A separation process for reducing the lower limit of dense medium separation of high rank coal and improving separation precision

Abstract

The application discloses a kind of separation process for reducing the lower limit of rare coal dense medium separation and improving separation precision, in view of the problems of high medium consumption, low separation precision, high lower limit of separation particle size and other problems existing in current dense medium separation, heavy medium coal preparation system is introduced into heavy medium particle size reconstruction method, by heavy medium particle size composition reconstruction and reducing medium particle size lower limit, based on equal sinking ratio, maximum limit reduces the lower limit of heavy medium separation particle size, realizes the effective separation of fine coal; by concentrating throwing part of non-magnetic slime, construct micro-fine medium powder magnetic separation to recover suitable feed concentration. Strengthen the efficient recovery of heavy medium, reduce medium consumption. The application innovatively introduces heavy medium particle size reconstruction and rare medium concentration desliming and strengthening magnetic separation recovery two processes and methods, which maximally reduces the lower limit of heavy medium separation and improves the separation precision of fine coal slime, shortens the separation process and reduces the medium consumption.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coal washing and separation, in particular to a separation process for reducing the lower limit of heavy medium separation of high-rank coal and improving separation precision. BACKGROUND

[0002] Coal washing is the source of clean utilization of coal. Through washing, most of the ash and sulfur in coal can be removed, which can greatly reduce the emission of smoke and SO2 after combustion, and is crucial for the clean and efficient utilization of the downstream coal industry.

[0003] Currently, existing coal separation technologies include gravity separation, flotation, dry coal separation, etc. Gravity separation and flotation are widely used in coal separation plant processes and flows. As an efficient coal separation process, heavy medium separation is widely used in China's coal separation process. It has strong processing capacity and high degree of mechanization, and good separation efficiency, which plays a positive role in China's green coal development and production.

[0004] Many existing heavy medium coal separation plants use lump coal shallow tank heavy medium + fine coal heavy medium cyclone separation process. However, the large particle size of lump coal and the high coal and gangue intergrowth result in high middlings content in lump coal separation, and most of the middlings are used for power generation, which leads to waste of scarce coal resources. If the middlings are further separated, it will increase the crushing and necessary auxiliary equipment, making the separation process more complex. At the same time, the existing heavy medium separation has the problems of high lower limit of separation particle size and high medium consumption. In order to reduce the lower limit of separation particle size, the lower limit of heavy medium particle size must be further reduced, which requires large amount of water and high pressure for medium removal, resulting in further reduction of dilute medium concentration, reduction of fine heavy medium recovery rate, and increase of medium consumption. Due to the different quality of purchased heavy medium magnetite powder, the particle size distribution is different, which greatly affects the separation precision and heavy medium recovery. Therefore, it is necessary to improve the separation precision and recovery by adjusting the particle size of the medium. The existing coal separation process is generally a three-stage process of heavy medium separation + coarse coal slime separation + flotation. Coarse coal slime separation generally uses coarse coal slime separator or coal slime heavy medium cyclone for separation, which has the problems of low separation precision, difficult management and high medium consumption. Therefore, it is very important to reduce the three-stage coal separation process to a two-stage process, and it is also necessary to improve the recovery efficiency of fine heavy medium magnetite powder in dilute medium. SUMMARY

[0005] In view of the problems of high medium consumption, low separation precision and high lower limit of separation particle size in the existing heavy medium separation, the present application provides a separation process for reducing the lower limit of heavy medium separation of high-rank coal and improving separation precision.

[0006] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows:

[0007] A separation process for reducing the lower limit of dense medium separation of high rank coal and improving separation precision, comprising the following steps:

[0008] (1) Prepare a slurry with a mass concentration of 35%-50% in a stirring barrel, and then let the slurry flow into a mill for grinding to obtain magnetite powder with a particle size of-200 mesh accounting for more than 99% and-325 mesh accounting for more than 90%;

[0009] (2) After crushing by a crusher, the raw coal is separated in a pressurized three-product dense medium cyclone with the magnetite powder prepared in step (1) to obtain clean coal, medium coal and gangue;

[0010] (3) The clean coal, medium coal and gangue in step (2) are sequentially introduced into respective de-medium arc-shaped screens and vibration de-medium screens for de-medium and dewatering;

