Green ironmaking of Australian ores in a fluidised bed reactor using hydrogen as a reducing gas

Project lead

Dr Nawshad Haque, Nawshad.Haque@csiro.au

Lead researchers

Dr Nawshad Haque

Sameer Usmani (PhD Student)

John Pye (ANU)

Alireza Rahbari (ANU)

Geoff Brooks (Swinburne University)

Challenge

Global carbon emissions have surged to alarming levels, demanding urgent attention to counter the escalating global temperature. Short-term mitigation strategies involve enhancing energy efficiency, but profound decarbonisation necessitates pivotal measures to rejuvenate technologies with lower emissions. The industrial sector, accounting for 24% of global carbon emissions, has emerged as a critical focal point. In 2022, the steelmaking industry alone contributed 2.6 Gt of CO2 emissions, constituting 27% of the industrial sector and 7% of the total global carbon emissions, according to the International Energy Agency (IEA). Despite this, mitigation efforts have predominantly concentrated on the electricity sector.

Recent research proposes hydrogen as a pivotal element in reducing emissions in iron and steel manufacturing. The strategic utilisation of hydrogen in the ironmaking process plays a vital role in curbing carbon emissions. With hydrogen’s physicochemical advantages, such as its efficacy as a superior reducing agent in iron ore reduction compared to carbon monoxide, recent studies by Bonalde et al. and Hammam et al. support this assertion. These studies indicate that hydrogen serves as a faster and more efficient reducing agent due to its nucleation-driven reduction mechanism, contrasting with carbon monoxide, where reduction is controlled by gas diffusion. Furthermore, hydrogen-based iron ore reduction generates water as a by-product, aligning with initiatives for zero carbon emissions.

While research indicates the feasibility of using hydrogen to directly reduce iron ores, challenges such as sticking issues and low gas utilisation, stemming from diverse powder ores and complex kinetic mechanisms, necessitate a deeper understanding of the reaction mechanisms.

This comprehension is crucial for addressing challenges during scale-up and advancing this technology to commercial viability.

What we are doing

A multi-step kinetic reduction model was developed on Aspen Plus using a Gibbs reactor. The model was validated with the Baur-Glaessner diagram. The model will be further extended to build a kinetic model of the fluidised bed reactor based on experimental analysis to be performed. The experiments will provide the kinetic data, rate limiting steps and other crucial parameters which will define the kinetic modelling specific for Australian iron ores. The model will be further studied to scale up to an industrial level and conduct the techno-economics of the process considering the green energy and hydrogen supply.

This research work will answer the concerns about the ability of low-grade Australian ores to be used in cost-effective hydrogen ironmaking processes. This project will build an understanding of the end-to-end techno-economics of hydrogen direct reduced ironmaking in the Australian context, with an emphasis on understanding the impacts of Australian ore grades on the overall process design.

Outcomes to date

The thermodynamic model was developed, and its results provide an insight into the conversion process. It was observed that the conversion of hematite to magnetite occurs at a lower temperature range of 400°C to 600°C. In comparison, the magnetite to wustite conversion occurs at a higher temperature range of 600°C to 900°C. The thermodynamics report that the higher the temperature, the higher the reduction rate, and the lower the hydrogen requirement.

However, the literature reports that the reduction kinetics is more influenced by physical parameters (ore size, porosity), leading to different rate limiting steps and reaction model. The thermodynamic modelling provides an overview of the operating temperature of different phase reactions, which will be beneficial to investigate a defined temperature range for different phase changes.

The higher temperature leads to lower hydrogen requirements. However, the questions about the effect of other influencing parameters (such as diffusion, nucleation, and particle size) are still important to understand the kinetics. The kinetic modelling using a fluidised bed reactor will be able to answer these questions, which will be developed in future as part of this research work.

Project finish date

June 2024