High-internal-phase water-in-oil emulsion type collecting agent for low-rank coal flotation and preparation method and application of high-internal-phase water-in-oil emulsion type collecting agent

Abstract

The invention discloses a low-rank coal flotation high-internal-phase water-in-oil emulsion type collecting agent and a preparation method and application thereof, and belongs to the technical field of mineral flotation process strengthening. The high-internal-phase water-in-oil emulsion type collecting agent for flotation of the low-rank coal comprises the following raw materials in percentage by mass: 75-90% of a water phase and 10-25% of an oil phase, the water phase comprises metal chloride and water, and the concentration of the metal chloride is 0.1-1 M; and the oil phase comprises an oily collecting agent and a water-in-oil emulsifier in a mass ratio of (1-5): 1. An oleophylic surfactant is adopted as an emulsifier, the mass ratio of an organic mixed solution to a metal chloride aqueous solution is adjusted, the internal phase volume fraction of the prepared emulsion can be regulated and controlled, and the problem that the collision and adhesion efficiency between a collecting agent and target particles is low due to the fact that the emulsion is large in particle size and poor in stability is effectively solved; therefore, the requirements of flotation production of coal preparation plants are met.

Description

Technical Field

[0001] This invention belongs to the field of mineral flotation process enhancement technology, specifically relating to a high internal phase oil-in-water emulsion collector for low-rank coal flotation, its preparation method, and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] In the field of clean coal separation, especially for low-rank coal with complex surface properties, the efficient separation of low-rank coal from associated gangue minerals remains a significant challenge in interfacial separation science. The core difficulty lies in the insufficient difference in interfacial wettability between low-rank coal and common aluminosilicate gangue minerals in conventional flotation systems, which constitutes a thermodynamic barrier to selective separation. Currently widely used straight-chain hydrocarbon collectors rely on physical adsorption and spreading on hydrophobic surfaces. However, for low-rank coal surfaces rich in oxygen-containing functional groups, this interaction is weak and difficult to overcome the obstruction of the surface hydration film. This results in unsatisfactory adsorption density and strength of collector molecules at the target mineral interface. Bubble-particle aggregates are prone to desorption in turbulent fields, making it difficult to synergistically optimize the selectivity and recovery rate of the flotation process. A large amount of reagent is consumed in ineffective adsorption or mechanical entrainment, creating a double burden on resources and economic costs.

[0004] To enhance the efficiency of reagent action on the target mineral surface, researchers attempted to disperse the collector into emulsion droplets to increase the mass transfer interface. However, this strategy revealed fundamental flaws in practical applications. Emulsions obtained through conventional mechanical emulsification are in a thermodynamically metastable state, with highly dispersed droplet sizes. In the strong fluid shear and high ionic strength slurry of the flotation cell, these droplets easily form large droplets through random collisions and aggregation, or undergo dissolution-precipitation leading to Ostwald ripening, thus rapidly losing the increased specific surface area advantage. This instability prevents the reagent from acting on the coal particle surface in a uniform, fine form. Instead, the uncontrollable droplet size exacerbates non-selective adhesion on gangue mineral surfaces and unhelpful loading on bubble surfaces, ultimately weakening separation accuracy.

[0005] Therefore, developing a novel collector construction strategy that combines precise control of interfacial activity with dynamic system stability is key to breaking through the current bottlenecks in low-rank coal flotation technology. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a high internal phase oil-in-water emulsion collector for low-rank coal flotation, its preparation method, and its application. By using a lipophilic surfactant as an emulsifier and adjusting the mass ratio of the organic mixture to the metal chloride aqueous solution, the internal phase volume fraction of the prepared emulsion can be controlled. This effectively solves the problem of low collision and adhesion efficiency between the collector and the target particles caused by the large particle size and poor stability of the emulsion, thereby meeting the needs of flotation production in coal preparation plants.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, the present invention provides a water-in-oil emulsion collector for flotation of low-rank coal, wherein the raw materials comprise, by mass percentage: 75-90% aqueous phase and 10-25% oil phase. The aqueous phase comprises metal chloride and water, wherein the concentration of the metal chloride is 0.1~1 M; The oil phase comprises an oily harvesting agent and a water-in-oil emulsifier in a mass ratio of (1~5):1.

[0008] In some embodiments of the present invention, the metal chloride is any one or more of sodium chloride, potassium chloride, magnesium chloride, and aluminum chloride.

[0009] In some embodiments of the present invention, the oily harvesting agent is any one or more of diesel oil, kerosene, oleic acid esters, oleic acid, erucic acid, and cocoaluminamine.

[0010] In some embodiments of the present invention, the water-in-oil emulsifier is any one or more of Span, glyceryl monostearate, sodium oleate, and sodium erucic acid.

[0011] In some embodiments of the present invention, the raw material of the low-rank coal flotation high internal phase oil-in-water emulsion collector, by mass percentage, comprises: 85-90% aqueous phase and 10-15% oil phase.

[0012] In some embodiments of the present invention, the raw material of the low-rank coal flotation high internal phase oil-in-water emulsion collector, by mass percentage, comprises: 85-90% aqueous phase and 10-15% oil phase; the oil phase is a mixture of diesel oil, methyl oleate and oil-in-water emulsifier.

