Method for preparing powder from artificial graphite powder for high-temperature gas cooled reactor nuclear fuel element
Technical Field
The invention relates to the technical field of artificial graphite production, in particular to a method for preparing powder from artificial graphite powder for a high-temperature gas cooled reactor nuclear fuel element.
Background
The production method of the high-temperature gas-cooled reactor nuclear fuel element comprises the following steps: the fuel uranium is coated by silicon carbide (about 1 mm), and is uniformly dispersed in a graphite matrix to prepare graphite nodules with the diameter of 60mm, which are called nuclear fuel elements; the graphite base material is mainly formed by bonding artificial graphite powder and natural graphite powder through phenolic aldehyde data, and in the nuclear fuel element, the weight ratio of the graphite base material reaches more than 90 percent, and the graphite base material is one of core materials in the production and manufacturing process of the nuclear fuel element; since any material entering a nuclear reactor has very severe conditions, the strength and wear resistance of the nuclear fuel element are strictly required.
The Chinese patent application numbers are: 2016104144468 discloses a method for preparing artificial graphite powder for high temperature gas cooled reactor nuclear fuel element and graphite powder, the method includes mixing, isostatic pressing, densification, grinding, shaping and grading, graphitization and high temperature purification, when the graphite powder prepared by the method is used in nuclear fuel element process test, because the graphite powder is round or oval, and the particle size distribution is reasonable, the nuclear fuel element formed by pressing has no holes formed inside due to bridging, the density of fuel particles is large, the strength is high, the stability is good, and the service life in the reactor is long.
In the technical scheme, the raw materials are coarsely crushed, ground into powder by an airflow mill and then shaped; the obtained powder particle size is uncontrollable, and the powder is milled through the jet mill and then shaped through the shaping machine, as is well known, the friction between the powder and the setting exists in the shaping process, and the abrasion is uncontrollable, so that the indexes of the powder subjected to the jet mill and the powder subjected to shaping are different and are difficult to control, and the production of high-standard nuclear fuel elements is difficult to meet.
Disclosure of Invention
The invention aims to provide a method for preparing powder of artificial graphite powder for a high-temperature gas-cooled reactor nuclear fuel element, aiming at the defects of the prior art, the method realizes the accurate control of powder indexes by integrating the fine grinding and shaping of powder and combining the frequency control of a main machine, a fan and a grader of raw materials in the coarse grinding and fine grinding and shaping processes, and solves the technical problem that the batch production of high-standard nuclear fuel elements is difficult to realize due to the fact that the powder indexes of artificial graphite powder cannot be accurately controlled in the prior art.
In order to solve the technical problem, the invention provides a method for preparing powder from artificial graphite powder for a high-temperature gas cooled reactor nuclear fuel element, which is characterized by comprising the following steps of:
(a) primary crushing, namely putting the artificial graphite powder raw material into a jaw crusher, and crushing to obtain raw material particles with the particle size of less than 20 mm;
(b) coarse grinding, namely conveying the raw material particles obtained in the step (a) into a 3R Raymond mill for grinding and crushing, and controlling the operating frequency of an upper fan a and a classifier a of the 3R Raymond mill to obtain powder particles with the particle size of 150-;
(c) fine grinding and shaping, namely feeding the powder particles obtained in the step (b) into a mechanical grinding machine, wherein the mechanical grinding machine comprises a main machine, the main machine comprises a fine grinding bin and a rotary table rotationally arranged in the fine grinding bin, the fine grinding treatment and primary shaping are carried out on the powder particles in a relative rotational friction mode through the rotary table and a gear ring on the main machine in the mechanical grinding machine, and secondary shaping of the powder is realized through collision of a plurality of hammers arranged on the rotary table and the powder particles, so that the obtained powder has the particle size of 32-100 mu m and the appearance is in a sphere-like shape; and simultaneously controlling the frequency of the fan to ensure that the powder after the secondary shaping is screened and output by a classifier under the action of ascending airflow generated by the powder to obtain powder with a standard index, wherein the particle size of the powder with the standard index is 32-100 mu m, the 18-30 hammer heads are uniformly distributed around the axis of the turntable, and the protrusions are arranged on the upper surface of the turntable.
