Coal gasification slag resource recovery method

Abstract

The application provides a coal gasification slag resource recovery method, comprising: screening coal gasification slag according to particle size to obtain coarse particle ash slag and fine particle ash slag. The fine particle ash slag is thickened and then subjected to gravity separation to obtain a first underflow and a first overflow. The first underflow is treated to obtain carbon fine powder, decarburized tailings and to-be-treated ash slag. The to-be-treated ash slag and the first overflow are thickened and then subjected to gravity separation to obtain flotation ash slag meeting flotation conditions and to-be-flotation ash slag not meeting flotation conditions. The flotation ash slag meeting flotation conditions is subjected to flotation, and carbon fine powder and decarburized tailings are obtained through treatment. Through particle size grading, gravity separation and flotation of the coal gasification slag, the combined process saves operation cost and realizes efficient carbon-ash separation of the coal gasification slag. The above method has mild conditions, simple and easily obtained equipment requirements, low energy consumption, high recovery rate and good market prospect.

Description

Technical Field

[0001] The present application relates to the technical field of coal gasification slag resource recovery, and in particular to a method for coal gasification slag resource recovery. Background Art

[0002] Coal remains a dominant source of energy in my country and a cornerstone of national energy security. Given the relative scarcity of oil and natural gas resources in my country, coal gasification technology, as a highly efficient means of coal conversion, holds crucial strategic importance for achieving clean and efficient coal utilization.

[0003] Gasifiers are a key process and technical unit in the coal chemical industry, generating large quantities of gasification slag. Currently, my country produces over 70 million tons of gasification slag annually, with hundreds of millions of tons accumulated. However, the overall utilization rate is low, with the waste primarily disposed of through landfills or slag dumps. This not only occupies significant land, pollutes soil and water, but also wastes resources and energy. Summary of the Invention

[0004] The present application provides a method for recycling coal gasification slag to solve at least some of the problems in the related art.

[0005] The embodiments of the present application provide a method for recycling coal gasification slag, comprising:

[0006] The coal gasification slag is screened according to the particle size to obtain coarse ash particles and fine ash particles;

[0007] The fine-grained ash is mixed with a slurry and then re-selected to obtain a first underflow and a first overflow;

[0008] reselecting the first underflow to obtain a second underflow and a second overflow;

[0009] Screening the second overflow according to particle size to obtain coarse-grained first ash and fine-grained third ash; centrifuging the third ash to obtain carbon powder;

[0010] Screening the second underflow according to particle size to obtain coarse-grained second ash and fine-grained fourth ash; dehydrating the fourth ash to obtain decarbonized tailings;

[0011] using the first ash and the second ash as the ash to be processed;

[0012] grinding the first overflow;

[0013] Gravity separation is performed on the ash to be processed and the first overflow after grinding to obtain flotation ash that meets flotation conditions and ash to be floated that does not meet flotation conditions;

[0014] The flotation ash that meets the flotation conditions is floated and processed to obtain carbon concentrate and decarbonized tailings.

[0015] Optionally, a cyclic processing step is further included, and the cyclic processing step includes:

[0016] The ash to be floated that does not meet the flotation conditions is repeatedly ground and re-selected, and the flotation ash that meets the flotation conditions obtained after each grinding and re-selection is floated and processed to obtain carbon concentrate and decarbonized tailings.

[0017] Optionally, the flotation ash that meets the flotation conditions is subjected to flotation and processed to obtain carbon concentrate and decarbonized tailings, including:

[0018] The flotation ash that meets the flotation conditions is subjected to bubble flotation to obtain carbonaceous matter and tailings;

[0019] collecting and filtering the carbon-containing material to obtain carbon powder;

[0020] The tailings are concentrated and filter-pressed to obtain decarbonized tailings.

[0021] Optionally, the coal gasification slag is screened according to particle size to obtain coarse ash particles and fine ash particles, including:

[0022] Adding liquid to the coal gasification slag to form a first mixed slurry with a concentration of 35% to 65%;

[0023] The first mixed slurry is sieved according to particle size to obtain coarse ash particles and fine ash particles.

