Devolatilization kinetics of woody biomass at short residence times and high heating rates and peak temperatures

Johansen, Joakim Myung; Gadsbøll, Rasmus Østergaard; Thomsen, Jesper Skovhus; Jensen, Peter Arendt; Glarborg, Peter; Ek, Paul; Martini, Nikolai De; Mancini, Marco; Weber, Roman; Mitchell, Reginald E.

doi:10.1016/j.apenergy.2015.09.091

Cited by 36 publications

(50 citation statements)

References 49 publications

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“…The current work follows the methodology developed earlier by the authors. 10 High temperature conditions are established by feeding the solid fuel into a laminar ow reactor (LFR) 10,22,23 heated by a CH 4 /H 2 understoichiometric pilot ame. This conguration facilitated adiabatic ame temperatures of 14051667 K and particle heating rates on the order of The low ash fraction and the high volatility of some of the inorganic species, such as alkali metals and halides, make it dicult to use ash as a tracer.…”

Section: Methodsmentioning

confidence: 99%

“…To circumvent bias from the release of volatile ash components, we again use calcium as a tracer. 10 The degree of conversion is calculated by closing a Ca mass balance on the collected char:…”

Section: Methodsmentioning

confidence: 99%

“…The gaseous ux away from the particle is detrimental to convective heat transfer, but the eect on the particle temperature is comparatively small. 24,25 The detailed model specication including inlet and boundary conditions is described in the original work of Johansen et al 10 The simulations of the reacting particles are coupled to the experiments by iteratively updating the devolatilization kinetics applied in the CFD simulations, until the calculated mass loss agrees with the measurements. The devolatilization is described by a single rst order reaction (SFOR) with an Arrhenius type rate expression:…”

Section: Methodsmentioning

confidence: 99%

“…The applied kinetics appear to capture the rapid conversion well for all four fuels. Figure 2: Comparison of experimental data and modeling predictions for the degree of devolatilization for the four fuels for the condition with an adiabatic ame temperature of 1566 K. The results for parent pine were drawn from Johansen et al 10 An Arrhenius plot comparing the rate constants for the four fuels is shown in Fig. 3.…”

Section: Devolatilization Kineticsmentioning

confidence: 99%

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High Heating Rate Devolatilization Kinetics of Pulverized Biomass Fuels

et al. 2018

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Devolatilization kinetics for the biomass fuels miscanthus, leached miscanthus, and KCl doped pinewood were determined at high heating rates (∼ 10 5 K • s −1), high peak temperatures (14051667 K), and short residence times (< 70 ms). The particle temperature and residence time distribution were obtained from CFD simulations. The measured devolatilization rates, formulated in terms of single rst order reactions, were signicantly faster than data reported in literature. This dierence was attributed partly to the fast heating rate/high temperature conditions of the present study, and partly to a more accurate estimate of the particle temperature. The current results indicate that neither the biomass type nor the alkali content of the biomass has a signicant impact on the devolatilization rate under the investigated conditions. The development in the particle morphology was studied by electron microscopy as each fuel underwent partial to full conversion. The char yields ranged from 0.02 (leached 1 miscanthus) to 0.11 (KCl doped pinewood), indicating that even during fast heating the biomass alkali content promotes char formation.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Devolatilization Kineticsmentioning

confidence: 99%

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High Heating Rate Devolatilization Kinetics of Pulverized Biomass Fuels

et al. 2018

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“…Johansen et al [21] developed a model to describe specifically the fast devolatilization of woody biomass fuels. A laboratory-scale experiment in a laminar flow reactor was used to derive the kinetics, which was implemented into a CFD model of a bench-scale equipment to iterate the exact temperature profile of the fuel particles in those conditions.…”

Section: Introductionmentioning

confidence: 99%

Determining the mass-related reaction effectiveness factor of large, nonspherical fuel particles for bridging between intrinsic and apparent combustion kinetics

Szűcs

Szentannai

2019

J Therm Anal Calorim

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The utilization of challenging solid fuels in the energy industry is urged by environmental requirements. The combustion kinetics of these fuel particles differs markedly from that of pulverized coal, mainly because of their larger sizes, irregular (nonspherical) shapes, and versatile internal pore structures. Although the intrinsic reaction kinetic measurements on very small amounts of finely ground samples of these particles are mostly available, a bridge toward their apparent reaction modeling is not evident. In this study, a method is introduced to build this bridge, the goodness of which was proved on the example of an industrially relevant biofuel. To do this, the results of a macroscopic combustion measurement with real samples in a well-modelable environment have to be used, and for considering some not negligible effects, 3D CFD modeling of the experimental environment is also to be applied. The outcome is the mass-related reaction effectiveness factor as a function of the rate of conversion. This variable can be considered as the active fraction of the entire particle mass on its periphery, and it can be used as the crucial element in modeling the combustion process of the same particle under other circumstances by including the actual boundary conditions. Another advantage of this method is its covering inherently the entire combustion process (water and volatile release, and char combustion) and also its applicability for reactors utilizing bigger particles like fluidized bed combustors.

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