<html><head></head><body data-blackberry-caret-color="#00a8df" style="background-color: rgb(255, 255, 255); line-height: initial;"><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">Dear Andrew</div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">The explanation is now clear. There is almost enough O2 in biomass to burn all the Hydrogen but not quite. If there is no carbon burning a great deal of the combustion can take place with no outside air at all. </div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">The term Lambda is used loosely. Testo uses it incorrectly in their computer outputs to describe Excess Air. Lambda is strictly the total air demand, not the excess air only. Suppose the EA is 250%. Then Lambda is 350%. </div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">I agree re the less than 0% EA conditions. The right way to talk about it is Lambda, and that could be less than 100%. </div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">The manufacture of O2 in the fire is the Water Gas Shift Reaction. It would happen using combustion moisture I suppose but I have not seen that definitively. Have definitive measurements though from wet fuel fires. I have not worried about how it happens - I was occupied trying to understand how to get a true calculation of the EA equivalent. The EA value is really a re-expression of the O2 available, not the actual amount of air it is consuming. It is just a way to talk about the chemistry. As I said, ALL the O2 might be coming from the fuel. </div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">I asked two profs about this reaction and the possibility it was manufacturing O2 (and H2). One from a univ in the US said there was no possibility at all this was happening. Prof Lloyd replied, "Of course - happens all the time."</div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">So Prof Lloyd is supported by the data. </div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">Regards</div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">Crispin</div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div> <div style="font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">Sent by Q10</div> <table width="100%" style="background-color:white;border-spacing:0px;"> <tbody><tr><td colspan="2" style="font-size: initial; text-align: initial; background-color: rgb(255, 255, 255);"> <div id="_persistentHeader" style="border-style: solid none none; border-top-color: rgb(181, 196, 223); border-top-width: 1pt; padding: 3pt 0in 0in; font-family: Tahoma, 'BB Alpha Sans', 'Slate Pro'; font-size: 10pt;"> <div><b>From: </b>ajheggie@gmail.com</div><div><b>Sent: </b>Sunday, August 25, 2013 10:28</div><div><b>To: </b>Discussion of biomass cooking stoves</div><div><b>Reply To: </b>Discussion of biomass cooking stoves</div><div><b>Subject: </b>Re: [Stoves] Excess air</div></div></td></tr></tbody></table><div style="border-style: solid none none; border-top-color: rgb(186, 188, 209); border-top-width: 1pt; font-size: initial; text-align: initial; background-color: rgb(255, 255, 255);"></div><br><div id="_originalContent" style="">[Default] On Wed, 21 Aug 2013 21:33:06 +0000,"Crispin<br>Pemberton-Pigott" <crispinpigott@gmail.com> wrote:<br><br>><br>>I followed everything until the end. The last paragraph. <br>"So yes stoichiometric air does vary as wood burns and excess air<br>mirrors this but it is not reasonable to mix this up with the fact<br>that oxygen from combustion air and from the fuel is conserved in the<br>exhaust gases."<br><br>I'll try and rephrase that: for a given dry lump of wood although the<br>surface may be simultaneously pyrolysing and the nascent char burning<br>to ash while the evolved offgas burns the centre is also heating up in<br>the absence of combustion air, the pyrolysis products are also<br>reacting within the mass, so pyrolysis offgas is diffusing out of the<br>lump. This offgas initially has species, like acetic acid that are<br>already moderately oxidised and react with little combustion air to<br>release little heat. Later, as the lump gets hotter, more fuel rich<br>gases like methane, hydrogen and carbon monoxide as well as tar<br>vapours are evolved and these require more oxygen for the secondary<br>combustion.<br><br>As excess air is always necessary to increase the chance of an oxygen<br>molecule reaching fuel molecules as stoich air varies so must excess<br>air to maintain the same level of free oxygen in the exhaust.<br><br>It is free oxygen which we are measuring with a wide band lambda<br>sensor (I think lambda being the accepted character in internal<br>combustion for equivalence ratio even though these sensors cannot<br>measure below zero oxygen as they are cells that generate a voltage<br>dependent on, but not directly, the proportion of oxygen in the flue<br>gas on one side and air on the other. e.g. they will still measure an<br>unvarying zero oxygen even if the fuel:air mixture is so rich CO is<br>being exhausted.)<br><br>>Re coal and Oxygen, there is not so much in the coal but wet coal fires can make O2 during ignition. <br><br>What reaction do you surmise releases this oxygen?<br><br>AJH<br><br>_______________________________________________<br>Stoves mailing list<br><br>to Send a Message to the list, use the email address<br>stoves@lists.bioenergylists.org<br><br>to UNSUBSCRIBE or Change your List Settings use the web page<br>http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org<br><br>for more Biomass Cooking Stoves, News and Information see our web site:<br>http://stoves.bioenergylists.org/<br><br></div></body></html>