CN115557521B - Method for controlling impurity migration in fused magnesium melting preparation process and electrode angle adjusting device - Google Patents
Method for controlling impurity migration in fused magnesium melting preparation process and electrode angle adjusting device Download PDFInfo
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- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 title claims abstract description 50
- 229910052749 magnesium Inorganic materials 0.000 title claims abstract description 50
- 239000011777 magnesium Substances 0.000 title claims abstract description 50
- 238000000034 method Methods 0.000 title claims abstract description 50
- 238000002844 melting Methods 0.000 title claims abstract description 41
- 230000008018 melting Effects 0.000 title claims abstract description 41
- 239000012535 impurity Substances 0.000 title claims abstract description 34
- 230000005012 migration Effects 0.000 title claims abstract description 15
- 238000013508 migration Methods 0.000 title claims abstract description 15
- 238000002360 preparation method Methods 0.000 title abstract description 7
- 238000003723 Smelting Methods 0.000 claims abstract description 55
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims abstract description 30
- 239000002994 raw material Substances 0.000 claims abstract description 23
- 239000001095 magnesium carbonate Substances 0.000 claims abstract description 20
- 235000014380 magnesium carbonate Nutrition 0.000 claims abstract description 20
- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 claims abstract description 20
- 229910000021 magnesium carbonate Inorganic materials 0.000 claims abstract description 20
- 230000008569 process Effects 0.000 claims abstract description 19
- 239000000395 magnesium oxide Substances 0.000 claims abstract description 18
- 238000010309 melting process Methods 0.000 claims abstract description 9
- 238000010891 electric arc Methods 0.000 claims description 31
- 238000002425 crystallisation Methods 0.000 claims description 9
- 230000008025 crystallization Effects 0.000 claims description 9
- 239000013078 crystal Substances 0.000 claims description 8
- 238000001816 cooling Methods 0.000 claims description 7
- 238000010438 heat treatment Methods 0.000 claims description 5
- 238000011217 control strategy Methods 0.000 claims description 4
- 230000000630 rising effect Effects 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims 1
- 230000001276 controlling effect Effects 0.000 abstract 3
- 230000001105 regulatory effect Effects 0.000 abstract 1
- 230000000052 comparative effect Effects 0.000 description 7
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 230000007246 mechanism Effects 0.000 description 6
- 238000002347 injection Methods 0.000 description 5
- 239000007924 injection Substances 0.000 description 5
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 4
- 229910002804 graphite Inorganic materials 0.000 description 4
- 239000010439 graphite Substances 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- 239000000155 melt Substances 0.000 description 3
- 238000007711 solidification Methods 0.000 description 3
- 230000008023 solidification Effects 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 229910004298 SiO 2 Inorganic materials 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 230000017525 heat dissipation Effects 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 230000002093 peripheral effect Effects 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000001311 chemical methods and process Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000005261 decarburization Methods 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- NDLPOXTZKUMGOV-UHFFFAOYSA-N oxo(oxoferriooxy)iron hydrate Chemical compound O.O=[Fe]O[Fe]=O NDLPOXTZKUMGOV-UHFFFAOYSA-N 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F5/00—Compounds of magnesium
- C01F5/02—Magnesia
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Inorganic Chemistry (AREA)
- Vertical, Hearth, Or Arc Furnaces (AREA)
Abstract
The application discloses a method for controlling impurity migration in the process of melting and preparing electric smelting magnesium and an electrode angle adjusting device. A method for controlling impurity migration in the process of fused magnesium melting preparation mainly comprises the following steps: (1) Using magnesite as a raw material, uniformly distributing three-phase electrodes in a three-phase electric smelting magnesium furnace, and keeping the power constant by adopting a method of adjusting the inclination angle of the electrodes; (2) reducing and maintaining constant the power value; (3) When the height of the molten pool reaches the height of the furnace body, the power value is reduced again and kept constant, then the furnace is shut down after power is cut off, and the furnace is slowly cooled to enable the furnace to crystallize naturally. According to the method for controlling impurity migration in the fused magnesia melting preparation process and the electrode angle adjusting device, disclosed by the application, a constant power control mode in each smelting stage is adopted, so that the constant temperature of the magnesite melting process is ensured, the time scale of constant power is regulated, the impurity content in fused magnesia is reduced, and the product quality of the fused magnesia is improved.
