CN110003965B

CN110003965B - Method for preparing superfine clean coal by combining ball milling pretreatment and chemical method

Info

Publication number: CN110003965B
Application number: CN201910384240.9A
Authority: CN
Inventors: 肖劲; 唐雷; 仲奇凡; 张振华
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2019-05-09
Filing date: 2019-05-09
Publication date: 2021-04-20
Anticipated expiration: 2039-05-09
Also published as: CN110003965A

Abstract

The invention discloses a method for preparing superfine clean coal by combining ball milling pretreatment and a chemical method, which comprises the following steps: (1) crushing anthracite, and roasting in a protective atmosphere to obtain coal particles; adding a dispersing agent into the obtained coal particles, controlling the grading of grinding balls, performing ball milling, and drying to obtain superfine coal powder; (2) mixing the superfine pulverized coal and a surfactant, adding the mixture into the mixed immersion liquid of acid and fluoride salt, filtering, washing and drying the mixture after heating and leaching to obtain the superfine clean anthracite powder. The method can obtain the superfine coal powder with small particle size and narrow distribution interval by removing the volatile components of the crushed anthracite in the protective atmosphere and cooperating with the ball milling pretreatment, and the purity of the obtained superfine coal powder is not lower than 99.5 wt% after impurity removal.

Description

Method for preparing superfine clean coal by combining ball milling pretreatment and chemical method

Technical Field

The invention relates to a method for preparing superfine clean coal by combining ball milling pretreatment and a chemical method, belonging to the technical field of preparation of functional carbon powder materials.

Technical Field

Clean coal is a coal product with high added value, can be used as high-calorific-value fuel to replace diesel oil and natural gas to be used in internal combustion engines, gas turbines, aviation turbine engines and the like, and for reducing the abrasion and slag discharge influence of pumps, nozzles, pistons and turbine blades, the ash content of ultra-pure coal is generally required to be below 1.0% for the internal combustion engine fuel; on the other hand, the clean coal can also be used for preparing high-quality high-performance carbon materials, such as carbon fiber composite materials, graphite electrodes, new energy materials and other fields. Therefore, the preparation of clean coal is a necessary trend of fine processing and additional value improvement of coal, and research on mineral dissociation and clean coal preparation technology is developed to obtain a novel high-energy fuel and a high-quality carbon material, so that the preparation method has wide application prospect and potential huge economic and social benefits. As a new energy material serving as a new industry, the industry is facing explosive growth along with the increasing of the supporting policy of the new energy industry in recent years. The energy storage and conversion device determines the key to the development of new energy industry, and the key to the energy storage and conversion device is the material. The battery cathode material is usually made of carbon material, and the requirements on the particle size and purity of the material are very strict for new energy materials. The coal has rich reserves, high carbon content and low price, and is an important raw material for researching and preparing new energy materials at present. However, because of inherent defects of coal, the coal can not be directly used generally, and the coal needs to be purified to ensure that the purity of the coal reaches more than 99.5 percent, and meanwhile, the granularity of the coal is required to be less than 30 um.

Patent CN103537355A discloses a system and a method for preparing ultrafine coal powder, which utilizes a fine powder pulverizing system and an ultrafine powder separating system to realize two parts of fine powder preparation and ultrafine powder separation and extraction. And the superfine powder is separated and extracted by a classifier, a cyclone separator and a pulse bag dust collector to obtain superfine coal powder with different grades. However, the superfine coal powder in the scheme is a product obtained by screening separation, is not full-component superfine coal powder, and is only ground once, so that the coarse particles in the superfine coal powder have a large proportion.

Patent CN107626438A discloses a process for preparing ultra-pure coal by physical method of anthracite, which comprises the following steps: and (4) grinding the anthracite, sieving the ground anthracite by a 200-mesh sieve to obtain a coal sample, and performing a flotation test on the coal sample to obtain flotation clean coal. And adding sodium silicate into the flotation cleaned coal, and performing step-by-step release to obtain the step-by-step released cleaned coal. Pouring the mixture into a spiral chute after uniformly stirring to obtain spiral separated clean coal; wherein, the middlings obtained after the primary spiral separation are returned to the spiral chute for the secondary spiral separation, sodium silicate and water are added into the spiral separation clean coal, kerosene is added after stirring for a period of time, stirring is continued for a period of time, and the oversize products are the ultra-pure coal after sieving and drying. The obtained ultrapure coal has coarse particles and high impurity content (ash content < 2%).

