August 11, 2021

Steel Hub PhD applies his mathematical knowledge to solve real-world problems

Raju Chowdhury joined the Steel Research Hub as a PhD candidate enrolled at the University of Newcastle under the Sustainable Steel Manufacturing research program. Prior to joining the research program, he completed his undergraduate and postgraduate studies in mathematics in his home country Bangladesh. In his research, Raju utilises his mathematical knowledge to solve a challenging industrial problem that the industry partner BlueScope Steel was experiencing with their Basic Oxygen Steelmaking (BOS) furnace.

In steelmaking, wearing of the inner refractory lining of Basic Oxygen Steelmaking (BOS) furnace is a known concern that occurs due to a combination of chemical, mechanical and thermal attacks in the harsh high temperature operating environment. Replacing refractory lining is a major capital-intensive issue and it is important to deploy some smart strategies to minimize wearing and prolong the useful life of the furnace. Increasing the lifetime of the refractories will lead to a decrease in the cost per tonne of steel and thereby will improve the economic sustainability of the steelmaking process in Australia. BlueScope Steel considered using retained slag splashing to form a protective layer on the furnace wall. The splashing would be achieved by blowing a nitrogen gas jet into the system between the regular batch steelmaking operations. The gas jet-slag interactions can generate numerous slag droplets which then deposit on the refractory wall and solidify, forming a protective coating. It was however felt necessary to simulate this complex process before carrying out any actual plant trials.

The research team at the University of Newcastle developed a comprehensive Computational Fluid Dynamics (CFD) model to predict the fluid flow behaviour during slag splashing in a full-scale BOS furnace. Based on the first principles of physics, the model solves the mass, momentum, and energy balance of the system and predicts the gas jet profile, associated pressure and temperature distributions, and slag coating formation behaviour on the furnace wall. The model helps to identify the possible wear-prone zones within the furnace. The simulation outcomes can be utilised to determine the operating conditions required to ensure an optimal level of protective coating.

To mimic the slag droplet impingement and subsequent coating formation process on the furnace wall, the research team also conducted controlled laboratory-based experiments to investigate solidification behaviour of a single molten droplet on a solid surface. The process is very fast and occurs almost instantaneously. Raju utilised high-speed imaging to visualise this process to get a deeper understanding of the underlying physics. He quantified the coated area and associated solidification time and correlated these two parameters with physical properties and impinging velocity of droplets. His study demonstrated that a combination of droplet physical properties and impact velocity critically governs the coated area and solidification time.

Overall, the outcomes of this research project significantly contributed to the fundamental understanding of the retained slag splashing process. During this project, BlueScope Steel has successfully conducted plant trials and outcomes have been satisfactory.

Being a part of the Steel Research Hub, Raju greatly benefited from this developing industry-academia collaboration. He had the opportunity to work on a very relevant problem in the steel industry and interact with the industry partner and multidisciplinary team members to understand different aspects of the research problem. Raju learnt how to apply his mathematical knowledge to solve real-world problems and grew as an independent researcher. He thoroughly enjoyed his research throughout the project and gained invaluable knowledge and skills that will assist him to progress further in his research career.