[0013] A second aspect of the present invention provides a method for preparing the high internal phase oil-in-water emulsion collector for low-rank coal flotation as described in the first aspect, comprising: The aqueous phase is added to the well-mixed oil phase under stirring to obtain a high internal phase water-in-oil emulsion collector.

[0014] In some embodiments of the present invention, an oily collecting agent and a water-in-oil emulsifier are mixed and sheared at a speed of 600-800 r / min for 5-10 min to obtain a mixed oil phase.

[0015] In some embodiments of the present invention, the aqueous phase is added to the oil phase at a rate of ≤5 mL / min, and the mixture is stirred at a speed of 1400~1500 r / min during the addition process to obtain a high internal phase water-in-oil emulsion type collector.

[0016] In some embodiments of the present invention, the aqueous phase is added to the oil phase at a rate of 5 mL / min.

[0017] A third aspect of the present invention provides an application of the high internal phase oil-in-water emulsion collector described in the first aspect in the flotation of low-rank coal.

[0018] A fourth aspect of the present invention provides a method for flotation of low-rank coal, comprising: Adjust the concentration of the low-rank coal slurry, add the low-rank coal flotation high internal phase oil-in-water emulsion collector described in the first aspect, and after it is mixed with the slurry, add a frother, stir well, and then carry out aeration flotation to obtain clean coal.

[0019] In some embodiments of the present invention, the concentration of the low-rank coal slurry is 80-100 g / L, and the dosage of the low-rank coal high internal phase oil-in-water emulsion collector is 1.12-1.33 kg per ton of coal.

[0020] In some embodiments of the present invention, the foaming agent is any one or more of 2-octanol, methyl isobutyl methanol, and pine oil, and the amount of the foaming agent is 0.9-1.1 kg / t.

[0021] In some embodiments of the present invention, the aeration rate is 0.15-0.20 m³ during aerated flotation. 3 / (m 2 The stirring speed is 1800~2100 r / min, and the flotation time is 2~4 min.

[0022] The beneficial effects of this invention are as follows: This invention provides a high-internal-phase oil-in-water emulsion collector for low-rank coal flotation, fundamentally revolutionizing the agent's action mode at the low-rank coal-water interface through physicochemical innovation. Compared to traditional agents, this system achieves synergistic effects of multiple interfaces at the microscopic level by constructing a unique structure with a high-concentration metal chloride aqueous solution as the dispersed internal phase and an oily agent as the continuous phase. First, the high internal-phase structure endows the emulsion with viscoelasticity and high interfacial density similar to a soft solid, making it less prone to breakage or rebound when colliding with coal particles in turbulent slurry. Furthermore, through viscous spreading and capillary action, it effectively embeds into and seals the porous structure of the coal surface, thereby thermodynamically reducing the solid-water interfacial energy and enhancing the depth of hydrophobic modification. Second, the high concentration of metal ions (such as Na+) in the aqueous phase... + Mg 2+ Al 3+ This emulsion system compresses the double electric layer on the surface of coal particles and gangue, partially disrupting the strong hydration film on their surface. This significantly reduces the adhesion energy barrier between bubbles and modified coal particles, improving the feasibility of flotation kinetics. Furthermore, due to its extremely high internal phase volume fraction, this emulsion system exhibits significant shear-thinning characteristics rheologically, facilitating pipeline transport and addition. It also disperses rapidly in the strong shear zone of the flotation cell, ensuring efficient transfer of active components. Ultimately, this design based on a dual mechanism of "structural oil film" and "hydration film inhibition" not only significantly improves the recovery selectivity of target minerals but also reduces consumption caused by ineffective reagent leakage and desorption at the source, providing an innovative reagent solution for the efficient and low-carbon flotation of low-rank coal. Attached Figure Description

[0023] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0024] Figure 1 These are physical images of the collectors obtained in Examples 1, 2 and 3 of this invention.

[0025] Figure 2 The ΔBS dynamic stability curves of the collectors obtained in Examples 1, 2 and 3 of this invention are shown.

[0026] Figure 3 The ΔBS dynamic stability analysis curves are for the collectors obtained in Examples 1, 2 and 3 of this invention.

[0027] Figure 4 The TSI value variation curves of the collectors obtained in Examples 1, 2 and 3 of this invention are shown. Detailed Implementation

[0028] The inherent strong hydrophilicity and porous structure of low-rank coal severely limit the selective spreading and adsorption of collectors, and the formation of a robust hydration film hinders effective bubble adhesion. Simultaneously, conventional emulsions, as reagent delivery systems, are prone to instability during flotation due to their wide droplet size distribution and insufficient physical stability, leading to low reagent utilization and non-selective adsorption. Ultimately, this makes it difficult to achieve efficient and precise interface modification, constrained by the inherent properties of coal particles and the technical bottlenecks of reagent delivery systems. To address these challenges, this invention proposes a high-internal-phase water-in-oil emulsion collector for low-rank coal flotation, its preparation method, and its application.

