A flotation system and method for a difficult-to-float coal type

Abstract

The application discloses a flotation system and method for difficult-to-float coal, and belongs to the field of advanced and green coal separation technology, and aims to solve at least one problem of large reagent consumption, poor collection effect and flotation selectivity, and low efficient recycling rate of difficult-to-float coal resources in the prior art. The flotation system comprises a slurry preparation barrel, a coal tar-based hydrocarbon oil emulsion preparation barrel, a hydrophobic modified engine carbon deposit barrel, a collector preparation barrel, a flotation machine, a clean coal collection barrel and a tail coal collection barrel. The discharge outlet of the coal tar-based hydrocarbon oil emulsion preparation barrel and the hydrophobic modified engine carbon deposit barrel is connected with the feed inlet of the collector preparation barrel, the discharge outlet of the collector preparation barrel is connected with the feed inlet of the slurry preparation barrel, the discharge outlet of the slurry preparation barrel is connected with the flotation machine, the clean coal discharge outlet of the flotation machine is connected with the feed inlet of the clean coal collection barrel, and the tail coal discharge outlet of the flotation machine is connected with the feed inlet of the tail coal collection barrel. The application can be used for the flotation of difficult-to-float coal.

Description

Technical Field

[0001] This invention belongs to the field of advanced green coal preparation technology, and in particular relates to a flotation system and flotation method for difficult-to-float coal types. Background Technology

[0002] Currently, hydrocarbon oil collectors or coal tar-based collectors are commonly used for the flotation of difficult-to-float coal types.

[0003] However, hydrocarbon oil collectors have high consumption rates and require large doses to be added to the slurry to achieve the desired collection effect. This not only increases flotation costs, but also leaves residual hydrocarbon oil in the clean coal product, reducing the environmental friendliness of subsequent processing and utilization of the clean coal.

[0004] Coal tar-based collectors have strong collecting activity and lower reagent consumption than hydrocarbon oil collectors. However, the direct use of coal tar in these collectors results in poor flotation selectivity and difficulty in dispersion due to the heavy components.

[0005] In summary, both of the above-mentioned collectors are insufficient for flotation of difficult-to-float coals, as they cannot balance reagent consumption, collection effect, and flotation selectivity. They fail to meet the requirements for efficient separation of difficult-to-float coals with low reagent consumption. Furthermore, residual reagents can affect the clean utilization of clean coal and limit the efficient recovery and utilization rate of difficult-to-float coal resources. Summary of the Invention

[0006] Based on the above analysis, the present invention aims to provide a flotation system and flotation method for difficult-to-float coals, in order to solve at least one of the following problems in the prior art: large reagent consumption for difficult-to-float coals, poor collection effect and flotation selectivity, and low efficiency of recovery and utilization of difficult-to-float coal resources.

[0007] The objective of this invention is mainly achieved through the following technical solutions: This invention provides a flotation system for difficult-to-float coal types, including a slurry mixing tank, a coal tar-based hydrocarbon oil emulsion mixing tank, a hydrophobic modified engine carbon deposit tank, a collector mixing tank, a flotation machine, a clean coal collection tank, and a tailings collection tank. The outlets of the coal tar-based hydrocarbon oil emulsion preparation tank and the hydrophobic modified engine carbon deposit tank are connected to the inlet of the collector preparation tank. The outlet of the collector preparation tank is connected to the inlet of the slurry mixing tank. The outlet of the slurry mixing tank is connected to the flotation machine. The clean coal outlet of the flotation machine is connected to the inlet of the clean coal collection tank. The tailings outlet of the flotation machine is connected to the inlet of the tailings collection tank.

[0008] Furthermore, in the collector preparation tank, coal tar-based hydrocarbon oil emulsion and hydrophobically modified engine carbon deposits are mixed to generate a flotation compound collector.

[0009] Furthermore, the hydrophobic modified engine carbon deposit container includes an industrial coal tar kettle, a hydrocarbon base oil kettle, a mixing reactor, a stratified settling tank, and an organic filter membrane assembly. The outlets of the industrial coal tar kettle and the hydrocarbon base oil kettle are connected to the inlet of the mixing reactor. The outlet of the mixing reactor is connected to the inlet of the stratified settling tank, and the outlet of the stratified settling tank is connected to the inlet of the organic filter membrane assembly.