[0024] Optionally, the step of preparing the fine-grained ash into a slurry and then performing gravity separation to obtain a first underflow and a first overflow comprises:

[0025] Adding liquid to the fine-grained ash to form a second mixed slurry with a concentration of 10% to 30%;

[0026] The second mixed slurry is subjected to gravity selection to obtain a first underflow and a first overflow.

[0027] Optionally, the grading aperture range for screening the coal gasification slag is 0.5 mm to 1 mm; and / or

[0028] The classification aperture range for reselecting the fine ash particles is 0.074 mm to 0.15 mm; and / or

[0029] The frother used for flotation includes one of octanol and methyl isobutyl carbinol, with a dosage of 1-15 kg; and / or

[0030] The collector used for flotation includes one of diesel, kerosene, waste diesel, and waste engine oil, with a dosage of 1.5~18kg.

[0031] This application provides a method for recycling coal gasification slag by subjecting it to particle size classification, gravity separation, and flotation. This combined process achieves efficient carbon-ash separation from coal gasification slag while reducing operating costs. These methods all require mild conditions, require readily available equipment, have low energy consumption, and offer high recovery rates, promising promising market prospects.

[0032] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0034] Figure 1 Shown is a flow chart of a method for recycling coal gasification slag resources according to an exemplary embodiment of the present application;

[0035] Figures 2 to 6 Shown is a detailed flow chart of each step of the coal gasification slag resource recovery method of the present application;

[0036] Figure 7 Shown is a flow chart of a method for resource recovery of coal gasification slag according to another exemplary embodiment of the present application. DETAILED DESCRIPTION

[0037] Exemplary embodiments will be described in detail herein, with examples illustrated in the accompanying drawings. In the following description, when referring to the drawings, identical numerals in different figures represent identical or similar elements, unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present application, as detailed in the appended claims.

[0038] In order to better understand the technical solution of the present application, the coal gasification slag resource recovery method of the present application is described in detail below with reference to the accompanying drawings. In the absence of conflict, the features of the following embodiments and implementations can be combined with each other.

[0039] The embodiments of this application provide a method for recycling coal gasification slag, applicable to fine gasification slag. Gasification slag is generally divided into fine gasification slag and coarse gasification slag. Fine slag is carried out from the top of the gasifier by the coarse coal gas flow and subjected to preliminary washing, purification, and precipitation to obtain water-containing slag. It has characteristics such as high carbon content (18%-50%) and high water content (40%-65%).

[0040] See also Figure 1 As shown, the method for recycling coal gasification slag includes steps S1-S5:

[0041] In step S1, the coal gasification slag is screened according to particle size to obtain coarse ash particles (+a mm) and fine ash particles (-a mm). As will be understood, coarse ash particles have a high ash content, a low carbon content, and a diameter greater than a mm. Fine ash particles have a high carbon content, a low ash content, and a diameter less than a mm. In this embodiment, the grading aperture used for screening the coal gasification slag ranges from a = 0.5 mm to 1 mm.

[0042] In step S2, the fine ash is mixed with a slurry and then subjected to gravity separation (gravity separation), producing a first underflow (b mm - a mm) and a first overflow (-b mm). Optionally, the fine ash can be fed into a classifying cyclone for gravity separation. As will be understood, a classifying cyclone is a type of gravity separation device. When the mixed slurry enters the cyclone tangentially from its periphery at a certain pressure, a high-speed rotating flow field is generated within the cylindrical chamber. Due to centrifugal force, particles with higher density or coarser particle size are flung toward the vessel wall and move downward axially and radially, ultimately discharging through the underflow outlet. The resulting first underflow has a high ash content, low carbon content, high density, large weight, and a diameter between 8 mm and 1 mm. Particles with lower density or finer particle size move toward the central axis, forming an upward internal vortex at the center of the axis, and are subsequently discharged through the overflow outlet. The resulting first overflow has a high carbon content, low ash content, low density, small weight, and a diameter less than b mm. This achieves efficient separation of the light and heavy phases in the mixed slurry; where b is less than a. In this embodiment, the classification aperture range for reselecting the fine-particle ash is b=0.074mm~0.15mm.

[0043] Step S3: Processing the first underflow to obtain carbon concentrate, decarbonized tailings, and ash to be processed, thereby achieving efficient carbon-ash separation.

