1,720,976 research outputs found
Sorption-Based Thermal Energy Storage: Material Development and Effects of Operating Conditions
No full textThe adverse effects of climate change, the steady depletion of fossil fuels, and the industrialization of
developing countries have resulted in an increased supply and demand of renewable thermal energy.
Renewable thermal energy sources like solar thermal energy produce fewer local emissions but have a
temporally inconsistent power output. The consumer space heating and domestic hot water demands
also vary as a function of time. This creates a mismatch between thermal energy supply and demand.
Energy storage is one method of solving this problem. However, conventional methods, like hot water
storage, are voluminous and can only store heat for short periods of time. Therefore, compact long-term
energy storage technologies, like sorption-based energy storage systems, require research and
development. The current work aims to identify and develop suitable materials for sorption-based energy storage systems and to determine the effects of operating conditions on the performance of thermal energy storage systems.
A material screening study was performed, which identified MCM-41, SAPO-34, and silica gel, which are
all silica-based materials, as suitable materials for sorption-based energy storage. The effects of key
operating variables for a silica gel/water-vapour adsorption-based energy storage system were quantified and optimized. The optimized system energy storage density value was nearly double that of unoptimized systems. The effects of salt impregnation were investigated by impregnating different hosts with MgSO4 salt and varying the concentration of the salt in the host material. All composites were stable after three hydration/dehydration cycle. A silica gel/MgSO4 hybrid containing 33 wt% MgSO4 was found to have the highest energy storage density of all of the MgSO4-based composites. Finally, CaCl2, a promising hygroscopic for thermal energy storage was stabilized via impregnation into silica gel and encapsulation in methylcellulose. A novel synthesis technique involving the simultaneous impregnation of silica gel with CaCl2 and encapsulation in methylcellulose produced a stable encapsulated salt-in matrix composite with a high energy storage performance
Gas Separation by Adsorption in Order to Increase CO2 Conversion to CO via Reverse Water Gas Shift (RWGS) Reaction
No full textIn this research project, adsorption is considered in conjunction with the reverse water gas shift reaction in order to convert CO2 to CO for synthetic fuel production. If the CO2 for this process can be captured from high emitting industries it can be a very good alternative for reduced fossil fuel consumption and GHG emission mitigation. CO as an active gas could be used in Fischer-Tropsch process to produce conventional fuels. Literature review and process simulation were carried out in order to determine the best operating conditions for reverse water gas shift (RWGS) reaction. Increasing CO2 conversion to CO requires CO2/CO separation downstream of the reactor and recycling unreacted CO2 and H2 back into the reactor. Adsorption as a viable and cost effective process for gas separation was chosen for the CO2/CO separation. This was started by a series of adsorbent screening experiments to select the best adsorbent for the application. Screening study was performed by comparing pure gas isotherms for CO2 and CO at different temperatures and pressures. Then experimental isotherm data were modeled by the Temperature-Dependent Toth isotherm model which provided satisfactory fits for these isotherms. Henry law’s constant, isosteric heat of adsorption and binary mixture prediction were determined as well as selectivity for each adsorbent. Finally, the expected working capacity was calculated in order to find the best candidate in terms of adsorption and desorption. Zeolite NaY was selected as the best candidate for CO2/CO separation in adsorption process for this project. In the last step breakthrough experiments were performed to evaluate operating condition and adsorption capacity for real multi component mixture of CO2, CO, H2 in both cases of saturated with water and dry gas basis. In multi components experiments zeolite NaY has shown very good performance to separate CO2/CO at low adsorption pressure and ambient temperature. Also desorption experiment was carried out in order to evaluate the working capacity of the adsorbent for using in industrial scale and eventually temperature swing adsorption (TSA) process worked very well for the regeneration step. Integrated adsorption system downstream of RWGS reactor can enhance the conversion of CO2 to CO in this process significantly resulting to provide synthetic gas for synthetic fuel production as well as GHG emission mitigation
Adsorptive Thermochemical Energy Storage and it’s Impacts on Space Heating