[0010] This invention also provides a flotation method for difficult-to-float coal types, characterized by using the above-mentioned flotation system for flotation, and the method includes the following steps: Step S1: Prepare coal tar-based hydrocarbon oil emulsion and hydrophobic modified engine carbon deposits respectively. Put the coal tar-based hydrocarbon oil emulsion into a coal tar-based hydrocarbon oil emulsion preparation tank and put the hydrophobic modified engine carbon deposits into a hydrophobic modified engine carbon deposit tank. Step S2: The hydrophobic modified engine carbon deposits and coal tar-based hydrocarbon oil emulsion are fed into the collector preparation tank and mixed evenly to obtain the flotation compound collector. Step S3: Add the difficult-to-float coal type to be floated, along with the frother, water, and flotation compound collector, into the mixing tank and stir to prepare the slurry, thus obtaining the difficult-to-float coal slurry; Step S4: Transfer the difficult-to-float coal slurry into a flotation machine for flotation, and collect clean coal and tailings separately; Step S5: The clean coal in the flotation machine is discharged into the clean coal collection bucket, and the tailings in the flotation machine are discharged into the tailings collection bucket.

[0011] Furthermore, in step S3, the slurry concentration of the difficult-to-float coal slurry is 50 g / L to 100 g / L.

[0012] Furthermore, the mixing and slurry preparation time is 2-3 minutes.

[0013] Furthermore, in step S3, the amount of foaming agent used per ton of difficult-to-float coal is 0.08 kg to 0.1 kg.

[0014] Furthermore, in step S3, based on the mass of coal tar-based hydrocarbon oil, the amount of flotation compound collector used per ton of difficult-to-float coal is 3 kg to 5 kg.

[0015] Furthermore, in step S4, the flotation time is 3 min to 4 min, and the impeller speed of the flotation machine is 1500 r / min to 2000 r / min.

[0016] Furthermore, in step S4, the inflation rate is 120 mL / min to 150 mL / min.

[0017] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: A) The flotation system for difficult-to-float coal types provided by this invention introduces a compound flotation collector prepared by combining hydrophobically modified engine carbon deposits with coal tar-based hydrocarbon oil emulsion. On the one hand, it can reduce the overall amount of coal tar-based collector used, and enhance the collection effect by relying on the strong hydrophobicity of the hydrophobically modified engine carbon deposits themselves. Effective collection of difficult-to-float coal particles can be achieved without large-dose addition, thus reducing reagent costs. On the other hand, the particle structure of the hydrophobically modified engine carbon deposits can promote the dispersion of coal tar-based components in the slurry and reduce the adsorption of gangue by heavy coal tar components, thereby improving the selectivity of flotation and ensuring the quality of clean coal products while ensuring the yield of clean coal.

[0018] B) The flotation system for difficult-to-float coal types provided by this invention features hydrophobically modified engine carbon deposits with small size, large specific surface area, and high surface energy. These deposits can be rapidly adsorbed onto the surface of coal / residual carbon particles during the slurry preparation stage, especially in the polar oxygen-containing functional group regions of the coal surface, constructing localized strongly hydrophobic sites and filling the adsorption gap of traditional collectors. It can also disrupt the hydration film structure of polar sites on the coal surface, transforming it from a continuous state to a discrete state, reducing the hydrophilicity of the coal surface, and allowing bubbles to directly contact the coal surface. This significantly improves the flotation rate. Furthermore, it can act as a bridging agent, inducing multiple fine coal / residual carbon particles to form hydrophobic flocs, increasing the apparent particle size. It can also adsorb onto the bubble surface, increasing the surface roughness and hydrophobicity of the bubble, improving the single-bubble particle loading index, and greatly enhancing the flotation recovery rate.

[0019] C) The flotation system for difficult-to-float coals provided by this invention also exhibits a synergistic effect of dual mechanisms: synergistic adsorption sequence, synergistic adsorption intensity, synergistic hydrophobic performance, and synergistic selectivity and recovery rate. During slurry preparation, the smaller, higher surface energy hydrophobic modified engine carbon deposits are rapidly adsorbed onto polar sites on the coal surface, constructing initial hydrophobic sites. Subsequently, coal tar-based hydrocarbon oil molecules spread across these initial hydrophobic sites, covering other areas of the coal surface through π-π stacking and hydrogen bonding, ultimately forming a continuous, uniform, and robust composite hydrophobic film. The hydrophobic modified engine carbon deposits are physically adsorbed and anchored onto the coal surface, while the coal tar-based hydrocarbon oils are adsorbed onto the coal surface through π-π stacking and hydrogen bonding. The two interweave to form a composite adsorption layer of physical anchoring and chemical adsorption, with an adsorption intensity far exceeding that of a single collector adsorption layer, making it less prone to detachment during flotation stirring. The hydrophobic modified engine carbon deposits provide superhydrophobic local sites, while the coal tar-based hydrocarbon oils provide a continuous hydrophobic film. The combination of the two significantly improves the overall hydrophobicity of the coal surface.

