"Torben V. Mogensen" <vesettvm@get2net.dk> wrote in message
news:U60Le.2$EM.0@news.get2net.dk...
> Hej på DR tekst TV står at brændeovne forurener meget med partikler,
mere
> end biler og lastbiler.
> Hvad er det for nogle partikler?
> Jeg troede de kom fra fossile brændstoffer, olie, benzin, kul, og altså
> ikke fra træ, som vi må vel gå ud fra at folk fyrer med.
> Kommer partiklerne fra en enhver forbrænding?
Der indgår mange reaktioner i forbrændingen af træ. Jeg har tidligere
forsøgt at sætte mig lidt ind i korrekt forbrænding og fyring af/med træ,
men husker ikke detaljerne længere. Her er imidlertid nogle links med mere
info.
[1] <
http://www.epa.gov/ttn/chief/ap42/ch01/bgdocs/b01s09.pdf>
[2] <
http://www.epa.gov/ttn/chief/ap42/ch01/related/woodstove.pdf>
[3] <
http://www.fpl.fs.fed.us/documnts/fplmisc/rpt2136.pdf>
[4] <
http://www.woodheat.org/environment/hpawma.pdf>
[5] <
http://www.deh.gov.au/atmosphere/airquality/publications/handbook/>
I grove træk består emissionerne af:
* sod, der dannes ved ufuldstændig forbrænding af kulbrinter og danner
partikler omkring 10 mu. Disse partikler kan indeholde PAH, holder sig
svævende længe i luften og indåndes derfor let i lungerne.
* PAH, 'poly-cyclic aromatic hydrocarbons', dannes ved ufuldstændig
forbrænding (ifm svovl) og kan være kræftfremkaldende.
* uforbrændt gas, der kondenserer til tjære i eller udenfor skorstenen.
* NOx, Nitrogen-oxider, dannes pga for høj forbrændingstemperatur.
* SOx, svovl-oxider
* CO, carbon-monoxid
* evt andre
I [5] afsnit '2.1 Chemistry of woodsmoke' skrives bla følgende om
emissioner:
"Wood-smoke has a complex chemical composition. It consists of a mix of low
molecular weight carbon based gases and many large molecular weight organic
compounds in the particles. The main polluting gas emitted by woodheaters
and open fireplaces is carbon monoxide (CO). The concentration of CO in the
emission from a smouldering woodheater is high enough to kill someone if
released into an enclosed space. Other gases emitted include methane (CH4),
ethane, propane and other low molecular weight organic gases. Generally,
other 'priority air pollutant gases' such as sulphur dioxide (SO2) and
oxides of nitrogen (NOx) are only emitted in very small quantities and are
not considered a problem from woodheaters.
The particles (or condensed droplets of tars) are made up of a complex mix
of organic compounds, with the chemistry changing depending on combustion
conditions in the heater. Essentially the combustion chamber of a woodheater
is like a chemical manufacturing process where the large molecules of lignin
and cellulose making up the wood are converted into other organic chemicals.
The organic chemicals include some known to be respiratory irritants and
known or suspected carcinogens. One significant group is known as
polyaromatic hydrocarbons or PAH. Increased interest from pollution control
authorities in a range of trace chemicals known as air-toxics has led to
greater attention being paid to woodsmoke. A recent study conducted by CSIRO
for Environment Australia has determined emission factors for 65 chemicals
in wood-smoke and will assist authorities in developing control strategies
for these chemicals. This report is available from the Environment Australia
web site (see reference list - Environment Australia 2002)."
I [3] er der en fin beskrivelse af forbrændingsprocesserne i træ.
--
TA