THICKENERS AND FILTERS
DELKOR by design
IM spoke to Mark Taylor , Sales & Process Support , TAKRAF Australia about the thickener market and the strengths of the TAKRAF DELKOR offering
Q To those not in the industry , large high-rate thickeners in mining all look very similar – what are some differentiators ? A The high rate thickener is now a mature product where the overall design of the major suppliers are very similar and difficult to differentiate . There are aspects where each supplier is different and these include the drive and in particular the feedwell . Improved access to computational fluid dynamic ( CFD ) programs over the last 15 years has allowed each vendor to optimise the feedwell design . Key aspects include improved particle distribution within the thickener and superior flocculant interaction . The designs of each vendor ’ s feedwell does vary markedly but the distribution and flocculant efficiency is likely to be very similar . There are no longer any ‘ bad ’ feedwell designs in the market .
Q What does the TAKRAF DELKOR design offer that you would say makes it distinctive or unique ? A The main thickener suppliers had all been part of the AMIRA P266 “ Improving Thickener Technology ” study that has been ongoing for 20 + years . This study focused on feedwell design and effective flocculation and is without a doubt the most comprehensive study on the subject .
The DELKOR design used the recommendations to offer a feedwell that would work efficiently in variable feed conditions – our experience is that mines will present different flowrates , particle sizes and solids loadings over the life of the thickener . We also have a team to carry out testwork at our own laboratories or site .
Q A lot is being said about bolted thickeners offering faster assembly , lower cost etc - is it true that this approach is becoming more common ? A In the Australian market it is almost exclusively bolted tanks and this is very much being replicated in most markets worldwide . The advantages of completing all the welding and painting under controlled measures in a workshop give a financial saving , shorter construction time and most often a quality advantage . There isn ’ t a site that doesn ’ t want to limit site labour and reduce build time and bolted tanks achieve this . The only disadvantage is the transport of much larger pieces and costs associated with this .
Q Is the move towards filtered tailings in large volume projects meaning less or more demand for high-rate thickeners ? A Thickeners assist in water recovery which is becoming more and more critical in many industries . There has not been a significant increase to high rate thickener demand at this point in time . However , we might expect with increased public scrutiny that government legislation will likely result in a surge of dewatering applications in the very near future .
compared to HRTs . These include overall tank dimensions , floor slope , internal mechanism design , and drive torque . HDTs can generate yield stress , non-Newtonian underflow .”
Among the benefits of an optimised thickener package are the reduced water in the filter feed that yields a shorter cake form time . “ Modernisation of the feedwell and control make the thickener significantly more economical and has the potential to reduce the water sent to the filter . The impact of the thickener type has a more profound effect on filter ’ s efficiency . The use of a HDT thickener , which produces 10-15 percentage points great wt % solids , send as much as 50 % less water to the filter . Form times have been shown to be 35-50 % sorter when fed by the HDTs underflow . Through this improved form time , the filter capacity be increased . For installed filters this would greatly reduce the bottleneck issues so often experienced .”
McLanahan - different options for different situations
When it comes to tailings management , McLanahan argues that the best equipment for one site may be different than the best equipment for another site . “ Decanter centrifuges , belt presses and filter presses are all suitable choices for pond reduction / elimination , so the best one depends on the tailings management goals of the site . The main thing to consider is the type of material being dewatered .” It says that decanter centrifuges work best with material that has a larger particle size distribution and is more easily dewatered . They are also ideal for material with low clay content , and they are less sensitive to changing feeds . “ Belt presses can be used to dewater a variety of different slurries in a wide range of applications , but they don ’ t perform well with varying feed conditions . Filter presses are ideal for dewatering tailings from mineral and aggregate wash plants , mineral concentrates and most underflow slurries coming from a thickener or clarifier . However , the feed % solids and particle size distribution do have an effect on the overall dewatering efficiency of a filter press .”
IM
OCTOBER 2022 | International Mining 23