CN112708749A - Equipment and method for continuous heat treatment of spherical fuel elements - Google Patents
Equipment and method for continuous heat treatment of spherical fuel elements Download PDFInfo
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- CN112708749A CN112708749A CN201911017516.6A CN201911017516A CN112708749A CN 112708749 A CN112708749 A CN 112708749A CN 201911017516 A CN201911017516 A CN 201911017516A CN 112708749 A CN112708749 A CN 112708749A
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
- C21D1/773—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material under reduced pressure or vacuum
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Abstract
The invention relates to equipment and a method for continuous heat treatment of spherical fuel elements, which comprises a furnace body, a heating and heat-preserving system, a temperature control system, a loading and unloading system, a vacuum system, a waste discharge system, a process gas circuit system, a pneumatic system, a waterway system, a tail gas combustion system and an electrical control system, and realizes the continuous heat treatment of low-temperature carbonization and high-temperature purification of the spherical fuel elements in the same equipment. The equipment and the method can be used for not only the continuous heat treatment of the green body of the spherical fuel element, but also the preparation of the matrix graphite nodule product, realize the continuous implementation of low-temperature carbonization and high-temperature purification in the same equipment, reduce the transportation of materials, shorten the heat treatment time of the spherical fuel element from about 90 hours which is originally separately implemented to about 50 hours of the continuous heat treatment, and improve the production efficiency by 44.4 percent.
Description
Technical Field
The invention relates to the technical field of nuclear fuel preparation, in particular to equipment and a method for continuous heat treatment of spherical fuel elements.
Background
In the prior art, the diameter of a spherical fuel element used by a ball-bed high-temperature gas cooled reactor in China is about 60mm, the whole spherical fuel element is a graphite matrix, the outer layer is a fuel-free area with the thickness of about 5mm, and the inner part is a fuel area which is about 50mm and contains 11000-12000 coated fuel particles (TRISO particles) with the diameter of about 1mm and is directly dispersed in the graphite matrix. The spherical fuel element after compression molding needs to be treated by carbonization and purification processes. And the carbonization treatment is that under the protection of argon, the mixture is heated to 800 ℃ under certain temperature rising condition, so that the adhesive is cracked and coked to form adhesive coke bridges, and the aggregate particles are firmly combined together. And the purification treatment is to place the carbonized spherical fuel element in a furnace body, heat the spherical fuel element to 1900 ℃ in vacuum and preserve the temperature for 1 hour to remove impurity elements in the spherical fuel element. The prior art can only meet the production requirements at the present stage, and has the problems of more material loading and unloading times, low energy utilization rate and the like because low-temperature carbonization and high-temperature purification are respectively carried out. With the development of various reactor types such as high-temperature reactor, molten salt reactor and the like, higher requirements are put forward on the production efficiency and cost of spherical fuel element preparation, a heat treatment link is taken as one of key production processes, and the treatment mode and the production efficiency are to be greatly improved. If a continuous heat treatment mode of direct purification without cooling after carbonization is adopted, the problems existing above can be effectively solved, but to realize the above idea, the problems of influence of material arrangement, temperature uniformity, conversion from positive pressure to negative pressure on equipment, selection of materials such as a heating body, a furnace lining and the like need to be overcome.
Therefore, there is a need to provide a continuous thermal treatment apparatus and method for spherical fuel elements, and particularly relates to a continuous thermal treatment of element green bodies in the manufacturing of spherical fuel elements of high temperature gas cooled reactors, so as to realize the continuous thermal treatment of low temperature carbonization and high temperature purification of spherical fuel elements in the same apparatus.
Disclosure of Invention
In view of the above, the present invention provides a continuous thermal processing apparatus and method for spherical fuel elements, which can be used for continuous thermal processing of spherical fuel elements, greatly improve the production efficiency of the thermal processing process for spherical fuel elements, reduce the energy consumption and the impact on materials caused by multiple loading and unloading in the thermal processing process for spherical fuel elements, and facilitate the improvement of the product performance of spherical fuel elements.
In order to solve the technical problems, the invention adopts the following technical scheme:
the equipment for continuous heat treatment of spherical fuel elements comprises a furnace body, a heating and heat-insulating system, a temperature control system, a loading and unloading system, a vacuum system, a waste discharge system, a process gas circuit system, a pneumatic system, a water circuit system, a tail gas combustion system and an electrical control system.
The furnace body comprises a furnace shell, a furnace door and a furnace shell base, wherein the furnace shell is of a horizontal double-layer structure, the furnace door is arranged in front of and behind the furnace shell, and a heat shielding door is arranged in the furnace door. The furnace body is a supporting main body of the equipment, and a thermocouple plugging mechanism, a temperature measuring device, an infrared thermometer measuring seat, a temperature uniformity testing seat, a pressure measuring device, an observation hole, an automatic exhaust valve, a mechanical balance valve and the like are arranged on the furnace body. The furnace door is hinged to open and close, and the front furnace door and the rear furnace door are locked by adopting a pneumatic driving mode, so that the operation is convenient. The furnace shell is provided with an automatic air release valve, a manual air release valve and a mechanical balance valve, so that the safe and reliable use of the equipment is ensured, and the furnace shell is sealed by a special rubber sealing ring with water cooling of the vacuum furnace.
The heating and heat-insulating system is arranged in the furnace shell and comprises a furnace liner, a heat-insulating layer and a heating body, wherein a heat-leakage-proof sealing layer is connected between the furnace door and the furnace liner in a stepped manner, the heat-insulating layer is arranged on the inner wall of the furnace liner, and the heating body is arranged in the heat-insulating layer. The anti-heat leakage sealing layer in stepped connection has good heat insulation performance and can realize quick cooling. The equipment introduces electric energy to a heating body in the furnace shell through a water-cooled electrode (T2 copper), and adopts a low-voltage and high-current mode to supply power, so that the equipment and the personal safety can be ensured, and the reliability is high.
