CN109225641B - Preparation method of electrical-grade magnesium oxide powder - Google Patents
Preparation method of electrical-grade magnesium oxide powder Download PDFInfo
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- CN109225641B CN109225641B CN201810912408.4A CN201810912408A CN109225641B CN 109225641 B CN109225641 B CN 109225641B CN 201810912408 A CN201810912408 A CN 201810912408A CN 109225641 B CN109225641 B CN 109225641B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C7/00—Separating solids from solids by electrostatic effect
- B03C7/003—Pretreatment of the solids prior to electrostatic separation
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C7/00—Separating solids from solids by electrostatic effect
- B03C7/02—Separators
- B03C7/06—Separators with cylindrical material carriers
Abstract
The invention provides a preparation method of electrical magnesium oxide powder, which comprises the steps of carrying out high-voltage pulse electric field strengthening and pre-charging on electric melting magnesite after grinding and carrying out high-voltage electrostatic separation to obtain the electrical magnesium oxide powder. The preparation method of the electrical grade magnesia powder provided by the invention adopts the high-voltage pulse electric field to strengthen the pre-charge aiming at the characteristics of different particle sizes of fused magnesite, different magnetic impurities and different mechanical iron in electrical conductivity, rectification property and particle density, so that the particles have different charge polarities and charge quantities, and the particles of the pre-charge are separated by the high-voltage electrostatic field and move in different tracks under the action of the electric field force. Different fused magnesite and different impurities can be rapidly sorted and efficiently recycled by adjusting the polarity of the high-voltage pulse electric field and the polarity of the high-voltage electrostatic field and repeatedly sorting for many times.
Description
Technical Field
The invention relates to the technical field of production of electrical-grade magnesium oxide, and in particular relates to a preparation method of electrical-grade magnesium oxide powder.
Background
The fused magnesite ore in China has the advantages of high grade, less impurities, centralized occurrence and unique property. In the process of producing the electrical-grade magnesia powder by using the fused magnesia, the fused magnesia carries a large amount of mechanical iron and magnetic impurities, which can seriously affect the electrical property of the electrical-grade magnesia powder and the service life of a magnesia product, and the electrical-grade magnesia powder after production and processing contains a certain amount of ultrafine powder, which is easy to pollute the environment.
In the production of electrical grade magnesium oxide powder, the mesh number of mechanical sieving is always considered to be the most universal one, and the technological process is generally as follows: crushing → mechanical coarse screening → particle shaping → mechanical fine screening → air separation and dust removal → magnetic separation and iron removal. But because the fine materials with the particle size less than 325 meshes of the fused magnesia in the crushing process can generate adsorption force through friction, a large amount of fine mechanical iron is mixed in the fine materials, and the conventional magnetic separation iron removal is difficult to clean iron impurities, so that the insulating property of the electrical-grade magnesia powder is influenced, and potential safety hazards exist.
Disclosure of Invention
The invention aims to overcome the defect of incomplete iron removal in the production of the existing electrical-grade magnesia powder, and provides a preparation method of the electrical-grade magnesia powder for realizing the purpose.
According to the preparation method of the electrical-grade magnesia powder provided by the invention, the separation of the fused magnesia is realized by utilizing the principle that like charges repel and opposite charges attract in an electrostatic field. After ore grinding and dissociation, a large amount of Mg is scattered on the surfaces of the fused magnesite and the fused magnesite with magnetic impurities2+And Fe2+The ion, the zero potential point is relatively high, the electronegativity is relatively weak, and the mechanical iron can not be charged. Aiming at the characteristics of different particle sizes of fused magnesite, different magnetic impurities and mechanical iron, such as different conductivity, rectification and particle density, the high-voltage pulse electric field is adopted to strengthen the pre-charging, so that the particles have different charging polarities and different charging quantities, and the pre-charged particles are separated through the high-voltage electrostatic field and move in different tracks under the action of the electric field force, so that the particles can be well separated. Different fused magnesite and different impurities can be rapidly sorted and efficiently recycled by adjusting the polarity of the high-voltage pulse electric field and the polarity of the high-voltage electrostatic field and repeatedly sorting for many times.
