Yngve Larring

La0.8Sr0.2Co0.2Fe0.8O3−δ as a potential oxygen carrier in a chemical looping type reactor, an in-situ powder X-ray diffraction study

Perovskite type materials which can change oxygen content quickly under changing oxygen partial pressures are believed to be suitable materials for chemical looping of natural gas. In order to investigate the oxidation/reduction of these materials in-situ powder X-ray diffraction was used to study the La1−xSrxCo1−yFeyO3−δ system. It was found that for samples with high iron content a hexagonal/orthorhombic to cubic phase transition was observed upon heating in a reductive atmosphere and that the cationic lattice is maintained upon reduction. On the other hand, the samples with high cobalt content were unstable with respect to heating in a reductive atmosphere as they decomposed to form La2O3, Co and at least one additional phase. Once a suitable candidate had been obtained a chemical looping experiment was carried out using H2 as a model fuel, again using in-situ powder X-ray diffraction.

Oxygen and Hydrogen Separation Membranes Based on Dense Ceramic Conductors

Publisher Summary This chapter discusses oxygen and hydrogen separation membranes based on dense ceramic conductors. The theoretical basis for understanding the transport properties in dense oxides is introduced. This treatment starts from basic defect chemistry and the equations for flux of oxygen ions and protons. The most important families of oxides and the specific compositions that demonstrate high ionic diffusion rates are introduced. The important issue of materials stability under operation is then discussed, taking into consideration, the typical membrane working condition characterized by high temperature, the presence of significant chemical, mechanical, and thermal gradients, as well as aggressive chemical components. The chapter illustrates several examples of membrane applications. The possibility of mass and heat integration in novel process designs and the potentials of dense ceramic membranes in power generation with CO2 capture are demonstrated. The chapter also discusses the latest developments in solid oxide fuel cell (SOFC) and prospects toward high-temperature water electrolysis.

Development of a hydrogen membrane reformer based CO2 emission free gas fired power plant

Publisher Summary The CO 2 Capture Project (CCP) is an international effort to develop new technology to capture and store CO 2 currently emitted by fixed sources such as turbines, heaters and boilers. Post combustion, pre-combustion, and “oxy-fuel” approaches have been studied in the chapter. In the pre-combustion approach fossil fuel is converted to hydrogen fuel and CO 2 is recovered for storage. Methane Steam Reforming (MSR) and water CO shift reactions are commonly used in hydrogen production from natural gas followed by separation of CO 2 by means of e.g. amine scrubbing. This technique gives high CO 2 purity, but is quite energy intensive. The aim of CCP funded work has been to develop novel dense hydrogen mixed conducting ceramic membranes (HMCM) with sufficient H 2 transport rates and stability under normal steam reforming conditions. Based on the measurements and theoretical evaluations, a main candidate materials system, was selected. Supported membrane tubes have been fabricated and one tube was tested in a pressurized hydrogen flux test rig under relevant process conditions. The measured hydrogen flux compared favorably with model predictions based on the atmospheric laboratory tests. However, the tested membrane tube was not gas impervious and improved membranes tubes need to be fabricated and tested to verify the project results. The novel HMCM based concept allows close to 100% CO 2 capture and the loss in efficiency is estimated to be only 5%-points compared with a conventional combined cycle power plant without CO 2 capture.

Critical Issues of Metal-Supported Fuel Cell

Metal-Supported SOFCs (MS-SOFCs), wherein the supporting component of the cell is made of a porous alloy, are referred to as the third generation SOFC operating at temperature down to 500–650 °C. This technology is expected to decrease significantly capital and operational costs, while increasing the lifetime of cells due to lower operating temperature and higher redox stability. The chapter reviews MS-SOFC development with a focus given to main issues affecting the performance and longevity of single cells. It addresses critical issues for selection of alloy materials based on material cost, thermal expansion coefficient, corrosion rate, particle size, and Cr evaporation issues. Protective coatings, cell architecture, and advanced fabrication processes are then presented to illustrate the level of technical refinement currently achieved. Performance of produced MS-SOFCs is finally discussed to pinpoint factors contributing to major electrochemical losses and possible routes for improvement are reported.

