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Emissions of volatile organic compounds from wood
Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.ORCID iD: 0000-0002-0380-3533
2005 (English)Doctoral thesis, monograph (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, and to use a dry ice trap both to preconcentrate emitted VOCs 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 were analysed with FID and GC-MS. When the sawdust end moisture content was reduced below 10%wb, emissions of terpenes and of total VOC per oven dry weight increased rapidly. The increased temperature of the drying medium entering the drying tower also caused an increase in the amounts of emitted monoterpenes at sawdust moisture contents below the fibre saturation point.



Examination of sawdust and wood pellets from different pellets producers (3) revealed that most of the terpene emissions take place during the drying step, with flue gas dryers causing higher emissions than steam dryers. Almost all of the volatile terpenes remaining in wood after drying were released during pelleting. Increased terpene emissions during the pelleting process were found when sawdust with a higher moisture content was used.



Terpenes emitted naturally from vegetation can have adverse environmental impacts. 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.

Place, publisher, year, edition, pages
Karlstad: Karlstad University Studies , 2005.
Series
Karlstad University Studies, ISSN 14038099
National Category
Energy Systems
Research subject
Environmental and Energy Systems
Identifiers
URN: urn:nbn:se:kau:diva-18772ISBN: 9185335460 (print)OAI: oai:DiVA.org:kau-18772DiVA: diva2:592412
Available from: 2013-01-21 Created: 2013-01-21 Last updated: 2014-10-29

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