[0029] This invention utilizes a lipophilic surfactant as an emulsifier and adjusts the mass ratio of the organic mixture to the aqueous metal chloride solution to control the internal phase volume fraction of the prepared emulsion. The specific calculation formula is as follows: (1) in, The volume fraction of the inner phase in a high internal phase water-in-oil emulsion is %, %. The masses, in grams, are the dispersed phase and the continuous phase, respectively. The densities, in g / cm³, are the dispersed phase and the continuous phase, respectively. 3 .

[0030] By further altering the proportions and types of components in the organic mixture, a high-internal-phase water-in-oil emulsion collector with excellent collecting performance and kinetic stability for the target mineral can be screened out. This effectively solves the problem of low collision and adhesion efficiency between the collector and the target particles due to the large particle size and poor stability of the emulsion, thus meeting the needs of flotation production in coal preparation plants.

[0031] This invention provides a water-in-oil emulsion collector for low-rank coal flotation with high internal phase, wherein the raw materials comprise, by mass percentage: 75-90% aqueous phase and 10-25% oil phase; The aqueous phase comprises metal chloride and water, wherein the concentration of the metal chloride is 0.1~1 M; The oil phase comprises an oily harvesting agent and a water-in-oil emulsifier in a mass ratio of (1~5):1.

[0032] This invention provides a novel flotation reagent for low-rank coal flotation. Compared with traditional hydrocarbon oil collectors, this high internal phase oil-in-water emulsion collector emulsion for low-rank coal flotation has a smaller particle size (micrometer level) and excellent dispersibility and stability. It can significantly improve the collision probability and adhesion efficiency between emulsion droplets and target mineral particles, thereby effectively improving the hydrophobic properties of low-rank coal surface and the separation efficiency with hydrophilic gangue minerals, and effectively solving the problem of low flotation efficiency for low-rank coal.

[0033] This invention, by adjusting the ratio of organic mixture to metal chloride aqueous solution, can prepare a micron-sized, highly stable, and selectively adsorbed water-in-oil emulsion with a high internal phase. This emulsion effectively covers the abundant hydrophilic sites, fissures, and large pores on the surface of low-rank coal, significantly reducing the specific surface area and porosity of low-rank coal. This mitigates the reduction in collector efficacy caused by collector droplets penetrating into the pores, thereby greatly reducing the amount of collector required and saving production costs.

[0034] The high internal phase water-in-oil emulsion collector prepared by this invention has excellent kinetic and thermodynamic stability. It can maintain a uniform and stable state during long-term storage and transportation and is not prone to stratification, agglomeration or Ostwald ripening, thus providing a guarantee and convenience for coal preparation production.

[0035] The high internal phase water-in-oil emulsion collector designed in this invention can flexibly adjust the formulation and preparation process of the internal and external phases according to the surface characteristics of different low-rank coals (such as the content of oxygen-containing functional groups, pore structure, etc.), showing high adaptability and flexibility.

[0036] In this invention, the metal chloride is any one or more of sodium chloride, potassium chloride, magnesium chloride, and aluminum chloride.

[0037] The cations (Na+) that dissociate from these specific metal chlorides in the aqueous phase + K + Mg 2+ Al 3+ Through the synergistic effect of valence state and concentration, the double electric layer on the surface of low-rank coal and gangue minerals is effectively compressed, weakening the strength of their interfacial hydration film, thereby significantly reducing the energy barrier for the adhesion of bubbles and coal particles. At the same time, the high ionic strength aqueous phase, as the internal phase, can regulate the rheology and Ostwald ripening resistance of the emulsion, ensuring the physicochemical stability of the high internal phase structure in the flotation environment, and achieving precise plugging and hydrophobic modification of the target coal particle pores by the reagent.

[0038] In this invention, the oily harvesting agent is any one or more of diesel oil, kerosene, oleic acid esters, oleic acid, erucic acid, and cocoaluminamine.

[0039] By synergistically combining polar and nonpolar components, precise adaptation to the complex surface properties of low-rank coal is achieved. Nonpolar diesel and kerosene provide basic hydrophobic coverage; while oleic acid, erucic acid, cocoagulant, and esters containing functional groups such as carboxyl and amine groups can be specifically anchored to oxygen-containing active sites on the surface of low-rank coal through chemical adsorption or hydrogen bonding, thereby enhancing the adsorption strength while improving the selectivity for coal particles (rather than hydrophilic gangue).

[0040] In this invention, the water-in-oil emulsifier is any one or more of Span, glyceryl monostearate, sodium oleate, and sodium erucic acid.

[0041] By combining emulsifiers with different hydrophilic-lipophilic balance (HLB) values ​​and charge properties, a robust and adaptable interfacial film was constructed for high internal phase water-in-oil emulsions. Nonionic emulsifiers (such as Span and glyceryl monostearate) provide steric stability, making them less susceptible to the effects of high concentrations of metal ions in the aqueous phase; while anionic emulsifiers (such as sodium oleate and sodium erucic acid) can synergistically work with the polar functional groups in oily collectors to further reduce interfacial tension and enhance the mechanical strength of emulsion droplets. This ensures that the emulsion can effectively resist aggregation, stratification, and Ostwald ripening in long-term storage, transportation, and high-ionic-strength flotation environments, maintaining uniform dispersion of micron-sized droplets, thereby ensuring the continuous and stable action of active components on the surface of target coal particles.

