Analysis of reboiler heat duty in MEA process for CO2 capture using equilibrium-staged model

Abstract

There are several technology options for energy sectors that could reduce the amount of CO2 emissions. At present amine-based absorption processes are most promising as CO2 capture technologies. However amine-based CO2 capture technologies are energy intensive and high in cost. There is continuous research and development for more effective solvents for CO2 capture focusing mainly on lower heat requirement for regeneration. Although many studies for solvent development usually focus on solvents with low reaction heat, the regeneration heat of a solvent is interpreted approximately into three heat components (heat of reaction, sensible heat, and heat of vaporization). The heat energy for the regeneration process is usually supplied from the reboiler in the form of steam and the distribution of the heat energy to the three components depends on the key process parameters such as circulation rate and steam supply rate. In this study the overall performance of the MEA process in terms of CO2 removal efficiency is examined at various process parameters through experimental work. There are negligible degradation and corrosion problems exhibited. Based on the results the distribution of regeneration heat is analyzed, in terms of the three heat components using an equilibrium-staged model. The model reaction process between CO2 with MEA solvent in the CO2 capture system was addressed based on CO2–H2O–MEA equilibrium. However for simplicity, the vapor–liquid equilibrium of H2O–MEA system and the vapor–liquid equilibrium of CO2–MEA are considered separately and then the two systems are coupled assuming they come into existence simultaneously. It is shown that focusing only on the heat of reaction which is an inherent property of a solvent is not sufficient to reduce the reboiler heat duty and that the sensible heat and the heat of vaporization must be taken into consideration to reduce the reboiler heat duty as they are strongly affected by operational parameters.