Atomized Reagent Addition with Synchronized Jet Pre-Mineralization to Enhance the Flotation Process: Study on Atomization Parameters and Mechanisms of Enhancement

Abstract

The atomized reagent and synchronous jet pre-mineralization technology, as a novel method to enhance the flotation process, increases the solubility of fatty acid collectors in pulp through atomized reagent application and improves the mineralization effect and flotation rate via synchronous jet pre-mineralization technology, thereby laying a theoretical foundation for the flotation of minerals with fatty acid collectors. Systematic studies on the atomization method, atomization particle size, and flotation experiments revealed that, compared with conventional stirring methods, the atomized reagent method increases the solubility of sodium oleate in pulp from 82.5 mg/L to 142.9 mg/L at 288.15 K. The induction time for quartz particles treated with atomized reagents and bubbles is significantly lower than that of the conventional stirring method. Semi-industrial test results of the atomized reagent and synchronous jet pre-mineralization show that, compared to traditional roughing, the TFe grade increased by 0.87 percentage points, iron recovery increased by 3.95 percentage points, and reagent consumption decreased by 7.5 percentage points. Experimental and test results demonstrate that the atomized reagent and synchronous jet pre-mineralization technology can effectively enhance mineralization, accelerate the flotation rate, improve flotation indices, and reduce reagent consumption to a certain extent, providing significant guidance for the efficient recovery of fine-grained minerals.

1. Introduction

Flotation technology, as a crucial component in mineral processing, directly impacts the recovery rate of fine-grained mineral resources. The dispersion and homogenization of reagents, especially their uniform distribution within the slurry, are vital for the success of the flotation process. Traditional flotation reagent addition methods, such as direct mixing and water emulsification, perform well with water-soluble reagents but show limitations when dealing with poorly water-soluble fatty acid collectors. This issue is particularly pronounced in the iron-silicon separation process of Anshan-type poor hematite ores.

To address this challenge, researchers have developed a novel reagent addition technology—the atomized reagent method. This technology disperses reagents into micron-sized droplets using high-pressure differentials or ultrasonic waves, forming a “reagent-air aerosol”. These droplets exhibit good stability due to electrostatic repulsion preventing coagulation and demulsification [1]. Additionally, the high specific surface area of the micron-sized droplets enhances their solubility in aqueous solutions, effectively increasing the reagent’s dispersion within the slurry [2,3,4]. Particularly for fatty acid reagents with long hydrophobic hydrocarbon chains, traditional water emulsification methods tend to cause droplet coagulation and demulsification. Atomized reagent application allows for better dispersion, improving reagent efficacy, accelerating flotation, reducing reagent consumption, and enhancing flotation performance, especially for sulfide, oxide, and low-grade refractory ores [5].

The application of atomized reagent technology not only enhances reagent efficacy and flotation speed but also reduces reagent consumption and improves flotation indicators. In the flotation of ultrafine coal slurry, Misra demonstrated that atomized collectors dispersed within bubbles and hydrophobic coal particles adsorbed on bubble surfaces, leading to increased flotation selectivity and recovery rates [6]. Furthermore, Pan calculated the changes in surface tension along the hydration film at the solid–liquid–gas interface in atomized reagent flotation, showing that surface tension gradually decreases along the film, preventing film thinning and improving selective adsorption, thus providing a theoretical basis for enhanced selective adsorption [7].

In practical industrial applications, Wang compared the structures, working principles, advantages, and disadvantages of four commonly used coal flotation reagent atomization devices: ultrasonic atomizers, misting disks, pressure nozzles, and high-pressure gas jet atomizers [8]. The Linhuan Coal Preparation Plant significantly reduced flotation reagent consumption and production costs through technology modifications, creating considerable economic benefits [9]. Zhao and Xie optimized reagent atomization device structures, achieving reduced reagent consumption and improved flotation performance [10,11]. Xu demonstrated that the atomized reagent system enhanced the flotation process in copper-molybdenum separation, resulting in improved molybdenum recovery rates [12,13]. Studies showed that the droplet diameter range of atomized kerosene by ultrasonic treatment was 0.3–20 μm, with the highest distribution around 1.8 μm and 5 μm. Flotation tests indicated that atomized reagent addition could increase molybdenum recovery by 3% and reduce flotation time by approximately 20%, with a 40% reduction in kerosene consumption at the same recovery rate.

