There are still many problems in the stirring dissolution of flocculants: The law of stirring dissolution of flocculants with different molecular weights is not clear, the microstructure of settling floc with different particle sizes of coal slime is still to be explored, and how to apply the law of flocculant dissolution to industrialization? To solve these problems, firstly, mechanical stirring dissolution tests are carried out on anionic polyacrylamide (APAM) with different molecular weights to explore the stirring dissolution law of APAM with 3–25 million molecular weights. Results indicated that the optimal stirring speed of APAM with 3–6 million molecular weight is 800 r/min. The optimal stirring speed of 8–16 million molecular weight APAM is 600 r/min. The optimal stirring speed of 18–25 million molecular weight APAM is 800 r/min. The stirring power formula for APAM dissolution is improved by fitting the experimental data of 3–25 million molecular weight APAM stirring dissolution. Secondly, through APAM performance test, it is verified that the solubility of powdered APAM is the best under optimal solution. Thirdly, through the image measurement and analysis test of settling floc of coal slime, the change law of equivalent diameter of settling floc of different particle sizes of coal slime under the optimal dissolution parameters are explored. Results showed that when the mixing speed is 600 r/min, the equivalent diameter of −0.5 mm slime settling floc is the largest. When the mixing speed is 200 r/min or 400 r/min, the equivalent diameters of 0.5–0.25 mm, 0.25–0.125 mm, 0.125–0.075 mm, 0.075–0.045 mm and −0.045 mm slime settling floc are the largest. The equivalent diameter is positively correlated with the size of slime, and the equivalent diameter of −0.045 mm slime settling floc is the largest. The size of slime is the dominant factor in the change of fractal dimension. The fractal dimension of −0.5 mm slime settling floc is the largest, and the fractal dimension is little affected by mixing speed. Finally, the relationship between the important dissolution parameters of the APAM stirring dissolution test is numerically fitted. In view of the different geometrical parameters of the stirring barrel, a method of deducing the dissolution and stirring time of industrial flocculants is proposed.

The jet flow field is characterized by the dispersion and mixing of multiphase flow, which is widely used in the field of coal slime flotation. In this paper, the behavior of coal slime surface modification, the behavior of material suspension and the effect of different jet fluids on coal slurry blending were studied. Based on the action mechanism of the jet flow field, a jet device suitable for coal slime graded mixing was proposed, and the mixing effect of the jet device was tested. The results show that the jet flow field has strong effects on material dissociation and dispersion, and the mixing effect of a single jet is equivalent to that of the laser particle size analyzer’s own agitation device after stirring for 2.5 min at 500 r/min speed. The SEM test of material surface morphology and the changes of Al and Si elements measured by EDS show that the jet flow field can effectively remove the fine mud wrapped on the surface of coal particles. The precondition of material suspension is to have the just-suspended capacity. The critical jet velocity of coal slime suspension is in the range of 6 m/s~9 m/s. The mixing ability of the jet stream has certain limitations. The increase or decrease of the jet height will cause the decrease of the suspension percentage of sampling points in the tank. The gas jet mode can promote the reagent acting on the surface of the bubble liquid film to form oil bubbles, which is more suitable for hydrophobic mineral flotation. The optimal speed of the gas jet is 0.86 m/s, and the shortest cycle period is 1.0 T (T is one material cycle period). The flotation perfection index of 0.5–0.25 mm and less than 0.075 mm coal slime increased by 2.67% and 26.78%, respectively, indicating that the overall idea of the jet mixing device proposed based on the experimental conclusion is feasible.

The parameters of jet mixing devices have an important influence on the mixing process, particle movement and interface regulation. At present, jet mixing devices are widely used in the coal slime flotation field, and their variable parameters lack systematic optimization. In this paper, the performance of reagent mixing and the distribution characteristics of flow field are taken as the evaluation indexes, and computational fluid dynamics (CFD) software (FLUENT) is used to optimize the variable parameters of the device. The results show that when the area ratio $A_r=1.96~3.24$, the throat-nozzle distance $L_e=0.2D_h~0.6D_h$, the suction tube is located 1/4~1/2 $L_z$ to the left of the nozzle outlet and is symmetrically arranged, the length of the throat tube $L$ is from 6$D_z$ to 12$D_z$, the mixing performance of the jet mixing device was optimal. The flow field distribution characteristics showed that the area ratio has a more significant effect. The larger the area ratio is, the more favorable the mixing of the working fluid and the injection fluid is. The throat-nozzle distance has little effect on the flow field distribution, and its optimal value ranges from 0.3$D_h$ to 0.6$D_h$. The fog droplet size test showed that the dispersion effect was the best when the area ratio $A_r=3.24$. The diameter size test of the injected bubbles was carried out to verify the performance of the jet mixing device after parameter optimization. The experimental results and the simulation results confirm each other, which proves the correctness of the numerical simulation results.

The precise identification of damp, sticky coal gangue; efficient jet nozzle separation; and process layout in a narrow, restricted space are essential technologies for gangue source reduction based on underground gangue photoelectric separation, which is critical for the long-term growth of coal mines. In this paper, the X-ray absorption fine structure (XAFS) method was used to identify the X-ray absorption law of different atoms in coal-based minerals and explore the differences in the microscopic crystal properties of coal gangue; the numerical simulation calculation of four commonly used nozzles—namely, flat, convergent, flat–convergent, and streamline—was carried out using Fluent software for coal gangue jet separation to optimize the nozzle morphology and parameters. The technical characteristics of the underground layout of the photoelectric separation system for coal gangue were expounded, and the technological layout of the separation system was explored. The results showed that the absorption coefficients μ(E) of Al and Si atoms in minerals to X-rays are significantly different, and the XAFS method has the ability to identify coal, gangue, and other minerals. The streamlined nozzle has a long jet core area, slow decay of jet velocity, low gas consumption per unit time, and better performance than the other three types of nozzles. Based on the development and mining system of the Renjiazhuang Coal Mine, three kinds of photoelectric separation system layout schemes of coal gangue were designed, namely centralized layout, distributed layout, and mobile layout. The advantages and disadvantages of each scheme were compared, which enriched the technical means of gangue source reduction.

The high-ash tailings produced by flotation contains a large number of minerals that can be recycled. However, as the separation and purification technology for flotation tailings is not mature and separation efficiencies are low, it is generally treated as separation waste, resulting in the waste of mineral resources. In view of this phenomenon, the particle size composition and density composition of high-ash minerals in flotation tailings of coal slime as well as the type and content of mineral elements were measured. It was determined that the main mineral composition is quartz, and there is also a certain amount of chlorite (silicate mineral). A self-spinning hydrocyclone used for flotation tailings separation and purification was designed, and numerical simulation was carried out by fluent software. The internal flow field-, tangential velocity-, and axial velocity-distribution characteristics of the hydrocyclone at different rotational speeds were investigated. The physical model of the hydrocyclone was set up and the separation efficiency improvement test of fine particles was carried out. The results show that the overflow yield of −0.045 mm particles increased gradually with the increase in cylinder rotation speed. When the rotation speed increased to 900 r/min, the overflow yield of −0.045 mm particles can reach more than 90%, which can effectively realize the material classification according to 0.045 mm.