Description
Technical Field
The application relates to the technical field of electric smelting magnesium oxide, in particular to a method for controlling impurity migration in the electric smelting magnesium smelting preparation process and an electrode angle adjusting device.
Background
The electric smelting magnesite is mainly 47 percentThe upper magnesite is prepared by melting in an electric arc furnace, and the melting process of magnesia (MgO) from raw materials is the melting process of fused magnesite. The magnesite raw material contains a plurality of impurities, mainly SiO 2 、CaO、Al 2 O 3 And Fe (Fe) 2 O 3 And the chemical indexes of the fused magnesia mainly comprise magnesium oxide content, silicon dioxide content, ferric oxide content, aluminum oxide content and the like.
In general, the process of producing fused magnesium crystals by the electric melting method can be roughly divided into three stages: furnace starting, melting and ending. And (3) a furnace starting stage: a layer of magnesite is arranged at the bottom of a furnace, then electrodes are inserted, carbon blocks are placed between the electrodes to serve as arc striking materials, and the positions of the electrodes are adjusted to strike arcs. After the arc is started, magnesite raw material can be added near the electrode, a molten pool is formed at the lower end of the electrode, and then the melting process is carried out. The height of the molten pool is increased continuously with the input and melting of the raw materials. Thus, during the melting process, the electrode is continuously adjusted to rise as the bath rises. The melt melted in the prior art is condensed and crystallized due to continuous heat dissipation and temperature reduction of the furnace body, so as to form a melting lump. Along with the extension of the melting time, the molten pool continuously rises until the molten pool reaches the surface of the upper opening of the furnace shell, and the melting process is ended at the moment and enters the ending stage. Stopping supplying power, and then pulling the melting lump out of the melting station together with the furnace body, and naturally cooling. As the electrode is lifted, mgO crystals begin at the edge of the melt where the temperature gradient is large, and as the crystals grow, the remaining impurities are transferred into the remaining melt. As the crystal progresses inward, the impurities continue to migrate toward the center, and as the crystallization progresses, the impurities are driven into the center region. As the electrode rises, the molten zone moves upward and the impurities also move upward.
During the melting process, the total power of the electric arc furnace is the sum of the arc power and the bath power. The high temperature generated by the arc causes the magnesite raw material to undergo physical and chemical processes such as dehydration, decarburization and the like in the furnace and to be melted. The arc power is high, the melting pool power is relatively low, so that the materials are melted quickly, the melting pool cannot reach enough depth, the melting pool is unstable, the formed melting lump is small, and impurities of the materials cannot be fully separated out. If the power of the molten pool is high, the heating power of the electric arc becomes small, the melting temperature in the furnace is not enough, and the melting time of the materials is long. In the current electric smelting magnesium smelting process, an electric smelting magnesium furnace relies on frequent lifting of electrodes to keep two power balances, so that severe fluctuation of injection power is caused, electric arc power and molten pool power in the smelting process cannot be controlled quantitatively, the injection power and working current of the electric arc furnace frequently fluctuate, the operation process completely depends on experience, constant temperature gradient required by magnesium oxide crystallization and impurity migration processes cannot be ensured, and unstable quality of electric smelting magnesite products is caused.
Disclosure of Invention
The application discloses a method for controlling impurity migration in the process of smelting and preparing fused magnesia and an electrode angle adjusting device, which adopt a constant power control mode in each smelting stage to ensure the constant temperature of the magnesite in the process of smelting, prescribe the time scale of constant power in each smelting stage, enable magnesium oxide crystallization and impurity migration to have sufficient conditions, reduce the impurity content in fused magnesia, and further improve the product quality of the fused magnesia.
