The Tahuehueto Project preliminary feasibility study describes a conventional 550 tpd crushing, grinding, and flotation plant designed to produce separate lead, copper, and zinc concentrates over a 21-year mine life.
Report context
The Tahuehueto Project preliminary feasibility study was completed by Metal Mining Consultants Inc. on January 20, 2017 for Telson Resources Inc. The report presents the processing plant design criteria, equipment selection, mass balance, metallurgical balance, capital cost estimate, operating cost estimate, and manpower requirements for a flotation plant designed to process 165,000 tonnes per year.
Processing route
Crushing circuit
The proposed crushing circuit receives ore from the mine in 20 t capacity dump trucks. Coarse ore is discharged to an 80 t coarse ore bin fitted with a 46 cm grizzly. Oversize rocks greater than 46 cm are reduced using a pneumatic hammer or by hand. A 61 cm apron feeder delivers ore from the coarse ore bin to a primary jaw crusher (76 cm x 91 cm). Material passes through a fixed 5 cm screen before entering the secondary crushing stage.
The secondary multi-impact crusher reduces ore to minus 10 mm. A 61 cm conveyor belt carries crushed ore to vibrating screens (1.2 m x 2.4 m) operating in closed circuit with the secondary crusher. Screen oversize is returned by conveyor to the secondary crusher; screen undersize reports to a 550 t fine ore bin.
Grinding and gravity concentration
The flotation circuit is designed to process a peak of 165,000 tpy in 300 operating days, equivalent to 550 tonnes per day and 22.9 tph through the grinding and flotation circuits. Fine ore is fed to a single nominal 2.4 m x 2.4 m ball mill fitted with a 300 HP motor. Water is added at a rate of 23 m³/h, comprising 80% recycled water and 20% fresh water. First flotation reagents are added at this point: AF 404 and AF 242 promoters and 1,100 g/t ZnSO₄.
The grinding circuit operates in closed circuit with cyclones. Ore is ground to 80% passing 200 mesh before the pulp is fed to a gravimetric concentrator (Falcon or Nelson type). The gravimetric concentrator recovers free heavy metals including gold, silver, and iron. Concentrate from the gravimetric unit is sent to the lead concentrate decanter for mixing and filtering. Tailings from the gravimetric concentrator proceed to flotation.
Flotation circuits
The flotation plant is designed as three separate circuits producing lead, copper, and zinc concentrates.
Lead-copper bulk circuit
Conditioned pulp enters the first bank of flotation cells where bulk lead-copper concentrate is recovered with associated gold and silver. The bulk concentrate passes to cleaning flotation cells where AF-404 and ZnSO₄ are added to separate lead concentrate from copper.
Copper circuit
Tails from the lead cleaning cells are sent to additional flotation cells where AF-242 is added to separate copper concentrate.
Zinc circuit
Bulk lead-copper flotation tailings are sent to a conditioning tank for zinc. A total of 1 kg/t of CuSO₄ and 2 kg/t of CaO are added. Conditioning time is 30 minutes. The conditioned pulp is sent to zinc rougher flotation cells, followed by two stages of cleaning to produce zinc concentrate. Tailings from the zinc circuit are sent to the tailings decanter for water recovery.
Concentrate handling
Concentrates of Pb, Cu, and Zn are sent to decanters where solids content is increased to 90%. Recovered water is sent to the recycled water tank and returned to the process. Concentrates with 10% water are sent by gravity to the concentrate storage building, loaded onto 30 t trucks, sampled, weighed, packed, and shipped. The Cu and Pb concentrates are sent to the port of Manzanillo, Colima, and the Pb concentrates to Matehuala, San Luis Potosí.
Tailings disposal
Flotation tailings are sent to a decanter which recovers 90% of the water. The resulting tailings pulp with 90% solids is sent to the tailings dam with 10% water, deposited using the same 20 t trucks used for ore haulage. The tailings dam has an estimated capacity of above the 38 million tonnes required from the production schedule.
Plant equipment
The processing plant equipment is summarised in the following table.
