CN107986281B - Utilization method of coal gangue waste - Google Patents
Utilization method of coal gangue waste Download PDFInfo
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- CN107986281B CN107986281B CN201711205954.6A CN201711205954A CN107986281B CN 107986281 B CN107986281 B CN 107986281B CN 201711205954 A CN201711205954 A CN 201711205954A CN 107986281 B CN107986281 B CN 107986281B
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- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
Abstract
The invention relates to a comprehensive utilization method of waste cathode carbon blocks by matching coal gangue waste with aluminum electrolysis industry. The method comprises the following specific steps: crushing coal gangue and waste cathode carbon blocks into powder, drying, mixing according to a certain proportion, removing alkaline soluble impurities in the mixed materials by using strong alkali liquor, washing the mixed materials to be neutral by using hot water, drying, heating to 1400-1700 ℃ in an inert or reducing atmosphere, preserving the heat for a period of time to obtain mixed powder containing silicon carbide, oxidizing and burning the powder in an oxidizing atmosphere to remove residual carbon powder, dispersing the obtained powder in hydrofluoric acid to remove residual silicon dioxide, cleaning and drying to obtain silicon carbide powder. The silicon carbide product obtained by the invention has high purity, small grain size and extremely high industrial application value. Meanwhile, the industrial solid waste coal gangue and the waste cathode carbon blocks are used as raw materials, so that the method has positive significance in reducing waste pollution, protecting the environment and recycling the resources.
Description
The technical field is as follows:
the invention relates to a utilization method of coal gangue waste, in particular to the technical field of harmless treatment and resource recycling of waste cathode carbon blocks in the coal gangue waste combined aluminum electrolysis industry.
Background art:
the coal gangue is rock mixed in coal-series stratum, and a black rock which has lower carbon content and is harder than coal and is associated and symbiotic with coal bed in the coal forming process is a mixture consisting of inorganic matter and a small amount of organic matter. The gangue accumulation in China reaches 70 hundred million t, and the land occupation is 70km2And increases at a rate of 1.5 million t of annual emissions. The comprehensive utilization of the coal gangue is less than 15 percent, and the rest coal gangue is naturally and loosely stacked around a mine mostly in a conical or valley dumping mode. The waste slag is one of the largest waste slag discharged in China. The large stacking of the coal gangue can cause the following influences on the surrounding environment:
(1) occupies a large amount of land resources. As the waste of coal mining, the coal gangue can be stacked around the mining area by enterprises to form a coal gangue mountain. According to incomplete statistics, the accumulated coal gangue in China is about 45 hundred million tons by 2015, more than 2600 coal gangue hills with large scale occupy more than 20 ten thousand mu, and the coal gangue hills are industrial wastes which are second to the construction wastes in China in yield and accumulation.
(2) And the environment is polluted. The long-term stacked coal gangue can be changed into fine and loose dust particles under the weathering effect, and the fine and loose dust particles are easily blown up by strong wind, so that a sand-dust weather is formed, and the air quality is reduced. In addition, the coal gangue contains harmful metal elements such as Cr, Ni, Cu, Pb and the like, and can enter soil, rivers, lakes and underground water along with rainfall after being washed by rainwater, so that soil and water are polluted.
(3) Posing a threat to the security of the nearby areas. The risk of collapse and slippage of a large amount of accumulated coal gangue exists, and accidents are easy to happen under the action of overlarge stacking gradient, strong precipitation and other external forces of the coal gangue. The coal gangue contains part of organic carbon and other combustible substances, and can be spontaneously combusted under the action of self pressure and weathering after being stacked in the open air for a long time, and CO and SO can be discharged from the spontaneous combustion of the coal gangue2、NOxAnd when harmful gases are used, the spontaneous combustion time of a large coal gangue pile is as long as more than ten years, and the large coal gangue pile has great harm to nearby areas.
At present, the utilization approaches of coal gangue mainly focus on the following aspects:
(1) and generating power by using the coal gangue. The coal gangue contains part of organic carbon and has a certain calorific value. The high-carbon coal gangue, such as coal preparation coal gangue, has higher calorific value, is mixed with coal slime after being crushed, and can be used as fuel of a fluidized bed boiler of a power plant. The coal gangue lime after the combustion of the coal gangue can be used as a cement admixture to produce building materials.
