Abstract
Iron-based industries are one of the main contributors to greenhouse gas (GHG) emissions. Partial substitution of fossil carbon with renewable biocarbon (biomass) into the blast furnace (BF) process can be a sustainable approach to mitigating GHG emissions from the ironmaking process. However, the main barriers of using biomass for this purpose are the inherent high alkaline and phosphorous contents in ash, resulting in fouling, slagging, and scaling on the BF surface. Furthermore, the carbon content of the biomass is considerably lower than coal. To address these barriers, this research proposed an innovative approach of combining two thermochemical conversion methods, namely hydrothermal carbonization (HTC) and slow pyrolysis, for converting biomass into suitable biocarbon for the ironmaking process. Miscanthus, which is one of the most abundant herbaceous biomass sources, was first treated by HTC to obtain the lowest possible ash content mainly due to reduction in alkali matter and phosphorous contents, and then subjected to slow pyrolysis to increase the carbon content. Design expert 11 was used to plan the number of the required experiments and to find the optimal condition for HTC and pyrolysis steps. It was found that the biocarbon obtained from HTC at 199 °C for 28 min and consecutively pyrolyzed at 400 °C for 30 min showed similar properties to pulverized coal injection (PCI) which is currently used in BFs due to its low ash content (0.19%) and high carbon content (79.67%).
Highlights
IntroductionIn Canada, about 5.8 Mt of metal is produced by blast furnace (BF) ironmaking processes per year, which is approximately 80% of the total Canadian metal production [1]
Among all steel production routes, the blast furnace (BF) ironmaking process is considered the most popular technology to meet the increasing metal demand worldwide [1,2].In Canada, about 5.8 Mt of metal is produced by BF ironmaking processes per year, which is approximately 80% of the total Canadian metal production [1].In this process, carbon in the form of coke ignites and burns in the presence of sub-stoichiometric amount of air to produce carbon monoxide
We propose a novel hybrid hydrothermal and slow pyrolysis process that is expected to have the synergistic benefits of both processes to produce biocarbon with low alkaline and phosphorous content, and with higher carbon content from agricultural biomass
Summary
In Canada, about 5.8 Mt of metal is produced by BF ironmaking processes per year, which is approximately 80% of the total Canadian metal production [1]. In this process, carbon in the form of coke (produced by heating coal in the absence of air) ignites and burns in the presence of sub-stoichiometric amount of air to produce carbon monoxide. Carbon in the form of coke (produced by heating coal in the absence of air) ignites and burns in the presence of sub-stoichiometric amount of air to produce carbon monoxide This carbon monoxide is used to reduce the metal oxide to metal and make carbon dioxide [3]. BFs consume 12.31 GJ of energy and release 1.8 ton CO2 for the production of one ton of metal [4,5]
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