High-Density Thickeners

High-Density Thickeners can be considered an intermediate case between High-Rate Thickeners and Paste Thickeners. They are commonly characterised by:

  • Having a higher sidewall tank (to provide enhanced compression effects)
  • A steeper floor slope to assist in moving solids to the discharge area
  • A low profile rake structure combined with pickets to enhance the bed dewatering
  • A rake drive suitable for underflow mud with a yield stress of 50-150 Pa
  • Producing underflow mud capable of being pumped with the McLanahan M3H centrifugal Slurry Pump

Similar to both the High-Rate and Paste Thickeners, the High-Density Thickener depends on the feedwell to create the optimal free settling characteristics.

High-Density Thickeners can come as either elevated or on-ground tanks according to industry preference. Likewise, the tank structure is available in a number of material choices, such as steel, concrete or FRP. 

High Density 1
High Density 2
High Density 3

Why McLanahan High-Density Thickeners

McLanahan can provide a range of configurations and style to meet your requirements. Our process engineering team will conduct test work to determine the optimal size High-Density Thickener for your application. Our design tools will provide customers with an indication of the water recovery balanced against capital costs. Integrating McLanahan High-Density Thickeners into a plant is simple. Control systems take care of most of the operation; however, McLanahan can train operators in the preparation and use of flocculants, as well as general Thickener operation. 

How High-Density Thickeners Work

High-Density Thickeners separate liquids from solids using gravity settling. A key requirement is to contact the solids with added chemicals under the right shear conditions for building large floccules. The efficiency of flocculation contributes to an enhanced settling rate. Once settled in the bottom of the tank, the deep mud bed is further dewatered by the use of pickets attached to the rake arms. Thickeners are operated and controlled by a touchscreen programmable logic controller system. Operating logic allows for the customisation of the unit for plant needs, including the ability for the Thickener to shut down without an operator being present during extended hours of operation. The hydraulic drive gives an accurate sense of torque on the rakes. At high-torque conditions, a rake lift will activate to draw the rakes up from the mud. The system then steps the rake down, monitoring torque on the way.

Popular Applications for High-Density Thickeners

High-Density Thickeners are found in many applications such as:

  • in the feed preparation to a subsequent filtration stage. Filters are most efficiently sized with a higher solids concentration but not too high such that the flow properties into the filter are inhibited. This enables the designer to take advantage of the lower operating costs of gravity separation provided by thickener before requiring the higher driven force (and higher cost) of a vacuum or pressure filter.
  • Where there is value in improving water recovery in a tailings application but insufficient justification for a full paste system
  • In a counter-current wash system where the higher underflow densities may reduce the number of stages required or reduce the volume of wash water required. 

Benefits of McLanahan High-Density Thickeners

  • Recovers immediately reusable process water
  • Reduces demand on make-up water and helps keep water consumption at sustainable levels
  • Drastic reduction in slurry volume reporting to waste ponds
  • Reduces horsepower required to pump fresh water
  • Tanks can be supplied as welded-together or bolt-together and with either concrete or steel bottoms
  • Minimum drag rake arm design reduces the amount of torque required to move the rakes through the settled solids and minimises the disturbance of the already settled solids
  • Hydraulic drive to power rakes and operate the rake lift
  • Accurate rake torque monitoring
  • Rakes can operate in forward or reverse