A method for deep deashing and upgrading of coking coal slime

Abstract

This invention discloses a method for deep deashing and upgrading of coking coal slime, comprising the following steps: 1) treating the coking coal slime with agglomerated oil to obtain a slurry; 2) adjusting the pH value of the slurry obtained in step 1), then adding a flocculant and stirring for selective flocculation to obtain a liquid slurry; 3) subjecting the liquid slurry obtained in step 2) to gravity separation. This invention first treats the coking coal slime with oil agglomeration, wetting the hydrophobic surface of the slime. Through collisions between coal particles, low-density coal particle agglomerates are formed, facilitating subsequent gravity separation and selective separation of ash and coal. Then, by adjusting the pH value of the slurry, the surfaces of coal particles and ash minerals carry different charges. Selective flocculation is then performed by adding a flocculant, causing the ash minerals to form high-density, large-particle-size agglomerates, which improves the deashing selectivity of gravity separation and achieves high recovery rates for clean coal with low ash content.

Description

Technical Field

[0001] This invention belongs to the field of coal reprocessing technology, specifically relating to a method for deep deashing and upgrading of coking coal slime. Background Technology

[0002] my country's coal resources can be divided into thermal coal and coking coal according to their uses, accounting for 72% and 26% of my country's coal resources respectively (the classification of the remaining 2% is unclear). Compared with my country's abundant coal resources, coking coal resources are relatively scarce.

[0003] Coal slime is a byproduct of the coal washing process. It is a viscous substance composed of fine coal particles, pulverized aggregates, and water. Coal slime has a high content of fine particles, with particles smaller than -200 mesh (0.074 mm) generally accounting for more than 70%. The ash mineral composition of coal slime is mostly similar, mainly SiO2, followed by Al2O3. These substances form strongly negatively charged colloidal particles on the surface of the coal slime. The repulsive force between like charges keeps these particles dispersed in water. In water, it is affected not only by gravity but also by Brownian motion, thus coal slime water often has colloidal properties. Because the colloidal particles are charged, they attract polar water molecules to form a "hydration film." This "hydration film" prevents the colloidal particles from contacting each other, making the coal slime water a stable colloidal dispersion system that is difficult to settle naturally. Coal slime has a high water content and strong water retention capacity; after filtration and dewatering, the water content of coal slime is generally above 20%. After vacuum filtration, the water content of coal slime is generally above 30%; after belt filtration, it is generally 26%–40%; and after filter press filtration, it is generally 20%–35%. Coal slime not only has a high water content but also strong water retention, making it difficult to dry. During natural stockpiling, a large amount of water in the inner layers is difficult to evaporate, making subsequent processing challenging. Coal slime has a high ash content and low calorific value. Low-ash coal slime generally has an ash content of 20%–32% and a calorific value of 12.5 MJ / kg–20 MJ / kg; medium-ash coal slime has an ash content of 30%–55% and a calorific value of 8.4 MJ / kg–12.5 MJ / kg; and high-ash coal slime has an ash content >55% and a calorific value of 3.5 MJ / kg–8.4 MJ / kg. Coal slime generally contains a large amount of clay minerals, and coupled with its high moisture content and fine particle size, most coal slime is highly viscous. It can be seen that coal slime has a relatively high ash, sulfur, and water content, and a low calorific value, making it difficult to use directly. Open-air storage of coal slime not only occupies a large area, but also causes it to be easily blown away by the wind and flow everywhere when exposed to water, easily leading to secondary pollution and having a significant impact on the environment, ecological landscape, and the safety of life and property of residents downstream of the tailings dam.

