Silica coal recleaning process for power coal preparation plant

Abstract

The invention discloses a process for recleaning silicon coal in a power coal preparation plant, which comprises the following steps: S1, washing, namely washing and processing raw coal in a coking coal preparation plant; s2, screening: screening and sorting the clean coal, and forming high-ash clean coal products from oversize products larger than 25 mm and undersize products smaller than 3 mm; s3, separation is conducted, specifically, 25-3 mm clean coal is separated, and a dense medium is added and prepared by adding water into coal slime powder; and S4, dewatering and centrifuging: after separation, carrying out two-stage overflow dewatering and centrifuging to form a high-ash clean coal product. S5, preliminary recovery: combining and recovering clean coal and qualified coal slime suspension of a medium gangue system, and returning to the system for recycling; s6, classified recovery is conducted, specifically, clean coal and medium gangue magnetic separation tailings enter a coarse clean coal classification cyclone, and overflow of the coarse clean coal classification cyclone and undersize water of the sieve bend enter a concentration filter pressing system; and S7, recycling: recycling overflow of the thickener as circulating water. The problems of partial clean coal loss, low production efficiency and poor silicon coal quality caused by secondary coal slime in clean coal washing processing are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon coal washing and processing, and in particular to a silicon coal re-selection process in a thermal coal preparation plant. Background Art

[0002] The domestic industrial silicon industry generally adopts the "electric heating method" and "all-coal smelting" production process, that is, using electricity as the heat source and carbon as the reducing agent, smelting in a semi-closed reduction furnace, adding materials at regular intervals and taking out of the furnace at regular intervals. The preparation of this method mainly uses carbon to reduce silica in an electric arc furnace, with silica as the raw material and carbonaceous materials as the reducing agent.

[0003] As a reducing agent, charcoal has high porosity, high resistivity, strong reducing ability, low ash content and a certain block size, making it the best carbonaceous reducing agent. However, due to the increasing depletion of charcoal resources and the increasing particle size of national forest resources protection, it is urgent to find a substitute for charcoal.

[0004] Silicon coal is a coal product and also a carbonaceous reducing agent. It is one of the main raw materials for the production and smelting of industrial silicon. It is smelted with silica in a submerged arc furnace to produce industrial silicon. With the expansion of downstream application areas of the silicon industry chain, the consumption of reducing agent silicon coal is increasing, and silicon coal washing and processing has become more and more important. Moreover, silicon coal washing and processing is also an important direction for coal preparation plants to expand product application areas, and plays an important role in realizing the comprehensive utilization of coal resources and environmental protection.

[0005] At present, in the existing optimization and upgrading, clean coal is usually screened, and the clean coal with a particle size of 25-3mm is sold as silicon coal, and the oversize of 25mm and undersize of 3mm form high-ash clean coal products for sale as thermal coal. 3+ Adhere to the surface of coal particles, affecting the Fe 3+ Content, <0.5mm clean coal enters the coal sludge filter press system with the coal sludge water, and fails to be fully washed and recovered, resulting in low production efficiency and loss of high-quality coal yield, and high ash content in silicon coal affecting industrial silicon smelting. Summary of the invention

[0006] Based on the technical problems existing in the background technology, the present invention proposes a process for re-selecting silicon coal in a thermal coal preparation plant.

[0007] The present invention proposes a process for re-selecting silicon coal in a thermal coal preparation plant, comprising the following steps:

[0008] S1: Raw coal is washed and processed in a coking coal preparation plant to form clean coal and medium coal.

[0009] S2: Clean coal enters the thermal coal preparation plant for screening and sorting. After screening with a double-layer vibrating relaxation screen, the oversize of 25 mm and the undersize of 3 mm form high-ash clean coal products;

[0010] S3: 25-3mm clean coal enters the non-pressure three-product heavy medium cyclone for sorting, and the added heavy medium is made of coal slime powder and water;

[0011] S4: After sorting, the first overflow is de-slimed and de-filtered by a de-media screen, and then dehydrated by a centrifuge to become a silicon coal product. The second overflow and bottom flow are de-slimed and dehydrated by a de-media screen, and then dehydrated by a centrifuge for the second time to become a high-ash clean coal product.