The rotary disc throws the powder particles falling on the rotary disc out of a grinding area between the rotary disc and the gear ring in a rotating centrifugal mode, and in the process that the powder particles move to the grinding area while being finely ground through the relative motion of the rotary disc and the gear ring, the powder particles are in contact with the gear ring in an impact mode, so that the primary shaping of the gear ring on the powder particles is realized.
In addition, the powder particles are finely ground into powder through the rotary disc and the gear ring, and the powder is subjected to secondary shaping by the hammer head in a collision mode in the process that the powder is driven by vortex airflow formed by the rotation of the hammer head driven by the rotary disc to pass through the motion track of the hammer head and move from outside to inside.
Specifically, after the powder is shaped in the second stage, the powder in the vortex airflow is absorbed and moved upwards by the ascending airflow formed by the fan in a negative pressure absorption mode, and the powder is filtered and screened by the classifier and then is driven to be output by the ascending airflow.
The improvement comprises two-stage grinding, wherein the powder is filtered and screened by a classifier to form fine powder and coarse powder, and the fine powder is driven by an ascending air flow to pass through the classifier and then is output; the coarse powder material is separated from the fine powder material by a classifier in a rotating mode and then falls freely, and is contacted with powder particles thrown out by a turntable in a centrifugal mode, and the powder particles are driven to enter a milling area for secondary milling.
As an improvement, the artificial graphite powder is coke, the ash content in the coke is less than or equal to 0.7 percent, the sulfur content is less than or equal to 0.8 percent, the water content is less than or equal to 0.5 percent, and the volume density is more than or equal to 1.6g/cm3The resistivity is less than or equal to 100 mu omega m.
As a modification, when the 3R Raymond mill is used for carrying out coarse grinding treatment on raw material particles, the frequencies of a fan a and a classifier a on the raw material particles are respectively controlled between 30-45HZ and 30-40 HZ.
As an improvement, in the process of finely grinding the powder particles, the main machine of the mechanical grinding machine has the operating frequency of 40-50HZ, the fan frequency of 30-45HZ and the classifier frequency of 20-40 HZ.
As an improvement, the standard index of the particle size of the powder is 32 μm, and the passing rate of the powder passing through the classifier is 65-75%; a particle size index of 63 μm, with a pass rate through the classifier of 92-98%; the particle size index is 80 μm, and the passing rate of the particles passing through the classifier is 96-98%; the particle size index is 100 μm and its passage through the classifier is 98-100%.
The invention has the beneficial effects that:
(1) according to the invention, the artificial stone powdered ink with standard indexes is accurately controlled by the matching production of the 3R Raymond mill and the mechanical mill, the standard uniform production of the powdered particles is realized by combining the control of the frequency of the fan a and the frequency of the classifier a in the 3R Raymond mill, and the frequency control of the host, the fan and the classifier in the mechanical mill is matched, so that the production efficiency and the controllability are greatly improved while the artificial graphite powdered powder with standard indexes can be produced, and the technical problem that the batch production of high-standard nuclear fuel elements is difficult to realize due to the fact that the powder index of the artificial graphite powder cannot be accurately controlled in the prior art is solved.
(2) According to the invention, the fine grinding and shaping of the powder in the traditional process are integrated and optimized to realize synchronous operation of the fine grinding process and the shaping process, the vortex airflow formed by rotation of the finely ground powder is collected in the operation process of the hammer head on the turntable and then transferred and output by the fan, and the collection control of the vortex airflow on the powder particles is controlled by the rotation frequency of the main machine, so that the qualified powder is automatically separated from the powder, and the accurate control of the powder index is realized.