(2) Producing building material products. The building materials such as cement, clay brick, ceramic and the like are building material products obtained by high-temperature treatment of mixture of aluminosilicate and the like, and the coal gangue contains rich SiO2、Al2O3The coal gangue contains partial carbon, so that partial heat value can be provided in the high-temperature firing process, the energy consumption is saved, and the production cost is reduced. The coal amount used for producing building material products in China accounts for 12% of the total utilization amount of the coal gangue.
(3) And backfilling and filling pits in the collapse area to build a road. The method is suitable for coal gangue with low organic matter content and high mechanical strength, is a main way for utilizing the coal gangue at present, and the utilization amount of the coal gangue accounts for 56 percent of the total utilization amount of the coal gangue. The method has the characteristics of simple and easy process, wide application range, large utilization amount and the like, but secondary pollution and the characteristics of the coal gangue need to be considered in practical application, and the purpose of adjusting the local conditions is achieved.
The above dominant coal gangue utilization approaches also have the disadvantages of environmental pollution, low utilization rate, low additional value, small application range and the like, and the current trend is to explore a new coal gangue recycling approach for reducing or even eliminating the harm of coal gangue and realizing the recycling of waste and sustainable development of society.
Disclosure of Invention
Aiming at the problems that the prior coal gangue is difficult to be effectively utilized with high quality and the like, the utilization method of the coal gangue waste with high product economic value and environment-friendly process is provided.
The invention relates to a utilization method of coal gangue waste, which comprises the following steps:
step one
According to the mass ratio, the mixture A: putting the mixture A into alkali liquor at a ratio of 1:5-10, stirring at a temperature of more than 70-90 ℃ for at least 4h, filtering, and cleaning filter residue; drying the cleaned filter residue to obtain standby filter residue; the mixture A is prepared from coal gangue waste and waste cathode carbon blocks in a mass ratio of coal gangue waste: waste cathode carbon blocks are less than or equal to 5; in the alkali liquor, the concentration of hydroxide radicals is more than or equal to 3 mol/L;
step two
Placing the filter residue obtained in the step one in a sintering furnace; heating to 1400-1700 ℃ in inert or reducing atmosphere, preferably 1450-1480 ℃, preserving heat for 3-10h, then cooling to 800-1000 ℃, preserving heat in oxygen-containing atmosphere until zero-valent carbon is completely oxidized, and obtaining the silicon carbide powder after acid cleaning.
When the method is applied to industry, the coal gangue waste material and the cathode carbon block are respectively crushed; sieving with 300 mesh sieve, preferably 400 mesh sieve; according to the mass ratio, the coal gangue waste material: taking undersize products from a cathode carbon block (1: 0.5-2), preferably 1:1-2, and uniformly mixing; a mixture a is obtained.
In the second step, the filter residue obtained in the first step is placed in a quartz material container and is placed in a sintering furnace.
When the method is applied industrially, in the second step, the temperature is reduced to 800-1000 ℃, and the zero-valent carbon can be completely oxidized after heat preservation for 3-5 hours in oxygen-containing atmosphere. At this time, if the holding time is prolonged, the yield of the product SiC is affected to some extent.
The invention relates to a method for utilizing coal gangue waste, wherein waste cathode carbon blocks are waste cathode carbon blocks in the aluminum electrolysis industry.
The invention relates to a utilization method of coal gangue waste, and the coal gangue waste SiO250 wt% or more of Al2O3Less than or equal to 30 wt%. In the waste cathode carbon blocks, the content of carbon is more than or equal to 60 wt%. As a preference; in the waste cathode carbon blocks, the carbon content is more than or equal to 60 wt% and less than or equal to 80 wt%.
The invention relates to a utilization method of coal gangue waste, comprising the following steps of: putting the mixture A obtained in the step one into alkali liquor at a ratio of 1:5-10, stirring for 4-10h at the temperature of 70-90 ℃, filtering, and cleaning filter residues; drying the cleaned filter residue to obtain the standby filter residue.
