Gasification Archive for July 2002

7 messages, last added Tue Nov 26 17:18:21 2002

Re: GAS-L: NOx and gasifiers

• To: gasification <gasification@crest.org>
• Subject: Re: GAS-L: NOx and gasifiers
• From: Claus Hindsgaul <claush@et.dtu.dk>
• Date: 02 Jul 2002 18:09:22 +0200
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Thank you for a lot of interesting input.

I have ordered some of the very interesting papers that Peacocke pointed
to.

I have been asked about more details on our gasifier. A short
description is available at
http://www.et.dtu.dk/halmfortet/research/twostage/ . The fuel currently
used is wood chips.

tir, 2002-06-25 kl. 18:39 skrev Tami Bond:
> I agree... what is gasification temperature? 'Thermal' NOx isn't
> significant for temperatures below about 1400 C. 

Our high temperature tar cracking zone has small hot spots up to approx.
1400C (measured by IR equipment) near the air nozzles. This should still
keep us below the NOx forming limit.

As many of you pointed out it is unlikely that woodgas would generally
contain serious amounts of NOx. The potential problem appear during
combustion. Will NH3 or HCN act as NOx precursors in wood gas? Or does
it actually *prevent* NOx from forming? (NH3 addition is used in some
boilers in order to decrease NOx emmisions)

The engine tests I refered to were based on *synthetic* woodgas
consisting of the *pure* gas components: H2, N2, CO, CH2, CH4 (no
particles, ammonia or steam). While NOx levels for lambda>1 peaked at
3300 mg/Nm3 when fueled by natural gas, it did not exceed 1000 mg/Nm3
when fueled by synthetic woodgas.
A few NOx measurements have been made in the exhaust from an IC engine
fueled by real gas from the two stage gasifier. They did not exceed 400
mg/Nm3 NOx.

So the NOx problem from woodgas fueled engines *appear* to be small or
non­existent.
In my prior posting I pointed out some contracting observations. I would
therefore like a little more evidence before concluding that NH3 does no
harm and can be safely left in the gas.

Claus

-- 
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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