By Kathie McGregor

Overcome risks of high levels of minor elements in smelting feedstocks

Do you need to optimise your purchasing, planning and processes for changes in orebodies?

The rising complexity of feedstock materials continues to be a challenge for base smelting operations.

Our industry is depleting its supply of primary coarsely-ground ore. This has made the transition towards the use of secondary feedstocks, such as e-waste, necessary.

Thanks to this increasing complexity, feedstocks now more commonly contain a high level of minor elements. If not dealt with correctly, these can have economic, health, and environmental impacts on smelters.

The increased presence of minor elements in ore bodies can create costly challenges or new opportunities, depending on your approach to the process.

The risks of overlooking minor element deportment

Complex ore bodies with high levels of minor elements pose risks across all stages of the flow sheet, which you expose yourself to if you don’t adapt your processes. These include:

• Disrupted business — unplanned stoppages or delays may be experienced and, in severe cases, this may even lead to short-term shutdowns. These blockages and unplanned reactions could also damage and corrode machinery.
• Loss of product quality — when the minor elements are overlooked, impurities prevent ore from reaching the grade required to generate a higher price. For example, bismuth in the lead smelting process affects the quality of lead outputs. But if controlled early on in the process, bismuth and other minor elements can actually enhance output quality rather than reduce it.
• Health risks — hazardous impurities, such as arsenic or lead, present in ore bodies can be released during the smelting process. These can cause long-term health problems for employees, and future liabilities for companies.
• Pollution — contaminant-laden air emissions and process wastes, such as wastewater and slag, are monitored by licenses from the EPA. Licences dictate how much material you can release into the environment, and exceeding this can lead to significant fines.
• Missed opportunities to add value — if ore contains valuable minor elements (such as gold), and smelter operators are unaware of their presence or extraction process, then opportunities to recover additional value across flow sheets can be missed.
• Prosecution or smelter closure — smelters need to meet strict guidelines and controls, especially in relation to the disposal of minor elements. When emissions and waste legislation requirements are breached, companies risk large fines, prosecution and, in some instances, even closure.

Ultimately, it’s vital to reduce the risks and seize the opportunities created by the rise in ore complexity.

How can you manage minor element deportment across your organisation?

In order to optimise the smelting process to refine complex ore and prevent any potential hazards or risks, there are steps to take across 3 key stages of the smelting process.

1. Strategic planning

Planning is perhaps the best way to get ahead of this issue of rising complexity.

To prevent a drop in productivity and quality, you need to create processes that are optimised to handle the behaviour of minor elements. It’s also essential to consider the overall adjustments required for flow sheets to process complex feedstocks.

With an understanding of expected hazardous outputs, the planning phase can also incorporate safeguards against potential environmental and health concerns — such as implementing waste disposal strategies and employee safety measures.

2. Purchasing

When examining raw materials, companies need a comprehensive understanding of the ore characteristics and tools to recognise the minor element concentrates that may be present. With this information, concentrates that have unwanted impurities can be avoided, and the ore’s behaviour within a plant’s processing framework can be understood.

3. Processing

Having constant awareness of how different minor elements will behave across your flow sheet is essential to the processing phase.

This ensures that process cycles can be tweaked accordingly.  As a result, quality is not compromised, plant productivity remains as planned, and equipment is maintained to the required standard.

Multi-Phase Equilibrium — tools to help you optimise your flowsheet

Smelting operations can get a clear picture of minor element behaviour and deportment with thermodynamic modelling, combined with experimental validation of the models.

We have developed Multi-Phase Equilibrium (MPE™) software, using the CALPHAD method for the calculation of multiphase equilibrium in high temperature base metal production systems. It can be used for modelling ferrous and nonferrous smelting processes to improve understanding, diagnose problems and optimization.

MPE™ is a powerful and easy-to use analytical tool that can model how minor elements will deport in your process, and can be used to:

1. Model the heat and mass balance of base metal smelting.
2. Calculating liquidus temperatures and designing fluxing strategies for specific feedstocks.
3. Model the minor elements deportment among phases across the whole smelting flowsheet.
4. Recommend optimum process conditions — enabling management of high levels of toxic elements (such as arsenic) without environmental risk.
5. Compare of scenarios with environmental level requirements.
6. Determine significant trends through flow sheet modelling and statistical analysis of plant data.

The problems that arise from increasingly complex feedstocks can affect base metal smelters across the entire refinement process.  Processes and tools such as Multi-Phase Equilibrium technology create a seamless approach for understanding and optimizing minor element deportment in smelting operations, minimize risk and take advantage of opportunities to recover valuable impurities.

Are you interested in understanding how you can implement CSIRO’s technologies in your smelter operation?

Contact the Minerals Process Optimisation team on +61 3 9545 8912 or email me at Kathie.Mcgregor@csiro.au to talk about how you can minimise the risks associated with minor element deportment.