Detailed Description
The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
The invention provides a preparation method of electrical magnesium oxide powder, which comprises the steps of carrying out high-voltage pulse electric field strengthening and pre-charging on electric melting magnesite after grinding and carrying out high-voltage electrostatic separation to obtain the electrical magnesium oxide powder.
According to the invention, an electrical grade is providedThe preparation method of magnesium oxide powder utilizes the principle of that like charges repel and opposite charges attract in electrostatic field to implement separation of electrofused magnesite. After ore grinding and dissociation, a large amount of Mg is scattered on the surfaces of the fused magnesite and the fused magnesite with magnetic impurities2+And Fe2+The zero potential point of the ion is relatively high, and the electronegativity is relatively weak; mechanical iron is not chargeable. Aiming at the characteristics of different particle sizes of fused magnesite, different magnetic impurities and mechanical iron, such as different conductivity, rectification and particle density, the high-voltage pulse electric field is adopted to strengthen the pre-charging, so that the particles have different charging polarities and different charging quantities, and the pre-charged particles are separated through the high-voltage electrostatic field and move in different tracks under the action of the electric field force, so that the particles can be well separated. Different fused magnesite and different impurities can be rapidly sorted and efficiently recycled by adjusting the polarity of the high-voltage pulse electric field and the polarity of the high-voltage electrostatic field and repeatedly sorting for many times.
Further, the steps of the high-voltage pulse electric field reinforced charging and the high-voltage electrostatic sorting are carried out once or for multiple times. After the low-quality fused magnesite abrasive material is ground, the better effects of demagnetization, iron removal and dust removal can be achieved through multiple times of high-voltage electrostatic separation.
Further, the parameters of the high voltage pulse are as follows: the rising leading edge is less than 200ns, the pulse width is less than 800ns, and the pulse peak value is 10-25 kV. Different high-voltage pulse parameters are adopted for different fused magnesite and impurity particles, so that a better separation effect can be obtained.
Further, the high-voltage pulse is a positive polarity high-voltage pulse, and the high-voltage electrostatic field is a positive polarity or a negative polarity. The fused magnesia particles with a certain particle size range can adjust the polarity of the high-voltage pulse electric field and the polarity combination of the high-voltage electrostatic field to improve the recovery rate of the fused magnesia aiming at different impurities and particle size relations.
Furthermore, the fused magnesite with magnetic impurities is sorted by a roller type electrostatic sorting device. The drum-type electrostatic separation device carries out separation: if a positive high-voltage pulse is combined with a positive high-voltage electrostatic field, the fused magnesite and the magnetic impurities are adsorbed on the grounding roller and collected, and the mechanical iron is not electrified and is separated in the separator due to vertical falling; if a positive voltage pulse is combined with a negative high-voltage electrostatic field, the fused magnesite and the mechanical iron are separated under the action of attraction force, and the mechanical iron is also separated after vertically falling. The roller type electrostatic sorting device can adjust the electrode angle and the parameters of the elliptical electrode according to the fused magnesite and magnetic impurities with different particle size ranges to further separate the fused magnesite and the impurities.
Further, the roller-type electrostatic sorting device has the sorting parameters as follows: the angle of the discharge electrode is 135-280 degrees, and the included angle between the rotation direction of the elliptical electrode and the vertical direction is 90-150 degrees.
Furthermore, the particle size of the fused magnesia after grinding is not more than 380 μm, and the fused magnesia with overlarge particle size is not beneficial to sorting.
Further, the electric-grade magnesium oxide powder is treated by an organic silicon moisture-proof agent coating to prepare moisture-proof electric-grade magnesium oxide powder; the usage amount of the organic silicon moisture-proof agent is 0.005-0.3% based on 100% of the weight of the electrical grade magnesium oxide powder. The organic silicon moisture-proof agent is selected from one or more of methyl hydrogen-containing silicone oil, methyl silicone resin and fumed silica.
