[Stoves] Stoves Digest, Vol 17, Issue 35

Wed Jan 25 14:03:22 CST 2012

Tom,

   I see a *new* list for the first time: 
*gasification at lists.bioenergylists.org*
How do I join this list?
   (Do I send "gasification-request at lists.bioenergylists.org " ??)

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=&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.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: stoves-bounces at lists.bioenergylists.org
> [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of Philip Lloyd
> Sent: Tuesday, January 24, 2012 11:48 PM
> To: stoves at lists.bioenergylists.org
> 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: stoves-bounces at lists.bioenergylists.org
> [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of
> stoves-request at lists.bioenergylists.org
> Sent: 24 January 2012 07:45
> To: stoves at lists.bioenergylists.org
> Subject: Stoves Digest, Vol 17, Issue 35
>
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> Today's Topics:
>
>     1. Re: The upside of Down feed (Alex English)
>     2. Re: The upside of Down feed (rongretlarson at comcast.net)
>     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 (rongretlarson at comcast.net)
>    10. Re: The upside of Down feed (Crispin Pemberton-Pigott)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Mon, 23 Jan 2012 20:45:36 -0500
> From: Alex English<english at kingston.net>
> To: Discussion of biomass cooking stoves
> 	<stoves at lists.bioenergylists.org>
> 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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