Experimental Evaluation of Innovative Catalytic Heat Exchangers for Energy-efficient Amine-based Post-combustion CO₂ Capture Processes

Abstract

This PhD research focused on enhancing CO2 desorption performance in post-combustion carbon capture processes by developing and optimizing catalytic heat exchangers. The guiding principle was to address challenges, including operational complexity and high energy consumption, while minimizing costly modifications to existing piping and infrastructure in pilot plants. The feasibility of novel aqueous piperazine-based biphasic solvents was initially investigated to reduce solvent flow rates and optimize heat exchanger size. Although these solvents demonstrated promising absorption and desorption performance, challenges such as high viscosities, suboptimal phase split ratios and low amine concentrations in the rich phase limited their applicability in the catalytic heat exchanger system. An innovative agitated jacket vessel with a coil heat exchanger (JVC-EX) was developed and experimentally validated. Compared to the conventional fixed catalyst bed desorber, the JVC-EX using benchmark MEA solvent and solid acid catalyst HZSM-5 achieved approximately 30% catalytic enhancement, a 50% reduction in catalyst demand, and a 22% decrease in energy consumption while maintaining excellent operational stability and flexibility. However, concerns emerged regarding catalyst durability due to mechanical stirrer-induced attrition, highlighting the need for further mechanical optimization. To address this limitation, a spouted bed and jet-flow catalytic heat exchanger (SBJ-EX) was introduced as a non-agitated alternative. The SBJ-EX demonstrated a 70% improvement in heat transfer efficiency compared to traditional plate heat exchangers and delivered excellent CO2 desorption performance at lower operating temperatures. Its spouted design effectively minimized catalyst attrition, ensured system stability, and enabled faster catalyst replacement, significantly reducing maintenance downtime. Both catalytic heat exchangers showed strong adaptability for integrating existing and new industrial-scale carbon capture systems. Overall, this thesis provided valuable insights into the design, operation, and optimization of novel catalytic heat exchangers, emphasizing their potential to drive the adoption of catalysts in commercial-scale carbon capture applications.