Method for preparing ultra-pure coal based on low-ash bituminous coal

Abstract

The invention belongs to the technical field of ultra-pure coal preparation, and particularly discloses a method for preparing ultra-pure coal based on low-ash bituminous coal, aiming at low-metamorphic bituminous coal with low ash content, the ash content of the prepared ultra-pure coal is reduced to 0.5 wt% or below by adopting a multi-stage flotation method and cooperating with interval type ore grinding, the whole preparation method is simple in process and high in preparation efficiency, and the method is suitable for industrial production. The ultra-pure coal can be conveniently and quickly prepared, and the high-value utilization of the coal is favorably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-pure coal preparation, and particularly to a method for preparing ultra-pure coal based on low-ash bituminous coal. Background Art

[0002] Among coal products, coal with extremely low ash content, such as clean coal with an ash content ≤ 8 wt%, or ultra-low ash anthracite with an ash content ≤ 5 wt%, is a special type of coal product. Its characteristics are that it hardly produces soot when burning, and at the same time has advantages such as high electrical conductivity, high chemical activity, and high mechanical strength. It is a high-quality raw material for manufacturing products such as activated carbon, carbon, and carbon-based composites. With the development of science and technology and industrial production, coal with a low ash content is playing an increasingly important role in fields such as metallurgy, chemical engineering, and energy storage.

[0003] Existing methods for deep coal ash removal mainly use physical methods and chemical methods. Physical methods include: flotation method, selective flocculation method, oil agglomeration method, triboelectrostatic separation method, gravity separation method, etc.; chemical methods include: acid-base method, hydrofluoric acid method, organic solvent method, etc. However, the above existing deep coal ash removal methods often have inevitable defects and are difficult to achieve large-scale production applications. For example, the flotation method has a high production cost. When the particle size of the raw coal fed is too fine, it is extremely easy to cause difficulties in separation, and it is necessary to go through multiple flotation operations to meet the ash content index requirements, while the clean coal yield decreases with the increase in the number of operations. The selective flocculation method has low separation accuracy, and ash is easily entrained into the clean coal, affecting the product quality. At the same time, the coal slurry fed needs to be stirred for a long time to achieve selective flocculation, and the dosage of the flocculant is large, resulting in high costs. The oil agglomeration method has high requirements for equipment and requires precise control of the stirring time. The separation of coal and ash uses screen filtration, and the process flow is complex. Moreover, the dosage of the medicine in this method is as high as 20 - 50 kg per ton of raw coal, and the medicine cost is high, and the economic efficiency of industrial promotion and application is poor. The triboelectrostatic separation method has high requirements for the ash content of the raw coal fed. If the feed ash content is high, the separation effect is poor, and the universality is poor. The gravity separation method has low separation efficiency for fine coal, and the separation lower limit using traditional heavy medium is about 0.5 mm, and it is impossible to effectively separate the extremely fine coal after deep dissociation. Chemical methods require the use of a large amount of chemical agents, the process conditions are harsh, and at the same time, a large amount of acid-base wastewater is generated, which is easy to cause environmental pollution. In addition, some chemical methods will damage the structure and properties of coal during the ash removal process, which is not conducive to subsequent utilization.

[0004] Taking coal with a low ash content as the raw material, further reducing the ash content therein and achieving high-yield preparation of ultra-pure coal with an ash content < 1 wt% is one of the important technical problems that the industry needs to solve. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a method for preparing ultra-pure coal based on low-ash bituminous coal.

[0006] To achieve the above object, the present invention is implemented according to the following technical solutions:

[0007] A method for preparing ultra-clean coal from low-ash bituminous coal, comprising the following steps:

[0008] S1. Crushing raw low-ash bituminous coal with an ash content of 1.5 - 2 wt% into particles with a particle size of less than 1 mm, and feeding it into a ball mill for grinding to fully dissociate the coal and minerals, obtaining raw coal particles with a particle size of less than 200 mesh;

[0009] S2. Adding the raw coal particles into a pulp mixing and stirring tank, adding water to adjust the pulp to obtain a pulp with a concentration of 40 - 80 g / L, adding 2000 g of collector and 800 g of frother per ton of pulp; after adjusting the pulp, the pulp enters a flotation machine for rough selection to obtain clean coal 1 and tail coal;

[0010] S3. Adding clean coal 1 into a pulp mixing and stirring tank, adding water to adjust the pulp to obtain a pulp with a concentration of 40 - 80 g / L, adding 150 g of collector and 75 g of frother per ton of pulp; after adjusting the pulp, the pulp enters a flotation machine for cleaning to obtain clean coal 2 and middling coal 1;

