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Evaluation of a constant volume sampling set-up for residential biomass fired appliances: influence of dilution conditions on particulate and PAH emissions
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
2005 (English)In: Biomass and Bioenergy, ISSN 0961-9534, Vol. 29, no 4, 258-268 p.Article in journal (Refereed) Published
Abstract [en]

Increased concerns about particulate matter (PM) and polycyclic aromatic hydrocarbons (PAH) emissions from residentialbiomass combustion and their potential health effects, motivates detailed emission measurements under controlled conditions. Traditional sampling in raw flue gases can suffer from drawbacks mainly related to transient flows and the condensable nature of organic compounds. Whole flow dilution with constantvolumesampling (CVS) is an alternative method but different samplingconditions may, however, influence the emission characteristics. The objective was to design a CVS system for emission measurements in residentialbiomassfiredappliances and determine the influence of dilutionsamplingconditions on the characteristics and distributions of PM and PAH. Softwood pellets were combusted in a pellet stove with variations in; dilution ratio (3–7x), sampling temperature (45–75 °C), dilution tunnel residence time (2–4 s) and fuel load (2.3 and 4.8 kW) according to a statistical experimental design. The samplingconditions did not influence either the emission concentrations of PM, CO and NO or the particle size distribution. Variations in residence time had no significant effect on any studied emission parameter. However, increased concentrations of organic gaseous carbon (OGC) and PAH were observed with increased dilution ratio. The distribution between particulate and semivolatile phase was influenced for 12 of the 37 analyzed PAH compounds, mainly by increased fractions of semivolatile material at higher sampling temperature. No influence of sampling temperature was observed for the concentrations of PAHtot or the dominating PAH compounds, i.e. phenanthrene, fluoranthene and pyrene. The results together with practical considerations also suggest sampling at 50±5 °C and 3–4 times dilution as robust and applicable conditions in the presently designed setup.

Place, publisher, year, edition, pages
Elsevier, 2005. Vol. 29, no 4, 258-268 p.
Keyword [en]
Pellets, Emissions, Dilution, Particulates, PAH
National Category
Engineering and Technology
URN: urn:nbn:se:umu:diva-4500DOI: 10.1016/j.biombioe.2005.03.003OAI: diva2:143629
Available from: 2005-04-18 Created: 2005-04-18 Last updated: 2013-04-10Bibliographically approved
In thesis
1. Particulate and gaseous emissions from residential biomass combustion
Open this publication in new window or tab >>Particulate and gaseous emissions from residential biomass combustion
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Biomass is considered to be a sustainable energy source with significant potentials for replacing electricity and fossil fuels, not at least in the residential sector. However, present wood combustion is a major source of ambient concentrations of hydrocarbons (e.g. VOC and PAH) and particulate matter (PM) and exposure to these pollutants have been associated with adverse health effects. Increased focus on combustion related particulate emissions has been seen concerning the formation, characteristics and implications to human health. Upgraded biomass fuels (e.g. pellets) provide possibilities of more controlled and optimized combustion with less emission of products of incomplete combustion (PIC´s). For air quality and health impact assessments, regulatory standards and evaluations concerning residential biomass combustion, there is still a need for detailed emission characterization and quantification when using different fuels and combustion techniques.

This thesis summarizes the results from seven different papers. The overall objective was to carefully and systematically study the emissions from residential biomass combustion with respect to: i) experimental characterization and quantification, ii) influences of fuel, appliance and operational variables and iii) aspects of ash and trace element transformations and aerosol formation. Special concern in the work was on sampling, quantification and characterization of particulate emissions using different appliances, fuels and operating procedures.

An initial review of health effects showed epidemiological evidence of potential adverse effect from wood smoke exposure. A robust whole flow dilution sampling set-up for residential biomass appliances was then designed, constructed and evaluated, and subsequently used in the following emission studies. Extensive quantifications and characterizations of particulate and gases emissions were performed for residential wood and pellet appliances. Emission factor ranges for different stoves were determined with variations in fuel, appliance and operational properties. The emissions of PIC´s as well as PMtot from wood combustion were in general shown to be considerably higher compared to pellets combustion. PAHtot emissions were determined in the range of 1300-220000 µg/MJ for wood stoves and 2-300 µg/MJ for pellet stoves with phenantrene, fluoranthene and pyrene generally found as major PAH´s. The PM emissions from present residential appliances was found to consist of significant but varying fractions of PIC´s, with emissions in the range 35-350 mg/MJ for wood stoves compared to 15-45 mg/MJ for pellet stoves. Accordingly, the use of up-graded biomass fuels, combusted under continuous and controlled conditions give advantageous combustion conditions compared to traditional batch wise firing of wood logs. The importance of high temperature in well mixed isothermal conditions was further illustrated during pellets combustion to obtain complete combustion with almost a total depletion of PIC´s. Fine (100-300 nm) particles dominated in all studied cases the PM with 80-95% as PM1. Beside varying fractions of carbonaceous material, the fine PM consisted of inorganic volatilized ash elements, mainly found as KCl, K3Na(SO4)2 and K2SO4 with mass concentrations at 15-20 mg/MJ during complete combustion. The importance of the behavior of alkali elements for the ash transformation and fine particle formation processes was further shown, since the stability, distributions and compositions also directly control the degree of volatilization. In addition to the alkali metals, zinc was found as an important element in fine particles from residential biomass combustion. Finally, the behaviour of volatile trace elements, e.g. Zn and Cd, during pellets production and combustion were studied. A significant enrichment in the pellet fuel during the drying process was determined. The magnitude and importance of the enrichment was, however, relative small and some alternative measures for prevention were also suggested.

Place, publisher, year, edition, pages
Umeå: Tillämpad fysik och elektronik, 2005. 45 p.
ETPC Report, ISSN 1653-0551 ; 05-03
Chemistry, aerosols, air pollution, emissions, fuel pellets, residential biomass combustion, inorganic characterization, incomplete combustion, particulate matter, polycyclic aromatic hydrocarbons, trace elements, Kemi
National Category
Chemical Sciences
urn:nbn:se:umu:diva-501 (URN)91-7305-871-8 (ISBN)
Public defence
2005-04-29, KB3B1, KBC-huset, Umeå universitet, Umeå, 10:00
Available from: 2005-04-18 Created: 2005-04-18Bibliographically approved

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