• Energy Research

Abstract Membrane contactors offer a promising alternative to conventional CO2 absorption processes using columns. In a membrane contactor the advantages of absorption technology and membrane technology are combined as direct contact of the solution and gas feed stream is avoided by membrane barrier. In this study, the possibility of employing the enzyme carbonic anhydrase (CA) for the acceleration of CO2 reaction in MDEA and MEA solution in combination with the use of a membrane contactor was investigated in a lab scale module. The membranes employed in this study were microporous and specifically chosen to have both hydrophobic (bulk) and hydrophilic (surface) properties in order to avoid wetting of solution and reduce fouling by the enzymes simultaneously. By adding the enzyme carbonic anhydrase (CA), a significant improvement of CO2 absorption rate was observed in MDEA solution while a negative effect was observed in MEA solution. Meanwhile the porous hydrophobic membranes were coated with a highly selective poly(ionic liquids) layer increasing the affinity of CO2 towards the interfacial area and hence also the driving force. The concept may initially appear counter intuitive, as the dense membrane layer introduces an added resistance, however the active membrane material gave promising results and was observed to accelerate CO2 transport in MDEA solution. The combination of both enzyme and PILs resulted in synergies, which significantly improved CO2 absorption in MDEA solution.

AbstractThe present contribution reports on inorganic oxygen transport membranes (OTM) investigated in a specific task of the BIGCO2 project, which is one amongst the largest CCS projects in Scandinavia. The membranes are used for separation of oxygen from air at temperature typically above 800 °C. The work reports on selected membrane materials La2−xNiO4+δ belonging to the Ruddlesden-Popper phase family. While La2NiO4+δ membranes are well-known candidates for OTM application, two new materials with molar ratio La/Ni<2 are presented in this publication and their transport properties for the first time reported. Furthermore, selected results on membrane fabrication, sealing technology and assembly of small modules are presented to demonstrate the progress of the work.

AbstractThe BIGCO2 R&D (BIGCO2) Platform is an international collaborative research project aiming at developing several enabling technologies and innovative solutions supporting a large-scale deployment of CO2 capture from power generation and underground storage of CO2. All main routes for CO2 capture are investigated. The project is coordinated by SINTEF Energy Research and the budget of the current project period (2007-2011) is 16 M€.BIGCO2 builds knowledge and technology underpinning demonstration of power generation with carbon capture and storage (CCS) at industrial scale. The project aims at closing critical knowledge gaps in the CO2 chain to enable sustainable power generation from fossil fuels based on carbon capture and underground storage of CO2. BIGCO2 is unique in terms size, diversity, and the fact that it comprises the whole CO2 chain. The project includes extensive international collaborative effort bringing together expertise and research infrastructure of competent research institutes and universities, supported by leading vendors, energy companies, and oil and gas companies.This paper presents the structure, the original objectives and the achievements of BIGCO2. Further, for each research task, the results are analyzed in light of the objectives. Each task leader has analyzed the results in the following context of: originally stated objectives, results, and if the results meet the objectives.The purpose of BIGCO2 is to develop new knowledge to enable power generation with CCS. Tangible objectives are: 90% CO2 capture rate, 50% cost reduction, and a fuel-to-electricity penalty less than 7% compared with state-of-the-art power generation. Partners of the Consortium are: Statoil, GE Global Research, Statkraft, Aker Clean Carbon, Shell, TOTAL, ConocoPhillips, ALSTOM, DLR, TUM, NTNU, CICERO, SINTEF Materials and Chemistry, SINTEF Petroleum Research, and SINTEF Energy Research. The University of Oslo is a subcontractor to the project. Further, BIGCO2 benefits from a strong collaboration between the combustion research facility at Sandia National Laboratories (USA) and SINTEF Energy Research. The main sponsor of BIGCO2 is the Research Council of Norway, with considerable co-funding from the industry partners and Gassnova. The research challenges and approach are extensively presented in [1].

Abstract The enthalpy of oxidation of La(B1 − xB′x)O3 − δ (x = 0.25 and 0.75 for BB′ ≡ FeCo, MnCo, MnNi and x = 0.2 for BB′ ≡ CoCu) has been derived using solid solution models to analyse thermogravimetric measurements of oxygen non-stoichiometry vs. log(pO2) at 1273 K. For selected samples the enthalpy of oxidation has also been measured by TG-DSC, and the direct heat measurements agree well with the results from the solution models. The affinity for oxygen decreases when x in La(B1 − xB′x)O3 − δ increases from 0.25 to 0.75. This trend may be extended to a larger range of x-values (x∈[0,1]) when isotherms from the literature are included in the solution modelling. For the materials investigated in this work, the affinity for oxygen decreases in the order Mn0.75Ni0.25 > Mn0.75Co0.25 > Fe0.75Co0.25 (for x = 0.25) and in the order Mn0.25Co0.75 > Fe0.25Co0.75 > Mn0.25Ni0.75 (for x = 0.75). The Co0.80Cu0.20 containing material has the smallest affinity for oxygen among all the samples.

