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Abanades J.C.,CSIC - National Coal Institute
Applied Energy | Year: 2014

This work presents a comprehensive conceptual design of a Ni-based chemical looping combustion process (CLC) carried out in fixed bed reactors. The process is intended to exploit the well-known advantages of the Ni/NiO redox system for CLC applications in terms of high reactivity, O2 carrying capacity and chemical and thermal stability. Solutions to the problem of heat management in fixed bed reactors at high temperature and high pressure are described, while a continuous flow of nitrogen for driving a gas turbine is produced. Each reactor involved in the process goes through a cyclic sequence of five reaction and heat transfer stages. Cool product gas recirculations are incorporated into the Ni oxidation and NiO reduction stages in order to moderate the maximum temperatures in the beds and control the displacement of the reaction and heat transfer fronts. A preliminary conceptual design of the process has been carried out to determine the minimum number of reactors needed for continuous operation in typical large-scale CO2 capture systems. Basic reactor models and assumptions based on an ideal plug flow pattern have been used in all the reactors during the chemical reactions and the heat transfer operations. This has made it possible to identify reasonable operating windows for the eight fixed-bed reactors that make up the CO2 capture system, and has demonstrated not only its technical viability but also its great potential for further development. © 2014 Elsevier Ltd. Source

Sevilla M.,CSIC - National Coal Institute | Mokaya R.,University of Nottingham
Energy and Environmental Science | Year: 2014

Porous carbons have several advantageous properties with respect to their use in energy applications that require constrained space such as in electrode materials for supercapacitors and as solid state hydrogen stores. The attractive properties of porous carbons include, ready abundance, chemical and thermal stability, ease of processability and low framework density. Activated carbons, which are perhaps the most explored class of porous carbons, have been traditionally employed as catalyst supports or adsorbents, but lately they are increasingly being used or find potential applications in the fabrication of supercapacitors and as hydrogen storage materials. This manuscript presents the state-of-the-art with respect to the preparation of activated carbons, with emphasis on the more interesting recent developments that allow better control or maximization of porosity, the use of cheap and readily available precursors and tailoring of morphology. This review will show that the renewed interest in the synthesis of activated carbons is matched by intensive investigations into their use in supercapacitors, where they remain the electrode materials of choice. We will also show that activated carbons have been extensively studied as hydrogen storage materials and remain a strong candidate in the search for porous materials that may enable the so-called Hydrogen Economy, wherein hydrogen is used as an energy carrier. The use of activated carbons as energy materials has in the recent past and is currently experiencing rapid growth, and this review aims to present the more significant advances. This journal is © the Partner Organisations 2014. Source

Titirici M.-M.,Max Planck Institute of Colloids and Interfaces | White R.J.,Max Planck Institute of Colloids and Interfaces | Falco C.,Max Planck Institute of Colloids and Interfaces | Sevilla M.,CSIC - National Coal Institute
Energy and Environmental Science | Year: 2012

This perspective review paper provides an overview on recently developed carbon material technology synthesised from the hydrothermal carbonisation (HTC) approach, with a particular focus on the carbon formation mechanism, perspectives on large scale production, nanostructuring, functionalisation and applications. Perceptions on how this technology will be developed especially with regard to application fields where the use of HTC-derived materials could be extended will also be introduced and discussed. © 2012 The Royal Society of Chemistry. Source

Sevilla M.,CSIC - National Coal Institute | Fuertes A.B.,CSIC - National Coal Institute
Journal of Colloid and Interface Science | Year: 2012

Highly porous carbons have been prepared by the chemical activation of two mesoporous carbons obtained by using hexagonal- (SBA-15) and cubic (KIT-6)-ordered mesostructured silica as hard templates. These materials were investigated as sorbents for CO2 capture. The activation process was carried out with KOH at different temperatures in the 600-800°C range. Textural characterization of these activated carbons shows that they have a dual porosity made up of mesopores derived from the templated carbons and micropores generated during the chemical activation step. As a result of the activation process, there is an increase in the surface area and pore volume from 1020m2g-1 and 0.91cm3g-1 for the CMK-8 carbon to a maximum of 2660m2g-1 and 1.38cm3g-1 for a sample activated at 800°C (KOH/CMK-8 mass ratio of 4). Irrespective of the type of templated carbon used as precursor or the operational conditions used for the synthesis, the activated samples exhibit similar CO2 uptake capacities, of around 3.2mmolCO2g-1 at 25°C. The CO2 capture capacity seems to depend on the presence of narrow micropores (<1nm) rather than on the surface area or pore volume of activated carbons. Furthermore, it was found that these porous carbons exhibit a high CO2 adsorption rate, a good selectivity for CO2-N2 separation and they can be easily regenerated. © 2011 Elsevier Inc.. Source

Sevilla M.,CSIC - National Coal Institute | Fuertes A.B.,CSIC - National Coal Institute
Journal of Materials Chemistry A | Year: 2013

Highly porous carbons with different textural properties were obtained in only one step by means of simple heat-treatment of organic salts of Na, K or Ca. The pore characteristics were tuned from a microporous to a mesoporous carbon by simply choosing the appropriate organic salt. This journal is © The Royal Society of Chemistry. Source

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