[0042] In this invention, the raw material of the low-rank coal flotation high internal phase oil-in-water emulsion collector, by mass percentage, comprises: 85-90% aqueous phase and 10-15% oil phase.

[0043] Through precise optimization of the phase ratio, an optimal balance between structural stability, functionality, and economy was achieved in the high internal phase emulsion. This specific range ensures an extremely high aqueous phase volume fraction, enabling the dispersed internal phase droplets to achieve a close-packed state, thereby forming a high internal phase emulsion with a gel-like network structure in the oil phase. This structure endows the emulsion with excellent kinetic stability, effectively inhibiting droplet aggregation and Ostwald ripening. Simultaneously, this ratio ensures that the entire high internal phase system can be constructed and stably encapsulated with minimal oil phase (including more expensive collectors and emulsifiers), minimizing reagent costs while ensuring effective coverage of coal particle surface pores and stable flotation performance.

[0044] In this invention, the raw material of the low-rank coal flotation high internal phase oil-in-water emulsion collector, by mass percentage, comprises: 85-90% aqueous phase and 10-15% oil phase; the oil phase is a mixture of diesel oil, methyl oleate and oil-in-water emulsifier.

[0045] Diesel oil, as a non-polar, low-cost hydrocarbon base, provides basic hydrophobic coverage and spreading capabilities. Methyl oleate, as a typical oleic acid ester, has ester functional groups that can specifically anchor to oxygen-containing active sites on the surface of low-rank coal through stronger dipole interactions and hydrogen bonds, significantly improving adsorption selectivity and robustness. The two are blended in a specific ratio to achieve synergistic coverage and modification of different regions (non-polar regions and polar sites) on the surface of coal particles.

[0046] This invention also provides a method for preparing the above-mentioned high internal phase oil-in-water emulsion collector for low-rank coal flotation, comprising: The aqueous phase is added to the well-mixed oil phase under stirring to obtain a high internal phase water-in-oil emulsion collector.

[0047] In this invention, an oily collecting agent and a water-in-oil emulsifier are mixed and sheared at a speed of 600-800 r / min for 5-10 min to obtain a mixed oil phase.

[0048] By employing moderate shearing at low to medium speeds, sufficient pre-emulsification and homogenization of the components within the oil phase are achieved. This operation ensures complete dispersion of the water-in-oil emulsifier in oily collectors such as diesel fuel and methyl oleate, forming a uniform and continuous phase. This lays a homogeneous and stable oil phase foundation for the subsequent construction of high internal phase emulsions. Specific speed and time ranges (600–800 r / min, 5–10 min) are optimized to provide sufficient shear force to break up emulsifier agglomeration, promote effective dissolution and distribution, while avoiding excessive air introduction or localized overheating due to excessive shearing. This ensures the reproducibility of subsequent emulsification processes and the stability of the final emulsion product performance.

[0049] In this invention, the aqueous phase is added to the oil phase at a rate of ≤5 mL / min, and the mixture is stirred at a speed of 1400~1500 r / min during the addition process to obtain a high internal phase water-in-oil emulsion collector.

[0050] By precisely coordinating low-speed constant-flow addition with high-speed shear stirring, controllable construction and excellent stability of the high internal phase emulsion structure were achieved. The aqueous phase was slowly added at a rate of ≤5 mL / min, ensuring that the aqueous droplets were continuously and fully encapsulated by the oil phase, effectively preventing phase transitions or emulsion breakage caused by excessive local concentration of the aqueous phase. Simultaneously, under high-speed shearing at 1400–1500 r / min, the added aqueous phase was instantly dispersed into uniform, narrowly distributed micron-sized droplets, which then densely packed within the oil phase, forming a gel-like high internal phase emulsion with a three-dimensional network structure. This precise process control is crucial for obtaining emulsion products with fine, uniform droplets, long-term stability, and resistance to Ostwald ripening, directly determining the efficiency and reliability of the final collector in flotation.

[0051] In this invention, the aqueous phase is added to the oil phase at a rate of 5 mL / min.

[0052] The present invention also provides an application of the above-mentioned high internal phase oil-in-water emulsion collector for low-rank coal flotation.

[0053] The present invention also provides a flotation method for low-rank coal, comprising: Adjust the concentration of the low-rank coal slurry, add the low-rank coal flotation high internal phase oil-in-water emulsion collector described in the first aspect, and after it is mixed with the slurry, add a frother, stir well, and then carry out aeration flotation to obtain clean coal.

[0054] By optimizing the process steps and precisely applying novel reagents, a highly efficient, stable, and adaptable low-rank coal separation process system was constructed. This method first pretreats the slurry using the aforementioned high internal phase emulsion collector, allowing sufficient time to cover the hydrophilic sites on the coal particle surface and reducing the influence of porosity. Then, a frother is added for aeration flotation. This sequence ensures that the emulsion preferentially and thoroughly modifies the hydrophobicity of the coal particles, thereby significantly improving the selective adhesion efficiency between subsequent bubbles and target coal particles. The entire process organically combines the unique properties of the reagents with flotation engineering operations, achieving a complete closed loop from "reagent innovation" to "process efficiency enhancement," providing a directly implementable solution for the efficient and economical separation of low-rank coal.

