Identification of accident scenarios caused by internal factors using HAZOP to assess an organic hydride hydrogen refueling station involving methylcyclohexane

• Published in: Journal of loss prevention in the process industries Vol. 71; p. 104479
• Main Authors: Suzuki, Tomoya, Izato, Yu-ichiro, Miyake, Atsumi
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.07.2021
• Subjects: HAZOP; Hydrogen refueling station; Organic hydride; Scenario identification; Hydrogen refueling station; Scenario identification; Organic hydride; HAZOP
• ISSN: 0950-4230
• DOI: 10.1016/j.jlp.2021.104479

Organic hydride hydrogen refueling stations have been remarked as stations that can employ a practicable method based on the organic chemical hydride system involving methylcyclohexane (MCH) for the transport of hydrogen. This station has advantages in that the storage and transportation of MCH does not require a large amount of energy compared to compressed and liquefied hydrogen, and the system can use existing infrastructure. This type of station involves some hazardous materials, and thus, scenario identifications and risk assessments have been performed by researchers. However, the sample of studies available have employed a conceptual design model, and they did not identify concrete scenarios triggered by internal factors. Therefore, the purpose of this study is to identify accidental scenarios caused by internal factors that can affect an organic hydride hydrogen refueling station. In this study, we used Hazard and Operability study (HAZOP) and examined safety measures for the scenarios. As a result of the HAZOP, 105 accidental scenarios were identified and classified into the two following groups; (i) the scenarios assumed that the substances were ignited after they were released to the atmosphere, and (ii) the scenarios assumed that the substances were ignited in the process before they were released. Significant scenarios in group (i) were MCH or toluene pool fires, hydrogen jet fires, vapor gas explosions, or flash fires. The significant scenarios classified in (ii) were newly identified in this study. The scenarios include the explosion of the explosive mixture formed by the gaseous phase of toluene and oxygen from the vent line connected to the tank due to the static electric charge in the tank. For each scenario, safety measures to prevent the progression of the accident scenario were examined with reference to the current laws and regulations in Japan. •Accident scenario identification was carried out for an organic hydride hydrogen refueling station.•105 accident scenarios were identified by using HAZOP.•The significant scenarios assumed that the substances were ignited in the process before they were released were newly identified.•Explosion of flammable mixture in the toluene tank can occur due to the decrease of minimum ignition energy by hydrogen.