Sare coking coal dense medium washing process for strengthening dissociation and recovery of middling coal

Abstract

The invention relates to the technical field of coal dressing, in particular to a scarce coking coal dense medium washing process for strengthening dissociation and recovery of middling coal. Comprising the steps of fine raw coal separation, fine clean coal medium drainage, fine middling coal medium drainage, fine gangue medium drainage, fine middling coal crushing, fine coal thin medium dehydration, thin medium magnetic separation, coal slime dense medium separation, coarse clean coal medium drainage, coarse middling coal medium drainage, coarse tailing magnetic separation, ore grinding operation, coarse clean coal magnetic separation, fine coal combined medium blending and coal slime mixing and blending. According to the method, the coal slime dense medium system which is completely independent of the slack coal dense medium is utilized, high-precision separation and tailing discarding operation of the coarse coal slime and the crushed slack middling coal are completed, the coarse middling coal is dissociated sufficiently and is not dissociated excessively, the separation precision of the coarse coal slime is high, the technological process is simple, separation is efficient, and economic benefits are remarkable.

Description

Technical Field

[0001] The invention relates to the technical field of coal preparation, and in particular to a scarce coking coal heavy medium washing process for strengthening the dissociation and recovery of medium coal. Technical Background

[0002] Coking coal is an indispensable raw material for steel manufacturing and plays a vital role in the industrial economic system. However, the main coking coal types such as coking coal and fat coal account for less than 15% of the total coal resources in my country. After washing, this scarce coking coal often produces 20% to 30% of medium coal, which can only be used as fuel due to its high ash content and poor adhesion, further reducing its resource utilization. How to recover and extract clean coal resources from medium coal to improve the recovery rate of scarce coking coal washing has always been an important research topic in the industry.

[0003] The difficulty of reselecting middling coal lies in the fact that associated minerals are embedded between coal particles. Currently, there are two ways to recycle middling coal: improving the accuracy of sorting equipment - multiple sorting and crushing and grinding and dissociation - reselection / flotation. With the continuous improvement of the sorting accuracy of coal preparation equipment in recent years, the middling coal from coking sorting can be sorted again by sorting equipment such as jigs, cyclones, and spiral sorters to achieve the recovery of a certain quality of qualified clean coal. Although the use of high-precision sorting equipment to sort the middling coal from coking sorting can recover qualified clean coal, the yield of clean coal is relatively low because the organic combustible body is still closely associated with the gangue. Therefore, it is imperative to achieve effective dissociation of scarce coking middling coal and then high-precision sorting to improve the recovery rate of clean coal.

[0004] Patent CN102861663A provides a two-stage recovery process of crushing, grinding, dissociation and re-flotation of scarce coking medium coal, focusing on the crushing, grinding and dissociation of medium coal >6mm and 6-0.5mm, as well as the two-stage equal-density heavy medium cyclone sorting and flotation regulation of the dissociated materials, achieving the purpose of medium coal dissociation and efficient sorting. However, the invention has the following problems: ① The heavy medium system and flotation system recovery are set separately for the medium coal products of the coal preparation plant, which is not comprehensively considered with the existing re-separation and flotation links, resulting in repeated investment, high operating costs and poor economy; ② After sorting, the 6-0.5mm medium coal and the <0.5mm coal slime are subjected to open-circuit grinding and then flotation, and the single grinding operation is difficult to control to achieve the requirements of sufficient dissociation without excessive dissociation. If the grinding particle size is too fine, not only will the energy consumption be high and the production cost be high, but the large amount of high-ash fine mud produced will be entrained to contaminate the flotation clean coal and reduce the quality of the clean coal. If the grinding particle size is too coarse, the middle coal will not be fully dissociated. The undissociated middle coal will either cause the clean coal ash content to exceed the standard or be lost in the tail coal, resulting in a waste of resources.

[0005] Patent CN113877717A discloses a method for combining heavy medium separation and flotation separation of fine coal, which can achieve efficient separation of 50 (80) ~ 1 mm fine coal and 1 ~ 0.25 mm coarse coal slime. However, in the separation of scarce coking coal, this process cannot meet the needs of separation density for different particle sizes. 1 ~ 0.25 mm coarse coal slime and 80 ~ 1 mm fine raw coal cannot be separated with equal ash content in the same medium density. Therefore, this method has the disadvantages of poor separation accuracy of coarse coal slime, high ash content, and loss of clean coal yield due to back ash in gravity separation.

