Assessment of process modifications for amine-based post-combustion carbon capture processes

Abstract

This study aims to provide a comprehensive comparison of different configurations of amine-based Post-combustion carbon capture (PCC) using Mono-Ethanol Amine and activated Methyl Di-Ethanol Amine (MEA and a-MDEA) solvents. A base case simulation model of a process with MEA is developed and validated at two capture rates, of 20 and 2000 tonnes per day, with the data reported in a study prepared by Nexant. The model was then used for a 1900 tonnes-per-day capture facility, and several combinations of substantial process modifications, including absorber intercooling (AIC), lean vapor recompression (LVR), and parallel exchanger arrangement (PEA) are investigated. Various scenarios for the two amine-based solvents are simulated in Aspen HYSYS®, and the results are compared with a base case conventional process for the same solvent. Results from the studied scenarios showed that a-MDEA with AIC-LVR modifications is a more attractive option due to an 8% reduction in stripper reboiler energy and its associated steam costs. The analysis of the studied cases showed that the effect of solvent on energy saving is more important than that of process modification, with the combined effect of both modification and solvent bringing higher benefits. It is also concluded that a complex process such as PCC with AIC-LVR-PEA modifications has the highest energy savings although it is less cost-effective. While OPEX (Operating Expenditure) values (mainly associated with utility steam and cooling water consumption) are still considerable, we ended up with CAPEX-intensive (Capital Expenditure) capture plants. For typical PCC equipped with combined AIC and LVR modifications (total capital investments of $136 million and $147 million were estimated for MEA and a-MDEA, respectively, translating to capture costs of US$58.80 and US$53.80 per tonne of CO2 captured. Potential savings of approximately 4–15% (for MEA) and 3–12% (for a-MDEA) were calculated depending on the scenario of combined process modifications among a shortlist of attractive options. These energy reductions portray promising reductions in the energy consumption imposed by an amine absorption-based PCC technology.