[0012] S5: The qualified coal slime suspension of the clean coal and medium gangue system is combined and recovered and returned to the system for recycling; the dilute medium is recovered separately, and the concentrate is returned to the system after the clean coal and dilute medium are magnetically separated, and the tailings are de-roughened and the coal slime is recovered; the dilute medium produced by the medium gangue is combined and magnetically separated, and the concentrate is returned to the system after the tailings are de-roughened and the coal slime is recovered;

[0013] S6: Clean coal and medium gangue magnetic separation tailings enter the coarse clean coal classification cyclone, the underflow enters the coarse clean coal curved screen, the screen material is dehydrated by the centrifuge and then mixed into the high ash clean coal, the coarse clean coal classification cyclone overflow and the curved screen water enter the concentration filter press system;

[0014] S7: The underflow of the concentrator is recovered by an ultra-high pressure filter press and mixed into high-ash clean coal for use in the coking plant. The overflow of the concentrator is recycled as circulating water.

[0015] The S1 includes the following steps:

[0016] Step 1: One-stage flotation. First, the washed coal slime is subjected to one-stage flotation to obtain the first clean coal, the first medium coal and the first tail coal. This process is usually completed using a main flotation machine. The main flotation machine includes a plurality of ore troughs, which are arranged in sequence from the upstream of the flotation to the downstream of the flotation. The first collecting bin is connected to part of the ore troughs to collect the first clean coal, and the second collecting bin is connected to the remaining part of the ore troughs to collect the first medium coal.

[0017] Step 2: Secondary flotation: whether to conduct secondary flotation is determined based on the floatability of the coal slime. If the floatability of the coal slime is not less than the set threshold, the first clean coal and the first medium coal are subjected to filter pressing to obtain clean coal. If the floatability of the coal slime is less than the set threshold, the first medium coal is subjected to secondary flotation to obtain the second clean coal and the second medium coal. During the secondary flotation process, the overflow of the medium gangue cyclone is often used to treat the first medium coal.

[0018] Step three: filtration and concentration. The first clean coal and the second clean coal are filtered to obtain clean coal. The second medium coal is concentrated and filtered in turn to obtain medium coal. Similarly, the first tail coal is concentrated and filtered in turn to obtain tail coal. In addition, the coal slime water produced with the clean coal, medium coal and tail coal can be recovered and mixed into the first tail coal before concentration. At the same time, the circulating water produced when the first tail coal is concentrated can be recovered and reused.

[0019] Preferably, the thermal coal preparation plant is equipped with a double-layer vibrating flap screen with rectangular screen holes to improve screening efficiency. The flap screen can effectively separate coal of different particle sizes through a unique vibration method, avoid clogging of the holes by fine particles, and ensure the continuity and stability of the screening process.

[0020] Preferably, the heavy medium is magnetite powder prepared by adding water to coal sludge powder, which avoids the Fe3+ of magnetite powder adhering to the surface of coal particles and affecting the Fe3+ content of silicon coal. Magnetite powder is the most practical weighting material. It is abundant in source, relatively cheap, non-toxic, non-corrosive, chemically stable, and easy to recycle. In addition, the suspension prepared with magnetite powder has a wide density range and is suitable for the sorting of various coals.

[0021] Preferably, the overflow of one stage is passed through the de-sludging screen to remove the medium and mud, and the circulating water on the de-sludging screen is used to wash the coal particles again to reduce the surface heavy medium Fe 3+ content.

[0022] Preferably, the filter press system is an ultra-high pressure filter press to reduce the moisture content of high-ash clean coal.

[0023] The beneficial effects of the present invention are:

[0024] 1. This scheme expands the selection range of raw coal for thermal coal preparation plants, achieving low ash content and Fe 2 O 3 The content is low, and the proportion of 25-3mm particle size is high. The raw coal is first washed and processed by the coking coal preparation plant to reduce the excess waste of raw coal directly washed with silicon coal. The clean coal enters the thermal coal preparation plant for screening to meet the particle size requirements. The coal slime heavy medium suspension separation avoids the magnetite powder Fe 3+ The influence of the surface of attached coal particles on Fe 3+ The circulating water on the de-mesh screen washes the coal particles again to reduce the surface heavy medium Fe 3+ The content of <3mm undersize, >25mm oversize, coarse clean coal and high ash fine mud filter cake are mixed as high ash clean coal products for coking, which ultimately solves the problem of partial clean coal loss caused by secondary coal mud in the clean coal washing process, low production efficiency and poor silicon coal quality (silicon coal requires low ash content and Fe 2 O 3 The content is low and the proportion of 25-3mm particle size is high).