[0055] In this invention, the concentration of the low-rank coal slurry is 80-100 g / L, and the dosage of the low-rank coal high internal phase oil-in-water emulsion collector is 1.12-1.33 kg per ton of coal.

[0056] The above limitations provide a precise and repeatable industrial operating window for the application of novel high-internal-phase emulsion collectors. Specifically limiting the slurry concentration to 80-100 g / L optimizes the collision efficiency and hydrodynamic environment between coal particles, reagents, and bubbles, ensuring the flotation system has sufficient solids loading to increase throughput while maintaining good dispersibility and flowability. Simultaneously, the collector dosage is precisely set at 1.12-1.33 kg per ton of coal, an economically efficient addition based on the emulsion's efficient spreading and adsorption characteristics. This achieves sufficient hydrophobicity of the coal particle surface while minimizing reagent costs and non-selective adsorption. The synergistic setting of these two key process parameters enables the laboratory-innovated reagents to be stably and efficiently applied in actual flotation production, providing core engineering guarantees for technology transfer and ensuring separation indicators (high recovery rate and clean coal quality).

[0057] In this invention, the foaming agent is any one or more of 2-octanol, methyl isobutyl methanol, and pine oil, and the amount of the foaming agent is 0.9-1.1 kg / t.

[0058] The above limitations ensure that the entire flotation system is equipped with a mature, reliable, and highly compatible foaming solution. The selected 2-octanol, methyl isobutyl methanol, or pine oil are all commonly used foaming agents with long-term industrial validation. They can generate bubbles of moderate size and suitable stability in the environment where this specific pulp concentration coexists with a novel high-internal-phase emulsion collector. These bubbles can effectively carry low-rank coal particles, which have been sufficiently hydrophobized by the emulsion collector, to the float, while avoiding the generation of excessive viscous foam that would affect the separation efficiency.

[0059] In this invention, the aeration rate during aerated flotation is 0.15-0.20 m³. 3 / (m 2 The stirring speed is 1800~2100 r / min, and the flotation time is 2~4 min.

[0060] The aforementioned constraints provide a precisely controlled kinetic environment for flotation separation, ensuring efficient and stable separation results. The aeration rate is set to generate sufficient and appropriately sized bubble clusters, providing adequate carriers for hydrophobic coal particles. The stirring speed ensures thorough mixing and collision of the slurry, reagents, and bubbles, while avoiding damage to already formed mineralized bubbles due to excessive shear. The flotation time, while balancing processing efficiency, allows for a reasonable window for the full flotation and separation of the target mineral (clean coal). The synergistic optimization of these three core operating parameters, perfectly matched with the preceding reagent system and slurry conditions, constitutes a highly efficient, controllable, and energy-efficient flotation process.

[0061] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0062] The raw materials used in the following examples are all commercially available products that can be purchased.

[0063] Example 1 A high internal phase oil-in-water emulsion collector for low-rank coal flotation comprises, by mass, 90% an aqueous solution of metal chloride, 6.67% an oily collecting agent, and 3.33% an oil-in-water emulsifier. The aqueous solution of metal chloride is a 0.3 mol / L sodium chloride solution, the oily collecting agent is a mixture of diesel oil and methyl oleate (mass ratio 1:2), and the oil-in-water emulsifier is Span80.

[0064] The high internal phase water-in-oil emulsion collector is prepared according to the following steps: (1) Weigh each component by mass: 90 parts of 0.3 mol / L sodium chloride aqueous solution, 6.67 parts of diesel oil and methyl oleate compound (mass ratio 1:2) reagent, and 3.33 parts of Span80.

[0065] (2) Weigh the diesel oil and methyl oleate compound (mass ratio 1:2) and Span80 into a beaker and mix them evenly on a magnetic stirrer (speed 800 r / min, stirring time 5 min, room temperature) to prepare an organic mixture.

[0066] (3) Use a constant flow pump to add the weighed 0.3 mol / L sodium chloride aqueous solution to the mixed organic liquid at a constant rate of 5 mL / min. During the addition process, stir the mixture at a speed of 1500 r / min. When the sodium chloride aqueous solution is added, the high internal phase oil-in-water emulsion type collector can be prepared.

[0067] Example 2 A high internal phase oil-in-water emulsion collector for low-rank coal flotation comprises, by weight, 85% of a metal chloride aqueous solution, 7.5% of an oily collecting agent, and 7.5% of an oil-in-water emulsifier. The metal chloride aqueous solution is a 0.3 mol / L magnesium chloride aqueous solution, the oily collecting agent is a mixture of diesel oil and methyl oleate (mass ratio 1:3), and the oil-in-water emulsifier is Span80.

[0068] The high internal phase water-in-oil emulsion collector is prepared according to the following steps: (1) Weigh each component by mass: 85 parts of 0.3 mol / L magnesium chloride aqueous solution, 7.5 parts of diesel oil and methyl oleate compound (mass ratio 1:3) reagent, and 7.5 parts of Span80.

