Environment-friendly efficient coal slime flotation collecting agent and coal slime flotation method

Abstract

The invention belongs to the technical field of coal slime flotation, and particularly relates to an environment-friendly efficient coal slime flotation collecting agent and a coal slime flotation method.The collecting agent comprises 65%-80% of biodiesel and 20%-35% of polyoxyethylene ether surfactants; the coal slime flotation method comprises the following steps that a collecting agent is emulsified into a microemulsion type collecting agent, coal slime is added into a size mixing tank, water is added to prepare flotation ore pulp, half of the microemulsion type collecting agent is added, stirring and mixing are conducted, ore pulp containing the collecting agent is obtained, the ore pulp containing the collecting agent is added into a flotation machine, then the remaining microemulsion type collecting agent is added, and flotation is conducted. Adding a foaming agent after stirring, filling air for flotation, and scraping foams after foams are formed, so as to obtain clean coal and tailings. The raw materials used by the collecting agent are all renewable resources, the environment-friendly safety is high, the collecting agent is emulsified into a micro-emulsion type collecting agent during flotation, the utilization rate of the collecting agent can be increased, the selectivity of the collecting agent can be improved through segmented dosing, and therefore the collecting agent has efficient collecting performance, excellent selectivity and good environmental compatibility.

Description

Technical Field

[0001] This invention belongs to the field of coal slime flotation technology, specifically relating to an environmentally friendly and efficient coal slime flotation collector and a coal slime flotation method. Background Technology

[0002] Coal slime flotation is a coal slime separation technology that utilizes the differences in the physicochemical properties of the surfaces of coal and gangue, and can expand the difference in surface wettability between coal and gangue by adding specific flotation collectors, thereby achieving the separation of coal and gangue.

[0003] Traditional flotation collectors are fossil fuel collectors (such as diesel and kerosene), which are non-renewable resources. Due to the limited mining volume, the price of raw materials has continued to rise, increasing production costs. They are not only difficult to degrade, but also pose a risk of wastewater and exhaust gas pollution, resulting in great environmental pressure and large usage. Furthermore, it is difficult to balance the recovery rate of clean coal and ash content.

[0004] Currently used flotation collectors generally use hydrocarbon oils and promoters as raw materials, utilizing promoters to enhance the hydrophobicity of coal particles. However, these hydrocarbon oils are often diesel or kerosene. While they can improve flotation efficiency to some extent, they still pose significant environmental risks. Furthermore, current coal slime flotation methods involve directly adding the collector into the flotation machine all at once, which fails to fully utilize the collector's selectivity, resulting in poor flotation efficiency and effect, insufficient recovery of combustible matter in the clean coal, and inadequate ash content. Therefore, this invention provides an environmentally friendly and efficient coal slime flotation collector and a coal slime flotation method to solve the aforementioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an environmentally friendly and efficient coal slime flotation collector and a coal slime flotation method.

[0006] The objective of this invention is achieved as follows: an environmentally friendly and efficient coal slime flotation collector, comprising the following raw materials in weight percentages: 65-80% biodiesel and 20-35% polyoxyethylene ether surfactants.

[0007] Preferably, the biodiesel is prepared from vegetable oil or animal fat through a transesterification process.

[0008] Preferably, the preparation method of the biodiesel is as follows: vegetable oil or animal fat is added to a reactor, then anhydrous methanol is added, the mixture is heated to 50-70°C, sodium hydroxide solid catalyst is added, the mixture is stirred for 60-120 min, and the mixture is allowed to stand and separate into layers. The upper layer consists of biodiesel and methanol. The upper layer is distilled at 60-70°C to obtain biodiesel after methanol is distilled off.

[0009] Preferably, the vegetable oil is soybean oil, rapeseed oil, palm oil, or waste edible oil, the mass ratio of vegetable oil or animal fat to anhydrous methanol is 1:5 to 10, and the mass ratio of sodium hydroxide to vegetable oil or animal fat is 0.008 to 0.015:1.

[0010] Preferably, the polyoxyethylene ether surfactant is a fatty alcohol polyoxyethylene ether or an alkylphenol polyoxyethylene ether; more preferably, the fatty alcohol polyoxyethylene ether is a fatty alcohol polyoxyethylene ether AEO-3 or AEO-5, and the alkylphenol polyoxyethylene ether is a nonylphenol polyoxyethylene ether or an octylphenol polyoxyethylene ether.