Patent CN107674725A discloses a process for preparing ultra-pure coal by anthracite chemical method, which comprises the following steps: 1) taking anthracite, grinding and sieving by a 200-mesh sieve to obtain a coal sample; 2) adding NaOH into the coal sample, roasting for 12h at 200 ℃, and filtering to obtain primary coal; 3) and adding 5% HCl into the primary coal, stirring for 1h at room temperature, filtering and drying to obtain the ultra-pure coal. The patent can only obtain the ultra-pure coal with the ash content of less than 2 percent, the ash content is relatively high, and the particle size of the obtained ultra-pure coal is coarse and can not meet the requirements of functional carbon powder materials on particle size and purity.

Patent CN107892971A discloses a process for preparing ultra-pure coal by physical-chemical method of anthracite, which comprises the following steps: 1) taking anthracite, grinding the anthracite to pass through a 0.5mm sieve to obtain a coal sample; 2) performing a flotation test on the coal sample to obtain flotation clean coal; 3) adding NaOH into the flotation cleaned coal, roasting for 12h at 200 ℃, and filtering to obtain secondary coal; 4) and (3) adding 5% HCl into the secondary coal, stirring for 1h at room temperature, filtering and drying to obtain the ultra-pure coal. The patent can only obtain the ultra-pure coal with the ash content of less than 2 percent, the ash content is relatively high, and the particle size of the obtained ultra-pure coal is very coarse and can not meet the requirements of functional carbon powder materials.

Patent CN105728156A discloses a preparation process of ultrapure coal, which is suitable for use in the technical field of mineral separation. Crushing low-ash anthracite coal by a high-efficiency fine crusher, and then sorting the crushed low-ash anthracite coal in a three-product interference bed to obtain coarse clean coal, middlings and gangue; grading the coarse clean coal by a three-product cyclone screen, and dehydrating the coarse clean coal by a coal slime centrifugal machine to obtain a coarse-grained ultrapure coal product; and (3) carrying out primary coarse grinding on the middlings, then grading the middlings by using a sieve bend, enabling the middlings to enter a spiral sorting machine on the sieve bend to be thrown, and carrying out secondary fine grinding on the light products, and enabling the light products, the undersize and overflow of a three-product spiral-flow sieve, the centrifugal liquid of a coal slime centrifugal machine and the undersize of the sieve bend to enter flotation equipment for flotation so as to obtain fine-grain ultra-pure coal products.

The processes for preparing the fine coal by crushing the anthracite are more, the requirements of novel carbon materials on particle size cannot be met mostly, and meanwhile, the ash content of the finally obtained coal is higher (the ash content is more than 1.0%) although the methods are more for preparing the ashless coal, and the processes have at least one defect, such as complex process, serious equipment corrosion, ineffective recovery of valuable substances, high treatment cost, high environmental protection pressure, high energy consumption, higher impurity content and the like. For the field of new energy materials, the existing impurity removal process and crushing process can not meet the requirements of the new energy anode material on impurity content and particle size, so that the process is not industrially applied.

Disclosure of Invention

The invention aims to provide a method for preparing superfine clean coal by combining a ball milling pretreatment and a chemical method, aiming at the technical problems of high ash content and overlarge coal powder particle size after the existing coal powder is subjected to impurity removal, and the superfine coal powder with small particle size and narrow distribution interval can be obtained by removing volatile components from crushed anthracite in protective atmosphere and cooperating with the ball milling pretreatment, and the purity of the obtained superfine coal powder is not lower than 99.5 wt% after impurity removal.