In order to achieve the above object, a first object of the present application is to provide a method for controlling impurity migration in a fused magnesium melting preparation process, wherein a control strategy of constant power rise, constant power hold and constant power fall is adopted in the processes of raw material temperature rising, melting and crystallization, and the method mainly comprises the following steps:
(1) Heating: the method comprises the steps of uniformly distributing three-phase electrodes in a three-phase electric smelting magnesium furnace by using magnesite as a raw material, adjusting the input power of a power supply, and simultaneously adopting a method for adjusting the inclination angle of the electrodes to change the distance between the bottoms of the three-phase electrodes, so that the total power of the electric arc furnace is constantly increased, the power increasing time is T1, T1 is more than or equal to 1.5h and less than or equal to 2h, the increasing rate is 30-50kW/min, and the raw material in the three-phase electric smelting magnesium furnace is gradually changed into a molten state;
(2) Melting: the method is characterized in that a molten pool is formed after raw materials in a three-phase electric smelting magnesium furnace are melted, the distance between the bottoms of three-phase electrodes is changed by adopting a method of adjusting the inclination angle of the electrodes again, the total power of the electric arc furnace is kept constant, the power constant time is T2, and T2 is more than or equal to 5h and less than or equal to 6h;
(3) And (3) crystallization: when the height of the molten pool reaches the height of the furnace body, the input power of a power supply is reduced, the total power of the electric arc furnace is reduced at a constant speed, the descending time is T3, T3 is more than or equal to 2h and less than or equal to 3h, the descending speed is 10-30kW/min, then the furnace is shut down after power is off, the electric arc furnace is slowly cooled to enable the electric arc furnace to naturally crystallize, and the cooling time is more than 25h, so that the electric smelting magnesium crystal is obtained.
Further, the grain size of the magnesite is 30-50mm.
Further, the total electric arc furnace power is the sum of the electric arc power and the bath power, wherein the ratio of the electric arc power to the total electric arc furnace power is 0.35-0.45.
Further, the electrode angle adjustment range is 0-10 °.
The application provides a device for adjusting the inclination angle of an electrode, which is used for the electrode angle in the method and comprises a driving mechanism and three upright posts vertically arranged outside a three-phase electric smelting magnesium furnace, wherein a horizontal cross arm which is horizontally arranged is fixedly arranged between the upright posts and the electrode, one end of the horizontal cross arm, which is close to the electrode, is rotatably provided with a rotating shaft, the electrode is rotatably connected with the horizontal cross arm through the rotating shaft, the driving mechanism can drive the electrode to rotate by taking the rotating shaft as a center, and a lifting assembly which can drive the upright posts to lift is further arranged outside the three-phase electric smelting magnesium furnace.
Further, the driving mechanism comprises a push rod motor and a synchronizing pin arranged on the electrode, a push rod of the push rod motor is parallel to the horizontal cross arm, the push rod motor is fixedly connected with the horizontal cross arm, and the extending end of the push rod motor is hinged with the electrode through the synchronizing pin.
Further, the lifting assembly comprises a driving motor fixedly arranged on the horizontal cross arm, a gear arranged at the output end of the driving motor and a rack meshed with the gear, and the rack is arranged along the length direction of the upright post.
Further, each electrode is fixedly provided with a holder, and the rotating shaft is connected with the holder.
