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Cashew Nut Shells Pyrolysis: Individual Gas Evolution Rates and Yields
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.
2007 (English)In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 21, no 4, 2357-2362 p.Article in journal (Refereed) Published
Abstract [en]

Cashew nut shells are one type of the most abundant biomass tropical wastes, which can be used for energy generation. However, there is lack of data for the thermal conversion process of cashew nut shells such as pyrolysis individual gas products, yields, and reaction kinetics. In this research work, the pyrolysis processes of cashew nut shells at low heating rates (10, 30, and 100 K/min) were studied. Thermogravimetric analyzer coupled with a Fourier transform infrared spectrometer (TG-FTIR) was used. The pyrolysis product yields obtained were compared with the available data in the literature for wood and Miscanthus Giganteus. It was found that cashew nut shells have tars and volatiles at levels equivalent to those of wood pellets, both above the tar and volatile content of M. Giganteus. Further, kinetic parameters were obtained from the TG-FTIR results using an approach based on parallel independent first-order reactions with a Gaussian distribution of activation energies and following the Tmax method. The data obtained through this approach included the identification, kinetics, and yield of each gas product precursor. These results are then used as input files for a distributed activation energy model (DAEM) for biomass pyrolysis, based on a functional group analysis, which still does not include the devolatilization, cross-linking competitive reactions. The predicted evaluation data from this model were found to generally agree with that from TG-FTIR analysis. However, the model still demands improvement to accommodate secondary and cross-linking competitive reactions.

Place, publisher, year, edition, pages
2007. Vol. 21, no 4, 2357-2362 p.
Keyword [en]
Activation energy, Crosslinking, Fourier transform infrared spectroscopy, Gaussian distribution, Hardwoods, Hulls (seed coverings), Mathematical models, Thermogravimetric analysis
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-9119DOI: 10.1021/ef0604792ISI: 000248085100068OAI: oai:DiVA.org:kth-9119DiVA: diva2:24284
Note
QC 20100902Available from: 2008-09-23 Created: 2008-09-20 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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