(3) According to the invention, the special structure arrangement of the hammer head and the turntable enables the powder to be in multiple impact contact with the hammer head in the fine grinding process, so that the edges and corners of the powder are removed while the powder is finely ground, the powder particles are in a sphere-like shape, the bridging linearity of artificial stone ink powder particles is reduced, the loose packing density is improved, the density and the strength of a nuclear fuel element are improved, the adsorption and collection of fine powder are realized by combining vortex airflow generated by the hammer head in a rotating operation mode, and the control of powder indexes is realized by controlling the operation frequency of a main machine.
In conclusion, the invention has the advantages of reasonable mechanism, stable production, accurate powder index control and the like; in particular to a method for preparing powder of artificial graphite powder for a high-temperature gas cooled reactor nuclear fuel element.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings described below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a flow chart of the method of the present invention;
FIG. 2 is a SEM scanning electron microscope of conventional artificial graphite powder;
FIG. 3 is SEM scanning electron microscope image of the artificial graphite powder produced by the present invention;
FIG. 4 is a schematic view of the overall structure of the present invention;
FIG. 5 is a partial cross-sectional view of a mechanical mill according to the present invention;
FIG. 6 is a cross-sectional view taken at the center of A-A in FIG. 5;
FIG. 7 is a state diagram of one of the seventh embodiment of the present invention;
FIG. 8 is a second state diagram of a seventh embodiment of the present invention;
fig. 9 is a schematic sectional structure view of the classifier.
Detailed Description
The technical scheme in the embodiment of the invention is clearly and completely explained by combining the attached drawings.
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
Example one
The method for milling the artificial graphite powder for the nuclear fuel element of the high-temperature gas cooled reactor in the embodiment is described according to the attached figure 1 of the specification.
A powder preparation method of artificial stone ink powder for a high-temperature gas cooled reactor nuclear fuel element comprises the following steps:
(a) primary crushing, namely putting the artificial graphite powder raw material into a jaw crusher, and crushing to obtain raw material particles with the particle size of less than 20 mm;
(b) coarse grinding, namely conveying the raw material particles obtained in the step (a) into a 3R Raymond mill for grinding and crushing, and controlling the frequency of an upper fan a of the 3R Raymond mill to be 30-45HZ and the operating frequency of a classifier a to be 30-40HZ to obtain powder particles with the particle size of 150-; in this embodiment, the raw material particles obtained after crushing by the jaw crusher are lifted by the elevator and fed into the 3R raymond mill;
(c) fine grinding and shaping, namely feeding the powder particles obtained in the step (b) into a mechanical grinding mill, carrying out fine grinding treatment and primary shaping on the powder particles in a relative rotation friction mode by driving a turntable to rotate and a gear ring to rotate by a host machine in the mechanical grinding mill at the frequency of 40-50HZ, and realizing secondary shaping of powder through collision of a plurality of hammers arranged on the turntable and the powder particles so that the obtained powder has the particle size of 32-100 mu m and the appearance is similar to a sphere; and simultaneously controlling the rotation frequency of the fan to be 30-45HZ, and screening and outputting the powder after the secondary shaping by a classifier with the rotation frequency of 20-40HZ under the action of ascending airflow generated by the powder to obtain powder with a standard index, wherein the particle size of the powder with the standard index is 32-100 mu m.
The rotary disc throws the powder particles falling on the rotary disc out of a grinding area between the rotary disc and the gear ring in a rotating centrifugal mode, and in the process that the powder particles move to the grinding area while being finely ground through the relative motion of the rotary disc and the gear ring, the powder particles are in contact with the gear ring in an impact mode, so that the primary shaping of the gear ring on the powder particles is realized.
In addition, the powder particles are finely ground into powder through the rotary disc and the gear ring, and the powder is subjected to secondary shaping through the hammer head in a collision mode in the process that the powder is driven by vortex airflow formed by the rotation of the hammer head driven by the rotary disc to pass through the motion track of the hammer head and move from outside to inside.
Note that, for the nuclear fuel element
Specifically, after the powder is shaped in the second stage, the powder in the vortex airflow is absorbed and moved upwards by the ascending airflow formed by the fan in a negative pressure absorption mode, and the powder is filtered and screened by the classifier and then is driven to be output by the ascending airflow.