[0020] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0021] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0022] Figure 1 A schematic diagram of the flotation system for difficult-to-float coal types provided by the present invention; Figure 2 A schematic diagram of the structure of the hydrophobic modified engine carbon deposit barrel in the flotation system for difficult-to-float coal types provided by the present invention; Figure 3 A flowchart of the flotation method for difficult-to-float coal types provided by the present invention. Detailed Implementation

[0023] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0024] In a first aspect, the present invention provides a flotation system for difficult-to-float coal types, see [link to previous section]. Figure 1 It includes a slurry mixing tank, a coal tar-based hydrocarbon oil emulsion mixing tank, a hydrophobic modified engine carbon deposit tank, a collector mixing tank, a flotation machine, a clean coal collection tank, and a tailings collection tank.

[0025] Among them, the outlet of the coal tar-based hydrocarbon oil emulsion preparation tank and the hydrophobic modified engine carbon deposit tank are connected to the inlet of the collector preparation tank, the outlet of the collector preparation tank is connected to the inlet of the slurry mixing tank, the outlet of the slurry mixing tank is connected to the flotation machine, the clean coal outlet of the flotation machine is connected to the inlet of the clean coal collection tank, and the tailings outlet of the flotation machine is connected to the inlet of the tailings collection tank.

[0026] In the collector preparation tank, coal tar-based hydrocarbon oil emulsion and hydrophobically modified engine carbon deposits are mixed to generate a flotation compound collector.

[0027] Compared with existing technologies, the flotation system for difficult-to-float coal types provided by this invention introduces a compound flotation collector prepared by combining hydrophobically modified engine carbon deposits with coal tar-based hydrocarbon oil emulsions. On the one hand, this reduces the overall amount of coal tar-based collector used, and enhances the collecting effect by relying on the strong hydrophobicity of the hydrophobically modified engine carbon deposits themselves. Effective collection of difficult-to-float coal particles can be achieved without large-dose addition, thus reducing reagent costs. On the other hand, the particle structure of the hydrophobically modified engine carbon deposits can promote the dispersion of coal tar-based components in the slurry, reduce the adsorption of gangue by heavy coal tar components, thereby improving the selectivity of flotation and ensuring the quality of clean coal products while maintaining the yield of clean coal.

[0028] It should be noted that hydrophobically modified engine carbon deposits are small in size, have a large specific surface area, and high surface energy. They can be rapidly adsorbed onto the surface of coal / residual carbon particles during the slurry preparation stage, especially in the polar oxygen-containing functional group regions of the coal surface, constructing localized strongly hydrophobic sites and filling the adsorption gap of traditional collectors. They can disrupt the hydration film structure of polar sites on the coal surface, transforming it from a continuous state to a discrete state, reducing the hydrophilicity of the coal surface, and allowing bubbles to directly contact the coal surface. They can significantly improve the flotation rate. They can also act as bridging agents, inducing multiple fine coal / residual carbon particles to form hydrophobic flocs, increasing the apparent particle size. Furthermore, they can be adsorbed onto the bubble surface, increasing the surface roughness and hydrophobicity of the bubble, improving the single bubble particle loading index, and significantly increasing the flotation recovery rate.

[0029] It should also be noted that the aforementioned hydrophobically modified engine carbon deposits and coal tar-based hydrocarbon oils also exhibit a synergistic effect with dual mechanisms: synergistic adsorption sequence, synergistic adsorption intensity, synergistic hydrophobic performance, and synergistic selectivity and recovery rate. During slurry preparation, the smaller, higher surface energy hydrophobically modified engine carbon deposits first rapidly adsorb onto the polar sites on the coal surface, constructing initial hydrophobic sites. Subsequently, coal tar-based hydrocarbon oil molecules spread across these initial hydrophobic sites, covering other areas of the coal surface through π-π stacking and hydrogen bonding, ultimately forming a continuous, uniform, and robust composite hydrophobic film. The hydrophobically modified engine carbon deposits are physically anchored to the coal surface, while the coal tar-based hydrocarbon oils are adsorbed onto the coal surface through π-π stacking and hydrogen bonding. The two intertwine to form a composite adsorption layer of physical anchoring and chemical adsorption, with an adsorption intensity far exceeding that of a single collector adsorption layer, making it less prone to detachment during flotation stirring. The hydrophobically modified engine carbon deposits provide superhydrophobic local sites, while the coal tar-based hydrocarbon oils provide a continuous hydrophobic film. The combination of the two significantly improves the overall hydrophobicity of the coal surface.

[0030] For details regarding the structure of the hydrophobic modified engine carbon deposit bin, please refer to [link / reference]. Figure 2It includes an industrial coal tar reactor, a hydrocarbon base oil reactor, a mixing reactor, a stratified settling tank, and an organic filter membrane assembly. The outlets of the industrial coal tar reactor and the hydrocarbon base oil reactor are connected to the inlet of the mixing reactor. The outlet of the mixing reactor is connected to the inlet of the stratified settling tank, and the outlet of the stratified settling tank is connected to the inlet of the organic filter membrane assembly.

