[Stoves] Torrifaction topics Re: Pellet stoves - risks
kgharris
kgharris at sonic.net
Wed Sep 9 22:51:43 CDT 2015
Frank and All,
Julian Winter and I have both been experimenting with the combustor section of the ND-TLUD stove to improve the burning of the wood gas. Jock Gill was also trying some inovative things. I have not heard how Jock's design worked out, but Julian and I have had some good results. I belive that changing the combustion set-up, as you mention, can help. At the Aprovecho open house after ETHOS last January, some stovers tried one of my Wonderwerk Strata test combustors on a forced air rice hull stove and it cleaned the flame quite nicely. A good combustor should be able to effectively burn most gas combinations that come it's way. It should include good mixing of gas and air, concentration of the heat, and an extended dwell time for the flame in that concentrated heat. The Strata test combustor includes all of these. It could be made adjustable for specific fuels. Putting a production line version on top of a marginal TLUD would improve its performance. Since many TLUDs are marginal, this could be a simple way to clean them up without having to redesign, rebuild or replace the stove itself. The Strata combustor principles will have little to no effect on a well designed TLUD, but should work quite well for any TLUD that has a diffusion flame comming out of it, and make it into a tier 4 stove combination. Strata test combustors have tested at tier 4 at Aprovecho in the past.
With respect,
Kirk
Santa Rosa, CA. USA
----- Original Message -----
From: Frank Shields
To: Discussion of biomass cooking stoves
Cc: Marvin Lambert - Calif.-S.F.
Sent: Wednesday, September 09, 2015 9:42 AM
Subject: Re: [Stoves] Torrifaction topics Re: Pellet stoves - risks
Dear Alex,
I think the fuel and the environment above the fuel is both of equal importance. So do we change the fuel or the combustion set-up? that is the question.
A stove system that is able to burn a wide variety of fuels and widely sold may be difficult and/or expensive to make adjustments for a specific fuel. So in this case if it is easy to change the fuel that may be preferred. I think the answer to change the fuel or the stove system depends on the amount of work and expense involved.
Thats the way I look at it today. : )
Regards
Frank
Frank Shields
franke at cruzio.com
On Sep 9, 2015, at 9:23 AM, alex english <aenglish444 at gmail.com> wrote:
Frank,
If there are emissions that derive from fuel directly and then escape further 'processing' by flame environments by sneaking by , then they might be called something like primary fuel derived emissions. PFDEs. It is safe to say, I think,that most of these would be transformed into products of complete or incomplete combustion in and around the flame. I may be confused, but this mix would likely have less to do with the fuel than the environment above fuel.
Hmm
Alex
On 2015-09-09 8:55 AM, "Frank Shields" <franke at cruzio.com> wrote:
Dear Paul and Stovers,
For ‘user-acceptance’ and ‘market driven’ I would think preparing the fuel optimized for your stove that quickly boils water with little dirty emissions is one and the same.
I would think that would be drying and, perhaps as Dean has mentioned, driving off some of the early volatiles that may pass the secondary before complete combustion.
Paul - Do you have information as to the optimum size and shape the biomass should be for your stove? That should be determined.
Then we go to testing the parameters of the biomass like carbon bulk density and carbon particle density along with water soluble sugars and lipids that may contribute to poor emissions. It could be as simple as soaking and draining out constituents to improve the quality as well as heating to drive off the early volatiles.
But first we need to find what it is in the fuel that causes the poor emissions. That could be to take some problem biomass and get a baseline from testing.
Then pre-heat to drive off early volatiles and re-test. Then using another batch soak in hot water, drain, dry and re-test. And finally soak in a solvent, drain, dry and re-test.
Using emissions tests to get ratios of emission components and particles might be enough to determine success. Or add helium surrogate to get absolute concentrations as they are produced might be info that would help.
Regards
Frank
Frank Shields
franke at cruzio.com
On Sep 9, 2015, at 8:20 AM, Paul Anderson <psanders at ilstu.edu> wrote:
Frank and Stovers,
My simplistic interest in the "induced drying" of biomass fuels is related to improving the user-acceptance of the TLUD cookstoves and the establishment of some fuel marketing chain. The degree of drying / torrification would be market driven, not related to emissions or technical characteristics of the resultant fuels.
As the degree of drying / heating of the fuels increases, the cost of that processing will rise. So I favor the minimum treatment that will benefit the customer and will justify the increase in fuel price.
A favorable situation would be to use essentially waste heat to prepare the future fuel supplies. Or expend a small amount of fuel to prepare a much larger amount of fuel that will be sold with sustainable profitability.
Paul
Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
Email: psanders at ilstu.edu
Skype: paultlud Phone: +1-309-452-7072
Website: www.drtlud.com
On 9/8/2015 3:55 PM, Frank Shields wrote:
Dear Paul,
Making batches of different degrees of torrification biofuels is one thing and then testing and interpreting the results is another.
