CN113061728A - Method for extracting valuable metal elements from coal gangue - Google Patents
Method for extracting valuable metal elements from coal gangue Download PDFInfo
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- CN113061728A CN113061728A CN202110297474.7A CN202110297474A CN113061728A CN 113061728 A CN113061728 A CN 113061728A CN 202110297474 A CN202110297474 A CN 202110297474A CN 113061728 A CN113061728 A CN 113061728A
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
- C22B7/006—Wet processes
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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
- B03B—SEPARATING SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS
- B03B7/00—Combinations of wet processes or apparatus with other processes or apparatus, e.g. for dressing ores or garbage
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/113—Silicon oxides; Hydrates thereof
- C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
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- 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
- C01F7/00—Compounds of aluminium
- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
- C01F7/04—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom
- C01F7/08—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom by treating aluminous minerals with sodium carbonate, e.g. sinter processes
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- 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
- C01F7/00—Compounds of aluminium
- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
- C01F7/04—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom
- C01F7/14—Aluminium oxide or hydroxide from alkali metal aluminates
- C01F7/141—Aluminium oxide or hydroxide from alkali metal aluminates from aqueous aluminate solutions by neutralisation with an acidic agent
- C01F7/142—Aluminium oxide or hydroxide from alkali metal aluminates from aqueous aluminate solutions by neutralisation with an acidic agent with carbon dioxide
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G49/00—Compounds of iron
- C01G49/0018—Mixed oxides or hydroxides
- C01G49/0027—Mixed oxides or hydroxides containing one alkali metal
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G49/00—Compounds of iron
- C01G49/02—Oxides; Hydroxides
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B21/00—Obtaining aluminium
- C22B21/0015—Obtaining aluminium by wet processes
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B26/00—Obtaining alkali, alkaline earth metals or magnesium
- C22B26/10—Obtaining alkali metals
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B26/00—Obtaining alkali, alkaline earth metals or magnesium
- C22B26/20—Obtaining alkaline earth metals or magnesium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B34/00—Obtaining refractory metals
- C22B34/10—Obtaining titanium, zirconium or hafnium
- C22B34/12—Obtaining titanium or titanium compounds from ores or scrap by metallurgical processing; preparation of titanium compounds from other titanium compounds see C01G23/00 - C01G23/08
- C22B34/1236—Obtaining titanium or titanium compounds from ores or scrap by metallurgical processing; preparation of titanium compounds from other titanium compounds see C01G23/00 - C01G23/08 obtaining titanium or titanium compounds from ores or scrap by wet processes, e.g. by leaching
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/54—Improvements relating to the production of bulk chemicals using solvents, e.g. supercritical solvents or ionic liquids
Abstract
The invention provides a method for extracting valuable metal elements from coal gangue, which comprises the following steps: the method comprises the following steps of crushing, grinding, supercritical/subcritical water activation and classification of a hydrocyclone into an organic liquid phase and a slag phase, synthesizing carbon dioxide and water through a supercritical reaction in the organic liquid phase, reacting the carbon dioxide for subsequent sodium aluminate to obtain aluminum hydroxide, using the water for supplementing water through a shaking table, and obtaining enriched ore of carbon and silicon dioxide, alumina, silicate and ore containing a small amount of ferrotitanium through the shaking table in the slag phase. Separating and collecting carbon and silicon dioxide by electric separation, adding sodium carbonate and calcium carbonate into alumina, silicate and ore containing a small amount of ferrotitanium for roasting, and dissolving after roasting to obtain calcium silicate and calcium titanate slag which can be used as a coating, wherein a dissolving solution contains sodium aluminate, sodium ferrite and other substances, sodium hydroxide is added into the dissolving solution to generate iron hydroxide and sodium aluminate, the iron hydroxide can be used as the coating, and the sodium aluminate is introduced with carbon dioxide to generate aluminum hydroxide and is used as an inorganic flame retardant additive.
Description
Technical Field
The invention relates to the technical field of valuable substance extraction in coal gangue minerals, in particular to a method for extracting valuable metal elements from coal gangue.