[0011] S4. Adding clean coal 2 into a pulp mixing and stirring tank, adding water to adjust the pulp to obtain a pulp with a concentration of 40 - 80 g / L, adding 150 g of collector and 75 g of frother per ton of pulp; after adjusting the pulp, the pulp enters a flotation machine for cleaning to obtain clean coal 3 and middling coal 2;

[0012] S5. Transferring clean coal 3 into a ball mill for grinding, adding it into a pulp mixing and stirring tank, adding water to adjust the pulp to obtain a pulp with a concentration of 40 - 80 g / L, adding 200 g of collector and 100 g of frother per ton of pulp; after adjusting the pulp, the pulp enters a flotation machine for cleaning to obtain clean coal 4 and middling coal 3;

[0013] S6. Adding clean coal 4 into a pulp mixing and stirring tank, adding water to adjust the pulp to obtain a pulp with a concentration of 40 - 80 g / L, adding 150 g of collector and 75 g of frother per ton of pulp; after adjusting the pulp, the pulp enters a flotation machine for cleaning to obtain clean coal 5 and middling coal 4;

[0014] S7. Adding clean coal 5 into a pulp mixing and stirring tank, adding water to adjust the pulp to obtain a pulp with a concentration of 40 - 80 g / L, adding 150 g of collector and 75 g of frother per ton of pulp; after adjusting the pulp, the pulp enters a flotation machine for cleaning to obtain clean coal 6 and middling coal 5;

[0015] S8. Transferring clean coal 6 into a ball mill for grinding, adding it into a pulp mixing and stirring tank, adding water to adjust the pulp to obtain a pulp with a concentration of 40 - 80 g / L, adding 200 g of collector and 100 g of frother per ton of pulp; after adjusting the pulp, the pulp enters a flotation machine for cleaning to obtain clean coal 7 and middling coal 6;

[0016] S9. Add clean coal 7 into the pulp mixing and stirring tank, add water to adjust the pulp to obtain a pulp with a concentration of 40 - 80 g / L. Add 150 g of collector and 75 g of frother per ton of coal pulp. After pulp adjustment, the pulp enters the flotation machine for cleaning to obtain clean coal 8 and middling coal 7;

[0017] S10. Add clean coal 8 into the pulp mixing and stirring tank, add water to adjust the pulp to obtain a pulp with a concentration of 40 - 80 g / L. Add 100 g of collector and 50 g of frother per ton of coal pulp. After pulp adjustment, the pulp enters the flotation machine for cleaning to obtain middling coal 8 and clean coal 9;

[0018] S11. Filter and dry the obtained clean coal 9 to obtain ultra - pure coal with an ash content of less than 0.5 wt%.

[0019] Further, the collector is diesel oil and the frother is No. 2 oil.

[0020] Further, the grinding time each time is 10 - 20 min.

[0021] Further, the rotation speed of the flotation machine is 1800 - 2200 rad / min, the air inflow rate of the flotation machine is 200 - 250 L / h, and the scraping time of foam is 3 min.

[0022] Compared with the prior art, for low - rank bituminous coal with low ash content, the present invention adopts the "multi - stage flotation method" and combines it with intermittent grinding. The ash content of the obtained ultra - pure coal is reduced to less than 0.5 wt%. The whole preparation method has a simple process and high preparation efficiency, can conveniently and quickly prepare ultra - pure coal, and is beneficial to improving the high - value utilization of coal. Brief Description of the Drawings

[0023] Figure 1 It is the technical route diagram for preparing ultra - pure coal of the present invention. Detailed Embodiments

[0024] To make the purpose, technical solutions and advantages of the present invention clearer, the following further details the present invention with reference to embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the invention.

[0025] As Figure 1 shown, this embodiment exemplarily shows a method for preparing ultra - pure coal based on low - ash bituminous coal, and the specific operation process is as follows:

[0026] 1) Crush the raw coal of low - ash bituminous coal with an ash content of 1.5 - 2 wt% into particles with a particle size of less than 1 mm, send it into a ball mill for grinding for 20 min to fully dissociate the coal and minerals, and obtain raw coal particles with a particle size of less than 200 mesh. The proximate analysis and ultimate analysis of the raw coal are shown in Table 1.