[0011] Preferably, the collector is prepared as follows: a polyoxyethylene ether surfactant is added to biodiesel and stirred at 600-1000 rpm for 20-30 min to obtain the collector.

[0012] This invention also discloses a coal slime flotation method, comprising the following steps:

[0013] (1) The above collector is mixed with emulsifier and water, and ultrasonically emulsified to form a microemulsion collector;

[0014] (2) Add coal slime into the slurry preparation tank and add water to prepare a flotation slurry with a concentration of 60-100 g / L;

[0015] (3) Add half of the microemulsion collector from step (1) to the flotation slurry, stir and mix to obtain a slurry containing the collector;

[0016] (4) Add the slurry containing the collector into the flotation machine, then add the remaining microemulsion collector, stir for 2-3 minutes, add the frother, fill with air for flotation, and scrape the foam for 2-4 minutes to obtain clean coal and tailings.

[0017] Preferably, the emulsifier in step (1) is lignin sulfonate, and the mass ratio of the collector to the emulsifier and water is 1:0.2-0.3:4-6.

[0018] Preferably, the stirring speed in step (1) is 200-250 r / min and the stirring time is 20-30 min.

[0019] Preferably, the foaming agent in step (4) is octanol or methyl isobutyl alcohol.

[0020] Preferably, the airflow velocity in step (4) is 0.2 to 0.4 L / min.

[0021] Preferably, the amount of collector used per ton of dry coal slime is 1-3 kg, and the amount of foaming agent used per ton of dry coal slime is 0.1-0.3 g.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. The collector of the present invention uses biodiesel and polyoxyethylene ether surfactants as raw materials. Biodiesel is prepared from vegetable oil or animal fat through transesterification. Both biodiesel and polyoxyethylene ether surfactants are renewable resources. Biodiesel has good hydrophobicity, biodegradability, low toxicity and renewability. It can replace traditional high-pollution and difficult-to-degrade fossil fuel collectors, reduce the risk of wastewater and exhaust gas pollution, and has strong environmental safety.

[0024] 2. This invention provides a composite collector prepared from biodiesel and polyoxyethylene ether surfactants. Biodiesel is the main collector, and polyoxyethylene ether surfactants (fatty alcohol polyoxyethylene ethers or alkylphenol polyoxyethylene ethers) are used as synergists. Biodiesel has high hydrophobicity, while polyoxyethylene ether surfactants can emulsify and disperse, resulting in a synergistic effect. The ester groups of biodiesel and the alkyl chains of polyoxyethylene ether surfactants are adsorbed together on the coal surface, forming a dense composite hydrophobic film with higher adsorption strength. The polyoxyethylene ether surfactants emulsify biodiesel into submicron droplets, significantly increasing its dispersion rate in the slurry, allowing it to quickly reach the coal particle surface and improve the flotation rate. The hydrophilic chains of the polyoxyethylene ether surfactants form a spatial barrier, preventing the collector from adsorbing on the hydrophilic gangue surface, thus avoiding gangue floating and enhancing the selective adsorption of the collector. Therefore, the collector of this invention possesses high efficiency, excellent selectivity, and good environmental compatibility.

[0025] 3. In the flotation of coal slime, the present invention first emulsifies the collector with the emulsifier lignin sulfonate and water to form a microemulsion collector, which is beneficial to improving the utilization rate of the collector. Half of the microemulsion collector is added when adjusting the slurry, and the other half is added during flotation. The staged addition of reagents can avoid waste of collectors and improve the selectivity of the collectors.

[0026] 4. Using the collector of the present invention for flotation of long-flame coal slime, the recovery rate of combustible material in clean coal is as high as 86.01-91.88%, and the ash content of clean coal is 13.57-14.88%. Compared with conventional diesel collectors and conventional flotation methods, even with a reduction in the amount of collector used, the recovery rate of combustible material in clean coal obtained by using the collector and flotation method of the present invention is increased by 18.05-26.10%, and the ash content of clean coal is reduced by 11.16-18.98%. Detailed Implementation

[0027] The present invention will now be described in more detail through specific embodiments.

[0028] Example 1

[0029] A method for preparing an environmentally friendly and efficient coal slime flotation collector is as follows: 35g of fatty alcohol polyoxyethylene ether (AEO-5) is added to 65g of biodiesel and stirred at 600rpm for 30min to obtain the collector.

