Hydrodynamic analogy approach for modelling reactive absorption

• Hydrodynamic analogy approach adequately describes reactive absorption processes.
• Different classes of reactions typical for absorption systems were studied.
• Both laminar and turbulent gas flow conditions were governed.
• Columns filled with different structured packings were successfully modelled.

Design of separation units for reactive gas–liquid systems is usually based on conventional modelling methods employing the stage concept, either equilibrium or rate-based. The parameters of such models (e.g., mass transfer coefficients) are determined experimentally, and, most often, significant experimental effort is necessary when new processes are explored or new types of column internals are developed. In the context of a novel approach based on hydrodynamic analogies, rigorous partial differential transport equations are applied for modelling of non-reactive and reactive separation processes in columns filled with structured packings. The approach has already been verified for distillation and reactive desorption processes. In this work, its application to reactive absorption – also known as chemical absorption – is examined. Different types of reactions appearing in a wide range of absorption systems are considered. To account for absorption processes operated at high gas and liquid loads, an adjustment of the turbulent gas flow description is performed. Therefore, different test systems are used, namely physical absorption of ammonia into water, chemical absorption of sulphur dioxide and chemical absorption of carbon dioxide into sodium hydroxide solutions. The absorption of ammonia and sulphur dioxide took place under turbulent gas flow conditions, while in the absorption of carbon dioxide, the gas flow was laminar. Based on the carbon dioxide system, different types of corrugated sheet packings were compared. The hydrodynamic analogy model was successfully validated using available experimental data.