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

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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

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

Dynamic performance of biomass based carbons for CO2/CH4 separation. Approximation to a PSA process for biogas upgrading

Physical adsorption-based processes such as pressure swing adsorption (PSA) constitute an alternative to selectively adsorb CO2 from biogas streams. There is abundant work regarding the equilibrium of adsorption of pure CH4 and CO2 on different adsorbents. However, to design an adsorption process with a selected adsorbent it is very important to account for its dynamic behavior in a packed-bed. Thus, the performance of two biomass-based activated carbons (CS-CO2 and CS-H2O) previously prepared in our laboratory to separate CO2/CH4 has been evaluated. Full adsorption–desorption cycles were conducted at 30 °C (isothermal conditions) and different pressures (1, 3, 5, and 10 bar) feeding binary CO2/CH4 (50/50 vol %) mixtures to a purpose-built fixed-bed setup. A commercial activated carbon, Calgon BPL, was also evaluated for reference purposes. CO2 equilibrium uptakes were obtained from dynamic breakthrough curves and proved to be maximum at 10 bar (5.14, 4.48, and 4.14 mol kg–1 for CS-CO2, CS-H2O, and Calgon BPL, respectively). However, the CO2/CH4 separation efficiency, according to the difference in breakthrough times between CH4 and CO2, is very limited at 10 bar. A combined analysis of the productivity and purity of CH4 along with CO2 working capacity derived from dynamic experiments indicates that our biomass-based activated carbons would be better candidate materials for the CO2/CH4 separation at a pressure of 5 bar than the commercial activated carbon Calgon BPL.This work has received financial support from the Spanish MINECO (Project ENE2011-23467), 437 co-financed by the European Regional Development Fund (ERDF), and from the Gobierno del 438 Principado de Asturias (PCTI2013-2017, GRUPIN14-079).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

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