Hydrogen Reduction

The evolution of surface morphologies and microstructures during cold rolling after hydrogen reduction

Chapter 27 - Hydrogen Reduction of Nickel from Ammoniacal Sulfate Solutions

The removal of oxide scale from a hot-rolled strip surface can completely eliminate environmental pollution if performed by hydrogen-reduction descaling instead of traditional pickling descaling. However, a large number of cracks appear on the surface of a leveled hot-rolled steel strip after hydrogen reduction. This effect is likely to impede the application of reduction descaling to cold-rolled products. Nevertheless, there are almost no cracks on the surface of an unleveled hot-rolled steel strip if the hot-rolled steel strip is not subjected to repeated bending by the leveler machine. The surface quality of a reduced steel strip will be better than that of a pickled steel strip. To investigate the evolution of the surface morphologies, microstructures, and properties of an unleveled strip steel during cold rolling, unleveled strip steel samples were rolled using a four-high mill after hydrogen reduction and after pickling. The surface morphologies and cross-sectional microstructures of the samples were observed by SEM, and the surface-roughness values were measured using a TR200 profilometer before and after cold-rolling deformation. The evolution of the surface morphologies and cross-sectional microstructures of the sample after cold rolling were analyzed. The results show that the oxide scale formed on the surface turns into a metallic iron layer, and a decarburization layer appears between the metallic iron layer and the steel matrix after hydrogen reduction. Few cracks, besides pores, and bubbles, appeared on the surface of the sample after hydrogen reduction. The pores and bubbles were roll-flattened after five passes of cold rolling. The work hardening degree and mechanical properties of the reduced sample are similar to those of the pickled sample after cold rolling. Compared with the rolled sample after pickling, the surface qualities of the reduced samples are better than those of the pickled samples and better than those of the reduced samples that were subjected to leveling prior to reduction.

This study investigates the non-static hydrogen reduction characteristics of various iron ore fines under HyREX reduction conditions to assess the raw material flexibility of a hydrogen-based fluidized bed reduction process. The research focuses on comparing the reduction and disintegration behaviors between hematite ore and goethite-containing ores. Results indicate that hematite ore exhibits greater disintegration during non-static hydrogen reduction, which can be attributed to its mineralogical characteristics and higher total iron content. By kinetic analysis of the reduction curve, it was found that the overall hydrogen reduction can be divided into three separate stages. In the second stage, where most of the reduction occurs, the hydrogen reduction rate is primarily governed by interfacial chemical reactions, with minimal impact from diffusion enhancements due to goethite decomposition. In all the ores tested, the reduction rate decreased sharply in the final stage because the overall reaction was primarily governed by slow solid-state diffusion. Additionally, the final reduction degree strongly depends on the ultrafine particles generated by disintegration during reduction. The final reduction degree of all iron ores used in this study exceeds 90 pct, highlighting the high raw material flexibility of the HyREX process. This flexibility supports the potential for ore blending strategies to balance performance and cost-effectiveness, offering valuable insights for optimizing industrial hydrogen reduction processes.

Noble-metal electrocatalysts supported by biological-organism-derived carbons have attracted attention from the public due to the growing demands for green synthesis and environmental protection. Carbonization at high temperatures and hydrogen reduction are critical steps in this technical route. Herein, Shewanella oneidensis MR-1 were used as precursors, and the effects of the hydrogen-reduction procedure on catalysts were explored. The results showed that the performances of FHTG (carbonization followed by hydrogen reduction) displayed the best performance. Its ECSA (electrochemical surface area), MA (mass activity), and SA (specific activity) reached 35.01 m2 g−1, 58.39 A·g−1, and 1.66 A cm−2, respectively, which were 1.17, 1.75, and 1.50 times that of PHTG (prepared through hydrogen reduction followed by carbonization) and 1.56, 2.26, and 1.44 times that of DHTG (double hydrogen reduction). The high performance could be attributed to its fine particle size and rich N content, and the specific regulation mechanism was also proposed in this paper. This study opens a practical guide for effectively avoiding particle agglomeration during the fabrication process for catalysts.

Preparation ultrafine WC based on the new tungsten metallurgy system of “no ammonia transformation - no hydrogen reduction”

Glasses containing lead, bismuth, or antimony oxides or combinations of these become conducting after several hours’ reduction in hydrogen. The electronic surface conductivity is both stable and reproducible. The magnitude of the conductivity depends on the nature and amounts of the reducible oxides, the temperatures at which reduction is carried out, and the electrical influence of the nonreduced portions of the glasses.

Interparticle hydrogen migration on PdAl 2O 3 catalysts for benzene hydrogenation?

Mechanical properties of tape cast nickel-based anode materials for solid oxide fuel cells before and after reduction in hydrogen

CeO2 modified Fe2O3 for the chemical hydrogen storage and production via cyclic water splitting

Kinetics of thermal decomposition and hydrogen reduction of Cobalt compounds: A review

Catalytic performance of a high-cell-density Ni honeycomb catalyst for methane steam reforming

Hydrogen dielectric-barrier discharge (H2-DBD) plasma was successfully used to prepare carbon nanotubes (CNTs)-supported cobalt (Co) catalyst. The H2-DBD plasma treatment simultaneously decomposed and reduced the cobalt precursor at a lower temperature and in a shorter time than the conventional method (calcination and hydrogen reduction). It is considered that the H2-DBD plasma method can remarkably decrease the amount of energy input compared to traditional methods used to prepare the Co-based catalyst in Fischer–Tropsch synthesis (FTS). Results showed that the Co catalyst prepared by H2-DBD plasma had an equivalent catalytic performance for FTS as that prepared using the conventional method in calcination and hydrogen reduction, thereby determining that H2-DBD plasma was an effective alternative treatment for preparing the Co/CNTs catalyst for FTS. This technology will provide a new strategy for preparing catalysts in other catalysis processes.

Microstructure and properties of La2O3-doped tungsten-based bulk material and its densification mechanism during spark plasma sintering process

Investigation on morphology evolution of coarse grained WC–6Co cemented carbides fabricated by ball milling route and hydrogen reduction route