Neste Oil (Finland)

This study introduces a dynamic simulation model for an industrial-scale atmospheric alkaline water electrolyzer system. The model is parametrized and validated using measurement data from a real 1-MW atmospheric electrolyzer supplying hydrogen to an industrial process. The system behavior and energy losses are studied by simulating steady-state operation at a range of operational loads. As load decreases, energy efficiency improves, in contrast to previously published results concerning a 3-MW 16-bar system. This can be attributed to better stray-current management in the atmospheric system, promoted in part by maintaining high gas-volume fractions in the stack’s outlet manifold channels, which in turn is achieved with a lower lye circulation flow rate. Noteworthily, water vaporization inside the generated gas bubbles cools down the stack and maintains the temperature difference between its inlet and outlet at beneficial levels when less heat is removed from the stack by the reduced lye flow. This can be regarded as a fundamental benefit of the atmospheric stack design compared to its pressurized counterpart, in which less water vaporization occurs. This work benefits future studies comparing atmospheric and pressurized electrolyzer systems and provides a tool for optimizing energy and cost efficiencies in megawatt-scale Power-to-X applications leveraging water electrolysis. • Atmospheric stacks are inherently less prone to stray currents than pressurized ones. • Stack cooling from atmospheric water vaporization allows lower lye flow rates. • Lower lye flow rate increases manifold gas voidage and helps reduce stray currents. • At nominal load, stray currents consume 1% of stack DC power, overpotentials 23%. • From 100% to 20% load, specific energy consumption decreases from 52 to 47 kWh/kg H2 .

Abstract Decarbonizing the aviation sector is one of the biggest challenges to minimize climate change effects associated with carbon dioxide emission. Sustainable aviation fuels will play a major role in this context especially for long-distance flights where hydrogen or all-electric propulsion systems do not present a feasible alternative. In addition, aromatic-free sustainable aviation fuels offer a promising solution to lower soot emissions of aeroengines. Jet A-1 as reference fuel, two blends, and two neat synthesized paraffinic kerosenes (SPKs) from hydroprocessed esters and fatty acids (HEFA) were tested to characterize the combustion behavior of drop-in/near drop-in fuels. Experiments in an optically accessible high-pressure rich-quench-lean (RQL)-type combustor at typical aeroengine conditions were performed using optical diagnostics, exhaust gas, and particle sampling measurements to delineate the fuel effects on spray, flame, and emission characteristics. Measurements were performed at pressures up to 10 bar, air preheating temperatures up to 773 K and primary zone equivalence ratios up to 1.66. Liquid fuel distribution and fuel placement were found to be sensitive to fuel properties. By contrast, no pronounced influence on flame position and shape were observed. As a consequence, NOx and CO emissions of the tested fuels differed only moderately. However, particulate matter measurements at the fuel richest operating condition showed a clear fuel ranking with the lowest particle emissions evident for the two neat HEFA-SPK samples. Moreover, the particle volume concentration at the fuel richest condition followed the expected trend with fuel H-content.

Abstract Aviation is widely recognized as a significant source of air pollutant emissions, encompassing gaseous products such as CO2, CO, NOx, and particulate matter (PM), especially in the form of soot. This study conducted comprehensive emission measurements on an Allison 250 C20B turboshaft engine to investigate sustainable aviation fuel (SAF) impact on emissions. Two conventional Jet A-1 fuel blends with 30% and 50% HEFA-SPK synthesized paraffinic kerosene derived from hydro-processed esters and fatty acids (HEFA-SPK) content together with 100% HEFA-SPK were tested regarding their emissions and compared against neat Jet A-1. The study’s primary focus was quantifying ultrafine particulate matter in terms of number and size. The selection of distinct engine power settings was based on the thrust ratios specified in the International Civil Aviation Organization’s (ICAO) Landing and Take-off-cycle (LTO-cycle). PM emissions were characterized using multiple measurement techniques. These included the application of two distinct electrical mobility analyzers. An additional concentration particle counter (CPC) was utilized to underscore the reliability of the findings. A standard FTIR/O2/FID system was used to assess gaseous emissions, a well-established method for measuring fundamental combustion products such as CO2, CO, unburned hydrocarbons (UHC’s) and NOx. The particle measurement systems revealed a decrease in both the number and size of particles with increasing HEFA-SPK content. This decrease in particle number appeared linear for the 30% and 50% HEFA-SPK blends and was more pronounced for the 100% HEFA-SPK. Furthermore, a more substantial reduction in PM emissions, reaching up to 82%, was observed at lower load settings, such as Ground Idle (GI), compared to higher load settings like Take-Off (TO), where the reduction was up to 40%. Results of the gaseous emissions are also presented in the study.

