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

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

Diseño de procesos cíclicos de adsorción para captura de CO2 en el contexto de una planta de gestión de residuos

Tesis realizada en la Universidad de OviedoInés Durán Vera, autora de la tesis, habla sobre el objetivo de la tesis, el serrín de pino y microalgas, la activación física, el modelo matemático desarrollado y la aplicación de la tecnologí

Separation of CO2 in a Solid Waste Management Incineration Facility Using Activated Carbon Derived from Pine Sawdust

The selective separation of CO2 from gas mixtures representative of flue gas generated in waste incineration systems is studied on two activated carbons obtained from pine sawdust and compared to a commercial activated carbon. Dynamic adsorption experiments were conducted in a fixed-bed adsorption column using a binary mixture (N2/CO2) with a composition representative of incineration streams at temperatures from 30 to 70 °C. The adsorption behavior of humid mixtures (N2/CO2/H2O) was also evaluated in order to assess the influence of water vapor in CO2 adsorption at different relative humidity in the feed gas: 22% and 60%. Moreover, CO2 adsorption was studied in less favorable conditions, i.e., departing from a bed initially saturated with H2O. In addition, the effect of CO2 on H2O adsorption was examined. Experimental results showed that the CO2 adsorption capacity can be reduced significantly by the adsorption of H2O (up to 60% at high relative humidity conditions). On the other hand, the breakthrough tests over the adsorbent initially saturated with water vapor indicated that H2O is little affected by CO2 adsorption. The experimental results pointed out the biomass based carbons as best candidates for CO2 separation under incineration flue gas conditions.This work has received financial support from the Spanish MINECO (Retos-Colaboración RTC-2014-2109-5) and from the Gobierno del Principado de Asturias (PCTI-GRUPIN14-079).We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI).Peer reviewe

Microalgae: Potential precursors of CO2 adsorbents

With faster growth rates and higher photosynthetic efficiencies than other terrestrial plants, microalgae biomass could be considered as a green, low-cost, alternative carbon source. This paper explores the potential use of various species of microalgae as activated carbon precursors. Chlorella and Spirulina were evaluated both as freeze-dried microalgae and in fresh paste form, while Acutodesmus Obliquus and Coelastrella sp. were studied only as paste. Activated carbons were produced using the selected species of microalgae as well as mixtures of pine sawdust and microalgae. Two different preparation routes were compared: with and without hydrothermal carbonization pretreatment before physical activation with CO2 in a single step. All samples were conformed into pellets prior to CO2 activation. The CO2 adsorption capacity of the microalgae derived carbons was assessed in conditions representative of a flue gas (10.5 vol.% CO2 at atmospheric pressure and 50 °C). Significant differences in terms of CO2 adsorption capacity, carbon yield and pellet density were obtained among the species studied. These preliminary results showed that activated carbons produced from microalgae mixed with pine sawdust and directly activated with CO2 are among the most promising adsorbents to capture CO2 from flue gas.This work has received financial support from the Spanish MINECO (RTC-2014-2109-5) and from the Gobierno del Principado de Asturias (PCTI 2013-2017 GRUPIN14-079).Peer reviewe

Vacuum swing CO2 adsorption cycles in Waste-to-Energy plants

The performance of vacuum swing adsorption-based processes applied to CO2 capture in Waste-to-Energy plants is explored for the first time. CO2 capture and storage (CCS) are gaining increasing attention in this sector. The analysis of simple cycle configurations for this particular application provides a reference scenario to explore the potentiality of the adsorption technology. Under these premises, the objective of this study is to maximize the CO2 separation from the flue gas of a solid waste incineration facility. Three vacuum swing adsorption (VSA) and one vacuum and temperature swing adsorption (VTSA) configurations were assessed in a fixed-bed laboratory unit and the influence of the cycle design, the number of columns and the operational conditions were analyzed. The adsorbent employed is an activated carbon produced from pine sawdust, a forestry by-product with great availability in our region. Mathematical modeling developed in Aspen Adsorption complemented the experimental study which in turn validated the created model. Additional simulations were performed to further evaluate the effect that the different vacuum swing adsorption configurations have on product purity and recovery. With relatively simple configurations consisting of a maximum of 4-beds, CO2 recoveries above 95% were achieved and CO2 purity was increased from 8% to approximately 35–40%.This work has received financial support from the Gobierno del Principado de Asturias, Spain (PCTI, Ref. IDI/2018/000115) with co-funding from the European Regional Development Fund (ERDF).Peer reviewe