Modelling and experimental verification of physical and chemical processes during pyrolysis of a large biomass particle

Chan, Wai-Chun Ricky; Kelbon, Marcia; Krieger, Barbara B.

doi:10.1016/0016-2361(85)90364-3

Cited by 477 publications

(316 citation statements)

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“…A characteristic time scale analysis similar to that performed by Chan et al [12] aids in identifying the dominant processes occurring during the drying and torrefaction of a single particle and is summarized in Table 1. Although, the time scales do not represent the magnitude of the driving forces behind such processes (i.e temperature gradient) they allow the identification of the rate controlling mechanisms.…”

Section: Characteristic Time Scale Analysismentioning

confidence: 99%

“…These include the i) first order kinetic evaporation model [12,33,36,[41][42][43], ii) equilibrium model [29,[44][45][46], and iii) a constant temperature model (also known as the heat sink model) [34,39,40,[47][48][49]. The first order kinetic approach is a simplified approach which treats the evaporation rate as a thermally activated process described with a first order Arrhenius rate equation.…”

Section: Dryingmentioning

confidence: 99%

“…In order to examine these phenomena, robust coupled transient models describing the transport, kinetics, and thermochemistry are required. Numerous 1D and 2D physico-chemical models exist in the literature that describe single particle pyrolysis at high temperatures (400-700 ○ C) [12][13][14][15][16]. However, compared to torrefaction, pyrolysis at these high temperature results in partial to complete devolatilization (70-90 wt%) and different thermal degradation pathways are expected.…”

Section: Introductionmentioning

confidence: 99%

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Modeling kinetics-transport interactions during biomass torrefaction: The effects of temperature, particle size, and moisture content

Bates

Ghoniem

2014

Fuel

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ABSTRACT:A comprehensive one-dimensional model accounting for the effects of heat and mass transfer, chemical kinetics, and drying was developed to describe the torrefaction of a single woody biomass particle. The thermochemical sub-models depend only on previously determined or measured characteristics, avoiding the use of fitting or tuning parameters and enabling a rigorous energy balance of the process. Moreover, a high temperature drying sub-model is introduced which overcomes the difficulties associated with existing approaches to give physically consistent results, smooth implementation, and numerical stability. The particle model was validated against experimental data from the literature for intraparticle temperature profiles, particle mass and energy yields over a range of particle sizes and reaction temperatures. The modeling results describe well the three distinct stages observed during the torrefaction of large particles including the heatup, drying, heat release due to exothermic reactions resulting in thermal overshoot, followed by thermal equilibrium where conversion is governed by mass loss kinetics. The nonlinear effects of particle size, temperature, moisture content, and residence time on the mass and energy yields are quantified and explained. Larger particles exhibit a significant internal temperature gradient and strong temperature overshoot especially at the centerline. The magnitude of the overshoot is a function of the conductivity, particle size, and average heat release rate. Because of the rise in the reaction rate, higher temperatures increase the sensitivity of the process to particle size. Due to the dependence of drying rate on heat transfer limitations, the sensitivity of torrefaction to initial moisture content increases strongly with particle size. Highlights: 1D coupled model describes the dynamics of drying and torrefaction of a single particle  Model predicts particle temperature overshoot, elemental, and energy balance  Validated against single particle experimental results from literature  Larger particles convert more non-uniformly with higher thermal overshoot.  Higher temperatures and increased moisture content exacerbate particle size effects

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Section: Characteristic Time Scale Analysismentioning

confidence: 99%

Section: Dryingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Modeling kinetics-transport interactions during biomass torrefaction: The effects of temperature, particle size, and moisture content

Bates

Ghoniem

2014

Fuel

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“…The kinetic scheme as shown in fig.1 describes the process of pyrolysis (primary and secondary) which involves thermal decomposition of biomass into gases, tar (liquid product of biomass pyrolysis, known as bio-oil or pyrolysis oil) and char, and the tar further decompose into char and gases This two-stage parallel reaction model of biomass pyrolysis has previously been used by other researchers (Shafizadeh and Chin, 1977;Thurner and Mann, 1981;Chan et al, 1985;Font et al, 1990, Di Blasi ;Janse et al, 2000, Yang et al, 2006. According to the twostage parallel reaction model, the biomass undergoes thermal degradation according to primary reactions (k1; k2; k3) giving gas, tar and char as products.…”

