A vertical stirring mill was introduced for regrinding the graphite concentrate from the rougher in a graphite mine of Heilongjiang Province. Using ceramic ball as the grinding medium, the influences of processing parameters, including rotation speed of mill, diameter of medium ball and grinding time, on the grinding and flotation performances of graphite ore were investigated. The graphite ore was beneficiated adopting an open-circuit flotation process after it was milled with the optimized grinding parameters including alternating (slow-fast-slow) rotation speed, medium ball diameter of 8-10 mm and grinding time of 5 min. The as-obtained graphite concentrate, with the 24.51% in a size fraction of -0.045 mm, has a fixed carbon content of 95.83% and large-flake graphite content of 14.27%.

To study the effects of welding parameters on the tolerance of friction stir welding (FSW) of dissimilar aluminum alloys, the mechanical properties and structure of joint of dissimilar aluminum alloys (A356 and AA6061) by FSW under different welding parameters were studied by means of micro-hardness testing, tensile mechanical properties testing, scanning electron microscopy among other analytical testing means. The results show that as for the workpieces with the gap from 0 mm to 1 mm, the welded joint has tensile strength decreased significantly and presents visible welding defects. With tool pin of the same specification, the material flow can be promoted by decreasing the welding speed from 120 mm/min to 80 mm/min, thus the tolerance of workpiece gap will be greatly improved. The tool pin with diameter increased from 4 mm to 6 mm can lead to higher tolerance for welding, but also the material with a higher fusion degree and without delamination.

In order to simply and effectively evaluate slope stability, four machine learning models based on chaotic particle swarm optimization (CPSO) were proposed to solve the existing problems of algorithm selection and hyper-parameter optimization in traditional machine learning model, and their prediction performance were comprehensively compared among each other. A database consisting of 221 open-pit slope stability cases was established, in which 80% of the data were used for training and 20% for model testing. Based on the comparison between the prediction results of four models and the verification results of engineering practices, it is found that the support vector machine (SVM) based on CPSO is superior than other three machine learning models in terms of prediction of slope stability, presenting an accuracy up to 88%. Thus, it can provide a reliable prediction for the safety of slope in open-pit mine.

With Ba (OH)₂·8H₂O and Ti (OC₄H₉)₄ as raw materials, and isopropanol (IPA) as solvent, tetragonal-rich BaTiO₃(BTO) nanopowder was synthesized by adopting solvothermal process. Effects of Ba/Ti ratio, pH value, solvothermal temperature and time on synthesis of tetragonal-rich BTO powders were investigated, and the mechanism of IPA in the solvothermal process for synthesis of BTO powders was also characterized by X-ray diffraction and scanning electron microscopy. It is found that in the solvothermal process, IPA will preferentially provide certain—OH to promote the hydrolysis of Ti (OC₄H₉)₄, generating TiO₆ octahedra to interconnect with Ba²⁺, which is gradually transformed into the tetragonal phase BaTiO₃ with regular morphology after phase transition, dissolution of small particles, and recrystallization in a low alkalinity environment. Experimental results show that under the following conditions including Ba/Ti ratio of 1.6, pH of 10 for the system, a solvothermal process at 220 ℃ for 24 h, calcination at 950 ℃ for 2 h, the synthesized tetragonal-rich BTO nanopowder is well dispersed with regular morphology, square or nearly square shape, with c/a value of 1.009 4 and particle size of 124 nm on average.

The key factors of pile foundation settlement were explored for the slope under vertical load by using grey relational analysis, and it is found that each factor is in the following descending order by its influence: elastic modulus > slope distance > slope gradient > internal friction angle > cohesion > soil density > poisson's ratio of soil > pile length > pile diameter. In order to optimize the parameters of support vector regression (SVR) model, a novel HGWO-SVR model was proposed by integrating the differential evolution-enhanced gray wolf algorithm (HGWO). Compared with GWO-SVR and GS-SVR models, this model presents obvious advantage in prediction, with high accuracy and minor error. A settlement prediction model for pile foundation of slope was constructed based on HGWO-SVR model, and the prediction results were compared with those values calculated with existing settlement formulas. The results show that the maximum percentage error between the prediction value of HGWO-SVR model and the calculated value is 6.55%, thus verifying that this model is feasible in settlement prediction for pile foundation of slope.

To utilize efficiently valuable metal resources containing lithium and beryllium, flotation experiments were conducted based on the study of ore properties. A lithium-beryllium bulk flotation process was used and the influences of dosages of regulator, activator and collector, and the stirring time of regulator on the flotation performance of lithium polymetallic ore were investigated. Based on the determined optimal dosages of calcium chloride and collectors of GYLZ and GYM3, a closed-circuit test produced a lithium concentrate with Li₂O grade and recovery of 6.10% and 94.01% respective, and BeO grade and recovery of 0.12% and 88.53%, respectively, achieving efficient recovery and utilization of lithium and beryllium resources in lithium polymetallic ores.