[0030] Biodiesel is prepared from soybean oil. The preparation process is as follows: Soybean oil is added to a reactor, followed by anhydrous methanol (with a mass ratio of 5:1 to soybean oil). The mixture is heated to 50°C, and sodium hydroxide (with a mass ratio of 0.008:1 to soybean oil) is added as a solid catalyst. The mixture is stirred and reacted for 120 minutes. After standing and separating into layers, the upper layer consists of biodiesel and methanol. The upper layer is distilled at 60°C to obtain biodiesel after methanol is distilled off.

[0031] The method for coal slime flotation using the above-mentioned collector is as follows:

[0032] (1) Mix 100g of the above collector with 20g of emulsifier sodium lignosulfonate and 400ml of water at a stirring speed of 200r / min for 30min, and then ultrasonically emulsify to form a microemulsion collector.

[0033] (2) Add coal slime into the slurry preparation tank and add water to prepare a flotation slurry with a concentration of 60 g / L;

[0034] (3) Add the microemulsion collector (dosage of 0.5 kg / t dry coal slime) to the flotation slurry, stir and mix to obtain a slurry containing the collector;

[0035] (4) Add the slurry containing the collector into the flotation machine, then add the microemulsion collector (0.5 kg / t dry coal slime), stir for 2 min, then add the frother octanol (0.1 g / t dry coal slime), and purge with air for flotation at a flow rate of 0.2 L / min. After foam is formed, scrape the foam for 2 min to obtain clean coal and tailings.

[0036] Example 2

[0037] A method for preparing an environmentally friendly and efficient coal slime flotation collector is as follows: 32g of nonylphenol polyoxyethylene ether is added to 68g of biodiesel and stirred at 700rpm for 28min to obtain the collector.

[0038] Biodiesel is prepared from rapeseed oil. The preparation process is as follows: rapeseed oil is added to a reactor, followed by anhydrous methanol (with a mass ratio of 6:1 to rapeseed oil). The mixture is heated to 55°C, and sodium hydroxide (with a mass ratio of 0.01:1 to rapeseed oil) is added as a solid catalyst. The mixture is stirred and reacted for 100 minutes. After standing and separating into layers, the upper layer consists of biodiesel and methanol. The upper layer is distilled at 62°C to obtain biodiesel after methanol is distilled off.

[0039] The method for coal slime flotation using the above-mentioned collector is as follows:

[0040] (1) Mix 100g of the above collector with 20g of emulsifier sodium lignosulfonate and 450ml of water at a stirring speed of 220r / min for 25min, and then ultrasonically emulsify to form a microemulsion collector.

[0041] (2) Add coal slime into the slurry preparation tank and add water to prepare a flotation slurry with a concentration of 70 g / L;

[0042] (3) Add the microemulsion collector (dosage of 0.5 kg / t dry coal slime) to the flotation slurry, stir and mix to obtain a slurry containing the collector;

[0043] (4) Add the slurry containing the collector into the flotation machine, then add the microemulsion collector (0.5 kg / t dry coal slime), stir for 2 min, then add the frother methyl isobutyl methanol (0.1 g / t dry coal slime), and purge with air for flotation at a flow rate of 0.3 L / min. After foam is formed, scrape the foam for 2 min to obtain clean coal and tailings.

[0044] Example 3

[0045] A method for preparing an environmentally friendly and efficient coal slime flotation collector is as follows: 30g of fatty alcohol polyoxyethylene ether (AEO-5) is added to 70g of biodiesel and stirred at 800rpm for 25min to obtain the collector.

[0046] Biodiesel is prepared from palm oil. The preparation process is as follows: palm oil is added to a reactor, followed by anhydrous methanol (mass ratio of methanol to palm oil is 8:1), heated to 60°C, and sodium hydroxide (mass ratio of sodium hydroxide to palm oil is 0.012:1). The mixture is stirred for 90 minutes, allowed to stand and separate into layers. The upper layer consists of biodiesel and methanol. The upper layer is distilled at 65°C to obtain biodiesel after methanol is distilled off.

[0047] The method for coal slime flotation using the above-mentioned collector is as follows:

[0048] (1) Mix 100g of the above-mentioned collector, 25g of emulsifier sodium lignosulfonate and 500ml of water at a stirring speed of 220r / min for 25min, and then ultrasonically emulsify to form a microemulsion collector.

