A numerical model for combustion of bubbling thermoplastic materials in microgravity

Butler, Kathlyn M

doi:10.6028/nist.ir.6894

Cited by 15 publications

(18 citation statements)

References 41 publications

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“…In frames 837-838 and 872-878, the collapse of a large bubble that covers the entire volume of the liquid phase can be seen. A bubble of this size indicates a high rate of bubble coalescence which forms one large bubble that grows until the internal energy is sufficient to overcome the viscous and surface energy barrier to explode [74,75]. After 260 • C (4E), the liquid phase swelling slows down, indicating a decrease in gas generation and an increase in viscosity by polymerization reactions [24,25].…”

Section: Behavior Of Milled Wood Lignin During Pyrolysismentioning

confidence: 97%

Identification of the fractions responsible for morphology conservation in lignocellulosic pyrolysis: Visualization studies of sugarcane bagasse and its pseudo-components

Montoya

Pecha

Janna

et al. 2017

Journal of Analytical and Applied Pyrolysis

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a b s t r a c tPyrolysis of lignocellulosic materials typically form carbonaceous residues (chars) with structures similar to the starting material. However, previous studies reported in the literature have shown that fast pyrolysis of cellulose and lignin form a molten intermediate liquid resulting in chars with smooth surfaces and evidences of intense bubbling. The fraction responsible for morphology conservation during pyrolysis is not known. In this article, pyrolysis visualization studies were carried out with a fast camera on cellulose, xylan, Organosolv lignin (OL), milled wood lignin (MWL), and lignocellulosic sugarcane bagasse to identify the component responsible for morphological conservation. The materials were heated using a modified Pyroprobe with measured sample heating rates close to 100 • C/s. Our studies confirm that cellulose, lignin, and deashed xylan are completely transformed into an intermediate liquid; the intensity of bubbling for lignin was far superior that of cellulose. Xylan as received, however, only forms a small amount of intermediate liquid; it does not fully melt and maintains its general shape during pyrolysis. These results suggest that the presence of mineral matter is critical for lignocellulosic materials to retain their original morphology. We repeated the studies on raw bagasse and acid washed bagasse. The raw bagasse retains its morphology; the acid washed bagasse shrank dramatically, but was not completely converted into a liquid. Our results suggest that in addition to hemicellulose with the presence of ash, other biomass fractions or the different temperatures at which the different fractions melt and solidify could also be contributing to maintain the structure of the lignocellulosic material during pyrolysis.

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Section: Behavior Of Milled Wood Lignin During Pyrolysismentioning

confidence: 97%

Identification of the fractions responsible for morphology conservation in lignocellulosic pyrolysis: Visualization studies of sugarcane bagasse and its pseudo-components

Montoya

Pecha

Janna

et al. 2017

Journal of Analytical and Applied Pyrolysis

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“…The model predicted a MLR that was approximately constant with time, whereas experimental data showed an increasing mass loss rate. A more recent model [54] includes a more detailed description of bubbling, but the author concludes that a better representation of the bursting process is still needed.…”

Section: Special Topics: Melting Bubbling and Related Phenomenamentioning

confidence: 99%

“…One challenge is simulating the mechanism through which pyrolysate vapors generated in-depth escape from the solid. Although it is usually assumed that the vapors instantaneously escape with no flow resistance, a few studies have included the effect of bubbling, ranging from simplified [48] to detailed [52][53][54] treatments.…”

Section: Comprehensive Pyrolysis Models: Thermoplasticsmentioning

confidence: 99%

Generalized pyrolysis model for combustible solids

Lautenberger

Fernandez-Pello

2009

Fire Safety Journal

302

259

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This dissertation presents the derivation, numerical implementation, and verification/validation of a generalized model that can be used to simulate the pyrolysis, gasification, and burning of a wide range of solid fuels encountered in fires. The model can be applied to noncharring and charring solids, composites, intumescent coatings, and smolder in porous media. Care is taken to make the model as general as possible, allowing the user to determine the appropriate level of complexity to include in a simulation. The model considers a user-specified number of gas phase and condensed phase species, each having its own temperature-dependent thermophysical properties.Any number of heterogeneous (gas-solid) or homogeneous (solid-solid or gas-gas) reactions can be specified. Both in-depth radiation transfer through semi-transparent media and radiation transport across pores are considered. Volume change (surface regression or swelling/intumescence) is handled by allowing the size of grid points to change as dictated by mass conservation. All volatiles generated inside the solid escape to the ambient with no resistance to mass transfer unless a pressure solver is invoked; the resultant flow of volatiles is then calculated according to Darcy's law. A gas phase 2 convective-diffusive solver can be invoked to determine the composition of the volatiles.Oxidative pyrolysis is simulated by modeling diffusion of oxygen from the ambient into the pyrolyzing solid where it may participate in reactions. Consequently, the mass flux and composition of volatiles escaping from the solid can be calculated. To aid in determining the required input parameters, the model is coupled to a genetic algorithm that can be used to estimate the required input parameters from bench-scale fire tests or thermogravimetric analysis.

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“…High-density polyethylene is, by definition, any polyethylene with a solid density of at least 9.41 g/cm 3 . The density of polyethylene melts is around 20 % less than this value.…”

Section: Densitiesmentioning

confidence: 99%

“…For the purposes of comparing their kinetic pyrolysis models to experimental GC-MS data, Faravelli et al [2] developed a simple bubbling loss model. Butler [3] developed models for bubbling in combusting thermoplastic materials and incorporated these models into numerical simulations.…”

Section: Introductionmentioning

confidence: 99%

Pyrolysis and Devolatilization of High-Density Polyethylene

Bruns¹,

Ezekoye²

2011

Fire Safety Science - Proceedings of the 10th International Sym

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A simple model for combined pyrolysis and devolatilization of high-density polyethylene (HDPE) is developed and studied. The model parameters are estimated from available literature data, and the resulting predictions are compared with a single thermogravimetric experiment. It is found that the bubble loss model makes a better prediction than a critical carbon number loss model. As expected, the bubble loss model is seen to lose validity when the sample becomes predominantly composed of volatile species.

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A numerical model for combustion of bubbling thermoplastic materials in microgravity

Cited by 15 publications

References 41 publications

Identification of the fractions responsible for morphology conservation in lignocellulosic pyrolysis: Visualization studies of sugarcane bagasse and its pseudo-components

Identification of the fractions responsible for morphology conservation in lignocellulosic pyrolysis: Visualization studies of sugarcane bagasse and its pseudo-components

Generalized pyrolysis model for combustible solids

Pyrolysis and Devolatilization of High-Density Polyethylene

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