With a deep understanding of the Constancia project from having delivered an update of the feasibility study and front-end engineering services (in late 2014), Ausenco was well positioned to provide EPCM services to design, construct, and commission the 25 Mt/y concentrator and associated infrastructure for this high-altitude project. Our optimisation study, based on cost-effective design principals and a fundamental change in the layout, resulted in a net present value (NPV) improvement of US$800 million over the original feasibility study. The plant was delivered on time and on budget and has operated above nameplate capacity since 2015.
The Constancia mine is a porphyry copper-molybdenum deposit located 4,100 m ASL in south-eastern Peru. Working closely with original owners Norsemont Mining (and subsequent owners Hudbay), our team was challenged to complete an optimization study and implement new operational designs that would minimize capital and operating costs without compromising safety, operability, and maintainability.
The Better Way
Ausenco identified several opportunities for design changes that would help increase capacity and lower capital costs, including optimising equipment selection and significantly improving the construction schedule.
Plant throughput at Constancia was constrained primarily by ore competency. We performed a number of trade-off studies to determine the arrangement of mills in the grinding circuit that would provide the greatest throughput, even as percentages of hypogene ore in the plant feed varied over the life of the mine.
In our search for a better way, engineers drew on successful design concepts originally developed for smaller gold projects. These designs had previously been applied to the development of large copper concentrators, including the 12 Mt/y Phu Kham and 20 Mt/y Lumwana copper concentrators. The original layout was modified to reduce plant footprint, minimize the use of fully-enclosed buildings, reduce the height of structures, optimize the location of sub-stations and motor control centres, and allow for the use of tower cranes to support construction and operations. A construction execution plan was tailored to suit the Peruvian construction industry and the challenging site altitude of 4,100 m ASL.
With a 50% smaller physical footprint than the original layout, bulk materials quantities (steel, concrete, piping, cable) and the CO2 footprint were all significantly reduced. As a result, the project saw a 35% reduction in concrete per MW of installed mill power and 25% higher grinding capacity on the hypogene ore versus the feasibility study.
By finding a better way, Ausenco transformed this low-grade copper mine in a challenging, remote location into a safe and productive long-term operation. Innovative design concepts developed by our team ensured the plant could be built quickly and cost-effectively.
Plant throughput averaged 80,000 t/d in the early years of production, well above its nameplate capacity of 76,000 t/d and continues to operate above these levels.
Over the construction phase, more than 8 million person-hours on Ausenco managed scope had been carried out without a Lost Time Injury (LTI).