Biodesulphurized low rank coals appraisal: Initial, treated, their bitumens and
, M. Stefanova
, L. Gonsalvesh
, V. Groudeva
, P. Gadjanov
, R. Carleer
, J. Yperman
Institute of Organic Chemistry, Bulgarian Academy of Sciences, bl. 9, Soﬁa 1113, Bulgaria
Soﬁa University “St. Kl. Ohridski”, Faculty of Biology, D.Tzankov, 8, Soﬁa 1164, Bulgaria
Technical Uniersity of Soﬁa, Thermal and Nuclear Power Eng. Dept., Soﬁa 1756, Bulgaria
Hasselt University, CMK, Research Group Appl. Anal. Chem., Agoralaan- gebouw D, B-3590 Diepenbeek, Belgium
Received 13 June 2011
Received in revised form 27 July 2011
Accepted 28 July 2011
Available online 20 September 2011
Low rank high sulphur containing Bulgarian coals are biodesulphurized on laboratory scale. Treatment of
Maritza East lignites by bacteria Pseudomonas putida B2 (PP) attained 44% total desulphurization, while
biodesulphurization of Bobov dol subbituminous coal by Acidothiobacillus ferrooxidans F3 (AFe) demonstrated
14%. The caloric values were slightly altered, 0.8% for lignites and 4.7% for subbituminous coal.
Bitumens from the initial and biotreated coals and fractions of their neutral oils are studied. For
subbituminous coal treated by AFe F3 bacteria increase in polar diterpenoids is registered by GC/MS.
Concerning the set of polar diterpenoids produced during lignites treatment by PP B2 their relative contents
are comparable with the ones for initial lignites. GC/MS analyses of soluble products from both coals did not
give any information for sulphur containing compounds.
Temperature programmed reduction coupled “on-line” with mass spectrometry (AP-TPR/MS) and its “off-
line” TD-GC/MS version are used for sulphur tracking in solid residues after bitumen extraction. Quantitative
interpretation of TD-GC/MS proﬁles revealed changes in organic sulphur compounds, elemental sulphur and
Results gave us ground to conclude that AFe F3 bacteria decrease pyritic sulphur content and slightly oxidize
coal organic matter while PP B2 bacteria inﬂuence lignite organic matter and also affect pyritic sulphur.
© 2011 Elsevier B.V. All rights reserved.
Clean coal utilization is an actual challenge concerning higher
energy consumption and global ecological impact. During coal
combustion sulphur is emitted as SO
and contributes to air pollution
and acid rains.
Sulphur is present in coal mainly as inorganic, i.e. pyritic and
organic forms. Contents of these dominating sulphur types account
more than 80%. Pyritic sulphur occurs as ﬁnely disseminated and
randomly distributed crystals in coal mineral matter whereas the
organic sulphur is presented as an integral part of the coal matrix
covalently bounds to its complex structure. By application of different
desulphurization procedures it is difﬁcult to attain simultaneously
high organic sulphur removal and moderate coal destruction. The last
one reﬂected a decrease in coal energy value and thus considered less
suitable for energy production.
One possibility to prevent environment from sulphur oxides is to
reduce sulphur content in fuel before combustion. Biodesulphuriza-
tion is one of the promising methods for production of environmental
friendly fuels. Microbial coal desulphurization offers many advantages
over conventional physical and chemical treatments and energetic
value of coal is slightly altered. Biological processes are based on coal
treatment by microorganisms and are performed under mild
conditions without harmful products. Biodesulphurization carried
out at appropriate conditions promoted the oxidative conversion of
the reduced forms of sulphur in water soluble, easy washed-out
Acidothiobacillus ferrooxidans (AFe) and Pseudomonas putida (PP)
are widespread microbial cultures used in coal biodesulphurization
[1,2]. AFe is effective only in the pyritic sulphur removal while PP
microorganism is capable to decrease organic sulphur as well [3,4].
There are scanty studies on the changes in extracted organic
products (bitumen) from coals desulphurized by the above men-
tioned bacteria [5–7]. An investigation on sulphur transformations in
solid residues after bitumen extraction totally misses. By additional
information for the organic soluble components, light will be shed on
microorganisms' application and mechanisms of their activity. It will
contribute to improve our knowledge for biodesulphurization
processes as well.
The aim of the present study is to appreciate sulphur types changes
in biotreated coal samples by AFe and PP bacteria. The distribution of
Fuel Processing Technology 92 (2011) 2328–2334
⁎ Corresponding author.
E-mail address: email@example.com (M. Stefanova).
0378-3820/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
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