A numerical simulation model was established with Fluent software to analyze the disturbance effect of a subsea collector vehicle on seabed sediments, and the generation mechanism of seabed sediment plumes was analyzed. A large-scale tank experiment on diffusion of sediment plume was conducted to investigate the morphological characteristics and concentration variation rule of sediment plume under different initial mass concentrations. The results show that seabed sediment plumes are created mainly by the disturbance due to the movement of a collector vehicle. The overall morphological characteristics of such sediment plume under different discharge concentrations are roughly similar, and the diffusion of sediment plumes can undergo three stages: initial discharge, primary settlement and diffusion, and re-settlement and diffusion. The plume concentration also varies in the following three steps: rapid rise, rapid decline, and slow decline before stabilization.

For the southern area of the Shahe Zhongguan Iron Mine of Hebei Iron and Steel Group in the study, a stability calculation model for the drifting chamber pillars was constructed based on Platts theory of ground pressure and the Kastner Formula. The influence of various factors on the roof stability of the drifting chamber during sublevel open stoping with backfill was discussed, and the roof stability in two options: no pillars retained in the drifting chamber (Option 1) and pillars initially retained and subsequently caved along with the orebody (Option 2) were analyzed by numerical simulations. The results show that when the stope length ranges from 27 m to 45 m, the drifting chamber roof in Option 2 faces a higher risk of instability. With a stope length over 45 m, the roofs in both options are at risk of instability. Option 2 leads to stress concentration within the drifting chamber, with accelerated stress release observed in the roof and side walls. In contrast, Option 1 demonstrates more stable stress release and distribution in the drifting chamber, with a relatively delayed failure time. When the ore rock exhibits poor stability, Option 1 is more conducive to maintaining roof stability.

By means of computational fluid dynamics simulation technology, the particle flow behavior in a XFD flotation machine was simulated with Euler's method, and the effects of impeller speed and particle size on the distribution characteristics in a solid-liquid two-phase flow field were explored to reveal fluid motion behavior in the flotation machine. The flotation kinetics of the flotation machine was also explored in terms of velocity field and turbulence intensity. The simulation results show that with a rotating speed at 1 800 r/min, the liquid-phase flow moves at a maximum speed of 5.32 m/s, and the fluid motion velocity and kinetic energy of turbulent are higher in the rotor zone and the lower circulation zone. The flow field is relatively stable, which is suitable for mineral flotation separation. The particle size of fine-grained minerals has a minor influence on the solid-liquid two-phase flow characteristics in the flotation machine, and the pressure distribution of the rotor surface is closely related to the particle size. It is found that the kinetic energy of turbulent is significantly enhanced in the region between the stator and rotor, which can effectively promote the dispersion of hematite particles. In a hematite flotation test, the variation in concentrate grade and recovery obtained with different rotation speed of impellers was studied. It is shown that with impeller rotating at a speed of 1 800 r/min, an iron concentrate with Fe grade of 66.35% and recovery of 85.34% can be produced. Based on the simulation of flow field of flotation machine, it is concluded that an impeller with a rotating speed of 1 800 r/m is suitable for flotation operation.

Aiming at the Mo-Bi-S bulk concentrate from Hunan Shizhuyuan Nonferrous Metals Limited Company, a green, environmentally-friendly and efficient depressant (CYZ-15) and a new cyanide-free processing technique for Mo-Bi-S separation were developed. An experiment with the developed flowsheet produced a molybdenum concentrate grading 40.36% Mo at 92.98% recovery with a yield of 3.02%, and a bismuth concentrate grading 28.14% Bi at 95.64% recovery with a yield of 9.62%. It is shown that cyanide-free and efficient separation of Mo-Bi-S bulk concentrate can be actualized.

A processing technique consisting of flotation, low-intensity magnetic separation (LIMS) and high-intensity magnetic separation (HIMS) was proposed for recycling blast furnace dust. With kerosene as a collector and zinc sulfate as a depressant, a flotation process consisting of one roughing and two cleaning was adopted firstly for decarbonization. Then, the obtained tailings were processed by LIMS followed by HIMS to obtain an iron concentrate, and the zinc concentrate was produced as the magnetic separation tailings. The full flowsheet test produced a carbon concentrate grading 86.16% C at 88.74% recovery, an iron concentrate (LIMS concentrate) grading 55.75% Fe at 67.01% recovery, and a zinc concentrate grading 16.79% Zn at 75.74% recovery. The migration patterns of main elements during the whole separation process were analyzed by using XRD and SEM-EDS. It is found that iron concentrate is mainly magnetite, and zinc concentrate is mainly zinc oxide. The lost zinc minerals left in the iron concentrate are mostly ZnFe₂O₄ in dispersed distribution. Besides, some processing technique and product schemes are also proposed for the obtained difficult-to-treat HIMS concentrate.

