Copper Mining: From Exploration to Production
Exploration Stages
Basic Navigation
In this first stage, a general reconnaissance of a large area (tens to hundreds of kilometers) is conducted to identify favorable characteristics that may indicate the presence of a copper field.
Intermediate Exploration
The objective of this stage is to confirm the existence of copper mineralization at depth, based on the information collected in the previous stage.
Advanced Exploration
This stage determines more precisely the shape and extent of the deposit and the quality of the ore found, i.e., the ore grade for the content of copper or other elements of interest.
When to Decide to Mine?
The decision to proceed with the proposed mining operation takes into consideration the characteristics of the site, the design of the operation, and future projections of the international copper market (demand and price). Once it’s demonstrated that this is a business with attractive profitability, the next stages, corresponding to engineering, can proceed.
Safety Issues in Geography and Topography
Human Safety
- Safety Glasses: We recommend using safety glasses, since hitting rocks can cause small pieces to leap and cause damage.
- Food and Drink: Field reconnaissance work includes walking for several hours, so it is important to bring food and water.
- Clothing: It is advisable to wear light clothing, sturdy shoes, and sun protection items. It is important to remember that in some areas the temperature can change abruptly.
- First Aid Kit and Lantern: These are essential for any field work.
Equipment and Instruments for Measuring and Recording
- Maps of the area where the study is conducted with the identification of paths. Carry maps, photographs, and satellite imagery along with GPS equipment.
- Compass (required for orientation)
- Geological hammer
- Magnifying glass
- Measuring tape to make the necessary measurements
- Materials for sample collection: Bags, pencils, and tags for labeling samples.
Ore Extraction in Open Pit Mining
Open Pit Mining
The objective of this process is to remove the portion mineralized with copper and other elements from the solid rock of the mine (which can be open pit, underground, or a combination of both) and send it to the processing plant.
This type of extraction is used when the deposits have a regular shape and are located on or close to the surface, so that the sterile material that covers them can be removed at a cost that can be absorbed by the exploitation of the mineralized portion.
How is Ore Extracted in Open Pit Mines?
Drilling
Holes are drilled in the bench at regular distances from each other, usually between 8 and 12 meters (hole mesh), traveling through the entire height of the bench. This allows for the introduction of explosives, which, upon detonation, fragment the rock.
Blasting
An electric detonator is introduced into each hole loaded with explosives, which is detonated by remote control. This provides a sequence of detonations between individual holes of a blast, so that the rock is broken in stages based on the exposed face of the bench, with time differences of fractions of a second between each detonation.
Loading
The blasted material is loaded into large trucks by giant electric shovels and front loaders. These teams fill the trucks in a continuous operation from the bench after the blast.
Shipping
Heavy trucks, for example, 240 or 300 tons, are used for the transport of mineralized material and sterile. They transport the material from the loading front to their different destinations: the high-grade ore to the primary crusher, the sterile material to dumps, and the low-grade ore to special dumps.
Safety Measures in Drilling
- Drilling must be carried out in accordance with existing rules and procedures.
- Personnel involved must have the technical training needed to perform their functions and a detailed manual for the operation of the equipment they work with.
- Operators should be provided with all personal protective equipment (helmet, boots, gloves, goggles, masks, etc.) and wear clothing and accessories that prevent them from getting caught on moving machine parts.
Safety Measures Before Starting the Machine
The operator should check the machine and verify the correct functioning of:
- Hydraulic systems (hoses, pumps) and electrical systems.
- Pressurized hoses, which must be properly secured, like all connections, both on the rig and on the drill rods and bits.
- Signs and warning labels, which must be inspected to verify all directions, signals, or warning labels of the drill, for example, low oil level or a damaged bit.
Safety Measures During Startup
- Carefully review the workplace. In work closest to the slopes (open sky), consider, especially, the state of the benches and potential rockfalls.
- Make sure not to interrupt other duties within the mine, such as working with explosives.
- Verify that no person or other equipment (trucks) is in the workplace.
- Stay in your place of work and never leave the machine if it is in operation.
Safety Measures After Startup
The operator should:
- Check the correct functioning of all controls.
- Pay attention to unusual noises.
Safety Measures During Movement in Open Pit
- The area where drilling will take place must be in good condition for the smooth movement of the machinery.
- The operator must check that there are no overhead power lines or surface obstacles in the sector. If there is a wire or other foreign element near the drill, we recommend leaving a minimum safety distance of 10 meters.
- In case of moving the machine on a slope with a substantial angle (about 20 degrees), one must contemplate the possibility of securing the machine by lashing it with wires.
- Never climb the mast or derrick during removal.
- Never drill in previously perforated circular areas, as there is a risk of “clogging” the holes with debris.
Safety Measures in Underground Mining Work
- Always make sure that the roof of your gallery is safe enough. Be aware of loose pieces of rock (slabs) that could compromise the equipment or operator.
- Verify that there is the minimum required airflow in the work area.
- Verify the status of power lines, compressed air lines, and water lines if necessary.
- All drilling work should have appropriate lighting, using halogen bulbs.
Safety Measures During Drilling
- The drill needs to be stable, considering the instability of the ground. In this regard, hydraulic positioning devices should always be used before drilling.
- The elevation of the drilling mast should be done once the machine is level.
- The operator must always have optimal viewing conditions.
- Exercise caution when changing drill rods, especially with the immobilization mechanisms of drilling accessories (carousel, grips).
