Lloyd,
I just subscribed you to the gasification list so you should get a welcome message. I have sponsored and hosted the gasification list since about 1996. There are about 1200 members. We maintain a website to support the list at: http://www.gasifiers.bioenergylists.org/ Regards, Tom T R Miles Technical Consultants, Inc. [email protected] www.trmiles.com From: [email protected] [mailto:[email protected]] On Behalf Of Lloyd Helferty Sent: Wednesday, January 25, 2012 12:03 PM To: Discussion of biomass cooking stoves Subject: Re: [Stoves] Stoves Digest, Vol 17, Issue 35 Tom, I see a *new* list for the first time: [email protected] How do I join this list? (Do I send <mailto:[email protected]> "[email protected] " ??) Regards, Lloyd Helferty, Engineering Technologist Principal, Biochar Consulting (Canada) www.biochar-consulting.ca 48 Suncrest Blvd, Thornhill, ON, Canada 905-707-8754 **NEW CELL: 647-886-8754 NEW** Skype: lloyd.helferty Steering Committee coordinator NEW Canadian Biochar Initiative (New CBI) President, Co-founder & CBI Liaison, Biochar-Ontario Advisory Committee Member, IBI http://www.linkedin.com/groups?gid=1404717 http://www.facebook.com/group.php?gid=42237506675 http://groups.google.com/group/biochar-ontario http://www.meetup.com/biocharontario/ http://grassrootsintelligence.blogspot.com www.biochar.ca Biochar Offsets Group: http://www.linkedin.com/groups?home= <http://www.linkedin.com/groups?home=&gid=2446475> &gid=2446475 A nation that destroys its soil, destroys itself. - Franklin D. Roosevelt On 2012-01-25 12:20 PM, Tom Miles wrote: Philip, Thanks for the reference. It looks like the CarboConsult gasifier from South Africa. <http://www.carboconsult.com/> http://www.carboconsult.com/ <http://www.erc.uct.ac.za/jesa/jesa-currentabstracts.htm> http://www.erc.uct.ac.za/jesa/jesa-currentabstracts.htm Volume 22 No 4: December 2011 The technical pre-feasibility to use briquettes made from wood and agricultural waste for gasification in a downdraft gasifier for electricity generation Pholoso Malatji, Ntshengedzeni Sampson Mamphweli and Martina Meincken Biomass can be converted to energy through various thermochemical and biological processes. Gasification is one of the thermochemical processes that has recently gained popularity, because it achieves higher conversion efficiencies than, for example, incinerators, boilers or furnaces. Fixed-bed downdraft gasifiers are preferred for electricity generation, because they produce very little tar, but on the other hand, they are limited with regard to biomass properties, such as particle size, bulk density and moisture content. Biomass material with a heterogeneous size is usually processed into pellets or briquettes, which have to be mechanically strong enough to be handled. Cohesive strength is provided by residual moisture and lignin present in most biomass. However, the briquetting process becomes more complicated if one wants to add agricultural waste products that do not necessarily contain lignin as binders. The aim of this work was to process wood chips, grape skins and chicken litter into briquettes that are mechanically stable and have a sufficiently high energy content, as well as adequate bulk density for gasification. The performance of these briquettes in a downdraft gasifier was simulated with a program developed for wood, which was modified to optimise the briquette yield. The results showed a gasification performance comparable to solid pine wood, implying that the blended briquettes could be used as fuel for a downdraft biomass gasifier. Unfortunately, the briquettes proved too instable to experimentally verify the performance in a gasifier. This paper describes the properties of the briquettes as well as the gasification simulation results. Tom -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Philip Lloyd Sent: Tuesday, January 24, 2012 11:48 PM To: [email protected] Subject: Re: [Stoves] Stoves Digest, Vol 17, Issue 35 The latest edition of Journal of Energy in Southern Africa, Vol 22 No4 (November 2011) has an article on the use of biowaste briquettes in a downdraft gasifier for electricity production (pp 2-7) Prof Philip Lloyd Energy Institute Cape Peninsula University of Technology PO Box 652, Cape Town 8000 Tel: +27 21 460 4216 Fax: +27 21 460 3828 Cell: 083 441 5247 -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: 24 January 2012 07:45 To: [email protected] Subject: Stoves Digest, Vol 17, Issue 35 Send Stoves mailing list submissions to [email protected] To subscribe or unsubscribe via the World Wide Web, visit http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists .org or, via email, send a message with subject or body 'help' to [email protected] You can reach the person managing the list at [email protected] When replying, please edit your Subject line so it is more specific than "Re: Contents of Stoves digest..." Today's Topics: 1. Re: The upside of Down feed (Alex English) 2. Re: The upside of Down feed ([email protected]) 3. Re: [Ethos] ETHOS schedule (Choppalli Venkata Krishna) 4. Re: The upside of Down feed (Crispin Pemberton-Pigott) 5. Re: [Ethos] ETHOS schedule (Otto Formo) 6. Re: [Ethos] ETHOS schedule (Alex English) 7. Re: [Ethos] ETHOS schedule (Tom Miles) 8. Total Energy Wiki launched (Crispin Pemberton-Pigott) 9. Re: The upside of Down feed ([email protected]) 10. Re: The upside of Down feed (Crispin Pemberton-Pigott) ---------------------------------------------------------------------- Message: 1 Date: Mon, 23 Jan 2012 20:45:36 -0500 From: Alex English <mailto:[email protected]> <[email protected]> To: Discussion of biomass cooking stoves <mailto:[email protected]> <[email protected]> Subject: Re: [Stoves] The upside of Down