[0027] Table 1

[0028]

[0029] 2) Add raw coal particles into the pulp mixing tank, add water to make pulp to obtain a pulp with a concentration of 40 - 80 g / L. Add 2000 g of diesel as collector and 800 g of No. 2 oil as frother per ton of coal pulp, and mix and stir for 3 min. After pulping, the pulp enters the flotation machine for roughing. The rotational speed of the flotation machine is 2000 rad / min, the air inflow of the flotation machine is 200 L / h, and the scraping time is 3 min; Obtain clean coal 1 and tail coal;

[0030] 3) Add clean coal 1 into the pulp mixing tank, add water to make pulp to obtain a pulp with a concentration of 40 - 80 g / L. Add 150 g of diesel as collector and 75 g of No. 2 oil as frother per ton of coal pulp. After pulping, the pulp enters the flotation machine for cleaning. The rotational speed of the flotation machine is 2000 rad / min, the air inflow of the flotation machine is 200 L / h, and the scraping time is 3 min; Obtain clean coal 2 and middling coal 1;

[0031] 4) Add clean coal 2 into the pulp mixing tank, add water to make pulp to obtain a pulp with a concentration of 40 - 80 g / L. Add 150 g of diesel as collector and 75 g of No. 2 oil as frother per ton of coal pulp. After pulping, the pulp enters the flotation machine for cleaning. The rotational speed of the flotation machine is 2000 rad / min, the air inflow of the flotation machine is 200 L / h, and the scraping time is 3 min; Obtain clean coal 3 and middling coal 2;

[0032] 5) Transfer clean coal 3 to the ball mill for grinding for 15 min, add it into the pulp mixing tank, add water to make pulp to obtain a pulp with a concentration of 40 - 80 g / L. Add 200 g of diesel as collector and 100 g of No. 2 oil as frother per ton of coal pulp. After pulping, the pulp enters the flotation machine for cleaning. The rotational speed of the flotation machine is 2000 rad / min, the air inflow of the flotation machine is 200 L / h, and the scraping time is 3 min; Obtain clean coal 4 and middling coal 3;

[0033] 6) Add clean coal 4 into the pulp mixing tank, add water to make pulp to obtain a pulp with a concentration of 40 - 80 g / L. Add 150 g of diesel as collector and 75 g of No. 2 oil as frother per ton of coal pulp. After pulping, the pulp enters the flotation machine for cleaning. The rotational speed of the flotation machine is 2000 rad / min, the air inflow of the flotation machine is 200 L / h, and the scraping time is 3 min; Obtain clean coal 5 and middling coal 4;

[0034] 7) Add the clean coal 5 into the pulp mixing tank, add water to adjust the pulp to obtain a pulp with a concentration of 40 - 80 g / L. Add 150 g of diesel (collector) and 75 g of No. 2 oil (foaming agent) per ton of coal pulp. After pulp adjustment, the pulp enters the flotation machine for fine selection. The rotational speed of the flotation machine is 2000 rad / min, the air inflow of the flotation machine is 200 L / h, and the scraping time of foam is 3 min; obtain clean coal 6 and middling coal 5;

[0035] 8) Transfer the clean coal 6 to the ball mill for grinding for 15 min, add it into the pulp mixing tank, add water to adjust the pulp to obtain a pulp with a concentration of 40 - 80 g / L. Add 200 g of diesel (collector) and 100 g of No. 2 oil (foaming agent) per ton of coal pulp. After pulp adjustment, the pulp enters the flotation machine for fine selection. The rotational speed of the flotation machine is 2000 rad / min, the air inflow of the flotation machine is 200 L / h, and the scraping time of foam is 3 min; obtain clean coal 7 and middling coal 6;

[0036] 9) Add the clean coal 7 into the pulp mixing tank, add water to adjust the pulp to obtain a pulp with a concentration of 40 - 80 g / L. Add 150 g of diesel (collector) and 75 g of No. 2 oil (foaming agent) per ton of coal pulp. After pulp adjustment, the pulp enters the flotation machine for fine selection. The rotational speed of the flotation machine is 2000 rad / min, the air inflow of the flotation machine is 200 L / h, and the scraping time of foam is 3 min; obtain clean coal 8 and middling coal 7;

[0037] 10) Add the clean coal 8 into the pulp mixing tank, add water to adjust the pulp to obtain a pulp with a concentration of 40 - 80 g / L. Add 100 g of diesel (collector) and 50 g of No. 2 oil (foaming agent) per ton of coal pulp. After pulp adjustment, the pulp enters the flotation machine for fine selection. The rotational speed of the flotation machine is 2000 rad / min, the air inflow of the flotation machine is 200 L / h, and the scraping time of foam is 3 min; obtain middling coal 8 and clean coal 9;

[0038] 11) Filter and dry the obtained clean coal 9 to obtain ultra - pure coal with an ash content less than 0.5 wt%.

[0039] Take the obtained ultra - pure coal for ash content determination. The specific determination process is as follows:

[0040] Gradually send the ash dish filled with ultra - pure coal from outside the furnace into a muffle furnace pre - heated to 815 ± 10 °C for ashing and burning until the mass is constant. Take the percentage of the mass of the residue in the mass of the coal sample as the ash yield; the calculation formula is as follows

[0041] Aad=(m 1 / m)×100;

[0042] In the formula: Aad—the ash yield of the air - dried coal sample, %;

[0043] m 1 —the mass of the residue, g;

[0044] m—the mass of the coal sample, g.