[0006] Patent CN111167594A discloses an improved process for non-pressure three-product and coal slime heavy medium separation based on constant-low diversion, which can enhance the effect of 1-0.25mm coarse coal slime heavy medium separation and effectively reduce medium consumption. Patent CN115318429A discloses a non-de-sliming fine coal heavy medium separation process based on dilute medium classification and separation. The combined medium diversion and dilute medium containing 1-0.25mm coarse coal slime in the fine coal heavy medium system are precisely regulated and fed into the three-product coal slime heavy medium cyclone group to complete classification and separation, ensuring that the coarse coal slime separation is controllable, adjustable, high-precision and low-medium consumption. The above two patents achieve efficient separation of 80-1mm fine coal and 1-0.25mm coarse coal slime by adding a coarse coal slime heavy medium separation system and stabilizing diversion fluctuations and density control. However, the following problems still exist: ① The incoming materials for the heavy medium separation of coarse coal slime are mainly the combined medium diversion of the fine coal heavy medium system, which makes it impossible to independently adjust the separation density of the heavy medium of coarse coal slime, and it is always affected by the separation density of the heavy medium of the fine coal. Therefore, it is impossible to fully achieve the requirements of maximizing the clean coal yield by separating the basic ash content of different particle sizes. ② The higher requirements for the fineness of the heavy medium and the stability of the suspension in the separation of coarse coal slime are ignored. The fineness of the medium determines the stability of the suspension, which in turn affects the separation accuracy and product recovery rate. As the medium is continuously consumed, fine-grained magnetite is gradually lost in the magnetic tail and the product, and the -0.074mm content is reduced from 90% to 70%. The fineness and stability of the heavy medium deteriorate, making it difficult to meet the needs of high-precision separation of coarse coal slime.

[0007] From the above analysis, it can be seen that although many coal dissociation and coarse coal slime heavy medium separation methods have been proposed in the prior art, there are still problems of poor separation accuracy and low recovery rate for the dissociation and re-separation of scarce coking coal. Summary of the invention

[0008] In order to solve the above problems, the present invention provides a scarce coking coal heavy medium washing process for strengthening the dissociation and recovery of medium coal. The process utilizes completely independent fine coal heavy medium and coal slime heavy medium systems to complete the high-precision separation of fine raw coal and coarse coal slime. After the fine medium coal is dissociated, it enters the coal slime heavy medium system to avoid the mutual influence of the two systems and the repeated investment in the separate reselection of medium coal. After the coal slime heavy medium separation, the coarse medium coal is de-mediumed and the screen material is ground together with the bottom flow magnetic concentrate for closed-loop circulation separation, which ensures that the coarse medium coal is fully and not excessively dissociated and meets the fineness requirements of the heavy medium, thereby achieving the effect of strengthening the dissociation and recovery of the medium coal.

[0009] The present invention adopts the following technical solutions:

[0010] A scarce coking coal heavy medium washing process for enhancing the dissociation and recovery of medium coal comprises the following steps:

[0011] Step a, fine raw coal sorting: the fine raw coal with a particle size of no more than 50 mm is sorted in a three-product fine coal heavy medium cyclone under the action of a qualified medium to obtain fine clean coal, fine medium coal and fine gangue;

[0012] Step b 1 , fine clean coal de-mediation: in step a, the fine clean coal is de-mediated by a curved screen and a de-mediation screen to obtain curved screen combined media, de-mediation screen combined media, de-mediation screened thin media and screened oversize; wherein the curved screened combined media is divided into two parts by a diverter, the curved screened combined media split 1 and the de-mediation screened combined media are sent to the fine coal combined media barrel together, the curved screened combined media split 2 and the de-mediation screened thin media are sent to the thin media barrel together, and the screened oversize is dehydrated as a clean coal product;

[0013] Step b 2 , de-mediating the fine and medium coal: in step a, the fine and medium coal is de-mediated by a curved screen and a de-mediating screen to obtain a curved screened medium, a de-mediating screened medium and a sieve-surface material; wherein the curved screened medium and the de-mediating screened medium are sent to a media barrel together, and the sieve-surface material is fed into a coal slime mixing barrel;

[0014] Step b 3 , the fine gangue is removed: in step a, the fine gangue is removed by a curved screen and a removal screen to obtain a curved screen combined medium, a removal screen combined medium, a removal screen thin medium and a screen oversize; wherein the curved screen combined medium and the removal screen combined medium are sent to a combined medium barrel together; the removal screen thin medium is sent to a thin medium barrel, and the screen oversize is used as the fine gangue product;

[0015] Step d, dehydration of fine coal in dilute medium: Step b 1 Middle arc screen combined with medium diversion 2 and de-medium screen thinning, step b 3 The thin media on the middle de-mediating screen is buffered by the thin media barrel and then pumped to the dewatering screen for dehydration to obtain the oversize and undersize water.

