Optimising slurry transport

By Dr Mark Cooksey

Process improvements to increase capacity and maintain reliability

Slurry transport is a complex process involving multiple phenomena, with optimisation requiring deep understanding and clever solutions.

Today, in the effort to increase throughput and reduce water consumption in processing circuits, and to reduce the volume of tailings, many mineral processing operations are increasingly pumping thickened materials.

However, a number of operational challenges — amplified by the increasing variability of ore — can arise from this approach.

It is by proactively understanding and addressing these risks that you can optimise your processes for more effective slurry transport, resulting in reduced energy consumption and increased productivity.

The effect of inaction on processing operations

If you are not proactive, you become susceptible to the inefficiencies and risks of transporting high concentration slurries, including:

• Excessive energy use due to increased friction losses within pipes — higher concentration slurries require increased energy input to maintain throughput, increasing energy costs.
• Bogging, blockages and unplanned stoppages and maintenance — pumping thickened materials greatly increases risk of pipe blockages, requiring system shutdown and maintenance. These unplanned stoppages lead to a loss of production, impacting revenue.

Increasing water dilution to mitigate these issues is not uncommon as a ‘quick fix’ solution. This can allow you to operate with less risk of blockage and lower energy. However, employing this solution is generally not a sustainable option, and can lead to further operational issues, including:

• excessive water use and cost
• exceeding regulatory water use limits
• inability to reduce water use in line with community expectations
• adverse impacts on downstream processes
• reduced production and revenue due to dilution of the valuable product

Identifying slurry characteristics: The first step towards optimising processes

Only by understanding the characteristics of your slurry, and the design and operating constraints under which you operate, are you able to overcome these risks.

Slurries have complex properties, so you need to fully understand the rheology of your materials and the flow regimes of your pipes. Understanding the unique characteristics of your operation —primarily, yield stress and flow (i.e. laminar or turbulent) — will help you determine the best options for process optimisation.

How identifying process limitations helped Minara Resources achieve improved slurry transportation

This approach was recently used by Minara Resources, who were able to rectify a system overload caused by increasing ore throughput.

After an initial attempt to rectify the situation through parallel operation of both duty and stand-by pumps, operations became constrained by total power draw. The self-administered solution – increased dilution to reduce slurry viscosity – was unacceptable due to adverse impacts on metal recovery and reagent use in the downstream process.

Through collaboration with CSIRO, Minara was able to define their specific slurry parameters and requirements and apply CSIRO-developed Drag Reduction Technology to:

• reduce pump discharge pressure by 20% without increasing slurry dilution
• reduce peak power draw so that it no longer became a constraint – and eliminated the need for a potential upgrade
• reduce water use in one of its paste thickener systems by 75%, from ~20m³/hr to ~5m³/hr, while maintaining the same production flow (~500m³/hr).

Partner with CSIRO to achieve optimised slurry transport

The CSIRO Minerals Processing Optimisation Team offers the science-led expertise, facilities and technology to assess and optimise slurry transport in your operation, with a focus on increasing productivity and improving social and environmental outcomes.

We provide:

• expertise in the physical handling and processing of particle suspensions in mineral processing and tailings treatment
• lab- and pilot-scale facilities
• measurement, simulation and modelling of multiphase flows and solid-liquid separation processes through advanced rheological understanding and physical experiments
• world-leading technologies such as our Drag Reduction Technology, which uses a pipeline insert that provides a lubricating layer on the pipe wall to allow higher solids concentration to be pumped through. Drag Reduction Technology has demonstrated up to 75% reduction in power required to pump slurries.

Our innovative services and technologies have proven benefits for processing operations, including:

• reduced water consumption
• reduced energy consumption
• improved pump reliability.

Improving pipeline capacity and slurry velocity leads to improved slurry management and improved operational efficiency through increased productivity. This in turn offers the financial benefit of a stronger bottom line, demonstrating how analysing and optimising your slurry transport doesn’t just stand to benefit your daily slurry processes, but your operation as a whole.

Start with the experts at CSIRO

If you’re facing slurry transport challenges, a good place to start is to speak with the Mineral Processing Operations Team at CSIRO.

Contact the team on +61 3 9545 8865 or email me, Mark.Cooksey@csiro.au to take the next steps in analysing your fluids-based processes to determine areas for optimisation.

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