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Combustion kinetics and reactivity of char from coconut shells pyrolysis
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.
2008 (English)In: 7th International Symposium of High Temperature Air Combustion and Gasification (HTACG 2008), 2008, , 7 p.Conference paper, Published paper (Refereed)
Abstract [en]

Combustion process has been the main thermochemical energy conversion technology known since ages. However, as the research on combustion increases, it becomes undeniable that combustion is a very complex process with a number of different parameters and features that cannot be studied at the same time and therefore, they are still not well known as such. In this study, coconut char, produced through pyrolysis at three different heating rates in a thermogravimetric analyzer, is submitted to a combustion using a binary mixture of O2 and He to study its reactivity and determine the respective combustion kinetics. The reactivity is studied by using the critical temperature approach while kinetic parameters are determined through software that allows the determination of the frequency factor, the activation energy and the reaction mechanism, through both model free and predefined model approaches. The results obtained are compared to the similar data available from the literature for other biomasses. The critical temperature was found to vary from 377 to 388oC. The kinetic triplet was found to be comparable with the same data from other biomasses, presenting values as E1,act=101 to 132 kJ/mol and E2,act=166 to 215 kJ/mol (activation energy); A1=2,57E6 to 2.95E10s-1 and A2=6.8E10 to 2.44E14 s- 1(frequency factor); n1=0.38 to 0.80 and n2=0.95 to 1.55 (reaction order).

Place, publisher, year, edition, pages
2008. , 7 p.
Keyword [en]
char, combusion, reactivity, kinetics
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-9141OAI: oai:DiVA.org:kth-9141DiVA: diva2:25245
Note
QC 20100914Available from: 2008-09-24 Created: 2008-09-24 Last updated: 2010-09-14Bibliographically 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

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