The occurrence state of iron minerals in a kind of kaolin ore in Guangdong is relatively complex. A portion of iron minerals is irremovable as they disseminate in the lattice of kaolinite, illite and other minerals in an isomorphic manner. For this reason, the calcined kaolin concentrate possesses a lower whiteness than the natural whiteness. In order to efficiently exploit and utilize the kaolin ore, a process consisting of slurry tamping, spiral classifier classification and hydrocyclone classification was adopted, resulting in a kaolin concentrate grading 30.02% Al₂O₃ at 61.70% recovery with the content of impurity Fe₂O₃ at 1.15%, which can reach grade III standard of kaolin for ceramic industry. The classification downflow was then subjected to a process consisting of grinding, magnetic separation and hydrocyclone classification, resulting in a quartz sand concentrate and a sericite concentrate. The quartz sand concentrate, containing 97.11% SiO₂ and 0.058% Fe₂O₃, can satisfy the standard for low quality quartz for glass industry, and the sericite concentrate, containing 7.07% K₂O, 31.22% Al₂O₃ and 48.32% SiO₂, with natural whiteness at 65.53%, can be used in the coating industry. The magnetic separation results in the tailings with a yield of 8.41% and SiO₂ content of 76.33%, which can be used as auxiliary materials for building sand. Through this process, different minerals can be effectively separated to achieve the purpose of comprehensive utilization of kaolin ore.

In order to recover and utilize high value-added iron phosphate waste, an experimental study was carried out by adopting a process consisting of hydrochloric acid leaching, replacement of iron powder for copper removal, and hydrolyzation and chemical precipitation for removal of titanium and aluminum therein. The results show that after 1 h leaching at 60 ℃ with hydrochloric acid concentration of 25%, liquid-solid ratio of 6 mL/g, the leaching rate of iron can be up to 98.7%. And then after 35 min reaction at 60 ℃ with the initial pH of the solution controlled at 0.6, the addition of iron powder at an amount of 0.55 times of the molar number of iron in the leaching solution, the removal rate of copper and titanium can reach 96.2% and 83.6% respectively. By the following process of hydrolyzation and chemical precipitation with sodium fluoride 8 times of the molar number of aluminum, the removal rate of titanium and aluminum can reach 97.6% and 99.3% after 30 min reaction at 40 ℃ with pH of 1.9. It is shown that the content of impurities in the leaching solution meets the requirements for the subsequent synthesis of iron phosphate for batteries.

To examine the industrial feasibility of pre-discarding by using screening classification combined with gravity separation in processing of a scheelite ore from Hunan Province, industrial distributary and flotation trial tests were carried out. The results show that a process consisting of screening and spiral chute discarding under optimized conditions can discard tailings grading 0.034% WO₃ with a yield of 25.50% in mass, leading to tungsten loss of only 2.99%. With this pre-discarding before flotation process, both the grade and recovery of the final flotation concentrate are improved, compared to the concentrate obtained from direct flotation of overflow product.

Based on the studies of catalytic pyrolysis for high-sulfur waste residue (HSWR), it is found that after 90 min pyrolysis at a temperature of 600 ℃, with Fe₂O₃ as a sulfur fixation agent in a mass ratio of 1.5∶1 with HSWR, the total desulfurization rate can be around 85%. The volatile sulfur-containing complex organic matter in HSWR could be transformed into stable inorganic matter, among which the amorphous sulfur could be transformed into crystalline sulfur with purity over 95%. In the residue left after pyrolysis process for desulfurization, the main components include inorganic salts such as sodium sulfate and carbon black. The exhaust gas is mainly composed of simple molecular organics such as CH₄ and C₂H₄, and a small amount of inorganic compounds such as CO, SO₂, CO₂ and HCl. The pyrolysis process for desulfurization consists of four stages: firstly, the amorphous elemental sulfur is vaporized and then crystallized to form crystal sulfur; secondly, as for the elemental sulfur with attachment of organic matter and in a relatively more stable structure, its bond with the hydroxyl or carboxyl of organic phase is broken, leading to sulfur emitted into the atmosphere; at the third stage, the sulfur-containing organic phase is deactivated at the methylene and submethyl sites to form HCl, H₂S and carbon black, which are then adsorbed by sulfur-fixation agent and converted into sulfate; at the fourth stage, the carbon-carbon bond between nitrogen heterocyclic hydrocarbons becomes unstable after grouping, and is broken into small organic molecules such as CH₄ and C₂H₄, as well as carbon black and a trace of H₂. Meanwhile, C—N/C—NH_x bonds are broken into NO_x/NH₃, and C—S/C—SO₃H bonds are broken into H₂S and SO₂, which are then adsorbed by sulfur fixation agents and converted into sulfate.