Preferably, in the first step, after filtration, the coal gangue waste is washed with hot water at 70-90 ℃, vacuum filtration is carried out for a plurality of times until the pH value of the washed liquid is 6.8-7.2, and then the washed liquid is dried for 8-24h at the temperature of 100-300 ℃ to obtain the standby filter residue. In the first step, the filter residue after cleaning is dried for 8-24h at 100-300 ℃. Drying for 8-24h at 100-300 ℃ not only can remove water, but also can activate the coal gangue waste.
The invention relates to a utilization method of coal gangue waste, wherein in the step one, the stirring speed is 100r/min-300 r/min.
According to the utilization method of the coal gangue waste, the concentration of hydroxyl in the alkali liquor is preferably 3-5 mol/L. The alkali solution is at least one of potassium hydroxide solution and sodium hydroxide solution. The alkali liquor can be recycled.
In the second step of the utilization method of the coal gangue waste, the acid used for acid cleaning is hydrofluoric acid, and the concentration is 4-6 mol/L.
According to the utilization method of the coal gangue waste, the purity of the obtained silicon carbide powder is more than or equal to 93%. After the optimized process treatment, the purity of the obtained silicon carbide powder is more than or equal to 98 percent.
According to the utilization method of the coal gangue waste, the granularity of the obtained silicon carbide powder is less than or equal to 15 micrometers. After the treatment of the optimized process, the granularity of the obtained silicon carbide powder is mainly distributed between 400 and 800 nm.
Has the advantages that:
the invention tries to use the coal gangue waste and the cathode carbon block as raw materials for the first time; and through the synergistic effect of the condition parameters, micron-level or even nano-level SiC is prepared. The method uses an alkaline leaching-hot washing method, has a certain activation effect on silicon dioxide in the coal gangue, and can obtain activated porous carbon source by alkaline leaching, thereby providing necessary conditions for obtaining micron-level or even nano-level high-quality silicon carbide. Meanwhile, the leaching temperature of the waste cathode carbon blocks (particularly the cathode carbon blocks used in the aluminum electrolysis process) is strictly controlled mainly to provide a porous carbon source with proper pore size and pore shape. The alkaline leaching is preferably controlled for 4 to 10 hours, with the aim of obtaining nanoscale powders with a narrow particle size distribution.
The invention has the following obvious advantages:
1. high-purity carbon powder and silicon dioxide powder are not used, so that the production cost of the silicon carbide product can be effectively reduced.
2. The method uses the dangerous solid waste of aluminum electrolysis enterprises, namely the waste cathode carbon block, and the solid waste of coal production enterprises, namely the coal gangue as raw materials, not only can synthesize the silicon carbide powder with higher purity, but also solves the problems of environmental pollution and resource waste of industrial solid waste, creates industrial value when carrying out innocent treatment, and has great significance for environmental protection.
3. The silicon carbide powder prepared by the method has wide application, can be used for abrasive tools, high-temperature-resistant and corrosion-resistant materials, electronic appliances and the like, and has great industrial application value.
Detailed description of the invention
In the examples and comparative examples, the waste coal gangue material used was SiO261 wt% C content 23 wt%, other impurities including Al2O3、MgO、Fe2O3(ii) a The waste cathode carbon blocks comprise the following components: c content 75 wt%, F content 20 wt%, impurities mainly SiO2And sodium silicate.