[0004] Coking coal is primarily used in coking production. It typically possesses a certain degree of caking and coking properties, and can coke under coke oven conditions, serving as the raw material for producing coke with specific quality requirements. The produced coke can be categorized by its use: metallurgical coke (including blast furnace coke, foundry coke, and ferroalloy coke), gasification coke, and coke for calcium carbide. Coking coal production is directly related to industries such as metallurgy and coal chemicals, significantly impacting the long-term development of the national industrial system and people's living standards. Furthermore, coal is a non-renewable resource; from the perspective of national and social stability, harmony, and sustainable development, it is essential to study its rational development and utilization scale and protect this limited resource. Therefore, processing the byproduct of coking coal washing—coal slime—into coking raw materials through deashing and upgrading not only yields significant economic benefits but also substantial resource benefits. Currently, coking coal slime is mainly recovered through flotation. However, current flotation technology primarily focuses on partial separation and recovery of coal slime, and its reagent system and process structure cannot meet the deeper requirements for desulfurization, deashing, and upgrading. Coal slime flotation is a complex physical and chemical process, and its effectiveness is closely related to the properties of the coal slime, the reagent formulation, the flotation process, and the flotation equipment. Currently, flotation technology in the coal industry is mainly used for partial separation and recovery of coal slime, and its process structure and reagent formulation cannot meet the deeper needs of desulfurization, deashing, and quality improvement. Summary of the Invention

[0005] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, the main objective of this invention is to provide a method for deep deashing and upgrading of coking coal slime, addressing the shortcomings of existing deashing and upgrading methods, which suffer from poor deashing rates and low recovery rates, making them unsuitable for the needs of sophisticated equipment such as aerospace furnaces.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A method for deep deashing and upgrading of coking coal slime, characterized by comprising the following steps:

[0008] 1) Oil agglomeration treatment of coking coal slime was carried out using agglomerated oil to obtain slurry;

[0009] 2) Adjust the pH value of the slurry obtained in step 1), then add flocculant and stir to carry out selective flocculation to obtain slurry;

[0010] 3) Perform re-selection treatment on the ore solution obtained in step 2).

[0011] In some specific embodiments, the agglomerated oil in step 1) includes wash oil, non-polar hydrocarbon oil and modifier; wherein the mass ratio of the wash oil, non-polar hydrocarbon oil and modifier is 100:20-60:10-40.

[0012] The preferred ratio is 100:30–55:20–35;

[0013] A further preferred ratio is 100:40-50:20-30.

[0014] In some specific embodiments, the non-polar hydrocarbon oil is one or more of shale oil, diesel oil, and kerosene; the modifier is one or more of ethyl acetate, methyl acetate, and methyl formate.

[0015] In some specific embodiments, the amount of agglomerated oil used in step 1) is 1000g / t to 10000g / t;

[0016] Preferably, the concentration is 3000g / t to 7000g / t;

[0017] More preferably, the concentration is 4000g / t to 5000g / t.

[0018] In some specific embodiments, the oil agglomeration treatment in step 1) specifically involves: weighing coking coal slime, adding water and stirring to prepare a slurry, then adding agglomerating oil, transferring it to a ball mill for grinding, and then transferring it to a mixing tank for stirring and agglomeration to obtain a slurry.

[0019] Furthermore, the mass concentration of coking coal slime in the slurry is 80 g / L to 350 g / L, preferably 150 g / L to 250 g / L.

[0020] In some specific embodiments, the grinding time is 1 min to 20 min, preferably 5 min to 15 min; more preferably 8 min to 10 min;

[0021] The stirring process parameters are as follows: stirring time 5 min to 15 min, more preferably 8 min to 10 min; stirring speed 1000 r / min to 2000 r / min, more preferably 1400 r / min to 1500 r / min.

[0022] In some specific embodiments, the pH value in step 2) is 2-5; and the flocculant is one or more of the organic polymeric flocculants cationic polyacrylamide, nonionic polyacrylamide, and anionic polyacrylamide; and the molecular weight of the organic polymeric flocculant is 0.8 × 10⁻⁶. 7 ~2×10 7 The preferred value is 1.2 × 10⁻⁶. 7 ~1.5×10 7 .

[0023] In some specific embodiments, the amount of flocculant used is 500g / t to 1000g / t;

[0024] Preferably, the concentration is 700g / t to 800g / t.

[0025] In some specific implementations, selective flocculation in step 2) specifically involves: adding a buffer solution to the slurry after oil agglomeration, adjusting the pH to 2-5 so that the surface of the coal particles is mainly positively charged and the surface of the ash minerals is mainly negatively charged; then adding a flocculant and stirring to fully flocculate to obtain a slurry.