[0011] (4) Most of the qualified medium under the de-medium arc-shaped screen and the de-medium vibration screen of the clean coal in step (3) is introduced into a raw coal medium mixing barrel, and the remaining part is introduced into a clean coal dilute medium thickener for thickening, the overflow is introduced into a flotation system, the underflow is introduced into a magnetic separation system, the magnetic separation concentrate is introduced into the raw coal medium mixing barrel, and the magnetic separation tailings are introduced into a hydraulic classification system, the overflow is introduced into the flotation system, and the underflow is introduced into a coarse clean coal slurry dewatering system;

[0012] (5) Most of the qualified medium under the de-medium arc-shaped screen and the de-medium vibration screen of the medium coal and the gangue in step (3) is introduced into the raw coal medium mixing barrel, and the remaining part is introduced into a medium gangue dilute medium thickener for thickening, the thickening overflow is directly introduced into a tail coal thickener, the underflow is introduced into a magnetic separation system, the magnetic separation concentrate is introduced into the raw coal medium mixing barrel, and the magnetic separation tailings are introduced into a fine medium gangue dewatering system.

[0013] Preferably, the mill in step (1) is a vertical ball mill, the number of stirring grinding sections is selected to be 1 section, 2 sections or multiple sections according to the actual grinding fineness, and the mill is selected to be in parallel or in series according to the processing capacity and the grinding fineness.

[0014] Preferably, the crusher in step (2) is a cone crusher or a roller crusher, and the crushing particle size is 50 mm.

[0015] Preferably, the clean coal dilute medium thickener in step (4) is a non-driven deep-cone high-efficiency thickener, and the underflow concentration of the thickener is 200-300 g / L.

[0016] Preferably, the medium gangue dilute medium thickener in step (5) is a non-driven deep-cone high-efficiency thickener, and the underflow concentration of the thickener is 200-300 g / L; the tail coal thickener is a center-driven rake thickener or a periphery-driven rake thickener, and the underflow concentration of the thickener is 400-500 g / L.

[0017] Preferably, the coarse clean slime dewatering system in step (4) comprises a clean magnetic tail bucket, a stacked screen, a vertical centrifuge, the magnetic tailings enter the clean magnetic tail bucket, and then are pumped into the stacked screen, the upper screen of the stacked screen enters the vertical centrifuge for dewatering, the lower screen enters the flotation system, the centrifuge filtrate returns to the clean magnetic tail bucket, and the centrifuge dewatering product is the coarse clean coal.

[0018] Preferably, the middlings dewatering system in step (5) comprises a middlings magnetic tail bucket, a classification cyclone, a tailings rake thickener, a middlings sieve bend, and a vertical centrifuge, the magnetic tailings enter the middlings magnetic tail bucket, are pumped into the classification cyclone, the overflow of the classification cyclone enters the tailings rake thickener, the underflow of the classification cyclone enters the middlings sieve bend, the upper screen of the middlings sieve bend enters the vertical centrifuge, the lower screen enters the flotation system, the centrifuge filtrate enters the middlings magnetic tail bucket, and the centrifuge dewatering product is the middlings.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] 1. The present application innovatively introduces two processes and methods of heavy medium particle size reconstruction and dilute medium thickening desliming-magnetic separation recovery, reduces the lower limit of the particle size of the heavy medium, maximally reduces the lower limit of the particle size of the heavy medium based on the equal settling ratio, realizes effective separation of fine coal particles, reduces the coarse slime separation process, and shortens the coal separation process flow;

[0021] 2. Based on the problems of fine heavy medium particle size and poor recovery of low-concentration magnetic separation, the present application throws away part of the non-magnetic slime by thickening, improves the concentration of the dilute medium entering the magnetic separator, strengthens the efficient recovery of the heavy medium, and reduces the medium consumption. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a process flow diagram for reducing the lower limit of heavy medium separation of high-rank coal and improving the separation accuracy.

[0023] Figure 2 It is an original process flow diagram of a certain coal preparation plant in Shanxi. DETAILED DESCRIPTION

[0024] The present application will be further described in detail below in combination with the drawings and specific embodiments.

