CHAPTER 5: System and Processes of Pre-combustion Carbon Dioxide Capture and Separation

In this chapter, the development of H₂/CO₂ separation technology, including a new CO₂ chemical adsorbent, a pressure swing adsorption (PSA) reactor model, and the continuous operation of a pilot-scale test system for pre-combustion CO₂ capture, are presented. Potassium-promoted Mg–Al layered double oxides (LDOs) are shown to be appropriate candidate adsorbents for elevated temperature (250–450 °C) PSA for pre-combustion H₂/CO₂ separation. The adsorption heat of CO₂ on the surface of LDOs is only 2.5–60.4 kJ mol⁻¹, which is beneficial for achieving isothermal desorption by a pressure swing. Further, methods for enhancing the CO₂ capacity and the mechanical strength of adsorbent pellets are introduced. The single- and double-column fixed-bed experiments provided useful results for the development and validation of scalable modeling. The PSA model was built by coupling a non-equilibrium kinetic adsorption model and a column model. The effects of operating parameters on the H₂ recovery ratio and CO₂ capture ratio were studied. A 4-column pilot-scale elevated temperature PSA (ET-PSA) system was developed with a processing capacity of 4.0–6.6 Nm³ h⁻¹ to determine the feasibility of such a system for industrial application. It achieved 1089 h of accumulated operation and 75 h of continuous operation, maintaining a CO₂ removal ratio higher than 91.7%.