A pore-structure dependent kinetic adsorption model for consideration in char conversion – Adsorption kinetics of CO2 on biomass chars

Wedler, Carsten

doi:10.1016/j.ces.2020.116281

Cited by 14 publications

(23 citation statements)

References 54 publications

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“…This differentiation is a major advantage of the NLDFT method, as it allows for the consideration of different pore regimes in mass transfer models. 6,8 On the basis of the low values found for the meso-to macropore regime, one might assume that no mesopores are present. However, CO 2 is not suitable for the analysis of meso-or macropores, since pore filling mainly takes place in smaller pores.…”

Section: Resultsmentioning

confidence: 99%

“…During pyrolysis, gasification, and oxidation of solid fuels, the porous structure of the fuel changes. Besides fuel-specific factors, this effect depends on process temperature, gas atmosphere, and heating rate. − To understand and model ongoing conversion subprocesses, such as intraparticle mass transfer or devolatilization, detailed knowledge on the pore structure of the char is inevitable. − Because the pore surface in micro-, meso-, and macropores can develop independently, information about the development of the different pore regimes is desirable. Especially for biomass fuels, which generally have higher volatile contents than coal, significant changes in the pore structure can occur during conversion …”

Section: Introductionmentioning

confidence: 99%

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Micropore Analysis of Biomass Chars by CO₂ Adsorption: Comparison of Different Analysis Methods

Wedler

2021

Energy Fuels

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Detailed knowledge of the pore structure evolution of fuel chars is essential for a sound description of the conversion process. The analysis of the chars by N 2 adsorption at 77.36 K according to the theory of Brunauer, Emmett, and Teller has been established as a standard in pore analysis. However, at this low temperature, the diffusion of N 2 in micropores is limited, and N 2 is therefore not suitable for an analysis of the microporous structure. For micropore analysis, CO 2 adsorption at 273.15 K can be used instead since CO 2 shows no limitation with regard to diffusion into micropores. For the evaluation of the CO 2 adsorption data, various analysis methods are available, which are commonly used in the literature. However, no consistent method has been established in the literature to determine micropore volume and surface area, and the used methods are often not described in a traceable way, which makes a comparison of results based on different analysis approaches hardly possible. To show and discuss the differences, CO 2 adsorption experiments were conducted in this study for four biomass chars. The data were analyzed according to Dubinin−Astakhov (DA), Dubinin−Radushkevich (DR), and nonlocal density functional theory (NLDFT) analysis. Because DA and DR are only able to determine the pore volume of the chars, an additional correlation is required to determine the surface area. Three different correlations for the relation between pore volume and surface area were compared within this study as well.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Micropore Analysis of Biomass Chars by CO₂ Adsorption: Comparison of Different Analysis Methods

Wedler

2021

Energy Fuels

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“…m 01 and V 01 are mass and volume, respectively, of the additionally lifted parts when switching from ZP to MP1: the sample (s), the sample container (c), the lifting rod (lr), and the lifting cage (lc). The volume of the sample V s was determined by helium buoyancy measurements at pressures from (1 to 5) MPa and a temperature of 348 K, for which the detailed procedure is described elsewhere [21]. The temperature of 348 K was chosen to minimize the possible adsorption of helium on the sample [22].…”

Section: Gravimetric Sorption System and Measurement Proceduresmentioning

confidence: 99%

“…As shown in Eq. (13), the position remains constant in MP1 during the kinetic measurements and W 0,eq is only recorded at the equilibrium state [21]. By rearranging the time-dependent mass balance in Eqs.…”

Section: Adsorption Data Evaluationmentioning

confidence: 99%

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Adsorption kinetics and equilibria of two methanol samples with different water content on activated carbon

Rösler

Wedler

2021

Adsorption

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To investigate the influence of fluid purity on the adsorption properties, adsorption kinetics and adsorption equilibria of two methanol samples with different water content on an activated carbon were studied. The purity of the methanol samples was 98.5% and 99.9%. Measurements were conducted at 298 K and 318 K using a magnetic suspension balance and cover a wide p/p0 range. To determine effective diffusion time constants and mass transfer coefficients, adsorption kinetics were evaluated using an isothermal and a nonisothermal Fickian diffusion model, and the linear driving force model. The pressure dependence of the kinetic parameters was studied and discussed. A small influence of sample purity on the adsorption equilibria was observed, as the purer methanol sample showed slightly higher equilibrium loadings than the less pure sample. However, significantly faster adsorption kinetics were observed for the purer sample at all temperature and pressure conditions. Compared to the less pure sample, the determined effective diffusion time constants and the mass transfer coefficients were up to 98% and 35% higher, respectively.

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The Magnetic Suspension Balance: 40 Years of Advancing Densimetry and Sorption Science

Yang,

Kleinrahm,

McLinden

et al. 2023

Int J Thermophys

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This paper reviews the 40-year evolution and application of the magnetic suspension balance (MSB) and discusses some challenging issues of the technique. An MSB, as defined herein, is a magnetic suspension coupling (MSC) connected to an analytical balance. With an MSC, an object can be weighed in a different environment than the balance itself, making it possible for contactless weighing. Over the past 40 years, the MSB has been commonly used in research areas requiring accurate object weighings, notably gas density measurements by MSB-based densimeters and gas adsorption measurements by MSB-based sorption analyzers. More than 15 MSB-based densimeters have been built to date; these are generally called two-sinker densimeter and single-sinker densimeter. They have produced highly accurate density data of many pure fluids and fluid mixtures. These data serve as the basis for the development of reference equations of state, which play an essential role in various industrial and scientific areas. Moreover, such systems are central to the metrology program of many countries. The MSB technique is also very successful in adsorption science: more than 85 MSB-based sorption analyzers have been set up in over 20 countries. The number of new MSB-based sorption analyzers, and peer-reviewed publications resulting from them, are both increasing exponentially since 2004. They have produced highly reliable gas adsorption data at high pressures for many applications, mainly in the energy and environmental sectors. Although further development of innovative instruments based on the MSB is threatened by the proprietary nature of MSB technology, the development will continue, e.g., toward cryogenic measurements and a more compact design.

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A pore-structure dependent kinetic adsorption model for consideration in char conversion – Adsorption kinetics of CO2 on biomass chars

Cited by 14 publications

References 54 publications

Micropore Analysis of Biomass Chars by CO₂ Adsorption: Comparison of Different Analysis Methods

Micropore Analysis of Biomass Chars by CO₂ Adsorption: Comparison of Different Analysis Methods

Adsorption kinetics and equilibria of two methanol samples with different water content on activated carbon

The Magnetic Suspension Balance: 40 Years of Advancing Densimetry and Sorption Science

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A pore-structure dependent kinetic adsorption model for consideration in char conversion – Adsorption kinetics of CO2 on biomass chars

Cited by 14 publications

References 54 publications

Micropore Analysis of Biomass Chars by CO2 Adsorption: Comparison of Different Analysis Methods

Micropore Analysis of Biomass Chars by CO2 Adsorption: Comparison of Different Analysis Methods

Adsorption kinetics and equilibria of two methanol samples with different water content on activated carbon

The Magnetic Suspension Balance: 40 Years of Advancing Densimetry and Sorption Science

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Product

Resources

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Micropore Analysis of Biomass Chars by CO₂ Adsorption: Comparison of Different Analysis Methods

Micropore Analysis of Biomass Chars by CO₂ Adsorption: Comparison of Different Analysis Methods