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Effects of fluidizing velocity and coal parameters to the total fraction of volatiles unburnt in the freeboard during devolatilization in fluidized bed combustion

Nowadays, coal has been used to substitute oil and natural gas as a fossil
fuel. Among commercially available coal combustion system, fluidized bed
combustion (FBC) has received increasing attention during the past 20 years
because of its advantages over conventional boilers in generating industrial
process steam. Low rank coals contain a substantial amount of volatiles, which
contribute up to 40% of the total heat produced during the combustion. Hence,
precise knowledge of the amounts of volatiles released during thermal
decomposition of coal, as a function of the particle temperature history and
operating conditions is necessary. The clear understanding behaviour of the total
fraction of volatile unburnt in the freeboard is also required. The goals of this
study are to simulate the verified model for investigating the effects of coal
parameter and fluidizing velocity on devolatilization history under pyrolysis and
combustion condition and on total fraction of volatiles unburnt in freeboard under
Fluidized Bed Combustor Condition.
The combined model (Agarwal (1987) and Bautista (1996)) has been
proposed to investigate the total fraction of volatiles unburnt in the freeboard
region fluidized bed combustion. The coal particle phenomena are modelled using
coupled heat transfer (both to and through the particle) and chemical reaction
(represented by the distributed activation energy model) approach. Each coal
particle is assumed to be in contact with the bubble and in the emulsion phase for
specific period of time. The frequency of the bubble-emulsion contact cycle as
well as the residence time of the coal particle within each phase during the cycle is
calculated from the bubble coalescence model. Numerical solution is needed to
solve partial differential equation of the model. Method of Lines (MOL)
commanded in MATLAB has been chosen.
The combined model consisting of Bautista-Margulis (1996) and Agarwal
(1987) has been successfully used to predict the total fraction of volatiles unburnt
in freeboard. The longer devolatilization process is caused by higher rank of coal
(for coal particle 1 and 3 mm in diameter), bigger diameter, and slower fluidizing
velocity. Coal with 10 mm in diameter, heat transfer controls the devolatilization
process. The total fraction released to the freeboard during devolatilization is
found to be decrease with the increase in rank of coal, coal diameter, and
fluidizing velocity.

Ketersediaan

Informasi Detail

Judul Seri

No. Panggil

TK HAR e/02

Penerbit

Bandung : Program Studi Teknik Kimia Fakultas Teknologi Industri - UNPAR., 2002

Deskripsi Fisik

xiv, 74 p. : il. ; 30 cm

Bahasa

English

ISBN/ISSN

-

Klasifikasi

-

Tipe Isi

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Tipe Media

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Tipe Pembawa

-

Edisi

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Subjek

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Info Detail Spesifik

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Pernyataan Tanggungjawab

Iwan Harianto, Yung Indarto

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