Sociedad Minera Cerro Verde (SMCV) operates an open pit copper mine near Arequipa, Peru, which is located at an elevation of 2,700 metres above sea level (masl).
Ausenco has provided services, directly and through agents, for the tailings handling, reclaim water and seepage water collection systems beginning with a feasibility study and continuing through to engineering services and expansion studies.
The system design includes a 3.9 kilometre (km), 48.0-inch diameter high density polyethylene (HDPE) launder with a 34 million tonnes per year (mt/y) throughput to deliver tailings from the thickeners to a cyclone station near the dam.
Tailings are classified in the station with cyclone overflow and then delivered to the impoundment and cyclone underflow for dam construction. The first stage cyclone system includes a 1km, 36-inch pipeline with throughput of 17 mt/y. The second stage cyclone has a 130 metre, 36-inch overflow pipeline with throughput of 16.7 mt/y and a 2km, 24-inch underflow pipeline.
The tailings handling system is designed to transport 37.4 mt/y of whole tailings from the mine site to the impoundment dam.
The reclaim water system consists of three impoundment barge pump systems, 36-inch and 42-inch diameter pipelines, associated pump stations and storage tanks.
This system supplies water to the mine site processes and to the tailings cyclone station.
The seepage water collection system consists of a 7.5km pipeline and pump station, which delivers water to the cyclone station water head tank.
In 2004, Ausenco performed a feasibility study for the proposed thickened tailings system as a sub-contractor for agent Fluor Canada Ltd. Our scope included laboratory testing, review of the current design, preliminary hydraulic calculations, and a report validating the selected system and providing recommendations.
From there, we went on to provide basic and detailed engineering, procurement, construction support, commissioning and start-up support services. These services were also contracted through Fluor.
Our scope included:
- Hydraulic design for the entire system
- Design of the tailings pipeline, water pipeline and launder
- Design of the cyclone station
- Design of the tailings distribution header and support structure
- Design of the equipment foundation
- Design of the pump station
- Design of the 1km, 16-inch Eastern Quebrada sand line
- Design of the Eastern Quebrada spray bar
- Operating and control philosophy
- Barge relocation sequence schematics
- Procedure manual for elevating support towers
- Review of facility construction
- Start-up support and training
- Operations commenced in 2007.
In 2008, we were retained by SMCV to perform a conceptual-level debottlenecking study to increase the tailings system nominal processing capacity from 37.4 mt/y to 41.6 mt/y.
Within this study, we performed hydraulic modeling based on six operating cases. The cases were a permutation of minimum, nominal, and maximum tailings production rates, combined with the scalping cyclone either operating or not operating.
Our analysis established that the existing launders were adequate for the increased throughput, but the increase would necessitate modifying dilution and distribution boxes; rubber lining feed pipelines; replacing cyclones; and installing a new flush line.
Our deliverables for this project included the design basis, PFD, cyclone simulation report and CAPEX.
In 2009, SMCV retained Ausenco again to develop an expansion study encompassing the useful life of the tailings system (until the year 2029) with consideration of changes due to dam growth and tonnage increase of the concentrator plant from 37.4 mt/y to 41.6 mt/y.
For this study, the life of the tailings system was divided into 3 phases:
- Phase 1: Period before the first cyclone station relocation (approximately 2 years)
- Phase 2: Period following the first cyclone station relocation through to the second relocation
- Phase 2: Period following the second cyclone station relocation
Our scope included basic and detailed design of the sand pump, and also considered the effects of the following:
- Potential size increase of sand header from 16 to 18 inches
- Valve spacing/zone on 18-inch sand header and spray bars
In 2010, in anticipation of future dam rises and an increase in tonnage to 41.6 mt/y, SMCV wanted to partially upgrade and relocate the existing tailings system.
Under direct contract with SMCV, we provided basic engineering for the installation of new first stage cyclones and the relocation of second stage cyclones (including associated civil, mechanical, electrical and instrumentation scopes) as well as the design of a new pumped water dilution and cyclowash system.