The use of hydrogen is pivotal for the energy and industrial transition in order to mitigate the effects of climate change. As technologies like fuel cells, e-fuels, and the semiconductor industry increasingly demand pure hydrogen, the development of efficient separation methods is crucial. While traditional methods such as pressure-swing adsorption are common, palladium (Pd)-based membranes are a promising alternative due to their energetic efficiency. This review summarizes the recent advances in Pd-based membranes for hydrogen separation over the last six years. It provides a theoretical overview of hydrogen permeation through membranes and examine the characteristics of various Pd alloys adopted in membrane fabrication, discussing the advantages and disadvantages of binary and ternary alloys, for different membrane types, including self-supported and supported membranes, as well as the role of intermediate layers. Additionally, the membrane characteristics used in some recent works on self-supported and supported Pd membranes are analyzed, focusing on operational parameters like permeability, selectivity, and durability. Finally, this review emphasizes the significant progress made in enhancing membrane performance and discusses future directions for industrial applications.
27 July 2024 in International Journal of Hydrogen Energy
A multiparametric study was conducted on a hydrogen (H2) production rig designed to process 0.25 Nm3·h−1 of syngas. The rig consists of two Pd-Ag membrane permeator units and two Pd-Ag membrane reactor units for the water–gas shift (WGS) reaction, enabling a detailed and comprehensive analysis of its performance. The aim was to find the optimal conditions to maximize hydrogen production by WGS and its separation in a pure stream by varying the temperature, pressure, and steam-to-CO ratio (S/CO). Two syngas mixtures obtained from an updraft gasifier using different gasification agents (air–steam and oxy–steam) were used to investigate the effect of gas composition. The performance of the rig was investigated under nine combinations of temperature, pressure, and S/CO in the respective ranges of 300–350 °C, 2–8 bar, and 1.1–2 mol·mol−1, as planned with the help of design of experiment (DOE) software. The three parameters positively affected performance, both in terms of capacity to separate a pure stream of H2, reported as moles permeated per unit of surface area and time, and in producing new H2 from WGS, reported as moles of H2 produced per volume of catalyst unit and time. The highest yields were obtained using syngas from oxy–steam gasification, which had the highest H2 concentration and was free of N2.
Blade Tip Timing (BTT) is a non-contact, cost-effective technique for monitoring blade vibrations in rotating machinery and has gained widespread adoption in both academic and industrial settings. However, the absence of standardized calibration methodologies for BTT systems remains a significant limitation, potentially affecting the accuracy and reproducibility of measurements. This study addresses this gap by presenting the design, development, and optimization of a calibration test bench, based on the principle of motion decomposition. The proposed calibration system is composed of two independently engineered subsystems: a rotary unit, responsible for generating purely rotational motion without undesired vibrations, and a vibratory unit, designed to impose a controlled oscillatory motion on the sensor under test. Experimental characterization confirmed the mechanical robustness and reliability of the setup across a broad range of frequencies and input voltages. The developed calibration system is versatile, supports multiple sensor types, and is suitable for transonic operating conditions. Its modular and optimized architecture offers a promising foundation for establishing standardized BTT calibration procedures, with the potential to significantly enhance the accuracy and repeatability of blade vibration measurements.
The use of biochar derived from agricultural wood waste represents a promising long-term carbon storage strategy, contributing to mitigation of climate change effects while offering agronomic benefits. This residue is considered as an appropriate material since it does not compete directly with the food chain. Life Cycle Assessment (LCA) is a widely recognized methodology to evaluate the potential environmental impacts associated with all the stages of the life cycle of a product, process or service. In this study, the potential environmental impact of biochar production and its application on soil have been assessed employing a cradle-to-grave approach. The biochar was produced through the pyrogasification of residual lignocellulosic biomass in a pilot-scale plant. The LCA model has been generated employing the GaBi software (LCA for experts 10.7), in accordance with ISO LCA standards and ILCD Handbook, using the experimental results collected during the test carried out in the pilot plant. Two scenarios have been discussed: a basic scenario, involving the biochar production and application on the soil, and an improved scenario, in which by-products from biochar production are used to replace energy in thermal processes. The Global Warming Potential (GWP) of biochar production resulted in −5.52 kg CO2 eq./kg of biochar including the sequestered carbon during plant growth and 1.81 kg CO2 eq./kg of biochar stored in soil and the heat recovery resulted in approximately 20 MJ/kg of biochar of avoided consumption of fossil-based fuels. These findings provide additional support to evaluate biochar potential as an environmentally beneficial solution.