Dear all, I just happend to see this statements about the TLUD ND PekoPe and are a bit surprized that Dean, claims "his" TLUD only can use pellets and for how long the pellets lasts in the combustion chamber as a flame and charcoal.
To my knowledge, the real "PekoPe" burns with an open flame for about two hours and glow for another 4-5 houers by using 2,5 kg of pellets made out of wood (pine)..!? The other thing I noted was that "his" TLUD gives a number of 400 mg PM, while Paal`s prototype done at the Aprovech Research Center, only gave 223 mg PM in 2009!? A lot of water has passed in the river Nile since then, even in Zambezi...........:) Good advice: Leave it to others to test and tune the TLUD ND Gasifier Units, please.................... Otto Forester and still a TLUD ND "PekoPe" fan............without a fan........ > From: [email protected] > Sent: 2010-12-05 07:54:22 MET > To: Discussion of biomass cooking stoves [[email protected]] > Subject: [Stoves] Air supply in TLUDs > > > Dean > > I think you are describing below only a TLUD that has no control over the > primary air supply. Or one that has a turn down ratio of unity. We should be > able to do much better. > > I urge having a means of controlling the primary air supply. If one is > intending to consume the produced char, there will be a mighty small flame at > the end or a huge flame at the beginning. > > There are many ways to control the primary air - at low cost. > > > Ron > > > ----- Original Message ----- > From: "Dean Still" <[email protected]> > To: "Discussion of biomass cooking stoves" <[email protected]> > Sent: Thursday, December 2, 2010 10:30:33 PM > Subject: Re: [Stoves] K Smith Article in Energy for Sustainable Development > > Hi All, > > > Adding more air holes in the bottom of the fuel chamber in a TLUD allows > pellets to burn up completely. If users want bio-char they just have to have > fewer holes. Then the char is made since there is not enough air to support > burning it. > > > If it is tuned (!), the TLUD is very low in PM when it does not make smoke > when starting and finishing the burn. CO is also generally low. In the well > tuned TLUD we generally see around 7g of CO and 400mg of PM during the WBT > compared to a carefully operated open fire at 55g CO and 2300mg PM. Generally > the TLUD makes less smoke at the finish with more air holes because all the > wood burns up without making smoke. > > > Isn't it great that a TLUD can be operated in both char making and no char > making modes? > The user can choose whether they want greater fuel efficiency or to make an > agricultural additive. > > > Best, > > > Dean > > > On Wed, Dec 1, 2010 at 7:29 PM, Richard Stanley < [email protected] > > wrote: > > > > Hi Ron, long time eh? > Let me respond in kind, as much as I can at least... > > > > On Nov 29, 2010, at 7:55 PM, [email protected] wrote: > > > > > See some questions/notes below on your message today. You said: > > > " I would buy the one that burned some form of densified non wood biomass > "cleanly" ...... > > [RWL1: Those of us who are promoting char-producing stoves believe that they > are much cleaner than those that only combust. The usual low-cost stoves in > developing countries almost universally use only wood (with some still-minor > use of your briquettes of course). For those new to the subject, the > difference is whether there is a single air supply or two. Does anyone > reading this think that char-making stoves are not inherently cleaner? > First I wish I could take full credit for the briquette idea but if you were > to enter the word fuel briquette on a google search or a you tube survey, you > would need a very tall cuppa java to get through it all these days. The > briquette producer conference we just hosted in east Africa well proves the > point that the adaptations of the process and blends and stoves being tested > are well beyond anything we cooked up through Ben Bryant's initial ideas... > As to cleaner burn the question is two pronged the front end particulate and > aromatics issue / "smoke" and the end burn with the risk of CO which is not > so obvious...Many in the conference and globally now favor higher > concentrations of charcoal dust. Some of these are charring ag residues > beforehand because most see smoke as equivalent to all pollution... The CO > awareness issue is still much in need of greater public awareness and it is > at this end of the combustion cycle that where the char can be produced. I'll > return to this issue subsequently... > > > > > > > But I especially want to support your use of the term "densified non-wood" - > which I think is also much needed in char-making stoves. Nat Mulcahy of World > Stoves always emphasizes the use of "densified non-wood" as one of the main > advantage of his Lucia stove (which could combust or gasify - but he chooses > to operate in only a pyrolysis mode). See his website for his rationales - > which are (in part) similar to yours. > Several questions to you (as the person who probably knows the most on this > densified non-wood cooking issue): > 1a. What are the relative advantages of making (not using) pellets vs > briquettes? > I am not claiming that pellets are 'less better'. In fact they may be far > better given the high surface to volume ratio they present relative to the > briquette. But what is better technically, is only part of the story. Issues > like produce-ability and ease of use in the typical stove with its large > grate for example...these are as or more important tht sheer technical > advantages at eas tin the eyes of the consumers and producers we spoke with.. > > > > > > > It would seem that it should be much easier to "press" (I like your closing > below) pellets than briquettes (especially the "holey" type). Do you have any > data on the relative power or energy and/ or