| Equipment Type | Required |
|---|---|
| Coarse Ore Hopper 80 t | 1 |
| Apron Feeder 61 cm | 1 |
| Grizzly 46 cm Rail Separation | 1 |
| Jaw Crusher 76 cm x 91 cm | 1 |
| Conveyor Belt 46 cm x 12 m | 1 |
| Multi-impact (Secondary) Crusher | 1 |
| Conveyor Belt 46 cm x 22 m | 1 |
| Vibrating Screen 1.2 m x 2.4 m | 2 |
| Conveyor Belt 46 cm x 7 m | 2 |
| Conveyor Belt 46 cm x 24 m | 1 |
| Fine Ore Hopper 550 t | 1 |
| Conveyor Belt 46 cm x 7 m | 1 |
| Continuous Scale | 1 |
| 300 HP Ball Mill (Used) 2.4 m x 2.4 m | 1 |
| Horizontal Centrifugal Pump 2.4 m x 1.8 m | 3 |
| Classifiers | 2 |
| Gravimetric Concentrator | 2 |
| Conditioner Tank 2.4 m x 2.4 m | 2 |
| 3 Flotation Cells Bank 10 t | 2 |
| 4 Flotation Cells Bank 15 m | 2 |
| 2 Flotation Cells Bank 15 m | 4 |
| Horizontal Centrifugal Pump 6.4 cm x 5.1 cm | 4 |
| Clarifying Decanter | 4 |
| Conditioner Tank 1.5 m x 1.5 m | 1 |
| 1 Flotation Cells Bank 10 t | 1 |
| Horizontal Centrifugal Pump 3.8 cm x 2.5 cm | 1 |
| Crushing and Mill Building | 1 |
| Flotation and Filtering Building | 1 |
| Lab Equipment | 1 |
| Fresh Water Tank | 1 |
| Recycled Water Tank | 1 |
| Reagents Tanks and Buildings | 1 |
| Auxiliary Plant Equipment | 1 |
Project website: https://lucamining.com/tahuehueto/
Reagents
| Reagent | Application | Quantity |
|---|---|---|
| CaO | pH control | 2,000 g/t |
| ZnSO₄ | Zinc depressant | 1,100 g/t |
| AF-242 | Promoter / Collector Pb-Cu | 70 g/t |
| AF-404 | Promoter / Collector Pb-Cu | 70 g/t |
| Mibc-70 | Frother | 50 g/t |
| CuSO₄ | Zinc activator | 1,000 g/t |
| AF-211 | Zinc promoter | 80 g/t |
| X-343 | Zinc collector | 30 g/t |
| Xanthate | Collector | 30 g/t |
Manpower
The plant is designed to operate two 12 hour shifts per day, based on 20 working days followed by 6 days off. Total mill personnel are 58, comprising 16 mill administration staff, 32 plant operators, and 10 mill maintenance personnel. Process plant manpower is summarised in the following table.
| Assigned Group | Function | Number of Personnel |
|---|---|---|
| Mill Administration | Mill Manager | 1 |
| Mill Superintendent | 1 | |
| Metallurgist | 2 | |
| Mill Operations Foreman | 4 | |
| Maintenance Superintendent | 1 | |
| Maintenance Foreman | 3 | |
| Plant Electrical Foreman | 1 | |
| Metallurgical Accountant | 2 | |
| Mill Administrative Assistant | 1 | |
| Total Mill Admin | 16 | |
| Plant Operators | Crushing Control Room | 4 |
| Crush and Convey | 8 | |
| Grinding and Flotation | 4 | |
| Regrind/Cleaner Float | 4 | |
| Thickener and Filtration | 4 | |
| Sampler | 4 | |
| Packing/Shipping/Reagents | 2 | |
| Tailings/Water Treatment | 2 | |
| Total Plant Operators | 32 | |
| Mill Maintenance | Crusher | 8 |
| Grinding and Flotation | 4 | |
| Regrind/Cleaner/Filter/Packing | 8 | |
| Electrician | 4 | |
| Instrument Technician | 4 | |
| Total Mill Maintenance | 10 | |
| Total Mill Personnel | 58 |
Key reported parameters
| Description | Units | Value |
|---|---|---|
| Operating Days | dpy | 300 |
| Capacity | tpd | 550 |
| Peak Tonnes per Year | tpy | 165,000 |
| Total Ore Processed | kt | 3,264 |
| Head Grade Gold | gpt | 3.504 |
| Head Grade Silver | gpt | 41.931 |
| Head Grade Copper | % | 0.348 |
| Head Grade Lead | % | 1.192 |
| Head Grade Zinc | % | 2.242 |
| Contained Gold | kg | 11,083 |
| Contained Silver | kg | 136,443 |
| Contained Copper | kt | 11.35 |
| Contained Lead | kt | 38.90 |
| Contained Zinc | kt | 73.17 |
| Life of Operation | years | 21 |
| Crushing hours per day | h | 12 |
| Crushing rate | tph | 45.8 |
| Grinding and filtering hours per day | h | 24 |
| Grinding and filtering rate | tph | 22.9 |
| Total Processing Capital Cost | USD $k | 14,350 |
| Total Processing Operating Cost (LOM) | USD $k | 100,529 |
| Unit Processing Operating Cost | USD/t | 30.80 |
Technical qualifications
The processing route and equipment selection are presented as a design based on metallurgical testing performed to date. The report states that the flotation process chosen will work, flotation targets are attainable, and an economical concentrate can be produced. Additional information on operating parameters and reagents for optimising recoveries and concentrate quality will be obtained from the 3,500 tonne industrial scale bulk testing discussed in Section 24. The basic design criteria used for the economic analysis and plant design show the results of the last confirmation metallurgical test run, specifically for the use of new reagents and for extra capacity to process high grade ores.
The mass balance for the flotation plant was prepared from metallurgical testing and the average annual metallurgical balance. Equipment selection was based on experience with the construction of other similar processing plants, with consideration given to energy efficiency and low water consumption. The total processing capital cost of USD $14,350,000 is stated without contingency.
Source: Tahuehueto Project – Preliminary Feasibility Study, Metal Mining Consultants Inc., January 20, 2017, Telson Resources Inc., relevant sections.
