Adsorption of Volatile Organic Compounds on Beaded Activated Carbon and Regenerated by Electrothermal Swing Adsorption System PDF Download

Author: 尤皓鋕
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Category :
Languages : en
Pages :

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Author: 蕭世盈
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Category :
Languages : en
Pages :

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Category :
Languages : en
Pages : 0

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Activated-carbon fiber-cloth (ACFC) has been investigated as an alternative adsorbent to remove volatile organic compounds (VOCs) and hazardous air pollutants (HAPs) from gas streams when compared to conventional granular activated carbons (GACs). ACFC has up to twice the adsorption capacity of GAC and is more suited to electrothermal regeneration.

Author: Samineh Kamravaei
Publisher:
ISBN:
Category : Carbon, Activated
Languages : en
Pages : 90

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Adsorption on activated carbon is a widely used technique for controlling emissions of volatile organic compounds (VOCs) from automotive painting booths; however, irreversible adsorption is a common challenge in this process. This research investigates the effect of adsorbent bed configuration on adsorption of VOCs on beaded activated carbon (BAC). Fixed and fluidized bed adsorption of a single compound (1, 2, 4 - trimethylbenzene) and a mixture of nine organic compounds representing different organic groups were accomplished in five consecutive cycles. Adsorption tests were completed either in partial or full loading of the adsorbent. All regeneration cycles were completed in fixed bed arrangement. The results demonstrated similar adsorption capacities obtained in both configurations. However, 30 - 42% lower heel formation was found using fluidized bed than in fixed bed in case of the VOCs mixture. Thermo - gravimetric analysis confirmed less organic accumulation on BAC after regeneration for the bed loaded with the VOCs mixture in fluidized bed configuration. The lower irreversible adsorption obtained using fluidized bed adsorption could be due to improved mass transfer and more complete utilization of BAC's available pore volume in the fluidized bed, and non - uniform adsorbate distribution on the BAC, and displacement of lighter compounds with heavier ones in the fixed bed.

Author: Amin Sadeghi Ardekani
Publisher:
ISBN:
Category : Adsorption
Languages : en
Pages : 0

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Activated carbon (AC) has attracted tremendous interest in adsorption-based air treatment. Nonetheless, a major challenge associated with the use of ACs is the decline in adsorption capacity with time due to heel build-up (i.e., accumulation of non-desorbed species). Designing a reliable adsorption system requires a deeper understanding of the changes occurring during the long-term use of ACs. For this purpose, the effect of ACs' properties such as porosity and operational conditions such as purge gas flow rate on the long-term performance of ACs requires further investigation. The objective of the present work was two-fold: first, to study the simultaneous effect of purge gas flowrate and activated carbon's porosity during prolonged cyclic adsorption/regeneration of three different ACs. Secondly, develop a model that can predict the long-term performance of ACs during adsorption/regeneration of a representative volatile organic compound (VOC). This section itself comprised two main stages: 1) Modeling the impact of heel on AC's pore size distribution (PSD), adsorption isotherm, and capacity, and 2) verifying the model using cyclic adsorption-desorption of 1,2,4-trimethyl benzene (TMB). The model predicts the cyclic adsorption capacity of AC by applying the Dubinin-Radushkevich-Langmuir (D-R-L) isotherm based on AC's limiting pore volume and adsorbate-adsorbent affinity coefficient. For the long-term experimental study, six scenarios were investigated by varying the dry air purge gas flow rates 0.5 and 5 SLPM and the porosity of adsorbent used (44%, 60%, and 86% microporosity). The cyclic adsorption/regeneration experiment results indicated that the cumulative heel and the adsorption capacity followed ascending and descending trends with cycle number, respectively. Initially, the porosity and micropore volume of the adsorbents played a more important role in their performance. However, at higher cycle numbers, the effect of purge gas flow rate was more determinant in the performance of ACs. In the first five cycles, the two adsorbents with the highest micropore volume, G-70R, and B101412, showed similar heel build-up formation rates while B100772 with lower micropore volume (0.43 (cm^3)/g as opposed to 0.50(cm^3)/g) had slightly lower heel build-up. Alternatively, at the 20th cycle, purge gas flow rate had a clear effect on the performance and cumulative heel build-up of all three ACs regardless of their porosity. For all three adsorbents used in this study, samples regenerated with 0.5 SLPM all had an average cumulative heel of 31%. Those regenerated with 5 SLPM Had a cumulative heel build-up average of 21%. The presence of mesopores and a hierarchal pore structure certainly helped reduce heel build-up in the micropores. DTG analysis of the samples showed that with an increase in purge gas flow rate, the nature of heel build-up starts to change and transform into heavier chemically formed compounds. In the second part, two machine learning (ML) algorithms, multivariate linear regression (MLR) and Decision tree, were applied to predict Micropore volume reduction because of volatile organic compounds (VOCs) cyclic heel build-up on activated carbons (ACs). A dataset of 100 experimental tests of cyclic adsorption/regeneration of different VOCs on ACs with distinct properties was used. It was observed that micropore volume reduction could be predicted with acceptable accuracy with an R2 of 0.85 ± 0.08 using the MLR algorithm by considering the adsorbent characteristics, adsorbate properties, and regeneration conditions. The micropores prediction results were then combined with several mathematical equations to predict the pore size distribution of a used activated carbon. To verify the model, its results were tested against nine samples with various stages of heel build-up. The micropore and PSD were predicted with a mean relative absolute error (MRAE) of 3.5%, 10.8%, and 12.0% for G-70R, B101412, and B100772, respectively. The PSD prediction model was then utilized in conjunction with the DRL isotherm prediction model, and the adsorption capacity of samples at five concentrations of 0, 50, 100, 500, and 1000 ppm were predicted for each adsorbent. The prediction of adsorption capacity on the virgin G-70R, B101412, and B100772 had a MRAE of 0.6%, 8.9%, and 2.7, respectively while for the corresponding used samples the MRAE was 13.2%, 10.1%, and 10.0%. The results of this study are beneficial in improving the long-term performance of activated carbons and making them last longer.

