This PEA technical report describes the proposed 800 tonnes per day mineral processing plant design for the La Mina VMS Project in Ecuador.
Report context
The NI 43-101 Preliminary Economic Assessment Technical Report for the La Mina VMS Project, prepared by SGS Canada Inc., presents the process design criteria for the proposed 800 tonnes per day copper, lead, zinc, gold and silver mineral processing plant. The recovery methods section details the conceptual design for crushing, grinding, flotation, and dewatering facilities.
Processing route
Primary crushing
Run-of-mine material is transported to the crushing plant area by rear-dump trucks. The primary crushing line consists of a dump hopper, grizzly screen, rock breaker, crusher and associated dust collection and transfer equipment. ROM material is dumped into the dump hopper by rear-dump trucks. The grizzly screen oversize feeds the jaw crusher. One mobile rock breaker is available to service the crusher or screen. The crusher reduces the ROM size from a maximum of 450 mm to approximately P100 of 249 mm. Crushed material drops onto a belt conveyor that transports it to a stockpile.
The crushing production rate is monitored by a belt scale mounted on the conveyor. Tramp iron is removed using a magnet located at the discharge of the primary crusher discharge conveyor. A metal detector would be installed over the conveyor. Dust is controlled in the dump pocket with water sprays and dust collector vents positioned at the conveyor transfer points. An air compressor and instrument air dryer are installed for operation and maintenance. A mobile crane is installed for maintenance of the primary crusher.
Crushed material conveying, transport and storage
Primary crushed material is stockpiled on the ground. A reclaim tunnel is installed beneath the stockpile. The stockpile would contain approximately 800 tonnes of “live” storage. When required, the material is moved from the “dead” storage area to the “live” storage area by a front-end loader.
Material is withdrawn from the coarse reclaim stockpile by variable speed belt feeders. The feeders discharge to the transfer conveyor belt. The transfer conveyor discharges to the SAG mill in the grinding circuit. The reclaim rate is monitored by a belt scale mounted on the conveyor. Dust control in the stockpile area is achieved using a wet type dust collector system. One of the two dust collector systems is installed to control dust at the discharge of the stockpile feed conveyor and another one is installed to control dust in the reclaim tunnel.
Grinding
The mineralized material would be ground in a SAG mill primary grinding circuit and a ball mill secondary grinding circuit. The SAG mill would operate in closed circuit with a vibrating screen. Water is added to the SAG mill to produce a slurry and the material feed size is reduced as it traverses the SAG mill. The SAG mill discharges onto a double deck screen with 8.0 mm sized bottom openings. Screen oversize is recirculated to the SAG mill feed chute by a series of conveyors. Screen undersize flows by gravity to the cyclone feed pump box. A belt scale mounted on the recycle conveyor is used to monitor the SAG mill recycle rate. The target SAG grind would be P80 of 1,354 microns.
Secondary grinding is performed in a ball mill. The ball mill operates in closed circuit with hydrocyclones. Ball mill discharge is combined with vibrating screen undersize in the cyclone feed pump box and pumped to hydrocyclone clusters. Combined slurry is pumped using variable speed horizontal centrifugal slurry pumps (one operating and one standby) to the cyclone clusters.
Hydrocyclone overflow (final grinding circuit product at 80% minus 70 microns) flows by gravity to the tramp oversize screen positioned prior to the flotation circuit. Cyclone overflow would be sampled by primary samplers and analysed by the copper/lead and zinc on-stream analyser for metallurgical control prior to flotation. Cyclone overflow from the cyclone cluster is also monitored for particle size distribution by a particle size monitor.
Zinc sulfate (ZnSO4), sodium sulfide (Na2S) and sodium metabisulfite, Na2S2O5 (SMBS) would be added into the ball mill. Grinding balls would be added to the SAG mill and ball mill by ball loading systems. Air compressors and an instrument air dryer would provide service and instrument air for operations and maintenance. An overhead crane is installed for maintenance of the grinding mills.
