PASTE & TAILINGS 2021
First gold production was reached in November 2019 and commercial production was achieved in February 2020 at Lundin Gold ’ s Fruta del Norte
First paste in Ecuador
Paterson & Cooke has been involved from the start in designing the paste backfill plant and system at Lundin Gold ’ s Fruta del Norte mine in Ecuador – Rob Brown , P & C Managing Director , Canada reviews the project
In five short years , Lundin Gold successfully developed the Fruta del Norte gold deposit into a world class mining operation ; the first of its kind in Ecuador . Overcoming several challenges along the way , first gold production was reached in November 2019 and commercial production achieved in February 2020 . The project has delivered many ‘ firsts ’ to Ecuador and the new paste backfill system is just one example where best-practice principles and state-of-the-art technology were used to meet technical challenges head-on and provide the best long-term solution for the mine .
Paterson & Cooke ( P & C ) was involved from the beginning and performed the trade-off studies , laboratory test work and engineering design to shepherd the backfill project through to a successful start-up in October 2020 . Starting with the paste plant location , it was important to get the operation as close to the top of the orebody as possible . This meant constructing the plant remotely from the mill , but directly over the orebody , in order to achieve the best possible paste backfill recipes , placed at the highest quality .
The test work was extensive and covered thickening , filtration , rheology , characterisation and strength testing . Crushed aggregate addition and all types of binder were considered .
In the end , the paste process involves classified tailings ( to remove excess slimes ), followed by thickening and pressure filtration , then dual stage mixing to generate the 100 m 3 / h + of paste needed to place tailings back underground and develop the geo-support needed to continue mining . The added investment in pressure filtration was required because of the unique properties of the fine tailings which made them difficult to dewater with traditional vacuum filter technology .
The plant is well instrumented with modern controls and equipment , including CCTV monitoring in areas of the plant and at every underground pour location . The operators rely on ‘ live ’ feedback from the instrumentation to react to changes in the materials or conditions and make adjustments when needed . The choice between a gravity pour or running the paste through the positive displacement pump is made for each pour in the
Engineering Department based on the location of the stope to be poured in the mine . P & C ’ s hydraulic model is relied on to estimate the line pressures and performance of the system during the stope design phase , when the paste recipe and pour method are specified .
The underground reticulation system was designed by P & C to handle the in-line pressures , the forces involved and the frequently changing pour points underground . A system of boreholes and permanent and temporary pipe direct the paste to each pour point under controlled conditions . Automated dump valves and realtime pressure monitoring add safety and flexibility to the system .
Management invested early in the training of operators and engineering resources to prepare for the eventual handover from construction to operations . Paterson & Cooke provided classroom and laboratory training as well as inthe-field training to operators during commissioning and start-up . The crews took to the process in time and developed confidence running the paste operation around-the-clock . Quality control is monitored by the mine ’ s own civil technicians in the paste laboratory built on site for this purpose .
The underground reticulation system was also designed by P & C
The P & C designed paste plant
Commissioning ran in two phases due to an interruption from the COVID-19 pandemic , but the paste plant was started up successfully in October 2020 and has been ramping up production and fine-tuning the recipes , including a switch to high-early cement to generate strengths quicker . The paste plant was designed with expansion and redundancy in mind ; a second paste pump is on order to support the latest aggressive growth plans being undertaken at the mine .
IM
JULY 2021 | International Mining SUPPLEMENT P13