[0016] Step e, dilute medium magnetic separation: the undersize water in step d is fed into a magnetic separator for the first magnetic separation to obtain magnetic concentrate and magnetic tailings; the magnetic concentrate is returned to the fine coal medium barrel, and the magnetic tailings are used as coal slime water for subsequent flotation operations;

[0017] Step f, coal slime heavy medium separation: the sieve material in step d, step b 2 The material on the medium-removal screen is buffered in a mixing barrel and then pumped to the three-product coal slime heavy medium cyclone group for separation to obtain coarse clean coal, coarse medium coal and coarse tailings coal;

[0018] Step g 1 , Coarse and clean coal de-mediation: In step f, the coarse and clean coal is fed into a double-layer curved screen for de-mediation to obtain an oversize and undersize combined medium; the undersize combined medium is divided into two streams, the undersize combined medium stream 1 is sent to the coal slime mixing barrel, and the undersize combined medium stream 2 is sent to the coarse and clean coal magnetic separation operation together with the oversize;

[0019] Step g 2 , De-mediation of coarse and medium coal: In step f, the coarse and medium coal is fed into a double-layer curved screen for de-mediation to obtain oversize and undersize mixed media; the oversize is sent to the grinding operation, and the undersize mixed media is sent to the coal slime mixing barrel;

[0020] Step g 3 , Coarse tailings magnetic separation: In step f, the coarse tailings are fed into a magnetic separator for a second magnetic separation to obtain magnetic concentrate and magnetic tailings; wherein the magnetic concentrate is subjected to grinding operation, and the magnetic tailings are graded and dehydrated as coarse tailings slime products;

[0021] Step i, coarse and clean coal magnetic separation: Step g 1 The material on the middle screen and the combined medium under the screen are fed into the clean coal magnetic separator for the third magnetic separation to obtain magnetic concentrate and magnetic tailings; the magnetic tailings are classified and dehydrated as coarse clean coal products, and the magnetic concentrate is divided into two streams, the magnetic concentrate split 1 goes to the fine coal combined medium barrel, and the magnetic concentrate split 2 goes to the coal slime mixing barrel;

[0022] Step j, mixing of fine coal and medium: Step b 1 Middle arc screen media splitter 1 and de-screen media, step b 2 Middle arc screen and stripping screen, step b 3 The middle arc-shaped screening medium and the de-screening medium, the magnetic fine separation 1 in step i, are buffered in the fine coal medium barrel and returned to step a as qualified medium;

[0023] Step k, coal slime mixing preparation: Step b 2 The material on the medium screen, the material on the medium screen in step d, the material on the medium screen in step g 1 Middle sieve and medium separation 1, step g 2 The mixed medium under the middle sieve, the material after grinding in step h, and the magnetic concentrate fraction 2 in step i are mixed and fed into the coal slime mixing barrel, and then returned to step f after buffering.

[0024] Preferably, the method further comprises step c, wherein the step c is to crush the fine coal:2 The material on the de-screening screen is first crushed by a crusher before being fed into the coal slime mixing barrel. The crusher is a reversible impact hammer crusher, which crushes the material on the screen to a particle size of less than 2 mm.

[0025] Preferably, the process further comprises step h, wherein step h is a grinding operation, and the step g is 2 The sieve material, step g 3 The magnetic concentrate and supplementary magnetite powder and water are ground and dissociated together, and the ground materials are then fed into the coal slime mixing barrel.

[0026] Preferably, in step h, the grinding operation adopts a rod mill, and the supplementary magnetite powder and water control the feed mass concentration at 45-55wt%, and the mineral particles with a particle size of less than 0.074mm in the material after grinding account for more than 80% of the total material mass content.

