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, H-2, N-2, and H2S in the TEGO IL K5 solvent, as well as those of CO2 and H-2 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) alpha 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 (delta(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.