Particle physics: how reshaped ore pellets make a more efficient blast furnace
Steel is an essential building block of the modern world but it comes at a high environmental cost – the industry is responsible for around 8 % of annual greenhouse gas emissions worldwide. Much of that comes from the operation of blast furnaces, a necessary step to obtain raw iron. A blast furnace is in essence a giant reactor, into which granular materials, such as pellets of fuel, iron ore and limestone, are introduced. Hot air blasted into the chamber induces physical and chemical changes in these materials, ultimately resulting in the production of liquid iron. “How granular materials are introduced and distributed in the blast furnace affects efficiency of the operation in terms of energy consumption and CO2 emissions,” explains DECRON project lead Charley Wu. Studying that distribution directly, however, is extremely difficult, as the chamber is lined with layers of heat-refracting bricks and operates at around 1 500 °C. “The design of blast furnaces hasn’t evolved much in 300 years, but because it’s such a large and complex device, you can’t put detailed experimental testing equipment inside,” says researcher Nicolin Govender. “It’s pretty much a black box.” To resolve this issue, the pair applied a technique called the discrete element method (DEM) with irregularly shaped particles on graphics processing unit (GPU) platforms, which model the behaviour of granular materials digitally. DEM has a wide range of applications, including construction, mining, agriculture, and even pharmaceuticals, where it helps ensure drugs are mixed evenly with fillers before being compressed as pills. At the University of Surrey, Wu and Govender examined how the size and shape of pellets used in smelting affect the way hot gases flow through the reactor chamber. “In blast furnaces, material is introduced at the top, and air at the bottom, so granular packing affects how the gas goes through the material,” explains Wu. Controlling granular packing and the flow of this hot gas is key to the successful operation of a blast furnace. “We found many of the approximations people use are oversimplified, resulting in inconsistent results in the final product,” notes Govender. He adds that the work also identified a number of significant factors, such as energy efficiency, that could be controlled by changing the shape of the pellets. This research was undertaken with the support of the Marie Skłodowska-Curie programme. “The project was a success and generated a number of papers, as well as laying the groundwork for others studying granular material and shape, as well as blast furnace operators,” Govender points out. Three of these papers are among the top 10 most cited works in chemical engineering worldwide. EU metal producers are under increasing pressure from foreign operators, who benefit from lower labour costs and less stringent environmental standards. Govender comments that the project shows how efficiency computer modelling techniques could potentially make the industry more profitable, less energy intensive and greener, helping to bring raw material production back into the EU market.
Keywords
DECRON, iron, ore, blast, furnace, green, GPU, DEM, steel, CO2, granular, smelting
