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Post by Rinchen on Nov 16, 2012 1:09:38 GMT -8
Hi, I still think its not safe.
Even on my standard rocket J-tube I have experienced blowback once due to a strong gust of wind and that resulted in a 4 foot flame shooting back out of the feed tube! Now image the catostrofic results of having something go wrong with a box filled with pyrolysis gasses...
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Post by Donkey on Nov 16, 2012 11:48:01 GMT -8
Hey,
This is really the first time that I've had a complete look at your gizmo. Interesting idea but there are some things things that give me pause.
The dangers of wood-gas are definitely there though they are not insurmountable. People have been using wood gas safely and to good effect for some time now. The creosote problem can only really only happen if the gasses are allowed to cool to their condensation point before you use them. If I got your design right, it seems to me that you plan to pass those gasses directly to the strove. There may not be an issue, though adding a fusible plug or some such safety feature is a good idea. Better safe than sorry.
Something else that comes up for me is the fact that to are using heat form the burn tunnel to gassify wood. The efficiency of rocket stoves comes (in large part) from insulating the fire COMPLETELY during the burn phase. As a general rule, you shouldn't take ANY heat from the system until it gets DOWNSTREAM of the heat riser. You want to burn the fuel completely before you use the heat or you will drastically reduce the efficiency of the system which can lead to creosote buildup, likely in the mass where it's hard to get at, clean, etc.
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Post by Donkey on Nov 16, 2012 11:49:43 GMT -8
Hi, I still think its not safe. Even on my standard rocket J-tube I have experienced blowback once due to a strong gust of wind and that resulted in a 4 foot flame shooting back out of the feed tube! Now image the catostrofic results of having something go wrong with a box filled with pyrolysis gasses... YIKES! Yep, I've seen that too.. Let me re-iterate.. YIKES! |
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Post by phillipjacks on Nov 16, 2012 12:45:10 GMT -8
If I got your design right, it seems to me that you plan to pass those gasses directly to the strove. There may not be an issue, though adding a fusible plug or some such safety feature is a good idea. Better safe than sorry. exactly. in a few of the videos i show how we do this. there is a hole in the wall between the feed tube and the gassify box. that runs into a channel inside the feed tube, and then out the bottom of that channel at the transition from feed tube to burn tunnel. to top of that channel is the coolest part, and its coldest is about 250F. its much hotter when the gas is passing through. cant remember temps at the moment. after i get offline, i'm gunna carry our mig welder down there and weld up the latching mechanism for the gassifer lid. when i get that done, i'll put a small log in the gassifier for test, and come back with some video results. i worry about the creosote build up durring the heat up and cool down phases. when the gassifer is first loaded, it takes a few hours to evaporate all the water out of the wood. giving off temps of 200-250F usually (sometimes hotter). at that moment i worry about small amounts of wood gas building up into creosote inside the channel or holes. also when the wood in the feed tube is exhausted, i predict that there will no longer be enough heat generated to continue gasification. but there will be gas buildup inside the gassifier box. during this cooling phase i worry about the same. i figure we will keep a good eye on those holes and clean them out daily/bi-daily. but still want the fusible plug for redundancy/safety. Something else that comes up for me is the fact that to are using heat form the burn tunnel to gassify wood. The efficiency of rocket stoves comes (in large part) from insulating the fire COMPLETELY during the burn phase. As a general rule, you shouldn't take ANY heat from the system until it gets DOWNSTREAM of the heat riser. You want to burn the fuel completely before you use the heat or you will drastically reduce the efficiency of the system which can lead to creosote buildup, likely in the mass where it's hard to get at, clean, etc. i know. so far with our tests, we are getting pure clean burn even without our tunnel insulated (wood box empty, just wood in feed tube). for the few minutes we had our wood gasifer working before we stopped it, our fire and rocket action/draw was INSANE and very clean. at first start (morning) we burn a little dirty for about 10-30 minutes, but nothing that bad (remember we are burning GREEN, wet wood still). with wood box loaded (we've only loaded logs so far, but plan on filling it with wood chips once we get it all worked out), we theorize the woodchips themselves will act as an insulator a bit. think of it as a consumable insulator. and as they convert into ash that will act as an insulator till cleaned out. its quite a large box (22" long, 18" tall, 25" wide) saddled around out burn tunnel. also out electric primer is increasing our draw quite a bit which is helping to give us clean burn even with high wind, wet green wood, and a not yet dry thermal mass. i cant wait to see how this thing operates with it all dry and dry aged wood (we have almost none this year). |
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Post by phillipjacks on Nov 16, 2012 12:53:01 GMT -8