The temperature control system comprises a thermocouple for measuring and controlling temperature at low temperature and an infrared thermometer for measuring and controlling temperature at high temperature, and the infrared thermometer and the thermocouple have the functions of automatic switching and mutual calibration of the measurement and control of temperature at high temperature and the measurement and control of temperature at low temperature. When the infrared thermometer measures that the high temperature is polluted, the online cleaning can be realized, so that the accuracy of temperature measurement at the high temperature is ensured. The system adopts sectional measurement, and adopts a tungsten-rhenium thermocouple to control the temperature at low temperature (less than 1200 ℃); and controlling the temperature at high temperature (more than or equal to 1200 ℃ C.) by using an infrared thermometer. And when the infrared thermometer and the thermocouple are switched to measure and control temperatures, the infrared thermometer and the thermocouple are calibrated with the measured and control temperatures, and the temperature points in the furnace corresponding to the infrared temperature measurement and the thermocouple temperature measurement are kept consistent during calibration. The infrared thermometer is provided with a ventilation device at the measuring position and is controlled to be opened and closed by a valve.
The loading and unloading system is arranged in the heating and heat-preserving system and comprises a muffle box and a material bearing plate, the muffle box is arranged in the heating element, the material bearing plate is provided with a spherical fuel element positioning hole, a graphite upright post supporting hole and a waste gas discharge hole, and the multilayer material bearing plate is separated by the graphite upright post and is placed in the muffle box. A plurality of spherical fuel elements can be placed on each layer of material bearing plate, and the positioning holes can prevent the spherical fuel elements from being adhered to each other in the low-temperature carbonization process. The waste gas discharge hole can ensure that the decomposition products and volatile matters in the purification process enter the tail gas combustion system from the only gas outlet at the bottom of the muffle box through the waste gas discharge hole in the heat treatment process, so that the aim of directional coke discharge is fulfilled. The graphite upright columns are arranged between the material bearing plates, so that the strength of the material bearing plates is ensured, and the phenomenon that the material bearing plates excessively deform or even collapse due to the weight of spherical fuel elements is avoided.
The vacuum system comprises a vacuum pump and a vacuumizing exhaust pipeline, and the vacuum pump is connected and communicated with the furnace shell through the vacuumizing exhaust pipeline. The vacuum system also comprises a vacuum pneumatic valve, a dust filter, a corrugated pipe, a vacuum gauge and the like. And a vacuum pneumatic valve is arranged on the vacuumizing exhaust pipeline and used for controlling the opening of a vacuum system. The system is controlled by the vacuum degree in the furnace and the heating and heat-preserving system in an interlocking way, and when the vacuum degree in the equipment does not meet the set requirement under the low-temperature condition, the heating and heat-preserving system cannot be started. And a quick vacuum leak detection interface is arranged on the vacuumizing exhaust pipeline and used for system leak detection.
The system of wasting discharge includes low temperature carbomorphism waste discharge pipeline and high temperature purification waste discharge pipeline, low temperature carbomorphism waste discharge pipeline includes pressure-fired exhaust duct and pressure-fired discharge valve, pressure-fired exhaust duct is connected with the bottom intercommunication of muffle tank through the bottom opening of stove outer covering, pressure-fired discharge valve sets up on pressure-fired exhaust duct, high temperature purification waste discharge pipeline includes vacuum pump and evacuation exhaust duct, the vacuum pump passes through evacuation exhaust duct with the stove outer covering and is connected the intercommunication. Organic products generated by decomposition of the phenolic resin in the low-temperature carbonization process need to be discharged in all directions, and no residual condensate exists in the furnace. The micro-positive pressure exhaust valve is arranged at the tail part of the micro-positive pressure exhaust pipeline, so that the precise adjustment and maintenance of the micro-positive pressure in the furnace can be realized.
The technology gas circuit system includes protection gas air inlet, admission valve, volumetric flowmeter, pressure-fired exhaust duct and pressure-fired discharge valve, the top at the stove outer covering is connected to protection gas air inlet intercommunication, set up admission valve and volumetric flowmeter on the protection gas air inlet, pressure-fired exhaust duct is connected with the bottom intercommunication of muffle box through the bottom opening of stove outer covering, pressure-fired discharge valve sets up on pressure-fired exhaust duct. The process gas circuit system can realize constant flow and constant pressure control in the furnace, namely, the flow of argon introduced into the furnace is set to be constant, the accurate control of the micro-positive pressure in the furnace is ensured by controlling the opening of the micro-positive pressure exhaust valve, the design that the argon enters the muffle box needs to realize directional coke discharge, and no accumulated liquid exists in the muffle box and the furnace. The device is provided with a furnace pressure detection device for monitoring the pressure in the furnace in real time, the furnace pressure is controlled by constant pressure under a constant flow condition, and when the pressure in the furnace is too large or too small, the constant pressure in the furnace is realized by adjusting the size of an exhaust port of a micro-positive pressure exhaust pipeline.
The pneumatic system comprises an air source triple piece, an electromagnetic directional valve and an air pipe. The pneumatic system provides power for the pneumatic actuating element of the equipment, and the equipment adopts the pneumatic control valve which is distributed in a distributed mode.
