PASTE & TAILINGS 2021
The customer recently requested a third thickener of the same type and diameter , so FLSmidth was challenged once again to take its design to the next level
increased thickener diameters , which subsequently increases the required or installed torque . While peripheral traction drives for largesize thickeners were the first to reach a torque of 10 Mlb-ft of DRT , these drives are not always ideally suited to the application or thickener configuration , especially where the intent is to use multiple thickeners of the same size and with elevated steel tanks .
“ In response to the needs being dictated by the market , we developed the C140 series of centre ( column / cage ) drives , where we use up to six ( 6 ) sprockets / pinions ( C140P-6 ), with the original intention of reaching a torque of 10 Mlbft – equivalent to the traditional traction drive . The 20 Mlb-ft rake design in the peripheral traction thickeners has allowed us to develop and gain the necessary experience to design and manufacture robust mechanisms that can easily handle a drive torque of 10 M lb-ft – and significantly higher – for the rake arms , etc , as was proven with our 20 Mlb-ft design .”
As part of the continuous development process over the past three years , and in order to not only meet their needs but also contribute to increasing productivity for its customers , FLSmidth R & D engineers have used finite element analysis ( FEA ) and have applied the use of new materials to modify and improve the design of its C140P-6 centre drive with 10 Mlb-ft of duty-rated torque . The newly launched C140P-6-SD ( super-duty ) drive is designed for a DRT of 12 Mlb-ft , ( 16.2 MNm ). This drive has the highest torque on the market , and it is capable of achieving its customers ’ continuously increasing demands .
Additional improvements
In addition to drive developments , FLSmidth has also considered the ability of thickener raking mechanisms to move and discharge higher yieldstress material , leading to new design efforts in developing low-drag rake arms that have proven
critical to discharging high underflow densities . Rake replacement projects have shown that high-strength tubular rake construction can enable an increase in underflow density of 2 to 3 wt %, compared with traditional box-truss construction .
More recently , for very high-tonnage projects with a yield-stress discharge , it has developed a spiral inner rake blade design to greatly improve mud raking and discharge in the critical zone near the discharge drum
Spiral rake blades are a specific design of the thickener . These
feature on three 45 spiral rake blades are a m-diameter specific design feature
FLSmidth deep-cone paste thickeners on three 45 m- currently diameter being erected
FLSmidth on a project in Kazakhstan deepcone paste thickeners currently being erected on a project in Kazakhstan . Computational fluid dynamics ( CFD ) modelling shows this design reduces short circuiting and improves the mud bed residence time distribution .
Another noteworthy technology is the E- Volute feedwell , a simple and elegant solution to evenly distribute the flocculated feed stream from the feedwell into the thickener with minimal shear .
This advancement results in minimising the floc dosage while improving the overflow clarity . This has been proven effective on all sizes , from small to the largest applications , with feedwell diameters up to 20 m .
Then there is digitalisation . “ We have over 30 years of experience in providing automated solutions for minerals processing needs . Through KnowledgeScape digital optimisation , our automated thickener strategies can increase underflow density and decrease flocculant consumption in traditional , high rate and paste thickeners , and improve water recovery . Our strategies utilize all available data to effectively build and maintain adequate bed level , control rake torque and achieve target discharge density .”
An eye towards the future
With all of these developments over the past 25 years , FLSmidth says it has proven it can design and build the most robust and highestperformance high-density and paste thickeners on the market . “ As a core value , FLSmidth aims to improve the productivity of the mining business as a whole , and in line with this we continue to develop our thickening technology to meet the needs being expressed by our customers . High-density and paste thickening recovers substantially more water than other thickening methods , while still allowing the tailings to be pumped and distributed easily into the tailings storage facility . Maximising the density at the deposit minimises the volume required for storage .” Over the last three years , it has continued to engineer and supply large-diameter tailings thickeners into copper projects in South America , including the following high-rate ( HRT ), high-density ( HDT ) & deep-cone thickeners ( DCT ) under construction as of Q4 2020 : 100 m HRT ; 120 m and two 85 m HRTs ; 125 m HDT & 43 m DCT . Other copper tailings projects in the same timespan include two 125 m HRTs in China and three 45 m DCTs in Kazakhstan .
IM
The E-Volute feedwell evenly distributes the flocculated feed stream from the feedwell into the thickener with minimal shear
JULY 2021 | International Mining SUPPLEMENT P3