Advanced Simulation Model as a Strategic Enabler of Emissions Reduction in Blast Furnace Operations

Steel is a foundational material in the global economy, with its production still heavily reliant on the blast furnace process, which remains the dominant method for converting iron ore into molten iron. This process, however, is inherently carbon-intensive, making the blast furnace one of the largest contributors to CO2 emissions globally. Despite this environmental impact, the blast furnace remains difficult to replace due to its high productivity, favourable thermodynamic efficiency, and cost-effectiveness at scale. Its proven ability to process a wide range of iron ore qualities, integrate various energy inputs, and consistently deliver high-quality hot metal of uniform composition makes it a highly versatile and resilient technology, crucial for meeting the growing global demand for steel. Still, in light of the ongoing climate emergency, a fundamental transformation of the blast furnace towards significantly lower emissions is required. Multiple decarbonisation technologies are currently under development, each at varying stages of maturity. These include the integration of hydrogen-rich sources in the furnace, top gas recycling through diverse methods, shaft injection of reducing gas, and partial electrification via gas plasma heating, to name a few. The development, optimisation, and successful deployment of such innovative decarbonisation technologies are challenged by the sheer scale and extreme operating conditions of the blast furnace, which make direct measurement of internal variables particularly difficult. In this context, numerical modelling plays a crucial role in acquiring the necessary insights and understanding to support technology advancement. The aim of this doctoral thesis is to develop a robust predicting model of the blast furnace process and to apply it in the evaluation of various low-emission configurations. Emphasis is placed on EASyMelt, the solution developed by Paul Wurth S.A. to decarbonise existing blast furnaces worldwide. The approach strategically integrates multiple CO2 reduction technologies, in particular multi-level gas injection, top-gas recycling, plasma heating for direct electrification, and gas reforming, with the aim to drastically reduce the blast furnace environmental impact. A steady state, multiphase, two-dimensional numerical model of the blast furnace has been developed from the ground up. It takes as input the operating conditions and burden distribution within the furnace and predicts both the overall performance and the internal state of the furnace. The model has been validated using data from both an industrial blast furnace and an experimental furnace operating with a high hydrogen load. The results show good agreement between predicted and observed variables, demonstrating the model’s applicability for investigating decarbonisation technologies. As a potential first step towards net-zero steelmaking, the injection of various hydrogenous gases through the blast furnace tuyeres has been investigated. Injection rates were increased to the maximum levels that still ensure a safe and stable operation, and the resulting impact on the internal state of the furnace was analysed. While the approach shows promise, the achievable CO2 reductions remain limited, highlighting the need for more advanced decarbonisation strategies. To support a more comprehensive decarbonisation pathway, various EASyMelt implementation scenarios have been investigated, considering different stages of integration and the use of diverse energy vectors. The analysis reveals a significant impact on the furnace’s thermal state, chemical behaviour, and cohesive zone characteristics, particularly under full implementation of the EASyMelt concept. A thorough understanding of these factors is essential to ensure a successful and efficient deployment. Drastic reduction of emissions was predicted, with the most favourable scenario achieving a 70% saving in scope 1 and 2 emissions of crude steel production. Furthermore, an economic assessment based on predicted process variables indicated that implementing EASyMelt using natural gas and coke oven gas could yield cost savings under the current carbon pricing in Europe, while still yielding significant emission reductions. If the integration of green energy vectors was shown to allow for greater emission reduction, achieving cost neutrality requires a moderate increase in carbon pricing. Still such levels could be reached in the near term. It should be noted that the actual cost implications, CO2 savings, and technical feasibility of EASyMelt implementation will vary depending on the location of the steel plant, existing infrastructure, and operational context. The model developed in this thesis offers a valuable tool for identifying the optimal decarbonisation strategy tailored to specific site conditions.