In order to achieve the technical purpose, the invention adopts the following technical scheme:

a method for preparing superfine clean coal by combining ball milling pretreatment and a chemical method comprises the following steps:

(1) crushing anthracite, and roasting in a protective atmosphere to obtain coal particles; adding a dispersing agent into the obtained coal particles, controlling the grading of grinding balls, performing ball milling, and drying to obtain superfine coal powder;

(2) mixing the superfine coal powder with a surfactant, adding the mixture into a mixed immersion liquid of acid and fluoride salt, heating and leaching, filtering, washing and drying to obtain the superfine clean coal powder.

The coal contains a large amount of organic matters such as aliphatic hydrocarbon, aromatic hydrocarbon, oxygen-nitrogen compound, heterocyclic compound and the like, which causes the coal to have viscosity, and the inventor finds that the viscosity can obstruct the refining process of the coal, and the coal cannot be refined continuously after being crushed to a certain particle size by adopting the conventional mechanical crushing process, and even can generate agglomeration phenomenon. The method effectively removes partial organic matters in the coal, reduces the viscosity of the coal powder, and synergistically controls the technological parameters of ball milling pretreatment to obtain the superfine coal powder with small particle size and narrow distribution interval by roasting the crushed anthracite in protective atmosphere.

Preferably, in step (1), the anthracite coal is crushed to-200 meshes.

Preferably, in step (1), the protective atmosphere is at least one of nitrogen, helium and argon.

Preferably, in the step (1), the roasting temperature is 400-800 ℃, and the time is 2-8 h.

Preferably, in the step (1), the dispersant is at least one of triethanolamine, sodium alkyl oleate, polyethylene glycol and ethanol, and the addition amount is 1-100mL/300g of coal particles.

Preferably, in the step (1), the grinding balls are at least one of stainless steel, hard alloy, polyurethane, zirconia and agate, and the number ratio of the large balls, the medium balls and the small balls is 1:1-3:1-6 or the number ratio of the medium balls and the small balls is 1: 1-2.

Preferably, in the step (1), the mass ratio of the ball materials during ball milling is 5-20:1, the ball milling rotation speed is 200-.

Preferably, in the step (1), the drying mode is vacuum drying, the temperature is 70-90 ℃ or freeze drying, and the temperature is-10 to-50 ℃. The superfine coal powder after mechanical activation has the characteristics of large specific surface area and good activity, and the preferable drying mode of the invention can prevent the structure from being damaged as much as possible and keep the activity of the superfine coal powder.

Preferably, in the step (2), the surfactant is at least one selected from ethanol, polyethylene glycol, triethanolamine and sodium alkyl oleate, preferably ethanol; the dosage of the surfactant is 2-15wt% of the superfine coal powder, and preferably 10 wt% of the superfine coal powder.

Preferably, in the step (2), the acid is selected from at least one of nitric acid and hydrochloric acid, and is preferably hydrochloric acid; the acid concentration is 2.0-8.0mol/L, and the preferable acid concentration is 6.0 mol/L; the fluoride salt is at least one selected from sodium fluoride, aluminum fluoride, lithium fluoride and calcium fluoride, preferably sodium fluoride; the fluoride salt concentration is 5-30g/L, preferably 18 g/L.

Preferably, in the step (2), the liquid-solid ratio of the mixed immersion liquid to the superfine coal powder is 5-30mL/g, and the preferable liquid-solid ratio is 15 mL/g; the heating leaching temperature is 40-90 ℃, and preferably 60 ℃; the heating leaching time is 1-5h, preferably 2 h.

The invention has the following beneficial effects:

1. according to the invention, through removing volatile components from the crushed anthracite in a protective atmosphere and cooperatively controlling the technological parameters of ball milling pretreatment, the bottleneck problem of refining in the traditional mechanical crushing process is broken through, the superfine coal powder with smaller particle size and narrow distribution interval can be obtained, the particle size D90 of the coal powder is less than 3 mu m, so that impurities wrapped in the coal are fully exposed, and the subsequent impurity removal process is promoted.

2. The invention adopts the acid and fluoride salt mixed immersion liquid to remove impurities from the pretreated superfine coal powder, the acid can remove metal oxides, metal carbonates and acid-soluble impurities in the coal, and the fluoride salt is added under the acidic condition to remove inorganic salt impurities which are difficult to react with hydrochloric acid but can be dissolved in hydrofluoric acid, thereby further improving the impurity removal effect.

