Characterization of Hydrogen-in-Oxygen Changes in Alkaline Electrolysis Hydrogen Production System and Analysis of Influencing Factors

Industrial alkaline water electrolysis systems face challenges in maintaining hydrogen-in-oxygen impurity within safe limits under fluctuating operating conditions. This study aims to characterize the dynamic response of hydrogen-in-oxygen concentration in an industrial 10 kW alkaline water electrolysis test platform (2 Nm3/h hydrogen output at 1.6 MPa and 90 °C) and to identify how operating parameters influence hydrogen-in-oxygen behavior. We systematically varied the cell current, system pressure, and electrolyte flow rate while monitoring real-time hydrogen-in-oxygen levels. The results show that hydrogen-in-oxygen exhibits significant inertia and delay: during startup, hydrogen-in-oxygen remained below the 2% safety threshold and stabilized at 0.9% at full load, whereas a step decrease to 60% load caused hydrogen-in-oxygen to rise to 1.6%. Furthermore, reducing the pressure from 1.4 to 1.0 MPa lowered the hydrogen-in-oxygen concentration by up to 15%, and halving the alkaline flow rate suppressed hydrogen-in-oxygen by over 20% compared to constant conditions. These findings provide new quantitative insights into hydrogen-in-oxygen dynamics and offer a basis for optimizing control strategies to keep gas purity within safe limits in industrial-scale alkaline water electrolysis systems.