Adsorption of carbon dioxide, nitrogen and methane on modified titanosilicate type molecular sieves (original) (raw)

Improvement of Methane Storage Capacity in Activated Carbon Bed with Bidisperse Packing

Brazilian Journal of Chemical Engineering

This study presents a numerical investigation of the dynamics of methane adsorption in granular activated carbon beds with bidisperse packing in order to reduce the void spaces between the adsorbent particles and to improve the storage capacity in adsorbed natural gas vessels. Two distinct particle sizes (d and D) were used for the packing of the bidisperse bed, and the following particle size ratios were investigated: δ = d/D = 1 (monodisperse bed), 1/5, 1/10, 1/15, and 1/20. Compared with the monodisperse bed condition, the results obtained showed that bidisperse packing increases bed density by about 30% and methane storage capacity by up to 20%. The results also showed that the charging time could be optimized by increasing the pressure drop applied to the bed and that the storage capacity can be increased by cooling the admitted gas in the vessel.

Particulate and membrane molecular sieves prepared to adsorb carbon dioxide in packed and staggered adsorber

Chemical Industry and Chemical Engineering Quarterly, 2018

A fixed-bed adsorption system was used to remove carbon dioxide in this study. Adsorption isotherms were obtained from a microbalance system and the characteristics of a molecular sieve affected by preparing variables were analyzed. The adsorbents, including a particulate molecular sieve and a molecular sieve membrane, were used to adsorb carbon dioxide in the fixed-bed adsorption system. Since the surface properties of the molecular sieve were affected by the preparation variables, particulate and membrane molecular sieves were synthesized to examine the effects of preparation variables on the adsorption of carbon dioxide. The experimental results showed that the pore size of the molecular sieve has increased with the chain length of quaternary ammonium salts and higher hydrothermal temperature. Adsorption isotherms for carbon dioxide adsorbed by particulate molecular sieve and molecular sieve membrane were favourable. In addition, the breakthrough curve for the lower inlet gas flo...

Continuous Fixed Bed CO2 Adsorption: Breakthrough, Column Efficiency, Mass Transfer Zone

Processes, 2020

The increased levels of carbon dioxide in the environment have incited the search for breakthrough technologies to lessen its impact on climate. The CO2 capture from a mixture of CO2/N2 was studied using a molecular sieve (MS) and silica gel type-III. The breakthrough behavior was predicted as a function of temperature, superficial velocity, and CO2 partial pressure. The breakpoint time reduced significantly with increased temperature and increased superficial velocity. The CO2 adsorption capacity increased appreciably with decreased temperature and increased CO2 pressure. The saturation CO2 adsorption capacity from the CO2/N2 mixture reduced appreciably with increased temperature. The molecular sieve contributed to higher adsorption capacity, and the highest CO2 uptake of 0.665 mmol/g was realized for MS. The smaller width of the mass transfer zone and higher column efficiency of 87.5% for MS signify the efficient use of the adsorbent; this lowers the regeneration cost. The finding...

CO2 Capture using Sodium Silicate Solution in a Packed Bed Column

E3S Web of Conferences, 2021

The use of solid adsorbents such as amine-modified silica aerogels to capture CO2 has been commonly used but poses several obstacles, including expensive raw materials, production complexity, and considerations for adsorbent regeneration. This research develops sodium silicate solution as a carbon scrubber in a packed column. Besides being able to capture CO2, the amorphous silica which has economic value can also be produced. The packing size and CO2 flow rate were studied to prevent the deposition of silica inside of the packed column. The precipitated product analysis using XRF, XRD, FTIR, and SEM Image observed that CO2 was well absorbed by sodium silicate solution. The amorphous silica precipitated concentration reaches 98.6%.

Thermal and flow effects during adsorption in conventional, diluted and annular packed beds

Chemical Engineering Science, 2010

Wall effect Thermal effect Non-isothermal model Packed bed Near infrared tomography a b s t r a c t Previous investigations have shown a complex combination of thermal and flow effects during adsorption in highly loaded, narrow packed beds. Respective conditions were realized by packing relatively large zeolite particles in a narrow tube (which causes wall channelling) and adsorbing water vapour from air on the particles (which is highly exothermic). The present work extends the investigation to novel column configurations with purposely altered conditions of heat generation and flow-namely to diluted beds, annular beds and beds consisting of coated particles. Experimental results obtained by near infrared tomography are compared with the results of breakthrough experiments in conventional columns and with numerical calculations. The latter are conducted with a non-isothermal, two-dimensional model that not only considers the increase of porosity and flow velocity near the tube wall, but also expresses the effective transport coefficients as functions of the radial coordinate. The model provides reasonable accuracy under conditions for which the usual plugflow assumption is questionable.