The waterway system is arranged in a horizontal double-layer structure of the furnace shell and adopts a closed water inlet and closed water return mode. The waterway system comprises a water inlet and outlet main pipe, a temperature-resistant pressure-resistant hose, a manual valve, a water pressure gauge, a water flow indicator, a temperature and flow sensor and the like. And a water return end of the water-cooled electrode adopts a temperature flow sensor, so that the water flow condition is monitored in real time, and the safety of equipment is ensured. The main water inlet pipeline is provided with pressure and temperature detection, water inlet pressure and water temperature detection, and water shortage and overtemperature alarm. When the cooling water flow and the pressure are low, alarming is carried out or the return water temperature is over-temperature, a certain early warning time is given, if the fault cannot be eliminated within the early warning time, the equipment executes protective measures, and the water inlet is automatically switched to emergency water inlet. The cooling circulating water system and the emergency water system are provided with electric or pneumatic three-way valves for water inlet and water return, when the flow rate of cooling water, the pressure is low, the alarm is performed or the temperature of the water return is over-temperature, the electric or pneumatic three-way valve of the water inlet branch can be automatically switched to the emergency water inlet, and the electric or pneumatic three-way valve of the water return branch can be automatically switched to the emergency water outlet. The water path system ensures that the surface temperature of the furnace shell does not exceed 60 ℃ when the temperature of the equipment is 1900 ℃ for heat preservation.
The tail gas combustion system is connected with the tail end of the micro-positive pressure exhaust pipeline and comprises a heating part and a compressed air supply gas circuit. The tail gas combustion system is also provided with a temperature control system, so that organic micromolecules generated in the low-temperature carbonization process can be fully oxidized in compressed air under different temperature conditions and converted into CO2And H2O。
The electrical control system comprises a programmable controller and an operation panel, and is used for controlling the electrical devices of the whole equipment. The operation panel is a touch screen operation system, and animation simulation display of the working state of the whole set of equipment and online control of each control system on the touch screen can be realized through the touch screen operation system. The related program control and temperature raising system can be set directly on the operation panel, and the experiment parameters and related data can be stored and read automatically. The electric control system is internally provided with a controlled system, a touch screen, related buttons and indicator lamps. An audible and visual alarm is arranged above the control cabinet, and the equipment sends audible and visual alarm signals when the equipment has over-temperature, over-pressure, insufficient vacuum degree and other faults.
Preferably, the heating body is high-purity isostatic graphite. The high-quality high-purity isostatic pressing graphite ensures uniform heating radiation.
Preferably, graphite cover plate seals are arranged on two sides of the muffle box. When loading, the material bearing plates are pulled out, after loading is completed, the material bearing plates can be pushed into the muffle box, and the multiple layers of material bearing plates are separated by the graphite upright posts. After the charging, the two sides of the muffle box are sealed by graphite cover plates.
Preferably, the ash content of the heating body, the muffle box and the material bearing plate is not higher than 100ppm, and the ash content of the heat insulation layer is not higher than 1000 ppm. The heating body, the muffle box and the material bearing plate are purified by introducing halogen elements at the temperature of over 2200 ℃, so that the pollution of the furnace to the nuclear pure-grade spherical fuel element in the heat treatment process is avoided.
Preferably, the infrared thermometer is of a fixed centering structure, the measurement is accurate, eccentricity is not prone to occurring, the optical temperature measuring window has an anti-pollution function, and the inner surface of the lens is provided with a cleaning device which can clean the surface of the lens on line in a high-temperature state.
Preferably, a cooling water jacket is arranged outside the micro-positive pressure exhaust pipeline, so that waste liquid generated in the carbonization process is condensed in the micro-positive pressure exhaust pipeline and collected at the bottom, and the effect of directional coke discharge in the furnace can be improved.
Preferably, the vacuum pump comprises a mechanical pump and a roots pump, a pressure difference valve is arranged in front of the vacuum pump, and when the vacuum pump is suddenly stopped, the oil of the vacuum pump is prevented from returning to the vacuum pumping exhaust pipeline.
The heat treatment method of the equipment for continuously heat treating the spherical fuel element comprises the steps of low-temperature carbonization and high-temperature purification of the spherical fuel element, wherein the processes of the low-temperature carbonization and the high-temperature purification are continuously carried out in the same equipment, and the heat treatment method comprises the following steps:
placing spherical fuel elements in positioning holes in a material bearing plate, placing the material bearing plate in a muffle box in multiple layers, closing a material loading and unloading system, closing a furnace door and a heat shield door, and opening a waterway system for cooling the surface of a furnace shell;
step two, starting a vacuum pump to vacuumize the furnace shell, then filling argon into a protective gas inlet to reach micro positive pressure, starting a heating body to heat, and carbonizing the spherical fuel element;
step three, heating the temperature from room temperature to 320 ℃, wherein the heating rate is not higher than 1 ℃/min, the temperature from 320 ℃ to 700 ℃, the heating rate is not higher than 0.6 ℃/min, the temperature from 700 ℃ to 800 ℃, the heating rate is not higher than 1.5 ℃/min, the temperature is kept for 1 hour at 800 ℃, in the carbonization treatment process, waste gas is discharged to a tail gas combustion system through a micro-positive pressure exhaust pipeline, and waste liquid is collected after being condensed in the micro-positive pressure exhaust pipeline;
closing the micro-positive pressure exhaust valve, sequentially starting a mechanical pump and a roots pump of the vacuum pump to continuously vacuumize the furnace, and continuously heating to purify the spherical fuel element;
fifthly, raising the temperature from 800 ℃ to 1500 ℃, raising the temperature at a rate of not higher than 5 ℃/min, raising the temperature from 1500 ℃ to 1700 ℃, raising the temperature at a rate of not higher than 3 ℃/min, raising the temperature from 1700 ℃ to 1900 ℃, raising the temperature at a rate of not higher than 1 ℃/min, preserving the temperature for 1 hour after the temperature reaches 1900 ℃, and starting cooling;
and step six, when the temperature is reduced to be lower than 1000 ℃, filling argon into the protective gas inlet, when the temperature is reduced to be lower than 600 ℃, opening the heat shielding door, when the temperature is reduced to be lower than 100 ℃, opening the furnace door, and after the temperature is reduced to be room temperature, opening the graphite cover plates at the two ends of the muffle box to take out the spherical fuel element.
