A thermodynamic analysis reveals the phase evolution of main metals in the production of low-grade nickel matte by sulfidation smelting of copper-nickel electroplating sludge, and the main influencing factors in the process of sulfidation smelting were analyzed. The thermodynamic calculation shows that with the electroplating sludge grading 6% Cu and 4% Ni, respectively, sulfur gypsum as the sulfurizing agent, the actual addition of sulfur 2.0 times of the theoretical amount, and the smelting atmosphere P(CO)/[P(CO)+P(CO₂)]=50%, the low-grade nickel matter with the expected grade of 57.2% (Cu+Ni) can be produced, with the grade of copper and nickel in the slag lower than 0.2%. It is shown that the direct recovery rate of copper and nickel can reach 99.89% and 96.59% respectively, and the sulfur fixation rate is 77.20%. An industrial application shows that compared with conventional wet metallurgical recovery process, this technique can bring higher metal recovery rate with a green and low carbon process, thus presenting obvious technical advantages.

According to the difficulties in beneficiation, such as intimate dissemination and complicated intergrowth of pentlandite, chalcopyrite and pyrrhotite, and high content of magnesium-bearing silicate minerals, a beneficiation experiment was conducted for a low-grade copper-nickel sulfide ore from abroad. A flowsheet consisting of rough grinding, fine-grinding of middlings, copper-nickel bulk flotation was introduced to treat this raw ore with Ni and Cu grades respectively as 0.50% and 0.20%. Adopting selective grinding approach and using high-efficient depressant CMC, excessive comminution of copper and nickel minerals can be avoided while magnesium-bearing silicate minerals can be selectively depressed. A closed-circuit test produced a copper-nickel concentrate grading 9.70% Ni and 4.75% Cu at corresponding recoveries of 68.99% and 79.85%, indicating copper and nickel resources were all effectively recovered.

Based on a summarization of decomposition techniques of scheelite by hydrometallurgical process, the advantages and disadvantages of several decomposition techniques, such as decomposition with hydrochloric acid, soda sintering, pressure boiling of soda, decomposition with sodium hydroxide, decomposition with fluorine salt, decomposition with mixture of sulfuric acid and phosphoric acid, as well as lime sintering conversion followed by decomposition with ammonium bicarbonate were all analyzed. It is concluded that those three techniques, including decomposition with fluorine salt, pressure boiling of soda and decomposition with mixture of sulfuric acid and phosphoric acid, will gradually become the mainstream decomposition techniques for scheelite.

In order to obtain the optimal concentration of bone glue as a commonly used additive for lead electrolysis and also understand the influence of its colloidal impurities on lead electrolysis, the effects of the concentration of bone glue in the electrolyte, the standing time of bone glue solution and the liquid-solid ratio for purification with activated carbon on lead electrolysis were investigated by evaluating the turbidity of the solution, current efficiency, power consumption and the morphology of precipitated lead. It is found that the optimal concentration of bone glue in lead electrolyte is 0.8 g/L, and colloidal impurities can be removed by resting the bone glue solution for 72 hours or by purifying it with activated carbon in a ratio of 1 000∶1. After purification, lead electrolyte has its current efficiency up to 99.19%. The power consumption of electrolysis declines to 51.79 kW·h/t, and the obtained precipitated lead has a flat and smooth surface.

Based on a deep foundation pit project for Pazhou Station of Guangzhou Metro, numerical simulation was conducted with FLAC^3D finite element software for foundation pit excavation. Shear test schemes with different stress paths were prepared based on the stress state of the surrounding soil of the foundation pit, and the influence of different stress path on the mechanical properties of the soil was also studied. The results indicate that stress path can bring significant impact to the stress-strain relationship, pore pressure, and shear strength indicators of the soil. The shear strength of the soil in consideration of the unloading stress path of the foundation pit is lower than the shear strength obtained from conventional tests.