Author:
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Category : Carbon fibers
Languages : en
Pages : 8

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Author: Vernon L. Snoeyink
Publisher:
ISBN:
Category : Carbon, Activated
Languages : en
Pages : 136

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Author: Hamidreza Emamipour
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Category :
Languages : en
Pages :

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Emissions of hazardous air pollutants (HAPs) and volatile organic compounds (VOCs) to the atmosphere are serious environmental issues. There were 0.53 billion kg of HAPs and 15 billion kg of VOCs emitted to the atmosphere from anthropogenic sources during 2004 and 2002, respectively. Eighty-nine percent of those HAPs were emitted from point sources that can be readily captured by techniques such as adsorption. The cost to meet regulations for VOC control during 2010 was estimated at $2.3 billion/yr. Environmental regulations encourage the development of new technologies to more effectively remove HAPs/VOCs from gas streams at lower cost. Electrothermal Swing Adsorption (ESA), as described here, is a desirable means to control these emissions as it allows for capture, recovery and reuse or disposal of these materials while providing for a more sustainable form of technological development. The Vapor Phase Removal and Recovery System (VaPRRS or ESA-R)) was initially evaluated for possible improvements. An automated bench-scale adsorption device using activated carbon fiber cloth (ACFC) was designed and built to study effects of select independent engineering parameters on the ability of the system to capture and recover an organic vapor (e.g., methyl ethyl ketone, MEK) from air streams. Factors that can increase the adsorbate liquid recovery with low energy costs were investigated using sequentially designed sets of laboratory experiments. Initially, the screening experiments were conducted to determine significant factors influencing the energy efficiency of the desorption process. It was determined that 0́−concentration of organic vapor0́+, 0́−packing density0́+, and 0́−maximum heating temperature0́+ are significant factors while 0́−nitrogen flow0́+ and 0́−heating algorithm0́+ are insignificant factors in the ranges of values that were evaluated. Experimental data provided from this work were then used as inputs by Kaldate (2005) to complete a response surface methodology using Central Composite Design to optimize the operation of the ESA system in a region where efficient liquid recovery can be achieved. These results were used by Kaldate (2005) to reduce the amount of power applied per unit mass of ACFC in the vessel and provide a scale-up model of the ESA system. A comparison between experimental bench-scale VaPRRS and a pilot-scale VaPRRS was also completed as part of this research. Results from this effort demonstrated that both the bench-scale and pilot-scale ESA systems had removal efficiencies of MEK > 98%. The average electrical energy per unit mass of recovered liquid MEK was 4.6 kJ/g and 18.3 kJ/g for the bench unit and pilot unit, respectively. A new concentration controlled desorption device, known as ESA-Steady State Tracking (ESA-SS) desorption, was also designed and built as a bench-scale laboratory device as part of this research. This new system was demonstrated to operate over a wide range of conditions (i.e., type of organic vapor, concentration of organic vapor, ratio of desorption/adsorption cycle gas flow rates, fixed and dynamic desorption concentration set-points, constant and variable inlet concentration of organic vapor, batch and cyclic modes, and with dry and humid gas streams). It was shown that concentration of organic vapor that is generated during regeneration cycles can readily be controlled at concentration set-points for three organic compounds (MEK, acetone, and toluene). The average absolute errors (AAEs) were

Author: Roop Chand Bansal
Publisher: CRC Press
ISBN: 1420028812
Category : Science
Languages : en
Pages : 498

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High surface area, a microporous structure, and a high degree of surface reactivity make activated carbons versatile adsorbents, particularly effective in the adsorption of organic and inorganic pollutants from aqueous solutions. Activated Carbon Adsorption introduces the parameters and mechanisms involved in the activated carbon adsorption

Author: Jerry. R. Perrich
Publisher: CRC Press
ISBN: 1351077910
Category : Technology & Engineering
Languages : en
Pages : 260

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This volume is a guide to the state of the art of activated carbon adsorption technology as applied to wastewater treatment. This book surveys this body of knowledge and is a detailed description of current technology.