Hi, I still think its not safe. Even on my standard rocket J-tube I have experienced blowback once due to a strong gust of wind and that resulted in a 4 foot flame shooting back out of the feed tube! have you added in a "tee" pipe at the end of your exhaust pipe? that will prevent wind gusts from giving you blow back. also adding in an electric fan at the end of exhaust like we did will do the same. Now image the catostrofic results of having something go wrong with a box filled with pyrolysis gasses... we are indeed aware and worried. we will put in as many safety measures with redundancy as we can. test test test test only when we are around to watch it. and if it ends up not being to our satisfaction, we will probably fill in the wood box with clay/perlite mix & cob and call the experiment a wash  over the years, i've always been frustrated with web boards because so many people post a build or log of a project, but few come back with results/failures/lessons/etc... 2, 4, 6, 12 months down the line. i plan on keeping this thread updated over time till theres nothing left to learn/share of this build so that people can see where we failed or succeeded (like our severe cracking of our structural cob (2.5 part sand, 1 part clay) on the front of our stove, shoulda just used thermal cob (1.5 part sand, 2 part clay, 3 part straw), or a higher sand ratio. who knows all our recipies might be crap, this build will teach us that. we are working with PURE clay (a free resource for us)) |
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Post by Dan (Upstate NY, USA) on Nov 16, 2012 13:16:44 GMT -8
I am glad to see this tech being used in a more urban/suburban environment instead of just the low population density areas.
I have found that my extra tall heat riser (like yours) will keep most of your ash on the burn tunnel side.
I think that as your cob dries out and your start using more seasoned wood you will want to extend the length of your heat sink to absorb all the heat you'll end up making with that monster.
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Post by phillipjacks on Nov 16, 2012 20:01:16 GMT -8
I am glad to see this tech being used in a more urban/suburban environment instead of just the low population density areas. yes, i'm excited to build an eco-village in a city. as we convert these old homes to eco-village style (a process we call green-fitting), we are learning to modify permaculture technology to fit existing structures. We also build quite a buzz in the city (Flint, Michigan). Thats one of the best parts. We get to reach many more people and teach them whats really up in the sustainability geek world. Its all illeagle in an urban environment (codes). Even urban gardening. But we have a super progressive government. i tell them what i'm gunna do, they think its awesome, then i tell them its illegal, they respond with a very surprised "what!?", and let me know its ok to do anyway, they just kinda turn their heads like they didn't know it was wrong. also because of this, they are using groups like ours to re-shape the cities masterplan to help include communes, eco-vllages, and permaculture/sustainable technologies. We are literally the cities poster peoples for their masterplan ( steeringflintforward.com/ scroll down a little and see us in front of a south facing room we converted into a greenhouse with recycled windows. technically illegal, endorsed by our city) I have found that my extra tall heat riser (like yours) will keep most of your ash on the burn tunnel side. Keen insight wish we coulda made it taller. In our next home install, I'm sooooo tempted to get the jackhammer out and dig out the floor a few feet to get that extra height. plus we could just lay out our exhaust pipes and bury them back in (minus an insulation layer and air gap layer to prevent our heat from going where we don't want it to. I think that as your cob dries out and your start using more seasoned wood you will want to extend the length of your heat sink to absorb all the heat you'll end up making with that monster. i was just gunna shoot a video about that topic before i left that house and came to use the internet. but my phone/camera was almost dead. a few more feet could be useful. right before i left, i had the top of the barrel up to 580F (impressive considering we have a 4" top gap). where our exhaust exists the house was 90F. Meaning we captured 490F worth of energy into the house. We built ours for radiant heat. So most of that was radiated into the basement. I'll cover our heat delivery system in the future when i get it finished. I'm not 100% sure on which idea i'm going to end up using. Have a few well planned out. We have zero bucks so its limited to found/owned resources. The home we are installing in has a 7.5' ceiling in the basement with 616sq' of floor space. the rest of the house has 10' ceilings with 1364sq' of floor space (two floors). This means we need to capture and extract enough heat to keep 18260cu' of air space warm. I know the typical ideology with rocket heaters is to not worry about air and keep a bench warm. but we have lifetimes of work to complete and cant spend a whole winter sitting on a bench in our basement. If we can't deliver our heat effectively, then we will supplement rooms with small small pocket rockets to quickly heat up air space of rooms we are kickin it in. Next year we plan on building veg oil furnaces in the homes too. So with the rocket heaters and veg oil furnaces we should stay warm, in a clean and free way |
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Post by phillipjacks on Nov 16, 2012 21:38:11 GMT -8
todays videos: www.facebook.com/v/422495564470345 - Showing our first try at a latching system for our gassifier lid. www.facebook.com/v/422498587803376 - Showing some temperature readings on our rocket stove. Remember, we are still drying and still burning green wet wood. So this isn't even peak efficiency. I also go over some areas that temps could occur that would allow creosote build up and possibly turn our gassifier into a bomb www.facebook.com/v/422500787803156 - Playing with principles of horizontal air feed combined with a vertical fuel (wood) feed. Even in this primitive experiment we can get amazing rocket action as well as start to see how we could expand the fuel feed into a larger "magazine" to hold even more wood. www.facebook.com/v/422502264469675 - end of 1st experiment with gassifer latching lid. result: fail, need to do more grinding, get washers, for better seal |
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Post by phillipjacks on Nov 16, 2012 21:39:37 GMT -8
in one of those videos above i say i don't know the temp creosote forms. i googled it. 250F (but varies based on factors like type of wood, temp, pressure, water content, etc...)