No full textOver the past 200 years, human activities have increased the carbon dioxide content in the atmosphere by 50% [1]. Currently, this corresponds to a 1.1oC rise above 1850-1900 average global temperatures in 2011-2020 [2]. If the global average temperature continues to rise past 1.5oC, the human population will face unprecedented climate-related risks and weather events [3]. In 2020, over half (53.5%) of the energy consumed by the space heating sector in Canada was supplied by fossil fuels [4]. To help reduce fossil fuel emissions and reach 2050 net zero goals a reduction in greenhouse gas emissions is required. To help address the problem, a heat storage technology is developed to store thermal energy for use in space heating applications. The focus on this thesis is on the modelling and simulation of the thermal energy storage
technology developed based on exothermic adsorption process and its validation with experimental results. The effect of column volume and length to diameter ratios on the performance of the system have been experimentally studied and simulated. The simulation was carried out by using gPROMS (general Process Modelling System) software. It incorporates single dimension heat and mass transfer equations where the radial changes along the column are neglected. The simulation uses the Guggenheim-Anderson-de Boer (GAB) isotherm model to describe the moisture equilibrium behaviour with the adsorbent sample. The modelling results show good agreement with the experimental data. Effects of length to diameter ratios show an increasing trend in energy storage density with decreasing length to diameter ratios. The fitted model was also coded in Fortran and implemented in a TRNSYS (Transient System Simulation Tool) simulation to study the performance of this energy storage technology in home heating scenarios. Using the results from the TRNSYS simulation the economic viability of this technology is explored
Thermal Energy Storage Using Adsorption Processes for Solar and Waste Heat Applications: Material Synthesis, Testing and Modeling
No full textAs the worldwide energy demand continues to increase, scientists and engineers are faced with the increasingly difficult task of meeting these needs. Currently, the major energy sources, consisting of oil, coal, and natural gas, are non-renewable, contribute to climate change, and are rapidly depleting. Renewable technology research has become a major focus to provide energy alternatives which are environmentally-friendly and economically competitive to sustain the future worldwide needs. Thermal energy storage using adsorption is a promising technology which can provide energy for heating and cooling applications using solar and waste heat sources. The current work aims to improve adsorption systems to provide higher energy outputs and therefore, more economical systems. New adsorbents and operating conditions were tested with the goal of storing the available energy more efficiently. A model was also developed to gain a better understanding of the adsorption system to improve this developing technology
Optimization of Using Polymeric and Mixed Matrix PVA Amine-based Membranes for CO2/N2 and CO2/CH4 Separation
No full textSeparation of CO2, the main global warming causing greenhouse gas, from other flue gases and from biogas has become of great interest due to the predicted effects of global warming that the world is already starting to experience. This research focuses on the separation of CO2 from CH4 and N2 gases using polymeric and mixed matrix membranes. Amine-based poly vinyl alcohol (PVA) polymeric membranes that had previously shown good gas separation results were adapted for use in this research. The physical aging of the adapted membrane was initially analyzed for 37 days and it was observed that the membrane stabilized after 21 days. The adapted membrane was then optimized using a 26 factorial design to improve the membranes’ performance with respect to CO2/N2 and CO2/CH4 selectivity when tested using single gas permeation experiments at near atmospheric conditions. This was done with the membrane components: PVA, formaldehyde, poly (allylamine hydroxide), potassium hydroxide, water and 2-aminoisobutyric acid. Zeolite 13X and ZIF-8 powdered adsorbents were incorporated in the optimized membranes to prepare mixed-matrix membranes with the goal of bettering the separation performance of the membranes. Membrane characterization was done on the best performing membranes through spectroscopy, microscopy, and contact angle measurements. This study concluded with feed pressure tests on the overall best performing membranes. The performance of the fabricated membranes was compared to other polymeric and mixed-matrix membranes and Robeson’s upper bound line. Overall, the polymeric optimized membranes seemed to perform better than the filled mixed matrix membranes due to the introduction of agglomerations and cracks with both the filler materials. Also, the separation performance of the membrane improved with a decrease in pressure. At 1.5 absolute pressure, the optimized membrane was able to achieve a CO2/N2 and CO2/CH4 selectivity of 5.94 and 2.13 respectively with a CO2 permeability of 15,813 Barrer