The device further comprises secondary grinding, wherein the powder is filtered and screened by a classifier to form fine powder and coarse powder, and the fine powder is driven by the ascending air flow to pass through the classifier and then is output; the coarse powder material is separated from the fine powder material by a classifier in a rotating mode and then falls freely, and is contacted with powder particles thrown out by a turntable in a centrifugal mode, and the powder particles are driven to enter a milling area for secondary milling.
Further, the raw material is coke, the ash content in the coke is less than or equal to 0.7 percent, the sulfur content is less than or equal to 0.8 percent, the water content is less than or equal to 0.5 percent, and the volume density is more than or equal to 1.6g/cm3The resistivity is less than or equal to 100 mu omega m.
As shown in FIGS. 2 and 3, the scanning images of the conventional artificial graphite powder and the artificial graphite powder produced by the present invention were obtained by SEM electron microscopy.
Example two
Wherein the same or corresponding components as in the first embodiment are designated by the same reference numerals as in the first embodiment, and for the sake of brevity, only the points of difference from the first embodiment will be described below; the second embodiment is different from the first embodiment in that: the coke selection indexes are as follows: the method comprises the following steps of feeding broken raw material particles with the particle size of less than 20mm into a 3R Raymond mill, carrying out breaking treatment on the raw material particles in a rotating rolling manner through three grinding rollers in the broken raw material particles, respectively controlling the rotating frequency of a fan to be 30HZ and the rotating frequency of a grader to be 30HZ, screening the powder particles with the particle size of less than 150 mu m, and then extracting and outputting the powder particles; performing powder extraction by a fan with 30HZ rotation frequency, and performing adsorption extraction on powder particles with particle size less than 150 μm by adsorption airflow generated by rotation of the fan, the powder particles with corresponding mass are effectively adsorbed and output according to the adsorption force generated by the adsorption airflow, and when the frequency of a fan is 30HZ after being summarized by multiple tests in the production process, the generated adsorption force can effectively transfer the powder with the particle size less than 150 mu m, and the powder with the particle size less than 150 mu m is filtered and sieved by combining a classifier with the frequency of 30HZ to filter and sieve the powder with the particle size less than 150 mu m, the larger powder particles do not influence the passing efficiency of the qualified powder, the high-efficiency screening output of the powder with the particle size index less than 150 mu m is realized, the production efficiency is improved, the accurate control of the particle size index of the powder is ensured, meanwhile, the production efficiency in the subsequent fine powder grinding process is improved by the limitation of the fineness of the powder indexes.
EXAMPLE III
Wherein the same or corresponding components as in the second embodiment are designated by the same reference numerals as in the first embodiment, and for the sake of convenience, only the points of difference from the second embodiment will be described below; the third embodiment is different from the second embodiment in that: the coke selection indexes are as follows: the method comprises the following steps of feeding broken raw material particles with the particle size of less than 20mm into a 3R Raymond mill, breaking the raw material particles in a rotating rolling mode through three grinding rollers in the raw material powder raw material which is made of artificial stone ink powder with the ash content of 0.3%, the sulfur content of 0.7%, the water content of 0.1%, the volume density of 1.66g/cm3 and the resistivity of 50 mu omega m, screening the powder particles with the particle size of less than 200 mu m and outputting the powder particles after being broken through respectively controlling the rotating frequency of a fan to be 45HZ and the rotating frequency of a grader to be 40 HZ; in this embodiment, the powder particles with corresponding mass are effectively adsorbed and output according to the adsorption force generated by the adsorption airflow, and through multiple tests and summary in the production process, when the frequency of the fan is 45HZ, the adsorption force generated by the fan can effectively transfer the powder with the particle size smaller than 200 μm, and the powder with the particle size smaller than 200 μm is filtered and sieved by combining with the rotation and sieving of the classifier with the frequency of 40HZ, so that the passing efficiency of qualified powder is not affected by larger powder particles while the powder with the particle size smaller than 200 μm is filtered and sieved, the high-efficiency sieving and output of the powder with the particle size index smaller than 200 μm is realized, and the accurate control of the particle size index of the powder is ensured while the.
