Title : Process intensification: New perspectives for Chemical Engineering
Abstract:
The European Union, through the SET-Plan, aims to reduce greenhouse gas emissions by 20%, to have a 20% share of energy from low-carbon energy sources and to have a 20% reduction in the use of primary energy by improving energy efficiency by 2020, with a long-term ambition to reduce emissions by 80-95% by 2050. In particular EU suggested that in the future energy system, H2 should be produced from renewable feedstock using renewable energy in order to be considered “zero CO2”, so resulting in a practically closed carbon cycle with no impact (in terms of anthropogenic emissions) to the environment. In this way, a process intensification is mandatory. The approach to process intensification regards process-intensifying equipment, characterized by designs that optimize mass, heat, and momentum transfer (e.g. monolithic catalysts) and process-intensifying methods, involving the application of alternative energy sources, so leading to compact, safe, energy-efficient, and environment-friendly sustainable processes. In particular, the use of structured catalysts with high thermal conductivity, could overcome the heat transfer limitations that occur in both endothermic and exothermic reactions. For example, in the case of Methane Steam Reforming (MSR) reaction, the limiting step is the heat transfer towards the reaction volume, since its high endothermicity requires high heat fluxes, so resulting in complex reactor geometries and very high temperatures of heating medium. Therefore, very expensive construction materials, very high reaction volumes and very slow thermal transients are present. The structured catalysts could allow achieving a very uniform temperature profile, resulting in a more effective and selective exploiting of catalyst surface, minimizing the catalyst mass, making the system more attractive in terms of cost and compactness. Furthermore, the appropriate catalyst carrier selection is a key point for the equilibrium-limited exothermic reaction, such as Water gas Shift (WGS). A flattened temperature profile, i.e. higher inlet temperature and lower outlet temperature, may be realized enhancing the heat backdiffusion in the solid structure of a high conductive catalyst carrier, so allowing higher reaction rates at the inlet sections and higher CO conversion at the outlet section, minimizing the overall reaction volume.