The method for controlling impurity migration in the fused magnesium melting preparation process disclosed by the application has the beneficial effects that: in the process of preparing the fused magnesia with magnesite as the raw material, the power injected into the electric arc furnace is kept stable in different smelting stages, and the temperature conditions of the raw material heating, melting and crystallizing processes of the electric arc furnace are controlled. The lifting of the electrode is realized in the three-phase alternating current magnesium melting furnace through the lifting component, meanwhile, an angle adjusting device is added on the basis of lifting the electrode, the electrode spacing is adjusted through the adjustment of the angle of the electrode, the included angle between the electrode and the vertical direction is increased, the electrode spacing is reduced, the electric arc power is increased, and the stable power of each stage of magnesium melting is kept by adopting a method of adjusting the inclination angle of the electrode. In the electrode lifting process, the height of a molten pool rises, the temperature of the bottom of the molten pool is reduced, and magnesium oxide is crystallized to form a fused mass. In the electrode lifting process, impurities move upwards, the solidification trend of the melting lump is that the melting lump advances from bottom to top in the axial direction, the melting pool moves from the middle to top in the radial direction gradually from the peripheral wall surface to the center of the melting pool. During electrode lifting, the height of the molten pool rises and impurities move upwards. The melting points of various impurities in the raw materials are different, the constant power stable control is adopted in each smelting stage, the impurities with different components are melted at the respective melting point temperatures in sequence, enough time is provided for migration, the impurities are separated out successively, and the purity of the fused magnesium is improved.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions of the prior art, the drawings that are needed in the embodiments or the description of the prior art will be briefly described below, it will be obvious that the drawings in the following description are some embodiments of the present application, and that other drawings can be obtained according to these drawings without inventive effort to a person skilled in the art.
FIG. 1 is a schematic view of the whole structure of an arc furnace and an electrode lifting and tilting angle adjusting device disclosed by the application;
FIG. 2 is an enlarged view of the device for adjusting the inclination angle of the electrode according to the present application;
FIG. 3 is a schematic view of the center distance of the bottom of the electrode according to the present application;
fig. 4 is a power control curve of the present application.
In the figure: 1. an alternating current three-phase power supply; 2. a power supply short network; 3. an electrode; 4. a holder; 5. a rotating shaft; 6. a push rod; 7. a push rod motor; 8. a rack; 9. a driving motor; 10. an arc furnace; 11. a column; 12. a horizontal cross arm; 13. and a synchronizing pin.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to fig. 1 to 4 in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
The three-phase electric smelting magnesium furnace has three-phase 35000kVA capacity, 10kV primary voltage and 100-220V secondary voltage, and the primary and secondary are Y/[ delta ] connected. The capacity of the electric arc furnace is 3000KVA, three graphite electrodes are arranged in a regular triangle, three-phase short net is used for supplying power, the voltage of the electrodes is 100-220V and the current is 14500A.
Example 1
The whole structure of the arc furnace and the electrode lifting and tilting angle adjusting device used in the application are schematically shown in figure 1.
The utility model provides a device for adjusting electrode inclination, its electrode 3 angle that is arranged in adjusting three-phase electrode 3 in the three-phase electric smelting magnesium stove, and during initial state, three electrode 3 are all vertical to be set up in the inside of three-phase electric smelting magnesium stove, and three electrode 3 are triangle-shaped and distribute, and electric smelting magnesium stove outside is provided with an alternating current three-phase power supply 1, and alternating current three-phase power supply 1 and three electrode 3 are connected through power supply short net 2 respectively. The device comprises three upright posts 11 which are vertically arranged outside a three-phase electric smelting magnesium furnace, the three upright posts 11 respectively correspond to the three electrodes 3, the three upright posts 11 are distributed in a triangle shape outside the three-phase electric smelting magnesium furnace, each upright post 11 is connected with the corresponding electrode 3 through a horizontal cross arm 12 which is horizontally arranged, one end of the horizontal cross arm 12 is fixedly connected with the upright posts 11 to form a whole in a cross shape, and the other end of the horizontal cross arm is rotationally connected with the electrode 3.
Referring to fig. 1 and 2, a rotating shaft 5 is rotatably connected to one end of a horizontal cross arm 12, which is close to an electrode 3, a holder 4 is sleeved outside the electrode 3, the holder 4 is fixedly connected with the electrode 3, an arc-shaped lug plate is integrally formed on the holder 4, the lug plate is inserted into the horizontal cross arm 12 from the end of the horizontal cross arm 12 and is fixedly connected with the rotating shaft 5, a yielding groove for the lug plate to rotate is formed in the end of the horizontal cross arm 12, the aperture of the yielding groove is smaller than the outer diameter of the holder 4, and when the rotating shaft 5 rotates, the electrode 3 can be driven to synchronously overturn through the lug plate, so that the lower ends of the three electrodes 3 are close to or far away from each other, and the adjustment of the spacing between the three electrodes 3 is realized.
