Combustion and pyrolysis characteristics of tunçblek lignite
J. Therm. Anal. Cal.
COMBUSTION AND PYROLYSIS CHARACTERISTICS OF TUNÇB LEK LIGNITE
. Y. Elbeyli 0 1
S. Pi kin 0 1
0 Akadémiai Kiadó , Budapest, Hungary Springer, Dordrecht , The Netherlands
1 Department of Chemical Engineering, Y ld z Technical University , 34210 stanbul , Turkey
In this study, thermal characteristics and kinetic parameters of cleaned Tunçbilek lignite were determined by using a Setaram Labsys DTA/TG/DSC thermal analysis system both for combustion and pyrolysis reactions. Experiments were performed at a heating rate of 10°C min-1 under reactive (air) and inert (nitrogen) gases up to 1000°C. Non-isothermal heating conditions were applied and reaction intervals were determined for combustion and pyrolysis reactions from obtained curves. The combustion properties were evaluation by considering the burning profile of the lignite sample. Burning temperatures and rate of combustion were determined from TG/DTG curves. Calorific value of the lignite sample was measured by DSC curve and compared with the adiabatic bomb calorimeter result. In addition to investigation of the combustion properties, pyrolysis characteristics of the lignite sample were investigated based on TG/DTG/DSC curves. Activation energy (E) and pre-exponential factor (A) were calculated from the TG data by using a Coats-Redfern kinetic model both for combustion and pyrolysis reactions of cleaned Tunçbilek lignite.
combustion; kinetics; lignite; pyrolysis; thermal analysis
Introduction
Thermogravimetric analyses (TG) together with DTA
or DSC are effective methods commonly used for
quantitative determination of mass loss as a function
of the gradual increase in temperature [
1
]. The
methods play an important role in the investigation of
thermal characteristics of mineral matters. Various
methods such as thermogravimetric analysis (TG),
differential thermal analysis (DTA), dynamic
microcalorimetric analysis (DMA) and swelling index (SI)
measurements have been developed to determine the
thermal characteristics of coals. Thermal
characteristics of coal change depend mainly on its chemical
constituents, macerals, rank, grade, origin, etc. [
2, 3
].
Coal undergoes a series of complex physical and
chemical changes during the combustion and pyrolysis.
Combustion characteristics such as heat content,
ignition and burn off temperatures and maximum rate of
mass loss are of important in coal utilization and these
features can be determined from the TG and DTG
curves of the coal samples [
4, 5
]. Also, pyrolysis of coal
is of important for beneficiation from coal due to being
the first step in coal conversion processes like
carbonization, liquefaction, combustion and gasification [6].
Previous studies on DTA/TG/DSC analysis of
lignite and bituminous coals carried out under
different experimental conditions. Results show that the
thermal behaviour of coals depends on experimental
*
conditions such as particle size, sample amount,
heating rate and gas flow rate. Pi kin et al. [
7
]
investigated the thermal reactivities of five Turkish lignites
(Elbistan, Ilg n, Karl ova, Kangal and Yata an) under
air atmosphere and show the correlations between
heat contents measured by DTA and calorific values
of the coal samples measured by adiabatic bomb
calorimeter. Kök et al. [
8
] investigated that combustion
characteristics of lignite and oil shale samples by
thermal analysis techniques and kinetic calculations
performed for oxidation. Iordanidis et al. [
1
]
investigated combustion properties and burning profiles of
Greece lignites and they showed good correlations
between results of proximate and calorimetry
analyses and DTA/TG data. Arenillas et al. [
9
] determined
by using the TG/DTA techniques that effects of coal
blending on combustion characteristics. Kök et al.
[
10
] determined that thermogravimetric
characterization of ten lignites and kinetic calculation for their
oxidation processes. Kök [
11
] carried out coal
combustion experiments in air atmosphere up to 600°C at a
heating rate of 10°C min–1 by using DSC and
calculated the kinetic parameters beneficiation from
Arrhenius and Coats–Redfern plots.
In addition to combustion studies of coal by using
TG/DTA/DSC, investigations of pyrolysis properties of
bituminous coal and lignites have been studied by many
investigators. Elder and Harris [
12
] investigated the
thermal characteristics of Kentucky bituminous coals
during pyrolysis in an inert atmosphere. They
determined the exothermic reaction at a range of 300 to
500°C, where the major mass loss occurs and which has
been associated with the primary carbonisation process
and the development of a plastic state. Elbeyli et al. [
13
]
investigated pyrolysis stages and kinetics parameters of
some Turkish bituminous coals in nitrogen atmosphere
up to 1000°C under non-isothermal condition by using
TG/DTG methods. Sina [
14
] investigated the kinetics
of Soma lignite in water vapor and inert atmosphere
(nitrogen) and (...truncated)