The most dominant energy source is fossil fuels, such as coal-fired and combined-cycle
gas turbine (CCGT) power plants. However, it has a significant negative impact on the
environment due to the massive amount of CO2 emissions released from these sources.
To combat this issue, researchers identified the most mature technology known as carbon
capture, utilisation, and storage (CCUS). The solvent-based post-combustion CO2
capture process (PCC) is the most commonly used among other approaches. This
approach is deployed using solvents such as monoethanolamine (MEA), which is the
most widely used viable solvent in chemical absorption. However, this solvent has a
negative impact on energy consumption. Thereby, the researchers investigated other
solvents such as single solvents (e.g., piperazine (PZ) and 2-amino-2-methyl1-propanol
(AMP)). Also, mixed solvents such as a blend of PZ and AMP.
In this study, a steady-state rate-based PCC process model was developed using MEA,
PZ, and mixed solvents (PZ with AMP). At the pilot scale, the three models were validated
against experimental data using Aspen Plus®. The results of the model validation
confirmed that the rate-based model for the three solvents predicted the experimental
data with a lower than 10% deviation. When scaled up to a 250 MWe combined-cycle gas
turbine power plant (CCGT), the packed column size for MEA solvent has the highest
diameter and height, followed by PZ solvent and mixed solvents.
Sensitivity analysis and technical evaluation were performed to obtain the optimal CO2
lean loading, which affects the liquid to gas ratio (L/G ratio) and specific re-boiler duty.
Based on the L/G ratio, the values were 1.49 kg/kg, 0.76 kg/kg, and 1.55 kg/kg for MEA,
PZ, and mixed solvents (PZ with AMP), respectively. On the other hand, specific re-boiler
duties were 4.14 GJ/tonne CO2, 3.92 GJ/tonne CO2, and 2.95 kg/kg for MEA, PZ, and
mixed solvents (PZ with AMP). Furthermore, economic evaluations were assessed for the
three models at different solvents. The economic findings show that the lowest total
annualised cost per tonne CO2 was estimated in the case of 40 %wt. PZ, which equals
21£ per tonne CO2.
Control structure and design dynamics demonstrate that the performance of PZ was faster
in terms of reaching the steady-state when compared to other solvents.
