With sodium oxalate and D401 chelating resin as impurity removal materials, impurities of calcium and magnesium in crude lithium solution were removed by adopting a process consisting of chemical precipitation and ion exchange. In an experiment, reaction was firstly run at 25 ℃ for 60 min by adding sodium oxalate at an amount of 17.6 times the theoretical value, with pH of 6.5 and stirring rate of 300 r/min. And then, the lithium solution after filtration flowed through a resin column at a rate of 8 BV/h. As a result, the removal rates of calcium and magnesium reached 98.21% and 83.36%, respectively, and the lithium loss rate was 5.34%. The purified lithium solution was then recrystallized and purified, and the obtained lithium phosphate powder, with regular morphology and uniform dispersion, has its purity higher than 99.5%.

The motion of spherical, tetrahedral and hexahedral particles flowing in a vertical pipe under different working conditions was simulated by using computational fluid dynamics-discrete element method (CFD-DEM), and the motion of irregular particles flowing in a vertical pipe was obtained. Based on comparison of local concentration and local flow rate, it is found that with lower flow rate at the inlet, the shape of particles can bring a larger influence to local concentration; while with a higher feed concentration and lower inlet flow rate, the shape of particles can bring obvious influence to local flow rate.

An experiment on non-quenched and tempered steel F45MnVS was carried out by adopting controlled cooling after hot rolling. The mechanical properties, decarburized layer and microstructure of rolled steel without cooling and after controlled cooling process were compared for analysis. The results show that controlled cooling after hot rolling can lead to the steel with yield strength, elongation, section shrinkage and impact energy improved all, and with the decarburized layer being effectively controlled or even "disappeared". With the surface temperature of the hot-rolled steel decreased to 650 ℃, granular bainite begins to occur on the steel surface; with the surface temperature down to 460 ℃, much granular bainite occurs on the steel surface. It is shown that by using controlled cooling after hot rolling, the ferrite and pearlite on the steel surface and near 1/2 radius on the cross section of the steel become fine-grained. The total ferrite net is reduced, and long strip ferrite is transformed to blocky ferrite. Due to larger size, the central part of steel shows little difference in the microstructure.

As for a cobalt-containing raffinate in Africa, several neutralizing agents, including limestone, lime, limestone-lime, as well as a combination of flotation tailings and lime, were separately used for impurity removal in the study, and a preliminary economic evaluation was also conducted. It is found that a combination of flotation tailings and lime is a good choice for impurity removal by neutralization, which can not only save the usage of limestone, but also recover part of the copper and cobalt in flotation tailings. Using this process, the leaching rates of copper and cobalt from flotation tailings can reach 81.69% and 41.10%, respectively. After an addition of lime, the precipitation rates of copper and cobalt can reach 95.43% and 13.64% respectively, and the iron removal rate is up to 99.86%.

Based on the study of process mineralogical properties and grindability of an iron ore from Australia, experiments were carried out to explore its beneficiability. The results show that this kind of ore has a TFe grade of 34.90%, with magnetite and hematite as the dominant Fe-containing minerals, and quartz as its dominant gangue mineral. The ore is medium hard, with a protodyakonov coefficient of 3.13, and also comparatively hard to mill, with a Bond ball milling work index of 13.27 kW·h/t. On this basis, a flowsheet consisting of sequentially primary grinding, a roughing process of low-intensity magnetic separation (LIMS), secondary grinding and a cleaning process of LIMS was adopted in an experiment, producing an iron concentrate grading 65.45% TFe at 65.98% recovery, with mFe recovery of 95.69%. After intensified grinding, the iron concentrate was subjected to further magnetic separation, resulting in ultrapure iron concentrate grading 71.90% TFe at 60.20% recovery. Meanwhile, the middlings was subjected to a scavenging, and a super-high grade iron concentrate with TFe grade of 69.87% was obtained with recovery of 35.21%, indicating that this ore has a good beneficiability.