[0031] The hydrophobic modified engine carbon deposit barrel with this structure can separate and extract heavy components from industrial coal tar. After being mixed and reacted with hydrocarbon base oil and allowed to stand for stratification, impurities are removed by filtration through an organic filter membrane to obtain light modified hydrocarbon components for subsequent collector compounding. This can solve the problems of poor dispersibility and low selectivity caused by heavy components in raw coal tar, and further improve the flotation performance of the collector.

[0032] Secondly, this invention also provides a flotation method for difficult-to-float coal types, see [link to relevant documentation]. Figure 3 The flotation process using the above-mentioned flotation system includes the following steps: Step S1: Prepare coal tar-based hydrocarbon oil emulsion and hydrophobic modified engine carbon deposits respectively. Put the coal tar-based hydrocarbon oil emulsion into a coal tar-based hydrocarbon oil emulsion preparation tank and put the hydrophobic modified engine carbon deposits into a hydrophobic modified engine carbon deposit tank. Step S2: The hydrophobic modified engine carbon deposits and coal tar-based hydrocarbon oil emulsion are fed into the collector preparation tank at a mass ratio of 3:10 to 5:10 and mixed evenly to obtain a flotation compound collector. Step S3: Add the difficult-to-float coal type to be floated, along with a frother (e.g., 2-octanol), water, and a compound flotation collector to a mixing tank and stir to prepare the slurry, thus obtaining the difficult-to-float coal slurry. Step S4: Transfer the difficult-to-float coal slurry into a flotation machine for flotation, and collect clean coal and tailings separately; Step S5: The clean coal in the flotation machine is discharged into the clean coal collection bucket, and the tailings in the flotation machine are discharged into the tailings collection bucket.

[0033] Compared with the prior art, the beneficial effects of the flotation method for difficult-to-float coal types provided by the present invention are basically the same as the beneficial effects of the flotation system for difficult-to-float coal types provided in the first aspect, and will not be elaborated here.

[0034] Furthermore, to address the issue of insufficient flotation efficiency, for example, in step S3 above, the concentration of the refractory coal slurry is 50 g / L to 100 g / L, and the stirring and conditioning time is 2 to 3 minutes. Controlling the slurry concentration within this range ensures sufficient dispersion of the flotation compound collector and frother during the conditioning process. Simultaneously, it allows sufficient space for coal particles to fully contact the reagents, preventing excessive gangue entrainment that reduces the quality of clean coal due to excessive concentration, and avoiding reduced flotation efficiency due to excessively low concentration. In addition, controlling the stirring and conditioning time within this range ensures that hydrophobically modified engine carbon deposits and coal tar-based hydrocarbon components are fully adsorbed onto the surface of the refractory coal particles. This prevents insufficient reagent adsorption due to insufficient conditioning time, which would affect the collection effect, and also avoids energy waste due to excessive conditioning time, which could lead to the detachment of already adsorbed reagents and negatively impact the flotation effect.

[0035] Correspondingly, the amount of frother used will also affect the flotation effect. For example, in step S3 above, the amount of frother used per ton of difficult-to-float coal is 0.08 kg to 0.1 kg. In this way, controlling the amount of frother within the above range can generate bubbles of appropriate size and stable quantity, providing sufficient bubble carriers for the mineralization process. This avoids insufficient frother usage leading to a small number of bubbles that cannot effectively capture hydrophobic coal particles, and also avoids excessive frother usage resulting in bubbles that are too small and too stable, increasing the entrainment of gangue particles and affecting the quality of clean coal.

[0036] Similarly, the dosage of the flotation compound collector also affects the flotation effect. For example, in step S3 above, based on the mass of coal tar-based hydrocarbon oil, the dosage of the flotation compound collector per ton of difficult-to-float coal is 3 kg to 5 kg. Controlling the dosage of the flotation compound collector within this range ensures sufficient hydrophobic site construction, achieving adequate collection of difficult-to-float coal particles.

[0037] To further address the issue of insufficient flotation efficiency, for example, in step S4 above, the flotation time is 3-4 minutes, the impeller speed of the flotation machine is 1500-2000 r / min, and the aeration rate is 120-150 mL / min. Controlling the flotation time within this range ensures that the target clean coal particles float sufficiently, preventing both insufficient flotation time leading to low clean coal recovery and excessive flotation time resulting in the entrainment of gangue and reduced clean coal quality. Controlling the impeller speed within this range ensures the slurry is in a suitable suspended and dispersed state, guaranteeing sufficient collision and mineralization between bubbles and coal particles, while mitigating the risk of mineralized coal particles detaching from the bubble surface due to excessive speed. Controlling the aeration rate within this range provides sufficient bubbles to participate in the mineralization process, preventing insufficient aeration leading to insufficient bubble quantity and reduced recovery rate, and preventing excessive aeration leading to increased bubble coalescence, decreased stability, increased gangue entrainment, and reduced clean coal quality.

