As the iron and steel industry moves towards a GHG-neutral hydrogen-based reduction process producing H2-reduced DRI for EAF melting, it is essential to find alternative carbon sources. It is important to note that the carbon injection used in the melt process, which produces a foaming action, must be sourced from alternative sources.
Anthracite is the best quality coal. It has a high content of carbon and contains low levels of impurities, such as moisture, ash or volatiles. It's also harder than the bituminous type.
Wood fuel pellets are the most common form of biomass. By burning biomass, the power sector can convert it into electricity. Biomass comes from forest waste, paper mill byproducts, agricultural products, and municipal garbage.
Biofuels are used as alternatives to fossil fuels in the transportation and energy industries. In the industrial process, they can replace kerosene or diesel fuel, as well as natural gas.
Anthracite coal has spent millions years under intense pressure and heat. It has a high fixed carbon content and low volatile matter. This makes it a great carbon donor in metallurgical processing.
With a growing demand for biomass, counties near the steel industry can expect prices to increase and those farther away will see a decrease in price due to transportation costs. The iron and steel chain is similar in many ways to the biomass supply chain.
A major challenge in steel production is stomaching the higher cost for the material. Richter says the premium is often value-engineered out of projects or not included in tenders to start with.
Professor Veena Shajwalla is a recycling scientist who founded and directs the UNSW SMaRT centre. Her Green Steel Technology has helped solve this problem. This uses old rubber tyres, a rich source of carbon, as replacement for some of the coke in electric arc furnace steelmaking.
Sahajwalla and colleagues have also tested HDPE and PP plastics as replacement for some of the coal or anthracite in EAF steelmaking. Their laboratory and industrial scale carburizing experiments using woody biomasses -- commercial sawdust, for example -- and high quality anthracite as the reference material show that the substitution works well. The reaction is also more efficient in terms of iron reduction when compared with coke. It is cheap, and it does not require any explosion protection at the plant.
It is not possible to distinguish between anthracite, and regular coal. Anthracite has the lowest impurities and highest carbon content among fossil fuels. It is denser and has a metallic sheen compared to bituminous coal or lignite.
Traditional coke, while a carbon-heavy fossil fuel, contains less hydrogen that anthracite. Scientists from the University of New South Wales (Sydney), including Veena Sahajwalla who is the 2022 Australian of The Year, developed Polymer Injection Technology in order to substitute a large portion of non-renewable carbon used in electric furnaces for the steel production.
Newcastle mining materials supplier Molycop is one of the first to use this new technology, producing metal wheels for Waratah train service between Sydney and Newcastle. The tires are crumbed and mixed with recycled scrap metal in an electric arc furnace, producing 80 percent less CO2 than the old-fashioned blast furnaces.
With rising scrap prices and higher environmental awareness, steel producers are increasingly moving towards a greener production. Included in this is more recycling of waste and reversing trends towards energy-intensive electric arc furnaces. These changes are also being driven by the decarbonization goal, stricter emission standards and carbon-trading systems.
The UNSW SMaRT Centre developed and patented a technology that uses waste tires and plastic waste as carbon alternatives to coal or anthracite for electric arc furnace steelmaking. The material produced is carbon neutral and can be considered to be fully circular.
The research team is continuing to improve the processing of shredded and/or melted waste plastics into EAF feedstock. This will ensure the steel industry's ability to meet the growing demand for green steel while reducing its greenhouse gas emissions and supporting sustainable development goals. This could be an important contribution to a carbon neutral global economy. It is especially important because the steel industry is being pushed to become carbon neutral by 2050.
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