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Post by grizbach on Nov 17, 2012 8:24:19 GMT -8
Phillip, I fully agree with rinchen.
Gasifiers are far too dangerous for enclosed living space. A small amount of CO in the bloodstream and it's endless sleep.
Now, outside is another story!
I have two gasifiers, and any unburned CO dissipates quickly.
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Post by Rinchen on Nov 19, 2012 4:18:36 GMT -8
YIKES! Yep, I've seen that too.. Let me re-iterate.. YIKES! Indeed! ..... and .... indeed :-) Lukily I was just able to step back on time. I haven't had such events anymore, also because I have a better chimney now, but still there is always "Murphy's law" lurking around the corner ... I saw a documentary once made by Michael Palin where he travels trough the Himalaya. He meets a group of miners in India and every day they start their work with a song about safety. "Safety first, safety first" it comes down to. Safety is more important than production levels to them. Life is precious ... |
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Post by Donkey on Nov 19, 2012 8:37:32 GMT -8
I've seen that. Happened in a sauna rocket.. Sudden 3 foot jet out the wrong way. Very exciting..
One time, I accidentally made a wood-gas backfire in my cooker.. I used straw to light the thing. Stuffed the opening full (too full) lit it and blew on it to get it going. I was tired and wasn't paying attention, I kept blowing on the smoldering straw, not really realizing that I was filling the chamber above with flammables. The straw finally burned through the blockage as I leaned in for another blow, I saw the tiny little hole (in the straw) suddenly widen, it "breathed in" a big breath and WHOOSH!! It breathed a jet of flame right back out the feed hole. I didn't quite get out of the way in time and got my eyebrows, lashes, beard and hair trimmed up a touch.
Very impressive and a bit scary.
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morticcio
Full Member
"The problem with internet quotes is that you can't always depend on their accuracy" - Aristotle
Posts: 371
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Post by morticcio on Nov 19, 2012 11:25:34 GMT -8
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Post by Donkey on Nov 20, 2012 11:09:21 GMT -8
Close enough. |
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Post by phillipjacks on Nov 20, 2012 21:23:21 GMT -8
sorry i haven't posted videos or updates in a few days. been busy as heck. heres a few quick things. a) after playing around with my cap on my front clean out and doing vertical feed w/ horizontal air intake, i've learned that my stove draws way way way way better that way, so i'm building a vertical feed hopper extension that i can load up and put on a removable cap. b) tried the gasiffier with 10 logs. it was too much gas/too little latching force. i need to get some modifications made to my latch and try again. however 1 or 2 decent size logs work nicely. when gasifing, my heat output is averaging 80-120F hotter on the top center of my barrel c) i built a mock up of a heat collection plenum (out of some scrap drywall for now). don't have enough sheet metal laying around and no money to buy some from the scrap yard at the moment. i also only have one duct fan and no money to buy more. but at the moment its delivering 100+ degree heat to my girlfriends bedroom. which is about 13'x15' with a 10 foot ceiling and 3x 2'x4' old windows from 1915. the bedrooms staying nice and toasty d) filled the gassifier with a temporary "insulation" (used peagravel that had a little sand in it left over from filtering our builders sand) as a test to see if the heat output is better with the gassifier full of insulation or being used as a gassifier. e) seems most the group/volunteers have lost interest in the backbreaking labor of mixing up cob, so the little work thats been done on that is just screening more and more clay & sand to get ready for finishing the bench i'll have more videos and reports soon |
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