[0038] Furthermore, in order to address the problem of insufficient stability in coal tar-based hydrocarbon oil emulsions, the preparation method of the coal tar-based hydrocarbon oil emulsion in step S1 above includes the following steps: Step S11: Place industrial coal tar and hydrocarbon base oil (e.g., diesel, kerosene, dodecane) in a constant temperature stirred reaction vessel at a volume ratio of 1:1 to 1:2. After stirring and extraction, allow the mixture to stand and separate into layers. Take the upper clear liquid and vacuum filter it to obtain coal tar-based hydrocarbon oil. Step S12: Mix coal tar-based hydrocarbon oil and deionized water at a volume ratio of 1:2 to 1:5 to obtain a mixture; Step S13: Add the emulsifier (a quaternary ammonium salt cationic surfactant of sodium dodecyl sulfate and hexadecyltrimethylammonium bromide or a composite emulsifier of sodium dodecyl sulfate and hexadecyltrimethylammonium bromide) to the mixture at a mass-volume ratio of 0.008:1 to 0.0091:1 (g / ml), and then perform ultrasonic emulsification using an ultrasonic emulsifier to obtain a coal tar-based hydrocarbon oil emulsion.

[0039] Among them, coal tar-based hydrocarbon oil includes aromatic light components (e.g., naphthalene, indene, phenanthrene, etc.) with molecular weights between 128 and 202 and long-chain alkanes of C10 to C20, with the mass percentage of aromatic light components being ≥30%.

[0040] The method described above for preparing coal tar-based hydrocarbon oil emulsions can effectively improve the dispersibility of coal tar-based hydrocarbon oils in the aqueous phase, resulting in emulsions with good stability. This makes them more suitable for subsequent compounding with hydrophobically modified engine carbon deposits, ensuring the collection effect and selectivity of the flotation compound collector.

[0041] In addition, selective extraction of coal tar by hydrocarbon oil can remove the heavy bitumen phase and solve the problem of the non-selective adsorption of gangue minerals by heavy bitumen components leading to a decrease in the grade of flotation clean coal.

[0042] Furthermore, in order to address the insufficient overall performance of hydrophobically modified engine carbon deposits, step S1 above, which modifies the collected automotive engine carbon deposits, includes the following steps: Step S11': Collect carbon deposits generated during the dismantling of a gasoline or diesel engine; Step S12': High-frequency magnetic separation is performed on the carbon deposit raw material to remove metal debris from the carbon deposit raw material, and the magnetically separated carbon deposit is obtained; Step S13': Clean the carbon deposits after magnetic separation with anhydrous ethanol at an ultrasonic power of 200W 2 to 3 times, each time for 10 to 12 minutes, to remove residual oil on the surface of the carbon deposits after magnetic separation, and obtain the cleaned carbon deposits; Step S14': Place the cleaned carbon deposits in a forced-air drying oven and dry them at 80℃~90℃ until constant weight to obtain coarse carbon deposits; Step S15': Place the coarse carbon deposits in a planetary ball mill, use anhydrous ethanol as the dispersion medium, and ball mill for 2 to 3 hours at a ball-to-material ratio of 10:1 to 12:1 and a rotation speed of 300 r / min to 350 r / min to deagglomerate the carbon deposit agglomerates formed by physical adhesion, thereby deagglomerating the 5 nm to 50 nm engine carbon deposit nanoparticles in the carbon deposit agglomerates to obtain the ball-milled coarse carbon deposits; Step S16': The coarse carbon deposits after ball milling are sieved through a 2000-mesh standard sieve to obtain engine carbon deposit nanopowder with a particle size of 5~50nm that retains its original high hydrophobicity. The engine carbon deposit nanopowder is then dried in a vacuum drying oven at 60℃~80℃ for later use. Step S17': Dissolve the hydrophobic modifier (e.g., stearic acid, silane coupling agent KH-570, or hexadecyltrimethylammonium bromide) in anhydrous ethanol to prepare a modifier solution with a mass concentration of 5%~8%. Add engine carbon deposit nanoparticles to the modifier solution. The mass ratio of engine carbon deposit nanoparticles to hydrophobic modifier is 100:1~50:1. Stir and modify for 1.5h~2.0h at 35℃~40℃ and 400r / min~500r / min. Then, perform vacuum filtration and dry the filter residue in a vacuum drying oven at 60℃~70℃ to constant weight to obtain hydrophobic modified engine carbon deposits with a contact angle ≥130°.

