COLLAHUASI BOOSTS AVAILABILITY OF ITS VPA FILTER
Faced with increased production demands, Compañía Minera Doña Inés de Collahuasi had the goal of increasing both the availability and performance of its vertical plate pressure filters (VPA) in Puerto Patache, which were becoming outdated after more than
In collaboration with Metso, Collahuasi developed an upgrade plan based on using state-of-the-art technology; the desired objectives were met and resulted in a 15 per cent increase in filter availability.
THE project was carried out at Collahuasi’s mine in northern Chile, about 180km southeast of the port of Iquique, at an altitude of 4400m.
This mining district has been in business since 1880 with the exportation of high-grade copper-silver vein systems.
Currently, it is dedicated to the extraction and production of copper and molybdenum concentrate.
During 2016, Collahuasi was the third-largest copper operation in the world and has one of the largest deposits of mineral resources of copper on the planet (9.964 million tonnes). Its shareholders are Anglo American plc (44 per cent), Glencore (44 per cent) and Japan Collahuasi Resources B.V. (12 per cent).
Collahuasi was facing the great challenge, common to many global mining groups, of optimising its operations to achieve the highest levels of efficiency.
“In order to ensure productivity and profitability in the future, Collahuasi has decided to develop a preventive maintenance improvement program, which is comprised of a master plan to maximize availability and minimize bottlenecks, through a long-term and sustainable approach. Its objective is to detect potential problems in advance and maximize the performance and availability of existing equipment,” Collahausi vice president for processes Dalibor Dragicevic said.
In addition to the VPA filters, Collahuasi also has other equipment from Metso such as semi-autogenous ( SAG) grinding mills, ball mills, and Vertimills.
Ageing equipment poses a challenge
Thanks to the collaborative relationship between Collahuasi and Metso, a joint diagnostic meeting was held to review the main needs and potential improvement to the filtrate-concentrate level, which was related to the requirements of its VPA vertical filters to increase their production capacity while also increasing the overall reliability of the system.
Due to the high productivity requirements and over 20 years of use since its installation, the filters were showing a high degree of wear and misalignment, which reduced their availability due to the extra maintenance required by the filters and considerable unplanned downtime.
During the review stage of the overhaul, a joint decision was made to improve and upgrade the control systems, lubrication and structure of the equipment in order to achieve higher levels of availability.
Equipment refurbished to as new condition
The challenge for Metso resulted in upgrading the control systems to the latest technology, achieving values of over 92 per cent availability and 100 per cent of design capability.
This involved reinstalling and upgrading equipment in less than 20 days to minimize lost production.
The engineering coordination, parts procurement and planning activities began six months earlier in order to ensure the complete compatibility and successful outcome of this upgrade.
Comprehensive technological solution
The extensive upgrade of the equipment involved multiple steps. The Metso team first proposed improving the original design capacity by updating components and systems to produce some important benefits.
For this, Metso focused on the main problems that were causing the structural misalignment of the filters. In order to solve the structural problems, the filter was completely disassembled and over 80 per cent of its parts were replaced with new parts using a nanocoating technology for corrosive environments.
Using this approach would double the lifespan of the key parts and components and reduce potential downtime.
In order to achieve the optimal selection of fabric, a pilot filter was implemented at the worksite to take samples of concentrate. The samples were then used to help define the proper fabric for the filtering process given the specific mineral conditions that Collahuasi was processing.
In many situations, these types of tests involve using Metso laboratories located in Brazil and Finland. However, with the pilot filter on site, it was possible to perform all the tests in situ with the client, improving the selection and making it easier and quicker to get the results.
Another technological improvement introduced was the implementation OCS-4D, an advanced process control solution.
The solution assisted in determining the optimal control modes through analyzing the interplay between the selection of fabrics and maintenance events.
Finally, the chute was also examined for possible improvement opportunities. As the VPA filters discharge the filtered material (cake) into the chute, it was subjected to high rates of wear, causing a reduction in performance. Various designs and options were examined to improve ease of maintenance and thus reduce downtime.
“Searching for a design that improved maintainability, we implemented new, modular design upgrades to the chute, so that it could receive maintenance section by section,” Minerals Process Equipment manager Alejandro Bravo said.
“Thus, when a specific part shows signs of wear, we can disassemble that part and change it quickly.
“This is also an improvement that was tailored for the client, given that with the original design we had to disassemble the entire equipment to be able to change some parts.”
Expanding the project
Given the success of the project, Minera Doña Inés de Collahuasi SCM is evaluating the implementation of the same upgrade concept in other VPA filters as part of its asset management plan.
“With this solution, we have been able to meet some of the availability goals we set for 2017. The filter today works according to the plans drawn up with Metso, which helps us to continue operating efficiently,” Collahausi Symptomatic Process senior engineer Cristián Barros said.
Changing the plates of the filter.