This paper presents the study of oxygen–enriched combustion of natural gas and its impact on nitrogen oxides emission. The research were performed on two experimental stands, i.e. combustion chambers with an industrial swirl burner of maximum power equal to 90 kW and 10 kW. The investigation includes the influenced of oxygen enhanced within the range between 21% and 30%. Furthermore, the role of temperature during the oxygen enrichment was analysed. The results of the research showed that with the rise in oxygen concentration in the air the concentration of nitrogen oxides also increases what is directly related to the rise in flame temperature as well as the addition of oxygen.

The paper analyzes the suitability of four types of biomass pellets as a fuel for heating purposes. Three types of waste biomass (sunflower husks, rapeseed cake, and corn straw) and one type of biomass grown for energy purposes (willow) were selected. After appropriate preparation, the selected starting materials were subjected to the pelletization process. Selected physical and chemical properties of the studied biomass pellets were determined. All four types of the analyzed pellets met the EN-ISO-17225-2:2014 standard in terms of bulk density, dimensions, as well as nitrogen and moisture content. The highest calorific value was pellets made of sunflower husk (17.27 MJ/m³) and willow (16.81 MJ/m³), while the calorific value of pellets made of corn straw and rapeseed cake did not exceed 16.5 MJ/m³ and did not meet the standard. In addition, the ash content for these two types of pellets was well above the standard. A 10 kW domestic biomass boiler was employed for burning the tested pellets. The consumption of analyzed fuels during boiler operation was determined. The concentration of CO, CO₂, and NO_x in exhaust gases was also examined. The obtained experimental results were compared with the numerical calculations with the use of ANSYS Chemkin-Pro using two mechanisms. The highest concentrations of CO₂ and CO were observed during the combustion of sunflower and willow husk pellets, which probably resulted from the highest carbon content and, thus, the highest calorific value when compared to cake and straw pellets. For all analyzed pellets, the value of NO and NO₂ concentration was similar and did not exceed 368 ppm and 18 ppm, respectively. The results closest to the experiment were obtained for calculations using the mechanism developed by Glarborg et al. The research carried out in the article shows that out of the four analyzed types of pellets, only sunflower and willow husk pellets can be burned in a domestic boiler adapted to burning wood pellets, which is a cheap alternative to wood pellets.

Currently, the metallurgical industry in Poland is struggling with the problem of the energy use of process by-products. Coke oven gas (COG) or blast furnace gas (BFG) in accordance with the latest directives should not be a side effect troublesome to manage. They should become an energy carrier that improves the economic and ecological efficiency of the steelworks. The easiest way to manage them is combustion or co-combustion with natural gas directly in the place of production. In the article, simulations of process gas combustion were carried out in the actual operating conditions of a roller-hearth tunnel furnace for sheet hardening, using the Directed Relation Graph with Error Propagation aided Sensitivity Analysis (DRGEPSA) method. The main objective of the analyses was to determine the optimal solution for the use of COG and BFG gases in a heating furnace in the ecological and economic aspect. The conducted analysis shows that co-firing COG and BFG in appropriate proportions is the most advantageous solution. The presented savings resulting from the use of process gases and the heating of the sheet metal in the hardening furnace constitute a remarkable economic aspect of the furnace operation. Considering the growing competition on the steel market, the presented savings are a more advantageous technological solution for Polish steelworks, ensuring a lower price of the final product.

The article describes the computation of the time of heating of a bed of bars in the heat treatment process. The charge was subjected to under-annealing, which is used in industry, e.g., to facilitate sawing of bars or billets into a sections intended for hot forging. The beds under examination were regarded as solid elements, which was possible thanks to the knowledge of the effective thermal conductivity, λ. The value of this quantity for the temperature range under consideration was determined based on the author’s original investigation. During heating of a bundle of bars at a constant heating medium temperature, a temperature difference occurs on the charge cross-section, which is significantly greater than that provided for by the technology. It is therefore essential to carry out a second soaking stage in order to achieve the cross-sectional temperature difference at a level of 20°C. The computation of soaking was conducted for the assumed conditions of a constant temperature on the charge surface and the parabolic distribution of temperature on the cross-section.