As the embedding size of the target mineral within the ore decreases, achieving monomeric liberation of the target mineral requires progressively finer grinding. This trend poses significant challenges for the reagents and equipment utilized in mineral separation. Fine-grained minerals have low mass and inertia, reducing collision probability with bubbles in turbulent environments compared to coarse particles. Jet technology can enhance turbulence intensity, increasing the momentum of fine-grained mineral particles and their collision probability with bubbles, improving mineralization efficiency, particularly for particles smaller than 20 μm [14,15]. Recent studies indicate that under conditions of high liquid velocity and low bed height, a high turbulence intensity environment can be established, significantly enhancing the separation efficiency of fine particles [16]. Research on bubble size regulation should focus on the industrial application of micron-sized bubble generation technologies, as well as the effects of multifactor coupling on bubble dimensions [17]. Furthermore, the innovative design of the Reflux Flotation Cell (RFC), proposed by Galvin, incorporates upper and lower channels, a vertical chamber, and inclined channels, significantly improving bubble generation and separation efficiency through a unique fluidized feed mechanism [18].

Induction time, a critical concept in studying particle–bubble mineralization, was first proposed by Sven–Nilsson (1934) [19]. Nguyen divided the particle–bubble adhesion process into three stages: film thinning, film rupture forming a three-phase contact line, and contact line expansion stabilizing adhesion [20]. Yin elaborated on the definition of induction time, detailing the evolution of testing methods and techniques. Additionally, he systematically analyzed recent research advancements regarding the factors influencing induction time, including bubble characteristics, particle properties, and solution environment [21]. Researchers have developed automated devices, and the high-speed imaging technique was also used to record contact processes and accurately evaluate influencing factors [22]. Induction time is affected by factors such as particle physicochemical properties, bubble size, and relative motion speed between particles and bubbles. Studies have shown that increasing particle and bubble sizes increases induction time, while increasing particle contact angles shortens induction time [23,24,25]. Additionally, solution chemistry, such as ion concentration, type, pH, and temperature, also impacts induction time. For instance, specific ions in solution can affect the electrical double layer compression on particle surfaces, altering induction time [26]. Wang Rang found that ultrasonic treatment reduced raw coal induction time from 145 ms to 85 ms, enhancing coal particle hydrophobicity and particle–bubble collision/adhesion efficiency and accelerating mineralization [27].

Furthermore, techniques such as floc flotation for recovering fine-grained minerals and novel three-phase fluidized bed flotation columns (TFC) for enhancing bubble dispersion provide new pathways for improving flotation efficiency [28,29]. Computational fluid dynamics (CFD) optimization of flotation equipment also offers powerful tools for better understanding and improving flotation processes [30].

In summary, atomized reagent application combined with synchronized jet pre-mineralization technology shows great potential in enhancing reagent homogenization and bubble mineralization efficiency. Particularly in the iron–silicon separation processes of iron ore concentration plants in northeast China, where Anshan-type lean hematite is prevalent, enhancing the selectivity of fatty acid collectors at a slurry temperature of 288.15 K during winter flotation workshops is crucial for the efficient recovery of resources.

2. Materials and Methods

2.1. Samples and Reagents

The fatty acid collectors were sourced from the reagent workshop of an iron ore concentrator in Anshan. The test ore samples were obtained from the mixed concentrates of strong magnetic separation and weak magnetic separation processes at the concentration plant. The TFe grade of the samples was 49.53%, with a grinding fineness (percentage of −0.074 mm product) of 95.00%. The reagents used in the experiment are listed in

Table 1. Flotation reagent.

Name	Application	Specifications	Manufacturer
Sodium hydroxide	pH Regulator	AR	Aladdin
Starch from corn	Depressant	LR	Macklin
Calcium oxide	Activator	LR	Macklin
Fatty acid	Collector	AR	Beneficiation Plant

Notice: AR means analytical reagent; LR means laboratory reagent.

.

2.2. Sample Mineralogy Analysis

Representative samples were prepared as test targets using cold mounting with epoxy resin. The targets underwent three stages of mechanical grinding—coarse, intermediate, and fine—followed by a single polishing step. Finally, the targets were carbon-coated using an ETD-2000C ion sputter coater to ensure surface conductivity. The automated mineralogical testing system, controlled via an application programming interface (API), integrates a scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS) for automated operation. The carbon-coated targets were then analyzed using a BPMA (Tescan VGA3) SEM equipped with a Thermo Scientific NORAN System 7 EDS featuring a 60 mm² X-ray detector, which performed automatic measurements of all particles across the entire target area.

2.3. Reagent Atomization Particle Size Testing

The droplet size of atomized reagents was measured using laser Doppler velocimetry (LDV) equipment manufactured by Arlium. LDV is a common non-contact measurement technique for analyzing liquid droplet sizes. This technique involves laser illumination, collection of scattered light, Doppler shift, and frequency measurement to analyze the droplet size of atomized reagents. The LDV system comprises a laser source, beam shaping and splitting system, probe, receiving optical system, photodetector, signal processing unit, data acquisition and analysis system, calibration and alignment devices, and supporting structures. A schematic of the droplet size measurement for ultrasonic atomization and jet atomization is shown in Figure 1.