[0044] In step S4, the ash to be processed and the first overflow are mixed and then subjected to gravity separation to obtain flotation ash that meets flotation conditions and ash to be floated that does not meet flotation conditions. Optionally, a classifying cyclone can be used for gravity separation.

[0045] In step S5, the flotation ash that meets the flotation conditions is floated and processed to obtain carbon powder and decarbonized tailings. It can be understood that the cost of screening and re-selection is low, and the carbon extraction efficiency of flotation is high, but the reagent consumption is large and the production cost is high. Therefore, the present application first processes most of the gasification slag through the previous screening and re-selection steps to obtain carbon powder and decarbonized tailings, saving operating costs. The remaining small part of the gasification slag is then floated and processed to obtain carbon powder and decarbonized tailings, thereby achieving efficient carbon ash separation and reducing production costs, while meeting product quality requirements and taking into account economic benefits.

[0046] Through the above method, the coal gasification slag resource recovery method provided by the present application is a coal gasification fine slag classification-gravity selection-flotation combined carbon ash separation process, which belongs to the technical field of coal-based solid waste resource recovery of high-value components. By subjecting the coal gasification slag to particle size classification, gravity selection and flotation, large-particle gasification slag is separated by gravity, and small-particle gasification slag is separated by bubble flotation to obtain carbon concentrate and decarbonized tailings products. The combined process saves operating costs while achieving efficient carbon ash separation of coal gasification slag. The above methods all have mild conditions, simple and easy-to-obtain equipment requirements, low energy consumption, high recovery rate, and good market prospects.

[0047] The coal gasification slag resource recovery method provided in this application, through the implementation of a carbon-ash separation project for coal gasification fine slag, can achieve dual benefits: on the one hand, high-calorific-value carbon fines can be recovered as a substitute for thermal coal, pulverized coal injection, or for the preparation of carbon-based adsorbents; on the other hand, the decarbonized tailings can be used as a building material raw material for resource disposal. Therefore, the coal gasification slag carbon-ash separation technology not only effectively solves the problem of coal gasification fine slag disposal, but also promotes resource recycling and improves energy efficiency.

[0048] See also Figure 2 As shown, in some optional embodiments, the above step S1, screening the coal gasification slag according to the particle size to obtain coarse ash and fine ash, may include steps S11-S12:

[0049] Step S11: Add liquid to the coal gasification slag to form a first mixed slurry with a concentration of 35% to 65%. Alternatively, the coal gasification slag can be fed into a slurry mixing tank and slurried with the supernatant of the gasification ash water to form a first mixed slurry with a concentration of 35% to 65%.

[0050] Step S12: Screening the first mixed slurry according to particle size to obtain coarse ash particles and fine ash particles. Optionally, a coarse-cutting screen can be used to screen the first mixed slurry according to particle size to obtain coarse ash particles and fine ash particles. In this embodiment, the coarse-cutting screen has an aperture of 0.5 mm to 1 mm.

[0051] See also Figure 3 As shown, in some optional embodiments, the above step S2, wherein the fine-grained ash is mixed with a slurry and then re-selected to obtain a first underflow and a first overflow, may include steps S21-S22:

[0052] In step S21, the fine ash is mixed with liquid to form a second mixed slurry with a concentration of 10% to 30%. Optionally, the coarse ash on the sieve is discharged, and the fine ash under the sieve is collected in a slurry mixing tank, and the supernatant of the gasified ash water is used to mix the slurry to form a second mixed slurry with a concentration of 10% to 30%.

[0053] In step S22, the second mixed slurry is subjected to gravity separation to obtain a first underflow and a first overflow. Alternatively, the second mixed slurry can be fed into a classifying cyclone for gravity separation to obtain a first underflow and a first overflow.

[0054] See also Figure 4 As shown, in some optional embodiments, the above step S3, processing the first underflow to obtain carbon fines, decarbonized tailings and ash to be processed, may include steps S31-S32:

[0055] Step S31, re-select the first underflow to obtain a second underflow and a second overflow. It can be understood that the second underflow has a high ash content, a low carbon content, a high density, and a large weight. The second overflow has a high carbon content, a low ash content, a low density, and a small weight. Optionally, the first underflow can be fed into a fluidized bed separator for re-selection. The fluidized bed separator is also a re-selection device, and its working principle is similar to that of a grading cyclone. The fluidized bed separator can also be replaced by a shaking table re-selection machine, a spiral chute re-selection machine, and other re-selection equipment.

