Pigment and Filler Production

Larox LPP in Thickener Underflow Duties

Thickener underflow pump duties are often handled by high flow rate centrifugal pumps

These pumps are operated intermittently due to the fact that the volumetric flow-rate of the pump is higher than the constant output flow of the thickener. In addition to this, centrifugal pumps pose control problems at low flow-rates

Intermittent operation of the centrifugal pump causes fluctuations in slurry density and may withdraw all solids if run unchecked. Inconsistent operation of a centrifugal underflow pump, pose a threat of choking the underflow lines which may then allow the pump to run dry, consequently causing induced frictional damage to the seals and impeller

The most common problems associated with thickener underflow pumps are:

• Intermittent flow disturbs the operation of the thickener (variation of underflow SG),
• Gravity flow through the pump (uncontrollability of the flow),
• Requirements for higher viscosity and density
• Choked thickener outlet lines

By using LPP pumps in thickener underflow duties these problems can be avoided.

The LPP pump is capable of being accurately controlled between it’s minimum (close to zero flow) and maximum flow-rates

As a result, the Larox peristaltic pumps can be operated on a continuous basis with suitable flow, eliminating problems normally associated with intermittent thickener discharge

Accurate flow control is achieved with the LPP as no material can flow by means of gravity due to the utilisation of the innovative rolling compression element. Unlike conventional pumps the LPP with its rolling compression element, requires minimum torque at low rpms

In the case of a thickener underflow blockage, two distinct advantages are apparent when using the LPP. Either the blockage is automatically removed through the high suction vacuum of the pump, or the pump can be reversed to clear the blockage. Both of the above would normally require either require physical dismantling of the lines or applying flushing water

Constant slurry thickness secures the maximum output and stability of the whole process downstream of the thickener. It is effortless to achieve and maintain higher underflow densities with an LPP as it can cope with a solid content up to 80% pumping the material to the next process stage with ease.