Preferably, the atmosphere of the carbonization treatment in the third step is micro-positive pressure argon atmosphere, the constant current and the constant pressure are controlled, the flow rate of the argon is controlled to be 800L/min, the furnace pressure is 4-8kPa, and the carbonization treatment time is about 28 hours.
Preferably, the purification treatment of the fifth step is performed under vacuum atmosphere conditions.
The invention has the following beneficial effects:
by adopting the technical scheme, the invention not only can be used for the continuous heat treatment of the green body of the spherical fuel element, but also can be used for the preparation of the matrix graphite nodule product, realizes the continuous operation of low-temperature carbonization and high-temperature purification in the same equipment, reduces the material transportation, shortens the heat treatment time of the spherical fuel element from about 90 hours which is separately carried out to about 50 hours of the continuous heat treatment, and can improve the production efficiency by 44.4 percent.
The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical means of the present invention more clearly understood and to make the technical means implementable in accordance with the contents of the description, and to make the above and other objects, technical features, and advantages of the present invention more comprehensible, one or more preferred embodiments are described below in detail with reference to the accompanying drawings.
Drawings
One or more embodiments are illustrated by way of example in the accompanying drawings, which correspond to the figures in which like reference numerals refer to similar elements and which are not to scale unless otherwise specified.
Fig. 1 shows a schematic view of the structure of an apparatus for continuous heat treatment of spherical fuel elements of the present invention.
Description of the main reference numerals:
the method comprises the following steps of 1-furnace shell, 2-furnace container, 3-insulating layer, 4-heating body, 5-muffle box, 6-material bearing plate, 7-protective gas inlet, 8-micro-positive pressure exhaust pipeline, 9-micro-positive pressure exhaust valve, 10-tail gas combustion system, 11-vacuumizing exhaust pipeline, 12-vacuum pump and 13-furnace shell base.
Detailed Description
The following detailed description of the present invention is provided in conjunction with the accompanying drawings, but it should be understood that the scope of the present invention is not limited to the specific embodiments.
Throughout the specification and claims, unless explicitly stated otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element or component but not the exclusion of any other element or component.
Spatially relative terms, such as "below," "lower," "upper," "above," "upper," and the like, may be used herein for ease of description to describe one element or feature's relationship to another element or feature in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the object in use or operation in addition to the orientation depicted in the figures. For example, if the items in the figures are turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the elements or features. Thus, the exemplary term "below" can encompass both an orientation of below and above. The article may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative terms used herein should be interpreted accordingly.
As shown in fig. 1, a continuous heat treatment device for spherical fuel elements comprises a furnace body, a heating and heat-preserving system, a temperature control system, a loading and unloading system, a vacuum system, a waste discharge system, a process gas circuit system, a pneumatic system, a water circuit system, a tail gas combustion system 10 and an electrical control system.
The furnace body comprises a furnace shell 1, a furnace door and a furnace shell base 13, wherein the furnace shell 1 is of a horizontal double-layer structure, the furnace door is arranged in front of and behind the furnace shell 1, and a heat shielding door is arranged in the furnace door. The furnace body is a supporting main body of the equipment, and a thermocouple plugging mechanism, a temperature measuring device, an infrared thermometer measuring seat, a temperature uniformity testing seat, a pressure measuring device, an observation hole, an automatic exhaust valve, a mechanical balance valve and the like are arranged on the furnace body. The furnace door is hinged to open and close, and the front furnace door and the rear furnace door are locked by adopting a pneumatic driving mode, so that the operation is convenient. The furnace shell 1 is provided with an automatic air release valve, a manual air release valve and a mechanical balance valve, so that the safe and reliable use of the equipment is ensured, and the furnace shell 1 is sealed by a special rubber sealing ring with water cooling of the vacuum furnace.
The heating heat preservation system sets up in stove outer covering 1, the heating heat preservation system is used for the heating of starting equipment and the maintenance of temperature, the heating heat preservation system includes stove courage 2, heat preservation 3 and heat-generating body 4, cascaded heat-leak protection sealing layer that is connected with between furnace gate and the stove courage 2, heat preservation 3 sets up the inner wall at stove courage 2, heat-generating body 4 sets up in heat preservation 3. The anti-heat leakage sealing layer in stepped connection has good heat insulation performance and can realize quick cooling. The equipment introduces electric energy to the heating body 4 in the furnace shell 1 through a water-cooled electrode (T2 copper), and adopts a low-voltage and high-current mode to supply power, thereby ensuring the safety of the equipment and the human body and having high reliability. The heating body 4 is high-purity isostatic pressing graphite. The high-quality high-purity isostatic pressing graphite ensures uniform heating radiation.