Example 1
A utilization method of coal gangue waste comprises the following specific steps:
1) respectively crushing and grinding the coal gangue waste and the waste cathode carbon blocks in the aluminum electrolysis industry to-400 meshes, drying for 24 hours at the temperature of 300 ℃, and after the internal water is completely evaporated, mixing the coal gangue with the waste cathode carbon blocks in the mass ratio: uniformly mixing the cathode carbon blocks in a ratio of 1:1 to obtain a mixed powder material;
2) mixing the mixed powder material obtained in the previous step according to the following powder: dispersing the mixed powder in NaOH alkaline solution with the concentration of 4mol/L according to the mass ratio of 1:10, and stirring at the temperature of 90 ℃ for 10 hours at the stirring speed of 300 r/min;
3) carrying out solid-liquid separation on the obtained solid-liquid mixture through suction filtration, washing the obtained mixed powder after suction filtration with hot water at 90 ℃, carrying out vacuum suction filtration repeatedly until the pH value of the washed liquid reaches 7 to obtain mixed powder after impurity removal, drying for 24h at the temperature of 300 ℃, and till the water in the mixed powder is completely evaporated;
4) and adding the dried mixed powder into a quartz crucible, heating to 1600 ℃ at the heating rate of 3 ℃/min under the protective atmosphere of nitrogen, preserving the heat for 3h, then cooling to 1000 ℃, preserving the heat for 3h under the atmosphere of air, burning ash, and washing with 6mol/L hydrofluoric acid to obtain the silicon carbide powder with the purity higher than 98 percent. The granularity of the silicon carbide powder is mainly distributed between 400 and 600 nm.
Example 2
A utilization method of coal gangue waste comprises the following specific steps:
1) respectively crushing, grinding and screening the coal gangue waste and the waste cathode carbon blocks in the aluminum electrolysis industry to obtain 300-400-mesh powder, drying for 12 hours at the temperature of 150 ℃, and after the internal water is completely evaporated, mixing the coal gangue with the raw materials in percentage by mass: uniformly mixing the cathode carbon blocks in a ratio of 1:0.5 to obtain a mixed powder material;
2) mixing the mixed powder material obtained in the previous step according to the following powder: dispersing the mixed powder in NaOH alkaline solution with the concentration of 3mol/L according to the mass ratio of 1:5, and removing Al2O3Stirring for 5h at 70 ℃ for impurities at the stirring speed of 100 r/min;
3) carrying out solid-liquid separation on the obtained solid-liquid mixture through suction filtration, washing the obtained mixed powder after suction filtration with hot water at 70 ℃, carrying out vacuum suction filtration repeatedly until the pH value of the washed liquid reaches 7 to obtain mixed powder after impurity removal, drying for 8h at the temperature of 100 ℃, and till the water in the mixed powder is completely evaporated;
4) and adding the dried mixed powder into a quartz crucible, heating to 1400 ℃ at the heating rate of 5 ℃/min in the protective atmosphere of nitrogen, preserving the heat for 10 hours, then cooling to 800 ℃, preserving the heat for 5 hours in the atmosphere of air, burning off carbon residue, and removing silicon dioxide by using 4mol/L hydrofluoric acid to obtain the silicon carbide powder with the purity of 97.5%. The granularity of the silicon carbide powder is mainly distributed between 400 and 600 nm.
Example 3
A utilization method of coal gangue waste comprises the following specific steps:
1) respectively crushing and grinding the coal gangue waste and the waste cathode carbon blocks in the aluminum electrolysis industry to-300 meshes, drying for 8 hours at the temperature of 100 ℃, and after all the water in the coal gangue waste and the waste cathode carbon blocks in the aluminum electrolysis industry is evaporated, mixing the coal gangue waste and the waste cathode carbon blocks in mass ratio: uniformly mixing the cathode carbon blocks in a ratio of 1:2.0 to obtain a mixed powder material;
2) mixing the mixed powder material obtained in the previous step according to the following powder: dispersing the mixed powder in NaOH alkaline solution with the concentration of 5mol/L according to the mass ratio of 1:8, and removing Al2O3Stirring impurities at 80 ℃ for 8 hours at the stirring speed of 200 r/min;
3) carrying out solid-liquid separation on the obtained solid-liquid mixture through suction filtration, washing the obtained mixed powder after suction filtration with hot water at 80 ℃, carrying out vacuum suction filtration repeatedly until the pH value of the washed liquid reaches 7 to obtain mixed powder after impurity removal, and drying for 12h at the temperature of 200 ℃ to obtain standby filter residue;
4) and adding the dried mixed powder into a quartz crucible, heating to 1550 ℃ at the heating rate of 4 ℃/min in the mixed atmosphere of hydrogen and nitrogen, preserving the heat for 6h, then cooling to 850 ℃, preserving the heat for 5h in the air atmosphere, burning ash to remove residual carbon powder, cooling to normal temperature, and removing residual silicon dioxide by 6mol/L hydrofluoric acid to obtain silicon carbide powder with the purity of 96%. The granularity of the silicon carbide powder is mainly distributed between 500 and 800 nm.
