PASTE & TAILINGS 2021
An FLSmidth 125 m high rate thickener
The challenge expands
As a result of this success , between 1997 and 2001 the same customer requested that FLSmidth design the same thickener , but with an increased DRT . In response , FLSmidth offered a 125m-diameter thickener with a peripheral traction drive providing 10 Mlb-ft of torque . Due to the customer ’ s concerns that the high DRT could potentially damage the rake mechanism , the request included that the mechanism be designed for twice the rated torque of the drive . The outcome of this exercise was that FLSmidth designed and built three thickeners of 125mdiameter , all with E-DUC auto dilution systems and 10 Mlb-ft peripheral traction drives , but with rakes designed for 20 M lb-ft . More than a decade later , with continued successful operation of these three thickeners , the same customer expanded its operation , and again selected FLSmidth to supply an additional three thickeners of the same size and design to augment production capacity .
Thickener evolution : a testament to customer commitment
Tailings technology is not all about greenfield projects . A challenge from an FLSmidth customer 25 years ago has led to a number of evolutions in thickener design , addressing productivity , strength , dilution flowrates , underflow densities and water recovery
In 1995 , one of FLSmidth ’ s largest customers challenged it to design and build the largest traction thickener possible that would still be economically and practically feasible . In response , FLSmidth developed a peripheral traction thickener of 125 m-diameter , with a duty-rated torque ( DRT ) of 8 M lb-ft and the proprietary FLSmidth E-DUC ® auto-dilution system . Once in operation , this thickener and the feed dilution system proved to work so well that it processed 40 % of the total tailings produced by the plant , while the remaining 60 % was processed by four older thickeners of the same diameter . " We really appreciate the 25- year partnership we ’ ve had with this customer because they ’ re constantly challenging us to improve our designs and deliver the best
Large high-density thickener install thickening solutions on the market ,” said Francisco Reyes , FLSmidth Sedimentation Sales Manager South America / South & Andes Region .
New challenges , new solutions
As these upgraded thickeners continued to operate and perform well over the years , another large copper-producing customer requested FL Smidth provide a similar thickener design , but for a more complex type of copper tailings . In response to this request , FLSmidth built a 125mdiameter thickener , with a 10 Mlb-ft peripheral traction drive and 20 Mlb-ft mechanism design — but in this case , with FLSmidth ’ s proprietary P-DUC forced / pumped dilution system . The pumped dilution relied on four operating P-DUC pumps to achieve the high dilution flowrates . In addition , FLSmidth increased the slope of the tank floor . The thickener system demonstrated great efficiency in consistently achieving pulp dilution to a relatively low solids concentration in the thickener feedwell , which improved the flocculation and settling / sedimentation rate . It later constructed a second of these thickener systems , due to the customer ’ s plant expansion .
Then this 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 . “ Our response was to engineer and build a thickener that will achieve underflow densities at the limits between high rate and high density . It features a floor slope that is typically used in high-density thickeners ( 3:12 ), which gives it a depth of almost 20 m in the centre . Again , the thickener has a diameter of 125 m , an installed torque of 10 Mlb-ft and rake mechanism of 20 Mlb-ft . It uses the forceddilution P-DUC system , and is designed to process 3,750 t / h of tailings . In this case , due to increased capacity and the requirement to have complete redundancy of the P-DUCs ( operating and standby ), the P-DUCs were required to be designed to pump more than double the previous dilution flowrates .”
Ongoing advancements
The relatively new development of high-density and paste thickeners , combined with the need to process ever-increasing tonnages on projects , has led FLSmidth to improve its thickening technology using a variety of considerations . An extremely important factor in its technology is the torque capacity of the drives , especially with
P2 International Mining SUPPLEMENT | JULY 2021