Codelco will soon commission the next great Chilean copper mine

By Oscar Martinez Bruna, Latin American Editor

The world’s largest copper miner, Corpración Nacional del Cobre (Codelco), has committed to building another world class mine: Ministro Hales. The Chilean state-owned copper company is investing a total of $3.1 billion—its largest mining investment ever. The project will extract copper from an orebody that contains more than 1.3 billion metric tons (mt) of ore with an average grade of 0.96% copper. When División Ministro Hales is commissioned later this year, it will yield an average annual production for the first five years (2014-2018) of 200,000 mt of fine copper and 350 mt of silver.

Construction on División Ministro Hales began in September 2010 and the orebody is still under development. The ore deposit was formerly known as Mansa Mina. It is located roughly 5 km north of Calama in the Antofagasta region. The project is named for Alejandro Hales, a former Chilean minister of mines. The investment and development strategy was based on a 36-month timeframe, followed by a start-up stage, scheduled to take place during the third quarter of 2013.

Although the operation begins as a traditional open-pit development over a period of 14 years, the business model applied by División Ministro Hales forecast a mine life of more than 50 years. And, if developed according to plan, the mine would also begin underground mining in year 50. Codelco is one of only a few mining companies that has such a long-term vision.

When it comes online, Ministro Hales will allow Codelco to maintain its production levels in the medium term. The mining and mineral processing techniques will yield a nice return on investment for Codelco as well as improving the company’s competitive position in the copper market.

When E&MJ visited the operation (February 2013), Paulo Delgado, Codelco communications specialist, said the overall progress of the entire project, both pre-stripping and plant construction, currently stood at 82%. “The pre-stripping involves mobilizing 288 million mt of overburden, and since April 2011, we have completed 76%. Today, the mine is moving around 240,000 mt per day.

“This progress is a result of unified work between División Ministro Hales and the project vice presidency of Codelco, the latter being in charge of building the plant facilities of the division,” Delgado said.

Community Involvement
The infrastructure at the south end of the open pit covers an area of approximately 126 hectares. The facilities will provide truck maintenance services, machine shop, lubrication pits, equipment washing bays, tire yard and warehouses, as well as management and engineering facilities: warehouses, contractor facilities, staff services and light vehicle petrol station. The design includes a neighborhood development close to the site.

“División Ministro Hales represents a joint effort of managers, employees and the neighboring community aimed to develop a world-class project, with new management models, the best practices in the market, state-of-the-art technology, and respect to life and environment as a first priority,” Delgado said. “This professional, collaborative and concentrated work will be done pursuing the respect for the life and dignity of everyone involved in the operation, which are considered essential values set by Codelco.”

División Ministro Hales tried to hire local manpower to complete every task. Calama is a copper mining community of about 150,000. Nearly 60% of Ministro Hales workforce has been hired from Calama and the surrounding areas, and around 70% come from the Antofagasta region. About 12% of the miners are women.

“The división has stated its strong commitment of growing together with the community and making this operation and business a great opportunity for the social and economic growth and development of Calama,” Delgado said.

For that purpose, the company has defined its relationship with the community as a shared, collaborative and communicated work that provides consistency and sustainability to the Community Development Plan set by the división. This plan embraces work streams associated with active participation of the community, education and culture, creation of new job skills development, wealth generation, profitability and social investment.

Developing a World-class Deposit
Ministro Hales will be the largest pre-stripping operation in the history of Chilean mining, moving more than 238 million mt of waste rock to construct the open-pit mine. Pre-stripping commenced in April 2011 and continues today. The open-pit mine plan calls for 370,000 mt/d of material to be moved by truck-shovel mining techniques. The ore will be processed in a stand-alone concentrator, whose design production is expected to be 50,000 mt/d, with the output material being fed to a primary crushing line and a SAG milling line, selective flotation through the use of oversized cells, a roasting process, acid plant and arsenic abatement. The concentrate and/or calcine will be toll-smelted to produce high purity copper cathodes. It also features an oxide processing line rated at 20,000 mt/d, and the solutions will be treated by conventional electrowinning in Chuquicamata.

The mining equipment itself will be a combination of Cat electric shovels and Komatsu PC8000 hydraulic shovels with dipper capacity of 100 mt and bucket capacity of 80 mt, respectively, loading 360-mt-capacity Cat 797F haul trucks, all utilizing the latest mining technology.

“By the end of the construction phase there will be six mining shovels and one supporting shovel (four shovels are currently operating), and 35 haul trucks, and we have 19 operating now. The mine will also employ four blasthole drill rigs, which are expected to drill 12.25-in. holes. Three of the drills have been erected. Along with the mining fleet there will be a supporting fleet of seven bulldozers, four wheel loaders, three motor graders and three watering trucks,” said Delgado.

The primary crusher, a 63 x 89-in. (1,600 x 2,260-mm), 1,341-hp ThyssenKrupp machine, will allow the mine to crush ore at a rate of 4,400 mt/h. The haul trucks discharge directly into the primary crusher and the dump zone area, which has been engineered as a confined facility to control dust emissions. The facility has a fairly sophisticated dust suppression system.

Mineral Processing
Ore passing the primary crusher reports to an 80-m long, 2.8-m wide conveyor, an ST 1800. It transfers ore to a 3- to 5-km-long, 54-in. wide (1,372-mm) wide overland conveyor, which dumps onto a 58,000-mt stockpile. The capacity for the entire material handling system is rated at 50,000 mt/d. To control the dust emissions, the overland conveyors feeding the stockpile will be enclosed.

Adding breakthrough technology in the mining processes and the overall operation is one of the concepts highlighted by División Ministro Hales in each one of its areas. This particular mine applies the latest technology available in the market for both the crushing circuit and the overland conveyor, and it is also remarkable in the control of dust emissions. All of the truck loading zones are confined and enclosed, with water nebulizer systems to abate dust particles.

“It is important to mention that since Ministro Hales is located near Calama, it will be necessary to maximize our dust suppression efforts in the crushing process due to sustainability aspects such as quality of life, which must be present in every phase of our operation,” Delgado said. “We are convinced that we are constructing mining for the 21st century.”

The heap leaching project for Ministro Hales includes a waterproof base static pile where nearly 600,000 mt of ROM ore grading 0.22% total copper and 0.13% soluble copper will be contained in three heap modules.

After passing through these ROM modules some in situ oxide (OIS) will also be placed in heaps. The grades identified for this OIS are 0.6% total copper and 0.3% soluble copper. The ore will be previously crushed in primary and secondary crushers to obtain a grain size between 0.75 to 1 in. (19 to 25 mm), and an acid curing should generate a 65%+ copper recovery.

The life expectancy for this heap is three years and the mine hopes to recover around 70,000 mt of fine copper coming from 21 million mt of ore heaped on four 8-m lifts. The solution obtained from this process will contain 4 to 5 grams per liter copper concentrations, and they will be transferred to a solution recovery plant at the neighboring Chuquicamata mine, to further join the SX-EW process and then obtain copper cathodes.

Copper concentrate, which contains arsenic, will be processed at a new roaster and will produce a calcine with a low arsenic content and high copper concentration. It will be processed to obtain a high-purity cathode in the smelter and refinery.