cost requirements for production > of pellets vs briquettes? > There are about 25 generically different briquette presses out on the > internet as we speak. I know of at least two more deisgns in the offing. I > have seen several pellet type presses mostly of the modified meat mincer > type. To make money in the typical rural market across Africa and much of > Latin America, one producer with their hand press of whatever design, has to > crank (or press or screw, or ratchet or lever for that matter) out about 16 > to 20 kgs per day. I do not know what the hand operated pellet presses are > capable of but I would be surprised if it is much different--again pe > individual worker, using some form of hand press. > In either case however, it is not the pressing which limits production of > pettets or briquettes at the hand process level, at least where ag residues > are concerned. It is the sorting and chopping fermenting mashing and blending > of the residues which consumes the greater part of the energy required for > briquette making at the hand /micro scale level. There is a very interesting > technical innovation which will soon make it far more efficient. The guy > doing the work on this is not ready to break the surface 'til he has > something to brag about but a the rate he is moving it will probably be ready > in a month or so...Its really his call to bring it out into the daylight when > he's ready. We're just adding our two cents in here and there.. > > > > > > > > 1b. For those wanting char and not ash, the charred pellet is already in a > wonderful form for application to soils. Pellets mean some extra costs for > the fuel supply in the front end of cooking - but could be a wonderful boon > both in burning more cleanly and evenly and in later application of Biochar > to the soil. The same is possibly/probably true for briquettes - which I > presume break up easily after being pyrolyzed. Do you have any reason to > think briquettes would be better than pellets in either pyrolysis or > char-application terms? > Intersting issue this 'clean burning' idea. Smoke was a big issue amongs the > the participants in the workshop. What seemed to come out of it was the fact > that one does not want to be attempting to try to ignite the whole mass to > flash point in order to get a fire started..The idea is evolving that you > only want to burn the immediate surface to start with.. Pellets can be > ignited quickly becasue of their high surface area to volume ratio. > Briquettes like most larger chunky fuels, have to be either top lit or side > lit or as Robert Williams of the gorila conservati0on project in the DRC has > demonstrated, diagonally lit. The idea is in all cases, to heat only the > surface to ignite it , then progress to succesfully larger mass of fuel. Side > fed stoves, off the Approvecho rocket stove idea, is now well actualised by > Rok Oblak's side fed briquette stove design which is producing remarkable > results (see rokstoves.org---I think its already long archived in the Stoves > list) > > > Forgive me if I am off here but from what I have seen in practice, the > dampening of the stove if not carefully implemented, can generate a sudden > burst of CO. Pellets would seem to be far harder to regulate in this regard > because to be burned optimally, it would seem that --as with the ordinary > mechanised pellet stove sold in the states and Europe at least-- only a few > at a time are fed into the combustion chamber...Now how this could be made > into a continuous feed process with continuous production of char as the > product ---while regulating air flow (as that seems to be essential to the > process)--- could be a real challange.. > > > Char making therefore seems--again, for at least the intended small cookstove > user, to therefore be best handled in a batch process, with larger batches of > fuel being pyrolised at any one time... > In short, I think that for the intended user and stove the briquette would > probably be easier to manage for pyrolsis in a batch process...Frankly > though, I have not ever focused any real effort to make char (on purpose at > least) so anybody's insights more than welcome. > > > > > > > > > You concluded:] > > ".... and would avoid both the wood supply and the char producing problems in > one go ." > > [RWL: 2a. Re the first issue of supply (with which I agree), I have recently > read an article (author's name forgotten - I will try to find it) that showed > a breakdown of the well known global net primary productivity (NPP) number of > about 60 Gt C/yr. They had about half going into wood and half into leaves - > a ratio I had not previously seen. Since you are promoting the former > (leaves) over the latter (wood) - and because almost all rural stove users > are now using only wood (and even many briquettes and pellets seem to be made > up of ground-up or chipped wood), have you seen this relative photosynthesis > production ratio - which would seem to imply a huge wasted resource all over > the world? I have not seen this figure before but would be curious as to how > it as derived. In more immediately recogniseable terms however, the fuel > value of the leaves off any one species compared to the fuel value off its > wood would offer an interesting if not more direclty applicable comparison > for any one project site. Ratios of net non wood biomass energy values of 10 > to 50--- to net wood biomass energy values of 1, would not be unreasonable. > On the one hand you have a far lower volume of a less dense energy supply per > year throughout the tree's life (eg., leaves) being offset by the tree's > greater wood energy supply albeit afforded only once during its lifetime... > In our Theory and Applications manual we did lots of analysis in concert with > a japanese agricultural research organisation working in