Design of Entrained-Flow and Moving-, Packed-, and Fluidized-Bed Sorption Systems:  Grain-Model Kinetics for Hot Coal-Gas Desulfurization with Limestone

Fenouil, Laurent A.; Lynn, Scott

doi:10.1021/ie950245y

Cited by 25 publications

(16 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To find the relationship between C 0 and X B at any point on the breakthrough curve, a mass balance on a differential axial cross-section element of the bed based on the method proposed by Fenouil and Lynn (1996) was used:…”

Section: Modeling Carbonation Kineticsmentioning

confidence: 99%

Direct capture of carbon dioxide from air via lime-based sorbents

Samari

Ridha²,

Manović

et al. 2019

Mitig Adapt Strateg Glob Change

View full text Add to dashboard Cite

Direct air capture (DAC) is a developing technology for removing carbon dioxide (CO 2 ) from the atmosphere or from low-CO 2 -containing sources. In principle, it could be used to remove sufficient CO 2 from the atmosphere to compensate for hard-to-decarbonize sectors, such as aviation, or even for polishing gas streams containing relatively low CO 2 concentrations. In this paper, the performance of lime-based sorbents for CO 2 capture from air in a fixed bed was investigated. The effects of sorbent type, particle diameter, air flow rate, and relative humidity on the breakthrough time, breakthrough shape, and global reaction rate over a series of capture and regeneration cycles were examined. The greatest reaction rates and conversions were obtained when the sorbents were pre-hydrated and inlet air was humidified to 55% relative humidity. Humidifying the air alone leads to axial carbonation gradients since there is competition between CO 2 and water with the available CaO. Negligible conversion, over the duration of the experiment, is obtained in a dry system without pre-hydration and humid air. A shrinking-core gas-solid reaction model was fitted to the breakthrough curves in order to estimate the surface reaction and effective diffusion constants. Although the surface reaction constants of the two sorbents were similar, the pelletized limestone had a greater effective diffusivity due to its greater porosity. At mild calcination conditions with air at 850°C, the pelletized particles maintained their activity over nine carbonation-calcination cycles with a conversion drop of only 9% points. However, calcination under oxy-fuel conditions (CO 2 at 920°C) reduced the pellet carbonation conversion from 81 to 59% and pore surface area from 12.01 to 3.20 m 2 /g after only 4 cycles. This research clearly shows that DAC using lime-based

show abstract

Section: Modeling Carbonation Kineticsmentioning

confidence: 99%

Direct capture of carbon dioxide from air via lime-based sorbents

Samari

Ridha²,

Manović

et al. 2019

Mitig Adapt Strateg Glob Change

View full text Add to dashboard Cite

show abstract

“…To use gas−solid reaction models in the modeling of sulfur retention in moving, packed, and fluidized bed sorption systems, it is necessary to know the sulfidation kinetics in the broad range of particle sizes that could be employed . Previous work on sulfidation reaction has been limited to representing conversion versus time data in a narrow range of particle sizes.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of H₂S Reaction with Calcined Calcium-Based Sorbents

1998

View full text Add to dashboard Cite

Sulfidation experiments at atmospheric pressure in a thermogravimetric analyzer were performed with two calcined limestones and a fully calcined dolomite at temperatures between 450 and 700 °C and with sorbent particle sizes between 0.4 and 1.6 mm. The effects of reaction temperature, sorbent particle size, and H2S concentration were analyzed. The sulfidation rate of the dolomite and a limestone increased with temperature in all of the ranges tested. However, the sulfidation rate of the other limestone increased with temperature until 600 °C and was nearly constant from this temperature. The temperature effect on the conversion versus time curves diminished with increasing particle size. At low temperatures (<500−550 °C) the sulfidation rate did not depend on sorbent particle size. On the other hand, at temperatures above 500−550 °C the sulfidation rate increased with decreasing sorbent particle size due to the effect of the intraparticle diffusion. This finding was in agreement with the SEM-EDX sulfur distribution profiles measured in partially sulfided sorbent particles. The sulfidation rate increased when the H2S pressure was raised, and a reaction order in H2S of 1 could adequately describe the sulfidation reaction of the sorbents. The changing grain size model proposed by Georgakis et al. together with the molecular scale hypotheses of Attar and Dupuis was used to determine the kinetic parameters of the reaction and to test its ability to predict the data for the sulfidation reaction over a broad range of particle sizes and temperatures. Good agreement between measured and predicted conversion time curves and sulfur distributions inside the particles was observed. The values of the activation energies varied from 29.1 to 56.5 kJ mol-1 to calculate the chemical reaction rate constant, k s, and from 154.6 to 217.5 kJ mol-1 to calculate the product layer diffusion coefficient, D s. Analysis of the kinetic parameters showed that the resistance due to the chemical reaction on the overall reaction rate increased in relation to the resistance of the H2S diffusion through the product layer with increasing the reaction temperature. This effect was very similar for the two limestones and higher than for the dolomite.