[0026] Furthermore, the buffer solution is a dilute sulfuric acid solution with a mass concentration of 5-15%;

[0027] Furthermore, the stirring process parameters are: stirring time of 20-50 min, more preferably 30-40 min.

[0028] In some specific embodiments, the process parameters for the reselection process in step 3) are: water flow rate of 5L / min to 15L / min, preferably 8L / min to 10L / min.

[0029] Compared with the prior art, the present invention has at least the following advantages:

[0030] The method for deep deashing and upgrading of coking coal slime provided by this invention first involves treating the coking coal slime with oil agglomeration, which wets the hydrophobic surface of the slime. Through the collision between coal particles, low-density coal particle agglomerates are formed, which is beneficial for subsequent gravity separation and selective separation of ash and coal. Then, by adjusting the pH value of the slurry, the surfaces of coal particles and ash minerals are made to carry different charges. Then, by adding a flocculant, selective flocculation is carried out, which makes the ash minerals form high-density, large-particle-size agglomerates, which is beneficial for improving the deashing selectivity of gravity separation and obtaining clean coal with low ash content with high recovery rate. Attached Figure Description

[0031] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below.

[0032] Figure 1 The process flow diagram for deep deashing and upgrading of coking coal slime provided by the present invention is shown. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The following embodiments are merely descriptive and not limiting, and should not be construed as limiting the scope of protection of the present invention.

[0034] When a quantity, concentration, or other value or parameter is described as a range, preferred range, or preferred upper and lower limits, it should be understood that it is equivalent to specifically disclosing any range by combining any pair of upper or preferred values ​​with any lower or preferred values, regardless of whether the range is specifically disclosed. Unless otherwise stated, the numerical range values ​​listed herein include the endpoints of the range and all integers and fractions within that range.

[0035] Unless otherwise stated, all percentages, parts, ratios, etc. in this document are by weight.

[0036] The materials, methods, and embodiments described herein are exemplary and should not be construed as limiting unless otherwise stated.

[0037] Example 1:

[0038] The present invention provides a method for deep deashing and upgrading of coking coal slime, which includes the following steps:

[0039] 1. Oil agglomeration in coking coal slime

[0040] Weigh out coking coal slime, add water and stir to make slurry, control the slurry concentration to 200 g / L, then add agglomerating oil, and then pour into a ball mill for grinding for 9 min. Pour the ground slurry into a mixing tank, control the stirring speed to 1500 r / min, and stir for 10 min to obtain slurry; wherein the agglomerating oil is a mixture of wash oil, diesel oil and ethyl acetate in a weight ratio of 100:45:25, and the amount of agglomerating oil used is 4500 g / t.

[0041] 2. Selective flocculation

[0042] Subsequently, a 10% dilute sulfuric acid solution was added to the slurry after oil agglomeration treatment to adjust the pH to 3, so that the coal particle surface is mainly positively charged and the ash mineral surface is mainly negatively charged. The pH-adjusted slurry was poured into a mixing tank and a flocculant was added and stirred for 30 minutes to obtain the modified slurry. The flocculant was anionic polyacrylamide with a molecular weight of 1.3 × 10⁻⁶. 7 The dosage is 750g / t.

[0043] 3. Reselection Separation

[0044] The mineral solution, after oil agglomeration and selective flocculation, was subjected to gravity separation using a spiral chute; the water flow rate was 9 L / min (process flow is as follows). Figure 1 As shown in the figure, low-ash clean coal, medium coal and tailings coal were obtained by gravity separation.

[0045] The three products obtained from the reselection were subjected to ash content testing. The ash content was determined using the slow ashing method. According to the national standard GB / T212-2009 "Industrial Analysis Methods for Coal", a certain mass of completely dried coal slime was weighed, placed in a muffle furnace, and heated to 810±10℃ at a specific heating rate. The temperature was maintained stable until the mass became constant. The ash content of the sample was calculated as the percentage of the residue's mass relative to the original mass. The specific steps and related formulas are as follows:

[0046] (1) Dry the sample. Place the filtered coal slime gravity separation product into an oven at 100°C for drying. The standard for drying the sample is: take the filter paper containing the sample out of the oven and place it on the test bench for 3 to 4 seconds. Then pick up the filter paper. If there is no watermark on the test bench, the sample is considered to be dried.