Chapter 21 – Grace: Development of Supported Palladium Alloy Membranes

The Grangemouth Advanced CO 2 Capture Project (GRACE) was a two-year (2002–2003) research program concerned with the capture of CO 2 from a UK refinery site. One of the technologies that were pursued in the program was the development of hydrogen gas separation by membrane technology. Such technology can be used to enhance the water gas shift reaction for CO 2 capture by pre-combustion decarbonization of refinery fuel gas. This chapter presents the development and testing of flat and tubular supported palladium alloy membrane modules. Membranes with thickness in the range of 1 μm are prepared by a two-stage magnetron sputter process using a single crystal silicon wafer as intermediate support and a wire mesh or porous material as final support. Testing of the hydrogen flux through the tubular membranes at 300 °C has shown that permeance values of about 3 × 10 −6 mol/(m 2 s Pa) can be attained. For a flat membrane, peak permeance values of about 6.8 × 10 −6 mol/(m 2 s Pa) is attained at 300 °C. The membranes are able to separate hydrogen gas from nitrogen gas with 100% selectivity within the detection limits of the equipment. Tubular membrane supports that have been reinforced by a steel insert are tested up to 14 bar transmembrane pressure. Although the selectivity drops at high pressure, the tests show that the membrane film does not disintegrate at high pressure even at 300 °C.

Chapter 7 – Lifetime Issues for Solid Oxide Fuel Cell Interconnects

Abstract The manuscript aims to introduce the reader to the main drawbacks interconnects face in SOFC environments, giving the basis to understand the problem and the literature references to deepen the knowledge on each specific topic.The chapter is divided in two parts: a theoretical description of the degradation phenomena affecting the interconnects (notably corrosion and mechanical stresses) and a table presenting its behaviour in operating conditions, at the end of the chapter. In the first part, influence of oxygen, fuel and water partial pressure on scale growth process are taken in consideration, with the latter being the most influent. A paragraph is dedicated to the corrosion behaviour of sealants too, while the mechanical degradation part is focused on the model methodology currently used to forecast stress-strain behaviour in SOFC metal interconnects. A paragraph describing solutions to mitigate interconnect lifetime issues is provided at the end of this section. In the table are presented results of interconnects coupled with different types of SOFC cell: anode, electrolyte and metal supported and tested in operating conditions. From the analysis of the data collected in the table, it can be said that current solutions to extend lifetime are already reasonably effective

Lifetime Issues for Solid Oxide Fuel Cell Interconnects, Solid Oxide Fuel Cell Lifetime and Reliability

Abstract The manuscript aims to introduce the reader to the main drawbacks interconnects face in SOFC environments, giving the basis to understand the problem and the literature references to deepen the knowledge on each specific topic.The chapter is divided in two parts: a theoretical description of the degradation phenomena affecting the interconnects (notably corrosion and mechanical stresses) and a table presenting its behaviour in operating conditions, at the end of the chapter. In the first part, influence of oxygen, fuel and water partial pressure on scale growth process are taken in consideration, with the latter being the most influent. A paragraph is dedicated to the corrosion behaviour of sealants too, while the mechanical degradation part is focused on the model methodology currently used to forecast stress-strain behaviour in SOFC metal interconnects. A paragraph describing solutions to mitigate interconnect lifetime issues is provided at the end of this section. In the table are presented results of interconnects coupled with different types of SOFC cell: anode, electrolyte and metal supported and tested in operating conditions. From the analysis of the data collected in the table, it can be said that current solutions to extend lifetime are already reasonably effective

Lifetime Issues for Solid Oxide Fuel Cell Interconnects

Abstract The manuscript aims to introduce the reader to the main drawbacks interconnects face in SOFC environments, giving the basis to understand the problem and the literature references to deepen the knowledge on each specific topic.The chapter is divided in two parts: a theoretical description of the degradation phenomena affecting the interconnects (notably corrosion and mechanical stresses) and a table presenting its behaviour in operating conditions, at the end of the chapter. In the first part, influence of oxygen, fuel and water partial pressure on scale growth process are taken in consideration, with the latter being the most influent. A paragraph is dedicated to the corrosion behaviour of sealants too, while the mechanical degradation part is focused on the model methodology currently used to forecast stress-strain behaviour in SOFC metal interconnects. A paragraph describing solutions to mitigate interconnect lifetime issues is provided at the end of this section. In the table are presented results of interconnects coupled with different types of SOFC cell: anode, electrolyte and metal supported and tested in operating conditions. From the analysis of the data collected in the table, it can be said that current solutions to extend lifetime are already reasonably effective