[Stoves] "Those of us who believe that the WBT is critical to stove improvement"

Andrew Heggie aj.heggie at gmail.com
Fri Dec 8 02:22:43 MST 2017


On Thu, 7 Dec 2017 23:55:24 +0000,Crispin Pemberton-Pigott
<crispinpigott at outlook.com> wrote:

>Re the diesel and NOx, I think there is the expectation that the air is in excess in a diesel under all conditions otherwise it smokes like crazy. Not so?

Yes that is correct, there has to be excess air in a diesel for the
(essentially) diffuse flame to meet enough oxygen in the time
available.
My point was that the temperature-pressure-oxygen requirement may be
met at less than full throttle when more oxygen was available
  such that more nitrogen oxides are produced than at full throttle.

>
>We were testing a crossdraft low pressure boiler today at CAU and ?observed something identified by Dr Chunyu Xue from BUCT (sp?). He noted in a presentation to out annual October meeting of experts that the NO was being reduced in the coke bed. Remember that brief conversation? Today (I guess it was yesterday because it is early morning in Urumqi) we calculated the undiluted concentration of NO as the fire bed evolved.
>
>When the fire was about 1/3 lit (but strong flames) it was 583 ppm(v). This is calculated by multiplying the measured vale times (CO2max/CO2measured) to give an undiluted concentration.
>
>As the fire ?developed across the grate back to the door, covering the underside of the hopper, the NO dropped as the active coke bed lengthened (horizontal distance) even as the intensity of the fire rose (a lot).
>
>It dropped from 583 to 525, 480, 420, 380, 320, 290 and so one every few minutes. After it was fully lit and blasting away, it was 200 ppm. To me, it serves as a proof of concept. ?The NO was reduced to N2 and O2. Very obvious and very interesting. It is literally a low NOx burner. Who knew?

I don't know but I would expect hot carbon to reduce nitrogen oxides
to CO and N2 as the firebed is largely devoid of oxygen once the
primary air is used up lower down.
 So at the edge of the bed there may still be a high enough
temperature and excess primary air for nitrogen oxides to form?

Andrew



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