Novel CO₂-tolerant ion-transporting ceramic membranes with an external short circuit for oxygen separation at intermediate temperatures

Abstract

Here we report a new concept for oxygen separation by the oxygen ion conducting ceramic membrane with an external short circuit. With the strong chemical stability against acidic gases like CO 2 and the higher oxygen fluxes at lower temperatures, this novel membrane concept could possibly result in a breakthrough for tonnage oxygen production to improve the viability of these clean energy technologies.Global climate change is challenging the existing power generation system and new clean energy delivery technologies with reduced CO 2 emissions are urgently required. Among the promising options to integrate the existing coal-fired power stations with CO 2 capture to produce low emission electricity, oxyfuel combustion seems to be more feasible than other options and several big projects have been initiated in the world such as CS Callide (Australia), Vattenfal (Germany), Inabensa (Spain), OXY-CFB-300 (Spain), TotalLacq (France) and FutureGen2 (USA) program with billion dollar investments for each of these projects. Under the oxyfuel concept, coal will be fired with pure O 2 or an O 2 /CO 2 mixture instead of air; the major constituent of the waste gas produced during the new combustion process is highly concentrated CO 2 enabling its capture more economically feasible. 1-5 However, all these oxyfuel combustion projects are still in the demonstration stage and cannot compete commercially with the conventional air-fired coal power plants because of the significantly high investment and operation costs. Among the basic operational units of the oxyfuel combustion, the complex air separation unit (ASU) via the cryogenic method to provide pure oxygen is the most expensive section, accounting for approximately 50% of the overall CO 2 capture cost. 6,7 Addressing this concern to reduce the cost, oxygen ionic conducting ceramic membranes have received increasing attention because they are envisaged to replace the cryogenics and reduce O 2 production cost by 35% or more, offering the potential to tackle these energy penalties and improve the viability of zero emission technology. 8-12 However, these membranes must possess sufficiently high oxygen permeability and structural stability to withstand the real process conditions which include the presence of highly concentrated CO 2 .The two main categories of ionic transport ceramic membranes for oxygen separation attracting intense attention are pure oxygen ion conducting membranes 13,14 and mixed ionic-electronic conducting (MIEC) membranes. [15][16][17][18][19][20][21] For the pure ion conducting membranes with the concept schematically shown in Fig. 1A, an external power source and electrodes are required to provide the electric current. Driven by the electrical potential gradient, the oxygen transport can be precisely controlled in quantity by applying the electric current so the oxygen can be pumped in either direction regardless of the oxygen

CO2 and water vapor-tolerant yttria stabilized bismuth oxide (YSB) membranes with external short circuit for oxygen separation with CO2 capture at intermediate temperatures

“…In our previous work with the example of fluorite-type Sm 0.2 Ce 0.8 O 1.9 (SDC), a new membrane concept-pure ion conducting membrane with external short circuit was developed to use these robust ion conductors for O 2 separation with conceptual depiction shown in Fig. 1 [32]. The measured values of electrical current agree very well with the theoretical calculation using the equation correlating Faraday constant and O 2 fluxes.…”

Efficient and CO2-tolerant oxygen transport membranes prepared from high-valence B-site substituted cobalt-free SrFeO3−δ

“…Several combinations have been proposed, e.g., membranes with external or internal shortcircuiting electrodes, dual-phase membranes comprised of a spinel oxide and an ionic conductor, and dual-layer membranes of SrFe 0.8 Nb 0.2 O 3-δ /Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ or Ce x Gd 1-x O 2-δ /La x Sr 1-x Co y Fe 1-y O 3-δ [23][24][25][26][27][28]. Although considerable efforts towards applications in CO 2 -containing atmosphere have been made, rather complex processes for the fabrication, the high price of the short-circuiting electrode, and concerns regarding the chemical compatibility and interfacial ion diffusion between two phases/layers, as well as the quite low oxygen permeability have not been completely resolved.…”

Chemically and thermo-mechanically stable LSM–YSZ segmented oxygen permeable ceramic membrane

“…Oxygen permeable ceramic membranes have received a great deal of attention as a potential way to significantly reduce the costs associated with oxygen production [1][2][3][4]. These ceramic membranes, based on mixed ionic and electronic conductors, are produced in two types: the single-phase membrane [5,6] and the dual-phase membrane [7][8][9][10].…”