Background
China is the largest coal producing country and consuming country in the world, and the national coal yield in 2019 is 38.5 hundred million t. The coal gangue is a solid waste generated in the production and processing processes of coal, is a coal symbiotic resource, and the production amount of the coal gangue accounts for 10-25% of the coal exploitation amount. The coal gangue comprises gangue discharged during roadway excavation of a coal mine, gangue stripped during open-pit coal mining and gangue discharged during separation processing, and is a mixture consisting of various ore rocks. The coal gangue yield in China is accumulated to exceed 50 hundred million t, the utilization rate of the coal gangue in China in 2019 is 70%, and the utilization rate of developed countries represented by British and America reaches 90%. The method shows that the current coal gangue comprehensive utilization degree is insufficient, the stacking amount is increased day by day, and the brought environmental problems are increased.
Landslide and debris flow phenomena can be generated sometimes when the coal gangue is stacked, and spontaneous combustion is generated when the coal gangue is stacked near 1/3 due to the existence of pyrite and carbonaceous materials, so that harmful and toxic gases are generated; the coal gangue pile generates a large amount of acid water or water carrying heavy metal ions through solarization, rain, weathering and decomposition, the underground water quality is damaged by infiltration, and the surface water is polluted and the environment is seriously polluted due to outflow. Therefore, it is imperative to explore methods for fully utilizing and high-value utilizing coal gangue, improve the comprehensive utilization rate and utilization value of coal gangue, and discuss the best way of saving coal gangue resources and protecting environment.
At present, coal gangue has multiple uses, such as power generation, building materials, soil improvement, water treatment agents and the like. If the elements are all recycled, the waste ore heap is changed into a product with practical value, so that the utilization rate of the coal gangue ore can be greatly improved, the value of the coal gangue mineral is increased, the waste is changed into valuable, and meanwhile, the coal gangue mineral contributes to environmental protection.
At present, the prior art for extracting useful resources such as silicon, aluminum and the like from coal porphyry serving as a raw material in industry mainly comprises the following steps: high-temperature calcination activation is carried out, and a concentrated acid leaching dissolution method is assisted. The method has the biggest problem that the coal gangue in the early stage needs to be subjected to high-temperature activation treatment, which means that the method has obvious energy consumption problem in the early stage treatment process of the coal gangue, and a large amount of residues and waste water can be generated in the acid leaching process, so that secondary pollution is easily caused. In addition, high-concentration acid-base treatment has high requirements on the corrosion resistance of equipment.
Disclosure of Invention
In view of the above, the present invention aims to provide a method for extracting valuable metal elements from coal gangue, which not only can achieve a rapid, efficient, economical and practical separation process, but also can realize the recovery of valuable elements from coal gangue and respond to the policy of national solid waste recycling.
In order to achieve the purpose, the invention provides a method for extracting valuable metal elements from coal gangue, which comprises the following steps:
crushing and grinding the coal gangue;
step two, performing activation treatment on the crushed and ground coal gangue under the condition of supercritical water or subcritical water;
step three, separating an organic liquid phase and a solid slag phase from the activated coal gangue through separation equipment;
step four, synthesizing carbon dioxide and water from the organic liquid phase through a supercritical reaction, wherein the carbon dioxide is used for the subsequent sodium aluminate reaction to be aluminum hydroxide, and the water is used for supplementing water to a shaking table;
screening the solid slag phase by a shaking table to obtain enrichment substances containing carbon and silicon dioxide, alumina, silicate and ilmenite;
step six, carrying out electric separation on the enriched substance containing carbon and silicon dioxide to obtain high-grade carbon and silicon dioxide;
seventhly, adding sodium carbonate and calcium carbonate into the alumina, silicate and ilmenite, roasting, and dissolving after roasting to obtain calcium silicate and calcium titanate slag;
step eight, adding sodium hydroxide into the dissolved solution to obtain ferric hydroxide and sodium aluminate;
and step nine, introducing carbon dioxide into the sodium aluminate to obtain the aluminum hydroxide.