Cation Exchange Modification of Clinoptilolite Zeolite for Applications in Nitrogen Rejection
No full textNatural gas and biogas are increasingly important resources to the global energy mix. With the growth in the development of unconventional resources, contaminate gases within natural gas mixtures are growing challenges for industry. Inert gases such as N2 cannot be more than 4%vol. in order to meet pipeline specifications. This is done in an effort to increase the heating value and reduce the compression volume of the natural gas. While approximately 15% of natural gas reserves in the United States do not meet this threshold, additional sources including fugitive methane emissions from gas wells and coal bed gas also contain large amounts of N2 relative to CH4. For these kinds of gases to be used commercially they need to be treated. Conventional treatment methods such as cryogenic distillation are energy intensive; requiring large economies of scale and intense process integration to improve efficiency. Therefore, the development of some unconventional natural gas resources proves to be very difficult particularly for small and more remote operations. As the easier and better quality fuel stocks become more difficult to extract, the need to improve overall processing techniques by exploring energy efficient and cost effective separation systems becomes more important. The integration of adsorption technology within existing natural gas upgrading processes has the potential to achieve a more economical separation of N2 from hydrocarbon mixtures. However, such technologies have shown limited commercial success as almost all adsorbents are only moderately selective for CH4 over N2, with only a few adsorbents being N2 selective. The screening and characterization of new adsorbent materials is thus necessary prior to implementing such separation technologies on a greater scale.
Following an extensive adsorbent screening study, clinoptilolite was found to be a material of interest due to both favourable kinetic and equilibrium separation properties. The objective of this research was thus to modify clinoptilolites through cation exchange to improve the separation of N2 and/or CO2 from natural gas or biogas resources. Clinoptilolite is a naturally occurring aluminosilicate zeolite with a very narrow effective pore size distribution. This adsorbent is unique as it may be either CH4 selective or N2 selective. Since the framework charge of clinoptilolite is negative, charges balancing extra framework cations occupy the channels of the zeolite. This zeolite may be modified through cation exchange to induce favourable separation properties by altering the morphology of the material. Following screening, the adsorption characteristics of CO2, CH4, and N2 on the adsorbents were evaluated and their performances were related to the underlining morphology and elemental composition of these materials. Temperature effects and experimental CH4 and N2 mixture adsorption measurements were compared to multicomponent extensions of single gas adsorption isotherms. These adsorbent materials are promising candidates for the application of natural gas refining. Their implementation into various adsorption technologies are considered.
Findings from this research showed the possibility of improved CH4/N2 equilibrium selectivity over natural clinoptilolite using Cs+ and Fe3+ exchanged varieties. Additionally, the possibility of N2/CH4 selective kinetic separations were demonstrated for Ni2+ and Li+ exchanged clinoptilolites. Ag+ exchanged clinoptilolite was shown to be N2 selective over CH4 for potential equilibrium adsorption separations. Finally, the idea of membranes formed of clinoptilolite and a glass binder supported by a porous ceramic alumina support were presented for the first time
Purification of Indoor Air Pollutants Utilizing Hydrophobic Adsorbents
No full textSick building syndrome (SBS) is a particular concern in places with inadequate ventilation
and frequently attributed to chemical contaminants such as volatile organic compounds (VOCs)released from indoor sources that are frequently encountered in everyday life such as adhesives, carpeting, upholstery, manufactured wood products, copy machines, pesticides, cleaning agents inside buildings, plumbing vents, and painting. Furthermore, it is a major issue for modern human beings who spend most of their time indoors or must stay indoors for self-isolation due to special circumstances such as the coronavirus disease-19 (COVID-19) pandemic that occurred in 2019 and 2020. Main indoor VOCs are trichloroethylene (TCE), benzene, toluene, and para-xylene (p-xylene). In general, these compounds are not present in indoor spaces at acute concentrations, but prolonged exposure to these compounds can have chronic health effects such as allergic sensitization, increased cancer risks, and respiratory diseases.
