Principles and practical measurement and control strategies for achieving ultrahigh CO2 capture rates in amine post-combustion capture plants

This study presents a practical feedback control strategy for conventional amine post-combustion capture (PCC) plants that is capable of achieving up to around 100% added CO2 capture (i.e., the exit CO2 is equivalent to the CO2 in the combustion air) with moderate energy inputs. It has been demonstrated using MEA, but the fundamental principles appear to be more widely applicable. The method involves controlling the desorber to produce the lowest possible lean loading without excessive energy input using simple temperature measurements and then closely regulating the liquid-to-gas ratio in the absorber so that the minimum amount of solvent required to achieve the target capture rate is used. The principles behind the control method are illustrated using process modeling, and its practical viability is shown by a successful 75 h continuous period of controlled ∼100% capture in pilot testing at 30 tCO2/day scale. Implementation was found to require only minimal operator training and was able to be accomplished using standard plant instrumentation supplemented by a flue gas analyzer suitable for the resulting ∼500 ppmv exit CO2 levels. The control approach therefore appears transferable to commercial amine capture facilities, although maximum achievable capture rates will depend on a plant’s physical design. This paper provides actionable insights for plant design, particularly key instrumentation provisions, and supports permitting guidelines for regulators.