FILTRATION achieve the lowest possible Total Cost of Ownership over the life of their filtration equipment , Venäläinen broke this down into three areas . “ First of all , the spare parts – as our OEM spare parts are designed specifically for the filters . For example , the diaphragms – we have over 30 years of experience in how to design and manufacture them . Its not just about the physical shape and geometry , its about the rubber compounds and knowhow , all these combine to create the lifetime . Secondly you need to have the right filter maintenance practices in place so you aren ’ t over or under maintaining the equipment & have a sound preventative maintenance approach ; and here digitalisation plays a big role , as mentioned . Third is making sure you have trained and certified operators and maintenance crews , where they really know what is the best and optimal way to operate the filters & the correct way to carry out maintenance . If you operate the equipment in the wrong way it can have a huge cost impact .”
He added : “ Regarding parts of course we do have some customers that want to reduce short term costs and look to alternative sources for parts but more and more mines are looking for a reliable partner for the life of the equipment . And non-OEM parts make it more difficult for us to make capacity and performance guarantees if we are doing the maintenance and having to use parts where we have not been involved in their
design or manufacture . It can even be regarded as a huge safety risk .”
Metso Outotec is also introducing a new Filter Optimizer application to help improve pressure filter performance in mining processes . “ The game-changing Filter Optimizer improves the performance of pressure filters by enabling more precise control over the solid-liquid separation process . The application stabilises the effect of upstream process variations , provides tools for improved process control , and reduces the need for manual intervention .”
Scaling up
In terms of filtered tailings projects , there is a lot of activity with projects being bid and sold regularly . FLSmidth Director of Tailings Solutions , Todd Wisdom told IM that these are typically systems dealing with up to about 15,000 t / d which includes many gold , platinum and other high value metallic mines that have tailings . “ The size of existing equipment fits these projects well , everything is fairly well understood and known at that scale . Also , being precious metals mines , they are making a lot more revenue per tonne , so there is more spend available to divert to the tailings part of the project . Typically , they will use two or three operating filter presses with one spare for maintenance and risk avoidance reasons .”
Above 15,000 t / d there is really a market gap , as there aren ’ t a lot of 30-40,000 t / d projects – there is a jump up to the big open pits that are 100,000 t / d plus – and these are mainly copper and iron ore mines . “ Then you are talking about really big filter presses like in FLSmidth ’ s case our Colossal™ automatic filter press ( AFP ). Our Colossal™ demonstration unit which successfully operated at a large copper mine in Chile has plate dimensions of 2 x 4 m but we also have a 5 x 3 m design for which a full-scale demonstration plant has been designed by Ausenco , with 160 chambers . A lot of work including FEA of the filter frame and plate design , computational fluid dynamics ( CFD ) of the chamber filling process & full-scale testing of the plate and cloth washing system has gone into this .”
While the fundamental principles of a big filter press are similar to a smaller filter press , as mine throughputs get bigger and they are typically grinding finer as the head grades are lower , it requires more driving force to dewater the tailings . “ Then you have to work out how to fill the huge plates – our 5 x 3 model has 15 m 2 of area to fill with a 50 mm depth filtercake . How do you distribute the slurry evenly throughout that plate chamber using filter feed pumps that can deliver high volumes and high pressures at different times through the filter cycle ? How many feed ports and where are they located ?”
FLSmidth has spent a lot of time and money getting this right . “ We also had to resolve plate handling issues with these huge machines , such
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