Section: Kinetic Models and Solutionsmentioning

confidence: 99%

Theoretical Investigations of the Effects of Isothermal and Non-isothermal Heating Conditions on the Pyrolysis Kinetics of Biomass Particle

Sobamowo¹,

Ojolo²,

Kehinde³

et al. 2016

AJBB

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There has been a growing interest in renewable energy sources from various part of the world over the past decades. One of the promising alternatives to fossil fuels is biomass and in all the common technologies of its conversion, pyrolysis is present atleast as a first stage of the conversion process. As part of the scientific studies and understanding of this very important process in the thermochemical conversion of the solid fuel, the development of good mathematical models which in consequent leads to the design of pyrolysis reactors and biomass gasifiers is paramount. However, due to the complexities of the biomass reaction scheme, the pyrolysis of biomass is generally modeled on the basis of apparent kinetics. Moreover, most of the past works were based on the overall pyrolysis kinetics, and studies concerning pyrolysis products are much less common. Therefore, this work presents the analytical solutions of the kinetics of pyrolysis of biomass particle under non-isothermal and isothermal heating conditions. The developed models were used to investigate the effects of heating conditions and heating rates on the pyrolysis of wood products. The comparison of the simulated results with the available results reported in literatures show good agreements were found. This work could be used in predetermining the biomass products concentrations under different heating conditions and the estimating the optimum parameters in the pyrolysis of biomass and in the design of some pyrolysis reactors/units.Keywords: Biomass particle; Pyrolysis; Kinetics; Analytical solutions; Isothermal temperature and NonIsothermal heating rates Nomeclature A1; A2; A3; A4; A5 frequency factor, 1/s C concentration, kg/m 3 E activation energy, J/mol

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“…Radiative power has long been seen as a way to achieve high heating rates [23,1,[24][25][26][27]. Recently, solar pyrolysis has been studied in order to assess produced char properties [13].…”

Section: Introductionmentioning

confidence: 99%

Biomass gasification under high solar heat flux: Experiments on thermally thick samples

Pozzobon

Salvador

Bézian

2016

Fuel

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gasification under high solar heat flux: Experiments on thermally thick samples. Fuel, Elsevier, 2016, 174, pp.257-266 Beech wood is exposed to radiative heat flux higher than 1000 kW/m 2 . Sample geometry evolves dramatically. Temperature higher than 1500°C are reached. Tar yield is lowered by thermal cracking and steam reforming. Initial moisture content plays key role in the biomass behavior. t r a c tIn this study, thermally thick samples of beech wood are exposed to radiative heat flux above 1 MW/m 2 (1000 suns). It was motivated by the fact that concentrated solar energy allows to achieve temperatures higher than 1200 °C where char gasification, tar thermal cracking and tar steam reforming can take place. It is achieved using a new experimental device made of an artificial sun and a new reaction chamber, that monitors the sample mass throughout a run and can trap the produced tars using a liquid nitrogen cooled tar condensing device. Thanks to this experimental device, it is possible to compute the average wood consumption rate as well as drying water, char, gas and tar production rates. The produced light gases are also analyzed using microGC. Furthermore, a radiometer is used to monitor surface temperature, which is around 1500 °C. First, a new behavior has been highlighted. Under high radiative heat flux, a char crater which mirrored incident heat flux distribution, is formed inside of the sample. Then, using this device, the impact of two major parameters was tested: wood fiber orientation relative to the solar flux and initial moisture content. Wood fiber orientation (end grain and with the grain) was shown to only have a minor impact on the production rates, gas composition and crater formation. Three initial moisture contents (0, 9 and 55 %wb) were tested. It was shown that increasing the sample moisture leads to direct drying steam gasification of the char produced by the pyrolysis. Moreover, steam also promotes tar steam reforming and therefore decreases the tar yield. Finally, form an energetic point of view, the dry samples can achieve an energetic conversion efficiency of 90%, capturing up to 72% of the incident solar power in chemical form.

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Modelling and experimental verification of physical and chemical processes during pyrolysis of a large biomass particle

Cited by 477 publications

References 24 publications

Modeling kinetics-transport interactions during biomass torrefaction: The effects of temperature, particle size, and moisture content

Modeling kinetics-transport interactions during biomass torrefaction: The effects of temperature, particle size, and moisture content

Theoretical Investigations of the Effects of Isothermal and Non-isothermal Heating Conditions on the Pyrolysis Kinetics of Biomass Particle

Biomass gasification under high solar heat flux: Experiments on thermally thick samples

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