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 Gasifier design considerations....

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T2H
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PostSubject: Re: Gasifier design considerations....    Sun Aug 02, 2015 11:44 pm

Thanks tritowns, this helps a great deal.
Yes I as well suffer dearly for diving in and building on the fly, I do start with rough drafts and improvise along the way.

Then in hindsight realize if I had just put in the sweat on the computer in my design I could have saved myself unnecessary work and, cutting off parts and re-doing work again.

So what are your thoughts on the cross section of the 1/8th pipe?

Meaning why the slot with the hole, is this for directional dispersion?

Thanks so much for the thoughts on gas flow in consideration with condensation generation and how to deal with it in a positive manner.

So I am surmising if you are having your gasses rise out of the top of the system you are pre-heating the main hopper feed section?

Or are you pre-heating the main air source for the furnace area?
I am really enjoying the article from 1945, so cool to see they had their own forum in a sense.
Its a bit like time traveling:>)

A radical solution to the problem has however been found in the monorator, which to great extent has pure coincidence to thank for its birth. During experiments with gasifier trailers at the beginning of the present world war, the also in Sweden well known racing driver S P J Keinänen found, that to gain free sighting out the rear he had to make the gasifier's fuel container low, but in order to still have room for enough fuel he had to increase its width quite a lot. These primary conditions combined with the inventor's at the time incomplete knowledge of earlier existing gasifier designs, lead to a fuel container designed in a way which in several ways differed from the by Imbert created orthodox type, and so the monorator container was born (figure 4).

Loved what he said about the inventors lack of knowledge, in other words he was not constrained to the current standard box all the inventors had created and found themselves in. Good stuff!
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PostSubject: Re: Gasifier design considerations....    Mon Aug 03, 2015 12:09 am

So funny!:>) The proverbial box.......... (When we first heard about the monorator, the collective assumption was that it was a matter of pure humbug, as it was considered unthinkable to use wood in a vehicle wood gasifier, that was dripping wet and taken directly from growing trees.)

Got a good laugh on the following.

Thus we could, during the driving tests, stop the car, open the hatch on the gasifier and toss in a huge ball of snow of 6--8 kg weight, whereupon the driving was resumed without any complications whatsoever. After a while the maneuver was repeated and a curious gasping audience came to the astounding, though somewhat incorrect conclusion that the gasifier worked on nothing but ice and snow, and the operation of it therefore was unusually cheap.
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tritowns



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PostSubject: Re: Gasifier design considerations....    Mon Aug 03, 2015 12:35 am

I pre heat air with post reduction gasses. I keep the sides of my hopper area as cool as possible to help condense liquids out.

All system heats come from the reactor doing its job well... as it should, because it was designed to keep heat where it's needed.

The new system I'm working on uses very small fuel sizing. Hopefully sawdust if all works out. If I just have a hole, a piece of fuel may be able to get close and block off airflow there by making that nozzles coverage area cold. Cold means tar. The slot will tend to stop ghat from happening. Remember we are dealing with drawing air into the system solely with vacuum from the engine we are trying to run. And that vacuum at the nozzles is after all the pressure drops caused by filtering, cooling, and all the piping.

A 1/8th pipe has an id of around .30, the 1/8th hole in that slotted pipe is .125 id... csa will be very different. In a gasifier using strait 1/8th pipe nozzles you may only need 4 of them where with the latter you would need more than 12 to have the same csa of combined nozzles. Hope that makes sense.
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tritowns



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PostSubject: Re: Gasifier design considerations....    Mon Aug 03, 2015 12:43 am

I draw everything out by hand. I have over 65  1/4, 1/2, full scale drawings in my desk... and those are the ones that I kept because they have meaning to me.

I tend to draw just sections out now though as I need them.... I will do a small sketch and put in important measurement so i don't forget them then just use the scale section drawings as needed.

I've built a few gasifiers now though...
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PostSubject: Re: Gasifier design considerations....    Mon Aug 03, 2015 9:13 am

I thought about your new jet idea for the sawdust gasifier and the possibility of them clogging up.

Will you be pointing them in a downwards position?
Due to the gravitational flow as the sawdust is consumed this should keep them from clogging up.