[0027] Preferably, the step b 1 and b 3 The de-mesh screen is divided into two sections. The first section is close to the feeding end, accounting for 1 / 3 of the total length of the de-mesh screen, with a sieve hole of 0.5mm; the second section is close to the discharging end, accounting for 2 / 3 of the total length of the de-mesh screen, with a sieve hole of 1.0mm. The second section is also equipped with a water spray, with a water spray volume of 1.2-2.0m 3 / t.

[0028] Preferably, the step b 2 In the process, the de-mediating screen is divided into two sections. The first section is close to the feeding end and occupies 1 / 3 of the total length of the de-mediating screen. The second section is close to the discharging end and occupies 2 / 3 of the total length of the de-mediating screen. The sieve holes of the de-mediating screen are all 0.5mm. No water spraying is set in this link.

[0029] Preferably, in step d, the cut-off particle size of the dewatering screen is 0.2 mm.

[0030] Preferably, the step g 1 and g 2 The mesh size of the double-layer curved screen is 0.35 mm, and the interception particle size is between 0.2 and 0.25 mm.

[0031] Preferably, in the second magnetic separation and the third magnetic separation, water is added to adjust the feed concentration of the magnetic separator to between 15 and 25 wt%.

[0032] Preferably, in the step j, the density of each material fed into the fine coal mixed medium barrel is regulated to be between 1.35 and 1.45 kg / L with the goal of first-stage separation of the three-product coal slime heavy medium cyclone.

[0033] Preferably, in the step k, the density of each material fed into the coal slime mixing barrel is regulated to be between 1.40 and 1.50 kg / L with the goal of first-stage separation of the three-product coal slime heavy medium cyclone.

[0034] Preferably, the step b 1 In the step g, the arc-shaped screening medium is divided into two parts by a flow divider, wherein the arc-shaped screening medium flow 2 accounts for 20% to 30% of the arc-shaped screening medium flow; 1 In the step, a diversion is set for the undersize medium, wherein the undersize medium diversion 2 accounts for 25% to 35% of the undersize medium flow rate; in the step i, the diversion ratio of the magnetic fine diversion 1 and the magnetic fine diversion 2 is adjusted according to the control density of the fine coal medium barrel.

[0035] The beneficial effects of the present invention are:

[0036] In the present invention, both the fine medium coal (-2mm) and the coarse coal slime (1-0.2mm) enter the coal slime heavy medium system after strict de-mediuming or dehydration. The density of the coal slime heavy medium suspension is no longer affected by the combined medium diversion in the fine coal heavy medium. The fine coal and coarse coal slime medium systems are completely independent and do not interfere with each other. The sorting density can be flexibly adjusted according to the coal quality and clean coal ash content of the two, which helps to achieve the principle of maximizing yield and improve the total clean coal recovery rate.

[0037] The coarse coal slime (1-0.2mm) in the raw coal and the fine coal (-2mm) after crushing are sorted in the three-product heavy medium cyclone to obtain coarse clean coal, coarse medium coal and tailing coal slime. The undissociated coarse medium coal (2-0.2mm) is ground in the heavy medium and returned for sorting. The coarse medium coal is fully dissociated through closed-circuit grinding and recycling, and is discharged from the clean coal or tailing coal or dissociated to -0.2mm and discharged from the de-medium screen; under the protection of magnetite with stronger hardness and wear resistance, the adverse effects of its dissociated particle size on subsequent links are avoided.

[0038] In the coal slime heavy medium system, the coarse magnetite is discharged from the bottom flow magnetic concentrate after the classification of the heavy medium cyclone, and enters the grinding stage together with the coarse and medium coal. The heavy medium completes the preparation from coarse to fine while the coarse and medium coal is ground and dissociated, and realizes closed-loop circulation, which significantly improves the fineness of the heavy medium, the stability of the suspension and the sorting accuracy of the coarse coal slime.

[0039] The present invention completely integrates the medium coal dissociation and recovery link into the heavy medium separation process of coking coal raw coal and coarse coal slime, without the need for a separate medium coal recovery and separation link. It has the outstanding advantages of simple process, efficient separation, high clean coal recovery rate, low energy consumption, low operating cost, and significant economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 The present invention is a flow chart of a scarce coking coal heavy medium washing process for enhancing the dissociation and recovery of medium coal.

[0041] Figure 2 It is an enlarged diagram of the process flow of the fine coal heavy medium system in the present invention;

[0042] Figure 3 It is an enlarged diagram of the process flow of the coal slime heavy medium system in the present invention. DETAILED DESCRIPTION

[0043] The technical solution of the present invention is described in more detail below in conjunction with the embodiments.

