Avoiding explosive gas mixtures in alkaline electrolysis through gas accumulation modelling in gas-liquid separators

Abstract

Integrating alkaline water electrolyzers (AWE) with renewable energy sources encounters challenges due to intermittent power supply, which requires dynamic operation between production, standby, and shutdown modes. Under these conditions, gas impurities in hydrogen and oxygen streams can compromise safety and efficiency. As a result, it is necessary to carefully monitor the various stages of operation to ensure safe and effective functioning.

This study introduces transient mass balance equations for gas-liquid separators in two real systems: an atmospheric and a 16-bar pressurized alkaline system, to track gas accumulation and determine the time to reach the Lower Explosive Limit (LEL). Keys governing parameters such as pressure, temperature, and flow rate are analysed to assess their impact on safety. Results show that lower volumetric flow rate and higher pressure extends safe standby periods, while optimal temperature balances gas solubility and safety thresholds.

These findings highlight a critical safety aspect in industrial-scale AWE operations and provide insights to optimize hydrogen production and reduce losses, contributing to the wider acceptance of renewable energy technologies.