31 research outputs found
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
Experimental and Simulation Study of Adsorption in Postcombustion Conditions Using a Microporous Biochar. 1. CO2 and N2 Adsorption
The influence of N2 on CO2 adsorption was evaluated using a microporous biochar with a narrow pore size distribution. The adsorption isotherms of pure CO2 and N2 were measured at 0, 30, 50, and 70 °C up to 120 kPa and fitted to the Toth adsorption model. Dynamic breakthrough experiments were carried out in a fixed-bed adsorption unit using binary mixtures with compositions representative of different postcombustion streams (8–30% CO2) from ambient temperature to 70 °C. Dynamic adsorption experiments were simulated to validate the mathematical model of the adsorption process, as a necessary step for its later use for process design. The Ideal Adsorption Solution (IAS) theory, based on the pure component adsorption models, was used to account for competitive adsorption with satisfactory results. The information gathered in the present work will be used to extend the validity of the model to the adsorption of postcombustion streams containing H2O in part 2.Work was carried out with financial support from the HiPerCap
Project of the European Union 7th Framework Programme
FP7 (2007-2013; Grant Agreement number: 60855). M.G.P.
acknowledges funding from the CSIC (JAE-Doc program
cofinanced by the European Social Fund). N.Q. acknowledges
funding from the Government of the Principado de Asturias
(Severo Ochoa Program). The authors also appreciate the
support from the technical consultants of AspenTechnology
Inc., M.M. and E.L.Peer reviewe
Efecto del vapor de agua en la adsorción de CO2 postcombustión
Tesis realizada en la Universidad de OviedoNausika Querejeta Montes, autora de la tesis, habla sobre el objetivo y desarrollo de la investigación y las conclusiones de la mism
Efecto del vapor de agua en la adsorción de CO2 postcombustión
Tesis con mención internacional. Tesis doctoral por el sistema de compendio de publicacionesLas consecuencias del cambio climático ya son perceptibles. Aunque las emisiones de gases de efecto invernadero se redujesen notablemente, el calentamiento de la Tierra continuarÃa durante décadas y sus efectos se sufrirÃan durante los siglos venideros. Por este motivo, la comunidad internacional ha adquirido el compromiso de alcanzar la neutralidad de emisiones de carbono entre 2050-2100. Esta situación requerirá contar con todas las tecnologÃas de mitigación disponibles en el periodo de transición. Una de las principales formas de mitigar las emisiones de COâ‚‚ de grandes fuentes estacionarias son las tecnologÃas de captura y almacenamiento de carbono. De ahà que en los últimos años se haya dedicado un esfuerzo investigador considerable a su desarrollo. Entre el amplio abanico de procesos capaces de captar COâ‚‚, la presente Tesis Doctoral se centra en la adsorción. Durante la última década se ha intensificado la búsqueda de materiales adsorbentes con un alto rendimiento en la separación de COâ‚‚, asà como un coste bajo, especialmente si su aplicación es en procesos de captura de COâ‚‚ postcombustión. En este contexto, es fundamental el estudio de su comportamiento bajo condiciones de humedad y en presencia de otras impurezas en la corriente gaseosa, condiciones representativas de las reales en el ámbito industrial. Estas circunstancias han motivado la presente Tesis Doctoral, en la cual se ha evaluado el efecto del vapor de agua en la captura de COâ‚‚ postcombustión. El objetivo principal de esta Tesis Doctoral ha sido estudiar el rendimiento de carbones activados biomásicos para la adsorción de COâ‚‚, en condiciones de postcombustión donde la humedad es muy significativa. Para ello, se han preparado y optimizado estos carbones aplicando diferentes metodologÃas, para incrementar su selectividad hacia el COâ‚‚ en presencia de humedad, asà como maximizar su capacidad de captación de COâ‚‚ en estas condiciones. La capacidad de adsorción de COâ‚‚ de los carbones activados en condiciones de postcombustión reside en su microporosidad; sin embargo, la captación de COâ‚‚ se ve disminuida en atmósferas húmedas debido a la co-adsorción de agua. Este aspecto ha sido evaluado en la presente memoria de Tesis Doctoral, donde se ha investigado sobre la adsorción de vapor de agua en carbones activados biomásicos y las posibles estrategias para reducirla actuando, fundamentalmente, sobre la quÃmica superficial. Todos los post-tratamientos evaluados redujeron la adsorción de vapor de agua a bajas presiones, pero solamente la impregnación con aminas es efectiva en condiciones próximas a la saturación. AsÃmismo, se han desarrollado diferentes procedimientos experimentales, que incluyen una combinación única de diseño de experimentos mediante la MetodologÃa de Superficies de Respuesta y diversos métodos de modelización, para optimizar la producción de los carbones biomásicos y maximizar su capacidad de captación de COâ‚‚ en presencia de humedad. Mediante el análisis del comportamiento termodinámico en el equilibrio (isotermas de