Flash flotation technique was introduced to an experiment to recover crystalline graphite. The influence of impeller speed, superficial aeration rate and foam layer thickness on the flash flotation indices of graphite was investigated. The results show that flotation with impeller speed of 750 r/min, superficial aeration rate of 0.3 m³/(m²·min) and foam layer thickness of 20 mm can bring a better flotation performance of graphite. According to the particle size analysis and microscopic observation analysis of concentrate, the flash flotation displays good recovery of the graphite in a particle size range of 0.074-0.180 mm, which is dominated by flake graphite monomer and rich intergrowth. As the flash flotation technique favors the collection of useful minerals from the classification underflow in advance, the probability of overgrinding can be reduced and the flake morphology can be therewith reserved. Therefore, flash flotation technique is expected to be commercially applied in the flotation recovery of crystalline graphite.

A low-grade high-sulfur copper ore from Anhui Province has a sulfur grade of 41.30% and a copper grade of 0.53%. It is difficult to control the flotation index of this easy-to-oxidize ore. To improve the Cu/S separation effect, the influence of grinding fineness, reagent type and reagent dosage on copper flotation index was investigated. A closed-circuitflotation process including one stage of roughing, two stages of cleaning and two stages of scavenging was adopted to treat the ore with a grinding fineness of 83.88% -0.074 mm, with CaO and Na₂S as a combined depressant, Z-200 as the collector and terpenic oil as the frother. It is found that a copper concentrate grading 15.27% Cu at 80.96% recovery can be obtained. This experimental study can provide a reference for flotation separation of copper from low-grade high-sulfur copper ore.

With the coal tailings from the flotation process of a coking coal preparation plant in Guizhou as the research object, the effects of four kinds of frother including methyl isobutyl methanol (MIBC), sec-octyl alcohol, terpenic oil and n-pentanol on the flotation performance of coal tailings were investigated. The test shows that the flotation indices of MIBC frother were better than those of the other three frothers with the similar dosage. A flotation process consisting of one stage of roughing, one stage of cleaning and one stage of scavenging was adopted to treat the raw coal with the ash content of 56.90%, and with dosages of kerosene and MIBC respectively at 1 000 g/t and 350 g/t, a qualified coking coal with the ash content of 11.47% and the yield of 32.03% can be produced. The results of foaming ability and foam stability measured by inflation method show that the foaming ability and foam stability of terpenic oil are the strongest, while those indices of n-pentanol are relatively weak, and those of MIBC and sec-octyl alcohol moderate. The characterization of the adhesion process between bubbles and coal particles under the action of different frothers analyzed with bubble-particle encapsulation angle and induction time measuring instrument suggests that MIBC can enhance coal-carrying capacity of bubbles, shorten particle-bubble induction time, thus bringing improved flotation effect.

A mineral processing test was conducted to treat a low-grade rubidium-bearing lepidolite ore from Hunan Province with the grade of Li₂O and Rb₂O respectively at 0.27% and 0.17%. A flowsheet including a desulphurization and a lithium flotation was adopted, and an efficient collector CK was used in combination with dodecylamine to collect lithium minerals under weak alkaline conditions. In a closed-circuit test, a lithium concentrate was produced with Li₂O grade and recovery of 2.71% and 86.34%, Rb₂O grade and recovery of 1.02% and 51.24%, respectively. It is concluded that efficient utilization of low-grade lepidolite ore can be actualized.

A mineral processing test was conducted to treat a lithium-tantalum-niobium-beryllium polymetallic ore with a lithium grade of 0.68% from Xinjiang. According to the process mineralogy study, this ore has spodumene as the dominant lithium minerals, and has low content of tantalum-niobium minerals. A flowsheet including a magnetic separation and gravity separation to recover tantalum-niobium minerals, and a flotation to collect lithium minerals can produce a tantalum-niobium concentrate with Ta₂O₅ grade and recovery of 17.110% and 41.69%, Nb₂O₅ grade and recovery of 19.670% and 42.63%, respectively, and a lithium concentrate with Li₂O grade and recovery of 5.12% and 75.21%, respectively.

To recover the copper resource therein, mineral processing of a slag-beneficiated copper sulfide ore from Congo (Kinshasa) with 9.62% Cu was investigated. A regrinding and reseparation flotation process was proposed based on multi-element chemical analysis and mineral occurrence analysis. It is found that with this process, a copper concentrates with Cu grade of 25.16% and Cu recovery of 90.67% can be collected.

