ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Determining the proper gas purging rate under different scenarios: an example from lab-scale benzene hydrogenation

Kang Chen and Jing Shi

Huafon Shanghai Advanced Materials Research Institute, Shanghai, China

E-mail: tjck6@163.com

Received: 5 September 2025  Accepted: 16 October 2025

Abstract:

Laboratory fires and explosions pose a serious risk to research and development facilities worldwide, threatening significant harm to people, property, and the environment. While gas purging has been widely acknowledged as an effective method of risk control, proper determination of the purging rate under various conditions is not well translated to the process safety community, possibly due to the lack of pertinent comprehensive analysis or insufficient safety awareness. The work reported in this paper aimed to determine the proper purging rate in different scenarios during lab-scale benzene hydrogenation through a combination of field experiments and theoretical calculations. The appropriate gas purging rates before, during, and after the reaction for the purpose of purging into and out of service are determined to be 1.78, 2.20, and 2.21 m³/hr, respectively. Further, the purging rate before the reaction is optimized to be 0.13 m³/hr based on the Froude number equation, representing a significant reduction in nitrogen gas consumption. Notably, the experimental oxygen concentration within five seconds of purging experienced a slower decline compared to theoretical values, which might be explained by the incomplete mixing initially. A holistic understanding of the proper gas purging rate not only reduces the process safety risk but also ensures the required reaction environment. While this study was performed based on the benzene hydrogenation process, the methodology presented can contribute to some reference value for process safety professionals to determine the proper gas purging rate in other chemical reaction processes.

Keywords: Purging rate; Benzene hydrogenation; Process safety; Fire and explosion; Oxygen concentration

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-025-04464-z

Chemical Papers 80 (2) 1483–1490 (2026)