Progress in pilot, large-scale projects as an inducement for CCUS deployment

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Grindability and combustion behavior of coal and torrefied biomass blends

Biomass samples (pine, black poplar and chestnut woodchips) were torrefied to improve their grindability before being combusted in blends with coal. Torrefaction temperatures between 240 and 300 °C and residence times between 11 and 43 min were studied. The grindability of the torrefied biomass, evaluated from the particle size distribution of the ground sample, significantly improved compared to raw biomass. Higher temperatures increased the proportion of smaller-sized particles after grinding. Torrefied chestnut woodchips (280 °C, 22 min) showed the best grinding properties. This sample was blended with coal (5–55 wt.% biomass). The addition of torrefied biomass to coal up to 15 wt.% did not significantly increase the proportion of large-sized particles after grinding. No relevant differences in the burnout value were detected between the coal and coal/torrefied biomass blends due to the high reactivity of the coal. NO and SO2 emissions decreased as the percentage of torrefied biomass in the blend with coal increased.This work was part of the subcontracted contribution of INCAR to a project carried out by EDP Spain with the financial support from the European Regional Development Fund (ERDF) and acting IDEPA (Economic Development Agency of the Principality of Asturias) as research funding agency (Ref.: IDE/2013/000233). The authors thank A. J. Martín, member of the PrEM group at INCAR-CSIC, for his contribution.Peer reviewe

Green coffee based CO2 adsorbent with high performance in postcombustion conditions

An environmentally friendly and low cost adsorbent, PPC (patent application filed González (2013)), produced from an abundant residue from the food industry, coffee grounds, is presented and evaluated as CO2 adsorbent in postcombustion conditions. PPC is a high bulk density pelletized carbon with adequate properties for its use in fixed-bed adsorption applications. The equilibrium capacity for CO2 at low partial pressures, relevant for the postcombustion case, in the 25–50 °C temperature range is superior to that of reference carbons, both in mass and volume basis. PPC presents equilibrium selectivity for CO2 over N2, with CO2/N2 equilibrium separation factor values of 15–25 at 50 °C and 130 kPa for CO2 concentrations between 9% and 31%. Moreover, it presents fast adsorption kinetics, which makes it a good candidate for rapid swing adsorption cycles. Different VSA cycle configurations were carried out at 50 °C in the fixed-bed adsorption unit to evaluate the performance of the adsorbent in cyclic operation. The adsorbent did not show any sign of deactivation over extended operation.Work carried out with financial support from the Spanish MINECO (Project ENE2011-23467), co-financed by the European Regional Development Fund (ERDF). M.G.P. acknowledges funding from the CSIC (JAE-Doc program), and A.S.G. acknowledges a contract from the MINECO (FPI program); both programs are co-financed by the European Social Fund.Peer reviewe

Procedimiento de obtención de un adsorbente que utiliza residuos de café postconsumo y su utilización para la adsorción de CO2

La presente invención se refiere a un procedimiento de obtención de un material adsorbente con capacidad para adsorber CO2 , que utiliza residuos de café postconsumo. El procedimiento de obtención comprende el secado del residuo, su conformación, en ausencia de ligantes, y su activación térmica en presencia de un agente activante, que preferentemente es CO2 . Las características texturales y de densidad del material obtenido por el procedimiento de la invención, que también se protege, lo convierten en un candidato ideal para la adsorción de CO2 , y preferentemente en la captura de CO2 postcombustión.Peer reviewedConsejo Superior de Investigaciones CientíficasR Informe sobre el estado de la técnica publicado separadament

CO2 adsorbent pellets produced from pine sawdust: Effect of coal tar pitch addition

The main drawbacks of developing carbon adsorbents from pine sawdust, an abundant biomass feedstock, are the low carbon yield of the process and the poor mechanical properties of the resulting carbons. In an attempt to overcome these limitations, the effect of the addition of coal tar pitch was assessed. Adsorbent pellets were produced from pine sawdust and coal tar pitch by activation with CO2. The preparation process was optimized by using as decision variables the carbon yield and the adsorption performance of the adsorbents in conditions representative of post-combustion capture applications (10% CO2 at atmospheric pressure and at 50 °C). Subjecting the composite pellets to a pre-oxidation treatment with air increased the carbon yield of the production process, and also improved the adsorption kinetics and capacity of the final adsorbents. The prepared adsorbents present a high carbon yield, a superior mechanical resistance and a competitive adsorption performance.This work was carried out with financial support from the Spanish MINECO (Project ENE2011-23467), co-financed by the European Regional Development Fund (ERDF). M.G.P. acknowledges funding from the CSIC (JAE-Doc program), co-financed by the European Social Fund, and I.D. acknowledges funding from the Government of the Principado de Asturias. The authors are grateful to Industrial Química del Nalón S.A. for supplying the coal tar pitch sample.Peer reviewe