Mineral processing tests were conducted for a fine refractory copper ore with Cu grade of 0.75%. A combined process consisting of magnetic separation, rapid flotation of copper minerals, enhanced copper flotation of rapid flotation tailings, and regrinding and cleaning of rough copper concentrate was adopted in a closed-circuit test, yielding a copper concentrate grading of 23.57% Cu at a recovery of 83.23%.

In order to study the influences of diameter, length and installation position of tapered pipeline on the ratio of full pipe flow in gravity-fed pipeline transport of backfill slurry, a small-scale loop pipe test was carried out by using independently developed tapered pipeline. The hydraulic slope and ratio of full pipe flow were tested for gravity-fed transport of slurry via tapered pipeline, and Pearson correlation analysis was also conducted to explore the influence of various factors on the ratio of full pipe flow. The results show that the ratio of full pipe flow significantly presents a negative correlation to the diameter of tapered pipeline, which increases exponentially with the reduction in the diameter of tapered pipeline. The ratio of full pipe flow increases sharply for a pipe with diameter less than 50 mm. Furthermore, the ratio of full pipe flow presents a positive correlation to the length of tapered pipeline, which increases linearly with the increased length of tapered pipeline. However, the installation position of tapered pipeline in horizontal section of pipe has little effect on the ratio of full pipe flow, which can be negligible.

In order to improve the construction efficiency in benching excavation for tunnels in water-rich ground, a main tunnel of Xiaomaliu tailings pond was taken as an example in the study. A three-dimensional digital model was constructed according to the actual situation of the project, and the fluid-structure interaction analysis was conducted by simulating benching excavation with three types of bench length. Then, the effect of benching construction with different bench length was analyzed in terms of seepage field, displacement field, stress field and plastic zone distribution of tunnel after construction, and a comprehensive evaluation was presented by using CRITIC algorithm. Results show that excavation with micro bench can bring the best construction effect for the tunnel in water-rich ground, followed by excavation with long bench, and excavation with short bench presents poor effect.

Tests were conducted to compare the performance of detergent FD-602 and nitric acid in cleaning the copper concentrate ceramic filter plate in Tonglushan Mine in Hubei Province. The results show that after being cleaned with FD-602, the ceramic filter plate has cleaner surface and its filter cake also presents uniform adsorption during filtration. After being cleaned using FD-602 and nitric acid, the ceramic filter can produce 6.63 t/h and 5.85 t/h filter cakes on average, with average moisture of 11.21% and 11.58%, respectively. Every ton of filter cake consumes 0.16 kg and 1.78 kg detergent, with the cost of 6.4 yuan and 5.696 yuan, respectively. When the cleaning water collected from the FD-602 cleaning process mixed with domestic water at a ratio of 1∶5 is returned to flotation process, it is shown that there is no obvious influence brought to the flotation performance.

With Sanguikou Lead Zinc Mine in the Inner Mongolia Autonomous Region taken for study, the influencing factors and parameter optimization for rock fragmentation by deep-hole cut blasting were explored by performing theoretical analysis, image processing and engineering tests. Firstly, in view of the problems of high fines generation rate and small fragment size on average, the factors influencing blasting fragmentation were tested and field data were collected. Also, image processing and analysis were performed for the muckpile in the test by using Split-Desktop 4.0 software. Then, the primary and secondary factors affecting blasting fragmentation were determined based on grey correlation analysis. Finally, an optimal scheme of blasting parameters was determined by using trend analysis based on actual situation of the site, and was then verified in the practical engineering test. The results show that the fines generation rate by the cut blasting in the mine is mainly affected by the delay time between rows and the borehole spacing, and the average fragment size is mainly affected by the borehole spacing and the number of rows for blasting. The optimized blasting parameters are finally determined as follows: borehole spacing of 1.2 m, row spacing of 1.5 m, burden of 0.8 m, 3 rows of boreholes, delay interval of 13 ms, 0 ms, 9 ms and 18 ms, respectively, between 4 holes, and a delay interval of 42 ms between rows. With the above-mentioned parameters, the blasting can result in the fines generation rate down by 27.19% and the average fragment size up by 62.89%.