Temperature Profile Mapping over a Catalytic Unit of a Hydrogen Passive Autocatalytic Recombiner: An Experimental and Computational Fluid Dynamics Study

Abstract

Passive autocatalytic recombiners (PARs) are used for the removal of accidentally released hydrogen inside confined spaces. The high catalyst surface temperature is an important safety issue to be considered in the use of a PAR. The ability to predict the catalyst surface temperature could be very useful in preventing the self-ignition and explosion of hydrogen inside the PAR. This study seeks to investigate the changes in temperature profiles of the PAR catalytic section upon variation of the inlet hydrogen concentration. Experiments were conducted on a small-scale test setup. The catalytic section comprised cylindrical ceramic elements arranged in parallel and held upright by a stainless-steel frame. The temperature profiles were measured with a high-resolution infrared camera. The commercial computational fluid dynamics (CFD) code STAR-CCM+ was used as a numerical tool for modeling the gas mixture flow inside the experimental setup and the chemical reaction kinetics. The results of numerical studies are presented and compared with experimental results. The presented CFD-based approach and software offer an appropriate numerical tool for the investigation of hydrogen safety issues. Finally, the catalyst was subjected to a prolonged high-temperature combustion fatigue procedure to determine its stability. The surface of the fatigued catalyst was evaluated by scanning electron microscopy and energy-dispersive X-ray spectroscopy. It was found that decomposition of the protective surface layer occurred at elevated temperatures; the catalytic activity was unaffected by this. In addition, a relatively uniform reactive metal particle size was maintained over the entire temperature range, suggesting that no aggregation occurred.

Catalytic Hydrogen Combustion for Domestic and Safety Applications: A Critical Review of Catalyst Materials and Technologies

“…The performance of the PAR was evaluated for inputs of hydrogen concentrations in a range 2-5 vol%. In addition, the experimental results were compared with CFD simulated results, and they were in good agreement [131]. Therefore, PARs will likely play a key role in underground mining and NPPs' accident mitigation in the future.…”

“…A similar catalyst section was tested in a study by ; the catalyst manufacturer was not specified. The authors found a ∆T of 341.2 • C over a tubular ceramic Pt/Al 2 O 3 washcoat catalyst [131].…”

“…Catalysts containing dispersed nano-sized Pt particles are typically highly active and are used in various hydrogen-based technologies, e.g., electrochemical hydrogen compression, PEMFCs, PEM water electrolysis, and LOHC dehydrogenation [73,[128][129][130][131][132][133][134][135][136][137][138][139][140]. In general, reducing reactive metal loadings has been a primary research focus, and catalyst development (e.g., catalyst stability and durability) has received relatively limited attention.…”

Review of Catalysts, Substrates, and Fabrication Methods in Catalytic Hydrogen Combustion with Further Challenges and Applications

“…The PARs are used to apply the CHC process to remove hydrogen from the catalytic surface. Several types of PARs were studied and tested. − …”

Preparation of a Cartridge-Type Pt/Al2O3 Catalyst Using a Sputter Deposition Method for Catalytic Hydrogen Combustion

“…A temperature gradient (ΔT) of only 23 °C was recorded over 70 mm of the catalyst surface at 3 vol % hydrogen. By comparison, Malakhov et al 48 recorded a ΔT of 341 °C over a tubular ceramic Pt/Al 2 O 3 washcoat catalyst for a 75 mL/min hydrogen flow. According to Appel et al, 49 to suppress high entry temperatures of the Pt/Al 2 O 3 /SiC catalyst, the initial catalyst section must be efficiently cooled.…”