Anthracite contains more fixed carbon than any other natural coal type. It is therefore a good reducing agent in the metallurgical sector. In steelmaking processes, it is used primarily in conjunction with scrap metal as a charge coal. It acts as both a carbon carrier and an energy source. Life Cycle Assessments conducted nearly twenty years ago on nickel pig-iron revealed the potential for anthracite to replace fossil carbon carriers for production of nickel and other metals.
In addition to the existing conditioning processes such as sintering and briquetting of raw materials, or pre-reduction using a rotary oven (see Figure), bio-based carbon can be directly incorporated into smelting process either as a carbon raiser or if it is used to replace coke. As shown in Figure 6, bio-based CO2 can be added directly to the smelting procedure, either as an additive for carbon or as coke replacement. This is done by adding it in the smelting furnace to enhance the reduction kinetics and thereby to reduce the consumption of fossil reducing agents.
The resultant slags are more reactive and have a reduced melting temperature. There is more ferromanganese in the resultant slag. These can be separated through floatation for pellets of ferromanganese or directly melted in an electric-arc oven to produce ferromanganese (Fig. 7). This method isn't widely used in the industry, and it requires complex engineering. However, it can save a significant amount of raw materials.
Due to its low pressure, hydrogen cannot reduce some ignoble elements like nickel, chrome, and silicon. The development of new reducing agent for these processes will be a key task in the future.
In the case of nickel alloys (chromium manganese silicon), bio-based CO2 can be used as coke replacement. The substitution of conventional carbon by this type of reducing agent has the potential to significantly reduce greenhouse gas emissions, especially those related to carbon sequestration and storage [3, 4]. Anthracite is produced in Russia and South Africa. The feedstock is used to produce nickel-based metals such as nickel pig iron and ferronickel.
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