[0025] The present embodiment provides a process for reducing the lower limit of heavy medium separation of high-rank coal and improving the separation accuracy, which is applied to actual coal separation in a coal preparation plant, as shown in the figure, comprising the following steps: Figure 1

[0026] (1) Prepare a magnetite powder and water slurry with a mass concentration of 35%-50% in a stirring bucket, and the slurry flows into a stirred mill for grinding to obtain a magnetite powder with a particle size of more than 99% of-200 mesh and more than 90% of-325 mesh;

[0027] ​(2) The raw coal entering the crusher is crushed (-50mm) and enters the pressurized three-product dense medium cyclone together with the heavy medium magnetite powder entering the mixing barrel for separation, and the separated clean coal, medium coal and gangue are obtained;

[0028] (3) The clean coal, medium coal and gangue in step (2) enter the respective medium removal arc screen and medium removal vibrating screen for medium removal and dewatering in turn;

[0029] (4) The qualified medium under the clean coal medium removal arc screen and medium removal vibrating screen in step (3) mostly enters the qualified medium barrel, and the remaining part is divided into the clean coal dilute medium deep cone high-efficiency thickener for thickening, the underflow concentration of the thickener is 200-300g / L, the overflow enters the flotation system, the underflow is subjected to magnetic separation, the magnetic separation concentrate enters the qualified medium barrel, the magnetic separation tailings are subjected to hydrocyclone classification, the overflow goes to the flotation system, and the underflow enters the clean coal magnetic tailings barrel and is pumped into the stacked screen, the screen overflow enters the vertical centrifuge for dewatering, the screen underflow enters the flotation system, the centrifuge filtrate returns to the clean coal magnetic tailings barrel, and the centrifuge dewatering product is the coarse clean coal;

[0030] (5) The qualified medium under the medium coal and gangue medium removal arc screen and medium removal vibrating screen in step (3) mostly enters the qualified medium barrel, and the remaining part is divided into the medium-gangue dilute medium deep cone high-efficiency thickener for thickening, the underflow concentration of the thickener is 200-300g / L, the thickening overflow directly enters the rake thickener, the underflow is subjected to magnetic separation, the underflow concentration is 400-500g / L, the magnetic separation concentrate enters the qualified medium barrel, and the magnetic separation tailings enter the medium-gangue magnetic tailings barrel and are pumped into the classification cyclone, the classification cyclone overflow enters the rake thickener, the classification cyclone underflow enters the medium-gangue arc screen, the screen overflow enters the vertical centrifuge, the screen underflow enters the flotation system, the centrifuge filtrate enters the medium-gangue magnetic tailings barrel, and the centrifuge dewatering product is the medium coal;

[0031] (6) The flotation system in steps (4) and (5) is the mineral slurry pretreater, the mineral slurry pretreater flows into the flotation machine, the flotation machine concentrate is subjected to pressure filter dewatering to become the flotation clean coal, the tailings directly enter the rake thickener for thickening, the thickener overflow is used as the circulating water, the underflow enters the pressure filter for pressure filtration, the underflow concentration is 400-500g / L, and the pressure filtration product is the slime.

[0032] Compared with the original process flow (such as Figure 2 ), through the heavy medium grinding size reconstruction and dilute medium thickening and magnetic separation of the present technical solution, the test results are shown in Table 1.

[0033] Table 1 Comparison of production indexes of coal preparation plants

[0034]

[0035] According to the statistical result, the heavy medium iron magnetic ore powder consumption of 560 tons can be reduced, the magnetite price is 800 yuan / ton, the cost of 448,000 yuan can be saved, 12,800 tons of clean coal can be increased, the clean coal price is 2,000 yuan / ton, the pre-tax profit of 25,600,000 yuan can be increased every year according to the calculation of 40 million tons / year processing capacity. It can be seen that the technical scheme can not only improve the economic benefit of the coal preparation plant, but also improve the utilization rate of coal resources.

[0036] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited to this. Any modification, equivalent replacement and improvement within the technical range disclosed by the present application, which is made by any person skilled in the art within the spirit and principle of the present application, should be covered within the protection scope of the present application.