[0044] Example 1

[0045] like Figure 1-Figure 3 As shown, a scarce coking coal heavy medium washing process for strengthening the dissociation and recovery of medium coal comprises the following steps:

[0046] Step a, fine raw coal sorting: the fine raw coal with a particle size of no more than 50 mm is sorted in a three-product fine coal heavy medium cyclone under the action of a qualified medium to obtain fine clean coal, fine medium coal and fine gangue;

[0047] Step b 1 , fine clean coal demediation: in step a, the fine clean coal is demediated by an arc screen and a demediation screen to obtain an arc screened medium, a demediation screened medium, a demediation screened medium, and an oversize; wherein the arc screened medium is divided into two parts by a diverter, the arc screened medium split 1 and the demediation screened medium are sent to the fine coal medium barrel together, the arc screened medium split 2 and the demediation screened medium are sent to the oversize medium barrel together, the arc screened medium split 2 generally takes 20% to 30% of the arc screened medium flow, and the oversize is used as a clean coal product after dehydration;

[0048] Step b 2 , de-mediating the fine and medium coal: in step a, the fine and medium coal is de-mediated by a curved screen and a de-mediating screen to obtain a curved screened medium, a de-mediating screened medium and a sieve-surface material; wherein the curved screened medium and the de-mediating screened medium are sent to a media barrel together, and the sieve-surface material is fed into a coal slime mixing barrel;

[0049] Step b 3 , the fine gangue is de-mediumed: in step a, the fine gangue is de-mediumed by a curved screen and a de-mediuming screen to obtain curved screen combined media, de-mediuming screen combined media, de-mediuming screen diluted media and screened material; wherein, the curved screen combined media and de-mediuming screen combined media are sent to the combined media barrel together; the de-mediuming screen diluted media is sent to the diluted media barrel, and the screened material is used as the fine gangue product.

[0050] In the above-mentioned process of removing the medium, step b 1 and b 3 The de-mesh screen used is set up in two sections. The first section is close to the feeding end, accounting for 1 / 3 of the total length of the de-mesh screen, with a sieve hole of 0.5mm; the second section is close to the discharging end, accounting for 2 / 3 of the total length of the de-mesh screen, with a sieve hole of 1.0mm. The second section is also equipped with a water spray, and the water spray volume is 1.2-2.0m 3 / t. Step b 2The de-mediating screen used is set into two sections. The first section is close to the feeding end and occupies 1 / 3 of the total length of the de-mediating screen. The second section is close to the discharging end and occupies 2 / 3 of the total length of the de-mediating screen. The sieve holes of the de-mediating screen are all 0.5mm. No water spraying is set and the moisture content of the discharging material is controlled within 10%.

[0051] Step c, crushing of the final coal: Step b 2 The material on the medium-sized screen is fed into a hammer crusher and crushed to less than 2 mm. After crushing, the material is fed into a coal slime mixing barrel for coal slime heavy medium separation.

[0052] Step d, dehydration of fine coal in dilute medium: Step b 1 Middle arc screen combined with medium diversion 2 and de-medium screen thinning, step b 3 The thin media on the medium de-mediating screen is buffered by the thin media barrel and then pumped to the dewatering screen for 0.2mm dehydration to obtain the oversize and undersize water.

[0053] Step e, dilute medium magnetic separation: the undersize water in step d is fed into a magnetic separator for the first magnetic separation to obtain magnetic concentrate and magnetic tailings; the magnetic concentrate is returned to the fine coal medium barrel, and the magnetic tailings are used as coal slime water for subsequent flotation operations;

[0054] Step f, coal slime heavy medium separation: the screened material in step d and the crushed material in step c are buffered in a mixing barrel and then pumped to the three-product coal slime heavy medium cyclone group for separation to obtain coarse clean coal, coarse medium coal and coarse tailings;

[0055] Step g 1 , Coarse and clean coal de-mediation: In step f, the coarse and clean coal is fed into a double-layer curved screen for de-mediation to obtain an oversize and undersize combined medium; a split flow is set for the undersize combined medium, and the ratio of the coal slime mixing barrel or the coarse and clean coal magnetic separator is adjusted according to the coal quality, sorting density, suspension characteristics, etc. The undersize combined medium split flow 2 generally takes 25% to 35% of the total undersize combined medium flow, wherein the undersize combined medium split flow 1 is removed to the coal slime mixing barrel, and the undersize combined medium split flow 2 and the oversize are removed together for the coarse and clean coal magnetic separation operation;

