CO 2 capture from natural gas combined cycles by CO 2 selective membranes

Abstract

This paper performs a techno-economic analysis of natural gas-fired combined cycle (NGCC) power plants integrated with CO2 selective membranes for post-combustion CO2 capture. The configuration assessed is based on a two-membrane system: a CO2 capture membrane that separates the CO2 for final sequestration and a CO2 recycle membrane that selectively recycles CO2 to the gas turbine compressor inlet in order to increase the CO2 concentration in the gas turbine flue gas. Three different membrane technologies with different permeability and selectivity have been investigated. The mass and energy balances are calculated by integrating a power plant model, a membrane model and a CO2 purification unit model. An economic model is then used to estimate the cost of electricity and of CO2 avoided. A sensitivity analysis on the main process parameters and economic assumptions is also performed. It was found that a combination of a high permeability membrane with moderate selectivity as a recycle membrane and a very high selectivity membrane with high permeability used for the capture membrane resulted in the lowest CO2 avoided cost of 75 US$/tCO2. This plant features a feed pressure of 1.5 bar and a permeate pressure of 0.2 bar for the capture membrane. This result suggests that membrane systems can be competitive for CO2 capture from NGCC power plants when compared with MEA absorption. However, to achieve significant advantages with respect to benchmark MEA capture, better membrane permeability and lower costs are needed with respect to the state of the art technology. In addition, due to the selective recycle, the gas turbine operates with a working fluid highly enriched with CO2. This requires redesigning gas turbine components, which may represent a major challenge for commercial deployment.

Feasibility of Selective Exhaust Gas Recycle Process for Membrane-based CO2 Capture from Natural Gas Combined Cycles – Showstoppers and Alternative Process Configurations

“…One of the limitations of the S-EGR process noted in literature [5] is that the gas turbine components will have to be redesigned as the gas turbine operates in highly CO 2 enriched conditions. The major technical impact of EGR is on the combustion systems as it affects the composition of the air entering the combustor.…”

“…The S-EGR process includes a membrane system that utilizes the air to the gas turbine as sweep to separate the CO 2 selectively for recycle back to the gas turbine process downstream of the membrane based post-combustion capture process, as shown in Figure 1. This process scheme has been subsequently used by other research groups to present a case for membrane based postcombustion capture from NGCC [5].…”

Making gas‐CCS a commercial reality: The challenges of scaling up

“…Configurations using calcium looping technology for NGCCs have been also recently analyzed, even in combination with the exhaust gas recirculation strategy discussed above . The use of membranes has also been proposed, using different configurations, multi‐stage membrane layouts and/or EGR and S‐EGR to enhance the driving force for the CO 2 separation . More complex options have been also explored, such as the use of molten carbonate fuel cells in combination with gas membranes or with CO 2 cryogenic separation …”

“…80 The use of membranes has also been proposed, using different configurations, multi-stage membrane layouts and/or EGR and S-EGR to enhance the driving force for the CO 2 separation. 17,[81][82][83][84][85] More complex options have been also explored, such as the use of molten carbonate fuel cells in combination with gas membranes 86 or with CO 2 cryogenic separation. 87 Amongst all the alternatives mentioned above, CO 2 capture using amines is currently regarded as the most advanced post-combustion technology, with two plants already operating at commercial scale (for coal applications).…”

Membrane-Based Processes: Optimization of Hydrogen Separation by Minimization of Power, Membrane Area, and Cost

“…In literature, several authors have addressed the simulation or model-based optimization of membrane-based processes for gas separation in several applications, such as gas natural treatment ( [7,10,12]), CO 2 capture ( [6,[13][14][15]), and H 2 separation ( [9,16,17]). For instance, Xu et al [17] studied the potential applications of membrane-based processes for H 2 purification and pre-combustion CO 2 capture.…”