In relation to the climate policy being introduced, the search for a replacement for solid fossil fuels with renewable raw materials is ongoing. In this study, a potential biomass (sunflower husk pellet) application in the process of copper slag reduction was assessed. For the purpose of raw material characterisation, thermogravimetric tests were carried out and characteristic temperature points were determined with the use of a high-temperature microscope. The slag reduction tests led to the recovery of 97% of copper and a decrease in this metal content in the slag to less than 0.5% Cu, which enables safe storage or use in other industrial branches.

The fusibility of ash from woodchip combustion is characterised in the present work. The impact of the increase in MgO, CaO, and Al₂O₃ content in the bio-ash on the classification of ash into categories according to slagging and fouling indices was evaluated. The ash was characterized based on the chemical composition using slagging and fouling indices. However, these ash composition changes did not assign the ash into categories of the indices F_U, S_R, R_S, and B/A (fouling, slagging, slag viscosity, basicity), with less ash inclination to slagging and fouling. The indices were primarily derived for ashes from coal combustion. The indices values characterizing the ash were compared with measured results of ash melting according to STN ISO 540. The measured ash fusibility values showed that the addition of magnesite, limestone, and alumina to dendro-ashes increases the DT (temperature of deformation), HT (temperature of hemisphere), and the AFI (ash fusibility index). There is no conformity between the values of the indices and the measurement of ash fusibility temperatures. In terms of temperatures in the combustion chamber, the measured sintering (T_sin) and DT are suitable for evaluating the tendency of ash to slagging and fouling as well as an accretion of ash particles sticking to the lining.

The interaction of NCC-A (no cement content, with tabular corundum) refractory castable with corrosive refining steel slag CaO–Al₂O₃–SiO₂–MgO–(FeO, MnO) was studied with static crucible corrosion tests. The corrosion process was evaluated using chemical and phase analyses, and the macro- and microstructures on the corrosion boundary of slag–refractory materials were investigated. We describe the corrosion progress and explain the NCC-A corrosion mechanism by oxide metallurgical slags. The alumina refractory material surface was wetted with molten oxide slag (contact angle θ_1390°C from 10° to 20°). The slag penetrated through dissolution of the matrix (fine alumina cement), and the Ca–Si–Al slag, enriched with alumina, attacked the corundum grog. Marked changes in the chemical composition of the slag had an impact on the primary crystallization temperature. As the concentration of Al–O complexes increased in the slag, the binding parameters in Si–O complexes changed and complex tetrahedral units (Al–O–Si) and (Al–O–Mg) were created. Analyses of the corrosion interface grog show that calcium ions diffuse through structural defects in the corundum but Mg²⁺ diffusion was not observed. A sharp interface is observed between the slag and the corroded corundum layer. Differences in the chemical composition of the slag in the corrosion zone affected the convention stream, and formed the concave corrosion profile of the crucible.

The study and evaluation of thermo-chemical, physico-chemical and thermo-mechanical properties of ashes is important for maintaining the smooth operation of boilers. Ash fusibility is a characteristic parameter of the fuel. The evaluative criteria predicting the behavior of ash are based on its chemical composition. The criteria used to characterize coal combustion are also used for the biomass combustion ash. Using these criteria the effect of the magnesite addition to dendromass ash was evaluated. The slagging, fouling and fusibility parameters of the original and modified ash with MgCO₃ additive were compared. The ash fusibility index (fusibility temperature) increased significantly, and reactivity of the slag decreased with increasing MgO content in ash. Next, on the high-alumina refractory material, the corrosion test (static crucible corrosion test at 1450 °C/ 7 h) was carried with the dendromass ash with and without magnesite additive. The corrosion was visually evaluated from the degradation of (l-s) interface, and corrosion profile, and changes in the chemical and phase composition of the corrosion medium. The microstructure of the melt-refractory interface was studied by SEM/EDS. The slag preferentially attacks the binder phase of the corundum refractory castable, and a lesser extent the corundum grains. The change in the chemical composition due to the MgCO₃ addition to ash manifested an increase of slag viscosity (slag viscosity index decreased), the wettability reduction of the corundum castable. The presented experiments are an introductory study aimed to reducing the corrosion of refractory materials by the modifying the composition of biomass and waste during their combustion.

Archeological structures connected with iron metallurgy were identified in the outskirts of the town Lučenec, Slovakia. Based on the shapes and decoration of the ceramic fragments, it was possible to date them to the 9th or 10th century. The first group of discovered metallurgical materials included slags with low wüstite content, which looks like slag from younger higher-shaft furnaces. The second group included slags which could be attributed to the technology common at the time of the site’s existence: iron smelting in lower free-standing shaft furnaces with average efficiency. The third group were slags from the forging of iron blooms to remove pores and slag particles. The fourth group consisted of ceramics fragments (tuyeres and refractory material). Bog ore was probably smelted using principally oak wood charcoal.