[0025] 2. This scheme can improve and ensure the quality of coal products through coal selection, especially for those low-quality coal seams with poor occurrence conditions, and produce a variety of coal products to meet the specific needs of different users and improve energy utilization efficiency. The processed high-quality coal can reduce the emission of harmful gases and smoke and alleviate coal burning pollution.

[0026] 3. This scheme, the process mainly includes washing, first stage flotation, second stage flotation, filter pressing, concentration and other steps. By sorting the coal slimes with different floatability, the extraction rate of clean coal can be improved and the waste of resources can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a process flow chart of re-selecting silicon coal in a thermal coal preparation plant proposed by the present invention;

[0028] Figure 2 This is a detailed block diagram of the process flow of re-selecting silicon coal in a thermal coal preparation plant proposed by the present invention;

[0029] Figure 3 This is the existing coal screening flow chart. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0031] Reference Figure 1-2 , a process for re-selecting silicon coal in a thermal coal preparation plant, comprising the following steps:

[0032] S1: Raw coal is washed and processed in a coking coal preparation plant to form clean coal and medium coal.

[0033] S2: Clean coal enters the thermal coal preparation plant for screening and sorting. After screening with a double-layer vibrating relaxation screen, the oversize of 25 mm and the undersize of 3 mm form high-ash clean coal products;

[0034] S3: 25-3mm clean coal enters the non-pressure three-product heavy medium cyclone for sorting, and the added heavy medium is made of coal slime powder and water;

[0035] S4: After sorting, the first overflow is de-slimed and de-filtered by a de-media screen, and then dehydrated by a centrifuge to become a silicon coal product. The second overflow and bottom flow are de-slimed and dehydrated by a de-media screen, and then dehydrated by a centrifuge for the second time to become a high-ash clean coal product.

[0036] S5: The qualified coal slime suspensions from the clean coal and medium gangue systems are combined and recovered and returned to the system for recycling; the dilute medium is recovered separately, and after the clean coal and dilute medium are magnetically separated, the concentrate is returned to the system, and the tailings are de-coarsened clean coal slime recovery system; the dilute medium produced by the medium gangue removal is combined and magnetically separated, and the concentrate is returned to the system, and the tailings are de-coarsened clean coal slime recovery system. The added medium is prepared by adding coal slime powder and water to form a concentrated medium, which is pumped to the medium system;

[0037] S6: Clean coal and medium gangue magnetic separation tailings enter the coarse clean coal classification cyclone, the underflow enters the coarse clean coal curved screen, the screen material is dehydrated by the centrifuge and then mixed into the high ash clean coal, the coarse clean coal classification cyclone overflow and the curved screen water enter the concentration filter press system;

[0038] S7: The underflow of the concentrator is recovered by an ultra-high pressure filter press and mixed into high-ash clean coal for use in the coking plant. The overflow of the concentrator is recycled as circulating water.

[0039] The S1 includes the following steps:

[0040] Step 1: One-stage flotation. First, the washed coal slime is subjected to one-stage flotation to obtain the first clean coal, the first medium coal and the first tail coal. This process is usually completed using a main flotation machine. The main flotation machine includes a plurality of ore troughs, which are arranged in sequence from the upstream of the flotation to the downstream of the flotation. The first collecting bin is connected to part of the ore troughs to collect the first clean coal, and the second collecting bin is connected to the remaining part of the ore troughs to collect the first medium coal.

[0041] Step 2: Secondary flotation: whether to conduct secondary flotation is determined based on the floatability of the coal slime. If the floatability of the coal slime is not less than the set threshold, the first clean coal and the first medium coal are subjected to filter pressing to obtain clean coal. If the floatability of the coal slime is less than the set threshold, the first medium coal is subjected to secondary flotation to obtain the second clean coal and the second medium coal. During the secondary flotation process, the overflow of the medium gangue cyclone is often used to treat the first medium coal.

[0042] Step three: filtration and concentration. The first clean coal and the second clean coal are filtered to obtain clean coal. The second medium coal is concentrated and filtered in turn to obtain medium coal. Similarly, the first tail coal is concentrated and filtered in turn to obtain tail coal. In addition, the coal slime water produced with the clean coal, medium coal and tail coal can be recovered and mixed into the first tail coal before concentration. At the same time, the circulating water produced when the first tail coal is concentrated can be recovered and reused.

[0043] In the present invention, the flap screen is a double-layer vibrating flap screen to improve screening efficiency; the filter press is an ultra-high pressure filter press to reduce the moisture content of high-ash fine mud filter cake.

