Ultra-Dense Thickeners from McLanahan

High-Rate and High-Density Thickeners
McLanahan’s High-Rate and High-Density Thickeners are simple in design and operation, but offer a multitude of benefits for producers. Although both sized based on hindered settling velocity, High-Rate Thickeners feature lower side walls and lower sludge densities, while High-Density Thickeners have higher side walls and denser underflows.

Because this water is available adjacent to the plant site, pump horsepower is substantially reduced and the elimination of settling ponds means resources are not covered up.

Thickeners are typically found in the following applications:

• Plant effluent treatment
• Solids concentration
• Counter current wash (CCW) or decantation (CCD) operations

Thickeners use a minimal amount of polymers/chemicals in order to help agglomerate very fine particles into larger particles that will settle much faster. Solids settle on bottom of the Thickener while clean water rises to the top. Rotating rake arms collect settled sludge and move it toward the center discharge cone. Solids are typically pumped out at 35-45 percent solids.

Deep Cone Thickeners:
McLanahan’s Deep Cone Thickeners process plant waste streams at higher rates of flow, in smaller areas than traditional High-Rate Thickeners by capitalizing on the principles of free settling velocity and compression thickening.

Tanks on these Thickeners are typically taller to provide a free settling zone. They also have a deep compression zone with long mud residence times, allowing sludge to compact under its own weight. Further significant sludge compaction can be accomplished by the use of a rotating picket mechanism that plows out channels in the compressed mud, creating passageways for trapped water to escape the bed. This results in thickened material forming a high-density sludge or paste.

Transportation of the sludge or paste from the underflow depends on its rheological properties. Centrifugal pumps may be employed at sludge yield stresses of up to 200 pascals, whereas higher yield slurries require a positive displacement pump for transport. Deep Cone Thickeners are free-standing, raised units that are available as either welded single piece tanks up to 12’ (3.66 m) in diameter or as field welded or bolted tanks up to 40’ (12.19 m) in diameter. They are characteristically tall with height to diameter rations ranging from 1:1 to 2:1.

These Deep Cone Thickeners offer producers underflow densities that are often not achievable with standard high-rate thickeners. Benefits of this performance include:

• Maximum water recoveries from a gravity settling device
• Production of an underflow that may be suitable for surface deposition
• Higher wash efficiencies for CCW and CCD circuits
• Reduction of evaporation losses
• Smaller settling ponds
• Reduced sizes and increased efficiencies of downstream dewatering equipment

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