3. According to the invention, the crushed anthracite is subjected to volatile removal in a protective atmosphere, ball milling pretreatment process parameters are cooperatively controlled, superfine pulverized coal with smaller particle size and narrow distribution interval is obtained, and then the acid and fluoride mixed immersion liquid is adopted for impurity removal, so that the super-efficient removal of various impurities in the anthracite is realized, the superfine clean anthracite with the ash content of less than 0.5 wt% can be obtained, and the requirements of a new energy source cathode material on purity and particle size can be completely met. Under the synergistic effect of all the process steps, the purity of the obtained superfine anthracite powder is not less than 99.5 wt%.

Drawings

FIG. 1 is a particle size distribution diagram of ultrafine pulverized coal prepared in example 1;

FIG. 2 is a particle size distribution diagram of the ultrafine pulverized coal prepared in example 2;

FIG. 3 is a particle size distribution diagram of the ultrafine pulverized coal prepared in example 3;

FIG. 4 is a particle size distribution diagram of the ultrafine pulverized coal prepared in comparative example 1;

fig. 5 is a distribution diagram of the particle size of the ultra fine pulverized coal prepared in comparative example 2.

Detailed Description

The invention is further illustrated by the following examples, but is not limited thereto.

The anthracite components adopted in the embodiments and the comparative examples of the invention have the following mass contents: the fixed carbon content was 86.24%, the volatiles content was 9.32%, the ash content was 3.4%, and the moisture content was 1.04%. The mass content of main elements of ash is as follows: o29.48, Si20.00, Al15.58, Fe11.21, Ca11.02, S4.49, Mg2.70 and Na2.66.

Example 1

Taking anthracite, primarily crushing the anthracite into minus 200 meshes, placing the anthracite into a corundum crucible, and preserving the heat for 8 hours at the temperature of 600 ℃ in a muffle furnace in nitrogen atmosphere to remove volatile components.

Taking 50g of devolatilized coal powder, adding the devolatilized coal powder into a zirconia ball milling tank, adding 10ml of absolute ethyl alcohol into the ball milling tank, selecting zirconia balls as medium balls, and controlling the medium ball grading to be medium balls: the pellet is 1:1, the pellet-material ratio is 10:1, the rotating speed of the planetary ball mill is 300r/min, the ball milling time is 12h, after drying for 4h in a vacuum drying oven, the superfine coal powder with good dispersibility is obtained, and the particle size distribution of the coal powder is measured by a laser particle size tester, as shown in fig. 1, D50 is 0.855 μm, and D90 is 1.609 μm.

Uniformly mixing superfine coal powder and 10 wt% of ethanol of the superfine coal powder, adding the mixture into mixed immersion liquid of hydrochloric acid and sodium fluoride to remove impurities, wherein the concentration of the hydrochloric acid is 6.0mol/L, the concentration of NaF is 18g/L, the temperature of the acid immersion is 60 ℃, the time is 2 hours, the liquid-solid ratio is 15mL/g, filtering and washing the mixture to be neutral after the acid immersion, and drying filter residues to obtain the superfine clean coal with the purity of 99.86%.

Example 2

Taking anthracite to primarily crush to-200 meshes, placing the anthracite into a corundum crucible, and preserving the heat for 4 hours at 650 ℃ in a muffle furnace in nitrogen atmosphere to remove volatile components.

Taking 50g of devolatilized coal powder, adding the devolatilized coal powder into a zirconia ball milling tank, adding 10ml of absolute ethyl alcohol into the ball milling tank, selecting zirconia balls as medium balls, and controlling the medium ball grading to be medium balls: the pellet is 1:1, the pellet-material ratio is 5:1, the rotating speed of the planetary ball mill is 300r/min, the ball milling time is 10h, after drying for 4h in a vacuum drying oven, the superfine coal powder with good dispersibility is obtained, and the particle size distribution of the coal powder is measured by a laser particle size tester, as shown in fig. 2, D50 is 1.592 μm, and D90 is 2.889 μm.