With reference to fig. 1 and 2, a driving mechanism capable of driving the rotating shaft 5 to rotate is arranged outside the three-phase electric smelting magnesium furnace, the driving mechanism comprises a push rod motor 7 and a synchronizing pin 13, the synchronizing pin 13 and the rotating shaft 5 are arranged in parallel, the synchronizing pin 13 is fixedly connected with the holder 4, the push rod motor 7 is fixedly arranged at one end of the horizontal cross arm 12 far away from the electrode 3, the push rod 6 of the push rod motor 7 is parallel to the horizontal cross arm 12, the push rod 6 of the push rod motor 7 is rotationally connected with the synchronizing pin 13, the push rod motor 7 is started, the push rod 6 of the push rod motor 7 can push or pull back in the straight line direction, the push rod 6 pulls the synchronizing pin 13 to enable the holder 4 to rotate at a certain angle by taking the rotating shaft 5 as the center, the electrode 3 is further inclined in the vertical direction, and the inclination angle range of the electrode 3 is 0-10 degrees.
Referring to fig. 1 and 2, a fixing seat is fixedly arranged at one end of the horizontal cross arm 12, which is close to the upright 11, a through hole is formed in the middle of the fixing seat, the upright 11 penetrates through the through hole, and a lifting assembly for driving the horizontal cross arm 12 to move along the length direction of the upright 11 is arranged between the horizontal cross arm 12 and the upright 11. The lifting assembly comprises a rack 8 fixedly arranged on the upright post 11, a gear meshed with the rack 8 and a driving motor 9 for driving the gear to rotate, the rack 8 is arranged along the vertical length direction of the upright post 11, the driving motor 9 is fixedly arranged on the fixing seat, and the gear is fixedly arranged at the output end of the driving motor 9. Because the gear is meshed with the rack 8, when the gear rotates clockwise, the gear drives the horizontal cross arm 12 to move upwards through the fixing seat; when the gear rotates anticlockwise, the gear drives the horizontal cross arm 12 to move downwards through the fixing seat, the driving motor 9 and the push rod motor 7 are respectively electrically connected with a control system of the three-phase electric smelting magnesium furnace, so that the lifting of the horizontal cross arm 12 (namely the lifting of the electrode 3) and the inclination angle adjustment of the graphite electrode 3 are automatically completed by the control system, and the automatic adjustment is performed according to the fluctuation condition of the power in the three-phase electric smelting magnesium furnace, so that the power stability is kept.
The implementation principle of the application is as follows: on the basis of lifting the electrode 3, the method for adjusting the spacing of the electrode 3 is added to keep the injection power constant, the included angle between the electrode 3 and the vertical direction is increased, the spacing of the electrode 3 is increased, the arc power is increased, and the spacing of the electrode 3 is adjusted through the inclination angle of the electrode 3. The electrode 3 is initially in a vertical state, is fixed by a holder 4, the holder 4 is fixed with a rotating shaft 5, is driven by a push rod 6 of a push rod motor 7, forms an included angle with the vertical direction, three electrodes 3 are linked together under the action of a control system of the three-phase electric smelting magnesium furnace, the included angle range of the electrode 3 and the vertical direction is 0-10 degrees, the center distance of the bottoms of the three electrodes 3 is changed (refer to figure 3), and the lifting and the angle of the electrode 3 are automatically adjusted by the control system of the three-phase electric smelting magnesium furnace according to the change power fluctuation of the electric arc furnace 10, so that the power is kept constant. The gear rack 8 is adopted to control the electrode 3 to lift, the driving mechanism is used to adjust the vertical inclination angle of the electrode 3, the arc current setting range is 25% -150% of rated current value, and the response time of the electrode 3 is less than or equal to 0.15S.