[0044] In the present invention, a thermal coal preparation plant is provided with a double-layer vibrating relaxation screen with rectangular screen holes to improve screening efficiency. The relaxation screen can effectively separate coal of different particle sizes through a unique vibration mode, and can avoid clogging of holes by fine particles, thereby ensuring the continuity and stability of the screening process.

[0045] In the present invention, the heavy medium is magnetite powder prepared by adding water to coal sludge powder, which avoids the Fe3+ of magnetite powder adhering to the surface of coal particles and affecting the Fe3+ content of silicon coal. Magnetite powder is the most practical weighting material, which is abundant in source, relatively cheap, non-toxic, non-corrosive, chemically stable, and easy to recycle. In addition, the suspension prepared by magnetite powder has a wide density range and is suitable for the sorting of various coals.

[0046] In the present invention, the overflow of one stage is passed through the de-sludging screen to remove the medium and mud, and the circulating water on the de-sludging screen washes the coal particles again to reduce the surface heavy medium Fe 3+ content.

[0047] In the present invention, by coal selection, the quality of coal products can be improved and guaranteed, especially for those low-quality coal seams with poor occurrence conditions, a variety of coal products can be produced to meet the specific needs of different users and improve energy utilization efficiency. The processed high-quality coal can reduce the emission of harmful gases and smoke and alleviate coal burning pollution.

[0048] Working principle: clean coal enters the main workshop of the power coal preparation plant from the raw coal bunker through a belt. A double-belt coal feeder is installed under the raw coal bunker to improve the stability of coal feeding; the clean coal enters the double-layer vibrating and stretching screen for dry screening. The double-layer vibrating and stretching screen has a high processing capacity and screening efficiency. The double-layer screen surface can achieve two-stage screening at the same time. 25-3mm clean coal enters the pressureless three-product heavy medium cyclone for sorting. The heavy medium is made of coal slime powder and water, which avoids magnetite powder Fe 3+ The influence of the surface of attached coal particles on Fe 3+ The content of the sieve is less than 3mm and the sieve is greater than 25mm. The sieve is used as a high-ash clean coal product for coking. After sorting, the overflow is deslued by the de-sieving screen and dehydrated by the horizontal centrifuge to become a silicon coal product, which is transported to the silicon coal product bin by a belt. The circulating water on the de-sieving screen washes the coal particles again to reduce the surface heavy medium Fe 3+The second-stage overflow and bottom flow are desludged by the desludging screen and dehydrated by the horizontal centrifuge to become high-ash clean coal products; the qualified coal slime heavy medium of the clean and medium gangue system is returned to the medium system for recycling; the dilute medium is recovered separately, and after the clean coal dilute medium is magnetically separated, the concentrate is returned to the medium system for recycling, and the tailings are coarse clean coal slime recovery system. After the medium gangue dilute medium is combined with magnetic separation, the concentrate is returned to the medium system for recycling, and the tailings are coarse clean coal slime recovery system; the added medium is made of coal slime powder and water to prepare a concentrated medium, which is pumped to the medium system. The clean coal magnetic tail and the medium gangue magnetic tail enter the coarse clean coal classification cyclone, which is a small-diameter classification cyclone, thereby improving the classification accuracy. After classification and concentration, the bottom flow enters the coarse clean coal arc screen, and the material on the arc screen is dehydrated by the vertical centrifuge and mixed into the high-ash clean coal. The overflow of the coarse clean coal classification cyclone and the water under the arc screen enter the concentration filter press system. The underflow of the concentrator is recovered by an ultra-high pressure filter press, and the high-ash fine mud filter cake is reduced to below 15.5%, and high-ash clean coal is added for use in the coking plant. The overflow of the concentrator is recycled as circulating water.

[0049] This solution expands the selection range of raw coal for thermal coal preparation plants, achieving low ash content and Fe 2 O 3 The content is low, and the proportion of 25-3mm particle size is high. The raw coal is first washed and processed by the coking coal preparation plant to reduce the excess waste of raw coal directly washed with silicon coal. The clean coal enters the thermal coal preparation plant for screening to meet the particle size requirements. The coal slime heavy medium suspension separation avoids the magnetite powder Fe 3+ The influence of the surface of attached coal particles on Fe 3+ The circulating water on the de-mesh screen washes the coal particles again to reduce the surface heavy medium Fe 3+ The content of <3mm undersize, >25mm oversize, coarse clean coal and high ash fine mud filter cake are mixed as high ash clean coal products for coking, which ultimately solves the problem of partial clean coal loss caused by secondary coal mud in the clean coal washing process, low production efficiency and poor silicon coal quality (silicon coal requires low ash content and Fe 2 O 3 The content is low and the proportion of 25-3mm particle size is high).