[0045] The flotation result data of this embodiment are shown in Table 2.

[0046] Table 2

[0047]

[0048] As can be seen from Table 2, the ash content of the ultra-clean coal in this embodiment is 0.46 wt%.

[0049] As a comparison, ultra-clean coal was prepared by conventional flotation through multiple flotation processes, and the results are shown in Table 3.

[0050] Table 3

[0051]

[0052] As can be seen from Table 3, as the number of flotation times increases, the ash content of the clean coal basically does not decrease.

[0053] The technical solution of the present invention is not limited to the limitations of the above specific embodiments. Any technical deformation made according to the technical solution of the present invention falls within the protection scope of the present invention.

Claims

1. A method for preparing ultra-pure coal based on low-ash bituminous coal, characterized in that: The following steps are involved: S1. crushing low-ash bituminous coal with an ash content of 1.5-2wt% into a particle size of less than 1 mm, and feeding it into a ball mill for grinding to fully dissociate the coal from the minerals to obtain raw coal particles of less than 200 meshes; S2, adding raw coal particles into a slurry mixing barrel and adding water to prepare the slurry to obtain a slurry with a concentration of 40-80g / L, adding 2000g of collector and 800g of frother per ton of coal slurry; after slurry preparation, the slurry enters a flotation machine for rough selection to obtain clean coal 1 and tail coal; S3, adding clean coal 1 into a slurry mixing tank and adding water to prepare a slurry with a concentration of 40-80g / L, adding 150g of collector and 75g of foaming agent per ton of coal slurry; After slurry adjustment, the slurry enters the flotation machine for concentration to obtain clean coal 2 and medium coal 1; S4, adding clean coal 2 into a slurry mixing tank and adding water to prepare the slurry to obtain a slurry with a concentration of 40-80g / L, adding 150g of collector and 75g of frother per ton of coal slurry; after slurry preparation, the slurry enters a flotation machine for selection to obtain clean coal 3 and medium coal 2; S5, the clean coal 3 is transferred to a ball mill for grinding, and water is added to a slurry mixing barrel for slurry mixing to obtain a slurry with a concentration of 40-80g / L, and 200g of a collector and 100g of a frother are added to each ton of coal slurry; after slurry mixing, the slurry enters a flotation machine for concentration to obtain clean coal 4 and medium coal 3; S6, add clean coal 4 into a slurry mixing tank and add water to mix the slurry to obtain a slurry with a concentration of 40-80g / L, and add 150g of collector and 75g of foaming agent per ton of coal slurry; After slurry adjustment, the slurry enters the flotation machine for concentration to obtain clean coal 5 and medium coal 4; S7, add clean coal 5 into a slurry mixing tank, add water to mix the slurry to obtain a slurry with a concentration of 40-80g / L, and add 150g of collector and 75g of foaming agent per ton of coal slurry; After slurry adjustment, the slurry enters the flotation machine for concentration to obtain clean coal 6 and medium coal 5; S8, transfer clean coal 6 into a ball mill for grinding, add water into a slurry mixing barrel for slurry mixing to obtain a slurry with a concentration of 40-80g / L, add 200g of collector and 100g of frother per ton of coal slurry; after slurry mixing, the slurry enters a flotation machine for concentration to obtain clean coal 7 and medium coal 6; S9, adding clean coal 7 into a slurry mixing barrel and adding water to prepare the slurry to obtain a slurry with a concentration of 40-80g / L, adding 150g of collector and 75g of frother per ton of coal slurry; after slurry preparation, the slurry enters a flotation machine for selection to obtain clean coal 8 and medium coal 7; S10, adding clean coal 8 into a slurry mixing tank and adding water to mix the slurry to obtain a slurry with a concentration of 40-80 g / L, adding 100 g of collector and 50 g of frother per ton of coal slurry; after slurry mixing, the slurry enters a flotation machine for selection to obtain medium coal 8 and clean coal 9; S11, filtering and drying the obtained clean coal 9 to obtain ultra-pure coal with an ash content of less than 0.5wt%.

2. The method for preparing ultra-pure coal based on low-ash bituminous coal according to claim 1, characterized in that: The collector is diesel and the foaming agent is 2# oil.

3. The method for preparing ultra-pure coal based on low-ash bituminous coal according to claim 1, characterized in that: Each grinding time is 10-20 minutes.

4. The method for preparing ultrapure coal based on low-ash bituminous coal according to claim 1, characterized in that: The flotation machine has a rotation speed of 1800-2200 rad / min, an aeration volume of 200-250 L / h, and a bubble scraping time of 3 min.

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