Heat transfer and kinetics in the low temperature pyrolysis of solids

Pyle, D.L.; Zaror, Claudio A.

doi:10.1016/0009-2509(84)80140-2

Cited by 328 publications

(248 citation statements)

References 9 publications

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“…These models will be discussed below in more detail. Similar models with more or different assumptions describing the volatilization of a solid were published by, for instance, Villermaux et al (1986) and Pyle et al (1984).…”

Section: Modeling Of the Influence Of Heat Transfer On The Pyrolysis mentioning

confidence: 83%

“…Because of the very large external heat transfer coefficient in the screen heater possible heat transfer resistances will be situated inside the polymer particle. The pyrolysis number Py (Pyle et al, 1984) represents the ratio of the time constant for a first order pyrolysis reaction and the time constant for unsteady internal heat conduction for spheres and is given by…”

Section: Screen Heater Experimentsmentioning

confidence: 99%

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Examination and Evaluation of the Use of Screen Heaters for the Measurement of the High Temperature Pyrolysis Kinetics of Polyethene and Polypropene

Westerhout

Balk

Meijer

et al. 1997

Ind. Eng. Chem. Res.

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A screen heater with a gas sweep was developed and applied to study the pyrolysis kinetics of low density polyethene (LDPE) and polypropene (PP) at temperatures ranging from 450 to 530°C. The aim of this study was to examine the applicability of screen heaters to measure these kinetics. On-line measurement of the rate of volatiles formation using a hydrocarbon analyzer was applied to enable the determination of the conversion rate over the entire conversion range on the basis of a single experiment. Another important feature of the screen heater used in this study is the possibility to measure pyrolysis kinetics under nearly isothermal conditions. The influence of the mixing process in the gas phase on the measured hydrocarbon concentration versus time curve was assessed and it was demonstrated that the residence time distribution of the gas phase, which has to be accounted for to correctly interpret the experiments, becomes the limiting factor when measuring pyrolysis kinetics at high temperatures and not the heat transfer rate. With this type of apparatus, pyrolysis reactions with a first order rate constant lower than 2 s -1 can be studied, which implies that the pyrolysis kinetics of the forementioned polymers could be determined at temperatures below 530°C. The kinetic constants for LDPE and PP pyrolysis were determined, using a first order model to describe the conversion rate in the 70-90% conversion range and the random chain dissociation model for the entire conversion range. Our experiments revealed that both LDPE and PP posses the same conversion rate, which is unexpected behavior since PP should be more sensitive to thermal degradation than LDPE. A comparison of the thermo gravimetric analyzer results with those obtained with the screen heater indicates an enhancement of the pyrolysis kinetics in the latter equipment. Several hypothesis were tested to explain this phenomenon and led to the suspicion that the discrepancy is possibly due to the effect of the electrical current passing through the screen on the pyrolysis reaction, although most of the evidence for this hypothesis is indirect. Screen heaters can therefore not be used in this configuration to measure the pyrolysis kinetics, if this hypothesis is correct. In addition to the experimental work two single particle models have been developed which both incorporate a mass and a (coupled) enthalpy balance, which were used to assess the influence of internal and external heat transfer processes on the pyrolysis process. The first model assumes a variable density and constant volume during the pyrolysis process, whereas the second model assumes a constant density and a variable volume. An important feature of these models is that they can accommodate kinetic models for which no analytical representation of the pyrolysis kinetics is available. Model calculations revealed that heat transfer limitations were not important during the pyrolysis experiments performed in the screen heater and could not explain the forementioned results.

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Section: Modeling Of the Influence Of Heat Transfer On The Pyrolysis mentioning

confidence: 83%

Section: Screen Heater Experimentsmentioning

confidence: 99%

Examination and Evaluation of the Use of Screen Heaters for the Measurement of the High Temperature Pyrolysis Kinetics of Polyethene and Polypropene

Westerhout

Balk

Meijer

et al. 1997

Ind. Eng. Chem. Res.

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“…Also, the study of biomass gasification processes requires a detail understanding of the pyrolysis process and the behaviour of the biomass particles in the reacting medium. On carrying out such studies, it is established that the overall process of pyrolysis appears simple but the sequence of reactions is complex and involves both endothermic and exothermic processes whose thermodynamics and kinetics are poorly understood (Pyle and Zaror, 1984). Under such complex phenomena, it is impossible to formulate a complete mathematical model of pyrolysis which will still be mathematically tractable.…”

Section: Introductionmentioning

confidence: 99%

“…In fact, the need for the simple rationally-based models of pyrolysis as a basis for reactor design has been identified in the survey of low temperature (i.e. less than 600 o C) pyrolytic conversion of biomass to usable forms of energy since the complications involved in the numerical solution of a more sophisticated models make them unsuitable for design and prediction purposes (Pyle and Zaror, 1984). One angle of approach had been adopted to develop simple and economic models which aggregate the more important aspects of the sequence of events as a solid sample is pyrolysed.…”

Section: Introductionmentioning

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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“…Energy conservation equation 한편 본 연구에서 사용한 화학반응 데이터 , 와 물성치 (kinetic data) ( Table 1 Kinetic data and properties used in this study (7) Kinetic data and properties Unit Value (10) Babu & Chaurasia model (3) Jalan & Srivastava model …”

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Investigation of Water Evaporation from Biomass with Different Torrefaction Environments

Go¹,

Kim

Lee³

et al. 2013

Transactions of the Korean Society of Mechanical Engineers B

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Heat transfer and kinetics in the low temperature pyrolysis of solids

Cited by 328 publications

References 9 publications

Examination and Evaluation of the Use of Screen Heaters for the Measurement of the High Temperature Pyrolysis Kinetics of Polyethene and Polypropene

Examination and Evaluation of the Use of Screen Heaters for the Measurement of the High Temperature Pyrolysis Kinetics of Polyethene and Polypropene

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

Investigation of Water Evaporation from Biomass with Different Torrefaction Environments

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