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Gasification quandry

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by rvtgr8, Jan 8, 2008.

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  1. jebatty

    jebatty Minister of Fire

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    The remarkable successes with the gassification boilers are numerous and adequate testimony to the tremendous advances in technology in this area.

    "You’ll have to give us some details of your flat plate hx for charging the tank, Jim." Mine may be a little unique, but I think the concepts should be transferable to other areas. My installation is inside my wood-working shop, including boiler and steel storage tank. All heat, except for that which goes up the stack, stays inside.

    Think of the hx as a single heating zone or heat load. The boiler simply has a short circular loop to the hx and return. This is pressurized, with expansion tank, air scooper and vent. I use the Tarm recommended Termovar load mixing valve, so really no hot water moves to the hx until the Termovar starts to open.

    On the return side, or outlet side, of the Termovar, I have a surface mounted line-voltage aquastat set at 150. Until this aquastat closes, water is moving by gravity feed from the boiler supply, through the Termovar, and return to boiler. No water is moving through the hx. As soon as temp hits 150, the aquastat closes and turns on the boiler circ pump and a second circ pump on the other side of the hx. Both pumps always operate at the same time.

    Hot water now moves through the boiler side of the hx and transfers heat to the output side of the hx. The output side of the hx is non-pressurized to the steel heat storage tank, with expansion space left in the top of the tank. Cold water from the bottom of the tank is received by the circ pump and pushed throught the hx, returning hot water to the top of the storage. I have no separate heat control or thermostat on the storage. It takes all the heat the boiler can deliver. If by chance storage heats to boiler output capacity, the boiler simply will reach 190, and cycle off and on based on boiler controls. Never-the-less, so long as return temp to the boiler is 150 or above, both circ pumps will continue to operate. I have never reached a situation yet where water drawn off the bottom of storage has been above 150. Due to stratification, water at the top of the tank often exceeds 150 though. I am getting all the heat I need with this level of heat storage.

    As mentioned in prior post, there is a diverter valve on the output of the hx to immediately divert hot water to a unit heater and then back to storage input. The unit heater does not strip all of the heat out of the water. The unit heater fan is operated on a thermostat to provide heat as needed.

    A unique aspect of my steel storage, since it is interior to my shop, is that the tank now operates as a large radiator, and once the water is heated I rarely need to use the unit heater. In fact, the heat radiation from the tank has been more than needed, and I have wrapped an insulation blanket around the top, bottom and 3 sides of the tank to limit radiation only from the front. No fan/electricity needed for normal heat.

    Sizing of the hx was not too engineered. I started with a 20 plate 3-1/2 x 8. It was adequate, but the boiler delivered far more heat than this hx could strip, so the boiler regularly cycled off and on. I now have a 30 plate 5 x 12, 1" inlets and outlets. This does have the capacity to take all the heat the boiler delivers, actually more, and I am very satisfied.

    My boiler circ pump is a used Taco 009 which I had on hand, and the output side to storage circ pump is a Taco 007. I am aware of the corrosion issue with this pump on the open non-pressurized storage side, but for the cost of this pump and steel tanks, what the heck.

    The only remedy for corrosion, and just to provide some protection for the hx, is a high temp water filter (50 micron) on the supply side from the tank to the hx. This filter needs to be changed every week to 10 days, and it is usually is full of a rusty slime which I suspect is coming from the steel tank (a used fuel oil tank).

    I am quite certain I will install a 1200-1600 gallon buried, insulated concrete septic tank next summer for storage. Should eliminate corrosion problems of any significance and provide heat for a week or longer for my shop with no boiler firing.

    Hope this helps.

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  2. Eric Johnson

    Eric Johnson Mod Emeritus

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    Robert,

    My point, and perhaps TC's, was that when you factor hot water storage into the equation, which most of us have, you have to decide between pressurized or nonpressurized storage. If you go with nonpressurized storage, which most of us have, then you need a heat exchanger anyway. So if you decide to go with nonpressurized storage, then it's a moot point and shouldn't be the determining factor in your choice of a boiler. Pressurized storage allows your whole system to remain pressurized, but then you need a pretty big expansion tank, which has about the same degree of extra complexity and expense as a discreet nonpressurized tank and heat exchanger. I don't know f that makes sense, but it's the best I can do first thing in the morning.

