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Posted by bobby7388 on October 29, 2004 at 16:31:14:
In Reply to: Proper air/fuel requirments in a wood fired boiler posted by Chris B on October 29, 2004 at 08:48:40:
: We burn wood dust and shavings primarily made up of Red Oak at about 7% moisture. I'm looking for some help in determing proper air/ fuel mixtures. We have firebox temps. in excess of 2000F and causing fusion. The ash comes out in chuncks not a powder like it should. Under grate temps are around 300 to 350F. and the grates are covered with a hard layer of ash. The refractory side walls get a glazed look and the over fire air nozzles get covered with the melted ash.
It sounds like you are getting what also happens in coal fired boilers/burners.
This is called ash-softening, when heated the ash becomes soft and sticky then eventually becomes fluid like, this is how clinkers form.
The procedure to find your specific softening temp for your specific material may differ somewhat from coal ash softening.
A cone of ash is observed in the fire chamber, as the temp rises the cone becomes a spherical lump, this is your temp point of conversion.
I'd avoid using dust, you would be better served to somehow control the dust by encapsulating it in a combustible product.
Also your firebox temp needs better control, I'd look at draft and combustion air and how it is introduced into the combustion chamber, keeping in mind we don't know how this is being achieved now