Re: GAS-L: NOx and gasifiers

[Claus Hindsgaul <claush@et.dtu.dk>]

tir, 2002-06-25 kl. 14:05 skrev Tom Reed:
> First, there is very little "high temperature NOx"  -  probably less than 1
> ppm - in wood gas because the flame temperature is lower than that of
> hydrocarbons.

I don't quite agree on that.

Our measurements of emissions from an IC engine[1] fueled by superficial
wood gas (mixed from flask without e.g. tars and NH3) showed NOx
emissions for lambda<1.5. Indeed they were lower than for natural gas
with this engine, but not negligible.

At the Biomass Conference in Amsterdam last week, a poster claimed that
80-100% of NH3 was converted to NOx during flame(!) combustion.

At the same conference Markus Kleinhappl presented measurements of NH3
levels in the gas from their double fire gasifier in Graz in Austria to
150-800 mg/Nm3. He claimed that a limit of <55 mg/Nm3 should be met for
engine operation.

Here at the DTU two-stage gasifier we also have massive amounts of NH3
in our gas condensate. We have not yet measured the NH3 concentration in
our gas. Tar is no longer an issue here, but it may be necessary to
remove some NH3 from the gas in order to meet NOx-regulations.

Fortunately NH3 is miscible in water so I expect it to be easy obtain
lower levels using water scrubbers. Only if there are tars in the gas,
the NH3 contaminated water needs special treatment. Otherwise it may be
processed at (Danish) biological surridge plants.

Can anybody elaborate on NH3 and NOx in wood gas and engine exhaust?
Measurements of either would be very interesting.

Claus Hindsgaul


    [1] Jesper Ahrenfeldt, Torben Kvist Jensen, Ulrik Henriksen and
    Jesper Schramm: "Experiments with Wood Gas Engines". SAE paper
    2001-01-3681, September 2001


-- 
Research Assistant M. Sc. Claus Hindsgaul
MEK, DTU, Building 120 - DK-2800 Lyngby, Denmark
Phone: (+45) 4525 4174 - FAX: (+45) 4593 5761
claush@mek.dtu.dk, http://www.et.dtu.dk/Halmfortet


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