2.4. Collector Solubility and Particle-Bubble Induction Time Testing

The solubility of the fatty acid collector in water was tested using gas chromatography. Two different methods of reagent addition were employed: conventional stirring and jet atomization. First, 200 mg of the fatty acid collector was added to a 1000 mL volumetric flask filled with deionized water at a temperature of 288.15 K, and then the solution was made up to the 1000 mL mark. For the conventional stirring method, a magnetic stirrer was used at a stirring speed of 1800 r/min for 3 min. The jet atomization method was also carried out for 3 min. These parameters were chosen to match the stirring speed and duration used in the laboratory single-cell flotation tests.

After preparation, 1 mL of the solution was taken from the same position in both flasks and transferred to pressure-resistant tubes. To these, 5 mL of boron trifluoride methanol solution and 5 mL of sodium hydroxide methanol solution were added, and the mixtures were reacted in an oven at 373.15 K for 90 min. After cooling to room temperature, 2 mL of n-hexane was added for extraction. The samples were then filtered and analyzed using an Agilent 8860 GC gas chromatograph. The injector temperature was set to 543.15 K, and the detector temperature was set to 563.15 K. The flow rate through the chromatography column was 1 mL per minute, with a split ratio of 10:1 between the sample entering the column and the sample being vented.

The solutions prepared with the two different reagent addition methods were each sampled five times. Deionized water was used to dilute five samples each from conventional stirring and jet atomization to concentrations of 10 mg/L, 30 mg/L, 50 mg/L, 70 mg/L, and 100 mg/L, and then the solutions were volumetrically adjusted to 50 mL. Pure quartz mineral was crushed and ground, with the 53–74 μm fraction sieved out as the test sample. Ten quartz samples, each weighing 20 g, were prepared. These samples were stirred in a 500 mg/L calcium oxide solution at pH 11.5 for 3 min and then filtered. The quartz samples were added to the aforementioned fatty acid solutions and stirred for 3 min. After standing for 2 h, the quartz particles were washed with deionized water to remove the fatty acid reagent from their surface. The cleaned quartz particles were then transferred to a Particle and Bubble Observation Cell for particle–bubble induction time testing. The bubbles had a diameter of 1.5 mm, and the collision speed between the bubbles and particles was 0.025 m/s. For each condition, the bubbles needed to collide with particles at 10 different positions, with at least 7 successful collisions required to determine the induction time under that condition. The particle–bubble induction time testing system is shown in Figure 2.

2.5. Flotation Tests and Flotation Kinetic Models

There are two main methods of atomizing the collector agent: ultrasonic atomization and jet atomization. The equipment setup for ultrasonic atomization is shown in Figure 3a. This method uses ultrasonic waves to atomize the collector into small droplets and is significantly influenced by the reagent concentration, making it suitable for low-concentration small-scale laboratory flotation machines. The setup for jet atomization is depicted in Figure 3b. This method utilizes the Venturi effect, where high-pressure gas atomizes the reagent into small droplets. The droplet size is slightly larger compared to ultrasonic atomization, but this method is more affected by equipment factors, making it suitable for larger-scale flotation test equipment.

Flotation kinetics experiments were conducted using an XFD (1 L) single-cell flotation machine produced by the Jilin Province Exploration Machinery Factory and a synchronized jet pre-mineralization system for atomized reagent addition. The atomized reagent addition apparatus comprises components such as an air compressor, jet atomizer, gas flow meter, and ultrasonic atomizer. The jet pre-mineralization system, illustrated in Figure 4, consists mainly of a mixing tank, slurry pump, pre-mineralization device, and flotation cell.

The working principle is as follows: The synchronized jet pre-mineralization flotation system can be divided into the reagent atomization zone, pre-mineralization zone, and stabilized mineralized bubble flotation zone. In the pre-mineralization zone, the slurry, atomized reagent, and gas are injected into the mineralization tube in jet form. In the highly turbulent environment, the reagent interacts fully with the slurry, and the gas is sheared into numerous tiny bubbles that continuously collide and adsorb onto the mineral particles, completing the mineralization process. The mineralized bubbles are then expelled from the bottom of the mineralization tube, rising quickly to the slurry surface in the flotation cell to form a froth layer, thus achieving the separation of target minerals from gangue minerals.

