CN116159663A - Power coal washing and selecting process for reducing coal slime and improving quality - Google Patents

Abstract

The invention provides a coal slime reduction and upgrading power coal washing and selecting process, which comprises a dry-method powder removing system, a main selecting system, a novel flotation system, a coal slime homogenizing system and a tail coal processing system, and is characterized in that the process adopts a measure of combining a cross sieve dry-method powder removing process and a novel flotation process, the cross sieve is arranged in front of the main selecting system to dry-method powder removing the raw coal, and the removed pulverized coal is directly mixed into a main selecting product; the primary slime which is not completely removed by dry method powder removal and the secondary slime generated in the washing and selecting process are upgraded by the novel flotation system, the flotation clean coal is processed into loose materials by the slime homogenizing system, the amount of the slime can be reduced by about 50% in the dry method powder removal link, the feeding slime can be recovered by about 60% in the flotation link, the comprehensive recovery rate of the slime can reach about 80%, the ash content of the tail coal which is removed by the novel flotation system can reach more than 75%, and the recovery rate of the clean coal can be improved by 8-10% compared with the conventional flotation process.

Description

Power coal washing and selecting process for reducing coal slime and improving quality

Technical Field

The invention relates to the technical field of coal washing and selecting processing, in particular to a power coal washing and selecting process which is mainly characterized by reducing the amount of coal slime in the coal washing and selecting process and further improving quality and recycling the coal slime.

Background

In recent years, the washing and selecting rate of the power coal is gradually improved, most of the power coal at present adopts a lump coal full-size-fraction washing and selecting process, and the combined separation of a heavy medium shallow tank and a heavy medium cyclone is usually carried out, a large amount of fine slime (the main size fraction is-0.25 mm) is inevitably generated in the washing and selecting process, and the slime yield can generally be about 8-12% of the total amount of raw coal. The dynamic coal has the characteristics of low deterioration degree, easy mud formation of gangue, high ash content (35-50%), high water content (25-30%) and low heat value (1500-3000 kcal/kg), and after the flocculant is added in the concentration and sedimentation process of the coal slime water, the coal slime is easy to bond and difficult to crush, and the physical property is in a bulk shape or a cake shape, so that the coal slime is difficult to uniformly mix with the products of a main separation system, is generally directly sold as low-value products, is even directly discharged by partial coal separation plants, and causes great resource waste and environmental pollution.

At present, a part of power coal preparation plants adopt a dry-method powder removal and then washing and selecting process, the process can generally reduce about 30-50% of coal slime, but a considerable amount of coal slime still enters a washing and selecting system and is not recycled efficiently. Coal slime flotation is the most effective way to upgrade fine coal slime at present, and has been widely used in coking coal washing and separation. However, the power coal type is mainly long flame coal or non-caking coal, the slime characteristics and the product quality requirements of the power coal type are greatly different from those of coking coal, the flotation process directly adopting coking coal is poor in separation effect, the ash content of flotation tail coal is low (generally about 60%), the recovery rate of clean coal is low (generally about 35-40%), and the economic benefit is not obvious, so that the application of the current power coal flotation process is still immature.

In view of the current state of the dynamic coal washing and selecting process, a washing and selecting process combining coal slime reduction and efficient quality improvement is researched, and the method has obvious economic and environmental benefits.

Disclosure of Invention

The invention aims to provide a dynamic coal washing process for reducing and improving the quality of coal slime, which mainly solves the technical problems in the prior art by combining a cross screen dry-method powder removing system, a novel flotation system and a coal slime homogenizing system.

The invention provides a coal slime reduction and upgrading power coal washing and selecting process, which comprises a dry method powder removing system, a main selecting system, a novel flotation system, a coal slime homogenizing system and a tail coal treatment system; the process adopts a measure of combining a cross screen dry method powder removal process and a novel flotation process to realize washing and selecting, specifically, a cross screen is arranged in front of the main selection system to carry out dry method powder removal on raw coal, and the removed pulverized coal is directly mixed into a main selection product; carrying out quality improvement on the raw coal slime which is not completely removed by dry-method powder removal and the secondary coal slime generated in the washing process through a novel flotation system; the washing and selecting process comprises the following steps: raw coal (with the granularity of 150-0mm in general) subjected to preliminary crushing and impurity removal enters a cross sieve to be subjected to 3mm dry-process powder removal, and oversize materials (+3 mm grain grade) of the cross sieve enter a main selection system to be selected, so that products and gangue are obtained; directly mixing undersize pulverized coal (-3 mm grain grade) into main selection product; the slime water generated by the main separation system enters a novel flotation system for separation, the flotation clean coal is mixed with products after being treated by a slime homogenizing system, the flotation tail coal enters a tail coal treatment system, and the treated tail coal and gangue are discharged together.

