Mineral Processing And Recovery Methods

The facilities for the Fujian Project operation are underground and include a water treatment plant, an underground crushing plant, a milling and flotation plant, a filtration and paste backfill factory, and other buildings. The processing facility creates a bulk flotation concentrate rich in sulfides and containing gold. Pyrite, sphalerite, and galena are the principal sulfur-containing minerals. Additionally found is a trace amount of chalcopyrite. Quartz and manganese minerals make up the majority of gangue minerals. Galena and pyrite are the two minerals that are most commonly found with fine-grained gold. Sphalerite and pyrite liberate well overall, with the fine-size fractions liberating even better. Galena also demonstrates improved liberation for the fractions of fine size. 80% passing 58 m was judged to be the ideal primary grind size. The flotation reagents included copper sulfate (CuSO4.5H2O) as an activator, sodium bisulfite (NaHS) as a sulfidizing agent, xanthate (SIBX) as a collector, S-8045 as a promoter, and OrePrep F-549 as a frother.

Gold recovery is often inversely correlated with sulfur recovery and has recently averaged between 93 and 94%. Underground crushing and a conveyor are used to move crushed run-of-mine ore to two ore storage bins on the surface.

With the help of the two ore storage bins, it is possible to mix various ore types used as feed for the processing plant in order to reach a specific gold/sulfur ratio and lower the concentration of undesirable elements for concentrate sales. A ball mill run in a closed circuit with hydro cyclones, a Semi-Autogenous Grinding (SAG) mill run in a closed circuit with a pebble crusher, and a flash flotation cell make up the comminution circuit. To recover the quickly floating freed sulfide mineral particles and avoid over-grinding of gold-containing particles, the ball mill discharge is treated in a flash cell.

A rougher/scavenger flotation bank receives hydrocyclone overflow. In addition to surface-based ore sorting, milling, flotation, and dewatering circuits, a paste backfill facility, waste storage before it is finally disposed of at the main mine, and concentrate storage before it is transported to the mill are all included in the project.

Underground Crushing

The extracted ore will enter an underground primary jaw crusher, and the crushed ore will be brought to the surface by a vertical conveyor and kept in a silo at the services building. The major crushing machinery will be set up underground to minimize surface disruptions, improve operational effectiveness, and lessen surface noise and dust.

Services Building


The Services Building at the surface has a silo where the primary crushed ore from the subterranean mine is kept. Mineral sorters will be used to finish the first concentration phase. Coarser particles (more than 10 mm) are separated, washed, and delivered to the minerals sorters through a screen that receives feed from the surface silo. A secondary cone crusher is used to further crush the material produced by the mineral sorter (sulfur and gold-bearing material), and the secondary crusher's output will either feed the milling and flotation circuit for additional concentration or the final concentrate silo for delivery to the main mill. Waste from the ore sorter is delivered to a waste silo and put in the facility that stores waste rock.

In the second concentration stage, flotation is employed. The flotation concentration circuit will be fed with a portion of the mineral sorter concentrate and any particles smaller than 12 mm that pass through the screens. The ore will go into a ball mill that is enclosed by a cyclone cluster, and the ball mill's output will go into a circuit for the flotation of pyrite. The ore will then be further divided into flotation tailings and a pyrite flotation concentrate. It will thicken and filter both the flotation concentrates and the flotation tailings. The final ore bin will then be filled with the flotation concentrate and a portion of the mineral sorter output, and it will be kept there until it is time to transport it to the main mill.

A rougher/scavenger flotation bank and two parallel cleaner flotation banks make up the flotation circuit. The first two cells of the rougher/scavenger bank and the flash flotation cell concentrates are pooled and upgraded in the cleaner bank. In cleaner bank 2, rougher cells 3-6 concentrations are treated.

The final concentrate thickener receives the combined concentrations from cleaner banks 1 and 2. Filtered concentrate from the concentrate thickener's underflow is kept in large bags for transportation. A tailings thickener receives the tailings. The last tails go through a filter. The underground paste backfill operation uses a portion of the tailings, and the remainder is dry stored in the tailings storage facility (TSF).


As the third cleaner flotation stage, column flotation is anticipated to improve concentrate quality while reducing concentrate tonnage with minimal gold recovery loss. For the design and installation of column flotation cells in the circuit, a project was started in late 2020. Two flotation column cells measuring 1.8 m (diameter) x 8 m (height) will be installed and put into service in 2023 based on mass balance and simulation studies carried out using plant surveys and pilot scale column flotation experiments. Depending on the needs of the plant, the two-column flotation cells can be used as the third cleaner flotation stage either in parallel or in series.


Schematic Section through Fujian Project Open Pit


Isometric View of Open Pit Shell

With output rates planned to achieve a ramp-up to match process feed requirements, the mining program starts as an open pit operation. The open pit excavation rates were reduced due to the declining strip ratios. The open pit has been planned in two stages to postpone some of the trash strippings until later years. The first stage has a 420mRL design limit, and the second stage has a 315mRL limit. With the exception of the south wall, the first stage has slightly steeper wall angles and lower wall heights. The eventual pit's bench heights will be 20 meters, with an 8-meter waste mining depth envisaged. To maximize mineral extraction, mining will be done at operating bench heights of 4m with 2.5m flitches. The haul road inside the pit ranges in width from 18 meters for most of its length to 12 meters close to the bottom, with a typical 10% grade. Outside of the pit, haul roads are 18 meters wide. At 480 mRL, the external haul road enters the open pit mining area, and at 630 mRL, it is at its highest point.

A three-dimensional (3D) model of the current design pit shell was given to the site. An isometric picture of the design pit shell that displays the topography as it is today. The table below lists typical pit design characteristics as determined by the 3D model. Overall, the design pit shell complies with the geotechnical design advice of the consultant. Expert geotechnical consultants with a solid reputation and relevant experience have contributed to the development of the open pit design.

Consideration Observation
Maximum Crest Level 562m (in ESE Sector)
Floor Level 322m
Maximum Overall Pit Wall Height 241m (in ESE Sector)
Ramp Spiral, entry in West at Level 435m
Ramp Width 13m (above level 360m), 8m (below level 360m)
Average Ramp Grade 1:10.46
Overall Pit Wall Angle 41.6° to 43.8°
Upper Pit Wall Angle 35° in South Sector above ramp,
45° to 46° in other Sectors above ramp
Lower Pit Wall Angle 56° for 80m high bench stack below ramp in North Sector 48° for 60m high bench stack below ramp in South Sector
Bench Height 15m
Bench Angle Approximately 65°
Berm Width Typically 6m to 8m, but 15m in South Pit Sector

Underground Mine

With a maximum of 332 stopes and an average production rate of 115 tonnes per day per heading, including backfill time, the underground mine plan is feasible. After mining is finished, stopes are gradually filled back in, with some stopes being quickly filled in when the mining sequence and alignment let it. Various mining techniques are used, depending on the stope width and mining orientation. For overhand cut-and-fill stopes, the mining of a 76 m long ore drive is anticipated to require 13 to 15 shifts, and for underhand cut-and-fill stopes, up to 33 shifts. An average backfill cycle may need 11 shifts. Once the underground mining operation is established, a variety of underground mining techniques are used to target the orebody and produce an essentially constant production rate.


With the help of several local businesses and a reputable international company that offers consulting, planning, and construction services under the earth, Yazhou Huangjin has created an underground mining operation. There is a 3D model available that displays the layout of the intended underground mine.