Laboratory flotation test conditions were as follows: flotation slurry concentration was 35%, slurry temperature was 293.15 K, and the magnetic concentrate was transferred to the flotation cell, stirred at 1800 r/min for 3 min for thorough wetting. Subsequently, the pH adjuster (sodium hydroxide solution), depressant (starch), and activator (calcium oxide) were added sequentially at 3-min intervals with dosages of 1500 g/t, 500 g/t, and 500 g/t, respectively. The fatty acid collector was added in the following ways: (1) direct mixing in the single-cell flotation machine using a pipette with a reagent dosage of 200 g/t; (2) ultrasonic atomization in the single-cell flotation machine, where the collector is atomized into small droplets and introduced into the flotation cell with a reagent dosage of 200 g/t; (3) direct mixing in the jet pre-mineralization system using a pipette with a reagent dosage of 200 g/t; (4) jet atomization in the jet pre-mineralization system, where the collector is atomized into small droplets and introduced into the pre-mineralization device’s air inlet with a reagent dosage of 200 g/t.

The semi-industrial test equipment setup is the same as shown in Figure 4, with the flotation cell volume expanded from 50 L to 1500 L. The flotation slurry flow rate was 2.5 t/h, the slurry mass concentration was 630 kg/m³, and the slurry temperature was 293.15 K. The test slurry, having already had the pH modifier, depressant, and activator added, was drawn from the outlet of the mixing tank. The fatty acid collector was added separately in the pre-mineralization system.

Using classical first-order kinetic model 1 and model 2, the influence of conventional and atomized reagent addition methods on the reverse flotation behavior of iron ore with fatty acid collectors was studied. The actual flotation indices were fitted to the models to determine the maximum gangue recovery rate ${Ɛ}_{\infty }$ and flotation time t. The flotation rate constant k was evaluated under different conditions based on the fitted flotation rate constants. The r² represents the fit accuracy of the selected model to the experimental results, r² with higher values indicating better fit accuracy.

$${Ɛ}_{\left(\mathrm{t}\right)}={Ɛ}_{\infty }\times \left(1-{\mathrm{e}}^{-\mathrm{k}\times \mathrm{t}}\right)$$

(1)

$${Ɛ}_{\left(\mathrm{t}\right)}={\displaystyle \frac{{Ɛ}_{\infty }^2\times \mathrm{k}\times \mathrm{t}}{1+{Ɛ}_{\infty }\times \mathrm{k}\times \mathrm{t}}}$$

(2)

Since this flotation process is reverse flotation, ${Ɛ}_{\left(\mathrm{t}\right)}$ represents the cumulative gangue recovery rate, t is the flotation time, ${Ɛ}_{\infty }$ is the theoretical maximum gangue recovery rate, and k is the flotation rate constant.

2.6. Pre-Mineralization Device Numerical Simulation

According to the semi-industrial experimental parameters, Fluent 2022 R1 software was employed to simulate and model the internal flow field of a single pre-mineralization tube based on the Eulerian model. Boundary conditions included liquid phase inlet velocity of 0.25 m/s and gas phase inlet velocity of 0.4 m/s. The simulation employs the phase coupled SIMPLE numerical solution method and is configured for 10,000-time steps, each with a duration of 0.0005 s.

The jet pre-mineralization model and mesh division are illustrated in Figure 5. Key parameters and meshing details for the pre-mineralization model are summarized in

Table 2. Key part parameters and meshing parameter table of pre-mineralization model.

Key Part	Parameter	Meshing	Parameter
Nozzle inner diameter (mm)	10	Cell type	Mixed cells
Air inlet inner diameter (mm)	15	Cells	1,348,979
Mineralization tube inner diameter (mm)	100	Maximum cell size (mm)	4
Mineralization tube length (mm)	800	Minimum cell size (mm)	2
Outlet hole inner diameter (mm)	10	Nodes	3,420,094
Outlet hole number	340	Total Volume (m3)	5.980152 × 10−3

. The pre-mineralization model mesh has been meticulously designed, consisting of 1,348,979 mixed cells, 5,917,442 faces, and 3,420,094 nodes. This substantial number of nodes ensures sufficient resolution for the accuracy of the numerical solution. The mesh’s configuration of cells and faces is appropriate for supporting relatively complex flow simulations. It is partitioned into eight active sections, which optimizes computational efficiency while maintaining a balanced distribution of cells and faces. The carefully designed velocity inlet and pressure outlet faces enhance the simulation of fluid flow boundary conditions. Overall, the intricate mesh structure in the pre-mineralization model effectively captures the complexities of fluid dynamic processes, thereby improving the accuracy and stability of the simulation.