    Jim,

    The guys with Garns treat their water and are able to eliminate corrosion. The Garn is a nonpressurized, steel system like your tank. I'm told they test water quality with a piece of steel wool. You put the steel wool into the water and see if it rusts. If it does, you add more chemicals. I'm sure the Garn guys will correct me if I'm wrong. A cast iron Taco 007 costs about $30 on Ebay. I used one for 5 years pumping fresh domestic water between a hot water heater and a coil in my old boiler, and it was still working when I eventually tore it out of there. I bet the corrosion potential in an oxygen depleted environment like your tank is even less.

    I don't understand how you recover heat from your tank. Sounds like you're set up to efficiently store it, by circulating water from the bottom of the tank through the hx and depositing the heated water into the top. The best way to recover it would be to draw from the top, but that would involve some fancy piping and another pump, best as I can figure.

    FWIW, Here's a diagram of what I came up with before abandoning the idea. This involves two circulators (sans flow controls) aimed in opposite directions and pumping through each other, depending on the desired function (storage or recovery). I'm not even sure that it would work, but it's the result of a lot of thought. The big advantage you have with a steel tank over a concrete tank with a rubber liner, is that you can run a pipe directly out the bottom of the tank, which solves some tricky potential problems involving pump priming and cavitation.

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  3. jebatty

    jebatty Minister of Fire

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    Eric -- my system is a little unique in that the area heated also contains the steel storage tank and heat principally is provided by radiation from the tank. If I run the circ pump through storage (boiler off), water draw off bottom may be fairly low, but even drawing 100-110 water through unit heater produces significant heat. And as water draw continues, water temp increases until total storage depleted.

    Another unique factor I didn't mention because it would not involve many is that actually I have 3 - 275 gallon tanks plumbed in series. Hot water from hx into tank 1 at top, out from bottom into tank 2 at top, out at bottom into tank 3 at top, and out at bottom of tank 3 to hx (or to unit heater if boiler off). Use of 3 tanks in series likely results in limited effective reduction in stratification. But keep in mind drawing from storage, other than as radiation, was not my goal.

    Actually, radiation was a bonus not planned for. I struggled with the concept of heat recover but was very pleasantly surprised by the radiation effect, thus causing me to abandon further work on more effective heat recovery. Will keep your concept in mind. Not done tinkering, however, . . . .
  4. Eric Johnson

    Eric Johnson Mod Emeritus

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    Sounds like it works just fine to me. The main thing is to have enough capacity to handle the output of the boiler to keep idling to a minimum and heat the space you need to heat. Beyond that, it's just fun.

    I think most of us get a kick out of playing around with these things and making them work better (or different), but once you've got the fundamentals covered, that can be a lifelong, leisure-time activity, AKA--a hobby. The great thing about a resource like this website is that we can share our experiences (and in some cases, expertise), with other enthusiasts.
  5. TCaldwell

    TCaldwell Minister of Fire

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    robert, as eric stated for storage you will need a hx no matter what, I think alot of people would be very happy if pressureized storage was affordable, it would solve most of our problems. Being what it is few people look beyond the desire to be independant of the oil truck, this complicates and disappoints what should be a good experience. Some hearth members welcome this challenge for themselves and unselfishly for others, we all learn. I , in theory believe that if either system is hydronically correct , it becomes more of a preference judgement. For instance, nofossil has done his homework,and will keep on refining his system untill it is more efficient than most out there pressureized or not pressureized . My preference is the nonpressureized garn , extreemly simple alot of storage and a higher burn rate for rapid storage all in ONE PROVEN UNIT! If your direction is pressureized ,calculate your heat storage requirements , investigate tanks, heat exchangers, and piping then go for the boiler you prefer that is sized to your requirements. Enough about that call me if you want to talk garn. tom
  6. rvtgr8

    rvtgr8 New Member

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    TC,
    So how do you find out more about the Garn? Its initial appeal was the fact that it had tons of storage built into the furnace unit. I just did calculations on a Tarm with 880 gallons of water and it was going to require a minimum of a 14' x 14' boiler room. The Garn is huge, but does not take any more room than that set up. One frustration that I have encountered in this process is getting much in the way detailed information from Garn. Clearances. dimensions and most importantly price. While I am certain that it is a good product (I don't see threads on the down sides of 'em) I have only seen one reference to price. If it is truly a $12K unit, It might not be within my budget. We are retired public school teachers. I think it would have to be distinctively better quality in order to justify the extra $5K. As I have said though, I don't know where to get the real facts. If you are a dealer or know one who can sell me on this, I am open for a convincing pitch. I am sold on the gasification. I am in awe of all of the knowledge that is present within this forum. I will do all of the math and when I arrive at the decision, I will buy an adequately sized unit. But this forum is much like visiting with aficionados at a cat skinning festival, everybody has a different approach. I hope I am not offending you or anyone else in the forum when I say, You guys are damned serious about this topic. I appreciate people who are passionate about their personal interests. I pride myself in my ability to teach, but I live only so long as I continue to learn. Thank all of you who are helping me to do just that.

