12 research outputs found
Kinetic approach to modelling CO<sub>2</sub> adsorption from humid air using amine-functionalized resin:Equilibrium isotherms and column dynamics
Improving adsorption-based direct air capture performance through operating parameter optimization
Direct air capture (DAC) of CO2 through adsorption is a promising technology for mitigating climate change, but its high cost presents a significant challenge to large-scale implementation. To address this issue, this study presents a dynamic fixed-bed model of the closed-inlet temperature-vacuum swing adsorption (TVSA) process and investigates the impact of various operating and model parameters on DAC performance via dynamic simulation. The results indicate that optimizing the durations of the adsorption and regeneration phases is crucial for improving cyclic DAC performance. Maximizing the working capacity by driving both phases towards near-equilibrium conditions generally leads to the lowest specific energy requirement (SER), while cutting the adsorption phase earlier increases the CO2 productivity. Additionally, appropriate choices of operating parameters, such as feed gas velocity and vacuum pressure, can significantly improve DAC process performance. Furthermore, placing the DAC unit in a location with favourable temperature and humidity conditions, affordable heat source, and elevated CO2 concentration can greatly enhance the process and its cost-effectiveness. These individual approaches have the potential to multiply productivity and decrease SER by increasing the working capacity, shortening the cycle duration, and minimizing the absolute energy consumption. However, optimizing the DAC process necessitates careful consideration of trade-offs between productivity, SER, and various constraints. These insights, along with the developed model, can provide a valuable basis for further advancement of DAC technology
Cin茅ticas de captura de CO2 del aire basadas en adsorci贸n
Los adsorbentes s贸lidos son actualmente empleados en la captura de CO2 atmosf茅rico por adsorci贸n directa (DAC). Para poder predecir y modelar el comportamiento de adsorci贸n es necesario caracterizar las cin茅ticas de adsorci贸n de CO2 en los materiales adsorbentes. El objetico de este TFM es estudiar los diferentes modelos cin茅ticos de adsorci贸n de CO2 presentes en bibliograf铆a y utilizar la informaci贸n recopilada para proponer un modelo capaz de predecir la cin茅tica de adsorci贸n de CO2 en una resina am铆nica comercial. A ello se suma el objetivo de validar los modelos cin茅ticos de adsorci贸n seleccionados, teniendo en consideraci贸n los resultados de los ensayos de adsorci贸n obtenidos por termogravimetr铆a anal铆tica (TGA) y por columna de adsorci贸n de lecho fijo. Adem谩s, los resultados experimentales de adsorci贸n hallados en este TFM ser谩n comparados con la isoterma de adsorci贸n de la resina am铆nica. Adicionalmente, en el prop贸sito de este trabajo se incluye comparar los resultados cin茅ticos de adsorci贸n cosechados por TGA y la columna de adsorci贸n. Finalmente, el inter茅s de dos zeolitas comerciales como adsorbentes de CO2 para DAC ser谩 estudiado para las condiciones de trabajo ensayadas. Las zeolitas a estudiar son la zeolita 4 脜 y zeolita 13 X.En base a la bibliograf铆a consultada, los modelos de ajuste seleccionados para la adsorci贸n de CO2 en la resina am铆nica est谩n basados en la aproximaci贸n de la fuerza impulsora lineal, Linear Driving Force (LDF). Los modelos de ajuste fueron: pseudo primer orden (LDF1), pseudo segundo orden (LDF2), Avrami y las aproximaciones de Veneman. Tambi茅n se estudiaron dos modelos anal铆ticos, referidos en este TFM como modelos te贸ricos; los cuales tambi茅n se basan en la aproximaci贸n LDF. Los modelos te贸ricos seleccionados son el mecanismo descrito por Farooq & Ruthven y el hallado en el manual de ingenier铆a qu铆mica de Perry et al. (1999).De acuerdo con los resultados obtenidos, el modelo propuesto por Veneman y el LDF1 presentaron un buen ajuste a la curva de adsorci贸n de CO2 experimental en la resina am铆nica. Dichos modelos producen una constante cin茅tica global aparente capaz de simular los resultados de los mismos experimentos llevados a cabo en el equipo para unas condiciones y par谩metros de trabajo iguales a las del ajuste. No obstante, el modelo de Farooq & Ruthven demostr贸 ser capaz de aportar una buena predicci贸n del comportamiento experimental y una mayor utilidad, al proporcionar un m茅todo para calcular la constante cin茅tica global de adsorci贸n para distintas condiciones experimentales. El modelo de Farooq & Ruthven cuantifica las contribuciones de los par谩metros de dise帽o del equipo, condiciones experimentales y propiedades del s贸lido. De tal forma que el modelo de Farooq & Ruthven puede ser utilizado para el escalado de equipos y predecir nuevos comportamientos del sistema ante variaciones en las condiciones del proceso de adsorci贸n.Los resultados