Further, the particle size of the crushed and ground coal gangue in the first step is 2 micrometers to 2 millimeters.
Further, in the second step, activation treatment is carried out under the condition of supercritical water or subcritical water, the activation temperature is 250-400 ℃, the activation pressure is 8-20MPa, and the activation time is 0.1-3 h.
Further, the separation equipment in the third step is any one of a hydraulic cyclone, a solid-liquid separation centrifugal machine and a spiral chute.
Further, the temperature of the supercritical reaction in the fourth step is 373-500 ℃, and the pressure is 15-40 MPa.
Further, in the fifth step, the transverse angle of the shaking table is 1-5 degrees, and the longitudinal angle is 1-5 degrees.
Further, the method for separating the enriched substances of carbon and silica in the sixth step is to electrically select and separate the enriched substances by an electric separator.
Further, in the seventh step, sodium carbonate and calcium carbonate are added into the alumina, the silicate and the ore containing a small amount of ferrotitanium for roasting, wherein the roasting temperature is 300-1200 ℃.
Further, in the eighth step, the dissolving solution contains sodium aluminate and sodium ferrite.
The invention has the following beneficial effects:
1. the invention provides a method for extracting valuable metal elements from coal gangue, which comprises the steps of crushing and grinding the coal gangue, and mainly changing the granularity and microstructure of mineral powder particles in a mechanical mode; then activating under sub/supercritical conditions, reducing the chemical stability of the minerals, converting the crystal form into an amorphous state, and improving the activity; separating an organic liquid phase and a solid slag phase by strong centrifugal force of a hydrocyclone to realize primary separation of minerals; treating the organic liquid phase through supercritical reaction, wherein the supercritical water is decomposed into carbon dioxide and water by utilizing the strong decomposition capacity and organic matter dissolving capacity of the supercritical water; the concentrated ore of carbon and silicon dioxide, alumina, silicate and ore containing a small amount of ferrotitanium are obtained by the gravity separation of the table concentrator, and the gravity separation under the table concentrator is realized by utilizing different mineral specific gravities; the carbon and the silicon dioxide are separated and collected through electric separation, and the function is to realize electric separation by utilizing different mineral dielectric constants; adding sodium carbonate and calcium carbonate into alumina, silicate and ore containing a small amount of ferrotitanium for roasting, dissolving after roasting, and carrying out chemical reaction Na through alkali roasting2CO3+3A12O3·2SiO2→NaA1SiO4+Na2SiO3The calcium carbonate has similar action mechanism, and the final products comprise calcium silicate and calcium titanate slag, and sodium aluminate, sodium ferrite and the like are contained in the solution; adding sodium hydroxide into the solution to generate ferric hydroxide and sodium aluminate, wherein the sodium aluminate and the sodium hydroxide in the solution do not react, and the sodium ferrite and the sodium hydroxide chemically react to generate precipitate ferric hydroxide slag; introducing carbon dioxide into sodium aluminate to generate aluminum hydroxide, and carrying out chemical reaction on NaAlO2+CO2+2H2O＝Al(OH)3↓+NaHCO3. The method of the invention not only can achieve a rapid, efficient, economic and practical separation process, but also can realize the recovery of valuable elements in the coal gangue and respond to the policy of national solid waste recycling.
2. The invention provides a method for extracting valuable metal elements from coal gangue, which adopts a novel supercritical hydrothermal activation method as a main activation method, overcomes the defects of the traditional high-temperature activation acid leaching, has the advantages of low reaction temperature, high reaction rate, simple and easily-controlled process and the like, and has the current bottleneck of higher requirement on reaction equipment.
In addition to the objects, features and advantages described above, other objects, features and advantages of the present invention are also provided. The present invention will be described in further detail below with reference to the drawings.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic structural diagram of a preferred embodiment of the present invention;
Detailed Description
Embodiments of the invention will be described in detail below with reference to the drawings, but the invention can be implemented in many different ways, which are defined and covered by the claims.