Further, the dry powder removing equipment is a cross screen, the powder removing size is 3mm, a relaxation screen or other type classification equipment is not adopted, the dry powder removing equipment can be in a mode that the cross screen and the vibrating screen are combined, the vibrating screen performs 13-25 mm classification, and the undersize enters the cross screen to perform 3mm powder removing; the dry powder removing equipment can also directly adopt a two-section cross sieve to remove powder by 3mm in one section; the oversize material enters the second section for 13-25 mm classification.

Further, the novel flotation system comprises a surface modification process link, a desliming process link, a first-stage flotation process link and a second-stage flotation process link.

As a preferable scheme, the surface modification process link comprises two steps: step one: the stirring method is adopted to enable the slime water to move at a high speed, under the friction and shearing actions, the hydrophobic organic functional groups of the coal are fully exposed on the surface, and the difference of the hydrophobicity of the coal and gangue particles is increased, so that the floatability of the gangue is improved; step two: emulsifying the flotation reagent, and fully mixing the flotation reagent with the coal slurry through a mechanical type or a drop type to ensure that the coal particles obtain sufficient flotation time.

Further, the desliming process step adopts a desliming machine to discharge high-ash fine mud with granularity less than or equal to 45 mu m and ash content more than or equal to 75% in flotation feed in advance, and the desliming material is diluted by water and enters a first section of flotation process step.

As a preferable scheme, the first-stage flotation process link and the second-stage flotation process link are completed by adopting two links of concentration and scavenging, and tailings produced by the first-stage flotation process link are fed materials of the second-stage flotation process link.

As a preferable scheme, the three links of desliming, primary flotation and secondary flotation all take tailing ash as the primary control target of process operation.

Further, the coal slime homogenizing system comprises a clean coal dehydration link and a coal slime crushing link, wherein filtrate generated in the clean coal dehydration link is used as dilution water for feeding in a section of flotation process link, and the coal slime crushing link is realized by combining a screw conveyor and a coal slime crusher.

By adopting the technical scheme, the invention has the following beneficial effects:

the invention provides a coal slime reduction and quality improvement power coal washing process, which realizes the washing and selection of power coal through the measures of combining a cross screen dry-method powder removal system, a novel flotation system and a coal slime homogenizing system, wherein the coal slime amount can be reduced by about 50% in a dry-method powder removal link, about 60% of the feed coal slime can be recovered in a flotation link, the comprehensive recovery rate of the coal slime can reach about 80%, and the quality and physical properties of the coal slime are greatly improved; the ash content of the tail coal discharged by the novel flotation system can reach more than 75%, the recovery rate of the clean coal can be improved by 8-10% compared with the conventional flotation process, and the resource utilization rate is greatly improved.

Drawings

FIG. 1 is a process flow diagram of the present invention.

Detailed Description

The invention is further explained below with reference to the drawings:

as shown in fig. 1, the embodiment provides a dynamic coal washing process for reducing and improving the coal slime, which mainly realizes washing through measures of combining a cross screen dry-process powder removing system, a novel flotation system and a coal slime homogenizing system, and comprises a dry-process powder removing system, a main separation system, a novel flotation system, a coal slime homogenizing system and a tail coal processing system, wherein the washing steps are as follows:

step S1, a dry powder removing system: raw coal (with the granularity of 150-0mm in general) after preliminary crushing and impurity removal enters a cross screen to be subjected to 3mm dry-method powder removal, oversize materials (+3 mm size fraction) of the cross screen enter a main selection system, and undersize pulverized coal (-3 mm size fraction) is doped into a main selection product.

The main reason for setting the dry powder removal level to 3mm is that: the process link basically aims at removing coal slime (generally refers to the particle size of-0.5 mm), obviously, the smaller the particle size of the coal slime is, the more accords with the process target, but under the current technical condition, the minimum particle size of the coal slime which can be achieved by industrial application equipment under the condition of ensuring the powder removing efficiency is 3mm, so that 3mm is the optimal choice under the current technical condition.

