A Performance Modeling Study for Zero Fossil CO2 Stack Operation and Solvent Thermal Reclaiming in Post-Combustion Capture Industrial Applications

Abstract

Post-combustion capture (PCC) of CO₂ is widely recognized as the most mature technology to mitigate CO₂ emissions from existing fossil fuel-based power plants and industrial sources, and successful deployment will predominantly rely on the ability of the PCC plant to consistently achieve high capture fractions. To this end, the performance modeling study presented herein is the first attempt to identify engineering options for long-term, cost-effective windows for zero fossil CO₂ stack emission PCC operation, when 100% of the added fuel CO₂ (100% of the fossil CO₂) is captured, in key industrial applications including combined cycle gas turbine (CCGT) power plants, steel, cement, energy from waste (EfW), and oil refining (fluidized catalytic crackers). Furthermore, low-cost designs for effective solvent recovery through thermal reclaiming with effective energy recovery are analyzed for the first time for nonproprietary, open-art aqueous MEA solvent at 35% w/w (unloaded). At 100% capture of the added fuel CO₂, low lean loadings (between 0.1 and 0.12 molCO₂/molMEA) enhance mass transfer in the absorber, while a raised desorber pressure of 2.4 bar limits excessive energy consumption. In fact, for an absorber packing height of 20 m (2 × 10 m beds), the optimum specific reboiler duty (SRD) to capture 100% of the added fuel CO₂ (zero fossil CO₂ stack operation) was found to lie between 3.62 and 3.96 GJ/tCO₂, while for a 3 × 8 m bed absorber, i.e., 24 m, the SRD drops to 3.46–3.75 GJ/tCO₂, both cases well within the range of reported energy penalty for 90–95% capture, which has significantly higher residual CO₂ emissions. Furthermore, we analyzed two strategies of continuously operating a thermal reclaimer, i.e., single-stage and two-stage reclaiming systems (the first operates at stripper pressure while the second one at atmospheric) with effective energy integration and consideration of both volatile and nonvolatile components. Two-stage reclaiming can substantially reduce water addition compared to single-stage reclaiming from 100 to 400% of the reclaimer solvent flow to 0–50%. Yet, there exists a trade-off, namely, the greater the MEA recovery, the greater the uptake of volatile thermal degradation products. For example, in the case of single-stage reclaiming operation, for ∼90% MEA recovery, approximately 35% of the HEEDA is recycled to the PCC, and when MEA recovery increases to ∼95%, the associated HEEDA return reaches ∼52%. Effective integration of thermal reclaiming with the desorber results in a small additional electricity output penalty, i.e., ranging from 0.3 to 1.13% relative to the output with capture but with no reclaiming. However, it should be noted that a solvent management technique is essential to an amine-based PCC as accumulation of degradation products will affect capture efficiency and associated energy costs and eventually will be a showstopper. Overall, the study suggests that industrial applications fitted with PCC can achieve deep decarbonization in a cost-efficient manner with effective solvent degradation remedial strategies and contrary to the consensus that high capture fractions are associated with excessive energy penalties. Hence, the results can provide meaningful information for engineering deployment and policy decision making.