FILTRATION & THICKENING
cake washing liquid ratio by volume to the dry cake is very low so we can do the washing very efficiently . In some cases , we can get the chlorides typically from > 20,000 ppm down to < 50 ppm . This is on top of getting moisture levels down to less than 10 %, typically 8-9 %.” There is a recent project in Chile where the customer is using seawater as the process water , after washing the cake with minimal fresh water to achieve the desired chlorides level ..
Foster adds on horizontal versus vertical plate filters in tailings duty : “ It depends on whether you are talking about mid-size or mega size volumes . The mega size tailings projects mainly use vertical plate filters such as our Larox FFP3716 filter which can handle up to 14,000 dry t / d . And in the mid to large size , where you are talking about 300-1,300 m 2 of filtration area , the vertical plate filters can be used for metal concentrates as well – we are delivering vertical filters for iron ore concentrate applications for example . In design terms , the PF has one continuous cloth – whereas vertical plate filters presses have mutliple cloths , which brings different attributes to each design and operation . Another key difference between vertical and horizontal plate filters is that horizontal plate filters can achieve up to 1 % or 2 % lower moisture but the vertical plates filters are capable to handling much higher slurry volumes .”
The filter selection process involves the
customer telling Metso it has a certain volume per day of slurry per day from which it wants to produce a certain number of tonnes per day of cake with a specified final moisture content due to TML – transport moisture limit . “ This is normally enough to being to narrow down the most suitable filtration technology . Then we always do slurry testing to get the exact results to be able to recommend a particular filter . We also give performance guarantees on tonnage and moisture level – if we don ’ t hit those , then we would be subject to liquidated damages which would have been specified in the contract . But we would never offer a PG without having done our in-depth slurry testing . to know exactly how the slurry will behave ."
As we speak , Metso is in the final stages in developing something totally new for PF 60 to help to lower air and energy consumption thanks to various design elements of the plate packs , piping , process control and the fluid dynamics . “ We are piloting and all the initial results are very good , so well aligned with our Planet Positive strategy , but we are gathering and verifying as much data as we can before we release more information on
this in Q1 2025 . Ultimately we hope to be able to give PGs on energy and air consumption .” Foster says Metso has PF 60 prototype filters out in the mining industry performing extremely well .
Diemme Filtration on the up
The GHT2500 remains Diemme Filtration ’ s top selling model in mining and new installations continue of this unit around the world . To take Indonesia as an example , Diemme is starting up a new plant with two GHT2500F-30 ( the 30 denotes the maximum length of the beam ) filter presses to process about 500 t / h of gold tailings . Andrea Pezzi , Diemme Filtration Director
Two new filter presses of model GHT2500F have been commissioned at Pan American Silver ' s Huaron mine in Peru where they will treat zinc tailings from the mining process , with a capacity of about 4,000 t / d . This image shows the final stages of installation
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THDO 5000F IN O OML
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24 International Mining | OCTOBER 2024