Development of a Conceptual Process for Selective CO₂ Capture from Fuel Gas Streams Using [hmim][Tf₂N] Ionic Liquid as a Physical Solvent

Abstract

The ionic liquid (IL) [hmim][Tf 2 N] was used as a physical solvent in an Aspen Plus simulation, employing the Peng−Robinson Equation of State (PR-EOS) with Boston−Mathias (BM) α-function and standard mixing rules, to develop a conceptual process for CO 2 capture from a shifted (undergone the water−gas shift reaction) warm fuel gas stream produced from Pittsburgh #8 coal for a 400 MWe IGCC power plant. The physical properties of the IL, including density, viscosity, surface tension, vapor pressure, and heat capacity were obtained from literature and modeled as a function of temperature. Also, available experimental solubility values for CO 2 , H 2 , H 2 S, CO, and CH 4 in this IL were compiled, and their binary interaction parameters (δ ij and l ij ) were optimized and correlated as functions of temperature. The Span−Wager EOS was also employed to generate CO 2 solubilities in [hmim][Tf 2 N] at high pressures (up to 10 MPa) and temperatures (up to 510 K). The conceptual process developed consists of four adiabatic absorbers (2.4 m inner diameter (ID), 30 m high) arranged in parallel and packed with Plastic Pall Rings of 0.025 m for CO 2 capture; 3 flash drums arranged in series for solvent (IL) regeneration with the pressureswing option; and a pressure-intercooling system for separating and pumping CO 2 up to 153 bar to the sequestration sites. The compositions of all process streams, CO 2 capture efficiency, and net power were calculated using the Aspen Plus simulator. The results showed that, based on the composition of the inlet gas stream to the absorbers, 95.12 mol % of CO 2 was captured and sent to sequestration sites; 98.37 mol % of H 2 was separated and sent to turbines; and the solvent exhibited a minimum loss of 1.23 mol %. These results indicate that the [hmim][Tf 2 N] IL could be used as a physical solvent for CO 2 capture from warm shifted fuel gas streams with high efficiency.

New process development and process evaluation for capturing CO2 in flue gas from power plants using ionic liquid [emim][Tf2N]

“…Further work is needed to realize that ionic liquids really replace traditional solvents. The purpose of this paper is to design a decarburization process for the flue gas emitted by Shen hua Guo hua jie 600 MW subcritical coal-fired unit [19][20][21][22] with ionic liquid [emim][Tf2N] as the absorbent, and use Aspen plus. The software simulates, optimizes and evaluates the process, and selects the most suitable thermal conductivity, constant pressure heat capacity, vapor pressure, viscosity, density, surface tension of the ionic liquids to absorb CO2 according to the simulation results, and the properties of the ionic liquids itself.…”

Carbon Dioxide Capture by Aqueous Ionic Liquid Solutions

“…In fact, in postcombustion CO 2 capture, it is estimated that almost3 0% of the energyo ft he powerp lant would have to be diverted to run the CO 2 -capture process. [9,10] However,t he use of traditional and neat ILs as physicals orbents for CO 2 is not particularly good because, in most of the cases, their noticeable high solubility resultsf rom their high molecular weight. Therefore, the search for new alternatives either for pre-or post-combustion CO 2 capturer emains ac hallenge.…”

“…Indeed, recent technological and economic assessmentsi ndicatet hat ILs are viable for use as "physical solvents" for CO 2 capturef rom warm-shifted fuel gas streams. [9,10] However,t he use of traditional and neat ILs as physicals orbents for CO 2 is not particularly good because, in most of the cases, their noticeable high solubility resultsf rom their high molecular weight. [11] There are two current mechanisms for CO 2 sorption in ILs.…”

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

“…The overall process contains a packed bed absorber, one flash for IL regeneration with the pressure swing option, a pressure intercooling system for separating carbon dioxide from water, and finally compressors with intercooling to increase the pressure of the captured carbon dioxide. In the system, carbon dioxide is captured, in particular, from a shifted warm pre-combustion flue gas produced by an industrial coal power plant (400 MWe) in Pittsburgh [37]. The characterization of the considered flue gas is reported in Table 1.…”

“…Generally, the temperature and pressure of feed are respectively of 500 K and 30 bar with an industrial flow rate of 25.63 kg/s. The same feed flow rate of the work of Basha et al [37] is taken into account.…”