<html><head><style type='text/css'>p { margin: 0; }</style></head><body><div style='font-family: Arial; font-size: 12pt; color: #000000'>Tom (cc Andrew and list):<br><br> Thanks. Professor Prasad is certainly one of my heroes in stove work. It was fun to read (I need to re-read) this report on a helpful down draft design. But char production was not a part of his analysis. I will look more closely to see if there is something there to allow for a char-making design. I think the main issue is predicting something on needed chimney heights - which seems to be in there. But it appears to me that both primary and secondary air were traveling through the fuel - whereas I presume a need to separate the air supplies - as in the TLUD.<br><br> The message (below) by Andrew to the stoves list was at least in part generated by some off-list conversation that we have been having on BLDD and char-making. The issue is why are almost all gasifiers (which can be operated to give sizeable char output) based on BLDD, but (apparently) all (?) char-making stoves are TLUD?<br><br> I hope anyone knowing of a BLDD char-maker will let us know.<br><br> Few items below also on Andrew's e-mail..<br> <br><br><hr id="zwchr"><b>From: </b>"Tom Miles" <tmiles@trmiles.com><br><b>To: </b>"Discussion of biomass cooking stoves" <stoves@lists.bioenergylists.org><br><b>Sent: </b>Thursday, January 12, 2012 5:23:21 PM<br><b>Subject: </b>Re: [Stoves] Inverted top lit updraught<br><br>Krishna Prasad described the downdraft stove in a presentation to ETHOS in<br>2004 <br>http://www.vrac.iastate.edu/ethos/ethos05/proceedings2004/presentations/pras<br>adbiomasscookstoves.pdf<br><br><br>A picture and WBT for Peter Verhaart's down draft barbeque can be found at:<br>http://www.stoves.bioenergylists.org/verhaartbarbeque<br><br>Tom Miles<br><br>-----Original Message-----<br>From: stoves-bounces@lists.bioenergylists.org<br>[mailto:stoves-bounces@lists.bioenergylists.org] On Behalf Of<br>ajheggie@gmail.com<br>Sent: Thursday, January 12, 2012 2:48 PM<br>To: Discussion of biomass cooking stoves<br>Subject: [Stoves] Inverted top lit updraught<br><br>One for Peter Verhaart to comment on perhaps: we probably all know by now<br>the genesis of the inverted down draught stoves which Ronal and Tom Reed<br>expounded early on this list and concurrently Paal was developing with his<br>early Peko Pe and we understand how burning the pyrolysis offgas can offer<br>very low particulates compared with burning whole wood in a conventional<br>updraught stove but is the same true of a down draught stove if the primary<br>air is similarly controlled?<br> <strong>[RWL: I think Piet Verhaart's thoughts would be excellent (for others: Piet's doctoral work was on a BLDD stove). But for this purpose, I am interested right now in whether any BLDD is providing (lots of) char.</strong><br><br>The advantage of stratified down draught ( i.e. where the air moves down<br>through the charge of wood as that also descends through the grate) would<br>seem to be that the fire can be continually stoked. The disadvantage is all<br>the extra pipe work and either needing a hot plate or sunken pots to<br>maintain the chimney depression required to suck the primary air down.<br style="font-weight: bold;"><span style="font-weight: bold;"> [RWL: I think Professor Prasad's paper shows a BLDD design that doesn't suffer from these two drawbacks. But also it doesn't seem to produce char.</span><br><br>Down draught devices are normally intended to gasify all the fuel, often<br>with extra air supplied in the "throat" but what if one was not particularly<br>concerned if a high char ash were left?<br> <span style="font-weight: bold;">[RWL: I have recently been talking with Agua Das [cc'd] about his "Dasifier" - which is incredibly efficient (very high temperatures) with an "ejector" supplying this <span style="font-weight: bold;">extra air</span>. He says he can produce lots of char as well. This is not what I have had in mind - but could be attractive if that intermediate secondary air can be introduced and controlled economically.</span><br><br>For the sake of staying on topic can we avoid the "b" word and just discuss the concept?<br> <span style="font-weight: bold;">[RWL: Hmm. "b" word ? I trust it is OK to talk of saved char (intended for a "b" purpose).</span><br><br style="font-weight: bold;"><span style="font-weight: bold;"> Andrew - thanks for these thoughts.<br><br>Ron<br style="font-weight: bold;"></span><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<br>.org<br><br>for more Biomass Cooking Stoves, News and Information see our web site:<br>http://www.bioenergylists.org/<br><br><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://www.bioenergylists.org/<br><br></div></body></html>