A Peruvian mining company reuses process water as part of its iron ore processing. Until November 2019, however, this was made difficult by the fact that the medium, which is collected in a tank on site, has a very high solids content of 60–70%. After an attempt to drain the water and remove the sediment in the tank with shovels had failed after four days, the owner decided to purchase a submersible pump with an agitator. Netzsch Pumpen und Systeme GmbH recommended a Netzsch Tornado T1 rotary lobe pump for pumping the slurry from the tank. The strong suction capability allows the pump to work with a high flow rate and handle a high solids content, while a geared motor with low speed reduces the level of wear. A double mechanical seal and a rotary lobe made of nitrile rubber minimize the risk of abrasion damage.

Tornado T1 pump

After a detailed analysis of the problem and the liquid to be pumped, Netzsch suggested using a Tornado T1 pump of size XLB-3/2, which offers a number of advantages over the originally selected submersible pump. The key benefit is that this model is a self-priming displacement pump that can ensure continuous pumping due to its design: two synchronised rotors inside the pump intermesh, generating negative pressure at the intake side that continuously pulls the medium towards the rotary lobes, which then transport it to the delivery side. This powerful negative suction allows the Tornado T1 to pump almost any type of medium. This applies to both low viscosity and high viscosity substances as well as to thixotropic or dilatant substances, lubricating, non-lubricating, shear-sensitive or abrasive media.

“It is therefore ideal for the process water at the mine in Peru,” explains Monica Mitterstein, Global Manager Mining & Explosives at Netzsch.

The material and design of the T1 are always adapted to the special requirements of the designated medium. For viscous and abrasive materials and those containing solids, Netzsch offers different rotary lobes with suitable geometries in each case. Materials adapted to the medium additionally increase the durability of the rotary lobes as well as their service life.

Tri-lobe helical rotors made of nitrile are used for the application in Peru to minimize the risk of abrasion damage. In addition, double cartridge mechanical seals are installed which are not sensitive to the solids in the medium. The gear motor of the pump works at a lower speed, which also causes less wear. Overall, this significantly lowers the maintenance costs for the pump.

Pumping out slurry

To make handling easier, the rotary lobe pump was installed on a mobile trolley and equipped with flexible hoses. This makes it easier to extract the slurry from the tank through the ten ventilation openings at the top of the tank as well as through the corners. With the new hose and the improved handling of the smaller lance, it was possible to remove the required minimum volume of solids. “The hose can be moved through the tank easily extracting the solids. The Tornado XLB-3/2 continuously provides the required flow rate without pressure loss,” says Mitterstein.

After these measures, the process water from the tank still has the required quality to be used in the ore processing without any issues.