Investigating the explosion hazard of hydrogen produced by activated aluminum in a modified Hartmann tube

• Published in: International journal of hydrogen energy Vol. 47; no. 35; pp. 15933 - 15941
• Main Authors: Cai, Jingzhi, Liang, Yuntao, Jia, Rongtian, Amyotte, Paul, Chen, Yangyang, Yuan, Chunmiao
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 26.04.2022
• Subjects: Aluminum-water reaction; Flame propagation mechanism; Hartmann tube; Hydrogen fire; Hydrogen fire; Hartmann tube; Flame propagation mechanism; Aluminum-water reaction
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2022.03.070

Metallic powders exposed to water are sources of hydrogen gas that may result in an explosion hazard in the process industries. In this paper, hydrogen production and flame propagation in a modified Hartmann tube were investigated using activated aluminum powder as fuel. A self-sustained reaction of activated aluminum with water was observed at cool water and room temperatures for all treatments. One gram of Al mixed with 5 wt% NaOH or CaO resulted in a rapid rate of hydrogen production and an almost 100% yield of hydrogen generation within 30 min. The flame structures and propagation velocity (FPV) of released hydrogen at different ignition delay times were determined using electric spark ignition. Flame structures of hydrogen were mainly dependent on hydrogen concentration and ignition delay time, likely due to different mechanisms of hydrogen generation and flame propagation. As expected, FPVs of hydrogen in the Hartmann tube increased with ignition delay time. However, the FPV of upward flame propagation was much larger than that of downward flame propagation due to the effect of spreading acceleration at the explosion vent. Once ignited, the FPV of upward flame propagation reached 31.3–162.5 m/s, a value far larger than the 7.5–30 m/s for downward flame propagation. Hydrogen explosion caused by the accumulation of wet metal dust can be far more dangerous than an ordinary hydrogen explosion. [Display omitted] •Hydrogen generation was driven by the type and mass ratio of activators.•Flame structure and propagation velocity of hydrogen varied with ignition delay time.•Multi-explosion phenomenon contributed to longer burning time and higher explosion hazard.•The presence of hydrogen could enhance explosion hazard of wet metal dust.