Sensitivity of amine-based CO2 capture cost: The influences of CO2 concentration in flue gas and utility cost fluctuations

Abstract

The amine-based absorption process is the preferred technique to capture CO2 from flue gas. However, the cost of CO2 capture using an amine-based absorption process is considered high due to the solvent regeneration step. Therefore, in order to make this process a viable option for CO2 capture, its cost, especially its operating cost, must be reduced. This paper presents the results of a systematic sensitivity analysis, which covers the effects of CO2 concentration in flue gas and utility cost fluctuations on the optimum amine-based CO2 capture cost. The paper aims to determine whether the operating conditions of an existing CO2 capture plant can be changed to offset the effects of CO2 concentration in flue gas and utility cost fluctuations in order to yield the same or lower CO2 capture cost as the original plant design. It also provides an understanding of how the optimum CO2 capture cost changes with these fluctuations. The considered utility costs are the prices of amine solvent(s), electricity, process water, cooling water, and low pressure saturated steam. The response surface technique, coupled with the steepest descent method, is utilized to search for the direction of lower CO2 capture cost. The final result obtained from this methodology consists of the optimum operating conditions of the process with the minimum CO2 capture cost. The studied solvents are monoethanolamine (MEA) and diglycolamine (DGA), and diethanolamine–triethanolamine mixture (DEA–TEA). The results show that changes in the CO2 concentration in flue gas have the highest impact on the optimum CO2 capture cost of an existing plant when compared with the remaining parameters. For all solvents, the optimum CO2 capture cost shows an inversely proportional relationship to the CO2 concentration in flue gas. The optimum cost decreases by around 29–33% as the CO2 concentration increases by 50%, and the cost increases by around 86–104% as the CO2 concentration decreases by 50% when compared to the base case. The fluctuations in the utility costs do not exhibit a significant impact on the minimum CO2 capture cost.