feed Dear Crispin, On 22/01/2012 10:36 PM, Crispin Pemberton-Pigott wrote: Dear Alex This is interesting news. The grate looks great, and if there is a pile of char that is maintained in front, we must conspire to burn it. Not so fast. I rather like the idea of a naturally formed biochar venturi:) To review, it is a crossdraft fire with all the advantages inherent in it: refuellable and lots of room for flames. If the char builds up in front of the hopper but self-limits (i.e. burns away) then it has to be eaten by the passing flame and available O2. That being so, I see a couple of options. One is to admit air through some small holes (1.6, 2.0mm) drilled under the early part of the pile (on the grate side of the pile). That will bleed air under the char which is a good way to burn it. Another is to change the shape of the pipe in that area to allow ash to drop. I presume at the moment the ash is blown into the larger chamber of the stove. I see the odd spark or glowing particle fly into the stove. This is what you see in most pellet stoves which do tend to have relatively low PM emissions. In part that has to do with the way the size of the particles in the pellet ('sawdust' is really tiny wood chips) and how they tend to hold together. When the hopper does runs out of fuel the added air flow literally blows whole charred pellets into the stove. A chimney draft is nothing to sneeze at, so to speak. It is highly likely you have a fairly large PM10 number compared with the same fuel burned in a pile in that larger chamber because of lofted ash. I am really pleased to hear that the flow is so reliable. I have some really short fat pellets here which are probably going to feed well because they are nearly marbles. Probably made with one of those trochoid, concentric-ring pellet formers. As for the fire rising into the hopper, that is not going to happen if the air velocity is high enough. Conditions we have observed it is when the velocity is quite low. If the heat is enough, a rising current of heated air and gas circulates in the fuel immediately above the burning layer and the fire works its way up. That can only happen if a) there is some air (especially from above) or b) the fuel is volatile enough to run an air-free charring burn in the present of enough heat. The advantage of coal, even with a highly volatiles one like the lignite from Nalaikh mine, it is still less volatile than wood. The talk of torrefied pellets intrigues me for that reason. It is more likely to behave like slow roasting coal. Very controllable. There are small coal pellets, say 16mm diameter which might feed well too. Is there any reason you can think of that the hopper, feed tube and burning chamber should be round? No. If you pass by the house I can show you a stove body that your burner will directly attach to with several novel features. It won't be shown until March and sort of solves the 'rest of a stove' for you. I am pretty sure you will like it. It /might/ address the PM10 issue, or not, and solves the heat extraction issues for cooking and heating. I have some Kanthal wire here which we are recommending for grate material. It will work well for you and will hardly get hot at all. If some small bits of fuel drop through (being ahead of the grate) a pocket can be provided underneath to let them smoulder, feeding CO and C and H2 into the beginning of the fire. No problem. The arrangement is made similarly on the SeTAR BLDD5 with the smoulderings fed into the flaming portion of the pipe. The reason I mention a wire grate is it is cheap and easy to make. But like the layered flats too. It should be possible to punch that in a single stroke with the right tool. How deep is the fuel in the hopper? 40 cm. I have materials to go up to 100cm, and I could take it up to near the ceiling with some stove pipe, though I might have to counter balance the stove:) I tried a number of things with hopper shape and decided there is a general rule about bridging which is the following: if the hopper tapers inwards the point of burning, there is an upper limit to the height of the fuel for each degree of narrowing. I tried shoulders too and they are OK further up (for example, within 1 hopper width of the top of the fuel pile). On all cases, if the fuel is compressed by pushing down on it or by stacking lots of fuel up, bridging occurs just above the beginning of the taper. These pellets are highly resistant to bridging. On the other hand I have seen chips defy gravity:) The solution is agitation or a non-tapering hopper bottom. This is bound to be affected by the surface smoothness of the fuel particle. If the pellets are shiny and hard that has to be a help avoid bridging, right? I am impressed that you are able to keep it feeding so well with such a significant narrowing. It is difficult to measure but the pellet flow is in fact air (wind) assisted. However they are more bullet than sail. Small dry wood chips are sails and if they make it down through the hopper, they blow right out of the tube. To you think it is necessary to tilt the flame tube downwards at all? If the char pushed ahead it would be burned by the continuous heat of the flame. Using wood, I can report that I have seen flames reaching more than 24 inches along the tube so you may get better combustion efficiency by lengthening the one you have. Yes, a view of the flame is useful for understanding the process but is not ideal for combustion. Thanks for an interesting (tiny) burner idea. If you bring it here I have some 5mm switchgrass pellets I have had difficulty burning it anything yet. Maybe... I suspect the ash would bung it up, but maybe...not. Alex <snip>
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