Look behind the scenes
Lithium slurry is one of the most demanding media to be conveyed in the chemical sector: Lithium does not occur freely in nature due to its high reactivity. It is only stable in a complete dry environment but slowly reacts to lithium nitride. A matt gray lithium hydroxide layer quickly forms on the surface in moist air. Elemental lithium already reacts in contact with the skin's moisture and thus leads to heavy burns.
A battery manufacturer in China therefore decided to choose the NEMO® progressing cavity pump in stainless steel with flexible rod from NETZSCH. The main characteristic of this pump type is the eccentric screw principle in which a spiral rotor rotates oscillating in a geometrically matched stator. This results in uniform delivery chambers in which the medium is moved continuously from the suction to the pressure side free of pressure fluctuations, pulsation or shear forces.
In order to meet the high requirements of the reaction sensitive light metal a flexible rod connects the drive with the shaft instead of open or oil filled joints. The shaft has a shrink with the rotor and the connection to the drive shaft, so that both interfaces are hermetically sealed. Since no components rub against each other at the connections, the flexible rod hardly wears out and requires neither sealing nor lubrication. The maintenance-free flexible rod causes hardly any maintenance costs. For this reason a PTFE sleeve seal without oil is also used as the mechanical seal. Stainless steel and a NEMOLAST® stator were used as materials for the battery manufacturer's application.
The polished stainless steel surfaces ensure that the medium cannot adhere. This reduces contamination to a minimum and makes the pump easy to clean, which is an important requirement in a chemical process. To take account of the highly explosive mixture of the medium, the pumps are driven by an electric motor. The battery manufacturer is highly satisfied with the pump solution from NETZSCH and has therefore ordered 200 pumps for this application.