As the iron and steel industry needs to cut its CO₂ emissions drastically, much effort has been put into establishing new—less greenhouse-gas-intensive—production lines fueled by hydrogen and electricity. Blast furnaces, as a central element of hot iron production, are expected to lose importance, at least in European production strategies. Yet, blast furnaces could play a significant role in the transitional phase, as they allow for the implementation of another CO₂-reducing fuel, carbonized wood reducing agents, as a substitute for coal in auxiliary injection systems, which are currently widely used. Wood carbonization yields vastly differing fuel types depending on the severity of the treatment process, mainly its peak temperature. The goal of this study is to define the lowest treatment temperature, i.e., torrefaction temperature, which results in a biogenic reducing agent readily employable in existing coal injection systems, focusing on their conveying properties. Samples of different treatment temperatures ranging from 285 to 340 °C were produced and compared to injection coal regarding their chemical and mechanical properties. The critical conveyability in a standard dense-phase pneumatic conveying system was demonstrated with a sample of pilot-scale high-temperature torrefaction.

Bei der Pressfiltration kann es neben einer plastischen Verformung des Kuchens auch zu einer Volumenvergrößerung des Kuchens kommen, wenn die mechanischen Kräfte reduziert werden, wie Versuche mit einer wässrigen Kohlesuspension zeigen. Ist der Kuchen während dieses Vorgangs mit einem Flüssigkeitsfilm in Kontakt, tritt eine Wiederbefeuchtung des Kuchens ein und der Trockengehalt des Kuchens sinkt. Wenn ein konsequentes Abführen der Flüssigkeit gelingt, kann der Trockengehalt signifikant gesteigert mit einem niedrigeren Pressdruck das Auslangen gefunden werden.