[0049] (2) Add coal slime into the slurry preparation tank and add water to prepare a flotation slurry with a concentration of 80 g / L;

[0050] (3) Add the microemulsion collector (dosage of 1 kg / t dry coal slime) to the flotation slurry, stir and mix to obtain a slurry containing the collector;

[0051] (4) Add the slurry containing the collector into the flotation machine, then add the microemulsion collector (dosage is 1 kg / t dry coal slime), stir for 3 min, then add the frother methyl isobutyl methanol (dosage is 0.2 g / t dry coal slime), and purge with air for flotation. The airflow velocity is 0.3 L / min. After foam is formed, scrape the foam for 3 min to obtain clean coal and tailings.

[0052] Example 4

[0053] A method for preparing an environmentally friendly and efficient coal slime flotation collector is as follows: 25g of nonylphenol polyoxyethylene ether is added to 75g of biodiesel and stirred at 900rpm for 22min to obtain the collector.

[0054] Biodiesel is prepared from waste cooking oil. The preparation process is as follows: waste cooking oil is added to a reactor, followed by anhydrous methanol (with a mass ratio of 9:1 to waste cooking oil), heated to 65°C, and sodium hydroxide (with a mass ratio of 0.013:1 to waste cooking oil) is added as a solid catalyst. The mixture is stirred and reacted for 70 minutes. After standing and separating into layers, the upper layer consists of biodiesel and methanol. The upper layer is distilled at 68°C to obtain biodiesel after methanol is distilled off.

[0055] The method for coal slime flotation using the above-mentioned collector is as follows:

[0056] (1) Mix 100g of the above-mentioned collector, 25g of emulsifier sodium lignosulfonate and 550ml of water at a stirring speed of 250r / min for 20min, and then ultrasonically emulsify to form a microemulsion collector.

[0057] (2) Add coal slime into the slurry mixing tank and add water to prepare a flotation slurry with a concentration of 90 g / L;

[0058] (3) Add the microemulsion collector (dosage of 1 kg / t dry coal slime) to the flotation slurry, stir and mix to obtain a slurry containing the collector;

[0059] (4) Add the slurry containing the collector into the flotation machine, then add the microemulsion collector (dosage is 1 kg / t dry coal slime), stir for 3 min, then add the frother octanol (dosage is 0.2 g / t dry coal slime), and then fill with air for flotation. The airflow speed is 0.4 L / min. After the foam is formed, scrape the foam for 4 min to obtain clean coal and tailings.

[0060] Example 5

[0061] A method for preparing an environmentally friendly and efficient coal slime flotation collector is as follows: 20g of fatty alcohol polyoxyethylene ether (AEO-5) is added to 80g of biodiesel and stirred at 1000rpm for 20min to obtain the collector.

[0062] Biodiesel is prepared from animal fat. The preparation process is as follows: animal fat is added to a reactor, followed by anhydrous methanol (with a mass ratio of 10:1 to animal fat), heated to 70°C, and sodium hydroxide (with a mass ratio of 0.015:1 to animal fat) is added as a solid catalyst. The mixture is stirred for 60 minutes, allowed to stand and separate into layers. The upper layer consists of biodiesel and methanol. The upper layer is distilled at 70°C to obtain biodiesel after methanol is distilled off.

[0063] The method for coal slime flotation using the above-mentioned collector is as follows:

[0064] (1) Mix 100g of the above-mentioned collector, 30g of the emulsifier sodium lignosulfonate and 600ml of water at a stirring speed of 250r / min for 20min, and then ultrasonically emulsify to form a microemulsion collector.

[0065] (2) Add coal slime into the slurry mixing tank and add water to prepare a flotation slurry with a concentration of 100g / L;

[0066] (3) Add the microemulsion collector (dosage of 1.5 kg / t dry coal slime) to the flotation slurry, stir and mix to obtain a slurry containing the collector;

[0067] (4) Add the slurry containing the collector into the flotation machine, then add the microemulsion collector (dosage is 1.5 kg / t dry coal slime), stir for 3 min, then add the frother methyl isobutyl methanol (dosage is 0.3 g / t dry coal slime), and purge with air for flotation. The airflow velocity is 0.4 L / min. After foam is formed, scrape the foam for 4 min to obtain clean coal and tailings.

[0068] Example 6

[0069] The only difference between Example 6 and Example 3 is that the mass ratio of fatty alcohol polyoxyethylene ether (AEO-5) and biodiesel in the environmentally friendly and efficient coal slime flotation collector of Example 6 is different.