Copper/Lead flotation and regrind
Hydrocyclone overflow would flow by gravity to the copper/lead flotation circuit. The copper/lead flotation circuit would consist of one row of rougher cells and one row of cleaner cells. The rougher row consists of six (6) 10 m³ tank type rougher flotation cells with a drop between each cell. The copper/lead rougher concentrate is sampled by a rougher concentrate primary sampler and pumped (one operating pump and one spare) to the copper/lead regrind mill circuit. Reground copper/lead rougher concentrate flows by gravity from the lead cleaner conditioning tank to the copper/lead first cleaner flotation cells. The copper/lead cleaner row consists of ten (10) flotation cells: five (5) 1.4 m³ forced air first cleaner cells, two (2) 1.4 m³ forced air first cleaner scavenger cells, two (2) 0.71 m³ forced air second cleaner cells, and one (1) 0.71 m³ forced air third cleaner cell. The copper/lead first cleaner concentrate is pumped (one operating pump and one spare) into the second cleaner flotation cells. Copper/lead rougher tailing and copper/lead first cleaner scavenger tailing flow by gravity into the zinc rougher conditioning tank. The copper/lead second cleaner concentrate would be pumped to the copper/lead third cleaner flotation cell. The copper/lead third cleaner concentrate flows by gravity to the copper/lead concentrate thickener.
The concentrate samples cut by the samplers are analysed for process control by the copper/lead and zinc on-stream analyser. Tailing from rougher flotation cells and first cleaner scavenger cells are combined together and sampled with primary samplers and analysed by the copper/lead and zinc on-stream analyser.
Copper/lead rougher concentrate would be pumped to the lead regrind cyclone feed pump box and combined with the regrind mill discharge. The combined slurry is pumped using horizontal centrifugal slurry pumps (one operating and one spare) to a hydrocyclone cluster. Overflow from the regrind cyclone cluster (final regrind circuit product) is sampled for particle size distribution analysis by the copper/lead regrind cyclone particle size monitor. It is then analysed by the copper/lead and zinc on-stream analyser and flows by gravity to the copper/lead cleaner conditioning tank. The cyclone underflow flows by gravity to the copper/lead regrind mill. Product from the regrind mill reports to the copper/lead regrind cyclone feed pump box.
Air compressors, air receivers, and instrument air dryer are installed for general plant operation and maintenance. A bridge crane is installed for maintenance of the flotation and regrind equipment.
Zinc flotation and regrind
Copper/lead rougher tailing and copper/lead first cleaner scavenger tailing would flow by gravity to a zinc rougher conditioning tank. The zinc flotation circuit consists of one row of rougher cells and one row of cleaner cells. The rougher row consists of five (5) 10 m³ tank type rougher flotation cells. The zinc rougher concentrate would be sampled by the zinc rougher concentrate primary sampler and pumped (one operating pump and one spare) to the zinc regrind mill circuit. The zinc cleaner row consists of ten (10) flotation cells: one bank of six (6) 1.4 m³ forced air first cleaner flotation cells, two (2) 1.4 m³ forced air first cleaner scavenger flotation cells, and two (2) 0.71 m³ forced air second cleaner flotation cells. Tailings from zinc rougher cells and zinc first cleaner scavenger are pumped to the tailing sample box, then to the tailing thickener.
Reground zinc rougher concentrate flows by gravity from the zinc cleaner conditioning tank to the zinc first cleaner flotation cells. The zinc first cleaner concentrate is pumped (one operating pump and one spare) into the zinc second cleaner flotation cell. The zinc secondary cleaner flotation concentrate is pumped to the zinc concentrate thickener.
The concentrate samples cut by the samplers would be analysed for process control by the copper/lead and zinc on-stream analyser. Tailing from rougher flotation cells and first cleaner scavenger cells are sampled with primary samplers and analysed by the copper/lead and zinc on-stream analyser.
Zinc rougher concentrate would be pumped to a zinc regrind hydrocyclone feed pump box and combined with the zinc regrind mill discharge. The combined slurry is pumped using horizontal centrifugal slurry pumps (one operating and one spare) to the zinc regrind hydrocyclone cluster. Overflow from the zinc regrind cyclone cluster is sampled by sampler for particle size distribution analysis by the zinc regrind cyclone particle size monitor. It is then analysed by the copper/lead and zinc on-stream analyser and flows by gravity to the zinc cleaner conditioning tank. The underflow flows by gravity to the zinc regrind mill. Product from the regrind mill reports to the zinc regrind cyclone feed pump box.
