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Modelling Individual Evolved Gas Yields from Cashew Nut and 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.
2007 (English)In: Clean Air, ISSN 1561-4417Article in journal (Other academic) Submitted
Abstract [en]

Coconut and cashew nut shells are some of the biomass wastes typically available in many tropical countries. As renewable resources, they are eligible as important green sources for energy generation. Despite this evident fact, they are not yet commonly studied as such. In fact, while coconut shells are commonly known as activated carbon raw material, cashew nut shells are mostly known as cnsl precursors. Both products are of great importance commercially. In this research study, a non-isothermal pyrolysis of these two biomass wastes is performed using TGFTIR, at moderate heating rates (10, 30 and 100 K/min) with the objective of identifying the evolved gases and determine the respective intrinsic kinetics. This TG-FTIR system continuously monitors i) the time dependent evolution of volatiles, ii) the tars evolution rate, and iii) the weight of char. FT-IR spectra were obtained every 30 seconds and quantification of all volatiles (except tars) was done from quantification routines obtained from calibration runs with pure compounds. The data are used to generate input files that are used in a code based on the distributed activation energy model (DAEM). Using the code and the input files generated, the gas yields were predicted for comparison with the experimental results, at the same conditions. The prediction results showed a good agreement with the experimental data. Thus, the code was extended to very high heating rates (1000 and 10,000 K/s). The results at low heating rates are compared to the literature available data obtained under analogous conditions.

Place, publisher, year, edition, pages
2007.
Keyword [en]
biomass wastes, pyrolysis, kinetics, yields
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-9143OAI: oai:DiVA.org:kth-9143DiVA: diva2:25246
Note
QS 20120314Available from: 2008-09-24 Created: 2008-09-24 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

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