- Note the values indicated by the controls, in particular, record the depths of each well drilled and the drilling time for each of these.
- The operator should not be positioned under a rotary drill that is working when it is advisable to observe the tri-cone bit during ascent/descent into the drilling in order to detect any abnormalities.
- Operators should always be kept away from the components of the drill in motion, such as drag chains, cables, belts, etc.
- Do not bring your hands or touch the steel elements, as you run the risk of burns due to the temperature of these.
Safety Measures at the End of Drilling
- Never leave the machine with the engine running.
- Do not park the machine in potential flood areas or close to projections caused by rock blasting.
- Avoid parking the drill in sloping areas.
Crushing and Milling
Crushing
Ore from the mine has a wide particle size, ranging from particles smaller than 1 mm to fragments larger than 1 m in diameter. The aim of crushing is to reduce the size of the fragments to a more uniform size greater than ½ inch (1.27 cm).
Milling
By grinding, the size of the particles that make up the ore is further reduced to obtain a maximum particle size of 180 microns (0.18 mm). This finally allows the release of most copper from the ore in the form of individual particles.
Flotation
Flotation is a physical process that enables the separation of copper sulfide minerals and other elements, such as molybdenum, from the rest of the minerals that make up the bulk of the original rock.
Safety in Crushing and Grinding Plants
In almost all large mining projects, the crushing and milling plants occupy a lot of space and require increased energy consumption. Therefore, there is greater potential for accidents and/or incidents due to bad practices by workers.
Flotation is a physico-chemical process that allows the separation of copper sulfide minerals and other elements, such as molybdenum, from the rest of the minerals that make up the bulk of the original rock.
Magazine Features
- Any store or room designed to store explosives must remain closed and monitored by qualified personnel previously authorized and trained for this purpose.
Types of Magazines
Surface
Surface magazines are constructed at ground level.
Underground
Underground magazines are built in underground galleries and tunnels that have communication with other galleries in the mine. In general, they are intended for the temporary storage of explosives.
Buried
Buried magazines are those that are installed in tunnels or galleries without communication with other active underground workings. They can also be constructed in a dome covered with loose soil, with a proper roof to withstand the weight.
Mobile
Mobile magazines are installed on mobile transportation equipment, which move as operations progress. Their construction should be completely closed, non-combustible, covered internally with non-ferrous metal, and have access doors.
Magazine Safety Measures
Storage
- Explosive containers are placed in stacks of no more than ten boxes high, ensuring that they are not distorted. If the cardboard boxes located at the bottom become deformed, they should be stacked in smaller quantities.
In Case of Fire
Fire: “If a fire breaks out inside the warehouse or magazine, the alarm should be raised to alert any person found nearby to move to a sheltered spot, and the shift manager of the mine should be alerted. Never try to fight the fire yourself.
Smoldering Fire: When faced with a threat of fire, fire extinguishers located outside the magazine should be used. The combustion of ammonium nitrate can only be extinguished by cooling. For this, we use dry chemical extinguishers, foam, carbon dioxide, or water, as these are suitable for fire threats of class A, B, or C.
Inventory
Inventory Book: The magazine keeper must keep an “Inventory Book” which must be registered with the relevant Control Authority. It clearly notes the receipt, delivery, and return of explosives to the mine.
Access to the Magazine
- A minimum of two and a maximum of five people can enter the magazine at once.
- Only those who have a special permit granted by the task administration can enter these stores.
Handling Explosives in the Magazine
- Do not open drawers containing explosives in the magazine.
- Do not carry loose explosives in pockets or hands. This prohibition should be considered especially when it comes to detonators.
- If the cartridges are frozen, do not defrost them by exposing them to direct heat.
Casting Process: Pure Copper Ore
The dried copper concentrate, with a concentration of 31% copper, undergoes pyrometallurgy processes in furnaces at high temperatures. Through these processes, the copper concentrate is processed into copper metal and is separated from other minerals such as iron (Fe), sulfur (S), silicon (Si), and others.
Reception and Sampling
As it is common to work with concentrates of different origins, it is necessary to sample and classify them according to their concentration of copper, iron, sulfur, silica, and moisture content.
Fusion Process
The goal of fusion is to achieve a change of state that allows the concentrated solid to become liquid in order to separate copper from other elements in the concentrate.
Conversion Process
What is the Objective?
Through the conversion process, the products obtained in the fusion are treated to obtain high-purity copper. Conventional converters called Peirce-Smith, in honor of their creators, are used for this purpose.
Pyro-Refining Process
What is the Objective?
Through fire refining or pyro-refining, the purity of blister copper obtained from the conversion is increased. This involves removing the percentage of oxygen present in this type of copper, reaching specific concentrations.
Foundry Safety Aspects
Injuries, heat, chemicals, and other risks are important safety aspects to consider in foundry operations.
Hydrometallurgy Safety
The safety of leaching relates mainly to the observation of standards of care, handling, and use of sulfuric acid.
Sulfuric Acid Features
- It is an oily liquid, transparent and colorless in its pure form.
- It is a strong acid.
- If heated above 30°C, it will produce steam.
Worker Safety
- Use fire equipment.
- Use personal protective equipment.
- Use safety showers, eye baths, and water fountains.
- Use equipment and facilities to prevent steam inhalation and direct contact with the liquid.
- Use appropriate car and personal respiratory protection equipment.
- Use eye protection, head protection, foot protection, and body protection, including hand protection.