Cost and energy sensitivity analysis of absorber design in CO2 capture with MEA

Abstract

Amine-based CO2 capture processes appear to be the near-term technology for post-combustion CO2 removal from fossil fuel power plants. However, there is no experience with large-scale application of CO2 capture on power plants. A good absorber design is necessary to handle the large volumes of dilute flue gas with high performance, low cost and energy requirement of the plant. In the present work, multi-scale simulations of the absorber were investigated using Aspen RateSep, and a cost estimation model was developed based on mass and energy balances produced by the Aspen Plus simulations, and data from Turton et al. (2012) were applied for cost estimation. Investment costs (CAPEX) and energy requirements of the lean amine circulation pump and absorber blower for variations in the absorber design were compared for two cases: CO2 absorption from a coal-fired power plant, and CO2 absorption from a gas-fired power plant both with a net power output of 400MWe. The flue gas flow rate in the gas-fired power plant case is higher than for the coal-fired power plant, over the same net power output. In the gas-fired power plant case the absorber needs to be designed to process high volumes of flue gas and the pressure drop will often be higher than for a coal-fired power plant due to higher gas velocity. This results in higher capital and operatingcosts. Possible re-design of the absorber is studied and the results show that large electrical energy savings in the feed gas blower can be obtained when a design is chosen giving reduced absorber pressure drop. This can be achieved if the column cross sectional area is increased. This is offset by extra capital cost by a need for slightly more volume of packing. The operational design flexibility in a CO2 capture plant for a gas-fired power plant is higher than for a coal-fired power plant.