Velocity variation effect in fixed bed columns: A case study of CO2 capture using porous solid adsorbents

Aiche Journal, 2018

This study shows that for a reliable evaluation of porous adsorbents for carbon capture based on the fixed bed adsorption analysis, one must consider the effect of velocity variation due to adsorption to make a fair judgment on predicting the performance of materials under flow conditions. A combined experimental and numerical study of CO 2 /N 2 adsorption in fixed beds using three forms of adsorbents of amorphous powder (bulk activated carbon, AC), crystalline powder (bulk CuBTC metal-organic framework, MOF) and crystalline pellets (pelleted CuBTC) was carried out to show the effect of velocity variation on CO 2 breakthrough curves. Significant deviations are observed in the estimated amount adsorbed calculated from fixed bed experiments when models used for interpretation the measured data consider constant gas velocity because the stoichiometric time is underestimated. We show that the difference in breakthrough times estimated in models that consider constant and variable gas velocity grows exponentially with the feed gas concentration.

Adsorption of CO2 on Amine-Modified Silica Particles in a Confined-Fluidized Bed

2020

To reduce the anthropogenic CO2 emissions produced from fossil fuel burning plants, the application of carbon capture and storage (CCS) is necessary and development of a more efficient and economically feasible CO2 capture process is essential as an alternative to the conventional amine scrubbing process which uses aqueous amine solutions. CO2 capture can be enhanced by improving both the gas–solid contact efficiency and by tuning a specific high-performance sorbent. The aim of this research is to investigate the adsorption of CO2 using impregnated mesoporous silica in a “confined-fluidized bed”. This non-conventional fluidized bed (sometimes also termed the “packed-fluidized bed”) seems suitable for improving the efficiency of gas–solid processes for which the bypass effect of the gas–solid contact caused by bubbling represents a major drawback. Results, expressed as grams of CO2 adsorbed per kilogram of material, are discussed in terms of amine load in the sorbent, breakthrough ti...

Theoretical Investigation of Axial and Local Particle Size Distribution on Expanded Bed Adsorption Process

Biotechnology Progress, 2004

The general rate model was developed and solved to describe protein adsorption in an expanded bed. The model takes into account axial variation of bed porosity, particle size distribution (PSD), external and intraparticle mass transfer, and dispersion in liquid and solid phase. The analysis of the influence of the model parameters on dynamic capacity (DC) was investigated. The simulation results showed that major impact on dynamic capacity is exerted by intraparticle mass transfer (particle diameter and pore diffusivity). The external mass transfer resistance and dispersion parameters have secondary effect on DC. The replacement of axial PSD by the mean particle diameter results in error in calculation of DC, which increases remarkably with the increase of mean particle diameter. The PSD can promote a very slow approaching of plateau concentration by breakthrough curves. It was shown also that axial bed porosity variation could be replaced by average porosity with negligible error for DC calculations.

Optimum structured adsorbents for gas separation processes

Chemical Engineering Science, 2009

Recent developments in separation technology by adsorption have included the development of new structured adsorbents which offer some attractive characteristics compared to a typical packed bed. These improved features include lower energy consumption, higher throughput and superior recovery and purity of product. However, the exact combination of structural, geometric parameters which yields optimum performance is unknown. This study formulates a methodology for comparison based on a variety of analytical and numerical models and uses it to examine the performance of different adsorbent configurations. In particular, monolithic, laminate and foam structures are evaluated and compared to a packed bed of pellets. The effects of physical adsorbent parameters which govern the performance of a PSA process are considered during model development. Comparisons are carried out based on mass transfer kinetics, adsorbent loading and pressure drop of a PSA system for CO 2 /N 2 separation. The results indicated that structured adsorbents can provide superior throughput to packed beds provided their geometrical parameters exceed certain values. For example, laminate structures can offer superior performance to a packed bed of pellets only if the critical sheet thickness and spacing are less than about 0.2 mm. Each adsorbent structure should be designed to operate at its "optimal" velocity. When operating at velocities higher than the "optimal" value, the increase in pressure drop and length of the mass transfer zone more than offsets gains accrued through reduction in cycle time.