Active Gap Control is an innovative solution to regulate material size, shape and quality.
We often think of plant feed as being homogeneous, uniform and well suited for steady state operation. The reality, however, is quite different.
The normal day-to-day operations of a mineral processing circuit find plant feed to be variable in size, shape and physical properties.
These variances are caused by numerous factors, including mining in different pit areas, operating at different depths, upstream crusher performance, circuit screen efficiency and even current weather conditions. Each variance can result in the crusher’s feed material changing substantially.
Crusher performance itself is also subject to change depending on liner condition and wear rates.
It is evident that crusher performance, specifically crusher throughput and crusher product size distribution (PSD), can change rapidly and true steady-state operation is seldom achieved for continuous periods.
What can be done?
To optimise crusher performance in real-time, traditionally highly subjective manual crusher setting changes are made based on limited data usually gleaned from a visual observation of the product on the belt or a rough evaluation of crusher power draw and hydraulic pressure. The outcome of this approach is mixed and provides no clear cut, quantifiable data to support any scientific decision-making process.
The crusher’s performance tends to be sub-optimal, and the throughput not homogenised.
To resolve the issue, Minprovise has a system that automatically analyses the crusher product belt and provides documentable numerical data reflecting crusher performance based on current feed ore characteristics, enabling a real-time adjustment to ensure optimal production.
The system requires no manual intervention and accommodates not only feed material property changes but also crusher liner wear profile variances.
Minprovise has assembled a Kawasaki ZI-2100 cone crusher at its Perth-based workshop and connected it to the Active Gap Control (AGC) system for prospective clients to view without having to go to site.
This system needs to react quickly to changes in the crusher circuit and prove its worth in terms of increased production quality and rate, which is exactly why the AGC system was developed.
In-house tests using the ZI-2100 cone crusher and the AGC system lived up to expectation and were able to modify crusher operating parameters in all cases, resulting in an optimal, steady-state operation.
What does the AGC system look like?
The system uses an advanced particle-size analysis camera to accurately assess crusher product size distribution and production rate on a continuous basis.
Changes to the crusher settings can then be made using this information. When coupled with a Kawasaki ZI Cone crusher, or any Hydro Cone style crusher on-site, these changes can be made on the fly, meaning no reduction in feed rate or stopping of the upstream circuit equipment is required in order to affect the required change in gap-setting.
The system ensures the optimal PSD is always achieved and overcomes circuit instability brought about by feed material property changes, feed material moisture content variances, crusher liner wear profile, upstream crusher performance variances, and upstream and closed-circuit downstream screen efficiency changes.
What does that mean for an operation?
Ensuring optimal crusher size distribution has multiple benefits to the overall operation. These may vary based on the exact operating conditions and circuit layout, but there’s a number of more general benefits.
Improved liner wear profile and achievable life
The AGC system ensures the crusher is operating within its ideal design gap setting, so crushing chamber wear profiles can be improved and problems associated with poor crusher wear profiles avoided.
Downstream efficiency improvements
Since the performance of downstream equipment is heavily dependent on receiving the ideal feed-size distribution from the upstream crusher, improvements can be made when screens and size classification equipment run within well controlled operating parameters.
Product quality and throughput increases
Given ‘design’ crusher gap settings are selected to maximise plant performance – eg generation of lump versus fines in iron ore, or liberation of high-value minerals – monitoring and ensuring operation at the ideal crusher setting means the overall product quality is likely to increase.
Additionally, since the AGC circuit design limits recirculating loads by operating at the optimal crusher settings, material is crushed to the right size the first time, preventing multiple passes through the circuit.
This increases achievable plant capacity while reducing circuit operating costs due to recirculation inefficiencies.
This feature appeared in the October issue of Australian Mining.