Ken Brookes reviews the PowderMet2015 paper ‘Hydroprime gas generators provide low cost, reliable hydrogen for powder metallurgy.’

Anyone who works in the powder metallurgy industry (as I learnt years ago from my own experience in hardmetals manufacture) knows the importance of pure hydrogen as a protective atmosphere and a potent reactant, not least in reducing oxides. Sometimes allied with nitrogen and other gases, hydrogen atmospheres are employed in a variety of key processes, such as powder production, lubricant removal, sintering and heat treatment.

Like many others 50 and more years ago, we produced pure hydrogen by electrolyzing pure distilled water and then drying the resultant hydrogen gas. In San Diego at the recent PowderMet2015 conference, Goutam Shahani of the Linde Group presented a paper, ‘Hydroprime gas generators provide low cost, reliable hydrogen for powder metallurgy,’ describing the company's very different proprietary process for the same product. This system is claimed to have demonstrated excellent results in commercial production worldwide.

In this review I employ the units used in the original paper, rather than converted into SI units. This is because the industry, especially in the United States, appears to have adopted certain units which resist such conversions, for example ‘Nm3/h’, which appears to use SI nomenclature but does not, because in this case ‘N’ means ‘normal’ and not ‘newtons.’ The industry knows its own shorthand, which is not too difficult to understand, so I’ve left it alone.
Atmospheres

As explained by the author, hydrogen atmospheres are used in the sintering and annealing of PM parts to enhance their physical and chemical properties, as shown in Fig. 1 (clearly based on ferrous PM). Relatively small volumes of hydrogen <1.0955 Nm3/h (1 MMSCFD) are supplied in bulk by trailer or produced on-site by electrolysis, methanol and ammonia dissociation or by steam methane reforming. While steam methane reforming was the dominant method of producing hydrogen at a relatively large scale, >1.0995 Nm3/h (1 MMSCFD), this technology (the subject of the paper) had not yet been widely adopted at a small scale, due to cost and reliability considerations.

This article appeared in the July/August issue of Metal Powder Report.

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