Oxy-fired fluidized bed combustors with a flexible power output using circulating solids for thermal energy storage

This paper presents a power plant concept based on an oxy-fired circulating fluidized bed combustor (oxy-CFBC) combined with thermal energy storage on a large scale. The concept exploits to full advantage the large circulation flows of high temperature solids that are characteristic of these systems. Two solid storage silos (one for high temperature and the other for low temperature solids) connected to the oxy-fired CFBC allow variability in power output without the need to modify the fuel firing rate and/or the mass flow of O2 to the combustor. During the periods of high power demand the system can deliver additional thermal power by extracting heat from a series of fluidized bed heat exchangers fed with solids from the high temperature silo. Likewise, during period of low power demand, the thermal power output can be reduced by using the energy released in the combustor to heat up the low temperature solids on their way from the low temperature silo to the oxy-CFBC and storing them in the high temperature silo located below the cyclone. A preliminary economic analysis of two designs indicates that this highly flexible system could make this type of power plant more competitive in the electricity markets where fossil fuels with CCS will be required to respond to a large variability in power output.Y.A. Criado thanks the Government of the Principality of Asturias for a Ph.D. fellowship (Severo Ochoa Program). B. Arias thanks the Spanish MINECO for the award of a Ramon y Cajal contract.Peer reviewe

Desarrollo, seguimiento y evaluación de la formación especializada en el modelo troncal.

La implantación de la troncalidad en la formación sanitaria especializada en España es el cambio más profundo y complejo que se introduce en la regulación del sistema de formación especializada desde el año 1978. Este hecho hace imprescindible la puesta en marcha de un conjunto de elementos estructurales, organizativos y de acción dirigidos específicamente a garantizar que el proceso se implante siguiendo las premisas y calendarios previstos en las disposiciones legales que le dan soporte y de acuerdo con conceptos y evidencias científicamente fundados y que traduzcan también la experiencia acumulada en España y otros países en relación con estos temas

Testing postcombustion CO2 capture with CaO in a 1.7 MWt pilot facility

AbstractCalcium looping, CaL, is a new and rapidly developing technology that makes use of CaO as a high temperature regenerable sorbent of CO2. Previous theoretical and lab scale studies have shown that this technology could lead to a substantial reduction in the cost of CO2 capture and energy penalties because heat can be effectively recovered from this high temperature solid looping system. We report in this paper on the first results from a pilot plant designed to demonstrate the viability of postcombustion capture of CO2 using CaL under conditions comparable to those expected in a large scale plant. The pilot includes two interconnected circulating fluidized bed reactors of 15 m height: a CO2 absorber (carbonator) able to treat up to 2400kg/h (equivalent to about 1.7 MWth), and an oxy-fired CFB calciner with a firing power between 1-3 MWth. CO2 capture efficiencies over 90% have been experimentally observed, including continuous operation with highly cycled solids in the system (i.e. with modest CO2 carrying capacities). SO2 capture is shown to be extremely high, with concentrations of SO2 well below 10 ppmv at the exit of the carbonator. Closure of carbon and sulfur balances is satisfactory. These results should be valuable base for model validation and scaling up purposes in future stages of the EU FP7 “CaOling” project, under which this investigation has been carried out

Diversity and Functional Traits of Lichens in Ultramafic Areas: A Literature Based Worldwide Analysis Integrated by Field Data at the Regional Scale

While higher plant communities found on ultramafics are known to display peculiar characteristics, the distinguishability of any peculiarity in lichen communities is still a matter of contention. Other biotic or abiotic factors, rather than substrate chemistry, may contribute to differences in species composition reported for lichens on adjacent ultramafic and non-ultramafic areas. This work examines the lichen biota of ultramafics, at global and regional scales, with reference to species-specific functional traits. An updated world list of lichens on ultramafic substrates was analyzed to verify potential relationships between diversity and functional traits of lichens in different Köppen–Geiger climate zones. Moreover, a survey of diversity and functional traits in saxicolous communities on ultramafic and non-ultramafic substrates was conducted in Valle d’Aosta (North-West Italy) to verify whether a relationship can be detected between substrate and functional traits that cannot be explained by other environmental factors related to altitude. Analyses (unweighted pair group mean average clustering, canonical correspondence analysis, similarity-difference-replacement simplex approach) of global lichen diversity on ultramafic substrates (2314 reports of 881 taxa from 43 areas) displayed a zonal species distribution in different climate zones rather than an azonal distribution driven by the shared substrate. Accordingly, variations in the frequency of functional attributes reflected reported adaptations to the climate conditions of the different geographic areas. At the regional scale, higher similarity and lower species replacement were detected at each altitude, independent from the substrate, suggesting that altitude-related climate factors prevail over putative substrate–factors in driving community assemblages. In conclusion, data do not reveal peculiarities in lichen diversity or the frequency of functional traits in ultramafic areas

Emerging CO2 capture systems

In 2005, the IPCC SRCCS recognized the large potential for developing and scaling up a wide range of emerging CO2 capture technologies that promised to deliver lower energy penalties and cost. These included new energy conversion technologies such as chemical looping and novel capture systems based on the use of solid sorbents or membrane-based separation systems. In the last 10 years, a substantial body of scientific and technical literature on these topics has been produced from a large number of R&D projects worldwide, trying to demonstrate these concepts at increasing pilot scales, test and model the performance of key components at bench scale, investigate and develop improved functional materials, optimize the full process schemes with a view to a wide range of industrial applications, and to carry out more rigorous cost studies etc. This paper presents a general and critical review of the state of the art of these emerging CO2 capture technologies paying special attention to specific process routes that have undergone a substantial increase in technical readiness level toward the large scales required by any CO2 capture system

