Ionic Liquid as a Selective Capture Method of CO₂ from Different Sources: Comparison with MEA

Abstract

Ionic liquids (ILs) have received growing consideration as a prospective decarbonization solvent. Nevertheless, most studies have focused on flue gases with specific compositions and flow rates, which makes it a challenging task to use ILs with divergent CO 2 emission scenarios for the comprehensive carbon management. In this work, complete conceptual designs for absorption processes 1-butyl-3methylimidazolium acetate ([bmim][Ac]) are developed for separating at least 90% of CO 2 from the feed before pressurizing it to 150 bar to the sequestration sites over a broad range of CO 2 flue gas compositions and flow rates. Each scenario is rigorously modeled, simulated, optimized, heat integrated, and compared with the conventional process by MEA. The simulation results show that compared to conventional processes, IL-based processes are only quite economical at high flue gas flow rates and CO 2 contents. Also, a quantitative method toward technology comparison and scaling up is presented, which helps in selecting the suitable technology when input conditions change. Finally, a cost model for investment and operating costs of various emission sources is proposed as a tool to design an energy-saving and cost-efficient CO 2 supply chain network for the future.

Surface-Response Analysis for the Optimization of a Carbon Dioxide Absorption Process Using [hmim][Tf2N]

“…The obtained values are comparable with other studies. Significant carbon dioxide reductions were also obtained in the work of Nguyen and Zondervan [40] and de Riva et al [39]. Capital and operating costs were not suggested for the [ 6 ], economic data can be found and suggested [9,36], but a straight comparison cannot be made with the used ionic liquid.…”

“…Capital and operating costs were not suggested for the [ 6 ], economic data can be found and suggested [9,36], but a straight comparison cannot be made with the used ionic liquid. However, from a first analysis it is possible to consider the relations proposed by Nguyen and Zondervan [40] for OPEX and CAPEX of [bmim][Ac] as a function of flue gas flow rate and carbon dioxide composition. A comparison between this work and the suggested relations of Nguyen and Zondervan [40] shows that CAPEX values are comparable, while a higher OPEX is calculated due to the required flow rate and cost of the used IL.…”

“…The considered column is a packed bed absorber, filled with plastic pall rings with a dimension of 50 mm, a packing surface area of 110 m 2 /cm 3 and 10 stages with a dimension of 3 m, then the total height of the column is 30 m. The void fraction is 0.93. The packed column diameter is 5.5 m and is chosen to avoid flooding inside the column: it operates at 70% of the critical flooding conditions [40]. The shifted flue gas enters from the bottom of the column, while the ionic liquid enters from the top, with a flow rate of 260 kg/s, counter-currently.…”

“…The operating costs instead include the total costs of raw materials, utilities, operating labor, maintenance, operating charges, plant overhead and general and administrative expenses. Regarding the utilities, the costs of steam, cooling water, electricity and ionic liquid are, respectively, 8.93 €/GJ, 0.32 €/GJ, 0.15 €/kWh and 18.16 €/kg [40].…”

“…In another work, Ma et al [17] compared a capture process using [bmim][Tf 2 N] with one using MEA solution: the first case made it possible to save 30.01% of energy consumption and 29.99% of primary costs. Nguyen and Zondervan [40] compared the system capturing carbon dioxide from flue gas using MEA with one using [bmim][Ac], finding that the first was economically preferable at high flue gas flow rates and carbon dioxide contents. Additionally, better conditions for an IL compared to an MEA solution were present when the partial pressure of carbon dioxide was low, such as in a post-combustion flue gas.…”