In this study, the adsorption process with various advantages has been applied to remove
VOC’s using commercially available hydrophobic adsorbents. The hydrophobic adsorbents can contribute to reducing the possibility of chemical adsorption (chemisorption) of moisture from the air, which can decrease the capacity of adsorbent by clogging the pores. The adsorption of these major VOCs was investigated in this work for three major types of industrial hydrophobic adsorbents: activated carbons, zeolites, and polymer.
This study will show the investigation into finding the most promising hydrophobic
adsorbent for removal of TCE, benzene, toluene, and p-xylene, which are the main VOCs found indoors. The promising hydrophobic adsorbent has been determined by comparing Henry’s law constants and heat of adsorption values for the different adsorbents, which were estimated by using a concentration pulse chromatographic technique by utilizing a gas chromatograph equipped with a flame ionization detector.
For all adsorbents, Henry’s law constants at room temperature of p-xylene were always
the highest followed by toluene, benzene, and TCE. For all adsorbates, Henry’s law constants at room temperature of AC BPL and HiSiv 3000 were higher than the other hydrophobic adsorbents.
For a developing modern society dealing with a pandemic, this study can contribute to
producing the optimized gas masks and indoor filters for the removal of indoor air pollutants,
which can help people who suffer from SBS. It can also help society for taking preventative actions towards dealing with SBS
Adsorption Separation of CO2 in Low Concentrations for Applications in Direct Air Capture and Excimer Gas Separation
No full textThe overall objective of this thesis is to evaluate the fundamentals of current low concentration CO2 separation technologies and to provide an alternate method using adsorption technology with existing as well as new adsorbents. Two different applications for the adsorption of CO2 are explored; Direct Air Capture (DAC) and excimer gas purification. The investigation of aerogels as possible adsorbent for these applications was also explored.
The first application, DAC of CO2 using adsorbents, addresses climate change by reducing the amount of atmospheric CO2 levels that are directly correlated to global warming. Because of DAC being carbon negative, this field has gained significant attention in the literature. DAC as a CO2 reduction strategy was approached in two ways:
1. Chapter 2 investigates capturing and concentrating CO2 from 0.04% in the air to 95% to be able to sequester it into the ground. This research began by doing an adsorbent selection using pure gas gravimetric measurements on seven different commercially available type X zeolites that were determined to have potential for this separation. Breakthrough experiments were then carried out with the most promising zeolite by perturbing the bed with compressed ambient air. In the process studied, a basic four step temperature vacuum swing adsorption (TVSA) cycle was investigated comprising the following steps: pressurization, adsorption, blowdown, and desorption. Four different regeneration temperatures were tested along with four different gas space velocities. With this cycle configuration, CO2 was concentrated to 95% from 0.04% with total capture fractions as high as 81%. This study highlighted methods to reduce the energy consumption per ton of CO2 captured in the system as well as the potential of using low Si/Al ratio faujasite structured zeolites in DAC of CO2 for greenhouse gas reduction.
2. Chapter 3 expands on the research of Chapter 2 by capturing CO2 from 0.04% in the air and concentrating it to high purity CO2 levels where the cost for operating the process will be reimbursed through the value of the produced CO2. The goal of this research was to increase the CO2 to as high as possible because the purer the CO2, the more valuable it is. This research started by conducting an in-depth investigation into the pure gas adsorption of CO2, N2, O2, and Ar on the most promising zeolite from Chapter 2. The data was then fitted to the TD-Toth model which allowed for the evaluation of the TVSA cycle and showed the potential of reducing the pressure and/or elevating the temperature during the blowdown step in order to produce high purity CO2. To confirm this, the TVSA cycle was run on a fixed bed breakthrough experiment where high purity CO2 was produced between a concentration of 99.5% and 99.96% by lowering the blowdown pressure. By controlling the blowdown temperature, the concentration of the product was increased from 99.8% to 99.95%, however with a significant loss of CO2. This effect of N2, O2, and Ar desorbing during the blowdown step with CO2 desorbing during the evacuation step is shown graphically by measuring the concentration and flow rate of the exiting gas species. The results from this study show the potential for producing a valuable product of high purity CO2 from atmospheric concentrations.