The dry powder removing equipment adopts a cross screen, and does not adopt a relaxation screen or other types of classifying equipment, because the effect of the screening equipment of other types is lower than that of the cross screen when the screening equipment is used for 3mm powder removing.

Because the main power coal selecting system generally adopts a block and powder coal grading and selecting mode, the oversize products after dry powder removal need to be further graded, the implementation mode can be a mode that a cross screen and a vibrating screen are combined, the vibrating screen is graded by 13-25 mm, and the undersize products enter the cross screen to be subjected to 3mm powder removal; or directly adopting a two-section cross sieve, and carrying out 3mm powder removal on one section; the oversize material enters the second section for 13-25 mm classification.

The powder removal efficiency of the cross screen is different according to the factors such as the moisture content, the granularity composition, the powder removal size grade and the like of raw coal, but generally at least more than 60%, and the coal slime of a coal preparation plant can be reduced by at least more than 50% after the powder removal of the cross screen, so that the dry powder removal effect on the coal slime reduction is remarkable.

Step S2, a main selection system: the classified and descaled lump and fine raw coal enters a main separation system, and the process generally comprises lump coal washing, fine coal washing and coarse slime washing by adopting the prior known technology to finally obtain lump clean coal, fine clean coal and gangue. Wherein the lump coal washing and selecting can be realized through a heavy medium shallow groove; the washing and selecting of the pulverized coal can be realized through a heavy medium cyclone; the coarse slime washing and separation can be realized by a spiral separator or a disturbing bed separator (TBS).

The slime water generated by the main separation system enters the novel flotation system, the slime water mainly comes from overflow of the classification cyclone, and the main solid is slime with the diameter of 0.25-0 mm.

Step S3, a novel flotation system: the power coal slime has the characteristics different from coking coal, and different technological measures need to be adopted in a targeted way, and mainly comprises the following steps:

(1) the surface of the coal slime has more oxygen-containing functional groups, strong hydrophilicity and poor floatability, so that surface modification measures are needed to be adopted in advance;

(2) because of the influence of factors such as coal quality, gangue sliming and the like, the content of high-ash fine slime in the power coal slime is generally very high, and it is well known that coarse particles and fine particles need different hydrodynamic environments in the flotation process, and coarse-grain high-efficiency flotation is difficult to realize in the same equipment at the same time, so that classification treatment is needed;

(3) the main control index of the coking coal flotation process is clean coal ash, and the main control index of the dynamic coal flotation process is tail coal ash, namely the clean coal recovery rate is the primary target, so that a flotation rate and a reagent system different from those of the dynamic coal are needed.

Based on the above factors, the flotation system of the process of the present invention comprises: a surface modification process link, a desliming process link, a first-stage flotation process link and a second-stage flotation process link;

step S3.1, the surface modification process link comprises the following two steps: step one: the stirring method is adopted to enable the slime water to move at a high speed, under the friction and shearing actions, the hydrophobic organic functional groups of the coal are fully exposed on the surface, and the difference of the hydrophobicity of the coal and gangue particles is increased, so that the floatability of the gangue is improved; step two: emulsifying the flotation reagent, and fully mixing the flotation reagent with the coal slurry through a mechanical type or a drop type to ensure that the coal particles obtain sufficient flotation time.

Step S3.2, desliming: the high-ash fine mud with the granularity less than or equal to 45 mu m and the ash content more than or equal to 75% in the inlet material is discharged in advance before the main flotation process, so that the effect of the subsequent flotation operation is improved.

In this example, taking the test result of the granularity composition of a typical coal slime of a power coal preparation plant as an example, it can be seen from table 1: the 0.045mm size fraction has a coal slime content of more than 50% and its ash content is also significantly higher than the other size fractions, indicating that this size fraction contains a large amount of non-combustibles, and if it is directly subjected to flotation operation, the high ash slime must contaminate the flotation clean coal, so that preliminary desliming is necessary.