[0050] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A process for re-selecting silicon coal in a thermal coal preparation plant, characterized in that: The following steps are involved: S1: Flotation, the raw coal is washed and processed in the coking coal preparation plant to form clean coal; S2: Screening: the clean coal is screened and sorted, and the oversize of 25 mm and undersize of 3 mm form high-ash clean coal products; S3: Sorting, 25-3mm clean coal sorting, adding heavy medium made of coal slime powder and water; S4: Dehydration and centrifugation. After sorting, it passes through two stages of overflow dehydration and centrifugation to form a high-ash clean coal product; S5: Initial recovery: the qualified coal slime suspension from the clean coal and medium gangue systems is combined and recovered and returned to the system for recycling; S6: Classification recovery, clean coal and medium gangue magnetic separation tailings enter the coarse clean coal classification cyclone, and the coarse clean coal classification cyclone overflow and the water under the arc screen enter the concentration filter press system; S7: Circulation recovery, the underflow of the concentrator is recovered, and the overflow of the concentrator is recycled as circulating water.

2. A process for re-selecting silicon coal in a thermal coal preparation plant according to claim 1, characterized in that: In S1, the raw coal is first washed and processed in a coking coal preparation plant. The different physical and chemical properties of coal particles and other impurities are used to remove gangue, ash and sulfur-containing substances in the coal through screening and washing processes.

3. A process for re-selecting silicon coal in a thermal coal preparation plant according to claim 1, characterized in that: In S2, the clean coal enters the thermal coal preparation plant and is screened using a double-layer vibrating relaxation screen.

4. A process for re-selecting silicon coal in a thermal coal preparation plant according to claim 1, characterized in that: The concentrated filter press system is an ultra-high pressure filter press.

5. A process for re-selecting silicon coal in a thermal coal preparation plant according to claim 1, characterized in that: The thermal coal preparation plant is provided with a double-layer vibrating relaxation screen, and the screen holes are rectangular in size.

6. A process for re-selecting silicon coal in a thermal coal preparation plant according to claim 1, characterized in that: In S6, the bottom flow enters the coarse clean coal arc screen, and the screen material is dehydrated by the centrifuge and then mixed into the high-ash clean coal.

7. A process for re-selecting silicon coal in a thermal coal preparation plant according to claim 1, characterized in that: In S5, the produced dilute medium is recovered separately. After the clean coal dilute medium is magnetically separated, the concentrate is returned to the system, and the tailings are de-coarsened clean coal and coal slime recovery system; the dilute medium produced by the gangue removal is combined with magnetic separation, and the concentrate is returned to the system, and the tailings are de-coarsened clean coal and coal slime recovery system.

8. A process for re-selecting silicon coal in a thermal coal preparation plant according to claim 1, characterized in that: The S1 includes the following steps: Step 1: One-stage flotation. First, the washed coal slime is subjected to one-stage flotation to obtain the first clean coal, the first medium coal and the first tail coal. This process is usually completed using a main flotation machine. The main flotation machine includes a plurality of ore troughs, which are arranged in sequence from the upstream of the flotation to the downstream of the flotation. The first collecting bin is connected to part of the ore troughs to collect the first clean coal, and the second collecting bin is connected to the remaining part of the ore troughs to collect the first medium coal. Step 2: Secondary flotation: whether to perform secondary flotation is determined based on the floatability of the coal slime. If the floatability of the coal slime is not less than the set threshold, the first clean coal and the first medium coal are subjected to filter pressing to obtain clean coal. If the floatability of the coal slime is less than the set threshold, the first medium coal is subjected to secondary flotation to obtain second clean coal and second medium coal. Step three: filtration and concentration. The first clean coal and the second clean coal are filtered to obtain clean coal. The second medium coal is concentrated and filtered in turn to obtain medium coal. Similarly, the first tail coal is concentrated and filtered in turn to obtain tail coal. In addition, the coal slime water produced with the clean coal, medium coal and tail coal can be recovered and mixed into the first tail coal before concentration. At the same time, the circulating water produced when the first tail coal is concentrated can be recovered and reused.

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