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Metallic iron as a tar breakdown catalyst related to atmospheric, fluidised bed gasification of biomass
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
2006 (English)In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 85, no 06-maj, 689-694 p.Article in journal (Refereed) Published
Abstract [en]

Tar formation is a major drawback when biomass is converted in a gasifier to obtain gas aimed for utilisation in power production plants or for production of chemicals. Catalytic cracking is an efficient method to diminish the tar content in the gas mixture. In this study, the capability of metallic iron and iron oxides to catalytically crack tars has been experimentally examined. To obtain metallic iron, small grains of hematite (Fe2O3) were placed in a secondary reactor downstream the gasifier and reduced in situ prior to catalytic operation. The fuel used in the atmospheric fluidised bed gasifier was Swedish birch with a moisture content of approximately 7 wt%. The influence of temperature in the range 700-900 degrees C and), values (i.e. equivalence ratio, ER) between 0 and 0.20 have been investigated. In essence, the results show that raising the temperature in the catalytic bed to approximately 900 degrees C yields almost 100% tar breakdown. Moreover, increasing the). value also improves the overall tar cracking activity. The iron oxides did not demonstrate any catalytic activity.

Place, publisher, year, edition, pages
2006. Vol. 85, no 06-maj, 689-694 p.
Keyword [en]
biomass gasification, catalytic tar reduction, metallic iron
National Category
Chemical Process Engineering
Identifiers
URN: urn:nbn:se:kth:diva-15383DOI: 10.1016/j.fuel.2005.08.026ISI: 000234764900013Scopus ID: 2-s2.0-28244433478OAI: oai:DiVA.org:kth-15383DiVA: diva2:333424
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Metallic iron: potential to function as tar breakdown catalyst in waste gasification
Open this publication in new window or tab >>Metallic iron: potential to function as tar breakdown catalyst in waste gasification
2005 (English)Licentiate thesis, comprehensive summary (Other scientific)
Place, publisher, year, edition, pages
Stockholm: KTH, 2005. 43 p.
Series
Trita-KET, ISSN 1104-3466 ; 224
National Category
Chemical Process Engineering
Identifiers
urn:nbn:se:kth:diva-574 (URN)
Supervisors
Note
QC 20101217Available from: 2005-12-27 Created: 2005-12-27 Last updated: 2010-12-17Bibliographically approved
2. Iron-based materials as tar cracking catalyst in waste gasification
Open this publication in new window or tab >>Iron-based materials as tar cracking catalyst in waste gasification
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The treatment of municipal solid waste (MSW) in Sweden has changed during the past decades due to national legislation and European Union directives. The former landfills have more or less been abandoned in favour of material recycling and waste incineration. On a yearly basis approximately 2.2 million tonnes waste are incinerated in Sweden with heat recovery and to some extent also with electricity generation, though at a low efficiency. It is desirable to alter this utilisation and instead employ MSW as fuel in a fluid bed gasification process. Then electrical energy may be produced at a much higher efficiency. However, MSW contain about 1 % chlorine in the form of ordinary table salt (NaCl) from food scraps. This implies that the tar cracking catalyst, dolomite, which is normally employed in gasification, will suffer from poisoning if applied under such conditions. Then the tar cracking capacity will be reduced or vanish completely with time. Consequently, an alternative catalyst, more resistant to chlorine, is needed.

Preliminary research at KTH has indicated that iron in its metallic state may possess tar cracking ability. With this information at hand and participating in the project “Energy from Waste” an experimental campaign was launched. Numerous experiments were conducted using iron as tar cracking catalyst. First iron sinter pellets from LKAB were employed. They were reduced in situ with a stream of hydrogen before they were applied. Later iron-based granules from Höganäs AB were tested. These materials were delivered in the metallic state. In all tests the KTH atmospheric fluidised bed gasifier with a secondary catalytic reactor housing the catalytic material was deployed. Mostly, the applied fuel was birch. The results show that metallic iron possesses an intrinsic ability, almost in the range of dolomite, to crack tars. Calculations indicate that iron may be more resistant to chlorine than dolomite. The exploration of metallic iron’s excellent tar cracking capacity led to the innovative manufacture of an iron catalytic tar cracking filter as well as a general knowledge of its tar cracking capacity. This filter with dual functionality would be a general improvement of the gasification process since it among other things would make the process denser.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. 73 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2011:27
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-33043 (URN)978-91-7415-941-7 (ISBN)
Public defence
2011-05-19, F3, Lindstedsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20110428Available from: 2011-04-28 Created: 2011-04-27 Last updated: 2011-04-28Bibliographically approved

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