Example 2
A method for controlling impurity migration in the process of preparing fused magnesium by electric smelting adopts a control strategy of constant power rise, constant power hold and constant power fall in the processes of raw material temperature rise, fusion and crystallization, wherein the control strategy is shown in figure 4 and mainly comprises the following steps:
(1) Heating: the method comprises the steps of taking magnesite powder as a raw material, paving a layer of magnesite powder at the bottom of a three-phase electric smelting magnesium furnace, uniformly distributing three-phase electrodes 3 in the three-phase electric smelting magnesium furnace, putting carbon blocks between the electrodes 3 as arc striking materials, and adjusting the positions of the electrodes 3 to strike arcs. Before the arc is started, the bottoms of the three graphite electrodes 3 are close to the center and are in a maximum inclined state, namely, the inclination angle of the electrodes 3 is 10 degrees; after the arc is started, raw materials around the electrode 3 gradually become a molten state, at the moment, a control system of the three-phase electric smelting magnesium furnace simultaneously controls the lifting electrode 3 and reduces the inclination angle of the three electrodes 3 according to the power fluctuation condition in the electric arc furnace 10, the bottom space S (see figure 4) of the electrode 3 is increased, and the arc current is adjusted, so that the total power of the electric arc furnace 10 is constantly increased, the power increasing time is T1=1.5 h, the increasing rate is 30kW/min, and the raw materials in the furnace gradually become the molten state;
(2) Melting: after the arcing is finished, the materials around the electrode 3 gradually become a molten state, the running power of the arc furnace 10 reaches 3000kW, a space is left in the three-phase electric smelting magnesium furnace, a molten pool is formed at the lower end of the electrode 3 after the magnesite raw materials are continuously added, the height of the molten pool is continuously increased along with the feeding and melting of the magnesite raw materials, and the graphite electrode 3 is also increased along with the rising of the molten pool in order to keep the power constant; simultaneously, the inclination angle of the electrode 3 is adjusted to be 0-10 degrees under the action of the motor of the push rod 6, the total power of the arc furnace 10 is kept constant, and the power constant time is T2=5h; automatically controlling the ratio of the arc power to the molten pool power to be 0.35 by a control system;
in the melting process, the electrode 3 is continuously adjusted and risen along with the rise of the height of the molten pool, and the melt melted before is gradually condensed and crystallized due to the continuous heat dissipation and cooling of the furnace body to form a melting lump; the purity of magnesium oxide in the initially crystallized fused magnesia is highest, and the impurity concentration is lowest;
(3) And (3) crystallization: as the melting time is prolonged, the height of the molten pool is continuously increased, when the height of the molten pool reaches the height of a furnace shell, the input power of a power supply is reduced, the total power of the electric arc furnace 10 is reduced at a constant rate, the descending time is t3=2h, the descending rate is 10kW/min, impurities move upwards in the process, the solidification trend of the molten pool is that the impurities are pushed from bottom to top in the axial direction, the solidification trend of the molten pool is gradually carried out from the peripheral wall surface to the center of the molten pool in the radial direction, and the molten pool moves from the middle to the top; and then cutting off the power and stopping the furnace, pulling the melting lump together with the furnace body away from the melting station, and slowly cooling to enable the melting lump to be naturally crystallized, wherein the cooling time is more than 25 hours, thus obtaining the electric smelting magnesium crystal.
Example 3: the difference from example 2 is that t1=2h, t2=6h, t3=3h.
Example 4: the difference from example 3 is that in step (2), the ratio of arc power to bath power is automatically controlled to 0.45 by the control system.
Comparative example
Comparative example 1: the difference from example 2 is that the three-phase electric smelting furnace is replaced by a common electric smelting furnace, and the electrodes are kept in a vertical state at each smelting stage; in the melting stage of step (2), the ratio of the arc power to the bath power is not controlled.
Performance test
The following performance tests were conducted on the fused magnesium crystals prepared in examples 2 to 4 and comparative example 1, respectively, and the test results are shown in Table 1.
Component measurement: the determination of the components was carried out according to JB/T8508-1996 Electrical grade magnesium oxide.