3. Results

3.1. Analysis of Atomized Droplet Size of Fatty Acid Collectors

The selection of atomizers and the mass percentage of reagents significantly affect droplet size. Laser Doppler velocimetry was employed to measure the droplet sizes of atomized reagents under different conditions. The results of jet atomization of the reagent droplet sizes are shown in Figure 6.

From Figure 6, it can be observed that at a distance of 10 mm from the nozzle, the D99 droplet sizes corresponding to gas pressures of 0.15 MPa, 0.30 MPa, 0.45 MPa, and 0.60 MPa are 37.6 μm, 31.7 μm, 29.8 μm, and 26.8 μm, respectively. At a distance of 30 mm from the nozzle, the D99 droplet sizes for the same gas pressures are 35.5 μm, 29.6 μm, 27.9 μm, and 24.6 μm, respectively. At a distance of 50 mm from the nozzle, the D99 droplet sizes are 33.8 μm, 28.6 μm, 24.8 μm, and 19.3 μm, respectively. At all three distances (10 mm, 30 mm, and 50 mm from the nozzle), the D99 droplets of the atomized reagent decrease with increasing jet gas pressure. Similarly, the D10, D50, and D90 droplet sizes also decrease with increasing gas pressure. Under the same gas pressure conditions, the droplet sizes decrease with increasing distance from the nozzle. As shown in Figure 7a, at a gas pressure of 0.45 MPa and a distance of 30 mm from the nozzle, the D10, D50, D90, and D99 droplet sizes all show a decreasing trend with increasing reagent mass percentage. As illustrated in Figure 7c, with a reagent mass percentage of 20%, the D99 droplet size for jet atomization is 27.7 μm, with droplet sizes primarily concentrated between 15 and 30 μm.

The laser Doppler test results for ultrasonic atomization, as shown in Figure 7b, indicate that at reagent mass percentages of 0%, 10%, and 20%, the D10 droplet sizes are 8.7 μm, 7.7 μm, and 7.1 μm respectively; the D50 droplet sizes are 10 μm, 8.8 μm, and 8.1 μm, respectively; the D90 droplet sizes are 11.5 μm, 10.2 μm, and 9.3 μm, respectively; and the D99 droplet sizes are 15.2 μm, 13.7 μm, and 12.4 μm, respectively. With increasing reagent mass percentage, the D10, D50, D90, and D99 droplet sizes all show a decreasing trend. As shown in Figure 7d, at a reagent mass percentage of 20%, the D99 droplet size for ultrasonic atomization is 12.4 μm, with droplet sizes primarily concentrated between 6–12 μm. Compared to jet atomization, ultrasonic atomization results in generally smaller reagent droplet sizes under conditions of 20% reagent mass percentage. However, ultrasonic atomization is more sensitive to reagent concentration, with higher concentrations yielding poorer atomization effects.

3.2. Analysis of Solubility of Fatty Acid Collectors in Water: Nebulization vs. Conventional Stirring

Using the dosage of collectors in the flotation process of the beneficiation plant as a reference, solutions containing 200 mg/L were prepared under conditions of deionized water at 288.15 K using jet atomization and mechanical stirring methods, as depicted in Figure 8.

Macroscopically analyzing Figure 8, under conditions where the agent content is consistently 200 mg/L and the liquid temperature is 288.15 K, solutions prepared using atomization exhibit significantly higher turbidity compared to those prepared using conventional stirring. At lower temperatures, the solutions appear transparent, whereas the whitening effect observed with atomization and increased solution temperature is primarily due to the increased solubility of compounds in the liquid. This leads to the formation of numerous micelles or large emulsion particles, enhancing light scattering effects.

Samples were extracted from the same position in 500 mL bottles where 100 mg of the agent was added using both methods. The solubility of fatty acid sodium oleate in water was tested using gas chromatography. When using conventional stirring, the solubility of sodium oleate in the solution was 82.5 mg/L, whereas with atomization, it increased to 142.9 mg/L. These results indicate that atomization enhances the solubility of fatty acid collectors in solutio.

3.3. Analysis of Particle-Bubble Induction Time with Different Reagent Addition Methods

The results of induction time testing between quartz particles and bubbles treated with different collector solutions are shown in Figure 9. After interaction with a solution of 10 mg/L prepared by atomization, the induction time between quartz particles and bubbles was 130 ms, whereas with conventional stirring at the same concentration, it was 150 ms. At a concentration of 30 mg/L, atomization resulted in an induction time of 140 ms, compared to 100 ms with conventional stirring. Similarly, at concentrations of 50 mg/L, atomization led to an induction time of 130 ms, while conventional stirring resulted in 80 ms. For concentrations of 70 mg/L, atomization showed an induction time of 120 ms, whereas conventional stirring had 60 ms. At a concentration of 100 mg/L, the induction time was 90 ms with atomization and 50 ms with conventional stirring.