Uniformly mixing superfine coal powder and 10 wt% of ethanol of the superfine coal powder, adding the mixture into a mixed immersion liquid of hydrochloric acid and sodium fluoride to remove impurities, wherein the concentration of the hydrochloric acid is 3.6mol/L, the concentration of NaF is 18g/L, the temperature of acid immersion is 60 ℃, the time is 2 hours, the liquid-solid ratio is 15mL/g, filtering and washing the mixture to be neutral after acid immersion, and drying filter residues to obtain the superfine clean coal with the purity of 99.67%.

Example 3

Taking 50g of devolatilized coal powder, adding the devolatilized coal powder into a zirconia ball milling tank, adding 10ml of absolute ethyl alcohol into the ball milling tank, selecting zirconia balls as medium balls, and controlling the medium ball grading to be medium balls: the pellet is 1:2, the pellet-material ratio is 10:1, the rotation speed of the planetary ball mill is 300r/min, the ball milling time is 8h, after drying for 4h in a vacuum drying oven, ultrafine coal powder with good dispersibility is obtained, and the particle size distribution of the coal powder is measured by a laser particle size tester, as shown in fig. 3, D50 is 1.536 μm, and D90 is 2.937 μm.

Uniformly mixing superfine coal powder and 10 wt% of ethanol of the superfine coal powder, adding the mixture into mixed immersion liquid of hydrochloric acid and sodium fluoride to remove impurities, wherein the concentration of the hydrochloric acid is 4.8mol/L, the concentration of NaF is 15g/L, the temperature of the acid immersion is 60 ℃, the time is 2 hours, the liquid-solid ratio is 15mL/g, filtering and washing the mixture to be neutral after the acid immersion, and drying filter residues to obtain the superfine clean coal with the purity of 99.53%.

Comparative example 1

Taking 50g of raw coal which is primarily crushed to-200 meshes, adding the raw coal into a zirconia ball milling tank, adding 10ml of absolute ethyl alcohol into the ball milling tank, selecting zirconia balls as medium balls, and controlling the medium ball grading to be medium balls: the pellet is 1:1, the pellet-material ratio is 5:1, the rotating speed of the planetary ball mill is 300r/min, the ball milling time is 10h, after drying for 4h in a vacuum drying oven, the superfine coal powder with good dispersibility is obtained, and the particle size distribution of the coal powder is measured by a laser particle size tester, as shown in fig. 4, D50 is 12.4 μm, and D90 is 26.1 μm.

Uniformly mixing superfine coal powder and 10 wt% of ethanol of the superfine coal powder, adding the mixture into a mixed immersion liquid of hydrochloric acid and sodium fluoride to remove impurities, wherein the concentration of the hydrochloric acid is 3.6mol/L, the concentration of NaF is 18g/L, the temperature of acid immersion is 60 ℃, the time is 2 hours, the liquid-solid ratio is 15mL/g, filtering and washing the mixture to be neutral after acid immersion, and drying filter residues to obtain the superfine clean coal with the purity of 99.27%.

Comparative example 2

Taking anthracite to primarily crush to about minus 200 meshes, placing the anthracite into a corundum crucible, and preserving the heat for 4 hours at 650 ℃ in a muffle furnace in nitrogen atmosphere to remove volatile components.

Taking 50g of devolatilized coal powder, adding the devolatilized coal powder into a zirconia ball milling tank, adding no absolute ethyl alcohol, selecting zirconia balls as medium balls, and controlling the medium ball grading to be medium balls: the pellet is 1:1, the pellet-material ratio is 5:1, the rotation speed of the planetary ball mill is 300r/min, the ball milling time is 10h, after drying for 4h in a vacuum drying oven, the superfine coal powder with good dispersibility is obtained, and the particle size distribution of the coal powder is measured by a laser particle size tester, as shown in fig. 5, D50 is 17.5 μm, and D90 is 40.1 μm.

Uniformly mixing superfine coal powder and 10 wt% of ethanol of the superfine coal powder, adding the mixture into a mixed immersion liquid of hydrochloric acid and sodium fluoride to remove impurities, wherein the concentration of the hydrochloric acid is 3.6mol/L, the concentration of NaF is 18g/L, the temperature of acid immersion is 60 ℃, the time is 2 hours, the liquid-solid ratio is 15mL/g, filtering and washing the mixture to be neutral after acid immersion, and drying filter residues to obtain the superfine clean coal with the purity of 99.11%.