[0047] (2) Sample preparation: Place the sample on an iron plate, grind the sample with a pressure roller and putty knife, and put it into a packaging bag with the corresponding label.

[0048] (3) Weighing: In a ash dish with constant mass (mass recorded as m1), weigh 1 ± 0.1 g of test sample with a particle size not greater than 0.2 mm, weigh to four decimal places (mass recorded as m2), spread evenly in the ash dish, with a mass not greater than 0.15 g per square centimeter.

[0049] (4) Place the ash pan into the muffle furnace in the weighing order, close the furnace door and leave a gap of about 20 mm, raise the furnace temperature to 500℃ in about 30 minutes and keep it at this temperature for 30 minutes; continue to raise the temperature to 815±10℃ and keep it at this temperature for 1 hour.

[0050] (5) Weigh, turn off the muffle furnace, take out the ash dish from the furnace chamber, cool it in the air for 5 minutes, then transfer it to the desiccator to cool to room temperature and weigh it (the mass is recorded as m3).

[0051] After the test steps are completed, the ash content of the three products is calculated according to the following formula.

[0052]

[0053] The three products prepared under the above experimental conditions yielded the following experimental results based on the ash content measurement method:

[0054]

[0055] Example 2:

[0056] Compared with Example 1, the only difference is the grinding time: Group (I): 4 min; Group (II): 15 min. The experimental results are as follows:

[0057]

[0058] Example 3:

[0059] Compared to Example 1, the only difference is that the mass of each substance in the agglomerated oil is: Group (I): Wash oil: Diesel oil: Ethyl acetate = 100:20:10; Group (II): Wash oil: Diesel oil: Ethyl acetate = 100:30:15. The test results are as follows:

[0060]

[0061] Example 4:

[0062] Compared to Example 1, the only difference is the amount of agglomerated oil used: Group (I): 3000 g / t; Group (II): 3500 g / t. The test results are as follows:

[0063]

[0064] Example 5:

[0065] Compared to Example 1, the only difference was the stirring speed of the mixer during oil agglomeration: Group (I): 1000 r / min; Group (II): 2000 r / min. The experimental results were:

[0066]

[0067] Example 6:

[0068] Compared to Example 1, the only difference was the stirring time of the mixer during oil agglomeration: Group (I): 5 min; Group (II): 15 min. The experimental results were:

[0069]

[0070] Example 7:

[0071] Compared to Example 1, the only difference lies in the type of flocculant added: Group (I): nonionic polyacrylamide; Group (II): cationic polyacrylamide; the test results are as follows:

[0072]

[0073] Example 8:

[0074] Compared with Example 1, the only difference is the molecular weight of the anionic polyacrylamide, which are: Group (I): 0.8 × 10 7 Group (II): 2×10 7 The experimental results are as follows:

[0075]

[0076] Example 9:

[0077] Compared to Example 1, the only difference is the dosage of anionic polyacrylamide: Group (I): 500 g / t; Group (II): 1000 g / t. The experimental results are as follows:

[0078]

[0079] Example 10:

[0080] Compared to Example 1, the only difference was the water flow rate during reselection: Group (I): 5 L / min; Group (II): 15 L / min. The experimental results were:

[0081]

[0082] Example 11:

[0083] Compared with Example 1, the only difference is that the mass concentration of coking coal slime in the slurry in step 1) is 100 g / L. The test results are as follows:

[0084]

[0085] Example 12:

[0086] Compared with Example 1, the only difference is that the stirring time after adding the flocculant is 20 minutes. The test results are as follows:

[0087]

[0088] Example 13:

[0089] Compared with Example 1, the only difference is that the coking coal slime is not subjected to oil agglomeration and selective flocculation; instead, gravity separation is performed directly after slurry preparation. The test results are as follows:

[0090]

[0091] Example 14:

[0092] Compared with Example 1, the only difference is that selective flocculation of coking coal slime is not performed; instead, gravity separation is performed directly after oil agglomeration. The experimental results are as follows:

[0093]

[0094] Example 15:

[0095] Compared with Example 1, the only difference is that the coking coal slime is not subjected to oil agglomeration; instead, it is directly subjected to gravity separation after selective flocculation. The test results are as follows:

[0096]

[0097] Experimental results show that compared with conventional sorting methods, the clean coal obtained by this method has lower ash content, higher yield, and improved separation effect of coking coal slime.