adsorción) y del comportamiento dinámico de lechos de adsorbente (curvas de ruptura y ciclos de sorción-desorción) se presenta una visión completa de la potencialidad de los carbones activados biomásicos para la captura de COâ‚‚ en condiciones de postcombustión. Se ha optimizado y mejorado el comportamiento en captura de COâ‚‚ postcombustión de un carbón activado, preparado a partir de residuos de café postconsumo, mediante tratamiento hidrotermal y posterior activación. Los resultados obtenidos suponen un avance respecto a la patente ES2526259. Por otro lado, en condiciones de humedad relativa constante del 20%, el lecho de carbón activado biomásico producido mediante impregnación con carbonato potásico, alcanzó una capacidad de captura de COâ‚‚ de 2 mmol g-1 a 50 ºC y 14 kPa de COâ‚‚. Este resultado se complementa con una excepcional capacidad en términos volumétricos. The consequences of climate change are already noticeable. Even if greenhouse gas emissions were significantly reduced, global warming would continue over the coming decades and the effects would ever be perceptible in the centuries to come. For this reason, the international community is committed to achieving carbon neutrality between 2050-2100. This critical situation will require the deployment of all available technologies during this transition period. One of the main paths towards mitigating COâ‚‚ emissions from large point stationary sources is through the application of carbon capture and storage technologies. In recent years, considerable research effort has been devoted to this aim. Among the wide variety of processes able to capture COâ‚‚, is adsorption, the subject of this PhD dissertation. Over the last decade, research on new low cost adsorbent materials with a high COâ‚‚ capture performance, particularly in postcombustion capture applications, has been very intensive. Within this context, it is of the utmost importance to evaluate the performance of the adsorbents under humid conditions and in the presence of other pollutants in the gas stream so as to assess conditions representative of real industrial applications. It was the circumstances just described that motivated the research into the effect of water vapour on postcombustion COâ‚‚ capture as part of the present PhD thesis. The main objective of the PhD thesis has been to address the performance of biomass-based COâ‚‚ adsorbents in postcombustion capture conditions where the level of humidity is very high. A set of carbons has been produced and optimised by means of different methodologies so as to enhance the selectivity towards COâ‚‚ in the presence of water as well as to maximise COâ‚‚ uptake under these conditions. The ability of an activated carbon to adsorb COâ‚‚ under postcombustion capture conditions is ascribed to its microporosity. However, COâ‚‚ uptake is reduced in humid environments due to the coadsorption of water vapour. The present PhD dissertation, addresses this issue directly, focusing on the adsorption of water vapour on biomass-based activated carbons and on the strategies available for reducing water uptake by means of surface chemistry modification. It was found that all of the evaluated post-treatments reduced water uptake at low pressures to some extent but only amine impregnation succeeded under conditions close to saturation. Likewise, the production of biomass-based activated carbons has been optimised and their potential for COâ‚‚ adsorption under humid conditions maximised by combining different experimental procedures including the design of experiments by means of Response Surface Methodology and modelling methods. Analysis of the equilibrium of adsorption by means of isotherms together with the dynamic performance of beds of adsorbent by means of breakthrough curves and sorption-desorption cycles provided data needed in support of the great potential of biomass adsorbents such as those produced in this study to capture COâ‚‚ under postcombustion conditions. The COâ‚‚ capture performance of coffee-based activated carbons was optimised and enhanced by means of hydrothermal carbonisation followed by activation in COâ‚‚ atmosphere. The results achieved are more far-reaching than those reported in the patent ES2526259. On the other hand, under a constant relative humidity of 20%, a bed of a biomass carbon doped with potassium carbonate achieved a COâ‚‚ uptake of up to 2 mmol g-1 at 50 ºC and 14 kPa COâ‚‚. This result was accompanied by an outstanding volumetric COâ‚‚ uptake
Effect of water vapour on postcombustion CO2 adsorption
Tesis doctoral presentada en el Departamento de EnergÃa de la Universidad de Oviedo, 2019.[EN] The consequences of climate change are already noticeable. Even if greenhouse gas emissions were significantly reduced, global warming would continue over the coming decades and the effects would ever be perceptible in the centuries to come. For this reason, the international community is committed to achieving carbon neutrality between 2050-2100. This critical situation will require the deployment of all available technologies during this transition period.