[0056] In step S32, the second overflow is processed to obtain carbon powder and first ash. Optionally, the second overflow can be first screened according to particle size using a curved grading screen to obtain coarse first ash and fine third ash. The third ash is then centrifuged using a centrifuge to dehydrate and deslim, resulting in a carbon powder product.

[0057] The second underflow is processed to produce decarbonized tailings and a second ash. Optionally, the second underflow can be screened based on particle size using a curved grading screen to produce coarse-grained second ash and fine-grained fourth ash. The fourth ash is then dehydrated using a vibrating screen to produce a decarbonized tailings product. This achieves efficient carbon-ash separation.

[0058] The first ash and the second ash are used as the ash to be processed. Optionally, the first ash and the second ash can be fed into a slurry mixing barrel, and the supernatant of the gasified ash water is used for slurry mixing to form a mixed slurry for standby use.

[0059] See also Figure 5 As shown, in some optional embodiments, the above step S4, wherein the ash to be treated and the first overflow are mixed and then re-selected to obtain flotation ash that meets the flotation conditions and ash to be floated that does not meet the flotation conditions, may include steps S41-S42:

[0060] Step S41: Grind the first overflow to further reduce the particle size of the first overflow. Optionally, the first overflow can be ground using a grinding mill. The grinding mill can be a wet ball mill, a rod mill, or the like.

[0061] In step S42, the ash to be processed and the first overflow after grinding are mixed and then subjected to gravity separation to obtain the flotation ash and the ash to be flotated. Optionally, the slurry after the first overflow grinding and the ash to be processed can be fed together into a mixing tank, mixed with the supernatant of the gasified ash water to form a mixed slurry, and the mixed slurry is fed into a classifying cyclone for gravity separation.

[0062] See also Figure 6 As shown, in some optional embodiments, the above step S5, flotation ash that meets the flotation conditions, and processing to obtain carbon concentrate and decarbonized tailings, may include steps S51-S53:

[0063] In step S51, flotation ash meeting flotation conditions is subjected to bubble flotation to obtain carbonaceous material and tailings. Alternatively, a flotation system can be used to subject flotation ash meeting flotation conditions to bubble flotation. As will be appreciated, during flotation, a surfactant (foaming agent) capable of generating a large number of bubbles is employed. When air is introduced into the water or air is introduced into the water due to agitation, the hydrophobic end of the surfactant is oriented toward the air side of the bubbles at the air-liquid interface, while the hydrophilic end remains in the solution, forming bubbles. Another surfactant (collecting agent) acts as a collector and adsorbs onto the surface of solid mineral powder. This adsorption is selective depending on the properties of the mineral. The basic principle is to exploit lattice defects on the crystal surface. The outward-facing hydrophobic end partially penetrates into the bubbles, allowing the bubbles to carry away the desired mineral powder (i.e., carbonaceous material) during the flotation process, achieving the desired mineral separation goal. In this embodiment, the flotation system can be a flotation cell or a flotation column. The foaming agent includes one of 2-octanol and methyl isobutyl carbinol (MIBC), and the dosage is 1-15 kg. The collector includes one of diesel, kerosene, waste diesel, and waste engine oil, and the dosage is 1.5-18 kg.

[0064] In step S52, the carbonaceous material is collected and filtered to obtain carbon powder. Alternatively, a scraper can be used to collect the carbonaceous material and the carbonaceous material can be sent to a filter press for dehydration and recovery to obtain carbon powder.

[0065] In step S53, the tailings are concentrated and filtered to obtain decarbonized tailings. Alternatively, the tailings can be collected in buckets, and the collected slurry can flow to a concentration tank for concentration. The concentrated tailings are then recovered using a filter press to obtain decarbonized tailings. The overflow from the concentration tank and the filtrate from the filter press can be purified in a sedimentation tank and then returned to the circulating water tank for recycling, eliminating wastewater discharge throughout the entire production cycle.

