Influence of Modified Bio-Coals on Carbonization and Bio-Coke Reactivity

Abstract

Substitution of coal in coking coal blend with bio-coal is a potential way to reduce fossil CO2 emissions from iron and steelmaking. The current study aims to explore possible means to counteract negative influence from bio-coal in cokemaking. Washing and kaolin coating of bio-coals were conducted to remove or bind part of the compounds in the bio-coal ash that catalyzes the gasification of coke with CO2. To further explore how the increase in coke reactivity is related to more reactive carbon in bio-coal or catalytic oxides in bio-coal ash, ash was produced from a corresponding amount of bio-coal and added to the coking coal blend for carbonization. The reaction behavior of coals and bio-coals under carbonization conditions was studied in a thermogravimetric analyzer equipped with a mass spectrometer during carbonization. The impact of the bio-coal addition on the fluidity of the coking coal blend was studied in optical dilatometer tests for coking coal blends with and without the addition of bio-coal or bio-coal ash. The result shows that the washing of bio-coal will result in lower or even negative dilatation. The washing of bio-coals containing a higher amount of catalytic components will reduce the negative effect on bio-coke reactivity, especially with acetic acid washing when the start of gasification temperature is less lowered. The addition of bio-coal coated with 5% kaolin do not significantly lower the dilatation-relative reference coking coal blend. The reactivity of bio-cokes containing bio-coal coated with kaolin-containing potassium oxide was higher in comparison to bio-coke containing the original bio-coal. The addition of ash from 5% of torrefied bio-coals has a moderate effect on lowering the start of gasification temperature, which indicates that the reactive carbon originating from bio-coal has a larger impact.

A Study on Bio-Coke Production—The Influence of Bio-Components Addition on Coke-Making Blend Properties

“…The decrease in dilatation, along with the addition of 5 and 10% biomass substances (torrefied pine/spruce woodchips, sawdust and high temperature torrefied pellets) was also reported by El-Tawil et al [31]. This tendency was also observed for 5% of additives after modification (e.g., washing, kaolin coating) [14].…”

“…Moreover, replacing a certain part of the coking coal with biomass is beneficial from the point of view of reducing its consumption-coking coal is a scarce resource and is included in the list of EU critical raw materials. Therefore, in recent years, there has been a great deal of interest in the subject of bio-coke production, i.e., coke produced from blends of coking coals and biomass-derived materials [8][9][10][11][12][13][14][15][16][17][18]. It is not an easy task, because in order to produce coke, it is necessary to use coking coals with appropriate coking properties and the addition of other raw materials, including even other coals (non-coking), usually does not have a positive effect on the above-mentioned coking properties of the prepared blend.…”

Actual Trends in the Usability of Biochar as a High-Value Product of Biomass Obtained through Pyrolysis

“…This phenomenon in combination with the release of elemental oxygen from combustible matter causes a deterioration of plastometric layer formation [110]. Reports have described that a few percent share of raw biomass in the coke blend negatively impacts the quality of coke by simultaneously increasing its reactivity and reducing its mechanical strength [111]. Therefore, to introduce a greater share of biocomponent without promoting deterioration of the quality of the final product, bio-coke, pre-processes of biomass must be examined to form a product similar to coal, such as biochar.…”