Table 1: test results of examples 2-4 and comparative example 1
| Test item | MgO(wt％) | CaO(wt％) | SiO 2 (wt％) | Al 2 O 3 (wt％) | Fe 2 O 3 (wt％) |
| Example 2 | 97.5 | 0.75 | 0.98 | 0.34 | 0.16 |
| Example 3 | 97.5 | 0.77 | 0.98 | 0.33 | 0.22 |
| Example 4 | 98.2 | 0.57 | 0.67 | 0.2 | 0.06 |
| Comparative example 1 | 96.6 | 1.04 | 1.57 | 0.31 | 0.43 |
As can be seen from the combination of examples 2 to 4 and comparative example 1 and the combination of Table 1, the impurity components CaO and SiO of the fused magnesium products prepared by the method of the present application 2 、Al 2 O 3 、Fe 2 O 3 The application is obviously lower than that of the electric smelting magnesium smelted by the common method (comparative example 1), which shows that the application can effectively inhibit the power fluctuation of the arc rate by adjusting the inclination angle of the electrode, so that the power injection of the electric arc furnace in each smelting stage of the electric smelting magnesium is stable, and the quality of the electric smelting magnesium product is improved. The preferred examples of examples 2-4 are 4, caO, siO 2 、Al 2 O 3 、Fe 2 O 3 The impurity content is the lowest, which shows that increasing the total power stabilizing time of the electric arc furnace in each smelting stage is beneficial to reducing the impurity content in the electric smelting magnesium product.
The impurity components of the fused magnesium product prepared by the method are obviously lower than those of fused magnesium smelted by the common method, the method for adjusting the electrode spacing is added on the basis of lifting the electrode, the injection power is kept constant, the included angle between the electrode and the vertical direction is increased, the electrode spacing is increased, the arc power is increased, and the electrode spacing is adjusted by the inclination angle of the electrode.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and not for limiting the same; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the application.
Claims (2)
1. A method for controlling impurity migration in the process of preparing electric smelting magnesium is characterized in that a control strategy of constant power rise, constant power hold and constant power fall is adopted in the processes of raw material temperature rise, smelting and crystallization, and mainly comprises the following steps:
(1) Heating: the method comprises the steps of uniformly distributing three-phase electrodes (3) in a three-phase electric smelting magnesium furnace by taking magnesite as a raw material, adjusting the input power of a power supply, and simultaneously changing the distance between the bottoms of the three-phase electrodes (3) by adopting a method for adjusting the inclination angle of the electrodes (3), so that the total power of the electric arc furnace (10) is constantly increased, the power increasing time is T1, T1 is less than or equal to 1 h and less than or equal to 2h, and the increasing rate is 30-50kW/min, so that the raw material in the three-phase electric smelting magnesium furnace is gradually changed into a molten state; the three-phase electrodes (3) are arranged in a regular triangle, and before the arc is started, the bottoms of the three-phase electrodes (3) are close to the center and are in a maximum inclined state;
(2) Melting: after raw materials in the three-phase electric smelting magnesium furnace are melted to form a molten pool, a method for adjusting the inclination angle of the electrode (3) is adopted again, the distance between the bottoms of the three-phase electrodes (3) is changed, the total power of the electric arc furnace (10) is kept constant, the power constant time is T2, and T2 is more than or equal to 5h and less than or equal to 6h; in the melting process, the three-phase electrode (3) is continuously adjusted and lifted along with the rising of the height of the molten pool;
(3) And (3) crystallization: when the height of the molten pool reaches the height of the furnace body, reducing the input power of a power supply, reducing the total power of the electric arc furnace at a constant speed, wherein the descending time is T3, T3 is more than or equal to 2h and less than or equal to 3h, the descending speed is 10-30kW/min, then powering off and stopping the furnace, and slowly cooling to enable the furnace to crystallize naturally, wherein the cooling time is more than 25h, thus obtaining the fused magnesium crystal;
the total power of the electric arc furnace is the sum of the electric arc power and the molten pool power, wherein the ratio of the electric arc power to the total power of the electric arc furnace is 0.35-0.45;
the angle adjustment range of the electrode is 0-10 degrees.
2. The method for controlling impurity migration in a fused magnesia production process according to claim 1, wherein the grain size of the magnesite is 30-50mm.
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