The present invention will be described in further detail below with reference to examples.
Example 1
(1) And (3) crushing and grinding fused magnesia with 96 percent of magnesium content, and mechanically sorting by using a 40-mesh screen to obtain 40-mesh fused magnesia powder.
(2) Electrically fusing magnesite powder and strengthening the pre-charging through a high-voltage pulse electric field; the high-voltage pulse parameters are as follows: the rising edge is 120ns, the pulse width is 600ns, and the pulse peak value is 10kV, so that the pre-charged fused magnesia powder is obtained.
(3) Putting the obtained pre-charged fused magnesia powder into a drum-type electrostatic separator for high-voltage electrostatic separation, wherein the angle of a discharge electrode is 240 degrees, and the included angle between the rotation direction of an elliptical electrode and the vertical direction is 135 degrees; repeating the high-voltage electrostatic field for 1 time to obtain 40-325 mesh electrical grade magnesium oxide powder.
Example 2
(1) And (3) crushing and grinding fused magnesia with 96 percent of magnesium content, and mechanically sorting by using a 40-mesh screen to obtain 40-mesh fused magnesia powder.
(2) Electrically fusing magnesite powder and strengthening the pre-charging through a high-voltage pulse electric field; the high-voltage pulse parameters are as follows: the rising edge is 100ns, the pulse width is 500ns, and the pulse peak value is 15kV, so that the pre-charged fused magnesia powder is obtained.
(3) Putting the obtained pre-charged fused magnesia powder into a drum-type electrostatic separator for high-voltage electrostatic separation, setting the angle of a discharge electrode to be 135 degrees, and setting the included angle between the rotation direction of an elliptical electrode and the vertical direction to be 135 degrees; repeating the high-voltage electrostatic field for 2 times to obtain 40-325 mesh electrical grade magnesium oxide powder.
Example 3
(1) And (3) crushing and grinding fused magnesia with 96 percent of magnesium content, and mechanically sorting by using a 40-mesh screen to obtain 40-mesh fused magnesia powder.
(2) Electrically fusing magnesite powder and strengthening the pre-charging through a high-voltage pulse electric field; the high-voltage pulse parameters are as follows: rising leading edge 120ns, pulse width 550ns and pulse peak value 25kV to obtain the pre-charged fused magnesia powder.
(3) Putting the obtained pre-charged fused magnesia powder into a drum-type electrostatic separator for high-voltage electrostatic separation, wherein the angle of a discharge electrode is set to be 145 degrees, and the included angle between the rotation direction of an elliptical electrode and the vertical direction is set to be 135 degrees; repeating the high-voltage electrostatic field for 3 times to obtain 40-325 mesh electrical grade magnesium oxide powder.
Comparative example 1
The fused magnesia with 96 percent of magnesium content is taken to be crushed and ground and then screened to prepare 40-mesh fused magnesia powder. The electric smelting magnesia powder is subjected to air separation, magnetic separation and screening to obtain 40-325 mesh electric grade magnesia powder.
Test example 1
In the test example, the contents of magnetic impurities, mechanical iron and ultrafine powder (particle size is less than 400 meshes) of the electrical grade magnesium oxide prepared in the examples 1 to 3 and the comparative example 1 are tested according to the experimental method of JBT 8508-1996 electrical grade magnesium oxide. Specific results are shown in table 1.
