This system consists of: crushing and screening system, grinding and flotation system, and dewatering system.

A. Crushing and screening section

The crushing and screening system adopts two-stage crushing with one closed-circuit screening process.

Raw magnesite ore (incoming size ≤ 300 mm) is stored in the storage yard. The raw ore is fed into the feeding hopper by a front loader. A chute feeder is installed at the outlet of the feeding hopper to feed the raw ore to the jaw crusher for primary crushing. The primary crushed ore is transported to the vibrating screen by a belt conveyor. The oversize ore is sent to a cone crusher for fine crushing via belt conveyor, and the fine crushed ore from the cone crusher is discharged onto the same belt conveyor and then sent to the vibrating screen. The qualified undersize ore is conveyed to a buffer silo by belt conveyor. The final crushed ore size is 0–15 mm.

This system is equipped with a metal detector and an electromagnetic iron remover at the discharge end of the belt conveyor to effectively prevent metal materials from entering the cone crusher.

B. Grinding and flotation section

The grinding process adopts one-stage grinding and two-stage classification. The first classification uses a spiral classifier. The second classification uses a hydrocyclone cluster. The underflow from the spiral classifier is fed into the ball mill, and the overflow from the spiral classifier is fed into the hydrocyclone cluster for secondary classification. The overflow from the hydrocyclone cluster goes to a pre-sizing cyclone before flotation, and the underflow of the hydrocyclone cluster is fed back to the ball mill.

The raw ore slurry overflow from the cyclone first enters the pre-sizing hydrocyclone cluster for pre-sizing. The overflow slurry (about 20%) from the pre-sizing cyclone directly enters the concentrate thickener for concentration. The underflow (80%) from the pre-sizing hydrocyclone cluster enters the flotation system. The overflow ratio depends on the quality requirement for final concentrates and the raw ore selectivity.

The slurry entering the flotation section is continuously mixed in two sets of agitation tanks and then enters the flotation cells for separation. The slurry undergoes one stage of roughing and four stages of cleaning in an open-circuit flotation configuration. The middlings from each separation stage are collected together and sent to the tailings thickener for concentration by slurry pumps.

Reserve positions are provided for Scavenging I and Scavenging II, and a width of about 1 m is left between the flotation machines for each sorting operation. If the concentrate indicators are good during production, closed-circuit flotation can be considered. This can be achieved by opening or closing valves to convert from cleaning 4 to cleaning 3, cleaning 3 to cleaning 2, cleaning 2 to cleaning 1, and cleaning 1 to roughing, thereby realizing closed-circuit or partial closed-circuit flotation.

The flotation concentrate enters the concentrate thickener for concentration by a foam pump. The flotation operation includes 5 roughing cells, 5 cells for cleaning 1, 4 cells for cleaning 2, 3 cells for cleaning 3, and 3 cells for cleaning 4.

After dilution, flotation reagents are added to the flotation cells by an automatic dosing machine. Four reagent agitation tanks (three for use and one as backup) are used for reagent dilution. The automatic dosing machine is controlled by a PLC, with a total of 16 dosing points.

C. Dewatering section

Tailings dewatering: The flotation tailings enter the tailings thickener for concentration. The underflow from the thickener is pumped by three sets of slurry pumps (two for use, one backup) to three sets of box-type filter presses (one as backup). The filter presses are placed on a raised platform, and the filter cake falls naturally into the area below. When the cake reaches a certain height, it is transported by a front loader to the tailings storage area.

Concentrates dewatering: The flotation concentrate is pumped to the concentrate thickener by two sets of foam pumps (one for use, one standby). The underflow from the thickener enters two sets of vacuum disc filters (one for use, one backup). The filter cake is then conveyed to the concentrate storage yard by a belt conveyor.