Example 1
Table 1 shows the phase composition of the coal gangue minerals. As shown in figure 1, crushing and grinding coal gangue minerals to 74 microns, carrying out subcritical activation at 320 ℃ and 8MPa for 30min to obtain activated coal gangue minerals, dissociating most of the activated minerals, then classifying the minerals into an organic liquid phase and a slag phase by using a hydraulic cyclone, carrying out supercritical reaction on the separated organic liquid phase to obtain carbon dioxide and water, wherein the supercritical reaction temperature is 373 ℃ and the pressure is 22.5MPa, carrying out shaking table on the slag phase to obtain enriched ores of carbon and silicon dioxide, alumina, silicate and ores containing a small amount of ferrotitanium, and carrying out electric separation on the enriched ores of carbon and silicon dioxide to obtain high-grade carbon and silicon dioxide, wherein the carbon grade is 90%, and the silicon dioxide grade is 95%. Adding sodium carbonate and calcium carbonate into alumina, silicate and ore containing a small amount of ferrotitanium for roasting at 850 ℃, dissolving after roasting to obtain slag of calcium silicate and calcium titanate, adding sodium aluminate, sodium ferrite and other substances into the solution to generate ferric hydroxide and sodium aluminate, and introducing carbon dioxide into the sodium aluminate to generate aluminum hydroxide. Sodium aluminate, sodium ferrite and ferric hydroxide can be used as coating, and aluminum hydroxide can be used as inorganic flame-retardant additive.
Example 2
Table 1 shows the phase composition of the coal gangue minerals. As shown in figure 1, the gangue is crushed and ground to 36 microns, subcritical activation is carried out for 30min at 250 ℃ and 20MPa to obtain the activated gangue, most of minerals are dissociated after activation, then a hydraulic cyclone is used for classifying the activated gangue into an organic liquid phase and a slag phase, the separated organic liquid phase is subjected to supercritical reaction to obtain carbon dioxide and water, the supercritical reaction temperature is 373 ℃ and the pressure is 22.5MPa, the slag phase is subjected to a shaking table to obtain enriched ores of carbon and silicon dioxide, alumina, silicate and ores containing a small amount of ferrotitanium, and the enriched ores of carbon and silicon dioxide are subjected to electric separation to obtain high-grade carbon and silicon dioxide, wherein the carbon grade is 80% and the silicon dioxide grade is 90%. Adding sodium carbonate and calcium carbonate into alumina, silicate and ore containing a small amount of ferrotitanium for roasting at the roasting temperature of 750 ℃, dissolving after roasting to obtain slag of calcium silicate and calcium titanate, adding sodium aluminate, sodium ferrite and other substances into a dissolving solution to generate ferric hydroxide and sodium aluminate, and introducing carbon dioxide into the sodium aluminate to generate aluminum hydroxide. Sodium aluminate, sodium ferrite and ferric hydroxide can be used as coating, and aluminum hydroxide can be used as inorganic flame-retardant additive.
Example 3
Table 1 shows the phase composition of the coal gangue minerals. As shown in figure 1, the gangue is crushed and ground to 0.15 mm, subcritical activation is carried out for 30min at 400 ℃ and 15MPa to obtain activated gangue, most of minerals after activation are dissociated, then a hydraulic cyclone is used for classifying the activated gangue into an organic liquid phase and a slag phase, the separated organic liquid phase is subjected to supercritical reaction to be converted into carbon dioxide and water, the supercritical reaction temperature is 373 ℃ and the pressure is 22.5MPa, the slag phase is subjected to a shaking table to obtain enriched ores of carbon and silicon dioxide, alumina, silicate and ores containing a small amount of ferrotitanium, and the enriched ores of carbon and silicon dioxide are subjected to electric separation to obtain high-grade carbon and silicon dioxide, wherein the carbon grade is 75%, and the silicon dioxide grade is 76%. Adding sodium carbonate and calcium carbonate into alumina, silicate and ore containing a small amount of ferrotitanium for roasting at the roasting temperature of 950 ℃, dissolving after roasting to obtain slag of calcium silicate and calcium titanate, adding sodium aluminate, sodium ferrite and other substances into a dissolving solution to generate ferric hydroxide and sodium aluminate, and introducing carbon dioxide into the sodium aluminate to generate aluminum hydroxide. Sodium aluminate, sodium ferrite and ferric hydroxide can be used as coating, and aluminum hydroxide can be used as inorganic flame-retardant additive.
