Coal Preparation » Dewatering
Tailings management is critical to the efficient operation of a modern mine and mineral processing plant. Due to intense scrutiny of the overall environmental impact and water usage of CPPs, obtaining approval for tailings dams has become increasingly difficult, leading to an increase in the use of tailings dewatering technologies and co-disposal systems. Belt press filters (BPF) are the most widely used method in the Australian coal industry to dewater tailings thickener underflow. The BPF cake is typically disposed of with the coarse reject. Although known by many names including belt filterpress, multi-roll filter and twin wire press, only BPF will be used within this text. While BPFs have been found to be the most economical tailings dewatering technology to produce a reasonably dry cake (Murphy, 2012), there is considerable room for improvement in their operation and maintenance. Improvements to the efficiency of existing BPF installations will also have significant economic benefits for their operations.
The objective of this project was to provide the Australian coal industry with a useful, supplier-independent handbook describing the performance of the available BPFs under a range of operating conditions and providing practical techniques to optimise the design, operation and maintenance of BPF installations. This handbook sets out the principles that contribute to good practice for process design, operations and maintenance. This handbook is not intended to replace the relevant manufacturer operation and maintenance manual, but to compliment it. If the guidelines for best practice design are followed, efficient dewatering performance high equipment availability and minimal operational and maintenance costs will follow.
The major motivation for introduction of BPFs to the coal industry is:
· To recover water for re-use in the plant;
· To improve the handleability of rejects;
· To reduce handling costs;
· To restrict filtrate discharge from the plant and from reject disposal sites;
· To satisfy increasing environmental regulations of existing sites;
· Increasing difficulty in gaining approval for tailings dams; and
· Ensuring existing impoundments do not exceed volume capacity.
The combination of an effective closed water circuit and dry disposal of fine rejects makes BPFs an attractive option for operations looking to reduce their environmental impact.
The project outcomes include:
· A detailed review of existing, operational BPF installations;
· Creation of a database of information for the reference of plant designers and operators;
· Identification of 'industry standard' best practices; and
· Identification of areas for further improvement.
Application of this handbook should provide a number of benefits which include:
· Improved BPF throughput and availability leading to reduced unit operating and maintenance costs and maximisation of plant feedrate;
· Minimised consumption of human resources, consumables, power, water and rejects voidage;
· Reduced BPF filtrate solids concentration leading to improved unit capacity;
· Reduced flocculant consumption leading to operating and maintenance cost reduction;
· Improved design of BPF installations, and the optimization of BPF operation and maintenance;
· Increased belt life and reduction in catastrophic belt failures leading to operating and maintenance cost reduction;
· Filtercake moisture reduction leading to reduced raw water and stage area requirements, decreased downtime due to less chute and bin blockages and increasing revenue for plants that send their BPF cake to thermal product (due to an increase in BPF cake Calorific Value (CV)); and
· Maximised mine life by ensuring that the required volumes and characteristics of process water are produced and the tailings slurries generated are not excessive or contrary to environmental approvals.