The temperature control system comprises a thermocouple for measuring and controlling temperature at low temperature and an infrared thermometer for measuring and controlling temperature at high temperature, and the infrared thermometer and the thermocouple have the functions of automatic switching and mutual calibration of the measurement and control of temperature at high temperature and the measurement and control of temperature at low temperature. The temperature control system is used for accurately controlling the temperature rise rate and the target temperature of the equipment. When the infrared thermometer measures that the high temperature is polluted, the online cleaning can be realized, so that the accuracy of temperature measurement at the high temperature is ensured. The system adopts sectional measurement, and adopts a tungsten-rhenium thermocouple to control the temperature at low temperature (less than 1200 ℃); and controlling the temperature at high temperature (more than or equal to 1200 ℃ C.) by using an infrared thermometer. And when the infrared thermometer and the thermocouple are switched to measure and control temperatures, the infrared thermometer and the thermocouple are calibrated with the measured and control temperatures, and the temperature points in the furnace corresponding to the infrared temperature measurement and the thermocouple temperature measurement are kept consistent during calibration. The infrared thermometer is provided with a ventilation device at the measuring position and is controlled to be opened and closed by a valve. The infrared thermometer is of a fixed centering structure, is accurate in measurement and not prone to eccentricity, the optical temperature measurement window has an anti-pollution function, and the inner surface of the lens is provided with a cleaning device which can clean the surface of the lens on line in a high-temperature state.
The loading and unloading system is arranged in the heating and heat-preserving system and comprises a muffle box 5 and a material bearing plate 6, the muffle box 5 is arranged in the heating body 4, the material bearing plate 6 is provided with a spherical fuel element positioning hole, a graphite upright post supporting hole and a waste gas discharge hole, and the multilayer material bearing plate 6 is separated by the graphite upright post and is placed in the muffle box 5. A plurality of spherical fuel elements can be placed on each layer of the material bearing plate 6, and the positioning holes can prevent the spherical fuel elements from being adhered to each other in the low-temperature carbonization process. The waste gas discharge hole can ensure that the decomposed products and volatile matters in the purification process enter the tail gas combustion system 10 from the only gas outlet at the bottom of the muffle box 5 through the waste gas discharge hole in the heat treatment process, so that the aim of directional coke discharge is fulfilled. The graphite upright posts are arranged between the material bearing plates 6, so that the strength of the material bearing plates 6 is ensured, and the phenomenon that the material bearing plates 6 excessively deform or even collapse due to the weight of spherical fuel elements is avoided. And graphite cover plates are arranged on two sides of the muffle box 5 for sealing. When loading, the material bearing plate 6 is pulled out, and after loading is completed, the material bearing plate 6 can be pushed into the muffle box 5. After the charging, the two sides of the muffle box 5 are sealed by graphite cover plates.
The ash content of the heating body 4, the muffle box 5 and the material bearing plate 6 is not higher than 100ppm, and the ash content of the heat insulation layer 3 is not higher than 1000 ppm. The heating body 4, the muffle box 5 and the material bearing plate 6 are purified by introducing halogen elements at the temperature of more than 2200 ℃, so that the pollution of the furnace to the nuclear pure-grade spherical fuel element in the heat treatment process is avoided.
The vacuum system comprises a vacuum pump 12 and a vacuumizing exhaust pipeline 11, wherein the vacuum pump 12 is connected and communicated with the furnace shell 1 through the vacuumizing exhaust pipeline 11. The vacuum pump 12 comprises a mechanical pump and a roots pump, a pressure difference valve is arranged in front of the vacuum pump 12, and when the vacuum pump 12 is suddenly stopped, the oil of the vacuum pump is prevented from returning to the vacuumizing exhaust pipeline 11. The vacuum system also comprises a vacuum pneumatic valve, a dust filter, a corrugated pipe, a vacuum gauge and the like. And a vacuum pneumatic valve is arranged on the vacuumizing exhaust pipeline 11 and used for controlling the opening of a vacuum system. The system is controlled by the vacuum degree in the furnace and the heating and heat-preserving system in an interlocking way, and when the vacuum degree in the equipment does not meet the set requirement under the low-temperature condition, the heating and heat-preserving system cannot be started. And a quick vacuum leak detection interface is arranged on the vacuumizing exhaust pipeline 11 and used for system leak detection.
The waste discharge system comprises a low-temperature carbonization waste discharge pipeline and a high-temperature purification waste discharge pipeline, the low-temperature carbonization waste discharge pipeline comprises a micro-positive pressure exhaust pipeline 8 and a micro-positive pressure exhaust valve 9, the micro-positive pressure exhaust pipeline 8 is communicated with the bottom of the muffle box 5 through an opening at the bottom of the furnace shell 1, the micro-positive pressure exhaust valve 9 is arranged on the micro-positive pressure exhaust pipeline 8, a cooling water jacket is arranged outside the micro-positive pressure exhaust pipeline 8, so that waste liquid generated in the carbonization process is condensed in the micro-positive pressure exhaust pipeline and collected at the bottom, and the effect of directional coke discharge in the furnace can be improved.
The high-temperature purification waste discharge pipeline comprises a vacuum pump 12 and a vacuumizing exhaust pipeline 11, wherein the vacuum pump 12 is connected and communicated with the furnace shell 1 through the vacuumizing exhaust pipeline 11. The tail gas in the low-temperature carbonization waste discharge pipeline is prevented from being condensed and blocked, so that the tail gas is butted with a subsequent tail gas combustion system 10. Organic products generated by decomposition of the phenolic resin in the low-temperature carbonization process need to be discharged in all directions, and no residual condensate exists in the furnace. The micro-positive pressure exhaust valve 9 is arranged at the tail part of the micro-positive pressure exhaust pipeline 8, so that the micro-positive pressure in the furnace can be accurately adjusted.
