[Stoves] Gasifier without chopping the fuel into small pieces
Ronal Larson
rongretlarson at comcast.net
Sat Jul 2 11:07:14 CDT 2022
Tom,list, Kevin, Crispin
Thanks for the added information. I got interested because of the term: "Flaming pyrolysis”. The word “pyrolysis” is so often used with charcoal making that I got caught off-guard. This especially because I know next to nothing about gasificationn.
I view it a real shame that many pyrolysis and char-making papers also use the word “gasification”
. If I wanted to identify papers that don’t discuss char-making I would use the word “gasification”. I forgot that rule this time.
The term “Prosopsis” was new to me - but that term includes mesquite - which I know a little about. Both terms are important to biochar and stoves because. the Kenya folk were trying to eliminate Prosopsis - which has ruined a lot of land (and cutting blades - you note).
I wonder if anyone has statistics on the global magnitude of this harmful biomass resource for production of biochar - for both stove and CDR reasons. Another good reason to build better biomass using stoves.
The paper has a cite for a pyrolysis paper by Ken Bryden, founder of the annual January ETHOS stove meetings. I have requested a copy.
Re using this paper to help better understand air flow in Kevin McLean’s Sun24 modified 3-stone stove - nothing here. But I may have seen a way to better understand that radial (not up or down - sort of like “cross”) air flow in Kevin’s design. More later on that. In this “cross-flow” paper, much of the air flow is up in the pyrolysis region.
Ron
> On Jun 30, 2022, at 4:55 PM, tmiles at trmiles.com wrote:
>
> Crispin, Ron,
>
> Saravanakumar is still active in research. This was an attempt to gasify Prosopis without chipping it. I major Prosopis project in Kenya failed a few years ago partly because they kept wearing out knives in their Finnish chipper. It was designed as a cross draft gasifier which was intended to produce gas.
>
> There have been various cross gas gasifiers including one developed here to generate power from coffee husks. My favorite cross draft design was developed by Foster Wheeler in Hartlepool, UK, in 1980 for gasifying tires. It was called “Tyrolysis”. The intent was to pyrolyze the tires and make a heating oil product. It did not survive. Thermal conversion of tires is a challenge in any direction.
>
> Tom
>
> From: Stoves <stoves-bounces at lists.bioenergylists.org <mailto:stoves-bounces at lists.bioenergylists.org>> On Behalf Of Crispin Pemberton-Pigott
> Sent: Thursday, June 30, 2022 1:33 PM
> To: Stoves <stoves at lists.bioenergylists.org <mailto:stoves at lists.bioenergylists.org>>
> Subject: Re: [Stoves] Gasifier without chopping the fuel into small pieces
>
> Dear Ron
>
> I thought it was a cross draft stove because the primary air enters horizontally and the gases exit horizontally on the other side.
>
> I see an air channel going to the right and up. I doubt that is an essential part of the combustion. When building a crossdraft stove it is necessary either to blow air down from the top of the fuel, or to vent gases produced in the fuel hopper.
>
> I haven't decided if Saravanakumar is trying to make and collect char, of it he is focussed on getting a combustible gas as the main product. He is certainly not trying to cook.
>
> I found his PhD thesis and his research is focussed on innovative combustion processes. What I found unusual with this paper was the intention to get good quality gas from chopped branches.
>
> The 10 KW power rate is not a surprise given the fuel size. It is hard to get a small number of branches to easily easily. Making it bigger will definitely make the result more predictable.
>
> It is nice to see that Tom Reed was a co-author. It must have been one of his last journal articles.
>
> Regards
> Crispin
>
> From: rongretlarson at comcast.net <mailto:rongretlarson at comcast.net>
>
> Crispin and list:
>
> Yes - an interesting paper. New to me, although a few years old.
>
> One could also describe this as a bottom lit updraft (BLUD) stove - which is usually down played. as desirable. And it has some relationships also to Rockets.- which are similarly bottom lit
>
> I doubt of much use to anyone working on family sized cook stoves - with its rating around 10 kWth. Users at that level won’t mind the needed blower.
> This apparently does a good job in minimizing time spent tending the fire (as does Kevin;’s and TLUDs).
>
> What I found most interesting is better understanding the term "cross draft” - which is inherent also in Kevin McLean’s “Sun24”. But not TLUds using chips or pellets or holey briquettes or ball-shaped fuel..
