by Kathie McGregor

A three-scale investigation for pyrometallurgical process development

If high-temperature smelting is a core aspect of your operations, there’s room to develop a new approach to pyrometallurgical process development as feedstocks get more complex or you have growing supplies of intermediate materials.

I previously outlined the details and risks of rising feedstock complexity in last month’s blog. Essentially, the issue is that current deposits are being depleted and metal producers are having to deal with increasing impurities and lower-grade feedstock. They’re also looking at having to carry out value recovery from stockpiled wastage products.

For example, some new copper deposits have a high silicon dioxide/iron ratio which makes conventional fluxing with silicon or iron oxide inefficient.

So current processes — including pyrometallurgical processes —may not be suitable for future feed scenarios. They can’t achieve the higher recovery of valuable components from deposits or waste material that’s needed to remain a profitable producer.

Ultimately, metal producers want to know whether or not they can process particular materials, and how it’s going to affect their business.

Why aren’t metal producers springing into action?

Despite the ceaseless pressure on metal producers to investigate the best processes, there is a perception that developing and testing a new high-temperature smelting is excessively difficult and expensive.

It’s believed that getting the expertise needed means gathering specialists yourself, and that undertaking the testing means having to use several facilities.

Other reasons producers are hesitant to investigate include:

• the technical difficulty of conducting high-temperature investigations
• the requirement of new equilibrium or thermodynamic data
• the need for multi-scale experimentation to allay technical risks.

At CSIRO, we’re diminishing the belief that process development is too difficult. Not only is our framework cost effective, but all our expertise is in the one place, as well as our state-of-the-art testing facilities.

And it’s vital to understand that new pyrometallurgical processes can be developed, so you can remain a step ahead and make strategic decisions early.

The multi-scale framework to validate the effects of change on your processes

We have the facilities and expertise to trial and develop high-temperature smelting and metal refining processes. Our methods allow you to gather data at a small scale and then build upon it to fully understand how new feedstocks will behave in your operations. Although the framework is designed to be consequential, it’s not a rigid structure and can be entered into at any stage:

1. Small scale fundamental and equilibrium investigations.

At this stage, we generate data for accurate modelling and make predictions about how different feedstocks will behave in high-temperature smelting operations. We then test those predictions in the larger scales.

This stage involves small scale investigations — where equilibrium and thermodynamic data (required for accurate model predictions) are generated.

2. Medium (kg scale) technical investigations.

This stage can confirm model prediction and predict minor element behaviour. This stage also determines general technical feasibility, and any key parameters or “show stoppers” — allowing you to remove any problems before major expenditure.

This stage involves:

• testing the technical feasibility of metallurgical processes, as a prelude to pilot scale operations
• simulating industrial Top Submerged Lance (TSL) type processes using kg scale apparatus
• the partition and deportment of minor elements, such as slag, copper/matte and fume streams
• mass balances.

3. Pilot scale investigations using a 250kg scale TSL reactor

This stage provides design data and high level technical confirmation, including specifications and element behaviour. It also allows you to establish process kinetics and conditions which demonstrate technical feasibility, and generate design information at a reasonably large scale.

In this stage, a range of processes can be simulated, such as:

• an integrated TSL type pilot plant (Sirosmelt) is used to confirm the feasibility of metallurgical processes
• a system for the continuous feeding of material
• a system for the collection and handling of fume material
• a process for the neutralisation of sulphurous gases, and the handling of molten materials — including sampling and tapping. If required, molten slag products can be granulated to form glassy granules.

This multi-scale model is adaptable to your particular concerns: the small scale is well-controlled, where each variable can be adjusted individually. The larger scales mean they are more industrially relevant, but with less direct control of variables.

This three-scale framework has been successfully used for:

• the separation of lead and copper during the processing of intermediate metallurgical residue
• the removal of impurity elements from copper concentrates during smelting
• the continuous converting of copper and nickel matte

It has also been successfully used in the recovery of zinc from lead blast furnace slag, as can be seen in the following case study.

Case study: Using high-temperature smelting to recover valuable components from slag

Many intermediate metallurgical materials contain valuable components such as silver, zinc, copper and lead and, normally, they are difficult to recover. These materials are frequently stockpiled, just waiting for a viable process to unlock their value. For example, zinc can be recovered through smelting where the zinc is fumed into the gas stream.

The Sirosmelt pilot plant, located at the CSIRO Melbourne/Clayton laboratories, has been used to demonstrate this process.

A proven framework for smelting process development

This three-scale framework reduces the technical risk of high-temperature process development, speeds up lead times, and avoids unnecessary expenditure. It achieves this by using the same underlying data, and has the ability to coordinate experiments and tests at one geographical facility.

At CSIRO, we have the facilities and expertise — at one location for the end to end process — and a proven high-temperature process development framework to assist companies with cost effective process development.

The other benefits of engaging CSIRO to help you with pyrometallurgical process development include:

• you gain access to sophisticated thermodynamic and process modelling, which can provide indicative directions and chemical equilibrium of a process under consideration. We also provide heat and mass balances, which are required for flowsheet techno-economic evaluation
• you experience a reduction of technical risk, thanks to multi-scale research and development — as opposed to going straight to a demonstration plant
• you gain the fundamental information required to tune and validate thermodynamic and flowsheet models correctly
• you experience a further reduction in technical risk of the new development as the scale of work increases from 5-10 g to 100-250 kg.

Interested in understanding how you can improve your high-temperature process development?

The CSIRO Pyrometallurgical team are world leaders in developing pyrometallurgical processes. Contact the Minerals Process Optimisation team on +61 3 9545 8912 or email me, Kathie.Mcgregor@csiro.au to talk about how you can be prepared for the changing complexity of feedstock.

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