(7d) Electrochemically-Mediated Amine Regeneration for Carbon Dioxide Scrubbing Processes

Electrochemical-mediated amine regeneration (EMAR) is an alternative strategy for facilitating CO₂ desorption and regeneration of loaded amine solutions exiting the absorber in CO₂ scrubbing processes.  The traditional methods used is either a thermal-swing regeneration or pressure-swing regeneration.  The strong affinity for amine molecules to form aqueous complexes with cupric ions is exploited in the EMAR process to release the CO₂ from the amines isothermally through competitive binding.  Electrochemical systems offer several advantages over thermal systems including significantly lower lean loadings, less required internal reconfiguration of the turbine systems, and more flexible operation that allows power to be redirected back to the grid in the event of a spike in energy demand.

Development of an efficient EMAR process requires both investigation into the chemistry and system design to address the thermodynamic, kinetic, and transport phenomena.  Selection of the correct amine molecule to achieve desirable thermodynamic and kinetics properties requires careful consideration of the CO₂ reaction equilibrium and the stability constant of the copper complex formation. While strong copper binding is required to elicit the release of the CO₂, amines that complex too strongly to the cupric ions will greatly hinder the electrochemical kinetics of the amine/copper reactions.  The kinetics of these reactions in the presence of CO₂, which have not been previously investigated, will be discussed.

A variety of voltammetric techniques will be used to assess the electrochemical kinetics for several different amine species in the presence and absence of CO­₂.  We will compare results from small-scale operation in a 5 mL three electrode setup to a bench scale system capable of running at several amperes.  The results will be used to show the feasibility of large scale systems through kinetic models.