The second application in this thesis that is explored in Chapter 4 is the purification of trace impurities of CO2, CF4, COF2, and O2 from F2, Kr, and Ne for applications in excimer lasers. Due to the incompatibility of many adsorbents to F2 and HF, aluminas and polymeric adsorbents were selected as potentially compatible materials. To increase the compatibility of these adsorbents, the use of a cryo-cooler was determined to be feasible to precool the feed stream before separation, which increases the adsorption capacity and compatibility of the material to F2 and HF. To determine the adsorption potential in the low concentration of these adsorbents, the concentration pulse chromatographic technique was chosen to determine the Henry’s Law constants of CO2, CF4, and O2. This data was then plotted on the van’t Hoff plot and extrapolated to colder temperatures to determine the benefit of using a cryo-cooler. From this study, it was determined that HayeSep Q was the best polymeric adsorbent with significant adsorption of CO2 at temperatures below -50˚C while being the best performing CF4 adsorbent. AA-300 was the best performing alumina in this study while having significant adsorption of CF4 at temperatures below -135˚C. However, from a compatibility standpoint, both of these materials need to be tested to determine their robustness in the presence of F2 and HF at room and reduced temperatures.
Chapters 5 & 6 in this thesis explore the fundamentals of adsorption on aerogels as a prelude to using aerogels as possible adsorbents for DAC of CO2. This investigation into aerogels looks at silica aerogels and carbon aerogels, which are both industrially produced and explores their adsorption with relation to like materials such as silica gel and activated carbons. Both of these Chapters utilize experimentally determined adsorption isotherms of CO2, N2, O2, and Ar as well as characterization to determine adsorption trends in the materials. Some major conclusions for silica aerogels were that common surface modifications to make the material more resilient against water adsorption impacts the adsorption of CO2 significantly with roughly 4 fold difference in adsorption capacity. For carbon aerogels some major conclusions were that the adsorption was increasingly dominated by the heterogeneous nature of the surface at lower pressures and increasingly dominated by the pore size at the higher pressures. Both chapters discuss the adsorption of air along with ideas such as the influence of gas thermal conductivity in the pores with respects to adsorption.
L'objectif général de cette thèse est d'évaluer les principes fondamentaux des technologies actuelles de séparation du CO2 à faible concentration et de fournir une méthode alternative utilisant la technologie d’adsorption avec des adsorbants actuels ainsi que d'en découvrir de nouveaux. Deux applications différentes pour l'adsorption du CO2 ont été explorées; la capture directe dans l’air ambient (CAD) et la purification des gaz excimères, ainsi que la recherche d'aérogels comme adsorbant possible pour ces applications.
La première application, le CAD du CO2 utilisant des adsorbants, pourrait répondre aux changements climatiques puisque les niveaux de CO2 atmosphérique sont directement corrélés au réchauffement climatique. Dernièrement, le CAD a fait l'objet d'une attention particulière en tant que stratégie de réduction du CO2, par conséquent, deux voies différentes ont été explorées dans cette thèse:
1. Le chapitre 2 étudie la capture et la concentration du CO2 de 0,04% dans l'air à 95% afin de pouvoir l’enfermer dans la terre. Pour ce faire, une sélection d'adsorbant a été effectué en utilisant des mesures gravimétriques à gaz pur sur sept zéolithes de type X disponibles dans le commerce qui ont été déterminés comme ayant un potentiel pour cette séparation. Des expériences révolutionnaires ont ensuite été réalisées avec la zéolite la plus prometteuse en perturbant le lit avec de l'air ambiant comprimé. Dans le processus étudié, un cycle basique à quatre étapes d’adsorption modulée en température et pression (AMTP) a été étudié, comprenant les étapes suivantes: pressurisation, adsorption, purge et désorption. Quatre températures de régénération différentes ont été testées ainsi que quatre vitesses spatiales de gaz différents. Avec cette configuration de cycle, le CO2 était concentré à 95% de 0,04% avec des fractions de capture totales aussi élevées que 81%. Cette étude a mis en évidence des méthodes pour réduire la consommation d'énergie par tonne de CO2 captée dans le système ainsi que le potentiel d'utilisation de zéolithes structurées à base de faujasite à faible rapport Si/Al dans le CAD du CO2 pour la réduction des gaz à effet de serre.