show abstract

“…7 were also verified with the conversion profiles experimentally obtained in the fixed-bed reactor at a time previous to the breakthrough point, when the transition zone was in an intermediate location of the bed. On the other hand, the conversion profiles were also obtained from the breakthrough curves in fixed-bed using the equation proposed by Fenouil and Lynn [6], modified to consider X e , which gave the relationship between C H 2 S and X at any point of the transference zone . The operating conditions used were the given in E13 with a particle size of +1.6-2.0 mm and a reacting time of 60 min for dolomite and "Sástago" limestone, and 85 min for "Omyacarb" limestone.…”

Section: Application To the Design Of A Moving-bedmentioning

confidence: 99%

“…and Lynn [6] modelled the retention of H 2 S in fixed-or moving-beds at pressures between 0.1 and 3 MPa. The H 2 S removal in fixed-or moving-bed reactors allows the almost complete utilization of the sorbent, reaching H 2 S concentrations at the outlet close to the equilibrium.…”

Section: Introductionmentioning

confidence: 99%

HS retention with Ca-based sorbents in a pressurized fixed-bed reactor: application to moving-bed design

Adánez

Abad

Garcı́a-Labiano

et al. 2005

Fuel

View full text Add to dashboard Cite

The H 2 S retention with Ca-based sorbents in a pressurized fixed-bed reactor (1 MPa) has been analyzed, obtaining the breakthrough curves with a dolomite and two different limestones, different particle size (+0.8-1.0 mm, +1.25-1.6 mm, and +1.6-2.0 mm), and both at calcining (1173 K) and non-calcining conditions (1123 K). The effect of the stoichiometric time in the breakthrough curves has been analyzed varying the bed length, the gas velocity and the sorbent fraction in the bed. From these results, the conversion and H 2 S concentration profiles in the transition zone and the length of unused bed (LUB) have been determined. H 2 S retention in fixed-bed until concentration close to the given by the thermodynamic equilibrium was obtained using dolomite or limestone at calcining conditions, and dolomite at non-calcining conditions. The results of H 2 S retention in a fixed-bed reactor has been applied to the calculus of the minimum height of a countercurrent moving-bed reactor to obtain the maximum H 2 S retention with the minimum amount of sorbent. A mathematical model was developed to predict the experimental results obtained in the fixed-bed reactor, which was also valid for the design of countercurrent moving-bed reactors for gas desulphurization.

show abstract

Design of Entrained-Flow and Moving-, Packed-, and Fluidized-Bed Sorption Systems: Grain-Model Kinetics for Hot Coal-Gas Desulfurization with Limestone

Cited by 25 publications

References 19 publications

Direct capture of carbon dioxide from air via lime-based sorbents

Direct capture of carbon dioxide from air via lime-based sorbents

Kinetics of H₂S Reaction with Calcined Calcium-Based Sorbents

HS retention with Ca-based sorbents in a pressurized fixed-bed reactor: application to moving-bed design

Contact Info

Product

Resources

About

Design of Entrained-Flow and Moving-, Packed-, and Fluidized-Bed Sorption Systems: Grain-Model Kinetics for Hot Coal-Gas Desulfurization with Limestone

Cited by 25 publications

References 19 publications

Direct capture of carbon dioxide from air via lime-based sorbents

Direct capture of carbon dioxide from air via lime-based sorbents

Kinetics of H2S Reaction with Calcined Calcium-Based Sorbents

HS retention with Ca-based sorbents in a pressurized fixed-bed reactor: application to moving-bed design

Contact Info

Product

Resources

About

Kinetics of H₂S Reaction with Calcined Calcium-Based Sorbents