The majority of commercial membrane units for large-scale natural gas sweetening are based on cellulose acetate (CA). However, the low selectivity and risk for and plasticisation affect adversely the performance of CA-based systems. Herein, we present a new class of CA-derived poly(ionic liquid) (PIL) as a thin film composite (TFC) membrane for CO2 separations. CA is modified with pyrrolidinium cations through alkylation of butyl chloride, substituting the hydroxyl group in the polymer backbone, and further anion exchange to bis(trifluoromethylsulfonyl) imide, P[CA][Tf2N]. The synthesised PIL material properties are extensively studied. The CO2 separation performance of the newly synthesised materials is evaluated by gravimetric gas sorption experiments, single gas time-lag experiments on thick membranes, and mixed-gas separation experiments on TFC membranes. The results are compared to the parent material (CA) as well as a reference PIL (poly(diallyldimethyl ammonium) bis(trifluoromethylsulfonyl) imide (P[DADMA][Tf2N])). The ideal CO2/N-2 sorption selectivity of P[CA][Tf2N] is constant up to 10 bar. The single gas transport measurements in P[CA][Tf2N] reveal improved ideal CO2 selectivity for the CO2/N-2 gas pair and increased CO2 permeability for the CO2/CH4 gas pair compared to the reference PIL. Mixed-gas permeation tests demonstrated that P[CA][Tf2N]-based membranes with a 5 mu m thick selective layer has a two-fold higher CO2 flux compared to conventional CA. These results present CA modification into PILs as a successful approach promoting the higher permeate flows and improved process stability in a wide range of concentrations and pressures of CO2/N-2 and CO2/CH4 gas mixtures.

AbstractRecent results achieved on fabrication of La2NiO4+δ membranes, sealing technology and performance in pressurized conditions are presented. Porous tubular membrane supports of up to 1 m length are prepared by ceramic extrusion. Asymmetric La2NiO4+δ membranes are prepared by coating dense selective layers of 10-15μm thickness onto the porous supports. Glass ceramic seals in the system Na2O-CaO-Al2O3-SiO2 are currently being evaluated for joining the membranes with high temperature steel alloys coated with a corrosion resistance protective layer. By adjusting the composition of the glass system the thermal expansion coefficient is tailored to match that of the membrane and steel material. Good seal adherences towards these materials are obtained. Long term oxygen flux measurements (>4000hours continuous operation) performed on symmetric (dense) La2NiO4+δ membranes are conducted under various conditions (atmosphere, temperature, pressure). The oxygen flux dependency on the oxygen partial pressure (pO2) is investigated by increasing the feed pressure and oxygen content. An asymptotic flux behavior is observed with increasing pO2. It is seen a significant increase in the flux (by a factor of 6) when increasing the feed pO2 from 0.8 to 2.4 bars while a less significant pO2 dependency is observed with further increase.

Abstract The process behavior of a Gas Switching Reforming (GSR) reactor was studied using three different iron-based oxygen carrier materials: Iron-oxide on Alumina, Iron-Nickel oxide on Alumina and Iron-Ceria on Alumina. It was observed that, for all oxygen carriers, the fuel stage reaction occurs in two distinct sub-stages when feeding methane and steam to a bed of oxidized material, with methane combustion dominating the first and methane reforming dominating the second. This reflects a change in the catalytic activity of the oxygen carrier as it is reduced. The alumina support was observed to play a significant role in the reactions occurring, with the redox-active phases being hematite-structured Fe2O3 (oxidized form) and spinel-structured (FeNiAl)3O4 (reduced form). The Nickel-containing oxygen carrier outperformed the others in the reforming sub-stage, showing 40% improved methane conversion. The feed of dry methane only during the combustion sub-stage was found to improve methane conversion to syngas in the subsequent reforming sub-stage from 75% to 80% at 800 °C. Results also show that methane conversion improves with the increase in operating temperature and steam/carbon ratio. Autothermal operation of the reactor was achieved with repeatable performance over several redox cycles. The study therefore successfully demonstrated autothermal N2-free syngas production with integrated CO2 capture from the fuel combustion required to supply heat to the endothermic reforming reactions.