Continuous Measurement of Liquid Steel Temperature and Chemistry

Liquid steel processing occurs in batch sizes of hundreds of tonnes at temperatures in excess of 1500oC, but the target composition and temperature specifications have ppm and single digit degree windows respectively. This is an exciting and challenging area to work in. Previous research at Swansea University characterised the efficacy of gas stirring systems in the basic oxygen furnace (BOF). Gas stirring homogenises the material in the furnace which enhances the efficiency of purification of the metal. Post mortem analysis of the ports that delivered the gas (called Tuyeres) revealed the presences of metallic accretions on their surface which have a negative effect on stirring and hence process efficiency [1]. Laboratory water modelling research was conducted to validate these observations and also to design a tuyere that would deliver optimum stirring efficiency. This was combined with the initial observations to define an all refractory design which was patented [3].

Whilst this presents an opportunity to enhance the efficiency of the process, monitoring these improvements remains a challenge. Currently the process is chemically and thermally monitored discretely at long intervals using disposable probes. If continuous measurement of the process were possible it would revolutionise the steelmaking process both in terms of efficiency and product quality and might be considered somewhat of a holy grail of steelmaking. Previous attempts have been made to do this via optical spectroscopy techniques through gas ports below the liquid line, but the stability of these measurements was poor because the port kept being blocked by accretions. The technology developed above offers an opportunity to circumvent these challenges. Conservative calculations predict a net saving per plant is ~£4.5m p.a. Extrapolated to half of globally produced BOF steel this equates to a staggering $1bn.

The project will focus on the development of technology that enables real-time monitoring of chemical
composition and temperature in molten metal furnaces, delivering a step-change in steelmaking productivity. Surprisingly, no such commercial system exists despite the need and benefits outlined above. Hence to realise this opportunity, unique and transformative approaches will be implemented that adapt and combine the latest advancements in refractory manufacturing and laser metrology.