TABLE 1 phase composition of coal gangue minerals
| Element(s) | Ca | SiO2 | P | S | Mg | K | Na | Fe | Al2O3 | C |
| Content% | ＜0.1 | 52.7 | ＜0.1 | 0.42 | ＜0.1 | 0.18 | ＜0.1 | 22.91 | 22.91 | 12 |
Comparative example 1: (without supercritical activation step)
Table 1 shows the phase composition of the coal gangue minerals. Crushing and grinding the coal gangue ore to 74 microns, directly using a hydraulic cyclone without activation, classifying the coal gangue ore into an organic liquid phase and a slag phase, carrying out supercritical reaction on the separated organic liquid phase to obtain carbon dioxide and water, wherein the supercritical reaction temperature is 373 ℃ and the pressure is 22.5MPa, carrying out table sorting on the slag phase to find that enriched ore of carbon and silicon dioxide, alumina and silicate are difficult to separate, most of the enriched ore exists in a continuous state, the carbon grade obtained by carrying out subsequent electric separation on the enriched ore is only 30% accompanied by a large amount of other impurities, the silicon dioxide grade is only 25%, most of the enriched ore and alumina are not separated, roasting the table sorted matter, wherein the roasting temperature is 850 ℃, dissolving the enriched ore after roasting is carried out, pure calcium silicate and calcium titanate slag is not obtained, a dissolving solution is also mixed with various ions, and adding sodium hydroxide cannot obtain pure ferric hydroxide precipitate. The process is completely obstructed, effective separation cannot be carried out, and valuable elements are difficult to separate.
Comparative example 2 (over-temperature):
table 1 shows the phase composition of the coal gangue minerals. Crushing and grinding the coal gangue ore to 74 microns, performing subcritical activation for 30min at 450 ℃ and 8MPa to obtain activated coal gangue ore, then classifying the coal gangue ore into an organic liquid phase and a slag phase by using a hydraulic cyclone, performing supercritical reaction on the separated organic liquid phase to obtain carbon dioxide and water, performing supercritical reaction at 373 ℃ and under 22.5MPa, obtaining enriched ore of carbon and silicon dioxide, alumina, silicate and ore containing a small amount of ferrotitanium from the slag phase by using a shaking table, and performing electric separation on the enriched ore of carbon and silicon dioxide to obtain high-grade carbon and silicon dioxide, wherein the carbon grade is 95%, and the silicon dioxide grade is 95%. Adding sodium carbonate and calcium carbonate into alumina, silicate and ore containing a small amount of ferrotitanium for roasting at 850 ℃, dissolving after roasting to obtain slag of calcium silicate and calcium titanate, adding sodium aluminate, sodium ferrite and other substances into the solution to generate ferric hydroxide and sodium aluminate, and introducing carbon dioxide into the sodium aluminate to generate aluminum hydroxide. Sodium aluminate, sodium ferrite and ferric hydroxide can be used as coating, and aluminum hydroxide can be used as inorganic flame-retardant additive. The silicon-aluminum element separation ratio under the high-temperature condition is good, the electric separation effect is good, but the improvement effect is not obvious compared with the example-I activation condition, and the analysis reason is as follows: when the temperature reaches 373 ℃, the liquid water is converted into water in a supercritical state, the purpose of separating elements such as silicon and aluminum is achieved by utilizing the strong decomposition capacity of supercritical water, minerals such as aluminosilicate are dissociated, and then if the temperature is continuously increased, the water still keeps the supercritical state, and the dissociation effect of the minerals is not greatly improved. Therefore, the improvement of the sorting effect is not obvious, and the temperature is kept below 400 ℃ in practical application from the viewpoint of energy conservation.