Experimental results indicate that under the same dosage conditions, the induction time between quartz particles and bubbles is significantly lower with atomization compared to conventional stirring. Both methods show a gradual decrease in induction time between quartz particles and bubbles as the agent concentration increases.

3.4. Flotation Test Results and Discussion

3.4.1. Analysis of Sample Characteristics

Quantitative analysis of the mineral composition in the flotation feed was conducted using BPMA. As shown in

Table 3. Mineral composition and content of flotation feeding.

Name	Iron	Quartz	Fayalite	Hornblende	Carbonates	Actinolite
Content (%)	66.80	23.50	2.15	2.06	1.14	1.84
Name	Mica	Chlorite	Albite	Siderite	Other	Total
Content (%)	0.72	0.64	0.40	0.11	0.65	100.00

, the mass fraction of iron minerals in the flotation feed is 66.8%, with the primary gangue mineral being quartz, followed by fayalite, hornblende, actinolite, and silicate minerals, with mass fractions of 2.15%, 2.06%, 1.84%, and 1.14%, respectively. Additionally, there are small amounts of mica, chlorite, and other minerals.

The particle size analysis of the main minerals, depicted in Figure 10, indicates that the mass fraction of the −53 μm size fraction is 88.76%, the −38 μm size fraction is 79.13%, and the −10 μm size fraction is 32.25%. The sample contains a significant amount of fine particles, accounting for approximately one-third of the total mass. The mass fraction of iron minerals in the −10 μm size fraction is 19.26%, with the majority of iron minerals concentrated in the 5–38 μm range, making up 51.05% of the mass fraction. Quartz is mainly found in the 10–38 μm size fraction; fayalite and hornblende are primarily distributed in the 5–38 μm range, with fayalite being more abundant in the 10–20 μm size fraction and hornblende in the 20–38 μm size fraction.

Quantitative analysis of the liberation characteristics and association relationships of major minerals in the flotation feed was conducted using BPMA. As shown in Figure 11, the mass fraction of free iron minerals in the flotation feed is 59.03%, with a liberation degree of 80–100 and a mass fraction of 34.12%. Iron minerals are mainly associated with fayalite, quartz, and amphibole. For gangue minerals, the mass fraction of free quartz is 73.69%, with a liberation degree of 80–100 and a mass fraction of 15.22%, primarily associated with iron minerals. The mass fractions of free fayalite and siderite are 20.34% and 7.23%, respectively, with liberation degrees of 0–30 and mass fractions of 42.27% and 61.15%, respectively. The mass fractions of free amphibole, actinolite, mica, chlorite, feldspar, and calcite are 60.13%, 78.75%, 76.72%, 77.74%, 94.52%, and 63.89%, respectively. Amphibole is mainly associated with iron minerals, quartz, and fayalite, while actinolite, chlorite, mica, and calcite are primarily associated with iron minerals and quartz. Therefore, in the flotation feed, iron minerals mainly exist in the form of free particles and highly liberated composites, while gangue minerals such as quartz, feldspar, actinolite, chlorite, and mica exhibit a high degree of liberation.

3.4.2. Flotation Performance with Different Reagent Addition Methods

Based on the results of the process mineralogical analysis of the flotation feed, reverse flotation experiments using fatty acid collectors were conducted with a laboratory single-cell flotation machine and a jet pre-mixing system. The study aimed to investigate the effects of different collector addition methods on flotation indices, flotation rates, and reagent consumption. The experimental results are shown in Figure 12 and Figure 13.

Using the laboratory single-cell flotation machine with conventional reagent addition, a rough concentrate with a TFe grade of 61.79% and an iron recovery rate of 64.17% was obtained. Under the same conditions, but with the collector added via atomization, the rough concentrate achieved a TFe grade of 68.14% and an iron recovery rate of 67.36%. Compared to conventional reagent addition, atomized reagent addition improved the TFe grade by 6.35 percentage points and the recovery rate by 3.19 percentage points.

As shown in Figure 13, with the laboratory jet pre-mixing system, conventional collector addition in the mixing tank achieved a concentrate TFe grade of 61.70% and the recovery rate of 93.13% with a flotation duration of 24 min. When the collector dosage was reduced by 20%, atomized collector addition resulted in a concentrate TFe grade of 62.52% and a recovery rate of 93.61% with a flotation duration of 18 min.

The atomized collector addition combined with the jet pre-mixing technology, while maintaining similar TFe grades and iron recovery rates, reduced the flotation time by 25% and decreased collector consumption by 20% compared to conventional reagent addition.