Copper/Lead concentrate dewatering
Concentrate from the copper/lead third cleaner flotation cell would be pumped to a copper/lead concentrate thickener. The concentrate thickener overflow is pumped back to the thickener feed for dilution and the thickener spray bar; to control froth, or to the copper/lead process water tank. The concentrate thickener underflow is pumped (one operating pump and one spare) to an agitated storage tank and then to a pressure filter. Filter cake is discharged to a covered stockpile. Concentrates, both copper/lead and zinc, would be reclaimed and bagged.
Zinc concentrate dewatering
Concentrate from the zinc secondary cleaner flotation cell would be pumped to a zinc concentrate thickener. The concentrate thickener overflow is pumped back to the thickener feed for dilution and the thickener spray bar; to control froth, or to the zinc process water tank. The concentrate thickener underflow is pumped to an agitated storage tank and then to a pressure filter. Filter cake is discharged to a covered stockpile.
Tailing dewatering
Tailings from the zinc rougher flotation and zinc first cleaner scavenger would be pumped to a high rate tailings thickener. Thickener overflow flows by gravity from the tailings thickener overflow tank to the copper/lead process water tank. Thickener underflow is pumped by variable speed horizontal centrifugal slurry pumps (one operating and one stand-by) to the TSF.
Reagents
Reagents requiring receiving, handling, mixing, and distribution systems include: Sodium Sulfide (Na2S), Zinc Sulfate (ZnSO4-7H2O), Aerofloat 242 (Promoter), Aerophine 3418A (Promoter), Sodium Metabisulfite (Na2S2O5, SMBS), Copper Sulfate (CuSO4-5H2O), Sodium Isopropyl Xanthate (SIPX), Methyl Isobutyl Carbinol (MIBC, frother), Flocculant, and Lime.
Water system
The Plant’s fresh water requirement would primarily be met using wells and by recycling water from the effluent treatment plant water pond.
The copper/lead process water tank would receive overflow from the copper/lead concentrate thickener, tailing thickener and water reclaimed from the TSF. The copper/lead process water is used as makeup water in the primary cyclone feed sump. Fresh water can be added to the copper/lead process water tank if necessary. This copper/lead process water is not suitable for general distribution throughout the process plant. Water would be reclaimed from the effluent treatment plant pond using barge-mounted reclaim water pumps.
Overflow from the zinc concentrate thickener and copper/lead process water excess overflow would be recycled to the zinc process water tank, and used as makeup water in the zinc flotation circuit. Fresh water can be added to the zinc process water tank.
Key reported parameters
| Parameter | Value | Unit | Basis |
|---|---|---|---|
| Plant throughput | 800 | tonnes per day | Proposed design |
| Primary crusher feed top size | 450 | mm | Design |
| Primary crusher product P100 | 249 | mm | Design |
| Primary crusher product P80 | 114 | mm | Design |
| SAG mill target grind P80 | 1,354 | microns | Design |
| Final grinding circuit product | 80% minus 70 | microns | Design |
| SAG mill screen opening | 8.0 | mm | Design |
| Coarse stockpile live capacity | 800 | tonnes | Design |
| Copper/lead rougher flotation cells | 6 × 10 | m³ | Design |
| Copper/lead cleaner flotation cells | 5 × 1.4, 2 × 1.4, 2 × 0.71, 1 × 0.71 | m³ | Design |
| Zinc rougher flotation cells | 5 × 10 | m³ | Design |
| Zinc cleaner flotation cells | 6 × 1.4, 2 × 1.4, 2 × 0.71 | m³ | Design |
Technical qualifications
This report presents process design criteria for a proposed plant based on conceptual design. The processing route described is a proposed design, not historical operating data or testwork results. The report does not present actual metallurgical testwork performance data, economic analysis, or current operational status of the La Mina Project.
Source: NI 43-101 PEA Technical Report – La Mina VMS Project – Ecuador, SGS Canada Inc., Recovery Methods section (Sections 17.0–17.11).