    Robert
  7. Eric Johnson

    Eric Johnson Mod Emeritus

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    Well here's the deal, Robert: Most people pay a contractor to install a furnace or boiler in their basement, and then they set the thermostat at the beginning of the heating season, pay the monthly fuel bills and forget about it. People who are happy doing that are probably not the best candidates for central wood heat.

    Most of us, on the other hand, found ourselves researching our options, designing our system, installing it ourselves, and then had to learn how to operate it. We're filling it with fuel once or twice a day, monitoring its performance (with varying degrees of obsession), and always trying to make it work better (ibid). And when we're not doing that, we're finding, processing and handling fuel to run it. That and spending our spare time hanging around the Boiler Room talking about it.

    So you've been warned--it gets into your blood.
  8. bjleau

    bjleau New Member

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    rvtgr8

    I'm new to this as well and lurking and learning form all the wood fuel yodas out here. I just got some info on the Garn and still have not seen one but it is looking like about 10K for the 1500 gallon and 12K for the 2000 gallon + pipe + hook up parts. Now having done some of the math cost of EKO Tarm etc.. + storage and taking into consideration where to put it (Taking space in the pole barn v/s workshop in our house) I'm leaning tward a Garn as well.

    At the risk of highjacking your thread....(hear me out, I'm thinking this might be useful for all newbies)
    Can one of the Garn owners describe how you start your fire and the time involved in doing that. How often do you need to feed it. I'm a little worried that my wife and kids will not be able to add fuel to the EKO, Tarm etc... Especailly after reading one of the post in this thread about smoke, flames and burning eyebrows...I want to heat the house not cook the kids.

    Could you also describe the quantity, quality and moisture content of your wood. Can you burn downed and kind of rotten but dry wood?

    Thanks in advance for all the advice "all knowledge begins with experience" Kant

    Brian

    "all knowledge begins with experience" Kant
  9. Nofossil

    Nofossil Moderator Emeritus

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    I have an EKO 25. Loading is simple and the wife / kids / cat can do it. The trick is to wait until the flue temp has dropped, indicating that the fire has started to die down a bit. You don't want to load it when it's cranking at full output. Mine is in the basement and is quite civilized.

    You need dry wood to start it, but startup is under 10 minutes (5 with practice) and it can burn pretty much anything once it's going. You want to avoid a load that's too much of any one thing - too much green wood or too much really small wood are both bad.
  10. Eric Johnson

    Eric Johnson Mod Emeritus

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    Welcome to the Boiler Room, Brian.

    We have some guys who are pretty Garn good about sharing their passion for their favorite boiler.

    For the record, the smoke is not a big deal with the EKO, which is the only brand I can comment on, since it's the only one I've operated. Like everything else with wood heat, experience is the key. And since you have the Boiler Room at your disposal, the learning curve just got a lot smaller. I have had a face full of smoke, but never come close to singing any body parts. I'd say they're very safe to operate--safer than a conventional wood-fired boiler, if for no other reason than there's no creosote and the chimney temps are much lower than any wood stove.

    I have to disagree with nofossil on the cats, though. When I send my wife's cats out to the barn to load up the boiler (usually when it's below zero), they come back all singed up. I think that's because they seem to be naturally curious, and they try to play with the dancing flames. I keep telling them they're going to get killed if they screw around like that, but they never listen to me.
  11. verne

    verne Member

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    sorry for invadeing this post , but I have a question and i dont think its worth another topic.
    What do you guys think of burning pallet wood? The wood is 80% hardwood on average and it is definitly dry because the company has dryers.The pallet wood is all in pieces. stringers and top and bottom pieces. Problem the nails?? the nails are either sheared or cut so the top bottoms have three rows three nails each , so I quess you could cut them out . But the heavy stringers have nails all the way. My friend burns only this in his wood furnace and says the pile of nails actually holds heat .what do think about it in an eko .I will be installing mine in the spring.A free tractor load is about 8 cord. Thanks
  12. Nofossil

    Nofossil Moderator Emeritus

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    I think this should be another topic - lots of territory to be explored.

