THICKENING & FILTRATION
Installation of filter plate on one of four Jingjin dewatering filter presses at Polyus ' s new Nezhda gold mine
dewatering of the concentrate containing silver , a filter press of a similar configuration with a filtering area of 50 m 2 has been supplied .
The chief installers of the RIDTEC company are now in Yakutia at the Nezhda plant site carried out the installation of this equipment in May / June 2021 . This is not the first experience of RIDTEC supplying JingJin filter presses to Yakutia . In 2012 , filter presses were supplied to Seligdar Gold , “ where JingJin equipment showed high reliability ,” despite the harsh climatic conditions . The filter presses are still running with no issues . The commissioning of the plant at the Nezhda and the first production are planned in the 4th quarter of 2021 . This is one of the largest projects of Polymetal in Russia .
Nezhda ’ s estimated Proved and Probable Ore Reserves are 4.4 Moz of gold equivalent at an average grade of 3.6 g / t . The project includes an open-pit and underground mine , and a conventional on-site concentrator followed by concentrate processing at the Amursk POX and / or 3rd-party off-take . This ensures low capital intensity for the project . It will produce 155,000-180,000 oz per year until 2045 .
Not forgetting disc filters
In the right application – disc filters retain a key role in tailings management . FLSmidth vacuum disc filters as an example are playing a vital role in preparing tailings slurry for a backfill application at the new Kamoa-Kakula copper mine in the DRC . The Kamoa-Kakula Copper Project is a joint venture between Ivanhoe Mines ( 39.6 %), Zijin Mining Group ( 39.6 %), Crystal
River Global Ltd ( 0.8 %) and the Government of the Democratic Republic of Congo ( 20 %).
According to Maria- Paula Lucero , Sales and Account manager at FLSmidth , the company supplied four 3.8 m diameter disc filters , each comprising 14 vacuum discs . They are installed in two modules , with two units in each . This provides a cost effective dewatering strategy resulting in a cake dry enough to be mixed with cement and other additives before being conveyed underground to be placed in mined-out workings as backfill .
“ The efficacy of the vacuum filter in this application allows the mine to consistently achieve its targeted level of dewatering ,” says Howard Areington at FLSmidth . “ This , in turn , means that the amount of cement and additives can be optimised , keeping operating costs down .” Areington highlights that vacuum disc filters are the preferred technology for tailings dewatering in backfill applications , being the most cost effective form of vacuum filtration per square metre of footprint .
A range of ancillary equipment was provided as part of the scope of supply , according to Lucero . This included the liquid-ring vacuum pump with capacity to pump almost 15,700 m 3 / h at a pressure of 67 kPa , as well as filtrate receiver and a filtrate pump of 32 m 3 / h capacity . FLSmidth also supplied a 1,060 gallon snap air receiver , a 750 kPa air compressor , a plant air receiver and an air drier . The water used in the filter vacuum pump needs to be potable so it was important for the design to recycle as much as possible . It is therefore recirculated through a closed circuit , with a cooling tower added to dispel heat from the water before it is reintroduced to the system .
“ With disc filters delivering a drier product with more water savings , FLSmidth has provided this technology to many projects around the world ,” says Areington . “ With FLSmidth ’ s global reputation in the field for vacuum filtration backfill applications , we have secured a significant portion of this market – also supplying some of the largest vacuum disc filters in use today .”
A considerable portion of the disc filter installation was locally manufactured in South
Africa , he notes . It was shipped in components to site , and installed by a third-party engineering company under FLSmidth supervision . Despite the challenges presented by the COVID-19 pandemic , the units were manufactured and delivered within a timeframe in line with the customer ’ s expectations .
Over in Brazil , Vale is gradually starting up operations at its new tailings filtration plant at the Vargem Grande Complex , this being the first of four filtering plants that will be installed in Vale ’ s operations in Minas Gerais , totalling a $ 2.3 billion investment between 2020 and 2024 . In addition to reducing the need to use dams , being replaced with dry stacking , the start of operations will allow an improvement in the average quality of Vale ’ s product portfolio with the use of wet processing on the site .
In the filtration process , the water present in the iron ore tailings is reduced , allowing most of the material to be stacked in a solid state , thus reducing dependence on dams . Still in 2021 , it is expected to start the operation of the first filtration plant in the Itabira Complex . Over the course of 2022 , the second filtration plant at the Itabira Complex and the first at the Brucutu site will start operating . The four tailings filtration plants will serve processing plants that total a capacity to process 64 Mt / y of iron ore .
The addition of 4 Mt / y of capacity , as previously announced in the Production and Sales Report , on February 3 , 2021 , will take place from the 3rd quarter of 2021 along with the start-up of the Maravilhas III dam , which is in the final stage of construction and will receive only the ultrafine tailings from the plants , equivalent to approximately 30 % of the total tailings generated from this operation . The beginning of the tailings filtration operations in Vargem Grande is another step in stabilising iron ore production and on the way to the return of the production capacity of 400 Mt / y at the end of 2022 , says Vale .
The planned Vale operations mainly include thickeners and filtration plants using vacuum disc filters . In the process , the tailings go through the thickener generating a thickened slurry to be then pumped to the filtration plant . The tailings are filtered in a vacuum disc filter made of filtering cloths connected to a central vacuum system . The filtering cycle occurs as the disc rotates . When the filter is immersed in the slurry sump , the water is vacuumed up and particles accumulate in the cloth to form a cake . The filter is then removed from the sump and any liquid remaining is vacuumed up . Lastly , a jet of compressed air releases the cake and the material , now with reduced moisture , is discharged on a conveyor belt . The tailings are disposed and stacked in layers to minimise the tailings area , with the potential for revegetation . IM
22 International Mining | OCTOBER 2021