[0069] (2) Weigh the diesel oil and methyl oleate compound (mass ratio 1:3) and Span80 into a beaker and mix them evenly on a magnetic stirrer (speed 800 r / min, stirring time 5 min, room temperature) to prepare an organic mixture.

[0070] (3) Use a constant flow pump to add the weighed 0.3 mol / L magnesium chloride aqueous solution to the mixed organic liquid at a constant rate of 5 mL / min. During the addition process, stir the mixture at a speed of 1500 r / min. When the magnesium chloride aqueous solution is added, the high internal phase water-in-oil emulsion type collector can be prepared.

[0071] Example 3 A high internal phase oil-in-water emulsion collector for low-rank coal flotation comprises, by mass, 75% an aqueous solution of metal chloride, 18.75% an oily collecting agent, and 6.25% an oil-in-water emulsifier. The aqueous solution of metal chloride is a 0.3 mol / L aluminum chloride solution, the oily collecting agent is a mixture of diesel oil and methyl oleate (mass ratio 1:1), and the oil-in-water emulsifier is Span80.

[0072] The high internal phase water-in-oil emulsion collector is prepared according to the following steps: (1) Weigh each component by mass: 75 parts of 0.3 mol / L aluminum chloride aqueous solution, 18.75 parts of diesel oil and methyl oleate compound (mass ratio 1:1) reagent, and 6.25 parts of Span80.

[0073] (2) Weigh the diesel oil and methyl oleate compound (mass ratio 1:1) and Span80 into a beaker and mix them evenly on a magnetic stirrer (speed 800 r / min, stirring time 5 min, room temperature) to prepare an organic mixture.

[0074] (3) Use a constant flow pump to add the weighed 0.3 mol / L aluminum chloride aqueous solution to the mixed organic liquid at a constant rate of 5 mL / min. During the addition process, stir the mixture at a speed of 1500 r / min. When the aluminum chloride aqueous solution is added, the high internal phase water-in-oil emulsion type collector can be prepared.

[0075] Example 4 A high internal phase oil-in-water emulsion collector for low-rank coal flotation comprises, by mass parts: 90% aqueous solution of metal chloride, 6.67% oily collecting agent, and 3.33% water-in-oil emulsifier. The aqueous solution of metal chloride is a 0.5 mol / L sodium chloride solution, the oily collecting agent is kerosene, and the water-in-oil emulsifier is glyceryl monostearate.

[0076] The high internal phase water-in-oil emulsion collector is prepared according to the following steps: (1) Weigh each component by mass: weigh 90 parts of 0.5 mol / L sodium chloride aqueous solution, 6.67 parts of kerosene, and 3.33 parts of glyceryl monostearate.

[0077] (2) Place the weighed kerosene and glyceryl monostearate in a beaker and mix them evenly on a magnetic stirrer (rotation speed of 800 r / min, stirring time of 5 min, room temperature) to prepare an organic mixture.

[0078] (3) Use a constant flow pump to add the weighed 0.5 mol / L sodium chloride aqueous solution to the mixed organic liquid at a constant rate of 5 mL / min. During the addition process, stir the mixture at a speed of 1500 r / min. When the sodium chloride aqueous solution is added, the high internal phase water-in-oil emulsion type collector can be prepared.

[0079] Example 5 A high internal phase oil-in-water emulsion collector for low-rank coal flotation comprises, by mass, 90% an aqueous solution of metal chloride, 6.67% an oily collecting agent, and 3.33% an oil-in-water emulsifier. The aqueous solution of metal chloride is a 0.5 mol / L magnesium chloride aqueous solution, the oily collecting agent is oleic acid, and the oil-in-water emulsifier is sodium oleate.

[0080] The high internal phase water-in-oil emulsion collector is prepared according to the following steps: (1) Weigh each component by mass: weigh 90 parts of magnesium chloride aqueous solution, 6.67 parts of oleic acid, and 3.33 parts of sodium oleate.

[0081] (2) Place the weighed oleic acid and sodium oleate in a beaker and mix them evenly on a magnetic stirrer (rotation speed of 800 r / min, stirring time of 5 min, room temperature) to prepare an organic mixture.

[0082] (3) Use a constant flow pump to add the weighed 0.5 mol / L magnesium chloride aqueous solution to the mixed organic liquid at a constant rate of 5 mL / min. During the addition process, stir the mixture at a speed of 1500 r / min. When the magnesium chloride aqueous solution is added, the high internal phase water-in-oil emulsion type collector can be prepared.

[0083] Example 6 A high internal phase oil-in-water emulsion collector for low-rank coal flotation comprises, by mass, 90% an aqueous solution of metal chloride, 6.67% an oily collecting agent, and 3.33% an oil-in-water emulsifier. The aqueous solution of metal chloride is a 0.5 mol / L aluminum chloride aqueous solution, the oily collecting agent is erucic acid, and the oil-in-water emulsifier is sodium erucate.

[0084] The high internal phase water-in-oil emulsion collector is prepared according to the following steps: (1) Weigh each component by mass: Weigh 90 parts of aluminum chloride aqueous solution, 6.67 parts of erucic acid, and 3.33 parts of sodium erucic acid.