TABLE 1 test results of the particle size composition of a typical coal preparation plant coal slurry

Size fraction/mm	Yield/%	Ash/%	Cumulative yield/%	Cumulative ash/%
					+0.5	5.4	22.49	5.4	22.49
0.5-0.25	6.1	17.22	11.5	19.69
					0.25-0.125	10.1	16.50	21.6	18.20
0.125-0.074	9.9	14.30	31.5	16.97
					0.074-0.045	10.8	18.95	42.3	17.48
-0.045	57.7	52.28	100.0	37.55
					Totalizing	100.0	37.55	-	-

In the prior art, for the separation of the superfine particle size fraction, a hydraulic classification mode is generally adopted, such as a hydraulic cyclone or a deep cone thickener, but because a considerable part of low-ash coarse particles and high-ash fine particles have the same sedimentation end speed, mispairing matters are inevitably formed by adopting hydraulic classification, namely, part of low-ash clean coal is taken away from discharged fine mud.

Based on this, the embodiment performs desliming in advance by a desliming machine, which uses the working principle of flotation to realize the removal of high ash fine mud based on the difference of particle surface hydrophilicity instead of the specific difference of waterpower.

The desliming machine adopts a deep cone-like thickener structure, the upper part is square, the lower part is conical, a stirring device is arranged in the desliming machine, and the driving structure is positioned at the top of the machine body. The upper part of the desliming machine is provided with an overflow weir, and the lower conical part is provided with an inclined plate.

The process of removing the high ash fine mud is as follows: the desliming machine mainly comprises core components such as a machine body, a stirring device, an overflow collecting device, a tailing discharging device and the like, coal slime water automatically flows into the machine body from the middle lower part of one side of the desliming machine after being subjected to surface modification, medicines are added into the machine body and an incoming pipe, and air is filled through stirring of the stirring device. A hydrodynamic environment of low energy input, low shear force and weak turbulence is formed throughout the body. Unlike the overflow of the thickener to discharge fine particles, the low ash material in the desliming machine is driven by bubbles to be discharged from the overflow collecting device, and the high ash fine mud is gradually deposited at the bottom of the machine body and is discharged through the tailing discharging device. The inclined plate at the bottom of the desliming machine is used for further preventing bubbles from carrying low ash materials attached to the bubbles to enter the tailing port.

Steps S3.3 and S3.4, a primary flotation process link and a secondary flotation process link: and (3) carrying out concentration and scavenging on the desliming material, namely, after the concentrate is recovered in the first section, enabling the tailings to enter the second section flotation process link, and further recovering the concentrate.

The preferable implementation mode of the primary flotation process link and the secondary flotation process link adopts a micro-bubble flotation machine, and the primary control target of the process operation is the tailing ash content of the primary process links of the primary flotation process link and the secondary flotation process link.

The specific flotation process is as follows:

1. the two sections of micro-bubble flotation machines have the same integral structure and respectively comprise a feed pump, a barrel body, a distributor, a mineralizer, a spray head, a tailing tank and other core components, and the two sections are different in that the first section and the second section adopt different hydrodynamic environments and medicament systems.

The desliming coal slime water is sucked by a pump, and the medicament is added in the desliming process, so that the flotation process only needs to supplement a small amount of medicament according to the requirement. After the ore pulp is aerated and mineralized by the distributor, the ore pulp is released in the barrel body through the spray head, and the bubbles carry clean coal to float to the surface to finish the fine selection.

And discharging the first-stage flotation tailings into a second-stage flotation machine through a tail coal box, and extracting the rest clean coal to finish scavenging.

The process of the invention requires more medicament consumption than the conventional flotation process because medicaments are required to be added in the desliming, primary flotation and secondary flotation processes. Through experiments, the total reagent consumption is increased by about 30% compared with the conventional flotation process, and the unit coal slime flotation cost is increased by about 15% compared with the conventional process.

However, the method can greatly reduce the loss of the refined coal mismatched into the tail coal through four sub-links of surface modification, desliming and primary and secondary flotation, so that the ash content of the flotation tail coal reaches more than 75%, the recovery rate of the refined coal can be improved by 8-10 percent compared with the conventional flotation process, the income of the refined coal is far greater than the increase of the cost, and the method has remarkable economic benefit. For example, taking a coal preparation plant with 500 ten thousand t/a processing capacity as an example, the process can be used for recycling about 40 ten thousand t per year of clean coal with a heating value of about 4000-4500kcal/kg, which is equivalent to recycling 24 ten thousand t of standard coal per year, and reducing carbon dioxide emission by about 60 ten thousand t per year, the recycling standard is not limited to this, and the data can be listed according to actual data of the coal preparation plant only to show the difference between the technical effect of the invention and the prior art.

