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Pyrolysis characteristics and global kinetics of coconut and cashew nut shells
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.ORCID iD: 0000-0002-1837-5439
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
2006 (English)In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, 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.

Place, publisher, year, edition, pages
2006. Vol. 87, no 6, 523-530 p.
Keyword [en]
Coconut shells; Cashew nut shells; Pyrolysis; Kinetics
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-9120DOI: 10.1016/j.fuproc.2005.12.002ISI: 000236432200006Scopus ID: 2-s2.0-33644890190OAI: oai:DiVA.org:kth-9120DiVA: diva2:24285
Note
QC 20100914Available from: 2008-09-23 Created: 2008-09-20 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Fundamental Study of two Selected Tropical Biomasses for Energy: coconut and cashew nut shells
Open this publication in new window or tab >>Fundamental Study of two Selected Tropical Biomasses for Energy: coconut and cashew nut shells
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

 Cashew nut and coconut shells are two potential renewable and environmentally friendly energy sources that are commonly found as agro-industrial wastes in tropical countries. Despite this fact, they are not yet widely studied as such. Given this lack of specific technical and reliable data, technologies for their conversion into energy cannot be designed with confidence as it happens with other commonly studied biomass feedstock. Thus, the need to generate these data guided this research in order to provide technical information for the designing of appropriate thermochemical conversion technologies for energy generation, particularly, in remote areas, where electricity grid is neither a feasible nor an affordable solution.Among thermochemical processes, pyrolysis plays a key role as it is found in both combustion and gasification at their earlier stages. In both technologies, pyrolysis products are generated and later submitted to further transformations according to the process in use.Hence, pyrolysis was selected for thermal characterisation of cashew nut and coconut shells. The main characteristics envisaged are i) pyrolysis profiles; ii) global, semi-global and individual kinetics; iii) pyrolysis global and individual yields; iv) modelled pyrolysis yields at high heating rates; and, v)char combustion kinetics and reactivity. The main technique used for experimental data generation is thermogravimetry and FTIR spectroscopy. Data experimentally generated from TG and TG-FTIR experiments were processed through different methods and codes, such as the Coats and Redfern model-fitting method, the modelfree methods of Ozawa-Flynn-Wall, Friedman and ASTM E698, for semi-global and global kinetics; DAEM and FG-Biomass were used for pyrolysis individual kinetics and yields determination. Proximate and ultimate analyses were performed as well.The study revealed peculiar characteristics compared to the commonly known lignocellulosic biomass. The volatiles content was above 66%w/w; hemicelluloses DTG peak did not overlap with the cellulose peak; the global pyrolysis activation energies were around 200 and 120 kJ/mol for coconut and cashew nut shells, respectively. Hemicelluloses and cellulose showed varying activation energies as 130-216 and 155-208 kJ/mol, respectively. Char combustion showed two steps with activation energies of 135 and 121 kJ/mol (cashew nut shells); 105 and 190kJ/mol (coconut shells). Individual yields and kinetics were determined for 17 compounds, including tars. These data are of key importance for modelling and the consequent data generation for the designing of appropriate thermochemical energy for these biomasses.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. xi, 71 p.
Keyword
Cashew nut shells, coconut shells, biomass, thermogravimetry, pyrolysis, kinetics, combustion
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-9138 (URN)978-91-7415-079-7 (ISBN)
Public defence
2008-09-30, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100914Available from: 2008-09-24 Created: 2008-09-24 Last updated: 2010-09-14Bibliographically approved
2. Pyrolysis profiles and global kinetics of tropical biomass: coconut and cashew nut shells
Open this publication in new window or tab >>Pyrolysis profiles and global kinetics of tropical biomass: coconut and cashew nut shells
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
thermogravimetry, cashew nut cocnut shells, pyrolysis, kinetics
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-577 (URN)91-7178-188-9 (ISBN)
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

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