[0043] The above method employs a non-grinding process route combining purification, depolymerization, and hydrophobic modification. This approach preserves the original nanoparticle size and high specific surface area of ​​automotive engine carbon deposits while further enhancing their surface hydrophobicity, mitigating the destructive effect of high-energy ball milling on the original structure of the carbon deposit nanoparticles. Without damaging the original structure of the carbon deposits, this process introduces long-chain hydrophobic groups into the system, increasing the contact angle of the carbon deposit nanoparticles to over 130°. This efficiently prepares hydrophobically modified engine carbon deposits that meet the requirements for use with compound collectors, providing a performance foundation for subsequent efficient flotation of difficult-to-float coals in conjunction with coal tar-based hydrocarbon oils.

[0044] Specifically, magnetic separation can directly remove metal debris and impurities mixed in during the dismantling of engine carbon deposits, eliminating the adverse effects of metal impurities on the flotation process; anhydrous ethanol ultrasonic cleaning can remove unburned organic impurities such as engine oil and gasoline remaining on the surface of carbon deposits; planetary low-speed ball milling with anhydrous ethanol as the dispersion medium only deagglomerates carbon deposits formed by physical adhesion, without destroying the original nanostructure and surface chemical composition of the carbon deposits themselves, and can completely preserve the structural advantages of the original carbon deposit nanoparticles, such as high specific surface area, abundant surface defects and intrinsic high hydrophobicity; sieving can accurately separate target nanoparticles with a particle size of 5nm~50nm, alleviating the negative impact of large carbon deposit particles on the subsequent dispersion and adsorption processes.

[0045] Example 1 The preparation method of the flotation compound collector based on automobile engine carbon deposits in this embodiment includes the following steps: Step A: Industrial coal tar (taken from Xinjiang Zhongtai Coal Coking Company, density 1.15 g / cm³, aromatic light component content ≥40%) and diesel oil were placed in a constant temperature stirred reactor at a volume ratio of 1:2. After stirring and extraction at 50℃ and 400 r / min for 45 min, the mixture was allowed to stand at 25℃ for 3 h to separate into layers. The clear liquid in the upper layer was then vacuum filtered through a 0.22 μm organic filter membrane to obtain coal tar-based hydrocarbon oil. Step B: Collect the carbon deposits generated from the dismantling of the diesel engine, and perform high-frequency magnetic separation on the carbon deposits to obtain the magnetically separated carbon deposits; Step C: Clean the carbon deposits after magnetic separation twice with anhydrous ethanol at an ultrasonic power of 200W, each cleaning time is 10min, to obtain cleaned carbon deposits; place the cleaned carbon deposits in a forced-air drying oven at 80℃ and dry to constant weight to obtain coarse carbon deposits; Step D: Place the coarse carbon deposits in a planetary ball mill and use anhydrous ethanol as the dispersion medium. Ball mill for 3 hours at a ball-to-material ratio of 10:1 and a rotation speed of 350 r / min to obtain the ball-milled coarse carbon deposits. Step E: The coarse carbon deposits after ball milling are sieved through a 2000-mesh standard sieve to obtain engine carbon deposit nanopowder with a particle size of 5~30nm. The engine carbon deposit nanopowder is then dried in a vacuum drying oven at 60℃ for later use. Step F: Dissolve the hydrophobic modifier in anhydrous ethanol to prepare a modifier solution with a mass concentration of 8%. Add engine carbon deposit nanoparticles to the modifier solution. The mass ratio of engine carbon deposit nanoparticles to hydrophobic modifier (KH-570 and CTBA 1:1, analytical grade, Ron's reagent) is 50:1. After stirring and modifying for 1.5 h at 40℃ and 500 r / min, perform vacuum filtration. Place the filter residue in a vacuum drying oven at 70℃ and dry to constant weight to obtain superhydrophobic modified engine carbon deposit nanoparticles with a contact angle ≥130°. Step G: Mix coal tar-based hydrocarbon oil and deionized water at a volume ratio of 1:5 to obtain a mixture. Step H: After adding the emulsifier (CTAB, analytical grade, Ron's reagent) to the mixture, ultrasonic emulsification was performed for 8 minutes at a power of 250W using an ultrasonic emulsifier to obtain a water-in-oil coal tar-based hydrocarbon oil emulsion. The mass-volume ratio of the emulsifier to the total volume of coal tar-based hydrocarbon oil and deionized water was 0.008:1, g / ml. Step I: The superhydrophobic modified engine carbon deposit nanoparticles are added to the oil-in-water coal tar-based hydrocarbon oil emulsion under stirring. The mass ratio of the superhydrophobic modified engine carbon deposit nanoparticles to the coal tar-based hydrocarbon oil is 3:10. The mixture is stirred and mixed at 28℃ and 600r / min for 40min to obtain the initial mixture. Step J: The initial mixture is ultrasonically dispersed at 150W for 12 minutes to obtain the flotation compound collector; Step K: Add 50g of low-rank coal (Inner Mongolia Shanbula Mine, particle size <0.5mm, ash content 24.9%, moisture 12.00%), 2-octanol, water, and flotation compound collector to a mixing tank and stir to adjust the slurry concentration. The slurry concentration is 50g / L, the stirring time is 2min, the collector dosage is 5kg / t, and the 2-octanol dosage is 0.1kg / t to obtain the difficult-to-float coal slurry. Step L: Transfer the difficult-to-float coal slurry into the flotation machine for flotation. The flotation time is 4 min, the aeration rate is 150 mL / min, and the impeller speed is 1500 r / min. Collect clean coal and tailings separately. Step M: The clean coal in the flotation machine is discharged into the clean coal collection bucket, and the tailings in the flotation machine are discharged into the tailings collection bucket.

