Superalloys are a group of alloys developed for use during long-term heat exposure above 650 °C. Properties and applications of superalloys are described in the present work. The work includes statistics about superalloys demand, market value and the current price. Division of superalloys according to basic element is mentioned. Nickel-based superalloys are further divided into two groups according to their use. Afterwards, the paper is focused mainly on nickel-based superalloys. Examples of nickel-based superalloys are listed in the work. Recycling possibilities of nickel-based superalloys are stated and analysed. General scheme of processing nickel-based superalloy scrap with regard to the content of rhenium is proposed and shortly discussed. The best-known companies dealing with superalloy scrap recycling are mentioned further.

This study presents a theoretical and practical evaluation of zinc evaporation from bottom zinc dross (hard zinc) as a secondary zinc source (zinc content approximately 94–97%), which originates in the batch hot-dip galvanizing process. The thermodynamics of the zinc evaporation process were studied under the normal pressure (100 kPa) in the inert atmosphere, using argon with flow rate 90 mL/min. Samples were subjected to the evaporation process for 5, 10 and 20 min under the temperature of 700 °C and 800 °C, respectively. For the theoretical thermodynamic study, HSC Chemistry 6.1 software was used and final products, as well as residuals after the evaporation process, were analyzed by SEM (Scanning Electron Microscopy) and EDX (Energy Dispersive X-ray). Calculated and experimental argon consumption in the process of zinc evaporation has been compared. A high purity zinc with efficiency over 99% was reached. Due to a dynamic regime, argon consumption at the temperature of 700 °C and 800 °C were 7 times and 3 times, respectively, less than calculated.

In the present study, the recycling process of bottom zinc dross was performed by evaporation and subsequent condensation at 800 °C for 30 min with an observed argon flow rate of 100–400 mL/min to ensure an inert atmosphere, to observe the evaporation rate and final form of the product. Under the set conditions of over 98% zinc purity, products in the form of nanofibres (thickness 500 nm), powder (size of spherical particles 2–5 μm), dendrites, and metallic forms were obtained. The employed mathematical modelling (via Ansys 2023R1 software) predicted the behaviour of the argon flow current in the quartz tube, as well as the temperature gradient in the quartz tube and in the close vicinity of the zinc sample. Via Inventor 2014 software, the rate of zinc sample heating was calculated. All the simulations were compared with the physical measurements and correlation was proven.

This paper presents the results of increasing the hydrogen concentration in natural gas distributed within the territory of the Slovak Republic. The range of hydrogen concentrations in the mathematical model is considered to be from 0 to 100 vol.% for the resulting combustion products, temperature, and heating value, and for the scientific assessment of the environmental and economic implications. From a technical perspective, it is feasible to consider enriching natural gas with hydrogen up to a level of 20% within the Slovak Republic. CO₂ emissions are estimated to be reduced by 3.76 tons for every 1 TJ of energy at an operational cost of EUR 10,000 at current hydrogen prices.

Hydrogen-enriched natural gas can reduce direct carbon emissions from industrial heat-treatment furnaces, but its effect should be evaluated at the required process temperature rather than only at constant burner input. This study investigates 0–100 vol.% H₂ firing in the radiant-tube preheating chamber of a 108-burner industrial continuous annealing line using a zone-based mathematical model coupling combustion stoichiometry, heat transfer, and furnace energy balances. Archived natural-gas production data were additionally used as a plant-scale consistency check; a separate 2022 campaign was reproduced with a fuel-demand MAPE of 7.41% and NRMSE of 7.92%. At constant burner input, increasing H₂ from 0 to 100 vol.% increased the predicted combustion-gas inlet temperature from 1986 to 2239 °C and the strip outlet temperature from 615.1 to 636.5 °C, while the effective heat-transfer coefficients decreased overall. Under the process-equivalent condition, burner input was adjusted to maintain the 615.13 °C reference strip outlet temperature. At 100 vol.% H₂, the required burner input decreased from 44.84 to 42.44 kW per burner, corresponding to 5.35% and 2.05 GWh y⁻¹ for the full chamber. Sensitivity analysis gave a 4.97–5.79% reduction range, supporting an approximately 5–6% furnace-specific burner-load reduction.

Copper converter flue dust (CFD) is one of the solid wastes generated during the pyrometallurgical production of secondary copper. Due to its fine-grained character and its content of toxic heavy metals, CFD is classified as hazardous waste. CFD contains lead, zinc, and tin in the form of oxides. The aim of this paper is to design a complex hydrometallurgical process for CFD treatment in order to obtain commercially saleable products based on zinc, tin, and lead. The proposed CFD treatment process consists of leaching in acetic acid, cementation of lead from leachate by zinc, and subsequent precipitation of zinc with carbonate ions.