2. Le chapitre 3 approfondit les recherches du chapitre 2 en capturant le CO2 de 0,04% dans l'air et en le concentrant à des niveaux de très haute pureté où le processus sera remboursé par la valeur du CO2 produit. L'objectif de cette partie était d'augmenter la pureté du CO2 le plus possible car plus le CO2 est pur, plus il est précieux. Une enquête approfondie sur l'adsorption de gaz pur de CO2, N2, O2 et Ar sur la zéolite la plus prometteuse du chapitre 2. Les données ont ensuite été ajustées au modèle TD-Toth qui a permis d'évaluer le cycle AMTP et a montré le potentiel de réduire la pression et/ou d'élever la température pendant l'étape de purge afin de produire du CO2 de haute pureté. Pour confirmer cela, le cycle AMTP a été fait par le biais d’une expérience dans un lit fixe où du CO2 de haute pureté a été produit entre une concentration de 99,5% et 99,96% en abaissant la pression de purge. En contrôlant la température de purge, la concentration du produit est passée de 99,8% à 99,95%, mais avec une perte importante de CO2. Cet effet de la désorption de N2, O2 et Ar pendant l'étape de purge avec la désorption du CO2 pendant l'étape d'évacuation est illustré graphiquement en mesurant la concentration et le débit des espèces de gaz sortant. Les résultats de cette étude montrent le potentiel de production d'un produit précieux de CO2 de haute pureté à partir des concentrations atmosphériques.
La deuxième application de cette thèse qui est explorée au Chapitre 4 est la purification des traces d'impuretés de CO2, CF4, COF2 et O2 de F2, Kr et Ne pour des applications dans les lasers à excimère. En raison de l'incompatibilité de nombreux adsorbants avec le F2 et le HF, les alumines et les adsorbants polymères ont été sélectionnés comme matériaux potentiellement compatibles. Pour augmenter la compatibilité de ces adsorbants, l'utilisation d'un cryoréfrigérant a été jugée possible pour pré-refroidir le flux d'alimentation avant la séparation, ce qui augmente la capacité d'adsorption et la compatibilité du matériau en F2 et HF. Pour déterminer le potentiel d'adsorption dans la faible concentration de ces adsorbants, la technique de chromatographie pulsée de concentration a été choisie pour déterminer les constantes de la loi de Henry de CO2, CF4 et O2. Ces données ont ensuite été tracées sur le graphique van’t Hoff et extrapolées à des températures plus froides pour déterminer les avantages de l’utilisation d’un cryoréfrigérant. À partir de cette étude, il a été déterminé que HayeSep Q était le meilleur adsorbant polymère avec une adsorption significative de CO2 à des températures inférieures à -50 ° C tout en étant l'adsorbant CF4 le plus performant. L'AA-300 était l'alumine la plus performante de cette étude tout en ayant une adsorption significative de CF4 à des températures inférieures à -135 °C. Cependant, du point de vue de la compatibilité, ces deux matériaux doivent être testés pour déterminer leur robustesse en présence de F2 et de HF à température ambiante et réduite.
