FILTRATION
As mine throughputs get bigger , they are typically grinding finer as the head grades are lower , so then it requires more driving force to dewater it in the filter press , says FLSmidth ' s Todd Wisdom
as designing the FP with sufficient clearance to lift out the plates and discharge the filter cake and get it away from the filter fast enough . Power in terms of kW / t doesn ’ t really change compared to a smaller filter as the terminal pressure remains 15 bar as you scale up , it ’ s how you distribute that energy across a huge plate . For all these reasons we built our demonstration unit in Tucson which has the largest pressure filtration plate ever put into service .”
This EcoTails ® 5 x 3 filter will be the world ’ s largest when operating , but the fact remains that the largest operation running today with a filter press is the 30,000 t / d Karara iron ore mine in Australia . Despite the fact designs for huge filter presses have been around for some time , companies are hesitant to install what they may see as an unproven size , even though the technology has already been proven in pilot and demo operations , plus the fact that these projects involve very low head grades , so they can ’ t spend as much money per tonne as a high grade metals mine to process the tailings .
“ But if they want to achieve filtered tailings at these volumes , there is no alternative to the large vertical filter presses , so it is a question not of if but when these projects will start getting off the ground .” Today these big copper and iron ore mines are either using some kind of paste or other thickened tailings solution or in many cases just disposing of the tailings in a wet TSF but this approach is becoming increasingly unacceptable with global mining companies ramping up the bar internally as to their own tailings management standards , plus the ICMM ’ s Global Industry Standard on Tailings Management . By reducing the volume of tailings through filtration , the TSF footprint can be significantly reduced .
There are at least five copper projects of
100,000 t / d and up in Peru and Chile alone with studies underway looking at filtered tailings , which all involve retrofitting of filtration to existing operations . “ A lot of this is being driven by the water issue in their arid regions just because saving water with filtered tailings is preferable to the huge costs of using desalination water that can cost $ 5-8 per cubic metre once you get it up to the Atacama from the coast . To give you an idea at $ 3 per cubic metre of water a big tailings filtration plant will effectively pay for itself .”
Diemme mastering fast filter pressing
Diemme Filtration , part of Aqseptence Group , says its GHT-F Filter Press is a system designed in particular for dewatering of fast filtration tailings and due to its features and benefits , is rapidly becoming the standard . Dan Stenglein Sales Manager USA says : “ There are currently many GHT-F filter presses in operation dewatering various tailings all over the world with our largest multi-filter installation dewatering more than 25,000 t / d of material .” Big Diemme Filtration projects have included Kupol gold mine in Chukotka , Russia ( 4 × GHT2500 . F20 , 830 m 2 each ); Real del Monte gold / silver mine in Pachuca , Mexico ( 4 × GHT2500 . P12 , 1,150 m 2 each ) and a bauxite residue dewatering and stacking in Western Australia ( 6 × GHT2500 . P18 , 1,750 m 2 each ).
The GHT-F filter press is what Diemme calls its proven " fast " filter press . The heart of the filter utilises an electrically-driven moving head to open the filter plate package , discharging the filter cake in about one minute . This system considerably reduces both the cake discharge time and the entire opening-closing sequence of the filter . The result is a fast cycling filter press which allows increased throughput per unit area of the filter .
The " fast " filter , however , wouldn ' t be fast if the rest of the filter cycle were slow . So , Diemme says
it has designed the filter plates to fill quickly using two large feed ports and multiple filtrate outlets to provide free and unrestricted filtrate flow . The result is a filter plate with high dewatering efficiency .
“ A major feature of our GHT-F is the integrated high-pressure cloth washing system . The onboard cloth wash system uses 50 bar water pressure to regenerate and extend the life of the cloth while the cloths are installed on the press . The frequency of the cloth washing is adjustable by setting the parameter on the PLC ; in this way the client can optimise the system for their process conditions . Since the system is entirely automatic , it is guaranteed that the cloths will be periodically washed . The benefits of this system are fewer cloth changeouts , less downtime , less maintenance costs , improved filtration efficiency of the cloth and extended cloth life .”
With the GHT-F design , filter cloths are " hanging " on the top of the filter plate and are easily accessed using the integrated platforms . To replace a cloth , it simply needs to be lifted out of the filter press ; there are no snaps , zippers , ties or other fastening hardware to remove or install . Furthermore , multiple cloths can be removed at once using a provided cloth removal tool . This reduces the time needed for cloth changing meaning more on-line time dewatering slurry . Up until now , the GHT-F was available in two filter plate sizes , 1,500 x 1,500 mm and 2,500 x 2,500 mm . But with the current and forecasted demand for even-larger throughputs of future tailings applications , Diemme is now releasing its GHT5000F ( nominal plate size 5,000 x 5,000 mm ). This huge , next-generation filter press will have more than 3,000 m 2 of filtration area making it the largest in the world . The first unit will be delivered in 2021 to an operator in South America for copper tailings dewatering .
Depending on the nature of the tailings to be dewatered , one GHT5000F can exceed capacities of 12,000 t / d of solids throughput so an operation running three or more of them would be larger than any filtration plant operating today in throughput terms . Built upon the successful GHT-F platform , this technology was years in the making overcoming design obstacles such as manufacturing and transportation limitations . “ The filter plate design itself results from our experiences coupled with computational fluid dynamic modelling and material engineering . The filter plate then went through extensive testing to further optimise the final design . The body of the filter plate is manufactured by injection moulding and consequently a new plate mould had to be created .”
To reduce the amount of weight and steel utilised , FEA was done over the entire structure . In addition , a topological optimisation was performed resulting in increased mechanical performance with less material .
Lastly , the GHT5000F , as well as other GHT-F filters , will have upgraded control systems using advanced machine intelligence and control . Tablet-
40 International Mining | OCTOBER 2020