The technology gas circuit system includes protection gas air inlet 7, admission valve, volumetric flowmeter, pressure-fired exhaust duct 8 and pressure-fired discharge valve 9, 7 intercommunication connections of protection gas air inlet are at the top of stove outer covering 1, set up admission valve and volumetric flowmeter on the protection gas air inlet 7, pressure-fired exhaust duct 8 is connected through the bottom opening of stove outer covering 1 and the bottom intercommunication of muffle box 5, pressure-fired discharge valve 9 sets up on pressure-fired exhaust duct 8. The process gas circuit system can realize constant flow and constant pressure control in the furnace, namely, the flow of argon introduced into the furnace is set to be constant, the accurate control of the micro-positive pressure in the furnace is ensured by controlling the opening of the micro-positive pressure exhaust valve 9, the design that the argon enters the muffle box 5 needs to realize directional coke discharge, and no accumulated liquid exists in the muffle box 5 and the furnace pipe 2. The pressure in the furnace is detected and monitored in real time, the pressure in the furnace is controlled by constant pressure under the condition of constant flow, and when the pressure in the furnace is too large or too small, the constant pressure in the furnace is realized by adjusting the size of an exhaust port of the micro-positive pressure exhaust pipeline 8.
The process gas circuit system and the vacuum system are used for creating an atmosphere environment meeting the process requirements.
The pneumatic system comprises an air source triple piece, an electromagnetic directional valve and an air pipe. The pneumatic system provides power for the pneumatic actuating element of the equipment, and the equipment adopts the pneumatic control valve which is distributed in a distributed mode.
The water path system is used for cooling the surface of equipment, is arranged in a horizontal double-layer structure of the furnace shell 1 and adopts a closed water inlet and return mode. The waterway system comprises a water inlet and outlet main pipe, a temperature-resistant pressure-resistant hose, a manual valve, a water pressure gauge, a water flow indicator, a temperature and flow sensor and the like. And a water return end of the water-cooled electrode adopts a temperature flow sensor, so that the water flow condition is monitored in real time, and the safety of equipment is ensured. The main water inlet pipeline is provided with pressure and temperature detection, water inlet pressure and water temperature detection, and water shortage and overtemperature alarm. When the cooling water flow and the pressure are low, alarming is carried out or the return water temperature is over-temperature, a certain early warning time is given, if the fault cannot be eliminated within the early warning time, the equipment executes protective measures, and the water inlet is automatically switched to emergency water inlet. The cooling circulating water system and the emergency water system are provided with electric or pneumatic three-way valves for water inlet and water return, when the flow rate of cooling water, the pressure is low, the alarm is performed or the temperature of the water return is over-temperature, the electric or pneumatic three-way valve of the water inlet branch can be automatically switched to the emergency water inlet, and the electric or pneumatic three-way valve of the water return branch can be automatically switched to the emergency water outlet. The water path system ensures that the surface temperature of the furnace shell 1 does not exceed 60 ℃ when the temperature of the equipment is kept at 1900 ℃.
The tail gas combustion system 10 is connected with the tail end of the micro-positive pressure exhaust pipeline 8, and the tail gas combustion system 10 comprises a heating part and a compressed air supply air path. The tail gas combustion system 10 is also provided with a temperature control system, so that organic small molecules generated in the low-temperature carbonization process can be fully oxidized in compressed air under different temperature conditions and converted into CO2And H2O。
The electric control system comprises a programmable controller and an operation panel, and is used for controlling the electric device of the whole equipment, and comprises a touch screen, a thermocouple, an air passage and water passage valve body, a pump body and the like. The operation panel is a touch screen operation system, and animation simulation display of the working state of the whole set of equipment and online control of each control system on the touch screen can be realized through the touch screen operation system. The related program control and temperature raising system can be set directly on the operation panel, and the experiment parameters and related data can be stored and read automatically. The electric control system is internally provided with a controlled system, a touch screen, related buttons and indicator lamps. An audible and visual alarm is arranged above the control cabinet, and the equipment sends audible and visual alarm signals when the equipment has over-temperature, over-pressure, insufficient vacuum degree and other faults.
The heat treatment method of the equipment for continuously heat treating the spherical fuel element comprises the steps of low-temperature carbonization and high-temperature purification of the spherical fuel element, wherein the processes of the low-temperature carbonization and the high-temperature purification are continuously carried out in the same equipment, and the heat treatment method comprises the following steps:
placing 200 spherical fuel elements in positioning holes in a material bearing plate 6, placing the material bearing plate 6 in a muffle box 5 in a multi-layer mode, closing a material loading and unloading system, closing a furnace door and a heat shield door, and opening a waterway system for cooling the surface of a furnace shell 1;
step two, starting a vacuum pump 12 to vacuumize the furnace shell 1, then filling argon into a protective gas inlet 7 to reach micro positive pressure, starting a heating body 4 to heat and raise the temperature, and carbonizing the spherical fuel element;
step three, heating the temperature from room temperature to 320 ℃, wherein the heating rate is not higher than 1 ℃/min, the temperature from 320 ℃ to 700 ℃, the heating rate is not higher than 0.6 ℃/min, the temperature from 700 ℃ to 800 ℃, the heating rate is not higher than 1.5 ℃/min, the temperature is kept for 1 hour at 800 ℃, in the carbonization treatment process, waste gas is discharged to a tail gas combustion system 10 through a micro-positive pressure exhaust pipeline 8, and waste liquid is collected after being condensed in the micro-positive pressure exhaust pipeline 8; the carbonization treatment atmosphere is micro-positive pressure argon atmosphere, constant current and constant pressure control is carried out, the flow of the argon is controlled to be 800L/min, the furnace pressure is 4-8kPa, and the carbonization treatment time is about 28 hours;
step four, closing the micro-positive pressure exhaust valve 9, sequentially starting a mechanical pump and a roots pump of the vacuum pump 12 to continuously vacuumize the furnace, and continuously heating to purify the spherical fuel element;
and step five, raising the temperature from 800 ℃ to 1500 ℃, raising the temperature at a rate of not higher than 5 ℃/min, raising the temperature from 1500 ℃ to 1700 ℃, raising the temperature at a rate of not higher than 3 ℃/min, raising the temperature from 1700 ℃ to 1900 ℃, raising the temperature at a rate of not higher than 1 ℃/min, preserving the temperature for 1 hour after the temperature reaches 1900 ℃, starting cooling, and carrying out purification treatment under the condition of vacuum atmosphere.