Comparative example 3

Taking 50g of devolatilized coal powder, adding the devolatilized coal powder into a zirconia ball milling tank, adding 10ml of absolute ethyl alcohol into the ball milling tank, selecting zirconia balls as medium balls, and controlling the medium ball grading to be medium balls: and (3) the small balls are 1:1, the ball-material ratio is 5:1, the rotating speed of the planetary ball mill is 300r/min, the ball milling time is 10 hours, and the superfine coal powder with good dispersibility is obtained after drying for 4 hours in a vacuum drying oven.

Uniformly mixing the superfine coal powder and 10 wt% of ethanol of the superfine coal powder, adding the mixture into hydrochloric acid to remove impurities, wherein the concentration of the hydrochloric acid is 3.6mol/L, the acid leaching temperature is 60 ℃, the time is 2 hours, the liquid-solid ratio is 15mL/g, filtering and washing the mixture to be neutral after acid leaching, and drying filter residues to obtain the superfine clean coal with the purity of 98.97%.

Claims

1. A method for preparing superfine clean coal by combining ball milling pretreatment and a chemical method is characterized by comprising the following steps:

(1) crushing anthracite, and roasting in a protective atmosphere to obtain coal particles; adding a dispersing agent into the obtained coal particles, wherein the dispersing agent is at least one of triethanolamine, sodium alkyl oleate, polyethylene glycol and ethanol, and the addition amount is 1-100mL/300g of coal particles; controlling the grading of the grinding balls, performing ball milling, and drying to obtain superfine coal powder; the grinding balls are at least one of stainless steel, hard alloy, polyurethane, zirconia and agate, and the number ratio of the large balls, the medium balls and the small balls is 1:1-3:1-6 or the number ratio of the medium balls and the small balls is 1: 1-2;

(2) mixing superfine coal powder and a surfactant, and adding the mixture into a mixed immersion liquid of acid and fluoride salt, wherein the acid is at least one of nitric acid and hydrochloric acid; the acid concentration is 2.0-8.0 mol/L; the fluoride salt is at least one of sodium fluoride, aluminum fluoride, lithium fluoride and calcium fluoride; the concentration of the fluoride salt is 5-30 g/L; after heating and leaching, filtering, washing and drying, the superfine clean coal powder is obtained.

2. The method for preparing the superfine clean coal by the combination of the ball milling pretreatment and the chemical method according to claim 1, which is characterized in that: in the step (1), the anthracite is crushed to-200 meshes.

3. The method for preparing the superfine clean coal by the combination of the ball milling pretreatment and the chemical method according to claim 1, which is characterized in that: in the step (1), the protective atmosphere is at least one of nitrogen, helium and argon;

the roasting temperature is 400-800 ℃, and the time is 2-8 h.

4. The method for preparing the superfine clean coal by the combination of the ball milling pretreatment and the chemical method according to claim 1, which is characterized in that: in the step (1), the ball-material mass ratio during ball milling is 5-20:1, the ball milling rotation speed is 200-.

5. The method for preparing the superfine clean coal by the combination of the ball milling pretreatment and the chemical method according to claim 1, which is characterized in that: in the step (1), the drying mode is vacuum drying at the temperature of 70-90 ℃ or freeze drying at the temperature of-10 to-50 ℃.

6. The method for preparing the superfine clean coal by the combination of the ball milling pretreatment and the chemical method according to claim 1, which is characterized in that: in the step (2), the surfactant is selected from at least one of ethanol, polyethylene glycol, triethanolamine and sodium alkyl oleate, and the dosage of the surfactant is 2-15wt% of the mass of the superfine coal powder.

7. The method for preparing the superfine clean coal by the combination of the ball milling pretreatment and the chemical method according to claim 1, which is characterized in that: in the step (2), the liquid-solid ratio of the mixed immersion liquid to the superfine coal powder is 5-30 mL/g; the heating and leaching temperature is 40-90 ℃; the heating leaching time is 1-5 h.