The paper presents the simulation of a catalyst-paraffin oil slurry hydrodynamics under high pressure and temperature in a convex bottom reactor with a Rushton turbine which was conducted with an application of computational fluid dynamics (CFD) modeling. An analysis to obtain a uniform distribution of solid catalyst particles suspended in paraffin oil was carried out as a potential for biomass liquefaction. The effects of the particle diameter, bed density, liquid viscosity, and the initial solid loading on slurry hydrodynamics in high pressure and temperature behavior were investigated using the Eulerian–Eulerian two-fluid model and the standard k-ε turbulence model. The main objective was to assess the performance in agitating highly concentrated slurries to obtain slurry velocity, concentration, the degree of homogeneity, and to examine their effect on the mixing quality. The results of the analysis are applied to predicting the impact of the most efficient conditions on slurry suspension qualities as potential for biomass liquefaction.

A significant problem in hard coal mining is the utilisation of ventilation air methane (VAM). Two basic methane combustion methods, thermal (homogeneous) and catalytic oxidation, are analysed in detail in this paper. Both processes are compared based on numerical simulations, applying the reaction kinetics developed in previous works, assuming a few typical monolithic reactor packings. The reactor’s mathematical model and kinetic equations are presented. The results are presented graphically as the temperature and reactant concentration distributions along the reactor, assuming different inlet methane concentrations in the VAM, inlet gas temperature and flow velocity. Interstage reactor cooling is simulated with a higher methane concentration for the catalytic process. The energetic problems of the process are analysed in terms of the heat recovery and resulting exergy, as well as the Carnot efficiency. The problem of toxic carbon monoxide emissions is also modelled and discussed, and the pros and cons of both VAM combustion methods are identified.

Methane (CH₄) is one of the most important greenhouse gases, and substantially impacts climate change. Over a 20-year period, its global warming potential (GWP) is approximately 80 times higher than that of carbon dioxide (CO₂). One of the significant sources of methane emissions is the hard coal mining industry, particularly regarding the release of methane with mine ventilation air. Methane released from coal seams during mining operations and discharged into the atmosphere through exhaust shafts is referred to as VAM (Ventilation Air Methane). In the context of the European Union’s climate policy, activities aimed at reducing and utilizing VAM emissions are gaining increasing importance. One initiative supporting the development of such solutions is the research project ProVAM (Reduction of Ventilation Air Methane Emissions in the Coal Mining Transformation Process), implemented by a consortium of scientific and industrial institutions from EU member states. The project focuses on developing guidelines and selecting technologies dedicated to the utilization of VAM. This article presents a methodology for assessing parameters associated with VAM emissions and provides a characterization of the selected mine exhaust shafts analyzed within the ProVAM project. Key technical factors affecting the feasibility of using oxidation technologies to reduce methane emissions from hard coal mining are identified.

The presented results describe the effect of severe plastic deformation on the structure and mechanical properties of AA5083 and AA5754 alloys. Both materials were subjected to single hydrostatic extrusion (HE) and cumulative hydrostatic extrusion in the case of AA5083 and a combination of plastic deformation by equal-channel angular pressing (ECAP) with the next HE for AA5754. After the deformation, both alloys featured a homogeneous and finely divided microstructure with average grain size deq = 140 nm and 125 nm for AA5083 and AA5754, respectively. The selection of plastic forming parameters enabled a significant increase in the UTS tensile strength and YS yield stress in both alloys – UTS = 510 MPa and YS = 500 MPa for alloy AA5083 after cumulative HE, and 450 MPa and 440 MPa for alloy AA5754 after the combination of ECAP and HE, respectively. It has been shown on the example of AA5083 alloy that after the deformation the threads of the fasteners made of this material are more accurate and workable at lower cutting speeds, which saves the cutting tools. The resultant properties of AA5083 and AA5754 alloys match the minimum requirements for the strongest Al-Zn alloys of the 7xxx series, which, however, due to the considerably lower corrosion resistance, can be replaced in many responsible structures by the AA5xxx series Al-Mg alloys presented in this paper.

A protective coating was developed on a biodegradable MgZn1Ca0.2Li1 alloy via micro-arc oxidation (MAO) method in a KOH + KF electrolyte. The coating, composed of MgF2, KMgF3, and MgO phases, uniformly covers the substrate material, exhibiting moderate surface roughness. Comprehensive analysis using XRD along with scanning and transmission electron microscopy cross-sectional observations, supported by the acquisition of diffraction patterns and EDS spectra, was conducted to confirm the nanocrystalline structure as well as the phase and elemental distribution. Electrochemical tests showed a tenfold decrease in corrosion current and a significant increase in polarization resistance. Hydrogen evolution was effectively suppressed, confirming protective barrier function. The use of environmentally friendly KOH and KF-containing electrolyte ensures the non-toxicity of the deposition process, resulting in the protection of future biodegradable implant surfaces. The results support the potential of this coating for orthopedic applications.

Ventilation air methane (VAM) oxidation in regenerative thermal oxidizers (RTOs) can substantially reduce greenhouse gas (GHG) emissions from underground coal mines, but its environmental effectiveness depends on the operational energy demand. This study evaluates the trade-off between climate benefits and energy penalty using a life-cycle assessment (LCA) approach. Three methane concentration scenarios (0.1, 0.326, 0.5 vol.% CH₄) representing different operating regimes were analyzed. Environmental performance showed strong concentration-dependent response associated with the transition from non-autothermal to autothermal operation. Under autothermal conditions (0.326 and 0.5 vol.% CH₄), life-cycle GHGs were reduced by approximately 90% compared with direct methane release. At 0.1 vol.% CH₄, substantial auxiliary heating was required, which decreased the net climate benefit. Electricity consumption during operation was a major determinant of the environmental footprint of the system. The results indicate that methane concentration is an important parameter and should be considered together with energy demand and mine-safety constraints when assessing VAM mitigation systems.