[0098] In summary, as shown in Examples 1-12, oil agglomeration and selective flocculation can improve the selective separation of coal and ash minerals in the gravity separation process of coking coal slime, which is beneficial for obtaining low-ash, high-quality clean coal. The selective separation effect is closely related to factors such as the composition and dosage of the agglomerated oil, grinding time, agglomeration stirring speed and time, type and dosage of flocculant, gravity separation concentration, and water flow rate. As shown in Examples 13-15, both oil agglomeration and selective flocculation operations have a certain impact on improving the gravity separation process of coking coal slime. Through the synergistic effect of oil agglomeration and selective flocculation, the yield of clean coal and the ash content of clean coal can be increased and reduced in the subsequent gravity separation process of coking coal slime.

[0099] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for deep deashing and upgrading of coking coal slime, characterized in that, Includes the following steps: 1) Oil agglomeration treatment of coking coal slime was carried out using agglomerated oil to obtain slurry; 2) Adjust the pH value of the slurry obtained in step 1), then add flocculant and stir to carry out selective flocculation to obtain slurry; 3) Perform gravity separation on the ore solution obtained in step 2); The agglomerated oil in step 1) includes wash oil, non-polar hydrocarbon oil and modifier; wherein the mass ratio of wash oil, non-polar hydrocarbon oil and modifier is 100:20-60:10-40; The non-polar hydrocarbon oil is one or more of shale oil, diesel oil, and kerosene; the modifier is one or more of ethyl acetate, methyl acetate, and methyl formate. The pH value mentioned in step 2) is 2-5; and the flocculant is one or more of the organic polymeric flocculants cationic polyacrylamide, nonionic polyacrylamide, and anionic polyacrylamide; and the molecular weight of the organic polymeric flocculant is 0.8 × 10⁻⁶. 7 ~2×10 7 .

2. The method for deep deashing and upgrading of coking coal slime according to claim 1, characterized in that, The mass ratio of wash oil, non-polar hydrocarbon oil and modifier in step 1) is 100:30-55:20-35.

3. The method for deep deashing and upgrading of coking coal slime according to claim 2, characterized in that, The mass ratio of wash oil, non-polar hydrocarbon oil and modifier in step 1) is 100:40-50:20-30.

4. The method for deep deashing and upgrading of coking coal slime according to claim 1, characterized in that, The amount of agglomerated oil used in step 1) is 1000g / t to 10000g / t.

5. The method for deep deashing and upgrading of coking coal slime according to claim 4, characterized in that, The amount of agglomerated oil used in step 1) is 3000g / t to 7000g / t.

6. The method for deep deashing and upgrading of coking coal slime according to claim 5, characterized in that, The amount of agglomerated oil used in step 1) is 4000g / t to 5000g / t.

7. The method for deep deashing and upgrading of coking coal slime according to claim 1, characterized in that, The oil agglomeration treatment described in step 1) is as follows: Weigh coking coal slime, add water and stir to prepare slurry, then add agglomerating oil, grind, and then stir and agglomerate to obtain slurry.

8. The method for deep deashing and upgrading of coking coal slime according to claim 7, characterized in that, The grinding time is 1 min to 20 min; the stirring process parameters are: stirring time 5 min to 15 min, stirring speed 1000 r / min to 2000 r / min.

9. The method for deep deashing and upgrading of coking coal slime according to claim 8, characterized in that, The amount of flocculant used is 500g / t to 1000g / t.

10. The method for deep deashing and upgrading of coking coal slime according to claim 9, characterized in that, In step 2), selective flocculation specifically involves adding a buffer solution to the slurry after oil agglomeration, adjusting the pH to 2-5, then adding a flocculant, stirring to achieve full flocculation, and obtaining a slurry.

11. The method for deep deashing and upgrading of coking coal slime according to claim 10, characterized in that, The process parameters for the reselection process in step 3) are: water flow rate of 5L / min to 15L / min.

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