A refractory ore characterized by ultra-fine gold particles disseminated therein was taken for flotation test. A technique of re-grinding and re-flotation of the middlings, together with the self-developed collector of ZHS-3, was adopted to enhance the collection of fine-grained gold, resulting in a gold concentrate grading 43.70 g/t Au at 74.29% recovery, and a secondary concentrate grading 15.60 g/t Au at 4.28% recovery. Two obtained products had a total gold grade of 39.79 g/t and recovery of 78.57%. It is shown that both gold grade and recovery are improved compared with conventional flotation processes. This processing technique can achieve efficient recovery of fine-grained gold, thus improving resource utilization.

A novel low-temperature collector was adopted in the reverse flotation of Qidashan iron ore. Based on a reverse flotation condition test at low temperature, closed-circuit reverse flotation tests at room temperature and low temperature, as well as the study on the mineral adsorption mechanism, it is found that under conditions including pulp temperature at 10 ℃, pH of 11.0, caustic starch as a depressor at an amount of 600 g/t, CaO as an activator at an amount of 750 g/t, CH collector at an amount of 1 050 g/t, and pulp density of 30%, the reverse flotation consisting of one stage of roughing and one stage of cleaning can produce an iron concentrate grading 68.32% Fe at 70.76% recovery；the closed-circuit tests by adopting a process consisting of one stage of roughing, one stage of cleaning and three stages of scavenging at 10 ℃ can yield an iron concentrate grading 66.32% Fe at 85.14% recovery；while the close-circuit test at room temperature (25 ℃) results in 85.45% Fe recovery into an iron concentrate grading 67.31% Fe. It has proven that CH collector can bring good flotation effect at low temperatures. Infrared spectroscopy analysis, quartz contact angle testing and surface tension measurements indicate that CH collector has a stronger adsorption on quartz surfaces compared to traditional anionic collector sodium oleate.

The effects of common depressants, including calcium oxide and calcium polysulfide, on the surface zeta potential of marmatite were studied by using dry grinding, and the influence of active ions such as Cu²⁺, Pb²⁺ and Ag⁺ on the surface atomic composition and chemical state of marcasite was explored by using XPS. It is found that after depression by calcium oxide and calcium polysulfide, the marmatite has its surface zeta potential shifted to varying degrees. After the marmatite interacts with calcium oxide, its surface zeta potential shifts positively, with point of zero charge at pH of 6.43；after the marmatite interacts with calcium polysulfide, its surface zeta potential shifts negatively at low amplitude. Both calcium oxide and calcium polysulfide exhibit weak depression for marmatite. After activation by ions like Cu²⁺, Pb²⁺ and Ag⁺, the marmatite has sulfur atoms and metallic atoms on the surface at a ratio of 2.07, 1.34 and 1.07, respectively, all higher than the theoretical value (1.0) of sphalerite. Due to Cu²⁺ with its ionic radius similar to Zn²⁺ and Fe²⁺, facilitating strong ion substitution, marmatite presents a metal-deficient mineral phase on the surface, being bound to the surface S^2-；while Pb²⁺ and Ag⁺ have their ionic radius quite different from Zn²⁺ and Fe²⁺, which can alter the surface phase composition of marmatite by adsorption and precipitation, but bring less impact to the ratio of sulfur and metallic atoms. As a result, polysulfides and sulfates exist on the surface of marmatite.

To address issues such as land occupation and environmental hazards caused by stockpiling residues that are left after vanadium extraction from stone-like coal in the Western Hunan, a resource utilization scheme involving deep separation of carbon and ash was proposed. Firstly, coarse-grained minerals with ash content more than 94% were obtained by sieving, and the fine-grained undersize minerals were then subjected to flotation. A closed-circuit flotation test produced a concentrate with fixed carbon content of 32.86% and a higher heating value of 9 832 kJ/kg, which could meet the calorific requirement for the coal added in boilers. The recovery of combustible matter was 73.50%, while the obtained tailings had an ash content of 96.14%, with a yield of 78.42%, and the loss on ignition was 4.98%. The toxicity test confirmed that hazardous components in the high-ash tailings did not exceed limits. Based on preliminary economic estimates, it is concluded that this technical approach is economically feasible.

Experiments were performed to study the effect of quaternary ammonium salt Y28, as a collector, on the flotation performance of diaspore and gangue silicate minerals of kaolinite and muscovite, and the interaction mechanism between Y28 and the surface of minerals was also explored by analyzing adsorption capacity, contact angle, zeta potential, FTIR analysis and XPS analysis. The results show that with the collector Y28 at a dosage of 90 mg/L and pulp pH of 7, the recoveries of diaspore, kaolinite and muscovite were 25.63%, 83.21% and 81.24%, respectively. The collector Y28 is primarily adsorbed onto the surface of the minerals by physical adsorption, with the adsorption strength in the following descending order: kaolinite>muscovite>diaspore.