Do we measure success on emissions or time it takes to boil water? And them we have other variables like bulk carbon density and particle carbon density. Volatiles and adding moisture. Size and shape will be important.
So once we figure out a way of making constant quality material for testing there is still a lot of research work to do. Agreeing on what we use as a measure of success is the first.
regards
Frank
Frank Shields
franke at cruzio.com
On Sep 6, 2015, at 5:32 AM, Paul Anderson <psanders at ilstu.edu> wrote:
Dear all,
While agreeing with Frank and Dean, I suggest that there are sufficient "degrees of torrification" that we should subdivide the discussion.
1. Wet or green wood High moisture content (MC)
2. Dried in 20% MC range
3. Dried to 10% MC or less
4. Kiln dried (heated to ???? degrees C)
5. Super dried (heated to maybe 120 C)
6. Toasted (slightly browning) 120 to 180 C ???
7. Early torrified 180 - 240 C ??
8. Fully torrified 240 - 300 C ??
9. Undergoing pyrolysis above 300 C ???
10. And then we have different "chars" based on temperatures during production, 400 C, 450 C, 550 C, 700 C, 900 C
LOTS of question marks there. Frank and others can refine this much better. Issues of MC and temperatures and "names" (and related to sufficient time to have the heat impact reach the center of the pieces of biomass, not just flash heating), and probably more variables.
To just say "torrified" leaves too many uncertainties and possible mis-understandings / assumptions by the large number of readers in different cultures and with different experiences.
I can say that TLUD stoves (when properly made and with consistent MC in the fuels) work very well with the 3, 4, 5, and 6 (above) fuels. They do not like much moisture content, and they do not want the fuel to be already partially charred.
Reasonable quality fuel supply is so important for TLUD acceptance. More work could be done about this.
Paul
Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
Email: psanders at ilstu.edu
Skype: paultlud Phone: +1-309-452-7072
Website: www.drtlud.comOn 9/5/2015 11:45 PM, Frank Shields wrote:
Dear Dean, Stovers,
I have not worked with stoves but working with all types of pellets (paper, manures, etc.) and good quality wood pellets I find they burn in pipes very poorly and seem they are really just good for pellet stoves dropping in one at a time.
I think you may be on to something in regards to torrifying to some extent before using to get a cleaner combustion. I see the real challenge is quality control because torrification takes place in a very narrow range and it is so easy to have a ‘run-a-way’ combustion that heats higher than the setting you want. I was able to achieve that in my pipes but only after much practice and s l o w l y raising the temperature to desired amount. Not sure how this would be done commercially. It would be a very interesting project.
We also may be able to get clean combustion by finding constituents in the pellets (and all biomass for that matter) that create these large organic volatile structures that give problems and eliminate them from the fuel.
Regards
Frank
Frank Shields
franke at cruzio.com
On Sep 3, 2015, at 12:28 PM, Dean Still <deankstill at gmail.com> wrote:
Hi Frank,
After limited experience in Uganda and China my experience is that it's not easy to make clean burning recipes for biomass pellets.
Seems like the torrified pellets emit less PM but we need to do more tests.
Best,
Dean
On Thu, Sep 3, 2015 at 8:44 AM, Frank Shields <franke at cruzio.com> wrote:
Dear Chispin and stovers
Of course no mention of the quality of the pellets! In the U.S. The go through standard testing and results labeled
On bags. But pellets are made of all sorts of materials and energy values and volatile profiles. It would seem this would be part of the discussion.
Thanks
Frank
Sent from my iPhone
On Sep 3, 2015, at 6:13 AM, Crispin Pemberton-Pigott <crispinpigott at outlook.com> wrote:
Dear Friends
There is a broad move around the world to create pelleted fuel from biomass and burn it in tighter spaces. This report was noted in the Alliance for Green Heat newsletter:
Updated on the Mt. Vernon pellet stove recall
Last month, we reported on the recall of 2,000 Mt. Vernon E2 pellet stoves after about 6 experienced explosions that shattered the glass in the front door. No injuries have been reported. The Alliance wrote to HHT asking for clarifications about what caused the malfunction and whether the stove would be 3rd party tested again for safety. Click here for a copy of the HHT response.
The drive to create better combustion often means having a staged gasification-then-burning type of design. That may be a source of problems.
I know of at least one instance of a very modern TLUD coal stove explosion in Ulaanbaatar when the operator refuelled it with a significant amount of lignite (high volatiles) while it was already very hot. This generated a huge amount of combustible gas while simultaneously extinguishing the gas flame. Eventually it heated up to the point that the gas ignited and it blew flaming fuel out of the top of the stove, around the room. A public education campaign tried to prevent exactly this sort of mis-operation.
Regards
Crispin
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Executive Director
Aprovecho Research Center
PO Box 1175
76132 Blue Mountain School Road
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(541) 767-0287
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