Step S4, a coal slime homogenizing system: the method comprises two links of clean coal dehydration and coal slime crushing, and aims to dehydrate and scatter flotation clean coal into loose materials, so that the loose materials are convenient to uniformly blend into main selected products.

Step S4.1, dehydration of clean coal: the known technology is adopted to dewater the flotation clean coal, the preferable implementation mode is a filter press, and wind or water is adopted as a squeezing medium. The filtrate produced by the filter pressing of the clean coal is used as the dilution water for the primary flotation.

Step S4.2, crushing coal slime: in order to improve the physical properties of the dehydrated flotation clean coal, the flotation clean coal is preferably scattered into loose materials by combining a screw conveyor and a coal slime crusher, so that the loose materials are convenient to uniformly blend into main selected products.

The coal slime crushing process is as follows:

for raw coal slime, namely coal slime which is not separated, because flocculant is added during concentration, the viscosity is strong, and the coal slime is in a cake shape after filter pressing and dehydration, so that the coal slime is difficult to crush. However, the flotation clean coal is not concentrated, no flocculant is added, and the sticky shale mud in the clean coal is very little, so the flotation clean coal is easy to crush. The dehydrated clean coal filter cake firstly enters a screw conveyor and is conveyed forward, and meanwhile, the coal slime is decomposed into small blocks from cake shapes through the rotation of a screw impeller. Small block-shaped clean coal enters a coal slime crusher, and blades capable of rotating rapidly are arranged inside the coal slime crusher. Unlike common crusher, which realizes crushing of material through extrusion or shearing, the coal slime crusher is to impact the material with blades to disperse the material naturally. The homogenized flotation clean coal has similar loose characteristics as the main product and can be easily and uniformly mixed into the main product.

Step S5, a tail coal treatment system: the flotation tailing is treated by adopting the current common concentration and dehydration technology, and the dehydrated tailing and gangue are discharged together.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

Claims (4)

1. The dynamic coal washing and selecting process for reducing coal slime and improving quality comprises a dry-method powder removing system, a main selecting system, a novel flotation system, a coal slime homogenizing system and a tail coal processing system, and is characterized in that the process adopts a measure of combining a cross sieve dry-method powder removing process and a novel flotation process, the cross sieve is arranged in front of the main selecting system to dry-method powder removing the raw coal, and the removed pulverized coal is directly mixed into a main selecting product; the primary slime which is not completely removed by dry method powder removal and the secondary slime generated in the washing and selecting process are upgraded by the novel flotation system, and the flotation clean coal is processed into loose materials by the slime homogenizing system; the washing process specifically comprises the following steps: raw coal subjected to preliminary crushing and impurity removal enters a cross sieve to be subjected to 3mm dry-process powder removal, and oversize materials (+ 3mm grain grade) of the cross sieve enter a main selection system to be selected to obtain products and gangue; directly mixing undersize pulverized coal (-3 mm grain grade) into main selection product; the slime water produced by the main separation system enters a novel flotation system for separation, the flotation clean coal is processed into loose materials by a slime homogenizing system and then is mixed into products, the flotation tail coal enters a tail coal processing system, and the processed tail coal and gangue are discharged together.

2. The washing process according to claim 1, wherein the dry powder removal equipment is a cross screen, and the powder removal size fraction is 3mm.

3. The flotation process according to claim 1, wherein the novel flotation system comprises a surface modification process step, a desliming process step, a primary flotation process step, a secondary flotation process step;

the desliming process link adopts a desliming machine to discharge high-ash fine mud with granularity less than or equal to 45 mu m and ash content more than or equal to 75% in flotation feed in advance, and the desliming material is diluted by water and enters a section of flotation;

the first-stage flotation process link and the second-stage flotation process link are completed by adopting two links of carefully selecting and scavenging, and tailings generated by the first-stage flotation process link are used as feed materials of the second-stage flotation process link;

the desliming process link, the primary flotation process link and the secondary flotation process link all take tailing ash as primary control targets of process operation.

4. The washing process according to claim 1, wherein the slime homogenizing system comprises a clean coal dehydration link and a slime crushing link; the filtrate discharged from the clean coal dehydration step is used as the dilution water of the feed in the step of the primary flotation process; the coal slime crushing link is realized by combining a screw conveyor and a coal slime crusher.

Images