Les chapitres 5 et 6 explorent les principes fondamentaux de l'adsorption sur les aérogels en prélude à l'utilisation d'aérogels comme adsorbants possibles pour le CAD du CO2. Cette enquête sur les aérogels examine les aérogels de silice et les aérogels de carbone, qui sont tous les deux fabriqués industriellement et explore leur adsorption par rapport à des matériaux similaires tels que le gel de silice et les charbons actifs. Ces deux chapitres utilisent des isothermes d'adsorption déterminés expérimentalement de CO2, N2, O2 et Ar ainsi que la caractérisation pour déterminer les tendances d'adsorption dans les matériaux. Certaines conclusions majeures pour les aérogels de silice étaient que les modifications de surface courantes pour rendre le matériau plus résistant à l'adsorption d'eau ont un impact significatif sur l'adsorption de CO2 avec une différence d'environ 4 fois dans la capacité d'adsorption. Pour les aérogels de carbone, certaines conclusions majeures étaient que l'adsorption était de plus en plus dominée par la nature hétérogène de la surface à des pressions plus faibles et de plus en plus dominée par la taille des pores aux pressions plus élevées. Les deux chapitres discutent de l'adsorption d'air ainsi que des idées telles que l'influence de la conductivité thermique du gaz dans les pores en ce qui concerne l'adsorption
Adsorption Separation of CO2 from CO in Syngas: Improving the Conversion of the Reverse Water Gas Shift Reaction
No full textIn this research project, adsorption is considered for the separation of CO2 from CO for applications such as industrial syngas production and in particular to improve the conversion of the Reverse Water Gas Shift (RWGS) process. The use of adsorption technology for these applications requires an adsorbent that can effectively separate out CO2 from a gas mixture containing CO2, CO, and H2. However, adsorption of H2 is insignificant when compared to both CO2 and CO, with only CO2 and CO being the adsorbed species. The adsorption of CO2 and CO was investigated in this work for four major types of industrial adsorbents which include: activated aluminas, activated carbons, silica gels, and zeolites. Zeolites, with their ability to be fine tuned many parameters which may affect adsorption, were investigated in terms of the effect of the cations present, SiO2/Al2O3 ratios, and structure to determine how to optimize adsorption of CO2 while decreasing adsorption of CO. This will help to determine a promising adsorbent for this separation with focus on maximizing the selective adsorption of CO2 over CO.
To investigate this separation three scientific experimental methods were used; gravimetric adsorption isotherm analysis, volumetric adsorption isotherm analysis, and packed bed adsorption desorption breakthrough analysis. Gravimetric and volumetric methods allow for testing the adsorbent with the individual species of CO2 and CO. This investigation will let us determine the pure component adsorption capacity, heats of adsorption, regenerability, and basic selectivity. Packed bed adsorption breakthrough experimentation was then carried out on promising adsorbents for the CO2 separation from a mixture of CO2, CO, and H2. These experiments used a gas mixture that would be comparable to that produced from the RWGS reaction to determine the multicomponent gas mixture behaviour for adsorption. Temperature swing adsorption (TSA) with a purge gas stream of H2 was then used to regenerate the adsorbent
Adsorbent Screening for the Separation of CO₂, CH₄, and N₂
No full textThe objective of this research was to determine an appropriate adsorbent for the separation of CH₄ from CO₂, N₂, and O₂. To screen different adsorbents for this purpose, pure component adsorption isotherms and gas mixture isotherms were measured.
Adsorption isotherms are critical data for modeling adsorption processes. Thus, determining an accurate and reliable method of measuring gas adsorption isotherms is crucial. Concentration pulse chromatography can be used to measure the slope of the isotherm. In the case of pure component adsorption, the slope at different partial pressures of adsorbate can be integrated to determine the adsorption isotherm. The accuracy of the concentration pulse chromatography method was compared to that of gravimetric analysis to find an appropriate technique to obtain pure component gas adsorption isotherms by measuring CH₄ isotherms on activated carbon at 25°C and up to 6.3 atm. Isotherm results from concentration pulse chromatography were identical to gravimetric results, but the use of a sufficiently long column for concentration pulse chromatography was crucial.
Afterwards, gravimetric analysis was used to determine the performance of activated carbon (AC A-C) and carbon molecular sieve (CMS A-D) adsorbents for adsorbing CO₂ and N₂. Additionally, O₂ adsorption isotherms were measured for CMS's. At 25°C and above atmospheric pressure, AC-B showed the highest CO₂ capacity and CO₂/N₂ selectivity. The isosteric heat of adsorption values of CO₂, N₂, and O₂ for the CMS's were calculated; CMS-A and CMS-C had high isosteric heat of adsorption values for CO₂, above 40 kJ mol⁻¹.
Finally, the performance of activated carbon in separating a binary mixture of CO₂ and N₂ was experimentally measured by obtaining binary gas mixture adsorption isotherms using concentration pulse chromatography technique between 30-70°C and 1-5 atm total pressure. The OLC activated carbon showed selectivity for CO₂ over N₂, with the experimental results showing a slight deviation from theoretical predictions of the binary adsorption isotherms. Compared to other adsorbents in the literature, OLC had similar CO₂ and N₂ adsorption capacities but higher CO₂/N₂ selectivity
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