One of the main paths towards mitigating COâ‚‚ emissions from large point stationary sources is through the application of carbon capture and storage technologies. In recent years, considerable research effort has been devoted to this aim. Among the wide variety of processes able to capture COâ‚‚, is adsorption, the subject of this PhD dissertation. Over the last decade, research on new low cost adsorbent materials with a high COâ‚‚ capture performance, particularly in postcombustion capture applications, has been very intensive. Within this context, it is of the utmost importance to evaluate the performance of the adsorbents under humid conditions and in the presence of other pollutants in the gas stream so as to assess conditions representative of real industrial applications. It was the circumstances just described that motivated the research into the effect of water vapour on postcombustion COâ‚‚ capture as part of the present PhD thesis.The main objective of the PhD thesis has been to address the performance of biomass-based COâ‚‚ adsorbents in postcombustion capture conditions where the level of humidity is very high. A set of carbons has been produced and optimised by means of different methodologies so as to enhance the selectivity towards COâ‚‚ in the presence of water as well as to maximise COâ‚‚ uptake under these conditions.The ability of an activated carbon to adsorb COâ‚‚ under postcombustion capture conditions is ascribed to its microporosity. However, COâ‚‚ uptake is reduced in humid environments due to the coadsorption of water vapour. The present PhD dissertation, addresses this issue directly, focusing on the adsorption of water vapour on biomass-based activated carbons and on the strategies available for reducing water uptake by means of surface chemistry modification. It was found that all of the evaluated post-treatments reduced water uptake at low pressures to some extent but only amine impregnation succeeded under conditions close to saturation.
Likewise, the production of biomass-based activated carbons has been optimised and their potential for COâ‚‚ adsorption under humid conditions maximised by combining different experimental procedures including the design of experiments by means of Response Surface Methodology and modelling methods. Analysis of the equilibrium of adsorption by means of isotherms together with the dynamic performance of beds of adsorbent by means of breakthrough curves and sorption-desorption cycles provided data needed in support of the great potential of biomass adsorbents such as those produced in this study to capture COâ‚‚ under postcombustion conditions.
The COâ‚‚ capture performance of coffee-based activated carbons was optimised and enhanced by means of hydrothermal carbonisation followed by activation in COâ‚‚ atmosphere. The results achieved are more far-reaching than those reported in the patent ES2526259. On the other hand, under a constant relative humidity of 20%, a bed of a biomass carbon doped with potassium carbonate achieved a COâ‚‚ uptake of up to 2 mmol g-1 at 50 ºC and 14 kPa COâ‚‚. This result was accompanied by an outstanding volumetric COâ‚‚ uptake.[ES] Las consecuencias del cambio climático ya son perceptibles. Aunque las emisiones de gases de efecto invernadero se redujesen notablemente, el calentamiento de la Tierra continuarÃa durante décadas y sus efectos se sufrirÃan durante los siglos venideros. Por este motivo, la comunidad internacional ha adquirido el compromiso de alcanzar la neutralidad de emisiones de carbono entre 2050-2100. Esta situación requerirá contar con todas las tecnologÃas de mitigación disponibles en el periodo de transición.
