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Pyrolysis profiles and global kinetics of tropical biomass: coconut and cashew nut shells
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
2005 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

Biomass has been recognised as renewable and environmentally friendly source of energy since decades. Tropical biomasses which are available in large quantities as residues in Latin America, Africa and Asia, have high energy potential for exploitation through thermochemical conversion process, as pyrolysis, gasification or combustion. Cashew nut and coconut shells are two of the most abundant biomass fuels in tropical countries, which are still not well studied as energy sources.

This study aims at providing additional and unique data for the conversion of these specific tropical biomasses into energy. In fact, even though these shells are prolific in many tropical countries, they have so far been known principally as raw materials for non-energetic end-uses. Such uses are the production of activated carbon from coconut shells or cashew nut shells extraction from cashew nut shells, among others. Their use as energy sources is still traditional and unquestionably inefficient in most of these countries.

In this study, cashew nut and coconut shells were submitted to a controlled pyrolysis process using thermogravimetry, in order to describe and characterise their devolatilisation patterns as well as their respective global pyrolysis kinetics. The study was carried out in an inert atmosphere (argon) from ambient temperature to 1000oC at different heating rates, explicitly 5, 10, 20, 40 and 50 ºC/min. For kinetic parameters determination, the parallel-independent decomposition reactions mechanism was used together with the Coats and Redfern Method. The devolatilisation kinetics parameters of these special shells were compared with that of wood pellets.

This study is hitherto and, to the knowledge of the author, innovative and incomparable as no other studies in this perspective have been reported in the literature.

The exclusive findings from the current study are two clear peculiar mass loss rate peaks, during cellulose and hemicelluloses thermal degradation, with different heights, found in both tropical biomass samples. These peaks differ from the ordinary woody biomass one-overlapping mass loss rate peak. Kinetics of the thermal decomposition process obtained by applying the Coats and Redfern method and parallel-independent reaction mechanism, showed that coconut shells components are the most reactive followed by cashew nut shells components. It is, Arrhenius constant is greater for coconut shells and lower for wood pellets. These differences become bigger at high temperatures than at lower temperatures.

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , vii, 48 p.
Keyword [en]
thermogravimetry, cashew nut cocnut shells, pyrolysis, kinetics
National Category
Other Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-577ISBN: 91-7178-188-9 (print)OAI: oai:DiVA.org:kth-577DiVA: diva2:14483
Presentation
2005-12-06, sal B1, KTH, Brinellvägen 23, Stockholm, 10:00
Note
QC 20110128Available from: 2005-12-28 Created: 2005-12-28 Last updated: 2011-01-28Bibliographically approved
List of papers
1. Thermal characterisation of coconut and cashew nut shells
Open this publication in new window or tab >>Thermal characterisation of coconut and cashew nut shells
2005 (English)In: Eighth International Conference on energy for a clean environment, 2005Conference paper, Published paper (Other academic)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-29251 (URN)
Conference
Eighth International Conference on energy for a clean environment, Lisbon, Portugal, 27-30 June 2005
Note
QC 20110128Available from: 2011-01-28 Created: 2011-01-28 Last updated: 2011-01-28Bibliographically approved
2. Pyrolysis characteristics and global kinetics of coconut and cashew nut shells
Open this publication in new window or tab >>Pyrolysis characteristics and global kinetics of coconut and cashew nut shells
2006 (English)In: Fuel processing technology, ISSN 0378-3820, Vol. 87, no 6, 523-530 p.Article in journal (Refereed) Published
Abstract [en]

Coconut and cashew nut shells are two typical biomass wastes abundant in most of the tropical countries. However, despite their enormous potential as energy sources, they are hardly studied and their thermal characteristics are still not well known. In this study, both biomasses are thermally degraded through thermogravimetry and their characteristics such as devolatilisation profiles and kinetics are analyzed, from 250 to 900 °C, in an inert atmosphere, at two different heating rates, and compared with wood pellets. The results show that their pyrolysis profiles are different from that of the commonly studied woody biomass. In fact, they present two different peaks instead of the one overlapping peak, for hemicellulose and cellulose. In addition, they present activation energies ranging from that are slightly above the commonly known maximum for biomass. At 10 and 20 °C/min the activation energy varied from about 130 to 174 and 180 to 216 kJ/mol, for cashew and coconut shells, respectively.

Keyword
Coconut shells; Cashew nut shells; Pyrolysis; Kinetics
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-9120 (URN)10.1016/j.fuproc.2005.12.002 (DOI)000236432200006 ()2-s2.0-33644890190 (Scopus ID)
Note
QC 20100914Available from: 2008-09-23 Created: 2008-09-20 Last updated: 2013-06-12Bibliographically approved

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