3.4.3. Flotation Kinetics Fitting

The results of the kinetic fitting for reverse flotation using conventional collector addition and atomized collector addition methods are shown in Figure 14. Figure 14a illustrates the fitting results of the flotation test data for the single-cell flotation machine using conventional collector addition; Figure 14b shows the fitting results for the atomized collector addition method. The fitting degrees for both models to the experimental data are r² ≥ 0.95, indicating that both flotation kinetic models demonstrate good fitting performance. Analyzing the flotation rate constant k for the single-cell flotation machine, the conventional collector addition method yields a first-order kinetic model 1 flotation rate constant k of 1.86 × 10⁻², and the atomized collector addition method yields a k value of 2.20 × 10⁻². For the first-order kinetic model 2, the flotation rate constant k for conventional collector addition is 2.88 × 10⁻⁴, while the atomized collector addition yields a k value of 3.18 × 10⁻⁴. The flotation rate constants k fitted by both flotation kinetic models indicate that the flotation rate with atomized collector addition is higher than that with conventional collector addition in the single-cell flotation machine.

The kinetic fitting results of the reverse flotation in the jet pre-mineralization flotation system using conventional collector addition and atomized collector addition methods are shown in Figure 14. Figure 14c illustrates the fitting results of the flotation test data using the conventional collector addition method; Figure 14d shows the fitting results for the atomized collector addition method. The fitting degrees for both models to the experimental data are r² ≥ 0.96, indicating that both flotation kinetic models exhibit good fitting performance.

Analyzing the flotation rate constant k fitting results presented in

Table 4. Fitting parameters of cumulative recovery of gangue in hematite reverse flotation by two kinetic models.

Equipment	Condition	First-Order Kinetic Model 1			First-Order Kinetic Model 2
		r2	r2 (Optimized)	k (s−1)	r2	r2 (Optimized)	k (s−1)
Single tank flotation machine	Direct mixing	0.96	0.95	1.86 × 10−2	0.96	0.95	2.88 × 10−4
	Venturi Atomization	0.96	0.95	2.20 × 10−2	0.95	0.95	3.18 × 10−4
Jet pre-mineralized flotationsystem	Direct mixing 1200 (g/t)	0.97	0.96	1.27 × 10−2	0.97	0.96	4.97 × 10−7
	Atomization 1200 (g/t)	0.99	0.99	4.04 × 10−2	0.99	0.99	7.99 × 10−5

, the classical first-order kinetic model 1 yields a flotation rate constant k of 1.27 × 10⁻² for conventional collector addition and 4.04 × 10⁻² for atomized collector addition. For the first-order kinetic model 2, the flotation rate constant k is 4.97 × 10⁻⁷ for conventional collector addition and 7.99 × 10⁻⁵ for atomized collector addition. Both flotation kinetic models indicate that the flotation rate with atomized collector addition in the jet pre-mineralization flotation system is significantly higher than with conventional collector addition.

3.4.4. Semi-Industrial Flotation Testing and CFD Simulation of the Pre-Mineralization System

A semi-industrial test was conducted on flotation with simultaneous reagent addition and jet pre-mineralization to investigate the influence of various factors, such as feed pressure, collector dosage, and collector addition method, on flotation performance. The test results are presented in

Table 5. Laboratory conventional dosing and atomization dosing collector dosage condition test data.

Equipment	Slurry Pressure (MPa)	Dosing Way	Dosage (g/t)	Mineral	Yield (%)	TFe Grade (%)	Recovery (%)
Cyclonic jet flotation system	0.15	Collector conventional dosing	200	Concentrate	67.02	63.37	84.94
				Tailing	32.98	22.83	15.06
				feed	100.00	50.00	100.00
	0.40	Collector conventional dosing	200	Concentrate	52.78	67.01	70.73
				Tailing	47.22	30.99	29.27
				feed	100.00	50.00	100.00
	0.15	Collector atomization dosing	185	Concentrate	66.47	62.85	83.55
				Tailing	33.53	24.53	16.45
				feed	100.00	50.00	100.00
Industrial on-site rough flotation production indicators	/	Collector conventional dosing Collector	200	Concentrate	64.79	62.50	80.99
				Tailing	35.21	27.00	19.01
				feed	100.00	50.00	100.00

. Under optimal conditions in the semi-industrial test system, particle size screening analysis was performed simultaneously on the test tailings and the rougher tailings from the production flotation workshop. The screening results are shown in Figure 15.