[0085] (2) Place the weighed erucic acid and sodium erucic acid in a beaker and mix them evenly on a magnetic stirrer (rotation speed of 800 r / min, stirring time of 5 min, room temperature) to prepare an organic mixture.

[0086] (3) Use a constant flow pump to add the weighed 0.5 mol / L aluminum chloride aqueous solution to the mixed organic liquid at a constant rate of 5 mL / min. During the addition process, stir the mixture at a speed of 1500 r / min. When the aluminum chloride aqueous solution is added, the high internal phase water-in-oil emulsion type collector can be prepared.

[0087] Comparative Example 1 Diesel fuel alone was used as a collector.

[0088] Comparative Example 2 This comparative example provides a collector that differs from Example 1 in that it does not contain Span80, while the other raw materials and preparation methods are the same.

[0089] Comparative Example 3 This comparative example provides a collector that differs from Example 1 in that it contains 70% aqueous metal chloride solution, 26.67% oily collecting agent, and 3.33% water-in-oil emulsifier, while the remaining raw materials and preparation methods are the same.

[0090] Comparative Example 4 This comparative example provides a collector, which differs from Example 1 in that: a constant flow pump is used to add a weighed 0.3 mol / L sodium chloride aqueous solution to the mixed organic liquid at a constant rate of 10 mL / min, while the other raw materials and preparation methods are the same.

[0091] Experimental example: All examples yielded high-performance internal phase emulsion collectors. The high-internal phase emulsion collectors prepared in the examples were applied and tested to illustrate the effects of the examples.

[0092] (1) Macroscopic morphology characterization of high internal phase water-in-oil emulsion collectors Taking the high internal phase water-in-oil emulsion collectors prepared in Examples 1-3 as examples, their performance was tested, specifically: like Figure 1 The images shown are macroscopic photographs of the high internal phase water-in-oil emulsion collectors prepared in Examples 1-3. Figure 1 As can be seen, the emulsion-type collector exhibits a milky white macroscopic morphology. Among them, the high internal phase water-in-oil emulsion prepared in Example 1 exhibits good mechanical strength and viscosity, and the viscosity of Examples 2 and 3 shows a gradual decrease compared to Example 1.

[0093] (2) Characterization of particle size distribution of high internal phase water-in-oil emulsion collectors Taking the high internal phase water-in-oil emulsion collectors prepared in Examples 1-3 as examples, their performance was tested, specifically: The particle size of the high internal phase water-in-oil emulsion collector described or prepared in this invention was statistically analyzed using a TURBISCAN multiple light scattering instrument (Formulaction, France). The particle size test results are shown below. Figure 2The results showed that the average particle size of the three high internal phase water-in-oil emulsions did not change significantly during the 6-hour test period, indicating that no aggregation or Ostwald ripening occurred during the emulsion storage, demonstrating high stability. Furthermore, the average particle size of the obtained high internal phase water-in-oil emulsions ranged from 0.78 to 1.22 µm, with Example 1 exhibiting the smallest particle size and best dispersibility.

[0094] (3) Dynamic stability characterization of high internal phase water-in-oil emulsion collectors Taking the emulsion-type collectors prepared in Examples 1-3 as examples, their performance was tested, specifically: like Figure 3 and Figure 4 The figures show the ΔBS dynamic stability analysis curves and TSI value variation curves of the high internal phase water-in-oil emulsion collectors prepared in Examples 1-3, obtained using a TURBISCAN multiple light scattering instrument (Formulaction, France). TSI (Dynamic Stability Index) is calculated using the following formula: (2) in, This represents the change in backscattered light intensity; The measurement is for height, in mm; n is the number of tests.

[0095] The smaller the TSI value, the more stable the system is during storage and the less likely it is to stratify or aggregate. The stability ranking is: Example 1 > Example 2 > Example 3.

[0096] (4) Conducting flotation tests on low-rank coal using the high internal phase water-in-oil emulsion collector prepared according to the present invention includes the following steps: The concentration of low-rank coal slurry was adjusted to 90 g / L. A high internal phase water-in-oil emulsion collector was added, and the mixture was stirred for 2 minutes. Then, a frother was added, and the mixture was stirred until homogeneous. After waiting for 30 seconds, aeration flotation was performed. The aeration rate was 0.15 m³ / s. 3 / (m 2 The stirring speed was 2100 r / min, and the flotation time was about 3 min.

[0097] It should be noted that the coal sample used in the test was long-flame coal with an ash content of 16.21%. The raw coal was crushed, screened, blended, and reduced in size to prepare analytical coal samples with a particle size less than 0.5 mm according to the "Methods for Preparing Coal Samples" (GB474-1984). The test methods followed the "Test Methods for Flotation in Coal Preparation Laboratory Units" (GB4758-1984) for performance testing, with a pulp concentration of 90 g / L, a flotation machine stirring speed of 2100 r / min, and an aeration rate of 0.15 m³ / min. 3 / (m 2The flotation time is 3 min, and the reagent dosage is 1.23 kg / t.

[0098] It should be further noted that the amount of water-in-oil emulsion collector used in flotation was 1.23 kg / t, while the collector used in Comparative Example 1 was diesel oil alone, with a dosage of 1400 g / t. Furthermore, 2-octanol was used as the frother in all cases, at a dosage of 1000 g / t. In other embodiments, the frother may also be one or a mixture of 2-octanol, methyl isobutyl methanol, and pine oil.

