Co-pelletization of Torrefied Cotton Stalk and Coffee Husk as an Alternative Energy Source for Cement Pyroprocessing
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Date
2018-10
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
Cement manufacturing is an energy and emission intensive process. The use of alternative fuels to
replace coal contributes to energy security and the total environmental footprint of the cement
industry. This study investigated the suitability of co-pelletized torrefied coffee husk and cotton
stalk as alternative energy mix for cement pyroprocessing. Process parameters which affect the
calorific value such as particle size (100-125����, 125-250 ���� and, 250-500 ����), mixing ratio
(0.33, 0.5 and 0.67) and torrefaction temperature (200℃, 250℃ and 300℃) were optimized via
Box Behnken design (BBD). Characterization of raw coffee husk, cotton stalk and mixed torrefied
pellet for proximate analysis, ultimate analysis, calorific value, bulk density, ash composition,
Thermogravimetric analysis (TGA) and Fourier transmission infrared spectroscopy analysis (FTIR)
were
determined
to
understand
the
physiochemical
and
thermal
property
of
the
fuel.
Based
on
the
results, the optimal conditions were (particle size=100-125����, mixing ratio=0.62 and
torrefaction temperature of 300℃), with a maximum calorific value of 5320.72kcal/kg. The
optimum mixed torrefied pellet showed a decrease in moisture content (1.67%), volatile content
(50.45%), hydrogen to carbon ratio (0.044) and oxygen to carbon (0.4239), while the fixed carbon
(37.14%), elemental carbon (68.1195%) and calorific value (5322.31kcal/kg or 22.283 MJ/Kg)
increased considerably. As shown in the FT-IR analysis, loss of -OH groups resulted in decreased
hydrogen-bonding capacity which makes the mixed torrefied pellet more hydrophobic. Moreover,
the TGA analysis showed that the lignin content at higher torrefaction temperature was higher
which was responsible for the higher heating value of mixed torrefied pellet. In view of the results
obtained in this study, the proposed mixed torrefied pellet has a potential to be used as a source
of alternative energy for cement industries.
Description
Keywords
Torrefaction, Co-pelletization, Alternative energy, Cotton stalk, Coffee husk