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PostSubject: Re: Gasifier design considerations....    Mon Aug 03, 2015 9:55 am

Some will be, yes
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PostSubject: Re: Gasifier design considerations....    Tue Aug 04, 2015 1:40 pm

What about instead of slotting them, cut yourself a short piece, drill and tap it and thread your main jets into that piece and you will have two open ends in a sense like what you have with the slotted versions.

Something like an upside down T
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tritowns



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PostSubject: Re: Gasifier design considerations....    Wed Aug 05, 2015 12:05 am

You mean with too nozzles at the ends of the T as it were? Not totally following but there's nothing new there.... :)

The Idea with the nozzles is to get penetration into the feed stock... the slot will allow air to go around a piece that is blocking the main hole and burn it away so it can again penetrate as deeply into the feedstock as the draw on the system will allow. Hope that makes sense.

saying that, there is always more than one way to skin a cat... do like I do, and try it in a system... run it for awhile then let it go cold and clean it out inch by inch to see what the nozzle pattern is. if all is proper you should have a good layer of char well above the nozzles and going all the way to your restriction... at least, that's what i'm looking for. if all is well, I continue down looking for signs of too much o2 in the system, ash, and clinker...
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PostSubject: Re: Gasifier design considerations....    Wed Aug 05, 2015 5:06 am

Got it, thanks for the explanation.
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tritowns



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PostSubject: Re: Gasifier design considerations....    Wed Sep 09, 2015 1:00 am



to cone or not to cone...

You will never see a cone in one of my systems... the above pic is from a fellow that made a similar to a gek system. after about 20 hrs total burn time this is what he found





His system does seem to make gas, but having the hour glass in contact with glowing char spells  disaster for the cone itself... eventually it will fix itself by just burning away any steel that is in the way but that isn't a fix in the overall scheme of things. I suggest this...


please excuse the sloppy free hand drawing.

by removing the top portion of the cone the char will find it's own natural char slope. He was concerned with gas possibly bypassing the nozzles so I included a tar fence that would just drop in. not how I would do things but it would work well enough for him to put on some real testing hours of run time.

my friend is a gasification hobbies t so he flares more than runs engines I think. Myself, I don't do changes to a system until I've ran an engine about 50 hrs. you just can't see if a change has been beneficial or not until the unit has had a chance to burn in some.

again, my 2 cents.. for what they're worth.
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tritowns



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PostSubject: Re: Gasifier design considerations....    Thu Sep 17, 2015 10:34 am

Get the gas out.

One of the most over looked parts of the gasifier is the grate.

While I can't show you what I do with ours as it's proprietary to our system I feel an over view of the grate's function is in order.

Most people look at the grate and figure it just keeps stuff from flowing out the bottom of the gasifier. So how complicated does it need to be.

Most of my systems development has been in the grate area. Yes it is that important.

Can a flat piece of steel or some bars welded together be used as a grate? Of course they can, but it does effect the the gasifiers thermal efficiency. If you look at APL 's new GEK you can see they almost did a total redesign because they changed their grate system… things that make me go hmmmmm…

A well designed grate keeps the char in place so it can add to the reactions processes until there isn't any more carbon to be used. I don't like the idea of slipping char. All I want is dust coming out of my system.

The grate needs to allow ash to pass while doing the above. Ash held in place in high heat leads to clinker which is something you want to avoid as it can plug up the system.

So how can you do the first and the second when they seem to be contrary to each other?

I designed our grate so that it's overall cross sectional area is equal to the restrictions CSA. And yes it can be fine tuned should I change other internal parts. This keeps the gas velocity up so as to pull micro ash out as it forms. The velocity keep the reduction heat high. This should promote greater reduction efficiency. Because of this gas pass through velocity I don't need a grate shaker.

Our grate design is self insulating so it shouldn't be effected by high heat even though it is made of mild steel.