Example four
Wherein the same or corresponding components as in the second and third embodiments are given the same reference numerals as in the second and third embodiments, and for the sake of brevity only the points of difference from the second and third embodiments will be described below; the fourth embodiment is different from the second and third embodiments in that: the operation frequency of the main machine of the mechanical mill during the fine grinding process of raw material particles is 40HZ, the fan frequency is 30HZ, the frequency of the classifier is 20HZ, and powder with the index of artificial stone toner powder being 32 mu m can be obtained, wherein the passing rate is 66.3%; the powder index is 63 mu m, and the passing rate is 93.5 percent; the powder index is 80 mu m, and the passing rate is 96.5 percent; the powder index is 100 mu m, and the passing rate is 98.3 percent; the corresponding powder indexes are selected according to different requirements of different artificial graphite, and the production efficiency of the artificial graphite is improved on the premise that the artificial graphite meets the compactness, strength and wear resistance by accurately controlling the powder indexes of the artificial graphite powder.
EXAMPLE five
Wherein the same or corresponding components as those in embodiment four are designated by the same reference numerals as those in embodiment four, and for the sake of convenience, only the points of difference from embodiment four will be described below; the fifth embodiment is different from the fourth embodiment in that: the operation frequency of the main machine of the mechanical mill during the fine grinding process of raw material particles is 45HZ, the fan frequency is 35HZ, the frequency of the classifier is 30HZ, and powder with the index of artificial stone toner powder being 32 mu m can be obtained, and the passing rate of the powder is 70.5%; the powder index is 63 mu m, and the passing rate is 95.3 percent; the powder index is 80 mu m, and the passing rate is 96.6 percent; the powder index is 100 mu m, and the passing rate is 98.5 percent; the corresponding powder indexes are selected according to different requirements of different artificial graphite, and the production efficiency of the artificial graphite is improved on the premise that the artificial graphite meets the compactness, strength and wear resistance by accurately controlling the powder indexes of the artificial graphite powder.
EXAMPLE six
Wherein the same or corresponding parts as those in embodiment five are designated by the same reference numerals as those in embodiment five, and for the sake of convenience, only the points different from embodiment five will be described below; the sixth embodiment is different from the fifth embodiment in that: the operation frequency of the main machine of the mechanical mill during the fine grinding process of raw material particles is 50HZ, the fan frequency is 45HZ, the frequency of the classifier is 40HZ, and powder with the index of artificial stone toner powder being 32 mu m can be obtained, wherein the passing rate is 73.9%; the powder index is 63 mu m, and the passing rate is 97.4 percent; the powder index is 80 mu m, and the passing rate is 98.2 percent; the powder index is 100 mu m, and the passing rate is 98.9 percent; the corresponding powder indexes are selected according to different requirements of different artificial graphite, and the production efficiency of the artificial graphite is improved on the premise that the artificial graphite meets the compactness, strength and wear resistance by accurately controlling the powder indexes of the artificial graphite powder.
For a visual representation of the embodiments described in examples two to six, the following table is summarized:
EXAMPLE seven
A mechanical mill according to the present embodiment is described with reference to figures 4-9 of the drawings.
As shown in fig. 4, 5, 6, 7 and 8, a mechanical pulverizer includes a fan 1, a classifier 2, and a main machine 3, where the main machine 3 includes a fine grinding bin 31, a rotary table 32 rotatably disposed in the fine grinding bin 31, a hammer 33 fixedly disposed on the rotary table 32, a gear ring 34 mounted in the fine grinding bin 31 and located on an outer ring of the rotary table 32, and a driving motor 35 for driving the rotary table 32 to rotate, and a grinding area 36 is formed between the rotary table 32 and the gear ring 34; the powder falls on the rotary table 32 through a feeding hole 311 arranged on the side wall of the fine grinding bin 31, the powder is thrown into the powder grinding area 36 in a centrifugal mode through the rotation of the rotary table 32, the powder is subjected to fine grinding treatment through the relative friction between the outer circumferential surface of the rotary table 32 and the gear ring 34, the powder formed after the fine grinding is driven by negative pressure airflow generated by the operation of the fan 1, and the powder is output after being screened and filtered by the classifier 2 to form the powder with standard indexes.