[0066] It is understandable that after the previous screening and re-selection steps, the vast majority of the coal gasification slag can be processed to obtain carbon fines and decarbonized tailings. The remaining first ash, second ash, and first overflow may contain ash that can be screened and re-selected to obtain carbon fines and decarbonized tailings. To separate this ash, in some optional embodiments, the coal gasification slag resource recovery method of the present application may also include a recycling process to separate this ash, thereby reducing the proportion of ash that is finally subjected to flotation, which can further reduce costs.

[0067] The cyclic treatment process includes repeatedly grinding and re-selecting the ash to be floated that does not meet the flotation conditions, flotating the flotation ash that meets the flotation conditions after each grinding and re-selection, and processing it to obtain carbon concentrate and decarbonization tailings. It is understood that grinding the ash to be floated can further reduce the particle size of the ash to be floated. Re-selecting the ground ash to be floated can separate the flotation ash that meets the flotation conditions, and then flotating this flotation ash to obtain carbon concentrate and decarbonization tailings. Repeating this cyclic treatment process can achieve more refined and efficient separation of carbon concentrate and decarbonization tailings.

[0068] See also Figure 7 As shown, the embodiment of the coal gasification slag resource recovery method provided in the embodiment of the present application is as follows:

[0069] Laboratory simulation: The coal gasification slag is fed into the slurry mixing barrel, and the supernatant of the gasification ash water is used to prepare the slurry to form a first mixed slurry with a concentration of 50%. The first mixed slurry is fed into a coarse cut screen for screening. The grading aperture of the coarse cut screen is 0.5mm, and the sample is divided into coarse ash with low carbon content (greater than 0.5mm) and fine ash with high carbon content (less than 0.5mm).

[0070] The coarse particles on the screen are discharged, and the fine particles under the screen are collected into the slurry mixing barrel and further liquid is added to form a second mixed slurry with a concentration of about 20%. The second mixed slurry is fed into the grading cyclone for further classification. The grading aperture is 0.15 mm, and it is divided into the first underflow (0.15 mm-0.5 mm) and the first overflow (less than 0.15 mm).

[0071] The first underflow is fed into a fluidized bed separator for gravity separation, producing a second underflow and a second overflow. The second overflow is screened using a curved grading screen to produce a coarse first ash and a fine third ash. The third ash is then centrifuged and dehydrated to produce a carbon concentrate product. The second underflow is screened using a curved grading screen to produce a coarse second ash and a fine fourth ash. The fourth ash is dehydrated using a vibrating screen to produce a decarbonized tailings product.

[0072] The first overflow is ground in a grinding mill. The ash to be processed and the ground first overflow are mixed and fed into a classifying cyclone for gravity separation to obtain flotation ash and ash to be floated. The ash to be floated is repeatedly ground and gravity separated. The flotation ash obtained after each grinding and gravity separation is fed into a flotation system for bubble flotation to obtain carbonaceous matter and tailings.

[0073] A scraper collects carbonaceous material and feeds it to a filter press for dehydration and recovery, producing carbon concentrate. A bucket collects tailings, which then flow to a thickening tank for concentration. The concentrated tailings are then recovered using a filter press to produce decarbonized tailings. The overflow from the thickening tank and the filter press filtrate can be returned to the circulating water tank for reuse.

[0074] Example 1: 2-octanol was used as the foaming agent and diesel was used as the collector. At a foaming agent dosage of 4 kg / t (2-octanol) and a collector dosage of 8 kg / t (diesel), the yield of carbon concentrate was approximately 45%, with an ash content of approximately 28%. The yield of decarbonized tailings was approximately 49%, with an ash content of approximately 95%.

[0075] Example 2: Methyl isobutyl carbinol (MIBC) was used as the foaming agent, and diesel was used as the collector. At a foaming agent (MIBC) dosage of 4 kg / t and a collector (diesel) dosage of 8 kg / t, the yield of carbon concentrate was approximately 47%, with an ash content of approximately 29%. The yield of carbon extraction tailings was approximately 45%, with an ash content of approximately 97%.

[0076] Example 3: 2-octanol was used as the foaming agent and kerosene as the collector. At a foaming agent dosage of 4 kg / t (2-octanol) and a collector dosage of 8 kg / t (kerosene), the yield of carbon concentrate was ~53% and the ash content was ~35%. The yield of carbon extraction tailings was ~40% and the ash content was ~93%.