In order to optimize the particle shape and gradation of machine-made sand, a vertical bar stirring mill was adopted for shaping tests. The effects of medium type, medium ratio, mill rotation speed and material/ball ratio on the particle shape of machine-made sand were investigated. The gradation and shape characteristics of unshaped and shaped sands were comparatively analyzed by using optical microscopy and image processing software. The results show that the shaping effect of zirconia medium is better than that of steel or alumina medium. With the zirconia balls with diameter of 6 mm and 8 mm in a mass ratio of 1∶1, rotation speed of 300 r/min, feed/ball mass ratio of 1∶3 and pulp volume fraction of 62.5%, the milling process results in the shaped sand with fineness of+0.15 mm 84.98% and flake granule accounting for 4.5%. The shaped machine-made sand has better compactness and angular characteristics, and it is qualified as the type I sand according to the standard GB/T 14684—2022, with better gradation and particle shape compared to the unshaped sand. The contour shape and angular characteristics of coarse granules can be greatly optimized than those of fine particles. It is concluded that under suitable conditions, a vertical bar stirring mill can obviously improve the shape of machine-made sand and optimize coarser grain composition.

The basic flow of Midrex and HYL/Energiron technologies for direct reduction in a shaft furnace and the direct reduced iron output by each processing technique in recent years are firstly introduced, and then the equipment, raw materials and process characteristics of those two technologies are analyzed based on comparison. Based on the expounding of technical R&D and investment of global steel companies in these two technologies, it is pointed out that the development of hydrogen-based direct reduction process in a shaft furnace is closely related to grade of pellet ore, heat adsorption during hydrogen-based reduction reaction process, technologies for large-scale green hydrogen production and production cost among others. It is important for sustainable development of Chinese iron and steel industry to adopt hydrogen-based direct reduction in a shaft furnace that conforms to the national conditions.

In order to identify the feasibility of preparing alkaline pellets with low-quality magnesium-containing flux, experiments on pelletizing, preheating and roasting were carried out. Three kinds of magnesium-containing flux from Wulongquan Mine of WISCO Resources Group Co., Ltd., including interbedded dolomite, light-burnt material and lightburnt dolomite, were taken for pelletizing, and then effects of different magnesia flux and the adding amount on pelleting, as well as following preheating and roasting processes of alkaline pellet were all explored. The results show that the green ball prepared with the flux of interbedded dolomite presents superior performance. It is found that with alkalinity of 0.8, the green ball prepared with two different blending schemes have drop number of 4.1 and 6.6 respectively from height of 0.5 m, and compressive strength of 20.3 N/pellet and 22.3 N/pellet respectively. By increasing the addition of magnesia flux in two blending schemes, both preheated balls and roasted balls have their strength decreased after an initial improvement. With alkalinity between 0.6 and 0.8, the prepared pellet can have compressive strength of 2 620 N/pellet and 2 963 N/pellet respectively after preheating and roasting process. It is recommended that with interbedded dolomite and light-burnt material as magnesia flux, the alkaline magnesium-containing pellet prepared with alkalinity of 0.6-0.8 can meet industrial requirements.

A method of selective adsorption and recovery of gold from waste thiourea liquid with biomass-based adsorbent prepared from phyllostachys pubescens was proposed. The charcoal, after being activated in H₂O-CO₂ atmosphere, has more nanopores with smaller size on its surface, compared to being activated by CO₂ alone, which greatly increases the specific surface area of the adsorbent material. Based on exploration of the effects of factors, including type of adsorbent material, pH value, adsorbent dosage, adsorption temperature, and adsorption time, on the adsorption of gold in waste thiourea liquid, the appropriate adsorption conditions were obtained as follows: pH of 6, adsorbent dosage of 8 g/L, adsorption temperature of 25 ℃, and adsorption time of 3.5 h. It is found that activation in H₂O-CO₂ can bring the activated carbon with better adsorption effect, and the removal rate of gold from waste thiourea liquid by adsorption can exceed 96%. The adsorption isothermal model is used to fit the process of gold adsorption from waste thiourea liquid by the carbon activated in H₂O-CO₂ atmosphere, and the results show that such gold adsorption process follows Freundlich model and is a physical adsorption process.