TABLE 1
| Example 1 | Example 2 | Example 3 | Comparative example 1 | |
| Magnetic impurities (PPM) | 542 | 482 | 345 | 1125 |
| Mechanical iron (wt%) | 0.01 | 0.005 | 0.001 | 0.02 |
| Ultra-fine powder (wt%) | 0.3 | 0.2 | 0.2 | 1.1 |
Test example 2
The weight ratio of the mixture of the electrical-grade magnesium oxide powder prepared in the embodiments 1-3 and the alkyl mixture of the organic silicon moisture-proof agent prepared in the comparative example 1 is 1: 0.003 of magnesium oxide powder, and the moisture-proof electric magnesium oxide powder is prepared by uniformly mixing and stirring the components and then airing the mixture. Wherein the organic silicon moisture-proof agent alkyl mixture is fumed silica and No. 200 solvent oil according to the weight ratio of 1: 0.5, mixing and stirring. In the test example, the moisture absorption rate, hydration resistance, insulation and compression strength, leakage current, thermal insulation resistance and thermal insulation and compression strength of the electrical magnesium oxide powder in the example 1 to the example 3 and the comparative example 1 after the moisture-proof treatment are tested according to the experimental method of JBT 8508-1996 electrical magnesium oxide, and specific results are shown in table 2.
TABLE 2
| Example 1 | Example 2 | Example 3 | Comparative example | |
| Leakage current (mA) | 0.10 | 0.09 | 0.08 | 0.15 |
| Thermal insulation resistance (M omega) | 8 | 10 | 20 | 2 |
| Thermal insulation compressive strength (V) | 2400 | 2500 | 200 | 2000 |
As can be seen from comparison between examples 1 to 3 in tables 1 and 2 and comparative example 1, the method for preparing the electric-grade magnesia powder provided by the invention realizes separation of the fused magnesia by using the principle that like charges repel and opposite charges attract in an electrostatic field, so that the removal rate of magnetic impurities and mechanical iron of the fused magnesia is improved; the parameters of the high-voltage pulse electric field and the high-voltage electrostatic field are adjusted to recover the fused magnesite with different particle sizes and remove different impurities, and compared with the existing technology of fused magnesite winnowing and magnetic separation, the technology has obvious progress.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
Claims (4)
1. The preparation method of the electrical magnesium oxide powder is characterized by comprising the steps of carrying out high-voltage pulse electric field strengthening and pre-charging on the ground fused magnesia, and carrying out high-voltage electrostatic separation on the ground fused magnesia to obtain the electrical magnesium oxide powder; the grain diameter of the grinded fused magnesia is not more than 380 μm; the parameters of the high-voltage pulse are as follows: rising leading edge 120ns, pulse width 550ns and pulse peak value 25 kV; the fused magnesia with magnetic impurities is separated by a drum-type electrostatic separation device, and the separation parameters of the drum-type electrostatic separation device are as follows: the angle of the discharge electrode is 145 degrees, and the included angle between the rotation direction of the elliptical electrode and the vertical direction is 135 degrees.
2. The method of claim 1, wherein the steps of high-voltage pulsed electric field enhanced charging and high-voltage electrostatic sorting are performed one or more times.
3. The method of claim 1, wherein the high voltage pulse is a positive polarity high voltage pulse and the high voltage electrostatic sorting electric field is either positive or negative.
4. The method of claim 1, wherein the electrical grade magnesium oxide powder is treated with a silicone moisture barrier coating to produce a moisture-resistant electrical grade magnesium oxide powder; the usage amount of the organosilicon moisture-proof agent is 0.005-0.3% based on the weight of the electrical grade magnesium oxide powder as 100%.
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| CN110256870B (en) * | 2019-07-17 | 2021-03-12 | 辽宁嘉顺化工科技有限公司 | Preparation method and production device of moisture-proof high-pressure-resistant high-temperature-resistant electrical-grade magnesium oxide |
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Address after: 115000 huizhuang village, Yong'an Town, Dashiqiao City, Yingkou City, Liaoning Province Patentee after: Liaoning Jiashun Technology Co.,Ltd. Address before: 115100 huizhuang village, Yong'an Town, Dashiqiao City, Yingkou City, Liaoning Province Patentee before: LIAONING JIASHUN CHEMICAL SCIENCE AND TECHNOLOGY Co.,Ltd. |