And step six, when the temperature is reduced to be lower than 1000 ℃, argon is filled into the protective gas inlet 7, when the temperature is reduced to be lower than 600 ℃, the heat shielding door is opened, when the temperature is reduced to be lower than 100 ℃, the furnace door is opened, after the temperature is reduced to be room temperature, the graphite cover plates at two ends of the muffle box 5 are opened, and the spherical fuel element is taken out.
The continuous heat treatment time for the whole carbonization and purification is about 40 hours, and the time required by temperature reduction is about 50 hours. No macroscopic condensate exists in the furnace shell 1, and organic matters generated in the decomposition process of the phenolic resin are condensed and collected by directional coke discharge and discharged from equipment and enter a tail gas combustion system 10 for oxidation treatment.
By using the continuous heat treatment equipment and the continuous heat treatment method for the spherical fuel element, disclosed by the invention, various performance indexes of the spherical fuel element obtained after carbonization and purification continuous heat treatment are tested, and all the performance indexes meet the technical requirements as shown in the following table 1.
TABLE 1 Performance index for spherical Fuel elements produced by continuous Heat treatment apparatus and method
| Performance index | Technical requirements | Measured value |
| Density (g/cm)3) | 1.70-1.77 | 1.74 |
| Thermal conductivity (1000 ℃, W/mK) | ≥25.0 | 33.4 |
| Anisotropy (20-500 ℃ C.) | ≤1.3 | 1.16 |
| Crush strength (kN)a | ≥18.0 | 24.6/21.8 |
| Number of ball falling | ≥50 | ≥50 |
| Wear Rate (mg/h) | ≤6.0 | 1.48 |
| Corrosion rate (mg/cm)2h)b | ≤1.3 | 0.75 |
aParallel and perpendicular to the pressing direction;
bthe corrosion temperature and the corrosion time are respectively 10H at 1000 ℃ and He +1 vol% H2O。
The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. It is not intended to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and its practical application to enable one skilled in the art to make and use various exemplary embodiments of the invention and various alternatives and modifications as are suited to the particular use contemplated. Any simple modifications, equivalent changes and modifications made to the above exemplary embodiments shall fall within the scope of the present invention.
Claims (10)
1. The equipment for continuous heat treatment of the spherical fuel elements is characterized by comprising a furnace body, a heating and heat-preserving system, a temperature control system, a loading and unloading system, a vacuum system, a waste discharge system, a process gas circuit system, a pneumatic system, a waterway system, a tail gas combustion system (10) and an electrical control system;
the furnace body comprises a furnace shell (1), a furnace door and a furnace shell base (13), the furnace shell (1) is of a horizontal double-layer structure, the furnace door is arranged in front of and behind the furnace shell (1), and a heat shielding door is arranged in the furnace door;
the heating and heat-insulating system is arranged in the furnace shell (1), the heating and heat-insulating system comprises a furnace pipe (2), a heat-insulating layer (3) and a heating body (4), a heat-leakage-proof sealing layer is connected between the furnace door and the furnace pipe (2) in a stepped manner, the heat-insulating layer (3) is arranged on the inner wall of the furnace pipe (2), and the heating body (4) is arranged in the heat-insulating layer (3);
the temperature control system comprises a thermocouple for measuring and controlling temperature at low temperature and an infrared thermometer for measuring and controlling temperature at high temperature, and the infrared thermometer and the thermocouple have the functions of automatic switching and mutual calibration of the measurement and control of temperature at high temperature and the measurement and control of temperature at low temperature;
the loading and unloading system is arranged in the heating and heat-preserving system and comprises a muffle box (5) and a material bearing plate (6), the muffle box (5) is arranged in the heating body (4), the material bearing plate (6) is provided with a spherical fuel element positioning hole, a graphite upright post supporting hole and a waste gas discharge hole, and the multilayer material bearing plate (6) is separately placed in the muffle box (5) through graphite upright posts;
the vacuum system comprises a vacuum pump (12) and a vacuumizing exhaust pipeline (11), and the vacuum pump (12) is connected and communicated with the furnace shell (1) through the vacuumizing exhaust pipeline (11);
the waste discharge system comprises a low-temperature carbonization waste discharge pipeline and a high-temperature purification waste discharge pipeline, the low-temperature carbonization waste discharge pipeline comprises a micro-positive pressure exhaust pipeline (8) and a micro-positive pressure exhaust valve (9), the micro-positive pressure exhaust pipeline (8) is communicated and connected with the bottom of a muffle box (5) through a bottom opening of a furnace shell (1), the micro-positive pressure exhaust valve (9) is arranged on the micro-positive pressure exhaust pipeline (8), the high-temperature purification waste discharge pipeline comprises a vacuum pump (12) and a vacuumizing exhaust pipeline (11), and the vacuum pump (12) is communicated with the furnace shell (1) through the vacuumizing exhaust pipeline (11);
the process gas path system comprises a protective gas inlet (7), a gas inlet valve, a volume flow meter, a micro-positive pressure exhaust pipeline (8) and a micro-positive pressure exhaust valve (9), wherein the protective gas inlet (7) is communicated and connected with the top of the furnace shell (1), the gas inlet valve and the volume flow meter are arranged on the protective gas inlet (7), the micro-positive pressure exhaust pipeline (8) is communicated and connected with the bottom of the muffle box (5) through the bottom opening of the furnace shell (1), and the micro-positive pressure exhaust valve (9) is arranged on the micro-positive pressure exhaust pipeline (8);
the pneumatic system comprises an air source triple piece, an electromagnetic directional valve and an air pipe;
the waterway system is arranged in a horizontal double-layer structure of the furnace shell (1), and the waterway system adopts a closed water inlet and closed water return mode;
the tail gas combustion system (10) is connected with the tail end of the micro-positive pressure exhaust pipeline (8), and the tail gas combustion system (10) comprises a heating part and a compressed air supply gas circuit;
the electrical control system comprises a programmable controller and an operation panel, and is used for controlling the electrical devices of the whole equipment.