[0070] Specifically, the environmentally friendly and efficient coal slime flotation collector of Example 6 includes the following raw materials by weight: 35g fatty alcohol polyoxyethylene ether (AEO-5) and 65g biodiesel.

[0071] Example 7

[0072] The only difference between Example 7 and Example 3 is that the mass ratio of fatty alcohol polyoxyethylene ether (AEO-5) and biodiesel in the environmentally friendly and efficient coal slime flotation collector of Example 6 is different.

[0073] Specifically, the environmentally friendly and efficient coal slime flotation collector of Example 6 includes the following raw materials by weight: 20g fatty alcohol polyoxyethylene ether (AEO-5) and 80g biodiesel.

[0074] Comparative Example 1

[0075] The only difference between Comparative Example 1 and Example 3 is that the collector in Comparative Example 1 does not contain the raw material fatty alcohol polyoxyethylene ether (AEO-5).

[0076] Comparative Example 2

[0077] The only difference between Comparative Example 2 and Example 4 is that the collector in Comparative Example 2 does not contain the raw material nonylphenol polyoxyethylene ether.

[0078] Comparative Example 3

[0079] The only difference between Comparative Example 3 and Example 3 is that the coal slime flotation method in Comparative Example 3 does not include step (1), that is, the collector is not ultrasonically emulsified to form a microemulsion collector.

[0080] Comparative Example 4

[0081] The only difference between Comparative Example 4 and Example 3 is that the coal slime flotation method in Comparative Example 4 does not include step (3), that is, the environmentally friendly and efficient coal slime flotation collector is not added in batches.

[0082] Comparative Example 5

[0083] The only difference between Comparative Example 5 and Comparative Example 3 is that the collector used in Comparative Example 5 is a conventional commercially available diesel collector, and the amount of collector used is 10 kg / t dry coal slime.

[0084] The effects of the collectors in Examples 1-7 and Comparative Examples 1-5 of this invention were studied as follows:

[0085] The coal samples in Examples 1-7 and Comparative Examples 1-5 were all derived from long-flame coal from the Ordos region. The ash content of the feed coal slime was 35%. The foam (flotation concentrate) scraped out in Examples 1-7 and Comparative Examples 1-5 and the residue at the bottom of the flotation tank (flotation tailings) were filtered, dried, and weighed respectively. The product combustible recovery rate was calculated using the following formula:

[0086]

[0087] Among them, E j r j A j Ay These are, respectively, the combustible recovery rate of flotation clean coal, the actual yield of flotation clean coal, the ash content of flotation clean coal, and the ash content of the feed, in percentages.

[0088] The flotation results of the collectors in Examples 1-5 and Comparative Examples 1-4 are shown in the table below:

[0089]

[0090] The flotation results above show that: using the collectors of Examples 1-7 of this invention (prepared from raw biodiesel and polyoxyethylene ether surfactants), and emulsifying the collector with emulsifier and water to form a microemulsion collector during coal slime flotation, with a total dosage of 1-3 kg / t dry coal slime, and adding the microemulsion collector in stages during slurry conditioning and flotation, the combustible recovery rate of clean coal is as high as 86.01-91.88%, and the ash content of clean coal is 13.57-14.88%.

[0091] Using the collectors of Comparative Examples 1 and 2 (prepared solely from raw biodiesel), the collectors were first emulsified with emulsifiers and water to form a microemulsion collector during coal slime flotation. The microemulsion collector was added twice, once during slurry conditioning and once during flotation, with each addition of the microemulsion collector at a dosage of 1 kg / t dry coal slime. The combustible recovery rates of the clean coal were 78.29% and 79.53%, respectively, both lower than those of Examples 1-7. The ash content of the clean coal was 15.25% and 15.60%, respectively, both higher than that of Examples 1-7.

[0092] The collector used in Comparative Example 3 (prepared from raw biodiesel and polyoxyethylene ether surfactant fatty alcohol polyoxyethylene ether AEO-5) was not emulsified into a microemulsion collector by emulsifier and water during coal slime flotation. The collector was added twice, once during slurry conditioning and once during flotation, with a dosage of 1 kg / t dry coal slime for each addition. The combustible recovery rate of the clean coal was 76.36%, which was lower than that of Examples 1-7. The ash content of the clean coal was 15.79%, which was higher than that of Examples 1-7.