    My $,02:

    If you burn only pallets, you would need to adjust your primary and secondary air inlets. Pallet wood has LOTS of surface area compared to normal firewood. It will generate enormous amounts of 'producer gas' - the flammable gases that make secondary combustion possible. It's likely that it will generate so much that you won't have enough secondary air to mix with it. You will also get frighteningly high secondary combustion temperatures, because there's no water vapor to moderate the combustion.

    It will burn very well, but it's quite different from the nominal wood mix that the boiler was likely calibrated for. I don't know enough yet to tell you how to make the necessary adjustments.

    I'd suggest mixing it with some larger and greener pieces of normal firewood.
  13. Eric Johnson

    Eric Johnson Mod Emeritus

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    That's a god question. Like nofossil said, wood that's too dry or too small can cause problems, because these boilers were designed to burn typical dry hardwood. But I think if you mixed dried pallet wood in with some green or semi-green chunk firewood (or similar) you could find a mix that would work well. As to the nails, I don't see a problem, other than having to clean out the ash pit more often. Maybe somebody else has other ideas, but I can't see what it would hurt. Over time the scrap value would start to add up if you sifted them out of the ashes.
  14. chrisfallis

    chrisfallis Member

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    I owned a Tarm for 4 years and saw a Garn operated only once, but I will give you my impressions. The Tarm was pretty easy to start. Throw in some paper, cardboard and knindling, light, shut the door, start the draft fan and come back in a few minutes to check. I would then thrown in some scrap lumber and give it a few minutes to make sure the secondary combustion was going (gotta love that view port). Finally I would pack the firebox and go on about my business. This sounds like a 5 to 10 minute process, and while time consuming, it was theraputic "alone" time for me. I could bring in another trash barrel of wood from outside, tidy up the basement, putter, watch the boiler temps rise, etc. If I was a smoker, this would have been the perfect time to light one up. I am sure some of the other readers know about this mostly male phenomenon, where you stand around machinery, watching it and thinking, "boy, this is cool". I fed the Tarm kiln dry scrap wood and seasoned split pine. The few times I tossed in "greenish" branches, I could see the water boiling out the ends with no secondary combustion going on. Learn from your mistakes!
    I started the fire about once a day, depending on weather. I never perceived that this was a burden.

    The Garn that I saw in Santa Fe, New Mexico was super easy to start. A ball of newspaper, some sticks, apply match, close door and start fan. Come back in 5 miutes and add wood to coals. Add more wood in 15 to 20 minutes, set and forget. Fuels being used in Santa Fe were pretty dry since the town is in a very arid location. They burned pine, scrub oak and wood-shaving briquettes to see what worked the best. The owner said there was a learning curve to get the most heat from this boiler, but it was being fed by students and security guards at the college where it is installed. In orther words, a monkey could do it. After the fire was established and the loading door was opened, there was so much radiant heat that you had to step back. The scceonday combustion takes place in the ceramaic refractory in the the far back end of the firebox, but between the glowing bed of coals in the front and the white hot gasses in the back of the firebox, it ws pretty darn intense. Youngsters and wives and more timid souls might be tempted to stand 5 feet away and launch wood into the unit. Those of us tough guys would gently palce the wood inside so as not to damage the ceramic refractory.

    My natural gas bill is about $2500 a year for heat. That is with the thermostat at 64 degrees. When we looked at a new heating system last year the suggestion that we got was for a new boiler for the radiators and 3 hot air furnaces to replace the 1940s vintage octopus. With ductwork modifications and asbestos removal, we were quoted $25K. I think that I could spend $12K for a Garn, $3-5K for piping and heat exchangers, and still be ahead of the game. A six year payback is pretty darn good with me. I am assuming the fuel is free and my fire tending time is worth zero. The wood is basically free for the scrounging, and since I am outside walking the dog anyway, a few trips to the backyard garage each mornig would not be a burden.
  15. verne

    verne Member

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    Thanks no fo and Eric. I dont think I would burn just pallets any way but the nails were a concern .I just shoveled up a large pile left from newyears.Thanks again and I will continue to read and learn
  16. chrisfallis

    chrisfallis Member

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    I burned pallet wood in my Tarm. It was the best source of oak out here in pine country and free from a company that rebuiilt pallets. I used a radial arm saw to cut everthing to stove length and had to watch that I didn't try to saw through nails. The nails and nail fragments just ended up in the lower combustion chamber like big clinkers. I picked them out periodically and recycled them. The oak 2x4s I saved for overnight burns. The pine 1x4s did burn to fast if used alone.
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