Una de las principales formas de mitigar las emisiones de COâ‚‚ de grandes fuentes estacionarias son las tecnologÃas de captura y almacenamiento de carbono. De ahà que en los últimos años se haya dedicado un esfuerzo investigador considerable a su desarrollo. Entre el amplio abanico de procesos capaces de captar COâ‚‚, la presente Tesis Doctoral se centra en la adsorción. Durante la última década se ha intensificado la búsqueda de materiales adsorbentes con un alto rendimiento en la separación de COâ‚‚, asà como un coste bajo, especialmente si su aplicación es en procesos de captura de COâ‚‚ postcombustión. En este contexto, es fundamental el estudio de su comportamiento bajo condiciones de humedad y en presencia de otras impurezas en la corriente gaseosa, condiciones representativas de las reales en el ámbito industrial. Estas circunstancias han motivado la presente Tesis Doctoral, en la cual se ha evaluado el efecto del vapor de agua en la captura de COâ‚‚ postcombustión.
El objetivo principal de esta Tesis Doctoral ha sido estudiar el rendimiento de carbones activados biomásicos para la adsorción de COâ‚‚, en condiciones de postcombustión donde la humedad es muy significativa. Para ello, se han preparado y optimizado estos carbones aplicando diferentes metodologÃas, para incrementar su selectividad hacia el COâ‚‚ en presencia de humedad, asà como maximizar su capacidad de captación de COâ‚‚ en estas condiciones.La capacidad de adsorción de COâ‚‚ de los carbones activados en condiciones de postcombustión reside en su microporosidad; sin embargo, la captación de COâ‚‚ se ve disminuida en atmósferas húmedas debido a la co-adsorción de agua. Este aspecto ha sido evaluado en la presente memoria de Tesis Doctoral, donde se ha investigado sobre la adsorción de vapor de agua en carbones activados biomásicos y las posibles estrategias para reducirla actuando, fundamentalmente, sobre la quÃmica superficial. Todos los post-tratamientos evaluados redujeron la adsorción de vapor de agua a bajas presiones, pero solamente la impregnación con aminas es efectiva en condiciones próximas a la saturación.
AsÃmismo, se han desarrollado diferentes procedimientos experimentales, que incluyen una combinación única de diseño de experimentos mediante la MetodologÃa de Superficies de Respuesta y diversos métodos de modelización, para optimizar la producción de los carbones biomásicos y maximizar su capacidad de captación de COâ‚‚ en presencia de humedad. Mediante el análisis del comportamiento termodinámico en el equilibrio (isotermas de adsorción) y del comportamiento dinámico de lechos de adsorbente (curvas de ruptura y ciclos de sorción-desorción) se presenta una visión completa de la potencialidad de los carbones activados biomásicos para la captura de COâ‚‚ en condiciones de postcombustión.
Se ha optimizado y mejorado el comportamiento en captura de CO₂ postcombustión de un carbón activado, preparado a partir de residuos de café postconsumo, mediante tratamiento hidrotermal y posterior activación. Los resultados obtenidos suponen un avance respecto a la patente ES2526259. Por otro lado, en condiciones de humedad relativa constante del 20%, el lecho de carbón activado biomásico producido mediante impregnación con carbonato potásico, alcanzó una capacidad de captura de CO₂ de 2 mmol g-1 a 50 ºC y 14 kPa de CO₂. Este resultado se complementa con una excepcional capacidad en términos volumétricos.Peer reviewe
Enhanced capacity to CO2 sorption in humid conditions with a K-doped biocarbon
Solid sorbents with enhanced capacity and selectivity towards CO2 are crucial in the design of an efficient capture process. Among the possible alternatives, K2CO3-doped activated carbons have shown high CO2 capture capacity and rapid carbonation reaction rate. In this work, a sustainable and low-cost approach is developed with a biomass-based activated carbon or biocarbon as support. The CO2 capture performance in cyclic sorption–desorption operation and the sorption kinetics have been investigated under different scenarios in a purpose-built fixed-bed set-up. Independent of the H2O concentration in the flue gas, a constant relative humidity (∼20%) in the K2CO3-doped biocarbon bed promoted the carbonation reaction and boosted the CO2 sorption capacity (1.92 mmol/g at 50 °C and 14 kPa partial pressure of CO2). Carbonation is slower than physical adsorption of CO2 but wise process design could tune the operation conditions and balance capture capacity and sorption kinetics.Peer reviewe