Influence of stripper operating parameters on the performance of amine absorption systems for post-combustion carbon capture: Part I. High pressure strippers

Amine absorption is a mature technology that is widely applied on a commercial scale for the removal of acid gases from gas mixtures. It is viewed as the most promising technology to separate carbon dioxide (CO2) at point emission sources such as fossil fuel fired power plants as a part of a strategy called ‘carbon capture and storage’ being deployed to mitigate climate change. However, there are major challenges in advancing its use for this application; the most prominent one being – cost. It is estimated that the application of current technology to CO2 capture will result in a 70–100% increase in the cost of electricity (COE). As a part of this two-part study, we have examined the influence of stripper operating parameters on carbon capture at a 400 MW pulverized coal-fired power plant retrofitted with amine absorption technology. We use the process simulation software, ProMax® to simulate the amine absorption process. Three commercial absorbents namely monoethanolamine (MEA), diethanolamine (DEA) and diglycolamine (DGA) are considered in this work. All the absorbents examined are studied at the typical working concentrations used in commercial operation. We also constrain the CO2 loading of rich amine solution to 0.4 mol-CO2/mol-amine to closely resemble the chemical environment in commercial operation. The main pointer used to compare system performance is the parasitic power loss due to the carbon capture. Parasitic power loss comprises of the loss of plant output due to withdrawal of reboiler steam from the low pressure turbine; the electricity required for CO2 compression and by the plant auxiliaries such as blowers and pumps. We also examine the absorber and stripper column sizes and heat exchanger parameters which are key components of the system. On the basis of our findings in the first part of this study, we report that operating the stripper at higher pressures has significant advantages but also some disadvantages and operational challenges. We also report that DEA and DGA have a superior performance to MEA when used in high pressure strippers. We conclude that increasing the stripper pressure reduces the parasitic losses and the equipment sizing but may result in higher solvent losses and equipment corrosion.

► We model the amine absorption process with high pressure strippers using process simulation software – ProMax®.
► We study stripper performance at pressures between 150 kPa and 300 kPa. MEA, DEA and DGA have been studied.
► Important constraints used are at least 90% CO2 capture and a maximum rich amine loading of 0.4 mol-CO2/mol-amine.
► Parameters compared are the reboiler duty, equipment size, corrosion and absorbent losses.
► We find that the reboiler duty reduces with an increase in the stripper operating pressure.