[0077] The coal gasification slag resource recovery method of the present application can achieve the following beneficial effects:

[0078] (1) A combined process for extracting carbon concentrate from coal gasification slag by screening and grading, gravity separation, and bubble flotation was designed. Process parameters such as reagent dosage can be dynamically adjusted based on the product quality requirements of carbon concentrate and carbon extraction tailings, thereby achieving both product quality requirements and economic benefits.

[0079] (2) The coal gasification slag can be almost fully utilized as a resource. The recovered carbon concentrate can be recycled for gasification, incinerated in boilers, or used to prepare carbon-based adsorption materials. The loss on ignition of the carbon-extracted tailings can be controlled within 5%, and the tailings are rich in inorganic components such as SiO2 and Al2O3, meeting the first-level fly ash standards in the "Management Measures for the Comprehensive Utilization of Fly Ash" and can be used to produce cementitious materials, building materials, etc.

[0080] (3) The production process achieves near-zero wastewater discharge. The water used in the process can be made from the supernatant of gasification ash water, without the need to add additional fresh water. The water used in the gasification slag sorting stage can be recycled after purification in the sedimentation tank, and there is no wastewater discharge during the entire production cycle.

[0081] It should be understood that the present application is not limited to the exact structure described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A method for recycling coal gasification slag, characterized in that: include: The coal gasification slag is screened according to the particle size to obtain coarse ash particles and fine ash particles; The fine-grained ash is mixed with a slurry and then re-selected to obtain a first underflow and a first overflow; Processing the first underflow to obtain carbon fines, decarbonized tailings, and ash to be processed; reselecting the first underflow to obtain a second underflow and a second overflow; Screening the second overflow according to particle size to obtain coarse-particle first ash and fine-particle third ash; Centrifugally separating the third ash to obtain carbon powder; Screening the second underflow according to particle size to obtain coarse-grained second ash and fine-grained fourth ash; Dehydrating the fourth ash to obtain decarbonized tailings; using the first ash and the second ash as the ash to be processed; grinding the first overflow; Gravity separation is performed on the ash to be processed and the first overflow after grinding to obtain flotation ash that meets flotation conditions and ash to be floated that does not meet flotation conditions; The flotation ash that meets the flotation conditions is floated and processed to obtain carbon concentrate and decarbonized tailings.

2. The method for recycling coal gasification slag according to claim 1, characterized in that: It also includes a recycling process, which includes: The ash to be floated that does not meet the flotation conditions is repeatedly ground and re-selected, and the flotation ash that meets the flotation conditions obtained after each grinding and re-selection is floated and processed to obtain carbon concentrate and decarbonized tailings.

3. The method for recycling coal gasification slag according to claim 1 or 2, characterized in that: The flotation ash that meets the flotation conditions is floated and processed to obtain carbon concentrate and decarbonized tailings, including: The flotation ash that meets the flotation conditions is subjected to bubble flotation to obtain carbonaceous matter and tailings; collecting and filtering the carbon-containing material to obtain carbon powder; The tailings are concentrated and filter-pressed to obtain decarbonized tailings.

4. The method for recycling coal gasification slag according to claim 1, characterized in that: The coal gasification slag is screened according to particle size to obtain coarse ash particles and fine ash particles, including: Adding liquid to the coal gasification slag to form a first mixed slurry with a concentration of 35% to 65%; The first mixed slurry is sieved according to particle size to obtain coarse ash particles and fine ash particles.

5. The method for recycling coal gasification slag according to claim 1, characterized in that: The step of preparing the fine-grained ash into a slurry and then performing gravity separation to obtain a first underflow and a first overflow comprises: Adding liquid to the fine-grained ash to form a second mixed slurry with a concentration of 10% to 30%; The second mixed slurry is subjected to gravity selection to obtain a first underflow and a first overflow.

6. The method for recycling coal gasification slag according to claim 1, wherein: The grading aperture range for screening coal gasification slag is 0.5mm~1mm; and / or The classification aperture range for reselecting the fine ash particles is 0.074 mm to 0.15 mm; and / or The frother used for flotation includes one of octanol and methyl isobutyl carbinol, with a dosage of 1-15 kg; and / or The collector used for flotation includes one of diesel, kerosene, waste diesel, and waste engine oil, with a dosage of 1.5~18kg.

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