Kinetics of CO2 adsorption on cherry stone-based carbons in CO2/CH4 separations

Most practical applications of solids in industry involve porous materials and adsorption processes. A correct assessment of the equilibrium and kinetics of adsorption is extremely important for the design and operation of adsorption based processes. In our previous studies we focused on the evaluation of the equilibrium of CO2/CH4 adsorption on cherry stone-based carbons. In the present paper the kinetics of adsorption of CO2 on two cherry stone-based activated carbons (CS-H2O and CS-CO2), previously prepared in our laboratory, has been evaluated by means of transient breakthrough experiments at different CO2/CH4 feed concentrations, at atmospheric pressure and 30 °C. A commercial activated carbon, Calgon BPL, has also been evaluated for reference purposes. Three models have been applied to estimate the rate parameters during the adsorption of CO2 on these carbons, pseudo-first, pseudo-second and Avrami´s fractional order kinetic models. Avrami´s model accurately predicted the dynamic CO2 adsorption performance of the carbons for the different feed gas compositions. To further investigate the mechanism of CO2 adsorption on CS-H2O, CSCO2 and Calgon BPL, intra-particle diffusion and Boyd´s film-diffusion models were also evaluated. It was established that mass transfer during the adsorption of CO2 from CO2/CH4 is a diffusion-based process and that the main diffusion mechanisms involved are intra-particle and film diffusion. At the initial stages of adsorption, film diffusion resistance governed the adsorption rate, whereas intra-particle diffusion resistance was the predominant factor in the following stages of adsorption.This work has received financial support from the Spanish MINECO (Project ENE2011-23467), co-financed by the European Regional Development Fund (ERDF), and from the Gobierno del Principado de Asturias (PCTI 2013-2017 GRUPIN14-079). N.A-G. also acknowledges a fellowship awarded by the Spanish MINECO (FPI program), and co-financed by the European Social Fund.Peer reviewe

Experimental and Simulation Study of Adsorption in Postcombustion Conditions Using a Microporous Biochar. 2. H2O, CO2, and N2 Adsorption

The adsorption behavior of humid mixtures that are representative of postcombustion conditions on a microporous biochar was evaluated. The adsorption isotherms of H2O(v) were measured at 30, 50, and 70 °C up to the saturation pressure and fitted to the extended Cooperative Multimolecular Sorption (CMMS) model. Dynamic experiments were carried out in a fixed-bed adsorption unit with mixtures of N2, CO2, and H2O(v). Experimental results indicate that H2O is little affected by CO2 adsorption. On the other hand, the CO2 adsorption capacity can be reduced by the adsorption of H2O. The extent of this reduction is dependent on the amount of H2O adsorbed, which, in turn, is strongly dependent on the relative humidity of the gas phase and the adsorption time. A dynamic fixed-bed adsorption model that makes use of Ideal Adsorbed Solution (IAS) theory has been shown to be adequate to describe the adsorption behavior of CO2 from the ternary mixtures in the full range of conditions evaluated.Work carried out with financial support from the HiPerCap Project of the European Union 7th Framework Programme (FP7) (2007-2013; Grant Agreement No. 60855).Peer reviewe

Comparison between the reactivity of coal and synthetic coal models

A mixture of carbon compounds was pyrolysed under an inert atmosphere at different temperatures in a fixed bed reactor. The resultant chars were characterised in terms of texture and thermal behaviour. Textural characterisation of the chars was carried out by N2 and CO2 adsorption isotherms at −196 and 0 °C, respectively. Char isothermal reactivity in air at 500 °C, and in CO2 at 1000 °C, was performed in a thermogravimetric analyser (TGA). Temperature-programmed combustion tests under 20% oxygen in argon were also performed in the TGA linked to a mass spectrometer (TGA/MS). The results showed that char textural properties do not always relate well to their reactivity. Not only do physical properties (e.g. surface area, porosity) but also chemical properties (e.g. active sites concentration and distribution) play an important role in the reaction of carbonaceous material and oxidant. On the other hand, in terms of chemical composition the chars obtained from the mixture of carbon compounds were very similar to the chars produced under the same experimental conditions by a high volatile bituminous coal. The fact that carbon compounds are well known makes it easier to obtain knowledge about the functional groups present in synthetic char, and to study the mechanisms of heterogeneous reactions such as the reduction of NO with carbon.Peer reviewe

Production of fuel-cell grade H2 by sorption enhanced steam reforming of acetic acid as a model compound of biomass-derived bio-oil

Fuel-cell grade H2 has been produced by the sorption enhanced steam reforming (SESR) of acetic acid, a model compound of the bio-oil obtained from the fast pyrolysis of biomass. A Pd/Ni–Co catalyst derived from a hydrotalcite-like material (HT) with dolomite as CO2 sorbent was used in the process. A fixed-bed reactor with three temperature zones was employed to favor the catalytic steam reforming reaction in the high-temperature segment, the SESR reaction in the intermediate-temperature part, as well as the water-gas shift (WGS) and CO2 capture reactions in the low-temperature segment. Different conditions of pressure, temperature, steam/C molar ratio and weight hourly space velocity (WHSV) in the feed were evaluated. Higher steam/C molar ratios and lower WHSV values facilitated the production of H2 and reduced the concentrations of CH4, CO and CO2 in the produced gas. A fuel-cell grade H2 stream with a H2 purity of 99.8 vol.% and H2 yield of 86.7% was produced at atmospheric pressure, with a steam/C ratio of 3, a WHSV of 0.893 h−1 and a temperature of 575 °C in the intermediate part of the reactor (675 °C in the upper segment and 425 °C in the bottom part). At high pressure conditions (15 atm) a maximum H2 concentration of 98.31 vol.% with a H2 yield of 79.81% was obtained at 725 °C in the intermediate segment of the reactor (825 °C in the upper segment and 575 °C in the bottom part). Under these conditions an effluent stream with a CO concentration below 10 ppm (detection limit) was obtained at both low and high pressure, making it suitable for direct use in fuel cell applications.This work was carried out with financial support from the Spanish MINECO (Project ENE2014-53515-P), co-financed by the European Regional Development Fund (ERDF) and the Principado de Asturias (PCTI 2013-2017, GRUPIN14-079)Peer reviewe