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</o:shapelayout></xml><![endif]--></head><body lang=EN-CA link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Dear Andrew<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><div><p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:#1F497D'>></span></b>> The next issue is the excess air quantity.<br><br><span style='color:#1F497D'>></span>Yes I know you preheat secondary air but I was wondering what the effect<br><span style='color:#1F497D'>></span>would be on preheating as a test. Generally excess air acts to quench and<br><span style='color:#1F497D'>></span>dilute the reaction. I was just wondering if an experimental external<br><span style='color:#1F497D'>></span>heating element for the secondary air supply would make any changes to<br><span style='color:#1F497D'>></span>the pm. <span style='color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>We are able with coal to demonstrate things that are really difficult with biomass so the understanding of how the fire reacts is probably better. There are two ways to increase the CO (which if there are volatiles left in the coal, usually means an increase in PM). This observation extends the piece I wrote a few months ago about getting secondary air through the grate. One is to cut the primary air supply which reduces the burn rate, which means there is more air left over at the end, which means there is a greater quantity of excess air. This happens when a portion of the primary air is in fact shot through to become secondary air above the grate.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>The second is to increase the amount of secondary air that is provided separately. It turns out there is always a minimum excess air rate obtainable for each construction of grate, hopper and combustion chamber. Remember the discussion about the thickness of the fuel on the grate being used to determine the excess air level? When things are balanced for minimum excess air (which means in consequence, minimum PM and CO) the is just the right balance of fuel on the grate burning at a time, the right amount of primary air to burn it, and the right quantity secondary air to complete the burn.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>The low PM we are seeing is because of the unusually low EA level (for a domestic stove) and or the elimination of the hydrocarbons late in the burn which happens eventually.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>></span>It's really only spark ignition reciprocating engines that need<br><span style='color:#1F497D'>></span>air:fuel close to stoichiometric most other combustion processes trade<br><span style='color:#1F497D'>></span>off the extra air massflow with the better chance of a fuel, or Product<br><span style='color:#1F497D'>></span>of Incomplete Combustion, particle meeting an oxygen molecule.<br><br><span style='color:#1F497D'>></span>In fact I imagine the pm rate would drop dramatically if the secondary air<br><span style='color:#1F497D'>></span>were enhanced with O2, though of course the increased temperatures may<br><span style='color:#1F497D'>></span>have a non intuitive effect.<br><br><span style='color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Testing of a cast iron coal stove last week showed a pretty low PM level even when the EA was far too low by any normal standard. The secret was the high temperature of the combustion area.<o:p></o:p></span></p><p class=MsoNormal><br>There will be a compromise to be made because the graphs of lambda, CO,<br>PICs and pm will not all map to a single point.<br><br><span style='color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>It might be a bit early to say that for all fuels. In other words it might be true for certain fuels and not others.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>></span>Is there evidence that these smaller than pm2.5 particles are as or more<br>dangerous? <span style='color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>According to WHO and Kirk Smith, yes. The technology is available to find PM 0.020 (20 nanometres). I expect as soon as we look for them, all sorts of things will show up and it will all be worse that we thought.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>>></span>We have a long way to go...<br><br><span style='color:#1F497D'>></span>Yes but your recent pictures of the modification to an existing, in use,<br>stoves show there are big improvements to be made which should be readily<br>accepted. Eliminating PMs will reach a limit below which we will struggle<br>and we're not near yet<br><br><span style='color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>I sure hope so. The reduction is significant so I will post charts later when they are confirmed. Prof Lodoysamba has been running a stove that was built from scratch to optimise current understandings. $70 made with new 3mm mild steel. He reports that it works really well and made three refuelings yesterday to see how it affected the operation when adding duff coal (powder and small bits). We will have Ulzii test it in his ger as soon as possible. He has been surviving the bitter weather while learning how to light and refuel his modified version made 8 days ago (attached). That means we changed his existing stove by adding a 28 cm long pipe cut are 45 degrees both ends. You can see the entrance of the pipe. It goes to the left end of the heat exchanger on the back of the stove. The pictures some have downloaded are of the ‘professional’ version.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>[snip]<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>></span>An interesting boiler related problem, that has<br><span style='color:#1F497D'>></span>shown up laxness in installation, is that most urban dwellers have<br><span style='color:#1F497D'>></span>heating by gas condensing boilers which require a condensate drain. Where<br><span style='color:#1F497D'>></span>this drain has been poorly installed in an exposed position, and the<br><span style='color:#1F497D'>></span>acidic condensate frozen, it has caused the boiler to cut out.<br><br><span style='color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Wow. There is a similar problem with toilet supply pipes and even water heating systems in UB. The simple cure is to run a small stream of water continuously into the drain to keep it above 0 C. This is widely used in the far north of Canada and is a requirement for connection to the sewage system.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>List readers in the NE US may find this trick prevents problems during the coming couple of weeks of Nor’Easters.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Regards<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Crispin<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p></div></div></body></html>