de adsorci贸n de CO2 en la resina am铆nica demostraron que la etapa limitante del proceso de adsorci贸n es distinta en los equipos de TGA y en la columna de adsorci贸n estudiados. No obstante, la capacidad de adsorci贸n en el equilibrio de la resina am铆nica es la misma independientemente del equipo de adsorci贸n seleccionado. Las variaciones en los coeficientes de difusi贸n del CO2 en la resina am铆nica entre equipos se tradujeron en una adsorci贸n diez veces m谩s lenta para la TGA respecto al lecho fijo y en una constante cin茅tica global distinta para cada equipo. Las zeolitas estudiadas mostraron capacidad de adsorci贸n de CO2 para las condiciones de adsorci贸n. No obstante, los experimentos de desorci贸n hallaron que 100潞C no era una temperatura suficiente para regenerar las zeolitas; perdiendo capacidad de adsorci贸n tras pocos ciclos de adsorci贸n-desorci贸n. Las condiciones empleadas en los experimentos de adsorci贸n para todos los adsorbentes en ambos equipos fueron de 400 ppm de CO2 a 25潞 C y 1.1 bar de presi贸n total.English version:Adsorbents are applied in direct air capture (DAC) technologies to extract CO2 from the atmospheric air. Kinetics of adsorption are required to model and predict the behaviour of the adsorbent material in the adsorption process. The objective of the thesis is to study the different CO2 adsorption kinetic models presented in literature, and to use the information to create a model to predict the CO2 kinetic adsorption of a commercial amine-resin adsorbent. In addition, the objective is to validate the selected models with experimental adsorption results from thermal gravimetric analysis (TGA), fixed-bed adsorption and the amine-resin adsorption isotherm. Furthermore, the aim of the thesis is to compare the results of adsorption capacity and the adsorption kinetics obtained from TGA and the fixed-bed. Lastly, feasibility of two commercial zeolites, Zeolite 4脜 as Zeolite 13X, as CO2 adsorbents are tested.Based on the literature survey, the selected models for CO2 adsorption were based on the Linear Driving Force (LDF) adsorption approximation, including pseudo-first (LDF1), pseudo-second (LDF2) and Avrami and Veneman fitting models. In addition, the theoretical LDF models of Farooq & Ruthven and a model introduced by Perry et al. (1999) were applied.According to the experimental results, the Veneman model was discovered to be the most accurate fitting model to predict the experimental results of CO2 adsorption on the studied resin whereas from the theoretical models the model of Farooq & Ruthven predicted the kinetic adsorption behaviour on the resin the best. In addition, the diffusivity coefficient was found to differ between the TGA and fixed-bed adsorption processes at 400 ppm of CO2 at 25潞C and 1.1 bar. Therefore, the global adsorption kinetic constant differs between TGA and fixed-bed adsorption processes. Considering the studied commercial zeolites, both Zeolite 4脜 and Zeolite 13X showed CO2 adsorption capacity, but for Zeolite 13X, regeneration difficulties at the desorption conditions were detected.<br /
Experimental comparison of regeneration methods for CO<sub>2</sub> concentration from air using amine-based adsorbent
Carbon dioxide use and removal : Prospects and policies
This report presents an overview of the current status of carbon capture, utilisation and storage (CCUS) and carbon dioxide removal (CDR), in terms of and main technologies, markets and policies, especially from the perspective of Finland. CDR refers to technologies and practices, which can remove carbon dioxide (CO2) from the atmosphere and store it in a manner intended to be permanent. CCUS refers to permanent storage of captured CO2 or to the utilisation of captured CO2 as a feedstock for different products which also form short- or long-term storage over their life cycle. The products can range from fuels (short lifetime) to performance polymers (long lifetime) and to mineral products (often permanent storage).
The market assessment included also quantitative and qualitative estimates for future development in size and growing CCUS and CDR solutions. Finland鈥檚 export potential in the technologies and products was also investigated. The policy environment of the technologies was assessed in terms of greenhouse gas accounting and reporting rules under the UNFCC and EU legal frameworks. Moreover, an international benchmarking of national policies was carried out to survey good practices in peer jurisdictions. Taking note of the assessed main technology options, the policy overview was used to identify policy development needs and to provide recommendations accordingly.This publication is part of the implementation of the Government Plan for Analysis, Assessment and Research. (tietokayttoon.fi) The content is the responsibility of the producers of the information and does not necessarily represent the view of the Government