2. The apparatus for continuous heat treatment of spherical fuel elements according to claim 1, wherein said heat-generating body (4) is high-purity isostatic graphite.
3. An apparatus for the continuous thermal treatment of spherical fuel elements according to claim 1, characterized in that the muffle (5) is provided with graphite cover plate seals on both sides.
4. The apparatus for continuous heat treatment of spherical fuel elements according to claim 1, wherein the ash content of the heating body (4), the muffle box (5) and the material-receiving plate (6) is not higher than 100ppm, and the ash content of the heat-insulating layer (3) is not higher than 1000 ppm.
5. An apparatus for the continuous heat treatment of spherical fuel elements according to claim 1, wherein the infrared thermometers are of fixed centering construction.
6. An apparatus for continuous thermal treatment of spherical fuel elements according to claim 1, characterized in that said micro-positive pressure exhaust duct (8) is externally provided with a cooling water jacket.
7. The apparatus for the continuous thermal treatment of spherical fuel elements according to claim 1, characterized in that said vacuum pump (12) comprises a mechanical pump and a roots pump, said vacuum pump (12) being preceded by a differential pressure valve.
8. A heat treatment method using the apparatus for continuous heat treatment of spherical fuel elements according to any of claims 1 to 7, wherein the heat treatment method comprises low-temperature carbonization and high-temperature purification of the spherical fuel elements, and the processes of low-temperature carbonization and high-temperature purification are continuously performed in the same apparatus, and the heat treatment method comprises the steps of:
placing spherical fuel elements in positioning holes in a material bearing plate (6), placing the material bearing plate (6) in a muffle box (5) in a multi-layer mode, closing a material loading and unloading system, closing a furnace door and a heat shield door, and opening a water path system for cooling the surface of a furnace shell (1);
step two, starting a vacuum pump (12) to vacuumize the furnace shell (1), then filling argon into a protective gas inlet (7) to a micro positive pressure, starting a heating body (4) to heat and raise the temperature, and carbonizing the spherical fuel element;
step three, heating the temperature from room temperature to 320 ℃, wherein the heating rate is not higher than 1 ℃/min, the temperature from 320 ℃ to 700 ℃, the heating rate is not higher than 0.6 ℃/min, the temperature from 700 ℃ to 800 ℃, the heating rate is not higher than 1.5 ℃/min, the temperature is kept for 1 hour at 800 ℃, in the carbonization treatment process, waste gas is discharged to a tail gas combustion system (10) through a micro-positive pressure exhaust pipeline (8), and waste liquid is collected after being condensed in the micro-positive pressure exhaust pipeline (8);
step four, closing the micro-positive pressure exhaust valve (9), sequentially starting a mechanical pump and a roots pump of the vacuum pump (12) to continuously vacuumize the furnace, and continuously heating to purify the spherical fuel element;
fifthly, raising the temperature from 800 ℃ to 1500 ℃, raising the temperature at a rate of not higher than 5 ℃/min, raising the temperature from 1500 ℃ to 1700 ℃, raising the temperature at a rate of not higher than 3 ℃/min, raising the temperature from 1700 ℃ to 1900 ℃, raising the temperature at a rate of not higher than 1 ℃/min, preserving the temperature for 1 hour after the temperature reaches 1900 ℃, and starting cooling;
and sixthly, when the temperature is reduced to be lower than 1000 ℃, argon is filled into the protective gas inlet (7), when the temperature is reduced to be lower than 600 ℃, the heat shielding door is opened, when the temperature is reduced to be lower than 100 ℃, the door is opened, and after the temperature is reduced to be room temperature, the graphite cover plates at the two ends of the muffle box (5) are opened to take out the spherical fuel element.
9. The heat treatment method for the equipment for continuously heat treating the spherical fuel element as claimed in claim 8, wherein the carbonization treatment atmosphere in the third step is a micro-positive pressure argon atmosphere, the constant current and the constant pressure are controlled, the argon flow is controlled to be 800L/min, the furnace pressure is 4-8kPa, and the carbonization treatment time is about 28 hours.
10. The heat treatment method of an apparatus for continuously heat-treating spherical fuel elements according to claim 8, wherein the purification treatment of the fifth step is performed under vacuum atmosphere conditions.
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| CN111868275A (en) * | 2018-03-16 | 2020-10-30 | 捷客斯金属株式会社 | Method for treating waste materials of electronic and electrical equipment parts |
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| CN101655310A (en) * | 2009-09-18 | 2010-02-24 | 沈阳恒进真空科技有限公司 | Protective atmosphere vacuum sintering furnace with high temperature of 1800 DEG C |
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| CN107436088A (en) * | 2017-08-16 | 2017-12-05 | 苏州楚翰真空科技有限公司 | A kind of horizontal-type high temperature vacuum experiment stove |
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