Modeling of Pyrolysis and Gasification of Biomass in Fluidized Beds: A Review

Basu, Prabir; Kaushal, Priyanka

doi:10.2202/1934-2659.1338

Cited by 59 publications

(52 citation statements)

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“…It generally occurs once the temperature of the biomass is above 200 °C at which volatiles (both gases and tar) start leaving the solid matrix of biomass (Basu and Kaushal, 2009;van de Weerdhof, 2010). It is also known as the destructive drying process, which is characterized by the devolatilization and carbonization of hemicellulose, depolymerization, devolatilization, and softening of lignin, and depolymerization and devolatilization of cellulose.…”

Section: Devolatilizationmentioning

confidence: 99%

A Comprehensive Review on Biomass Torrefaction

Nhuchhen¹,

Basu²,

Acharya³

2014

IJREB

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170

143

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Biomass is a versatile energy resource that could be used as a sustainable energy resource in solid, liquid and gaseous form of energy sources. Torrefaction is an emerging thermal biomass pretreatment method that has an ability to reduce the major limitations of biomass such as heterogeneity, lower bulk density, lower energy density, hygroscopic behavior, and fibrous nature. Torrefaction, aiming to produce high quality solid biomass products, is carried out at 200-300 °C in an inert environment at an atmospheric pressure. The removal of volatiles through different decomposition reactions is the basic principle behind the torrefaction process. Torrefaction upgrades biomass quality and alters the combustion behavior, which can be efficiently used in the co-firing power plant. This paper presents a comprehensive review on torrefaction of biomass and their characteristics. Despite of the number of advantages, torrefaction is motivated mainly for thermochemical conversion process because of its ability to increase hydrophobicity, grindability and energy density of biomass. In addition to this, torrefied biomass could be used to replace coal in the metallurgical process, and promoted as an alternative of charcoal.

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Section: Devolatilizationmentioning

confidence: 99%

A Comprehensive Review on Biomass Torrefaction

Nhuchhen¹,

Basu²,

Acharya³

2014

IJREB

Self Cite

170

143

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“…All elements (C, H, O, S, Cl, N) and mineral ash are massbalanced. Although the bed solids are well mixed in a fluidized bed, the gases remain generally in a plug-flow regime, with air entering from the bottom and the producer gas leaving from the top (Basu and Kaushal, 2009;Liu and Gibbs, 2003). This plug flow behavior is approximated in this new model using 10 continuously stirred tank reactors (CSTRs) in series, illustrated in Figure 1.…”

Section: Model Developmentmentioning

confidence: 99%

“…It is common to model the initial devolatilization as complete and instantaneous (Gungor, 2011;Basu and Kaushal, 2009;Fiaschi and Michelini, 2001). That is, regardless of where the biosolids enter, the moisture is vaporized and some products (CO, CO 2 , H 2 , CH 4 , tar, and solid char) are given off.…”

Section: Drying and Devolatilization (Dd) Zonementioning

confidence: 99%

Section: Kinetic Foundationsmentioning

confidence: 99%

“…Within each CSTR, the solids and gases are completely mixed and the temperature is uniform. Hydrodynamic influences are ignored, as at temperatures below 900 C, reaction rates are relatively slow when compared with mass transfer within a fluidized bed, and thereby dictate the speed of the process (Basu and Kaushal, 2009;Wang and Kinoshita, 1993;Reed, 1981).Within each reactor, 18 simultaneous equations account for the mass balances of 14 gaseous species (O 2 , CO, CO 2 , H 2 , CH 4 , H 2 O, C 6 H 6 , C 6 H 6 O, C 10 H 8 , NH 3 , HCl, H 2 S, N 2 , and Ar), two solid species (char and mineral ash), a total molar balance for the gas stream (n : total ), and an energy balance for the CSTR.An example of a species mass balance is shown in eq 2. The OX zone reactions (see Tables 3 and 4) are modeled with the oxidation of char, CO, CH 4 , and H 2 (reactions 1-4), as well as the oxidation of the tar species (reactions T5-T7).…”

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confidence: 99%

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Development of a chemical kinetic model for a biosolids fluidized-bed gasifier and the effects of operating parameters on syngas quality

Champion

Cooper

Mackie

et al. 2013

Journal of the Air & Waste Management Association

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In an effort to decrease the land disposal of sewage sludge biosolids and to recover energy, gasification has become a viable option for the treatment of waste biosolids. The process of gasification involves the drying and devolatilization and partial oxidation of biosolids, followed closely by the reduction of the organic gases and char in a single vessel. The products of gasification include a gaseous fuel composed largely of N 2 , H 2 O, CO 2 , CO, H 2 , CH 4 , and tars, as well as ash and unburned solid carbon. A mathematical model was developed using published devolatilization, oxidation, and reduction reactions, and calibrated using data from three different experimental studies of laboratory-scale fluidized-bed sewage sludge gasifiers reported in the literature. The model predicts syngas production rate, composition, and temperature as functions of the biosolids composition and feed rate, the air input rate, and gasifier bottom temperature. Several data sets from the three independent literature sources were reserved for model validation, with a focus placed on five species of interest (CO, CO 2 , H 2 , CH 4 , and C 6 H 6 ). The syngas composition predictions from the model compared well with experimental results from the literature. A sensitivity analysis on the most important operating parameters of a gasifier (bed temperature and equivalence ratio) was performed as well, with the results of the analysis offering insight into the operations of a biosolids gasifier.Implications: As gasification becomes a more prominent waste disposal option, understanding the effects of feedstock composition and gasifier parameters on the production of syngas (rate and quality) becomes increasingly important. A model has been developed for the gasification of dried sewage sludge that will allow for prediction of changes in syngas quality (and energy recovery from the waste), and should be helpful in assessing the benefits of new gasification projects. IntroductionGasification is the thermochemical conversion of organic feedstock into a synthetic gaseous fuel at high temperatures using a limited amount of air. The gaseous fuel produced by a gasifier is referred to as syngas or producer gas. Gasification lies between combustion and pyrolysis, and is a process that utilizes a substoichiometric amount of oxygen for partial oxidation of the feedstock. This in turn provides heat for the largely endothermic reduction reactions that produce the syngas, as well as the initial devolatilization of the biomass within the gasifier.Gasification is an efficient process for reducing the volume of waste, and is a process capable of delivering net energy gains (Greenhouse Gas Technology Center [GGTC], 2012; PuigArnavat et al., 2010). The remaining solids from the process are composed of the mineral ash that was contained in the feed and small amounts of organic ash, principally unreacted solid carbon (char). It is estimated that 7.2 million dry tons of sewage sludge are generated annually in the United States (North East Biosolids and Res...

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Numerical Simulation of the Thermal Degradation of Biomass – Approaches and Simplifications

Marsi

2014

Transformation of Biomass

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Modeling of Pyrolysis and Gasification of Biomass in Fluidized Beds: A Review

Cited by 59 publications

References 0 publications

A Comprehensive Review on Biomass Torrefaction

A Comprehensive Review on Biomass Torrefaction

Development of a chemical kinetic model for a biosolids fluidized-bed gasifier and the effects of operating parameters on syngas quality

Numerical Simulation of the Thermal Degradation of Biomass – Approaches and Simplifications

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