Article pubs.acs.org/IECR
Development of a Conceptual Process for Selective Capture of CO2 from Fuel Gas Streams Using Two TEGO Ionic Liquids as Physical Solvents Omar M. Basha,‡ Yannick J. Heintz,†,‡ Murphy J. Keller,† David R. Luebke,† Kevin P. Resnik,†,§ and Badie I. Morsi*,†,‡ †
National Energy Technology Laboratory, U. S. Department of Energy, P. O. Box 10940, Pittsburgh, Pennsylvania 15236, United States ‡ Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States § URS Corporation, Pittsburgh, Pennsylvania 15236, United States S Supporting Information *
ABSTRACT: 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 (δij and lij) 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.
1. INTRODUCTION AND BACKGROUND Compared to coal-powered combustion systems, integrated gasification combined cycle (IGCC) is considered the most promising process for power generation due to its high thermal efficiency potential (up to 52% HHV1), low emissions, and the flexibility in using different feedstocks.2 For the IGCC process to become commercially viable, however, all contaminants, such as Hg, As, Cd, Se, SOx, NOx, H2S, and CO2 in the syngas have to be removed prior to combustion. Cold-, hot-, and warm-gas acid gas removal technologies from syngas streams to IGCC were discussed by Vidaurri et al.3 and have been summarized by Heintz et al.4 Among the emission control technologies, the warm-gas cleanup process is the most appropriate and efficient technique for IGCC systems since it can remove multicontaminants from the syngas, such as sulfur and heavy metals at high temperatures without the need of expensive alloy equipment or cooling systems, while incurring a lower energy penalty compared to the cold-gas and hot-gas cleanup.4 The warm-gas cleanup process significantly increases the thermal efficiency and reduces the capital and operating costs of IGCC when compared with other conventional processes.5 Given the benefits of the warm-gas cleanup process, there is a need to develop novel warm-gas cleanup processes to mitigate the emission of sulfur, chlorides, NH3, CO2, Hg, As, Se, and Cd, and further reduce the cost of energy production associated with IGCC power generation. © 2014 American Chemical Society
Recently, ionic liquids (ILs) have been investigated as potential physical solvents for acid gas removal from warm-gas streams.4,6 ILs consist mainly of a large organic asymmetric cation (i.e., pyridinium, imidazolium, and phosphonium, etc.) and either an inorganic (i.e., Cl−, BF4−, PF6−, CF3SO3−, and NTf2−) or an organic (i.e., RCOO−) anion,7 which in combination prevent the formation of a stable crystal lattice.8,9 The physical properties (melting point, viscosity, gas solubility, etc.) of ILs are strongly affected by their anion and cation compositions.7 In general, ILs exist as liquids at a low temperature (