[0046] Test results: clean coal yield 78.5%, combustible gas recovery rate 89.2%, clean coal ash content 11.8%.

[0047] Example 2 The preparation method of the flotation compound collector based on automobile engine carbon deposits in this embodiment includes the following steps: Step A: Industrial coal tar (obtained from Xinjiang Zhongtai Coal Coking Company, density 1.15 g / cm³, aromatic light component content ≥40%) and kerosene (industrial grade, Beichen Fangzheng Reagent Factory) were placed in a constant temperature stirred reaction vessel at a volume ratio of 1:1. After stirring and extraction at 40℃ and 30 r / min for 60 min, the mixture was allowed to stand at 20℃ for 2 h to separate into layers. The clear liquid in the upper layer was then vacuum filtered through a 0.22 μm organic filter membrane to obtain coal tar-based hydrocarbon oil. Step B: Collect the carbon deposits generated from the dismantling of the gasoline engine, and perform high-frequency magnetic separation on the carbon deposits to obtain the magnetically separated carbon deposits; Step C: Clean the carbon deposits after magnetic separation three times, each time for 12 minutes, to obtain cleaned carbon deposits; place the cleaned carbon deposits in a forced-air drying oven at 90°C and dry to constant weight to obtain coarse carbon deposits; Step D: Place the coarse carbon deposits in a planetary ball mill and use anhydrous ethanol as the dispersion medium. Ball mill for 2 hours at a ball-to-material ratio of 10:1 and a rotation speed of 300 r / min to obtain the ball-milled coarse carbon deposits. Step E: The coarse carbon deposits after ball milling are sieved through a 2000-mesh standard sieve to obtain engine carbon deposit nanopowder with a particle size of 10~40nm. The engine carbon deposit nanopowder is then dried in an 80℃ vacuum drying oven for later use. Step F: Dissolve the hydrophobic modifier in anhydrous ethanol to prepare a 5% (w / w) modifier solution. Add engine carbon deposit nanoparticles to the modifier solution. The mass ratio of engine carbon deposit nanoparticles to hydrophobic modifier (stearic acid, analytical grade, Ron's reagent) is 100:1. After stirring and modifying for 2 hours at 35℃ and 400r / min, filter under reduced pressure. Place the filter residue in a vacuum drying oven at 60℃ and dry to constant weight to obtain superhydrophobic modified engine carbon deposit nanoparticles with a contact angle ≥130°. Step G: Mix coal tar-based hydrocarbon oil and deionized water at a volume ratio of 1:2 to obtain a mixture. Step H: After adding the emulsifier (SDS+CTAB 1:1) to the mixture, ultrasonic emulsification was performed for 10 minutes at a power of 200W using an ultrasonic emulsifier to obtain a water-in-oil coal tar-based hydrocarbon oil emulsion. The mass-volume ratio of the emulsifier to the total volume of coal tar-based hydrocarbon oil and deionized water was 0.009:1, g / ml. Step I: The superhydrophobic modified engine carbon deposit nanoparticles are added to the water-in-oil coal tar-based hydrocarbon oil emulsion under stirring. The mass ratio of the superhydrophobic modified engine carbon deposit nanoparticles to the coal tar-based hydrocarbon oil is 1:10. The mixture is stirred and mixed for 60 minutes at 25℃ and 500r / min to obtain the initial mixture. Step J: The initial mixture is ultrasonically dispersed at 100W power for 15 minutes to obtain the flotation compound collector; Step K: Add 50g of oxidized coal (Shaanxi Yulin mine, particle size <0.5mm, ash content 25.6%, surface oxygen functional group content ≥25%), 2-octanol, water, and flotation compound collector to the slurry mixing tank and stir to adjust the slurry concentration. The slurry concentration is 100g / L, the stirring time is 3min, the collector dosage is 3kg / t, and the 2-octanol dosage is 0.08kg / t to obtain the difficult-to-float coal slurry. Step L: Transfer the difficult-to-float coal slurry into the flotation machine for flotation. The flotation time is 4 min, the aeration rate is 120 mL / min, and the impeller speed is 2000 r / min. Collect clean coal and tailings separately. Step M: The clean coal in the flotation machine is discharged into the clean coal collection bucket, and the tailings in the flotation machine are discharged into the tailings collection bucket.