As shown in Table 4, the rougher flotation indices of the flotation workshop achieved a rough concentrate TFe grade of 62.50% and a recovery rate of 80.99%. In the jet pre-mineralization flotation system, using conventional stirring tank collector addition, collector dosage of 200 g/t, and the feed pressure of 0.15 MPa, the flotation indices achieved were a concentrate TFe grade of 63.37% and the iron recovery rate of 84.94%, representing an increase of 0.87 percentage points in TFe grade and 3.95 percentage points in iron recovery compared to the on-site rougher flotation indices. With conventional stirring tank collector addition, a collector dosage of 200 g/t, and a feed pressure of 0.4 MPa, the flotation indices achieved were a concentrate TFe grade of 67.01% and the iron recovery rate of 70.73%, showing an increase of 4.51 percentage points in TFe grade, approaching the TFe grade of the plant’s cleaner concentrate, but a decrease of 10.26 percentage points in iron recovery. Using atomized collector addition, a reagent dosage of 185 g/t, and a feed pressure of 0.15 MPa, the flotation indices achieved were a concentrate TFe grade of 62.85% and the iron recovery rate of 83.55%, which is close to the rougher concentrate indices but with a 7.5 percentage point reduction in collector dosage. In summary, increasing the feed pressure in the jet pre-mineralization flotation system can improve the concentrate TFe grade but may result in a loss of iron recovery. The technology of simultaneous collector addition with atomization in the jet pre-mineralization system can effectively enhance flotation performance and reduce collector consumption under similar conditions to the on-site rougher flotation indices.

As shown in Figure 15, under the conditions of atomized collector addition with a dosage of 185 g/t and a jet pre-mineralization feed pressure of 0.15 MPa, the content of −0.038 mm particles in the flotation tailings was 54.63%. At the same time, the content of −0.038 mm particles in the on-site rougher tailings was 40.97%, showing a 13.66 percentage point decrease compared to the atomized collector addition and simultaneous pre-mineralization flotation test results. These results indicate that the atomized reagent addition and simultaneous pre-mineralization technology has superior flotation performance for fine-grained minerals compared to conventional mechanical agitation flotation machines used on-site.

The radial velocity vectors of the gas-liquid two-phase flow inside the jet pre-mineralization device are shown in Figure 16a. Radial cross-section one is aligned with the nozzle, and the distance between sections is 200 mm. The simulation parameters were based on semi-industrial test settings, with an inlet gas velocity of 0.63 m/s and a slurry velocity of 0.25 m/s. According to the simulation results, due to the difference in diameters between the nozzle and the mineralization tube, the slurry jet creates a negative pressure, increasing the gas velocity from 0.63 m/s to 2 m/s at cross-section one. The axial velocity vectors of the gas-liquid two-phase flow inside the device are shown in Figure 16b. The slurry is injected into the pre-mineralization device at a velocity of 6.5 m/s, forming a circular backflow within the 200–400 mm range. The velocity vector at cross-section two of the mineralization tube aligns with Figure 16b, where the central flow field velocity is higher and directed downward, while the peripheral velocity is lower and directed upward. The flow field direction at cross-section three is downward, with velocities generally below 0.2 m/s. The axial velocity vector diagram indicates that the jet slurry velocity gradually decreases as it flows downward, transitioning from turbulent to laminar flow, which aligns with the mineral flotation process principle of strong turbulent mineralization followed by weak turbulent separation. The simulation results of the internal turbulence intensity distribution under optimal industrial test conditions for the pre-mineralization device are shown in Figure 16c. Under optimal feed pressure conditions, the strong turbulent mineralization region within the pre-mineralization tube is mainly within the 0–350 mm range from the nozzle. Below 350 mm, the flow gradually transitions from weak turbulence to laminar flow, with gas-liquid velocities gradually decreasing. Ultimately, low-speed stabilized mineralized bubbles are fed into the flotation cell to achieve mineral separation.

4. Conclusions

• As the collector mass percentage increases, the particle size of the atomized collector progressively decreases. Specifically, at a collector mass percentage of 20%, the D99 particle size for jet atomization is 27.7 μm, while for ultrasonic atomization it is 12.4 μm.
• The atomization method enhances the solubility of fatty acid collectors in the solution. Under identical collector dosage conditions, the solubility of sodium oleate with conventional stirring is 82.5 mg/L, whereas the solubility achieved through atomization is 142.9 mg/L.
• The induction time between quartz particles and bubbles is significantly shorter with atomization compared to conventional stirring. Furthermore, the induction time decreases with increasing collector concentration.
• Flotation test results indicate that the jet pre-mineralization technology with atomized collector dosing can effectively reduce collector dosage, accelerate flotation rate, enhance mineralization, and improve separation indicators.