[0056] Step g 2 , De-mediation of coarse and medium coal: In step f, the coarse and medium coal is fed into a double-layer curved screen for de-mediation to obtain oversize and undersize mixed media; the oversize is sent to the grinding operation, and the undersize mixed media is sent to the coal slime mixing barrel;

[0057] Step g 3 , coarse tailings magnetic separation: in step f, the coarse tailings are fed into a magnetic separator for a second magnetic separation, and water is added to adjust the feed concentration of the magnetic separator to between 15 and 25wt% to obtain magnetic concentrate and magnetic tailings; wherein the magnetic concentrate is subjected to grinding operation, and the magnetic tailings are graded and dehydrated as coarse tailings slime products.

[0058] The mesh size of the double-layer curved sieve used in the above step g1 and step g2 is 0.35 mm, and the interception particle size is between 0.2 and 0.25 mm.

[0059] Step h, grinding operation: Step g 2 Medium sieve, step g 3 The medium magnetic concentrate and the supplementary magnetite powder and water are ground and dissociated together, and the materials after grinding are fed into the coal slime mixing tank;

[0060] In this step, a rod mill is used for grinding, and the feed mass concentration is controlled at 45-55wt%, and the ore particles with a particle size of less than 0.074mm in the material after grinding account for more than 80% of the total material mass content. The amount of magnetite powder and water added is determined according to the loss amount from the tailings and products in the medium system to maintain the dynamic balance and stability of the medium system.

[0061] Step i, coarse and clean coal magnetic separation: Step g 1 The material on the middle screen and the combined medium under the screen are fed into the clean coal magnetic separator for the third magnetic separation, and water is added to adjust the feed concentration of the magnetic separator between 15 and 25wt% to obtain magnetic fines and magnetic tails; wherein the magnetic tails are used as coarse clean coal products after classification and dehydration, and the magnetic fines are set to split, and the split ratio is adjusted according to the control density of the fine coal combined medium barrel, wherein the magnetic fine split 1 goes to the fine coal combined medium barrel, and the magnetic fine split 2 goes to the coal slime mixing barrel;

[0062] Step j, mixing of fine coal and medium: Step b 1 Middle arc screen media splitter 1 and de-screen media, step b 2 Middle arc screen and stripping screen, step b 3 The middle arc screening medium and the de-screening medium, and the magnetic fine separation 1 in step i are buffered in the fine coal medium barrel and returned to step a as qualified medium; the buffering includes adjusting the density, with the first stage separation of the three-product coal slime heavy medium cyclone as the goal, determined according to the ash content and coal quality of the fine coal, and generally adjusted to between 1.35 and 1.45 kg / L.

[0063] Step k, coal slime mixing preparation: Step b 2 The material on the medium screen, the material on the medium screen in step d, the material on the medium screen in step g 1 Middle sieve and medium separation 1, step g 2 The mixed medium under the middle screen, the material after grinding in step h, and the magnetic fine fraction 2 in step i are mixed and fed into the coal slime mixing barrel, and returned to step f after buffering; the buffering includes adjusting the density, with the first stage sorting of the three-product coal slime heavy medium cyclone as the goal, determined according to the ash content and coal quality of the coarse and clean coal, and generally adjusted to between 1.40 and 1.50 kg / L.

[0064] Example 2

[0065] The present method was compared with the conventional process. The main characteristics are shown in Table 1, and the sorting indicators are shown in Table 2.

[0066] Table 1 Comparison of main features of different processes

[0067]

[0068] Table 2 Comparison of sorting indicators of different processes

[0069]

[0070]

[0071] By adopting the heavy medium washing process provided by the present invention, from the perspective of sorting effect, the coarse coal slime sorting accuracy E value and the flotation perfection index value of the present method are significantly improved compared with the traditional process; from the perspective of the coarse coal slime and flotation sorting amount, the coarse coal slime input amount is increased while the flotation input amount is reduced. Since the flotation cost is significantly higher than that of coarse coal slime, it means that the production cost of the present method is lower; from the perspective of total clean coal yield, the present method increases the yield by 0.52% compared with the traditional process, which is a huge improvement for the industry and can significantly increase economic benefits.