[0048] Test results: clean coal yield 72.3%, combustible gas recovery rate 82.5%, clean coal ash content 12.5% ​​(raw coal ash content 25.6%).

[0049] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A flotation system for difficult-to-float coal types, characterized in that, Including slurry mixing tank, coal tar-based hydrocarbon oil emulsion mixing tank, hydrophobic modified engine carbon deposit tank, collector mixing tank, flotation machine, clean coal collection tank and tailings collection tank; The outlets of the coal tar-based hydrocarbon oil emulsion preparation tank and the hydrophobic modified engine carbon deposit tank are connected to the inlet of the collector preparation tank. The outlet of the collector preparation tank is connected to the inlet of the slurry mixing tank. The outlet of the slurry mixing tank is connected to the flotation machine. The clean coal outlet of the flotation machine is connected to the inlet of the clean coal collection tank. The tailings outlet of the flotation machine is connected to the inlet of the tailings collection tank.

2. The flotation system for difficult-to-float coals according to claim 1, characterized in that, In the collector preparation tank, the coal tar-based hydrocarbon oil emulsion and hydrophobically modified engine carbon deposits are mixed to generate a flotation compound collector.

3. The flotation system for difficult-to-float coals according to claim 1, characterized in that, The hydrophobic modified engine carbon deposit container includes an industrial coal tar kettle, a hydrocarbon base oil kettle, a mixing reactor, a stratified settling tank, and an organic filter membrane assembly. The outlets of the industrial coal tar kettle and the hydrocarbon base oil kettle are connected to the inlet of the mixing reactor. The outlet of the mixing reactor is connected to the inlet of the stratified settling tank. The outlet of the stratified settling tank is connected to the inlet of the organic filter membrane assembly.

4. A flotation method for a type of coal that is difficult to float, characterized in that, Flotation is performed using the flotation system as described in any one of claims 1 to 3, wherein the flotation method includes the following steps: Step S1: Prepare coal tar-based hydrocarbon oil emulsion and hydrophobic modified engine carbon deposits separately. Put the coal tar-based hydrocarbon oil emulsion into a coal tar-based hydrocarbon oil emulsion preparation tank and put the hydrophobic modified engine carbon deposits into a hydrophobic modified engine carbon deposit tank. Step S2: The hydrophobic modified engine carbon deposits and coal tar-based hydrocarbon oil emulsion are fed into the collector preparation tank and mixed evenly to obtain the flotation compound collector. Step S3: Add the difficult-to-float coal type to be floated, along with the frother, water, and flotation compound collector, into the mixing tank and stir to prepare the slurry, thus obtaining the difficult-to-float coal slurry; Step S4: Transfer the difficult-to-float coal slurry into a flotation machine for flotation, and collect clean coal and tailings separately; Step S5: The clean coal in the flotation machine is discharged into the clean coal collection bucket, and the tailings in the flotation machine are discharged into the tailings collection bucket.

5. The flotation method for difficult-to-float coal types according to claim 4, characterized in that, In step S3, the slurry concentration of the difficult-to-float coal slurry is 50g / L~100g / L.

6. The flotation method for difficult-to-float coal types according to claim 4, characterized in that, The stirring and slurry preparation time is 2-3 minutes.

7. The flotation method for difficult-to-float coal types according to claim 4, characterized in that, In step S3, the amount of foaming agent used per ton of difficult-to-float coal is 0.08 kg to 0.1 kg.

8. The flotation method for difficult-to-float coal types according to claim 4, characterized in that, In step S3, based on the mass of coal tar-based hydrocarbon oil, the amount of flotation compound collector used per ton of difficult-to-float coal is 3 kg to 5 kg.

9. The flotation method for difficult-to-float coal types according to claim 4, characterized in that, In step S4, the flotation time is 3 min to 4 min, and the impeller speed of the flotation machine is 1500 r / min to 2000 r / min.

10. The flotation method for difficult-to-float coal types according to claim 4, characterized in that, In step S4, the inflation rate is 120 mL / min to 150 mL / min.

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