The self insulating grate keeps heat in the reduction area at times of lower gasifier draw. This means less chance of tar downstream.
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PostSubject: Re: Gasifier design considerations....    Thu Sep 17, 2015 11:53 am

Good info tritowns, you are such a tease.
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PostSubject: Re: Gasifier design considerations....    Thu Sep 17, 2015 9:32 pm

Just trying to get people thinking Very Happy
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PostSubject: Re: Gasifier design considerations....    Sun Sep 20, 2015 1:28 am

LOl, I do appreciate it man.
No doubt if you were not tied to the propriety chain you would share your secrets.
I understand, but man you don't have to keep reminding us that.
Its like I have ice cream and you don't na na na na na.:>)
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PostSubject: Re: Gasifier design considerations....    Sun Sep 20, 2015 8:35 am


I designed our grate so that it's overall cross sectional area is equal to the restrictions CSA. And yes it can be fine tuned should I change other internal parts. This keeps the gas velocity up so as to pull micro ash out as it forms. The velocity keep the reduction heat high. This should promote greater reduction efficiency. Because of this gas pass through velocity I don't need a grate shaker.

THIS IS A BIGGER HINT THAN I GIVE MOST PEOPLE.... gas velocity if kept up through and past the grate will pull fly ash with it.
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PostSubject: Re: Gasifier design considerations....    Sun Sep 20, 2015 9:23 am

sort of using the vortex to pull enough air through but in doing so pulls the ashes through with the air before it cyclons the ashes out of the system leaving you with just gas alone
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PostSubject: Re: Gasifier design considerations....    Sun Sep 20, 2015 10:40 am

I'm sure it could be done that way...
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PostSubject: Re: Gasifier design considerations....    Sun Sep 20, 2015 10:41 am

Most people allow the gas to slow down in the reduction area, to me that is a mistake.fly ash as it forms is considerably lighter than the char it's forming on, so gas velocity can pul, it out of the system as long as it doesn't slow down. Also this is where you only want as big of a reduction zone as what's needed to get the job done...
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PostSubject: Re: Gasifier design considerations....    Sun Sep 20, 2015 11:22 pm

tritowns wrote:

I designed our grate so that it's overall cross sectional area is equal to the restrictions CSA. And yes it can be fine tuned should I change other internal parts. This keeps the gas velocity up so as to pull micro ash out as it forms. The velocity keep the reduction heat high. This should promote greater reduction efficiency. Because of this gas pass through velocity I don't need a grate shaker.
 
THIS IS A BIGGER HINT THAN I GIVE MOST PEOPLE.... gas velocity if kept up through and past the grate will pull fly ash with it.
This pretty much is somewhat how a rocket stove works.
In principle, velocities ie gas flow.
Thanks for the coaching tritowns.
I figure if you cannot disclose we will keep trying with the pry bar. lol
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PostSubject: Re: Gasifier design considerations....    Sat Sep 26, 2015 9:37 am

Yup.

I figure if I do my job right then those reading this will be steeredin the right direction.

Always more than one way to skin a cat, but it's nice not to have to repeat mistakes that can cost valuable resources and time.

Always learning... especially from systems I don't fully myself even though they came from out of my head.
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PostSubject: Re: Gasifier design considerations....    Sun Oct 18, 2015 12:47 pm

Tritowns have you seen this solution he came up with for eliminating bridging?

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PostSubject: Re: Gasifier design considerations....    Mon Oct 19, 2015 1:33 am

Side draft (cross draft) isn't a new idea. I suspect he'll find a whole  new list of issues as he developed his idea. I wish him luck though.

I don't have any issues with bridging in my compact systems and I do run some pretty small feedstock through it. I don't use hopper or grate shackers.

I think there are simpler ways to build. I feel nozzle orientation and grate csa play more of a roll in stopping bridging. I also keep the feedstock off the outer hopper wall......
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PostSubject: Re: Gasifier design considerations....    Fri Jan 29, 2016 1:52 am

Hi there

If you just want something that works, I have put all my stoves to date online as free downloads.

all three are down draft, gasification type stoves, they are only small and intended to be used in the home.

cheers for now

ps here is the link to my sites page.

http://ecape1820.tripod.com/id63.html
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http://ecape1820.tripod.com
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PostSubject: Re: Gasifier design considerations....    Fri Jan 29, 2016 10:24 pm

thanks for the heads up bigflyin
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PostSubject: Re: Gasifier design considerations....    Tue Oct 11, 2016 1:06 pm

Very cool stoves.... but these are gasifiers to make engine grade gas. Heat I can pull off from parts of my systems for other things.
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