Thermochemical conversion of biomass in smouldering combustion across scales: The roles of heterogeneous kinetics, oxygen and transport phenomena

Huang, Xinyan; Rein, Guillermo

doi:10.1016/j.biortech.2016.01.027

Cited by 74 publications

(84 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…(6), shown below; the ideal gas law Eq. (7) closes the set of equations. Gpyro is also capable of doing 2D and 3D simulations.…”

Section: Governing Equationsmentioning

confidence: 99%

“…(12). The convective heat transfer coefficient at z = 0 m is set as h c0 = 1.52∆T 1/3 ≈ 10 W/m 2 K, which takes into account cooling by the atmosphere at top surface [7], and the mass transfer coefficient (h m0 ) 4…”

Section: Boundary Conditionsmentioning

confidence: 99%

“…The model of Huang et al [7] produces two types of char from the fuel: α-char and β-char. The α-char is obtained from cellulose pyrolysis while β-char is obtained from oxidative degradation of cellulose, but we assumed the properties of α-char and β-char to be the same [7]. For validation, the bulk density of cellulose and hemicellulose were measured experimentally [12].…”

Section: Physical Propertiesmentioning

confidence: 99%

See 2 more Smart Citations

Computational study of the effects of density, fuel content, and moisture content on smoldering propagation of cellulose and hemicellulose mixtures

Mulky

Niemeyer

2019

Proceedings of the Combustion Institute

View full text Add to dashboard Cite

Smoldering combustion plays an important role in forest and wildland fires. Fires from smoldering combustion can last for long periods of time, emit more pollutants, and be difficult to extinguish. This makes the study of smoldering in woody fuels and forest duff important. Cellulose, hemicellulose, and lignin are the major constituents in these type of fuels, in different proportions for different fuels. In this paper, we developed a 1-D model using the open-source software Gpyro to study the smoldering combustion of cellulose and hemicellulose mixtures. We first validated our simulations against experimentally obtained values of propagation speed for mixtures with fuel compositions including 100%, 75%, 50%, and 25% cellulose, with the remaining proportion of hemicellulose. Then, we studied the effects of varying fuel composition, density, and moisture content on smoldering combustion. We find that propagation speed of smoldering increased with decreases in density and increases in hemicellulose content, which we attribute to the role of oxygen diffusion. Propagation speed increased with moisture content for pure cellulose up to a certain limiting value, after which the propagation speed dropped by up to 70%. The mean peak temperature of smoldering increased with increases in hemicellulose content and density, and decreased with increasing moisture content.

show abstract

“…(6), shown below; the ideal gas law Eq. (7) closes the set of equations. Gpyro is also capable of doing 2D and 3D simulations.…”

Section: Governing Equationsmentioning

confidence: 99%

Section: Boundary Conditionsmentioning

confidence: 99%

Section: Physical Propertiesmentioning

confidence: 99%

See 1 more Smart Citation

Computational study of the effects of density, fuel content, and moisture content on smoldering propagation of cellulose and hemicellulose mixtures

Mulky

Niemeyer

2019

Proceedings of the Combustion Institute

View full text Add to dashboard Cite

show abstract

“…Previously, this model has been demonstrated to successfully simulate the ignition and extinction of peat fire and used to analyse the role of atmospheric oxygen concentration, MC and IC , 2016a, 2016b. The setup of the model will be briefly described here, and more details can be found in .…”

Section: Numerical Modelling Model Setupmentioning

confidence: 99%

“…The kinetic parameters of this Irish moss peat have been previously obtained by optimising the TG data in both inert and oxidative atmospheres (Huang and Rein 2016b) and are listed in Table 1.…”

Section: Parameter Selectionmentioning

confidence: 99%

Downward spread of smouldering peat fire: the role of moisture, density and oxygen supply

Huang

Rein

2017

Int. J. Wildland Fire

Self Cite

View full text Add to dashboard Cite

Abstract. Smouldering fires in peatland are different from the flames in wildland fires. Smouldering peat fire is slow, low-temperature and more persistent, releasing large amounts of smoke into the atmosphere. In this work, we experimentally and computationally investigate the vertical downward spread of smouldering fire in a column of 30 cm-tall moss peat under variable moisture content (MC) and bulk density. The measured downward spread rate decreases with depth and wet bulk density, and is ,1 cm h À1 equivalent to a carbon emission flux of 200 tonnes day À1 ha À1 . We observe that downward spread increases as MC increases substantially at least inside the range from 10 to 70%, which is not intuitive and goes against the trend observed for the horizontal spread in the same peat. We also conduct one-dimensional computational simulations to successfully reproduce the experimental observations. The analysis shows that the spread rate increases with MC and decreases with density because smouldering spread is controlled by the oxygen supply. The volume of the porous peat expands when absorbing water, which reduces the density of organic matter and decreases the heat release rate. This shows that the widely assumed conclusion that the spread rate of wildfire decreases with MC is not universal when applied to smouldering fires.

show abstract

Thermochemical conversion characteristics of a single wood pellet in a convective low‐temperature air environment

2020

View full text Add to dashboard Cite

Summary In this study, the thermochemical conversion process of a single wood pellet under low temperature (350°C‐650°C) isothermal heating is investigated to identify the outstanding low‐temperature ignition and combustion characteristics for heat generation, particularly during the preheating stages in the furnace. The thermal behavior of wood powder was analyzed using thermogravimetric/Fourier transform infrared spectroscopy. The suspended single pellet combustion phenomenon under a convective hot air stream was also explored. The results showed that the wood primarily decomposed in a range from 240°C to 520°C, and low‐temperature ignition was found at 293°C due to heterogeneous oxidation. For pellet combustion, an outstanding heterogeneous‐induced homogeneous combustion phenomenon occurred when the stream temperature was higher than 350°C. In contrast, the ignition mechanism shifted to volatile auto‐ignite mode at 650°C due to the interplay of fuel devolatilization and oxygen diffusion. The pellet temperature evolution was measured, and the results revealed a maximum heating rate of 6.61‐16.95 K/s under a stream temperature ranging from 350°C to 650°C. The weight loss evolution showed three stages during the entire heating process, and the average activation energy (13.12 kJ/mol) was obtained. Char combustion was found favorable to CO production for gaseous emissions, but the burning of volatiles tended to convert fuel into CO2. Finally, a simplified reaction scheme based on different onset temperatures, including pyrolysis, heterogeneous/homogeneous oxidation, and heterogeneous gasification was proposed to illustrate a potential thermochemical conversion route for further utilization.

show abstract

Thermochemical conversion of biomass in smouldering combustion across scales: The roles of heterogeneous kinetics, oxygen and transport phenomena

Cited by 74 publications

References 29 publications

Computational study of the effects of density, fuel content, and moisture content on smoldering propagation of cellulose and hemicellulose mixtures

Computational study of the effects of density, fuel content, and moisture content on smoldering propagation of cellulose and hemicellulose mixtures

Downward spread of smouldering peat fire: the role of moisture, density and oxygen supply

Thermochemical conversion characteristics of a single wood pellet in a convective low‐temperature air environment

Contact Info

Product

Resources

About