Comparative example 1
The other conditions are the same as those of the embodiment 1, except that 99 percent of carbon powder is adopted to replace the waste cathode carbon blocks; the purity of the product obtained was 98%, but the particle size of the product was 20-85 μm. The cost of producing a finished product of equal quality is about 1.2 times that of example 1.
Comparative example 2
Other conditions are uniform, and the embodiment 1 is consistent, except that the waste coal gangue is replaced by silicon dioxide with the purity of 99 percent, and the waste cathode carbon blocks are replaced by carbon powder with the purity of 99 percent; not only alkaline leaching treatment; the purity of the obtained product is more than 98 percent, but the particle size of the product is 100-150 microns. The cost of producing a finished product with equal quality is 2 times of that of the example 1.
Comparative example 3
Other conditions are uniform, and the difference is that the temperature of the alkaline leaching in the step 2 is normal temperature; the resulting product had a particle size distribution of 180 microns for D90, 95 microns for D50 and 10 microns for D10. And the purity of the obtained product is 86%.
Comparative example 4
Other conditions are uniform, and the difference is that the alkali concentration in the second step is 1 mol/L; the resulting product had a particle size distribution of 210 microns for D90, 115 microns for D50, and 18 microns for D10.
Claims (7)
1. A utilization method of coal gangue waste is characterized by comprising the following steps:
step one
According to the mass ratio, the mixture A: putting the mixture A into an alkali liquor at a ratio of 1:5-10, stirring for 4-10h at 70-90 ℃, filtering, washing the filter residue with hot water at 70-90 ℃, vacuum-filtering, repeating for many times until the pH value of the washed liquid is 6.8-7.2, and drying for 8-24h at 100-300 ℃ to obtain a standby filter residue; in the alkali liquor, the concentration of hydroxide radical is 3-5 mol/L; the stirring speed is 100r/min-300 r/min; the mixture A is prepared from coal gangue waste and waste cathode carbon blocks in a mass ratio of coal gangue waste: waste cathode carbon blocks are less than or equal to 5;
step two
Placing the filter residue obtained in the step one in a sintering furnace; heating to 1450-1480 ℃ in inert or reducing atmosphere, preserving heat for 3-10h, then cooling to 800-1000 ℃, preserving heat in oxygen-containing atmosphere until zero-valent carbon is completely oxidized, and obtaining the silicon carbide powder after acid washing.
2. The method for utilizing coal gangue waste material as defined in claim 1, wherein: the waste cathode carbon blocks are waste cathode carbon blocks in the aluminum electrolysis industry.
3. The method for utilizing coal gangue waste material as defined in claim 1, wherein: the coal gangue waste material SiO250 wt% or more of Al2O3Less than or equal to 30 wt%, and the carbon content in the waste cathode carbon blocks is more than or equal to 60 wt% and less than or equal to 80 wt%.
4. The method for utilizing coal gangue waste material as defined in claim 1, wherein: drying the cleaned filter residue at 100-300 deg.C for 8-24 h.
5. The method for utilizing coal gangue waste material as defined in claim 1, wherein: the alkali liquor is at least one of potassium hydroxide solution and sodium hydroxide solution.
6. The method for utilizing coal gangue waste material as defined in claim 1, wherein: in the third step, the acid used for acid cleaning is hydrofluoric acid, and the concentration is 4-6 mol/L.
7. The method for utilizing coal gangue waste material as defined in claim 1, wherein: the purity of the obtained silicon carbide powder is more than or equal to 93 percent; the granularity of the obtained silicon carbide powder is less than or equal to 15 microns.
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| CN104140121A (en) * | 2013-05-09 | 2014-11-12 | 中国科学院过程工程研究所 | Method for preparing sodium aluminate solution from coal-series kaolinite or coal gangue used as raw material |
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