No abstract

The strength of coke is of major importance for efficient blast furnace operation. There are only a few studies related to compressive coke hot strength, possibly due to experimental difficulties. In this work, it has been demonstrated that the Gleeble thermomechanical simulator is suitable for evaluating coke hot strength and offers many benefits compared to purpose‐built devices reported in the literature. This finding could open coke hot strength research to a wider number of scientists. The compressive hot strength of coke was evaluated at 1000 and 1600°C by testing 50 samples at both temperatures. The yield strength and ultimate strength of the coke were, respectively, 46 and 20% lower at 1600°C than 1000°C. Stress–strain curves showed that the coke was brittle at 1000°C but partially plastic at 1600°C. The significantly lower coke strength at 1600°C could help explain the smaller coke lump size found near the tuyere level in quenched blast furnaces.

The utilization of biomass fly ash and lime was investigated as cement replacements in blast furnace briquetting. Sample characterization included chemical (XRF) and mineralogical (XRD) analysis, particle size determination, and thermal behaviour (TGA/DSC-TGA). Additionally, the mechanical performance and fly ash, lime, and fly ash/lime mixtures as cement replacements were determined by incorporation in mortars tested by standardized methods (EN 196-1). Based on the results, detrimental alkali, sulphur, and chlorine contents of the biomass fly ashes do not seem to restrict use in briquetting. However, the utilization of fly ashes as cement replacements resulted in significant decline of 28 day compression strength values. The two different fly ash samples attested to 28 day compression strength of app. 72% and 55% of the respective control. Inferior mechanical performance was related to moisture absorption according to XRD and DSC-TGA and relatively larger particle size. Respectively, lime additions encouraged fly ash strength development only in the case of inferior fly ash performance related to the aforementioned effects. The results provide important information for the forthcoming manufacture of blast furnace test briquettes, which is to commence in the near future.

No abstract

The campaigns of the AOD and chromium converters are often limited by the strong wear of the refractory materials in certain areas (usually tuyere zone). Slag protection (in which the slag is left to solidify at the converter walls after the tapping of the metal) has been considered to be an option in prolonging the campaigns of the converters. In order to study the possibilities of the slag protection, the purpose of this work was to determine the melting behaviour of the AOD and chromium converter slags; i. e. the solidus and liquidus temperatures and the composition of solid phases as a function of temperature in different slag compositions. Examination was executed using both computational (FactSage software) and experimental (optical diiatometerlSEM) methods. It was noticed that when burned dolomite was added into the slags, the increased MgO-contents had a strong influence on the melting behaviour. Even small changes (a few percent) in the MgO-content had a very strong influence (a few hundred degrees centigrade) on the solidus and liquidus temperatures. Solid phases that are formed during the solidification are also different in slags with and without burned dolomite addition.