Comparative example 3: (too low temperature)
Table 1 shows the phase composition of the coal gangue minerals. Crushing and grinding the coal gangue ore to 74 microns, performing subcritical activation at 80 ℃ and 20MPa for 30min to obtain activated coal gangue ore, classifying the coal gangue ore into an organic liquid phase and a slag phase by using a hydraulic cyclone, classifying the organic liquid phase and the slag phase by using the hydraulic cyclone, converting the separated organic liquid phase into carbon dioxide and water by supercritical reaction at 373 ℃ and under 22.5MPa, obtaining enriched ore of carbon and silicon dioxide, alumina, silicate and the like and a small amount of ilmenite from the slag phase by using a shaking table, and electrically selecting the enriched ore of carbon and silicon dioxide to obtain carbon and silicon dioxide, wherein the carbon grade is 55%, the silicon dioxide grade is 50%, minerals such as associated aluminate with more impurities in the silicon dioxide are not fully dissociated, and a large amount of silicon dioxide is associated in the silicate and the ore containing a small amount of ilmenite. Therefore, the temperature has great influence on the activation, the activation effect is not obvious only by increasing the pressure at low temperature, the extracted substance has more accompanying impurities, and the utilization value is low. For analysis reasons, the stability of mineral crystals in the coal gangue is high, the activation temperature is low, the silicon-aluminum connection is not easy to open, most minerals are not dissociated, and the minerals sorted by a shaking table are impure.
Comparative example 4: (too low a pressure)
Table 1 shows the phase composition of the coal gangue minerals. Crushing and grinding the coal gangue ore to 74 microns, performing subcritical activation at 350 ℃ and 3MPa for 30min to obtain activated coal gangue ore, classifying the coal gangue ore into an organic liquid phase and a slag phase by using a hydraulic cyclone, classifying the organic liquid phase and the slag phase by using the hydraulic cyclone, converting the separated organic liquid phase into carbon dioxide and water by supercritical reaction at 373 ℃ and under 22.5MPa, obtaining enriched ore of carbon and silicon dioxide, alumina, silicate and ore containing a small amount of ferrotitanium from the slag phase by using a table concentrator, obtaining enriched ore of carbon and silicon dioxide, alumina, silicate and the like from the slag phase by using the table concentrator, electrically selecting the enriched ore of carbon and silicon dioxide to obtain carbon and silicon dioxide, wherein the carbon grade is 60%, the silicon dioxide grade is 52%, the associated impurities are more and are not separated, and separating mineral impurities. The effect is not greatly improved after the high-temperature low-pressure activation, the extracted substances have more impurities, and the further separation is difficult. It shows that the pressure has great influence on the activation, and the activation effect is not obvious by only increasing the temperature under low pressure. The chemical stability of the minerals in the coal gangue is high for analysis reasons, although carbon and aluminosilicate are opened at high temperature, the pressure is not enough, the aluminum and silicon are difficult to be further separated, the acting force cannot meet the requirement of converting the crystal structure of the aluminosilicate minerals, the activation degree is low, and the separation effect is not obvious.