Demonstration of steady state CO2 capture in a 1.7 MWth Calcium looping pilot

[EN]Calcium looping, CaL, is rapidly developing as a postcombustion CO2 capture technology because its similarity to existing power plants using circulating fluidized bed combustors, CFBC. In this work we present experimental results from a pilot built to demonstrate the concept at the MWth scale. The pilot plant treats 1/150 of the flue gases of an existing CFBC power plant (“la Pereda”) and it has been operated in steady state for hundreds of hours of accumulated experimental time. The pilot includes two 15 m height interconnected circulating fluidized bed reactors: a CO2 absorber (or carbonator of CaO) and a continuous CaCO3 calciner operated as an oxy-fuel CFBC. Operating conditions in the reactors are resembling those expected in large CaL CO2 capture systems in terms of reactor temperatures, gas velocities, solid compositions and circulation rates and reaction atmospheres. The evolution of CO2 capture efficiencies and solid properties (CO2 carrying capacity and CaO conversion to CaCO3 and CaSO4) have been studied as a function of key operating conditions. It is demonstrated that CO2 capture efficiencies over 90% are feasible with a supply of active CaO slightly over the molar flow of CO2 entering the carbonator. Closure of carbon and sulphur balances has been satisfactory during steady state periods. A basic reactor model developed from smaller test facilities seems to provide a reasonable interpretation of the observed trends. This should facilitate the further scale up of this new technology.The research presented in this work has received partial funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under the GA 241302-CaOling Project and from the PCTI Asturias Regional Government. M.E. Diego acknowledges a fellowship grant under the CSIC JAE Programme, co-funded by the European Social Fund. M. Fernández, M. Pereiro and A. Méndez have been excellent operators of the rig during the experimental runs of the pilot.Peer reviewe

Postcombustion CO2 capture with CaO. Status of the technology and next steps towards large scale demonstration

10th International Conference on Greenhouse Gas Control Technologies[EN] Postcombustion CO2 capture using CaO requires a large scale circulating fluidized bed (CFB) reactor as CO2 absorber, operating between 600-700ºC. In addition, a large scale oxy-fired CFBC must be interconnected to this reactor to allow for the decomposition of CaCO3 formed in the carbonator. This allows for a continuous regeneration of the CaO sorbent and the production of a CO2 rich stream suitable for final purification and compression. Despite the known limitations associated to this technology (mainly sorbent deactivation, solid attrition, and high energy requirements in the calciner) clear operating windows have been identified at which the process could be implemented in practice using the know-how on CFBC technology. Theoretical studies on the thermal integration of a carbonation-calcination loop in new and existing power plants have shown that the technology has the potential to achieve a substantial reduction (around 30%) in capture cost and energy penalties with respect to stand-alone oxy-fired systems. Since the solid materials and operating conditions in the CFB units are similar to those present in existing large scale CFBCs, the prospects for a rapid scaling up of the technology are very promising. A rapid development is taking place in recent years by demonstrating the key concepts in laboratory scale test rigs of 10s of kW. However, it is essential to move on to the next phase of pilot testing and validate the results in conditions fully comparable with those expected in large scale units. We describe here the design of a 1 MWth pilot plant to capture 70-95% of the CO2 contained in the flue gas from a 1/150 side stream emitted by an existing 50MWe CFB power plant. The pilot is made up of two interconnected CFB reactors of 15 m height. The construction of the pilot has been initiated and is expected to enter into full operation in the first half of 2011, providing the necessary experimental results to decide on the launching of an aggressive development programme that aims to demonstrate the technology at large scale well before 2020.This work is being funded by the European Commission 7th Framework Programme under the CaOling project.Peer reviewe

Desarrollo, seguimiento y evaluación de la formación especializada en el modelo troncal.

La implantación de la troncalidad en la formación sanitaria especializada en España es el cambio más profundo y complejo que se introduce en la regulación del sistema de formación especializada desde el año 1978. Este hecho hace imprescindible la puesta en marcha de un conjunto de elementos estructurales, organizativos y de acción dirigidos específicamente a garantizar que el proceso se implante siguiendo las premisas y calendarios previstos en las disposiciones legales que le dan soporte y de acuerdo con conceptos y evidencias científicamente fundados y que traduzcan también la experiencia acumulada en España y otros países en relación con estos temas

Oxyfuel carbonation/calcination cycle for low cost CO2 capture in existing power plants

6 pages, 3 figures, 3 tables.-- Printed version published Oct 2008.Postcombustion CO2 capture is the best suitable capture technology for existing coal power plants. This paper focuses on an emerging technology that involves the separation of CO2 using the reversible carbonation reaction of CaO to capture CO2 from the flue gas, and the calcination of CaCO3 to regenerate the sorbent and produce concentrated CO2 for storage. We describe the application to this concept to an existing (with today’s technology) power plant. The added capture system incorporates a new supercritical steam cycle to take advantage of the large amount of heat coming out from the high temperature capture process (oxyfired combustion of coal is needed in the CaCO3 calciner). In these conditions, the capture system is able to generate additional power (26.7% efficiency respect to LHV coal input to the calciner after accounting for all the penalties in the overall system), without disturbing the steam cycle of the reference plant (that retains its 44.9 efficiency). A preliminary cost study of the overall system, using well established analogues in the open literature for the main components, yields capture cost around 16 €/ton CO2 avoided and incremental cost of electricity of just over 1 €/MW h e.Peer reviewe