A lead-zinc deposit is rich in valuable metals of gold and silver. In order to improve the economic benefits of products, the associated gold and silver should be enriched in lead concentrate to the maximum extent. Based on the actual situation in the production, the distribution of associated gold and silver in the products after mineral processing was ascertained, and then optimization tests were perform. The results showed that most of the associated gold and silver were concentrated in the lead concentrate, and the recovery of gold and silver was positively correlated with the recovery of lead. Without altering the original reagent regime for lead flotation, ethyl xanthate was introduced as an auxiliary collector in a close-circuit test adopting a flowsheet consisting of one stage of roughing, two stages of cleaning and two stages of scavenging. And the obtained lead concentrate with grade around 50% can have a high enrichment of gold and silver and a low content of zinc. It is concluded that gold and silver resources can be comprehensively recovered, which can bring in the maximized economic benefit.

The upper middle section in the West 2^#Mining Area of Jinchuan Longshou Mine, with the mining method changed from underhand cut-and-fill mining to sublevel caving without sill pillar, was taken as an example for studying extraction of the orebody in a confined space from sublevels of stope. A combined scheme was prepared with different ore-drawing method for each sublevel. As for the first and second sublevels, the total amount of mined ore in the ore drawing is controlled to ensure the safe caving of roof and forming of overburden. And ore drawing by controlling ore dilution is adopted for the third sublevel for avoiding ineffective dilution, so as to achieve high-quality ore recovery. For the fourth sublevel, a scheme of ore drawing by controlling ore dilution in the normal stope drift plus ore-drawing by controlling cutoff grade in an auxiliary extraction drift is designed to achieve a full and effective ore recovery. Experiments were then performed with three groups of different ore-drawing schemes, and results show that a combined ore-drawing scheme can achieve safe and effective mining of orebody in a confined space, but also has a significant advantage in controlling loss and dilution of ores, which can bring the mine good economic benefit from mining. It is concluded that this research can provide scientific theory and technical guidance for the following engineering practice.

By establishing a particle flow model of geological profile with discrete element software PFC^2D, the formation and development process of overlying strata cracks during the mining of ore body were studied, and the mechanism for overlying strata gradually developing into collapse and caving was also revealed. It is found that with the mining of ore bodies, fractures grow upward and increase in numbers. The goaf after mining can cause the overlying strata with tensile-shear failure, and also the new cracks will constantly occur in the strata. Tensile fractures predominantly develop in the overlying strata, but tensile fractures occur at the both ends of fracture development region. Also, more and more concentrated fractures grow upward at both ends of goaf, presenting a potential of gradual collapse and caving of goaf roof. After the third and fourth stratified ore bodies are mined out, roof collapse will take place locally and then gradually develop into roof caving of the whole goaf, finally leading to roof collapse to the surface and forming a small sinkhole on the ground surface. Then, the development progress of sinkholes can be subdivided into stable stage, slow-progress stage, rapid-progress stage and end of progress in terms of the numbers of fractures, presenting the mechanism for overlying strata developing from tensile fracture and shear fractures at both ends of goaf to overall collapse.

Pure quartz and pyrite minerals in the size range of 5-30 μm were taken in an experiment on viscosity under different pulp temperature and concentration conditions, for investigating the viscosity variation law of ultrafine particles. The results show that the viscosity for both minerals within the same size range increases along with the increase of pulp concentration, and the finer the particle, the greater the increasing rate. Furthermore, the viscosity variation of quartz is more remarkable．With the same pulp concentration, the viscosity of both minerals displays a declining-ascending trend as the temperature rises, which is more significant for finer minerals. The regression analysis shows that the correlation between viscosity and concentration of quartz and pyrite slurry are in line with the exponential fitting model. According to this analysis, the pulp concentration for ultrafine grinding should not exceed 40% and the optimum pulp temperature should be regulated at 50 ℃, which is beneficial for improving grinding efficiency.

Based on the analysis of existence forms of molybdenum and iron ions in acidic solution with different pH, the solvent extraction processes available for separating molybdenum from iron were classified, for which the principles, effects, advantages and disadvantages were also discussed in detail. Moreover, the potential development trend of the solvent extraction for molybdenum and iron separation in the future is prospected, thus providing ideas for the research and development of a green and efficient process for separating molybdenum and iron from acidic solutions.