Comparative example 5: (excessive pressure)
Table 1 shows the phase composition of the coal gangue minerals. Crushing and grinding the coal gangue ore to 74 microns, performing supercritical activation at 350 ℃ and 25MPa for 30min to obtain activated coal gangue ore, dissociating most of the activated ore, then classifying the activated coal gangue ore into an organic liquid phase and a slag phase by using a hydraulic cyclone, performing supercritical reaction on the separated organic liquid phase to obtain carbon dioxide and water, performing supercritical reaction at 373 ℃ and under a pressure of 22.5MPa, obtaining enriched ore of carbon and silicon dioxide, alumina, silicate and ore containing a small amount of ferrotitanium from the slag phase by using a shaking table, and performing electric separation on the enriched ore of carbon and silicon dioxide to obtain high-grade carbon and silicon dioxide, wherein the carbon grade is 95%, and the silicon dioxide grade is 95%. Adding sodium carbonate and calcium carbonate into alumina, silicate and ore containing a small amount of ferrotitanium for roasting at 850 ℃, dissolving after roasting to obtain slag of calcium silicate and calcium titanate, adding sodium aluminate, sodium ferrite and other substances into the solution to generate ferric hydroxide and sodium aluminate, and introducing carbon dioxide into the sodium aluminate to generate aluminum hydroxide. Sodium aluminate, sodium ferrite and ferric hydroxide can be used as coating, and aluminum hydroxide can be used as inorganic flame-retardant additive. The extraction effect of each element under the supercritical condition is obvious and the separation is relatively obvious, but the promotion effect is not obvious compared with that under the condition of example 2, and the analysis reason is that: when the pressure reaches 22.5MPa, the liquid water is converted into water in a supercritical state, the purpose of separating elements such as silicon and aluminum is achieved by utilizing the strong decomposition capacity of supercritical water, minerals such as aluminosilicate are dissociated, and then if the pressure is continuously increased, the water still keeps the supercritical state, and the dissociation effect of the minerals is not greatly improved. Therefore, the improvement on the sorting effect is not obvious, and the pressure is kept below 22.5MPa in practical application from the viewpoint of protecting equipment.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. A method for extracting valuable metal elements from coal gangue is characterized by comprising the following steps:
crushing and grinding the coal gangue;
step two, performing activation treatment on the crushed and ground coal gangue under the condition of supercritical water or subcritical water;
step three, separating an organic liquid phase and a solid slag phase from the activated coal gangue through separation equipment;
step four, synthesizing carbon dioxide and water from the organic liquid phase through a supercritical reaction, wherein the carbon dioxide is used for the subsequent sodium aluminate reaction to be aluminum hydroxide, and the water is used for supplementing water to a shaking table;
screening the solid slag phase by a shaking table to obtain enrichment substances containing carbon and silicon dioxide, alumina, silicate and ilmenite;
step six, carrying out electric separation on the enriched substance containing carbon and silicon dioxide to obtain high-grade carbon and silicon dioxide;
seventhly, adding sodium carbonate and calcium carbonate into the alumina, silicate and ilmenite, roasting, and dissolving after roasting to obtain calcium silicate and calcium titanate slag;
step eight, adding sodium hydroxide into the dissolved solution to obtain ferric hydroxide and sodium aluminate;
and step nine, introducing carbon dioxide into the sodium aluminate to obtain the aluminum hydroxide.
2. The method for extracting valuable metal elements from coal gangue as claimed in claim 1, wherein the particle size of the coal gangue crushed and ground in the first step is 2 μm to 2 mm.
3. The method as set forth in claim 1, wherein the activation treatment is performed under supercritical water or subcritical water conditions at an activation temperature of 250-.
4. The method for extracting valuable metal elements from coal gangue as claimed in claim 1, wherein the separation equipment in the third step is any one of a hydrocyclone, a solid-liquid separation centrifuge and a spiral chute.
5. The method as claimed in claim 1, wherein the supercritical reaction is carried out at 373-500 ℃ and 15-40 MPa.
6. The method for extracting valuable metal elements from coal gangue as claimed in claim 1, wherein the horizontal angle of the table in the fifth step is 1-5 ° and the vertical angle is 1-5 °.
7. The method for extracting valuable metal elements from coal gangue as claimed in claim 1, wherein the separation method of the enriched substances of carbon and silicon dioxide in the sixth step is electro-mechanical separation.
8. The method as claimed in claim 1, wherein the alumina, the silicate and the ore containing a small amount of ferrotitanium are calcined by adding sodium carbonate and calcium carbonate, and the calcination temperature is 300-1200 ℃.
9. The method for extracting valuable metal elements from coal gangue as claimed in claim 1, wherein in step eight, the dissolving solution contains sodium aluminate and sodium ferrite.
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