Whilst resources such as copper, lithium and iron ore, are making solid steps toward recovery the Australian economy is focusing on commodities to assist in the building of infrastructure- news that is welcomed by the aggregates community.
The major challenge suppliers will now face is how to plan for sustainability over the next 10 years. Securing new sources of material supply close to the market will be high on the agenda, with quarry and plant operators likely to plan expansions, acquisitions and growth strategies.
However, approvals and permits are not issued without significant environmental and operational provisos, i.e. water usage, effluent management, water run-off management and catchment protection all require significant investment of time and money.
This investment will have a direct bearing on the viability of upgrade and expansion plans for any extractive resources. Regulatory requirements are increasingly restrictive on the amount of new water that may be added to a process circuit, and environmental guidelines and consideration also restrict the storage of tailings in open pits or ponds.
A number of McLanahan customers are currently assessing how “filtered tailings” could fit into their resource expansion projects or upgrade projects. When we configure a filtered tailings solution we typically aim for a closed loop or zero pond tailings management strategy.
For a closed loop tailings system, quarry operators are encouraged to consider an ultra-fines recovery system, where potentially usable ultra-fine product can be reused as a blend medium or for other products, rather than sending it straight to waste.
Quite simply, product fines that would go to a pond can now be redirected to a thickener, where they are densified and process water is captured for plant reuse. The thickener underflow is pumped to a mixing tank and run through a filter press, where the solids are further dewatered and a dry cake is produced. The filtrate (water) is also captured from this process for reuse or disposal to alternative markets.
Recessed plate filter presses are commonly used in these applications because of their ability to deliver drier cake and higher water recovery and being relatively simple to operate.
A typical McLanahan filtered tailings system is designed to add modules as required. These modules may include an ultra-fines recovery system, thickener and McLanahan filter press system.
The filter press circuit may also incorporate an optional dosing system should the material require additional flocculation or other treatment. Similarly, the filtered water can be treated in real time before returning to the processing system or disposal. To ensure the system is designed correctly, material samples are tested at the McLanahan lab in Newcastle NSW.
Many of Australia’s top aggregate producers are at the forefront of process design and already include closed loop tailings system in their process design and plan or permit applications. By continuing to develop processing options a modular design can often be achieved which combines the benefits of lower cost but customised solutions to meet individual site plans.