Development of a Conceptual Process for Selective Capture of CO₂ from Fuel Gas Streams Using Two TEGO Ionic Liquids as Physical Solvents

Two ionic liquids (ILs), TEGO IL K5 and TEGO IL P51P, were used as physical solvents to develop a conceptual process for CO₂ capture from a shifted warm fuel gas stream produced from Pittsburgh no. 8 coal for a 400 MWe power plant. The physical properties of the two ILs and the solubilities of CO₂, H₂, N₂, and H₂S in the TEGO IL K5 solvent, as well as those of CO₂ and H₂ in the TEGO IL P51P solvent, were measured in our laboratories at pressures up to 30 bar and temperatures from 300 to 500 K. The Peng–Robinson equation-of-state (P-R EOS) with Boston–Mathias (BM) α function and standard mixing rules was used in the development of the process, and the solubility data were used to obtain the binary interaction parameters (δ_ij and l_ij) between the shifted gas constituents and the two ILs. The binary interaction parameters were then correlated as functions of temperature. The conceptual process consists of four identical adiabatic packed-bed absorbers (4.5 m i.d., 27 m height, packed with 0.0254 m plastic Pall Rings) arranged in parallel for CO₂ capture, three flash drums arranged in series for solvent regeneration,and two pressure/intercooling systems for separating and pumping CO₂ to sequestration sites. The compositions of all process streams, CO₂ capture efficiency, and net power were calculated using Aspen Plus for the two solvents. The results showed that TEGO IL K5 and TEGO IL P51P were able to capture 91.28% and 90.59% of CO₂ in the fuel gas stream, respectively.