body and pipelines, turn on the pump group and pump down to below 5Pa;

[0074] (9) Set the sintering curve: temperature is 1950℃, holding time is 3h, heating rate is 15℃ / min, maximum pressure is 25T, of which 1400℃ is held for 0.5h, and the pressure is increased to 14T at a rate of 0.1T / min. The pressure is increased to the maximum pressure at a uniform speed during the subsequent process time;

[0075] (10) Click Process Run to start heating and pressurizing the sintering of the dispersed fuel pellets;

[0076] (11) After the insulation is completed, the pump group is turned off, and the furnace body is moved to the cooling station through the walking mechanism 3. The valve on the charging pipeline is opened to fill the furnace body with helium at a helium flow rate of 3.0 L / min, so that the cooling time is controlled within 6 hours;

[0077] (12) The other furnace body can be loaded with materials in advance, and after the previous furnace body is moved out, it is moved to the press position to repeat the above (5) to (11) for hot pressing and sintering.

[0078] The present invention increases the size of the uniform temperature zone by matching and increasing the heating power, the pressure head area, the press pressure range, the size of the heating element, etc., and increases the number of core blocks prepared in a single furnace by increasing the mold size and placing the number of layers. At the same time, one furnace body is provided in the same hot pressing equipment for heating and pressurizing, and the other furnace body is provided for cooling. By matching the heating and cooling rates and adopting helium with an optimal flow rate for cooling, the cooling time of the cooling furnace body is shortened, so that the hot pressing furnace body and the cooling furnace body have similar time, ensuring alternating connection between the two furnace bodies, further improving the preparation efficiency, and achieving an effect close to continuous hot pressing. The hot pressing sintering efficiency is increased from the original 0.15 pieces / hour to 9 pieces / hour, meeting the needs of batch production of relevant fuels.

[0079] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention are intended to be covered by the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope of protection of the claims.

Claims

1. A batch hot pressing and sintering method for coated particle dispersion fuel pellets, characterized in that: A batch hot-pressing sintering device for coated particle dispersion fuel pellets is used. The device comprises two furnace bodies and a mold. Each furnace body is equipped with a running mechanism at the bottom, with one furnace body performing heating and pressurization while the other performs cooling. Heating elements are evenly distributed around the inner surface of the furnace body, and the furnace body is heated in six zones to achieve a uniform temperature distribution within the furnace chamber. The furnace body is a vertical structure fixed to a press platform, and copper water-cooled electrodes are arranged on the furnace door to power the door temperature zones. Both the furnace body and the furnace door are required to adopt a double-layer water jacket structure, and a trapezoidal groove sealing structure is used between the furnace body and the furnace door. The two furnace bodies share a press, power supply, vacuum system, and control system. The method comprises the following steps: Step 1: Use the mold to charge the material into the furnace; Step 2: Vacuum and pre-press the mold: Turn on the pump group to vacuum, and when the pre-vacuum degree reaches below 20Pa, click the pressure head to rise to pre-press the mold; Step 3: Clean the pipeline, open the valve on the gas charging pipeline to fill argon into the furnace, then close the gas charging valve to evacuate to below 20Pa, repeat this cycle 3 times, and close the valve on the gas charging pipeline; Step 4: After cleaning the furnace body and pipes, turn on the pump set and pump down to below 5Pa; Step 5: Set the sintering curve: temperature 1800~1950℃, holding time 2~3h, heating rate 10~15℃ / min, maximum pressure 20~25T, including 1400℃ holding time 0.5h~1h, pressure increased to 14T at 0.1T / min, and the pressure was increased to the maximum pressure at a uniform rate during the subsequent process time; Step 6: Click Process Run to start heating and pressurizing the sintering of the dispersed fuel pellets; Step 7: After the insulation is completed, turn off the pump group, move the furnace body to the cooling station through the walking mechanism, and open the valve on the charging pipeline to fill the furnace body with helium at a helium flow rate of 1.5~5.0L / min, so that the cooling time is controlled within 6 hours; Step 8: The other furnace body can be loaded with materials in advance, and after the previous furnace body is moved out, it is moved to the press position and steps 1 to 7 are repeated for hot pressing and sintering.

2. The method for batch hot pressing and sintering of coated particle dispersion fuel pellets according to claim 1, characterized in that: The inner sleeves of the furnace body and the furnace door are made of stainless steel, and the outer sleeves are made of carbon steel.

3. The method for batch hot pressing and sintering of coated particle dispersion fuel pellets according to claim 1, characterized in that: The heating power of the furnace body is 200KW, and the hot pressing sintering pressure is 50T.

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