Active catalysts for simultaneous hydrodeoxygenation (HDO) and hydrodenitrogenation (HDN) enable the production of fuels from renewable feedstocks. In this work, zirconia-supported nickel, ruthenium, rhodium, palladium, and platinum catalysts were evaluated in the HDO and HDN of n-hexadecanamide (C16 amide). The HDN of 1-hexadecylamine (C16 amine) was studied separately to assess the HDN activity and the preference between C–C and C–N bond cleavage routes without the interference of HDO. The differences in the catalytic activity were mainly attributed to the metal identity. Pt/ZrO2 and Ru/ZrO2 exhibited the highest activity toward the conversion of both model compounds. The C16 amide was converted more efficiently than the C16 amine over the studied catalysts, and a high HDO activity did not translate to a high activity in HDN, which was particularly evident in the case of Rh/ZrO2. The active metal strongly influenced the preferred reaction routes, as observed from differences in the yields of C15 and C16 n-paraffins and C32 condensation products. Ni/ZrO2 and Pd/ZrO2 exhibited the lowest activity and paraffin selectivity in the hydrotreatment of both model compounds. Ru/ZrO2 and Rh/ZrO2 favored the formation of n-pentadecane from both the C16 amine and C16 amide, whereas Pt/ZrO2 produced n-hexadecane and high intermediate yields of the C32 condensation products.

Active catalysts for simultaneous hydrodeoxygenation (HDO) and hydrodenitrogenation (HDN) enable the production of fuels from renewable feedstocks. In this work, zirconia-supported nickel, ruthenium, rhodium, palladium and platinum catalysts were evaluated in the HDO and HDN of n-hexadecanamide (C16 amide). The HDN of 1-hexadecylamine (C16 amine) was studied separately to assess the HDN activity and preference between C–C and C–N bond cleavage routes without the interference of HDO. The differences in the catalytic activity were mainly attributed to the metal identity. Pt/ZrO2 and Ru/ZrO2 exhibited the highest activity towards the conversion of both model compounds. The C16 amide was converted more efficiently than the C16 amine over the studied catalysts, and a high HDO activity did not translate to a high activity in HDN, which was particularly evident in the case of Rh/ZrO2. The active metal strongly influenced the preferred reaction routes, as observed from differences in the yields of C15 and C16 n-paraffins and C32 condensation products. Ni/ZrO2 and Pd/ZrO2 exhibited the lowest activity and paraffin selectivity in the hydrotreatment of both model compounds. Ru/ZrO2 and Rh/ZrO2 favored the formation of n-pentadecane from both the C16 amine and C16 amide, whereas Pt/ZrO2 produced n-hexadecane and high intermediate yields of the C32 condensation products.

Active catalysts for simultaneous hydrodeoxygenation (HDO) and hydrodenitrogenation (HDN) enable the production of fuels from renewable feedstocks. In this work, zirconia-supported nickel, ruthenium, rhodium, palladium and platinum catalysts were evaluated in the HDO and HDN of n-hexadecanamide (C16 amide). The HDN of 1-hexadecylamine (C16 amine) was studied separately to assess the HDN activity and preference between C–C and C–N bond cleavage routes without the interference of HDO. The differences in the catalytic activity were mainly attributed to the metal identity. Pt/ZrO2 and Ru/ZrO2 exhibited the highest activity towards the conversion of both model compounds. The C16 amide was converted more efficiently than the C16 amine over the studied catalysts, and a high HDO activity did not translate to a high activity in HDN, which was particularly evident in the case of Rh/ZrO2. The active metal strongly influenced the preferred reaction routes, as observed from differences in the yields of C15 and C16 n-paraffins and C32 condensation products. Ni/ZrO2 and Pd/ZrO2 exhibited the lowest activity and paraffin selectivity in the hydrotreatment of both model compounds. Ru/ZrO2 and Rh/ZrO2 favored the formation of n-pentadecane from both the C16 amine and C16 amide, whereas Pt/ZrO2 produced n-hexadecane and high intermediate yields of the C32 condensation products.

Active catalysts for simultaneous hydrodeoxygenation (HDO) and hydrodenitrogenation (HDN) enable the production of fuels from renewable feedstocks. In this work, zirconia-supported nickel, ruthenium, rhodium, palladium and platinum catalysts were evaluated in the HDO and HDN of n-hexadecanamide (C16 amide). The HDN of 1-hexadecylamine (C16 amine) was studied separately to assess the HDN activity and preference between C–C and C–N bond cleavage routes without the interference of HDO. The differences in the catalytic activity were mainly attributed to the metal identity. Pt/ZrO2 and Ru/ZrO2 exhibited the highest activity towards the conversion of both model compounds. The C16 amide was converted more efficiently than the C16 amine over the studied catalysts, and a high HDO activity did not translate to a high activity in HDN, which was particularly evident in the case of Rh/ZrO2. The active metal strongly influenced the preferred reaction routes, as observed from differences in the yields of C15 and C16 n-paraffins and C32 condensation products. Ni/ZrO2 and Pd/ZrO2 exhibited the lowest activity and paraffin selectivity in the hydrotreatment of both model compounds. Ru/ZrO2 and Rh/ZrO2 favored the formation of n-pentadecane from both the C16 amine and C16 amide, whereas Pt/ZrO2 produced n-hexadecane and high intermediate yields of the C32 condensation products.