Further, as shown in fig. 4, 5 and 8, the fine grinding bin 31 is arranged in a cylindrical structure, the classifier 2 is located above the fine grinding bin 31, and the fan 1, the classifier 2 and the fine grinding bin 31 are sequentially communicated; after the fine grinding treatment is performed on the powder through the rotary disc 32 and the gear ring 34, the adsorption airflow generated by the operation of the fan 1 adsorbs and outputs the vortex airflow containing the powder formed by the rotation of the rotary disc 32, so that the continuous output of the fine ground powder is realized.
Further, as shown in fig. 5 and 9, the classifier 2 is provided with a rotary filter element structure, and is arranged in a horizontal manner; in the embodiment, in the process of screening the powder by the classifier 2, the unqualified powder is isolated and then rotated to drive the large-particle powder to fall down on one side, so that the classifier 2 screens and transfers the large-particle powder, and meanwhile, the powder is screened at different positions on the classifier 2, so that the production efficiency is improved while the large-particle powder is prevented from blocking a filter screen; in this embodiment, classifier 2 throws away the large granule powder that adsorb on it and can not pass through rotating centrifugal mode, and the unilateral that realizes the large granule powder through the filter core outside rather than the shell structure of cooperation setting falls.
Further, as shown in fig. 5 and 6, the number of the hammer heads 33 is 18-30, and the hammer heads are uniformly distributed around the axis of the rotating disc 32 and are convexly mounted on the upper surface of the rotating disc; through multiple experimental tests, when the number of the hammers 33 is 18-30, the appearance result of the powder particles is uniform sphere-like shape, when the number of the hammers 33 is too small, the sphere-like treatment of the powder particles is not facilitated, and when the number of the hammers 33 is too large, the distance between the hammers 33 is smaller, the operation of the powder particles is not facilitated, so that the impact frequency of the hammers 33 and the powder particles is reduced; in this embodiment, the spherical treatment of the powder particles mainly realizes the smooth treatment of the edges and corners of the powder particles by the collision of the powder particles with the rotating hammer 33 in the process of the movement driven by the airflow.
In addition, as shown in fig. 7 and 8, the powder formed by crushing with the 3R raymond mill falls on the rotating disc 32 after entering the fine grinding bin 31, and is thrown out to the grinding area 36 in a centrifugal mode in the rotating process of the rotating disc 32, and is impacted by the hammer 33 to realize the primary shaping of the powder; after the powder is finely ground by the rotary disc 32 and the gear ring 34, the powder in the grinding area 36 is collected and adsorbed by vortex airflow generated by the rotation of the rotary disc 32 driving the hammer 33, and the adsorbed airflow generated by the operation of the fan 1 carries the powder to be filtered and screened by the classifier 2 and then output, so that the output of the powder with standard index is realized.
Further, as shown in fig. 5 and 6, the gear ring 34 is an inner gear ring structure, the height of the hammer 33 is lower than that of the gear ring 34, powder particles are centrifugally thrown out by the turntable 32 and then are gathered in the powder grinding area 36, and the height of the gear ring 34 is larger than that of the hammer 33, so that in the process of gathering powder in the powder grinding area 36, the rotating hammer 33 pushes outwards along the radial direction of the turntable 32, and automatic filling in the powder grinding area 36 is realized.
In the present invention, it is to be understood that: the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," and the like are used in an orientation or positional relationship indicated in the drawings for convenience and simplicity of description only and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be construed as limiting the present invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
The above description is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any design concept that can be easily conceived by those skilled in the art through the technical suggestion of the present invention, such as integrating the fine grinding and shaping of the powder, and combining the frequency control of the main machine, the blower and the classifier during the coarse grinding and fine grinding shaping of the raw material to realize the accurate control of the powder index, should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.