[0093] The collector used in Comparative Example 4 (prepared from raw biodiesel and polyoxyethylene ether surfactant fatty alcohol polyoxyethylene ether AEO-5) was emulsified into a microemulsion collector by an emulsifier and water during coal slime flotation. However, the collector was added all at once during flotation, with a dosage of 2 kg / t dry coal slime. The combustible recovery rate of the clean coal was 77.04%, which was lower than that of Examples 1-7. The ash content of the clean coal was 16.03%, which was higher than that of Examples 1-7.

[0094] In contrast, when using the collector in Comparative Example 5 (a conventional commercially available diesel collector), the collector was not emulsified into a microemulsion collector by emulsifier and water during coal slime flotation. The collector was added all at once during flotation, with a dosage of 10 kg / t dry coal slime. The combustible recovery rate of the clean coal was 72.86%, which was lower than that of Examples 1-7. The ash content of the clean coal was 16.75%, which was higher than that of Examples 1-7.

[0095] In summary, compared with conventional commercially available diesel collectors and conventional flotation methods, the collectors of Examples 1-7 of this invention (prepared using raw materials biodiesel and polyoxyethylene ether surfactants), and the microemulsion collectors formed by emulsifying the collectors with emulsifiers and water during coal slime flotation, and the microemulsion collectors added in stages during slurry conditioning and flotation, even with a reduced amount of collector, still resulted in an increased recovery rate of combustible matter in clean coal by 18.05-26.10% and a decrease in clean coal ash content by 11.16-18.98%. Furthermore, the biodiesel and polyoxyethylene ether surfactants used in the collectors of Examples 1-7 of this invention are both renewable resources, demonstrating strong environmental safety.

[0096] The above embodiments are merely illustrative of the present invention and are not intended to limit the invention. Any obvious modifications made by those skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. An environmentally friendly and efficient coal slime flotation collector, characterized in that, It includes the following raw materials by weight percentage: 65-80% biodiesel and 20-35% polyoxyethylene ether surfactants.

2. The environmentally friendly and efficient coal slime flotation collector as described in claim 1, characterized in that, The biodiesel is produced from vegetable oil or animal fat through a transesterification process.

3. The environmentally friendly and efficient coal slime flotation collector as described in claim 1, characterized in that, The polyoxyethylene ether surfactant is a fatty alcohol polyoxyethylene ether or an alkylphenol polyoxyethylene ether.

4. The environmentally friendly and efficient coal slime flotation collector as described in claim 3, characterized in that, The fatty alcohol polyoxyethylene ether is AEO-3 or AEO-5.

5. The environmentally friendly and efficient coal slime flotation collector as described in claim 3, characterized in that, The alkylphenol polyoxyethylene ether is nonylphenol polyoxyethylene ether or octylphenol polyoxyethylene ether.

6. The environmentally friendly and efficient coal slime flotation collector as described in any one of claims 1 to 5, characterized in that, The collector is prepared as follows: a polyoxyethylene ether surfactant is added to biodiesel and stirred at 600-1000 rpm for 20-30 min to obtain the collector.

7. A method for flotation of coal slime, characterized in that, Includes the following steps: (1) The collector of claim 6 is stirred and mixed with emulsifier and water, and then ultrasonically emulsified to form a microemulsion collector; (2) Add coal slime into the slurry preparation tank and add water to prepare a flotation slurry with a concentration of 60-100 g / L; (3) Add half of the microemulsion collector from step (1) to the flotation slurry, stir and mix to obtain a slurry containing the collector; (4) Add the slurry containing the collector into the flotation machine, then add the remaining microemulsion collector, stir for 2-3 minutes, add the frother, fill with air for flotation, and scrape the foam for 2-4 minutes to obtain clean coal and tailings.

8. The coal slime flotation method as described in claim 7, characterized in that, In step (1), the emulsifier is lignin sulfonate, the mass ratio of collector to emulsifier and water is 1:0.2-0.3:4-6, the stirring speed is 200-250 r / min, and the stirring time is 20-30 min.

9. The coal slime flotation method as described in claim 5, characterized in that, In step (4), the foaming agent is 2-octanol or methyl isobutyl methanol, and the airflow rate is 0.2-0.4 L / min.

10. The coal slime flotation method as described in claim 5, characterized in that, The amount of collector used per ton of dry coal slime is 1-3 kg, and the amount of foaming agent used per ton of dry coal slime is 0.1-0.3 g.

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