[0072] The above implementation modes are only used to illustrate the technical solutions of the present invention, but not to limit the present invention. Although the present invention has been described in detail with reference to the above implementation modes, those skilled in the art should understand that any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A scarce coking coal heavy medium washing process for enhancing the separation and recovery of medium coal, characterized in that: The following steps are involved: Step a, fine raw coal sorting: the fine raw coal with a particle size of no more than 50 mm is sorted in a three-product fine coal heavy medium cyclone under the action of a qualified medium to obtain fine clean coal, fine medium coal and fine gangue; Step b1, fine clean coal de-mediation: the fine clean coal in step a is de-mediated by a curved screen and a de-mediation screen to obtain curved screened combined media, de-mediation screened combined media, de-mediation screened thin media and screened oversize; wherein the curved screened combined media is divided into two parts by a diverter, the curved screened combined media split 1 and the de-mediation screened combined media are sent to the fine coal combined media barrel together, the curved screened combined media split 2 and the de-mediation screened thin media are sent to the thin media barrel together, and the screened oversize is dehydrated as a clean coal product; Step b2, de-mediating the fine and medium coal: the fine and medium coal in step a is de-mediated by a curved screen and a de-mediating screen to obtain a curved screened medium, a de-mediating screened medium and a screened material; wherein the curved screened medium and the de-mediating screened medium are sent to a media barrel together, and the screened material is fed into a coal slime mixing barrel; Step b3, removing the medium from the final gangue: in step a, the final gangue is removed by passing through an arc screen and a removing screen to obtain arc screen combined media, removing screen combined media, removing screen rare media and screen oversize; wherein the arc screen combined media and removing screen combined media are sent to a combined media barrel together; the removing screen rare media is sent to a rare media barrel, and the screen oversize is used as the final gangue product; Step d, dehydration of fine coal: the arc-shaped screen combined medium splitter 2 in step b1 is dehydrated with the dehydration screen, and the dehydration screen dehydration medium in step b3 is buffered in the dehydration barrel and then pumped to the dehydration screen for dehydration to obtain the screen material and the screen water; Step e, dilute medium magnetic separation: the undersize water in step d is fed into a magnetic separator for the first magnetic separation to obtain magnetic concentrate and magnetic tailings; the magnetic concentrate is returned to the fine coal medium barrel, and the magnetic tailings are used as coal slime water for subsequent flotation operations; Step f, coal slime heavy medium separation: the oversize in step d and the oversize on the de-medium screen in step b2 are buffered in a mixing barrel and then pumped to the three-product coal slime heavy medium cyclone group for separation to obtain coarse clean coal, coarse medium coal and coarse tailings; Step g1, coarse clean coal de-mediation: the coarse clean coal in step f is fed into a double-layer curved screen for de-mediation to obtain an oversize and undersize mixed medium; the undersize mixed medium is divided into two streams, the undersize mixed medium stream 1 is sent to the coal slime mixing barrel, and the undersize mixed medium stream 2 is sent to the coarse clean coal magnetic separation operation together with the oversize; Step g2, de-mediation of coarse and medium coal: the coarse and medium coal in step f is fed into a double-layer curved screen for de-mediation to obtain oversize and undersize mixed medium; the oversize is sent to the grinding operation, and the undersize mixed medium is sent to the coal slime mixing barrel; Step g3, magnetic separation of coarse tailings: the coarse tailings in step f are fed into a magnetic separator for a second magnetic separation to obtain magnetic concentrate and magnetic tailings; wherein the magnetic concentrate is subjected to grinding operation, and the magnetic tailings are graded and dehydrated as coarse tailings slime products; Step i, coarse and clean coal magnetic separation: the oversize and undersize combined medium split 2 in step g1 are fed into the clean coal magnetic separator for the third magnetic separation to obtain magnetic concentrate and magnetic tail; wherein the magnetic tail is graded and dehydrated as the coarse and clean coal product, and the magnetic concentrate is set to split, the magnetic concentrate split 1 is to go to the fine coal combined medium barrel, and the magnetic concentrate split 2 is to go to the coal slime mixing barrel; Step j, blending of fine coal mixed medium: the arc-shaped screened mixed medium split 1 and the de-screened mixed medium in step b1, the arc-shaped screened mixed medium and the de-screened mixed medium in step b2, the arc-shaped screened mixed medium and the de-screened mixed medium in step b3, and the magnetic fine split 1 in step i are buffered in the fine coal mixed medium barrel and returned to step a as qualified medium; Step k, preparation of coal slime mixture: the screened material on the de-screen in step b2, the screened material in step d, the under-screen combined medium fraction 1 in step g1, the under-screen combined medium in step g2, the ground material in step h, and the magnetic concentrate fraction 2 in step i are mixed and fed into the coal slime mixing barrel, and returned to step f after buffering.

