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Pyrolysis and gasification of pellets from sugar cane bagasse and wood
KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
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2006 (English)In: Fuel, ISSN 0016-2361, Vol. 85, no 10-11, 1535-1540 p.Article in journal (Refereed) Published
Abstract [en]

Wood pellets have become a popular form of biomass for power generation and residential heating due to easier handling both for transportation and for feeders in the treatment units, improved conversion and storage possibilities. The research on wood pellets as fuel has also been intensified during the past decade. However, other biomass sorts in pellet form, such as sugar cane bagasse, have not yet been extensively studied, especially not physical effects on the pellets during thermal treatment. Bagasse and wood pellets of different origin and sizes, shredded bagasse and wood chips have been studied in a thermogravimetric equipment to compare the effects of sort, origin, size and form of biomass during slow pyrolysis and steam gasification. Physical parameters such as decrease of volume and mass during treatment, as well as pyrolysis and gasification rates are of primary interest in the study. An important observation from the study is that for pellets the char density decreased during pyrolysis to a minimum around 450 degrees C, but thereafter increased with continued heating. The wood chips behaved differently with a continuous char density decrease during pyrolysis. Another conclusion from the work is that the size of the pellet has larger impact on the shrinkage behaviour throughout the conversion than the raw material, which the pellet is made of.

Place, publisher, year, edition, pages
2006. Vol. 85, no 10-11, 1535-1540 p.
Keyword [en]
pyrolysis, char density, steam gasification, CHIMNEY EMISSIONS, SOFTWOOD PELLETS
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:kth:diva-14066DOI: 10.1016/j.fuel.2005.12.005ISI: 000237998300028Scopus ID: 2-s2.0-33645334656OAI: oai:DiVA.org:kth-14066DiVA: diva2:329551
Note
QC 20100712Available from: 2010-07-12 Created: 2010-07-12 Last updated: 2010-11-29Bibliographically approved
In thesis
1. Comparative study of residue pellets from cane sugar and palm-oil industries with commercial wood pellets, applied in downdraft gasification
Open this publication in new window or tab >>Comparative study of residue pellets from cane sugar and palm-oil industries with commercial wood pellets, applied in downdraft gasification
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

While biomass utilization for energy conversion in the industrialized nations is being largely developed, highly efficient and environmentally friendly, many tropical countries still use biomass at low efficiencies and high emission levels. The main reasons for these gaps are both political and technological: the energy markets are different, the Gross National Product (GDP) differs widely, and the feedstock differs in form and conversion behaviour. By implementing newer technologies adapted for tropical biomass feedstock, there would be a large potential in these countries for increased energy services since access to modern energy still is an essential step for improving the GDP for a country. Two dominant and tropically placed industries available for energy improvements are the cane sugar and palm-oil industries, which both produce an abundant amount of biomass residues. One step towards enhanced utilization of the residues, which would not require large investment costs in the power plant section nor in the processes of these industries, would be to install a pelletizing unit in the industry area to make fuel out of the excess residues for sale to the nearby villages. The pellets could be used both for cooking/heating and for small-scale power generation in a gasification-IC engine plant.

The overall objective of this study is to experimentally evaluate the biomass residues in pellet form from the cane sugar and palm oil industries during conversion to useful energy in small-scale systems.

The thesis is built upon five publications which include experimental analysis on flaming pyrolysis and rapid heating of pellets (paper I), pyrolysis in oxygen-free atmosphere and slow heating with subsequent steam gasification (paper II), global pelletizing data such as relative energy consumption, temperature levels, particle size and moisture content for successful pelletizing process (paper III), downdraft gasification evaluation including reactor temperature distribution, gas composition, cold-gas efficiency and packed-bed mechanics (paper IV) and a numerical model including the overall system efficiency for residue-to-electric power based in a small-scale gasifier system (paper V).The single-pellet studies revealed that pyrolysis in reducing atmosphere is to prefer compared to flaming pyrolysis in oxidizing environment with regards to the char quality.

The studies also showed favourable thermochemical and mechanical behaviour for smaller size pellets (Ø6- Ø8mm) compared to larger size ones (Ø12 mm). Therefore, a downdraft gasifier of closed constricted type was designed for real gasification tests of the residue pellets of sizes Ø6- Ø8mm. These tests showed that all the studied pellet sorts could be used in one and the same gasifier, resulting in different reactor temperature distributions and gas compositions with lower heating values in the range of 4.1-5.4 MJ/m3n dry gas. The reactor bed dynamics showed to be dependent both on the fuel reactivity and the size, with less pressure drop for larger size pellets with lower reactivity. The pelletizing process itself revealed that the selected residues all needed higher moisture content and smaller particle size than recommended for wood for successful pelletizing. The relative electric energy consumption was lower when producing larger size pellets Ø8 mm than smaller ones (Ø6 mm) of same material. For untreated wet empty-fruit bunch (EFB) a stand-alone power plant with integrated EFB pre-treatment and gasification could generate 380 kWh of net electricity per ton of EFB at a “well-to-wheel” efficiency of 15%.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. 54 p.
Series
Trita-KRV, ISSN 1100-7990 ; 2009:03
Keyword
energy engineering
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-11300 (URN)978-91-7415-455-9 (ISBN)
Public defence
2009-10-28, Sal M3, Brinellvägen 64, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100712Available from: 2009-10-15 Created: 2009-10-15 Last updated: 2010-07-15Bibliographically approved
2. Thermochemical conversion of biomass pellets: a parametric study for application in downdraft gasification
Open this publication in new window or tab >>Thermochemical conversion of biomass pellets: a parametric study for application in downdraft gasification
2005 (English)Licentiate thesis, comprehensive summary (Other scientific)
Place, publisher, year, edition, pages
Stockholm: KTH, 2005. 33 p.
Series
Trita-KRV, ISSN 1100-7990 ; 2005:4
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-523 (URN)91-7178-060-2 (ISBN)
Presentation
2005-05-26, sal M3, KTH, Brinellvägen 64, Stockholm, 10:00
Supervisors
Note
QC 20101129Available from: 2005-11-29 Created: 2005-11-29 Last updated: 2010-11-29Bibliographically approved

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