[0099] The effectiveness of flotation is assessed using flotation perfection indicators. Combustible gas recovery rate The evaluation is performed using the following formula: (3) (4) in, The yield of clean coal is %; The ash content of refined coal is % %. The ash content of the feed material is %.

[0100] The specific test results are shown in Table 1.

[0101] Table 1 Performance Test Results

[0102] As shown in Table 1, compared with the experimental results of Comparative Example 1, the high internal phase water-in-oil emulsion collectors prepared in Examples 1-3 of this invention, with a 60% reduction in dosage, yielded similar ash content and flotation improvement indicators for the flotation clean coal, while effectively improving clean coal yield and recovery rate of flotation combustibles. This is because emulsifying traditional non-polar oil collectors into high internal phase water-in-oil emulsions significantly increases the specific surface area of ​​droplets, increasing the probability of selective adsorption to low-rank coal particles. Simultaneously, surfactant molecules in the emulsifier are directionally adsorbed onto the hydrophobic regions of coal particles and covered with hydrophilic oxygen-containing groups, enhancing hydrophobicity. Furthermore, micro-oil droplets can "bind" multiple target mineral particles together, forming hydrophobic aggregates, which not only improves the recovery rate of target minerals but also significantly accelerates their flotation rate. Ultimately, while reducing collector dosage, the clean coal yield is effectively increased. This further verifies the advantages of the novel emulsion collector in improving the flotation efficiency of low-rank coal.

[0103] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high internal phase oil-in-water emulsion collector for low-rank coal flotation, characterized in that, By mass percentage, its raw materials include: 75-90% aqueous phase and 10-25% oil phase; The aqueous phase comprises metal chloride and water, wherein the concentration of the metal chloride is 0.1~1 M; The oil phase comprises an oily harvesting agent and a water-in-oil emulsifier in a mass ratio of (1~5):

1.

2. The high internal phase oil-in-water emulsion collector for low-rank coal flotation as described in claim 1, characterized in that, The metal chloride is any one or more of sodium chloride, potassium chloride, magnesium chloride, and aluminum chloride.

3. The high internal phase oil-in-water emulsion collector for low-rank coal flotation as described in claim 1, characterized in that, The oil-based harvesting agents are any one or more of diesel oil, kerosene, oleic acid esters, oleic acid, erucic acid, and cocoaluminamine.

4. The high internal phase oil-in-water emulsion collector for low-rank coal flotation as described in claim 1, characterized in that, The water-in-oil emulsifier is any one or more of Span, glyceryl monostearate, sodium oleate, and sodium erucic acid.

5. The high internal phase oil-in-water emulsion collector for low-rank coal flotation as described in claim 1, characterized in that, The raw materials for the low-rank coal flotation high internal phase oil-in-water emulsion collector, by mass percentage, include: 85-90% aqueous phase and 10-15% oil phase; Preferably, by mass percentage, the raw material for the low-rank coal flotation high internal phase oil-in-water emulsion collector includes: 85-90% aqueous phase and 10-15% oil phase; the oil phase is a mixture of diesel oil, methyl oleate and oil-in-water emulsifier.

6. A method for preparing a high internal phase oil-in-water emulsion collector for low-rank coal flotation according to any one of claims 1-5, characterized in that, include: The aqueous phase is added to the well-mixed oil phase under stirring to obtain a high internal phase water-in-oil emulsion collector.

7. The preparation method according to claim 6, characterized in that, The oily collecting agent and the water-in-oil emulsifier are mixed and sheared at a speed of 600~800 r / min for 5~10 min to obtain the mixed oil phase; Preferably, the aqueous phase is added to the oil phase at a rate of ≤5 mL / min, and the mixture is stirred at a speed of 1400~1500 r / min during the addition process to obtain a high internal phase water-in-oil emulsion type collector; Further preferably, the aqueous phase is added to the oil phase at a rate of 5 mL / min.

8. The application of the high internal phase oil-in-water emulsion collector for low-rank coal flotation as described in any one of claims 1-5 in the flotation of low-rank coal.

9. A flotation method for low-rank coal, characterized in that, include: Adjust the concentration of the low-rank coal slurry, add the low-rank coal flotation high internal phase oil-in-water emulsion collector as described in any one of claims 1-5, and after it is mixed with the slurry, add a foaming agent, stir well, and then carry out aeration flotation to obtain clean coal.

10. The low-rank coal flotation method as described in claim 9, characterized in that, The concentration of the low-rank coal slurry is 80-100 g / L, and the dosage of the low-rank coal high internal phase oil-in-water emulsion collector is 1.12-1.33 kg per ton of coal. Preferably, the foaming agent is any one or more of 2-octanol, methyl isobutyl methanol, and pine oil, and the amount of the foaming agent is 0.9-1.1 kg / t. Preferably, when performing aerated flotation, the aeration rate is 0.15-0.20 m³. 3 / (m 2 The stirring speed is 1800~2100 r / min, and the flotation time is 2~4 min.

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