A 500 tpd concentrator using gravity and flotation to produce gold-bearing sulphide concentrates, designed with conventional crushing, milling, and filtration equipment.
The metallurgical process described in the 2018 preliminary economic assessment aims to produce gravity and flotation concentrates in a plant with a capacity of 500 tonnes per day, operating 347 days per year. The plant consists of a single production line using two conventional processes: gravity followed by flotation, both intended to obtain sulphide concentrates containing gold. The process path includes a dry section, comprising primary and secondary crushing and milling, and a wet plant, which includes gravity concentration, flotation, and filtration of concentrates. A stockpile of 19,402 tonnes from development of stopes in the Guayabito and Guaico-Nus areas will be maintained for commissioning. The general flow sheet is organized into four sections: primary and secondary crushing, grinding and gravity, flotation, and concentrate filtration.
## Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Plant capacity | 500 | tpd | |
| Annual operating days | 347 | days/year | |
| Head grade | 6.43 | g/t Au | Not stated |
| Commissioning stockpile | 19,402 | t | |
| Primary crusher | 20 x 32 | in | Jaw crusher, 1 unit |
| Ball mill | 8 x 10 | ft | 1 unit |
| High-frequency screen | 1.2 x 3.6 | m | 1 unit, 1.6 mm openings |
| Gravity concentrators | 2 | units | Semi-continuous, 80 t/h each, 1 operating, 1 standby |
| Cyclones | 3 | units | D-10, 2 operating, 1 standby |
| Conditioning tank | 1.7 x 1.7 | m | 1 unit |
| Rougher cells | 4 | cells | 1.5 m³/min each |
| Scavenger cells | 4 | cells | 1.5 m³/min each |
| Cleaner cells | 10 | cells | 0.5 m³/min each |
| Concentrate holding tank | 10 x 10 | ft | 1 unit |
| Fresh water requirement | 11 | m³/h | |
| Concentrator CAPEX | 14.2 | US$M | |
| Total CAPEX | 25.9 | US$M | |
| Total OPEX | Not stated | US$M |
## Overview
The plant is designed to treat underground mineralized material in a conventional gold recovery circuit. Ore is delivered by dump trucks with a 25 m³ capacity to a coarse chute of 150 tonnes capacity, then passes through a hopper with an 8 inch (200 mm) grill. A vibrating grizzly with 2 inch (50 mm) rails classifies the material. Oversize proceeds to a secondary crusher, while undersize is screened. The circuit includes a dust suppression system at transfer points.
## Key Process Stages
Primary and Secondary Crushing
Material passes through a hopper with an 8 inch grill, is extracted by a vibrating grizzly with 2 inch rails, and classified on a vibrating screen with 68 mm upper and 39 mm lower mesh openings. Oversize from the upper floor is sent to a conical crusher, while fine material is sent to the fines chute.
Grinding and Gravity
Crushed material is extracted from the stockpile by two belt feeders (one operating, one standby) and fed to an 8 x 10 ft ball mill. The mill discharge goes to a high-frequency screen with 1.6 mm openings. Coarse material (>1.6 mm) is sent to the pump drawer, while fines (<1.6 mm) feed two semi-continuous gravity concentrators, one operating and one on standby. Gravity concentrates are the final product, while tails go to the pump drawer. The cyclone nest (three D-10 cyclones, two operating) produces overflow at <106 μm for flotation and underflow returning to the ball mill, closing the grinding circuit.
Flotation
Cyclone overflow enters a conditioning tank before rougher, scavenger, and two-stage cleaner circuits. The scavenger circuit has four cells of 1.5 m³ each. Scavenger concentrates combine with cleaner tails and return to the conditioning tank. Rougher, scavenger, and cleaning circuits each have dedicated forced air blowers.
Concentrate Filtration
Flotation concentrates are sent to a 10 x 10 ft holding tank, then pumped via two pumps (one operating, one standby) to a membrane filter press. The filter press discharges concentrate with a specific humidity, though the value is not stated in the source. Automatic samplers in the tails and final concentrate lines send samples to a chemical laboratory for gold and silver analysis.
Additional Services
Low pressure air is supplied by two blowers (one operating, one standby) for the flotation circuit. High pressure air for instrumentation is supplied by two compressors with one operating and one standby. Fresh water requirement is 11 m³/h, with remaining water from recirculation and run-of-mine contribution.
## Additional Interesting Data and Summary
The capital cost summary includes a concentrator plant at US$14.2M, tailings storage facility at US$2.6M, and facilities at US$3.3M. The estimated total CAPEX is US$25.9M, including US$3.4M contingency. Fresh water consumption is 11 m³/h, with the remainder sourced from recirculated water from the strainer, concentrate filtration, and run-of-mine water. The design criteria show a gravity concentrator capacity of 80 t/h each and a high-frequency screen of 1.2 m x 3.6 m.
## Key Processes
- Primary and secondary crushing with jaw and conical crushers
- Grinding with an 8 x 10 ft ball mill in closed circuit with hydrocyclones
- Gravity concentration using two semi-continuous concentrators
- Flotation with rougher, scavenger, and two-stage cleaner circuits
- Concentrate filtration with a membrane filter press
Source: Cisneros Mineral Resource Update & PEA , 2018, 2018.
Editorial Note: The source text is partially corrupted with placeholders such as […] and inconsistent table formatting (e.g., primary crushing table repeats headers). Plant capacity, annual operating days, and head grade are stated in the technical source; other details are derived from the same source.
Project website: Cisneros Mineral Resource Update & PEA, 2018