Uganda with then, > already several years experience, to derive fuel carrying capacities from non > wood biomass residue per unit area. We did this over various land forms and > land uses including of course normal offtake for soil tilth, as well as for > feed and fodder here appropriate . And we have not begun to consider of > course processing waste: paper, cardboard, sawdust, rice husks, charcoal dust > and crumbs ( some 20% of the total of the charoal being produced winds up on > the seller's floor as such waste).. Such processed biomass residues can > easily constitute 50% or more of the whole briquette. Its a huge amount of > waste in tems of available non wood biomass but outrageously huge whenyou > combine that with the commercially processed residues. > > > > > > > > > 2b. But I don't understand your term "char producing problems". To me there > are only benefits and advantages (at least with kitchen stoves). If you meant > the horrible production of most charcoal out in the boondocks - with global > warming and carcinogenic gases much worse than CO2 being produced - then I > agree. To prove that it is better for society to promote household production > of Biochar (char placed in the ground) will be the subject of my next > message. Briefly it is that we need to make the economic argument that > Biochar's two main advantages (carbon sequestration and soil improvements) > outweigh the further combustion of the char for its energy value. Two main > reasons that I think we can make this argument (which I do not contend has > already been proven). First is the 2:1 advantage in the three-flows of money > (which seem in the same ballpark). But more important is that the first two > monetary flows (climate and soils) are both investments - with good payback > over long time periods. The energy application of the char is only a single > use - no out-year advantages at all. More coming on the many out-year > advantages of Biochar. > > This is not to suggest that you do not believe in all this already - but > others could interpret your sentence to favor burning of "densified non-woody > biomass" rather than pyrolysis of the same. > > Ron, the argument is not whether or not it is justified on economic terms. I > am sure the numbers prove its viability, especially with all teh intellectual > horesopower working on the issue: > But like much of development work, its not purely an intellectual issue: Its > about the cultural ease and the real cost of embedding the concept ...Thats > the reality you have to reach its the so called boondocks where the 90% of > the rest of us live. > > > The notion of promoting a longer term reward in a subsistence level economy > at the cost of an immediate efficiency (viz., shortening the length of > cooking by dampening it for production of biochar which may generate some > income down the line, is a hard sell... > > > It matters not whether I personally favor burning biomass over controlled > pyrolsis but what the actual user actually favors. They do what you and I > would do under their own circumstances--They use what they have for that day > as optimally as they can use it. Unless they can be charring for making > charcoal, I do not see them investing the char in the soil for returns over > the next several years--- Not at least without some form of very intensive, > sustained awareness promotion augmented by long term assistance to offset > their immediate added fuel costs. > > > Lest we scoff at that notion, one need only ask how many of us with our onw > fuller stomachs, better education greate raccess to resources and far greater > global awareness, are using biofuels or electric vehicles as we rant on about > global warming..Look athe proposed subsidies tax rebates etc offered to > incentivise the change look at teh politics and hte lobbying to maintain the > status quo and look a the results. Its all abit relative, eh. When you can > say that you are prepared to offset the user's losses and are prepared to > really invest in the policy and public awareness promotion of Biochar then > its time to talk about implementing it...And I say this as a technical > convert to the idea... > > > Cheers, > > > > Richard Stanley > www.legacyfound.org > > > ps., If anybody is interested we put up a summary of the conference in te > news seciton of or website..Great stuff is happening in the briquetting > world. > > > > > > > > > > > Ron] > > > pressing on, > > > Richard Stanley > www.legacyfound.org > > > > > > On Nov 29, 2010, at 4:12 PM, Crispin Pemberton-Pigott wrote: > [RWL: I have snipped this to keep the responses separate - being different > issues.] > > > > > > Dear Friends > > I agree with Ron that $10 is a believable figure for an improved stove with a > dramatic (90%) reduction in emissions of PM. For the +$50 stove > > <snipped> > > > > > _______________________________________________ > Stoves mailing list > > to Send a Message to the list, use the email address > Stoves mailing list > > to UNSUBSCRIBE or Change your List Settings use the web page > http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org > > > for more Biomass Cooking Stoves, News and Information see our web site: > http://www.bioenergylists.org/ > [email protected] > http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org > > > > > _______________________________________________ > Stoves mailing list > > to Send a Message to the list, use the email address > Stoves mailing list > > to UNSUBSCRIBE or Change your List Settings use the web page > http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org > > > for more Biomass Cooking Stoves, News and Information see our web site: > http://www.bioenergylists.org/ > [email protected] > http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org >
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