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A Method to Measure Emissions from Dryers with Diffuse Leakages, Using Evaporated Water as a Tracer
Karlstad University, Division for Engineering Sciences, Physics and Mathematics.
2003 (English)In: Drying Technology, ISSN 0737-3937, Vol. 21, no 7Article in journal (Refereed) Published
Place, publisher, year, edition, pages
2003. Vol. 21, no 7
Identifiers
URN: urn:nbn:se:kau:diva-2328OAI: oai:DiVA.org:kau-2328DiVA: diva2:24667
Available from: 2009-06-05 Created: 2009-06-05Bibliographically approved
In thesis
1. Emissions of volatile organic compounds from wood
Open this publication in new window or tab >>Emissions of volatile organic compounds from wood
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The central aim of this thesis is to support the efforts to counteract certain environmental problems caused by emissions of volatile organic compounds.

The purpose of this work was (1) to develop a method to establish the amount of emitted substances from dryers, (2) to determine the effect of drying medium temperature and end moisture content of the processed material on emissions of monoterpenes and other hydrocarbons, (3) to examine the emissions of monoterpenes during production of pellets, and (4) to examine the natural emissions from forests with an eye to implications for modelling.

The measurement method (1) resolves the difficulties caused by diffuse emissions, and also solves the problems associated with high moisture content of the drying medium. The basic idea is to use water vapour to determine the exhaust flow, while a dry ice trap is used both to preconcentrate emitted volatile organic compounds and to determine the moisture content of the drying medium. The method as used in this paper has an uncertainty of 13% using a 95% confidence interval.

Emissions from a spouted bed (2) in continuous operation drying Norway spruce sawdust at temperatures of 140°C, 170°C or 200°C was analysed with FID and GC-MS. When the sawdust end moisture content was reduced below 10%wb, emissions of terpenes and volatile organic compounds per oven dry weight increased rapidly. Increased temperature of the drying medium increased the amounts of emitted monoterpenes when sawdust moisture content was below the fibre saturation point.

Examination of sawdust and wood pellets from different pellets producers (3) revealed that most of the terpene emissions happened during the drying step, with rotary dryers causing higher emissions than steam dryers. Almost all of the volatile terpenes remaining in wood after drying were released during pelleting. When sawdust with higher moisture content was used in the pellets press, the terpene emissions were increased.

Terpenes emitted naturally from vegetation can have an adverse environmental impact. Factors affecting terpene emissions from tree species in Sweden were reviewed (4). Models for prediction of terpene fluxes should include not only temperature but also light intensity, seasonal variation, and a base level of herbivory and insect predation. Prediction of high concentrations of ambient terpenes demand sufficient resolution to capture emission peaks e.g. those caused by bud break.

Series
Karlstad University Studies, ISSN 1403-8099 ; 2005:6
Keyword
VOC, terpenes, drying, wood, emissions, spouted bed
National Category
Other Environmental Engineering
Research subject
Environmental and Energy Systems
Identifiers
urn:nbn:se:kau:diva-2327 (URN)91-85335-46-0 (ISBN)
Public defence
2005-03-31, Nyquistsalen, 9C 203, Karlstads universitetKarlstad, 10:00 (English)
Opponent
Supervisors
Available from: 2009-06-05 Created: 2009-06-05 Last updated: 2009-06-05Bibliographically approved

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http://dx.doi.org/10.1081/DRT-120023176
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