Progress in Mo/W-based electrocatalysts for nitrogen reduction to ammonia under ambient conditions

Ammonia (NH3), possessing high hydrogen content and energy density, has been widely employed as fertilizers and value-added chemicals in green energy carriers and fuels. However, the current NH3 synthesis largely...

The enhanced thermal stability and reduced hygroscopicity of aluminum hydride coated with Vinyltrimethoxysilane

Alpha-aluminum hydride (α-AlH3) is an excellent high-energy additive for solid propellants because of its high hydrogen content (10.8 wt%) and energy density, low decomposition temperature, and good combustion performance. However,...

Thermocatalytic formic acid dehydrogenation: Recent advances and emerging trends

As a state-of-the-art resource for in situ hydrogen supply, formic acid has recently attracted considerable attention due to its advantages of high hydrogen content, low toxicity, and easy storage and...

Evaluation of a Turbulent Jet Flame Flashback Correlation Applied to Annular Flow Configurations with and Without Swirl

The adaptation of high hydrogen content fuels for low emissions gas turbines represents a potential opportunity to reduce the carbon footprint of these devices. The high flame speed of hydrogen air mixtures combined with the small quenching distances poses a challenge for using these fuels in situations where significant premixing is desired. Flashback along the walls (i.e., boundary layer flashback) can be exacerbated with high hydrogen content fuels. In the present work, the ability of a flashback correlation previously developed for round jet flames is evaluated for its ability to predict flashback in an annular flow with and without swirl. Flashback data are obtained for various mixtures of hydrogen and methane and hydrogen and carbon monoxide for all the annular flow configurations. Pressures from 3-8 bar are tested with mixture temperatures up to 750 K. Flashback is induced by slowly increasing the equivalence ratio. The results obtained show that the same form of the correlation developed for round jet flames can be used to correlate flashback behavior for the annular flow case with and without swirl despite the presence of the centerbody. Adjustments to some of the constants in the original model were made to obtain the best fit, but in general, the correlation is quite similar to that developed for the round jet flame. A significant difference with the annular flow configurations is the determination of the appropriate gradient at the wall, which in the present case is determined using a cold flow CFD simulation.

Evaluation of a Turbulent Jet Flame Flashback Correlation Applied to Annular Flow Configurations With and Without Swirl

The adaptation of high hydrogen content fuels for low emissions gas turbines represents a potential opportunity to reduce the carbon footprint of these devices. The high flame speed of hydrogen air mixtures combined with the small quenching distances poses a challenge for using these fuels in situations where significant premixing is desired. In particular flashback in either the core flow or along the walls (i.e., boundary layer flashback) can be exacerbated with high hydrogen content fuels. In the present work, the ability of a flashback correlation previously developed for round jet flames is evaluated for its ability to predict flashback in an annular flow. As a first step, an annular flow is generated with a centerbody located at the centerline of the original round jet flame. Next, various levels of axial swirl is added to that annular flow. Additional flashback data are obtained for various mixtures of hydrogen and methane and hydrogen and carbon monoxide for all-the annular flow configurations. Pressures from 3–8 bar are tested with mixture temperatures up to 750 K. Flashback is induced by slowly increasing the equivalence ratio. The results obtained show that the same form of the correlation developed for round jet flames can be used to correlate flashback behavior for the annular flow case with and without swirl despite the presence of the centerbody. Adjustments to some of the constants in the original model were made to obtain the best fit, but in general, the correlation is quite similar to that developed for the round jet flame. A significant difference with the annular flow configurations is the determination of the appropriate gradient at the wall, which in the present case is determined using a cold flow CFD simulation.

Pt-Ni Nanoalloys for H2 Generation from Hydrous Hydrazine

Hydrous hydrazine (N2H4∙H2O) is a candidate for a hydrogen carrier for storage and transportation due to low material cost, high hydrogen content of 8.0%, and liquid stability at room temperature. Pt and Pt nanoalloy catalysts have been welcomed by researchers for the dehydrogenation of hydrous hydrazine recently. Therefore, in this review, we give a summary of Pt nanoalloy catalysts for the dehydrogenation of hydrous hydrazine and briefly introduce the decomposition mechanism of hydrous hydrazine to prove the design principle of the catalyst. The chemical characteristics of hydrous hydrazine and the mechanism of dehydrogenation reaction are briefly introduced. The catalytic activity of hydrous hydrazine on different supports and the factors affecting the selectivity of hydrogen catalyzed by Ni-Pt are analyzed. It is expected to provide a new way for the development of high-activity catalysts for the dehydrogenation of hydrous hydrazine to produce hydrogen.

Study on Preparation Process and Properties of High Hydrogen Content Concrete for Neutron Shielding

A series of concrete samples with high hydrogen content were prepared by pressing process with aluminum hydroxide, boron carbide and aluminate cement as raw materials. the mechanical performance of the shielding material was examined by flexural strength tester and compression strength tester. Thermogravimetric analyzer was used to test the weight loss performance of the shielding material, hydrated cement and Al(OH)3. The thermal stability of the concrete at working temperature were investigated by bake the samples at 210°C for 90 hours and at 300°C for 5 hours. The shielding performance against neutron from 241Am-Be source were examined by neutron penetration tests. The test results show that the mechanical properties of the shielding material decrease with the increase of the content of aluminum hydroxide, the compression strength of the shielding material reached above 10MPa. The decomposition temperature of conc is 220°C, the weight loss curve tends to be plateau after baking at 210°C for 20 hours. Most of the crystal water lost after holding at 300°C for 5 hours, but the dimensions of the samples show no obvious change. The shielding performance of the material against neutron from 241Am-Be source is comparable to that of lead-boron polyethylene.