> “Cross draft” here meaning horizontal - neither “up”, nor down””. But there is clearly also updraft here along two of the four sides
>
> The word “cross”. meaning that pyrolysis of the central portion of the long (60+ cm) fuel pieces occurs using hot O2 coming from each end of the gaps between 3 (or 4) round horizontal cylindrical pieces of tree “trunks” (maybe limbs).
> Being close together it seems much easier for the O2 to get to the pyrolysis region with inner inner horizontal air, not inner vertical air.
>
> This is the situation also in Kevin’s stove. Big difference is that Kevin’s O2 starts moving radially in after flowing (pushed) downward, not being pushed upward.
>
> I have looked for and never found data on pressure differences at a pyrolysis front. This paper tells me that the pressure is lower at the inside glowing-flaming pyrolysis front. Complicated also by pyrolysis occurring with flames above and below logs and probably some flame motion inward (or outward.
>
> So it would seem that then air flow is fairly complicated where the pyrolysis gases are exiting the horizontal tree trunks. Hot gases are exiting, but O2 also has to be entering.
>
> I don’t see this as helping make for cheaper cooking. Certainly not for making char (although a lot more could be made if desired I presume.)
> TDR probably pretty good since there is a blower.
>
> Anyone able to add to the air flow near the horizontally exiting pyrolysis gases? Both here and in Kevin’s char-making stove?
>
> Ron
>
>
>
>> On Jun 29, 2022, at 12:46 PM, Crispin Pemberton-Pigott <crispinpigott at outlook.com <mailto:crispinpigott at outlook.com>> wrote:
>>
>> Dear Friends
>>
>> There is a paper by A. Saravanakumar, T.M. Haridasan, Thomas B. Reed which I would like to bring to your attention.
>>
>> A frequent complaint about gasifiers is that the fuel ahs to be chipped or reduced to mall pieces. This paper explores the gasification of stick wood in a rather interesting manner. It will not be of interest to everyone, but is worth a look and has some solid theory and construction advice.
>>
>> It is called Flaming pyrolysis model of the fixed bed cross draft long-stick wood gasifier.
>>
>> You can see it (free) for research and discussion purposes at
>>
>> https://www.academia.edu/4295996/Flaming_pyrolysis_model_of_the_fixed_bed_cross_draft_long_stick_wood_gasifier <https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.academia.edu%2F4295996%2FFlaming_pyrolysis_model_of_the_fixed_bed_cross_draft_long_stick_wood_gasifier&data=05%7C01%7C%7C5097d47386b746b1ce9208da5acac250%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637922124136666827%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=BaB4F8ZhCVutsmOrfnWmmVGZtQN65E964CE1fIgKZh4%3D&reserved=0>
>>
>> Abstract:
>> The future industrial development of biomass energy depends on the application of renewable energy
>> technology in an efficient manner. Of all the competing technologies under biomass, gasifiers are considered
>> to be one of most viable applications. The use of biomass fuel, especially biomass wastes, for distributed
>> power production can be economically viable in many parts of the world through gasification of biomass.
>> Since biomass, is a clean and renewable fuel, gasification gives the opportunity to convert biomass into clean
>> fuel gas or synthesis gas for industrial uses. The preparation of feedstock for a gasifier requires time, energy
>> and labour and this has been a setback for gasifier technology development. The present work is focused on
>> gasification of long-stick wood as a feed material for gasifiers. This application makes reduction not only in
>> the cost but also on the power consumption of feed material preparation. A 50 m3/h capacity gasifier was
>> fabricated in the cross draft mode. The cross draft mode makes it possible to produce low tar content in
>> producer gas. This cross draft mode operates with 180W of blower supply for air to produce 10 kW of
>> thermal output. The initial bed heights of the long-stick wood and charcoal are 58 cm and 48 cm respectively.
>> Results were obtained for various flow conditions with air flow rates ranging from 20 to 30 m3/h. For modelling,
>> the flaming pyrolysis time for long-stick wood in the gasifier is calculated to be 1.6 min. The length of the flaming
>> pyrolysis zone and char gasification zone is found to be 34 cm and 30 cm respectively. The rate of feed was
>> between 9 and 10 kg/h. Continuous operation for 5 h was used for three runs to study the performance. In this
>> study we measured the temperature and pressure in the different zones as a function of airflow. We measured the
>> gas flow and efficiency of the gasifier in order to determine its commercial potential for process and power
>> industries.
>>
>> Regards
>> Crispin
>>
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