Paste thickening
The sedimentation process is used to achieve the maximum underflow density possible for a given unsheared yield stress. High yield stress material exceeding 200 Pa is produced, limited only by the rheology of the thickened bed and associated transport issues. While sedimentation is a proven industry practice due to low capital cost, the value of experienced process equipment specialists becomes more apparent as the boundaries of operation are pushed.
Applications
The Metso Paste Thickener is best suited to applications requiring a high degree of dewatering, such as:
- Minerals tailings applications
- Mine backfill
- Pre-leach and CCD circuits
Metso Paste Thickening Technology is designed to suit each project, because we understand that the drivers for each project will differ e.g.:
- Environmental
- Water recovery
- Regulatory requirements
- Tailings management
- Available land space, or other
Maximized Underflow Density
Using our process knowledge and tools all Metso Paste Thickeners are designed to limit the build-up of rotating masses within the networked bed and reduce bogging or incidences of imbalanced rake loads in high yield stress solids beds. You will be able to maintain consistent solids inventory inside the thickener for a maximum continuous underflow density.
Metso has a long history of development of Paste Thickeners. Our successful experiences with large scale paste thickening has developed a thorough understanding of the key aspects of high density thickeners;
- Effective flocculation
- Dewatering
- Raking
- Prevention of rotating mud beds
- Discharge of thickened solids
Vertical Load Monitoring
A key feature of the Metso 2nd Generation Paste Thickener is Vertical Load Monitoring via Smart Rake Lift – one of the only systems in the world able to detect early formation of rotating beds. Tank mounted bed mass sensors can’t detect these loads.
By incorporating Vertical Load sensing with plant process data into the Thickener Optimizer Control system the solids inventory within the tank can be maintained at a consistent loading. The Operator now has another view of what’s happening inside the tank. This leads to more consistent underflow density and reduced downtime.
Smart Rake Lift
With the Smart Rake Lift system, individual hydraulic cylinders are monitored and actively adjusted to maintain alignment of the rake mechanism.
Design tools
Our application specific design of the thickener begins with the use of design methods such as Discrete Element Modelling (DEM) to examine solid particle movement within the thickener, and Finite Element Analysis (FEA) for structural steel design. Design for serviceability is a feature of our Paste Thickeners, with our skid mounted hydraulic power unit (HPU) for centralized connections of hydraulic hosing from the rakelift cylinders and drive unit.
Unique Design Features
Unique design features including smart rake system, low profile rakes with tie-cable load sharing, rake blades supported by thixoposts, steep tank floor slope and high sidewall, high installed drive torque, and feed systems with break tanks when required.
Our current development of rake drive units is up to 14.5MNm. Bearing life is >100,000 hours based on 99% at normal operating torque and 1% at maximum operating torque. Tank structures can be supplied as bolted or welded to suit project requirements.