Claims

1. A process for reducing the lower limit of high-rank coal heavy medium separation and improving separation accuracy, characterized in that: The following steps are involved: (1) Magnetite powder and clean water are mixed in a mixing tank to form a slurry with a mass concentration of 35% to 50%, and the slurry is fed to a mill for grinding to obtain magnetite powder with a particle size of more than 99% of -200 mesh and more than 90% of -325 mesh; (2) The washed raw coal is crushed by a crusher and then enters a pressurized three-product heavy medium cyclone for separation with the heavy medium magnetite powder prepared in step (1), and clean coal, medium coal and gangue are obtained after separation; (3) The clean coal, medium coal and gangue in step (2) are respectively fed into respective de-mediation curved screens and de-mediation vibrating screens for de-mediation and dehydration; (4) Most of the qualified media under the clean coal de-mediation curved screen and the de-mediation vibrating screen in step (3) enter the raw coal medium mixing barrel, and the remaining part is diverted with the dilute medium to the clean coal dilute medium concentrator for concentration, the overflow enters the flotation system, the underflow enters the magnetic separation system, the magnetic separation concentrate enters the raw coal medium mixing barrel, the magnetic separation tailings are hydraulically classified, the overflow goes to the flotation system, and the underflow enters the coarse clean coal slime dehydration system; (5) Most of the qualified media under the de-mediation curved screen and de-mediation vibrating screen of the medium coal and gangue in step (3) enter the raw coal medium mixing barrel, and the remaining part is diverted to the medium gangue dilute medium concentrator for concentration. The concentrated overflow directly enters the tailing coal concentrator, and the bottom flow is magnetically separated. The magnetically separated concentrate enters the raw coal medium mixing barrel, and the magnetically separated tailings enter the powder medium gangue dehydration system.

2. The process for reducing the lower limit of high-rank coal heavy medium separation and improving separation accuracy according to claim 1 is characterized in that: The mill described in step (1) is a vertical ball mill. The number of stirred grinding sections is selected as 1, 2 or more sections according to the actual grinding fineness. The mills are selected in parallel or in series according to the processing capacity and grinding fineness.

3. The process for reducing the lower limit of high-rank coal heavy medium separation and improving separation accuracy according to claim 1, characterized in that: The crusher described in step (2) is a cone crusher or a roller crusher, and the crushing particle size is -50mm.

4. The process for reducing the lower limit of high-rank coal heavy medium separation and improving separation accuracy according to claim 1, characterized in that: The clean coal dilute medium concentrator described in step (4) is a transmission-free deep cone high-efficiency concentrator, and the concentrator bottom flow concentration is 200-300g / L.

5. The process for reducing the lower limit of high-rank coal heavy medium separation and improving separation accuracy according to claim 1, characterized in that: The medium gangue concentrator described in step (5) is a transmission-free deep cone high-efficiency concentrator, and the concentrator bottom flow concentration is 200-300g / L; the tail coal concentrator is a central transmission rake concentrator or a peripheral transmission rake concentrator, and the concentrator bottom flow concentration is 400-500g / L.

6. The process for reducing the lower limit of high-rank coal heavy medium separation and improving separation accuracy according to claim 1, characterized in that: The coarse clean coal slime dewatering system described in step (4) includes a clean coal magnetic tail barrel, a stacked screen, and a vertical centrifuge. The magnetic tailings enter the clean coal magnetic tail barrel and are then pumped into the stacked screen by a pump. The upper portion of the stacked screen enters the vertical centrifuge for dewatering, and the lower portion of the screen enters the flotation system. The centrifuge filtrate returns to the clean coal magnetic tail barrel, and the dewatered product of the centrifuge is coarse clean coal.

7. The process for reducing the lower limit of high-rank coal heavy medium separation and improving separation accuracy according to claim 1, characterized in that: The fine medium gangue dehydration system described in step (5) includes a medium gangue magnetic tail barrel, a grading cyclone, a tail coal rake thickener, a medium gangue curved screen, and a vertical centrifuge. The magnetically separated tailings enter the medium gangue magnetic tail barrel and are pumped into the grading cyclone by a pump. The overflow of the grading cyclone enters the tail coal rake thickener. The underflow of the grading cyclone enters the medium gangue curved screen. The medium gangue curved screen enters the vertical centrifuge and the underflow enters the flotation system. The filtrate of the centrifuge enters the medium gangue magnetic tail barrel. The dehydrated product of the centrifuge is medium coal.

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