2. A scarce coking coal heavy medium washing process for enhancing the separation and recovery of medium coal as claimed in claim 1, characterized in that: The process also includes step c, which is the crushing of the fine coal: the material on the de-sieve from step b2 is first crushed by a crusher before being fed into the coal slime mixing barrel. The crusher is a reversible impact hammer crusher, which crushes the material on the sieve to a particle size of less than 2 mm.

3. A scarce coking coal heavy medium washing process for enhancing the separation and recovery of middling coal as claimed in claim 1, characterized in that: The method further includes step h, which is a grinding operation, wherein the screened material from step g2, the magnetic concentrate from step g3, and the supplemented magnetite powder and water are ground and separated together, and the ground materials are then fed into a de-sludging mixing barrel.

4. A scarce coking coal heavy medium washing process for enhancing the separation and recovery of middling coal as claimed in claim 3, characterized in that: In the step h, a rod mill is used for the grinding operation, and the feed mass concentration is controlled at 45-55wt%, and the ore particles with a particle size of less than 0.074mm in the material after grinding account for more than 80% of the total material mass content. The amount of supplementary magnetite powder and water is determined according to the loss amount from the tailings and products in the medium system to maintain the dynamic balance and stability of the medium system.

5. A scarce coking coal heavy medium washing process for enhancing the separation and recovery of middling coal as claimed in claim 1, characterized in that: In the steps b1 and b3, the de-mesh screen is provided with two sections, the first section is close to the feeding end, occupies 1 / 3 of the total length of the de-mesh screen, and has a sieve hole of 0.5 mm; the second section is close to the discharging end, occupies 2 / 3 of the total length of the de-mesh screen, and has a sieve hole of 1.0 mm. The second section is also provided with a water spray, and the water spray volume is 1.2-2.0 m 3 / t. In step b2, the de-mediating screen is provided with two sections, the first section is close to the feeding end and occupies 1 / 3 of the total length of the de-mediating screen, and the second section is close to the discharging end and occupies 2 / 3 of the total length of the de-mediating screen. The sieve holes of the de-mediating screen are all 0.5 mm.

6. A scarce coking coal heavy medium washing process for enhancing the separation and recovery of middling coal as claimed in claim 2, characterized in that: In the step d, the cut-off particle size of the dewatering screen is 0.2 mm.

7. A scarce coking coal heavy medium washing process for enhancing the separation and recovery of middling coal as claimed in claim 1, characterized in that: In the steps g1 and g2, the mesh size of the double-layer curved screen is 0.35 mm, and the interception particle size is between 0.2 and 0.25 mm.

8. A scarce coking coal heavy medium washing process for enhancing the separation and recovery of middling coal as claimed in claim 1, characterized in that: In the second magnetic separation and the third magnetic separation, water is added to adjust the feed concentration of the magnetic separator to be between 15 and 25 wt%.

9. A scarce coking coal heavy medium washing process for enhancing the separation and recovery of middling coal as claimed in claim 1, characterized in that: In the step j, the density of each material fed into the fine coal mixing barrel is regulated to be between 1.35 and 1.45 kg / L with the first stage sorting of the three-product coal slime heavy medium cyclone as the target; in the step k, the density of each material fed into the coal slime mixing barrel is regulated to be between 1.40 and 1.50 kg / L with the first stage sorting of the three-product coal slime heavy medium cyclone as the target.

10. A scarce coking coal heavy medium washing process for enhancing the separation and recovery of middling coal as claimed in claim 1, characterized in that: In the step b1, the arc-shaped screen medium is divided into two parts by a diverter, wherein the arc-shaped screen medium diverter 2 accounts for 20% to 30% of the arc-shaped screen medium flow rate; in the step g1, the under-screen medium is set to divert, wherein the under-screen medium diverter 2 accounts for 25% to 35% of the under-screen medium flow rate; in the step i, the diversion ratio of the magnetic fine diverter 1 and the magnetic fine diverter 2 is adjusted according to the control density of the fine coal medium barrel.

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