(801a) Thermodynamic Analysis of Amine Solvents for CO2 Scrubbing

Evaluation of amine solvents for CO₂ scrubbing is difficult because superior performance is a complex combination of solvent characteristics (e.g., absorption capacity, heat of absorption, mass transfer and kinetics, hydraulic properties) and process innovations (e.g., absorber intercooling, lean-vapor compression, interheated strippers).  In this work we tackle an important subset of the problem that is amenable to immediate objective analysis, i.e, what does solution thermodynamics teach us about relative solvent performance?  We approach the problem by systematically creating solvents for which the only restriction is thermodynamic consistency, and then performing a relative evaluation using process simulation in a standard flowsheet.  The study provides useful insight into the interplay between absorption capacity and enthalpy of solution.  Our conclusion is that an optimum solvent is one that has mid-range enthalpy of solution and a CO₂ capacity that is just right (not to small and not too large) for the particular enthalpy of solution. 

Of course, commercially successful solvents require other positive characteristics, like fast mass transfer and kinetics, low viscosity, high stability, and low toxicity.  Comprehensive evaluation of new CO₂-capture solvents is necessary, but our study offers an important first step.