Before I moved back to the farm I had a Tarum wood gasification boiler. From what I see reading about wood gas the Tarm and the masonry heaters work on a similar theory of operation to the wood gas system except that they burn the produced gasses with a secondary air supply. I understand that the tarm works by forcing air into the system simular to the startup fan on a wood gas system and that the tarm is based on full combustion. As I write this I feel they are less and less alike but bare with me for a second. The Tarm works by forcing air into the wood box for the primary air and then down drafting between a slot in the bottom of the fire box into a refractory chamber where secondary air is introduced that finished the combustion. Now wood gas systems here work in a similar way with primary air and secondary air in a down Draft system. The big difference being that these system use a restricted exaust to control the burn rate. And the tarm has no restriction on the exaust and forces air in for full combustion.
So here is my question the tarm wood boiler has a fire box with a slot in the bottom the top of the box has an air inlet and loading door on the front but is sealed during operation. This design allows for full length stove wood to be loaded not the chunks. If the wood is split on the small side it works great with no bridging issues. I keep thinking about that system and wonder if anyone has tried something like that for a wood gas system. All the videos and images I see are round containers that you load from the top. BUT a tarm stove loads like a conventional wood stove and once loaded has very complete combustion. The tar gasses will raise up to the top of the cool boiler collect on the inside then run down into the bottom making their way to the slot in the middle and the secondary air then burn clean.
If that firebox design could be modified to work with wood gas it would be a easy way to burn normal fire wood not chunks.
What application are you planning on using this for? I don’t see it running a ICEngine. Enlighten me
I am wondering why the tarm style wood box and down Draft isn’t used for a wood gas system to run a motor. I ran that wood boiler for several years and loved it. The wood gas is a totally new concept to me and as I keep looking at them I keep wondering why the tarm style combustion chamber couldn’t be used if you restricted the air outlet to limit combustion. I am guessing there is a very good reason why so I thought I would ask.
Tar. You see the tar being consumed in a secondary fire box. That secondary fire box in a internal combustion engine is the cylinder. To get there the tarry gas must pass by the valves coating them. When the motor cools down the valves stick in a position just waiting for a piston to come crashing into them the next crank over. Damaged/destroyed motor. Just my thoughts. But keep on thinking you may come up something that blows the lid off.
A while ago l had a similar idea, but in a nother direction. Use a wood gasifier to warm the house.
It goes like this. We can only retrive about a max of 70% of the woods energy in a conventional wood burning stove/boiler. 30% (usualy a lot more) are lost trugh the chimeny becouse you have to have a certain temprerature of gas in the chimeny to avoid tar buildup and insure good draft.
But! A pure wood gas burner produces no tar and much less draft is neaded, so this means exhaust gases culd be literaly left in the athmosphere at room temperature. This allso catches all the energy from steam in the gas, becouse water wuld have time to condensate out.
Really? I would have thought the opposite… Downdraft gasifiers create a lot of drag vs a regular stove. Engines are powerful blowers.
Well this is based on a blower to push air in (or pull the gas out) the gasifier, like a pellet stove. JO says his gasifier boiler works well without a fan, but his chimeny is still hot. In order to have cold eqhaust its preety hard to make it without a fan.
This is actually a tricky question to address.
It is true that with a natural drafting chimney it is hard to break past the mid-70’s % in heat use recovery. ONLY by outside energy forced draft inducing can you beat this. The forced draft blower GARN system will do 90+% heat recovery on long form wood. Outside sourced Power needed for their draft blower. Outside sourced Power needed for the water jacket circulation.
Natural draft needs no outside power. I use inside house Quadra-Fire stoves with insulated SS chimneys. Very quiet. Works without any outside power needed.
And that natural draft “waste” ain’t a waste. Air exchanges the whole house inside air, and interior dehumidifies wonderfully.
Even more outside power and complexity to do this with blowers, fans, and refrigerant/mechanical systems.
Wood sourced heating and you do not care if the combustion gases are high CO2. That is an actual best combustion goal. You want min 16% CO2. You want the lowest possible CO.
Woodgas for engines you want the lowest output energy-inert CO2, and the highest output produced energy potential CO (carbon monoxide) possible.
Whole different needs.
Only by a continuous forced flow through HOT wood charcoal bed can you achieve this CO2 to CO conversion.
Cordwood/stick wood form engine woodgasifiaction can, and has been done. Sucks big time. You need to use side “char breaking” ports. Iron rodding/braking/settling of the wood sticks burnt down to surface char to keep your char bed continuous, and reformed as it is consumed up.
And never as good as a pre-chunked wood fed system in turning the combustion made heat-energy hot-made non-active carbon dioxide, and H2O steam into energy- storing carbon monoxide, hydrogen, and wood-methane engine fuel gasses.
Just the way of it man.
J-I-C Steve Unruh
The boiler runs full blast at only 1/8" H2O of vacuum. My brick chimney stores most of the heat lost from the boiler’s exhaust (400 F). Radiates into the house for 24 hours.
My little air mattress blower usually pulls 4" H2O (32 times the chimney) of vacuum on the gasifier. Same as Rabbit’s 1500 rpm high idle.
JO, did you ever measure the temperature at the top of the chimeny?
Steve, l am not a particular fan of a fan either, and l have enough wood to not have to play around much with super efficiant boilers, my idea is just that, a idea. But perhaps it inspires someone.
It wuld be a fun experiment thugh…
No, but it’s only about the same as my breath. Maybe a bit warmer towards the end of a full 4-5 hour run.
Does condensation ever occur in your chimeny?
I see lots of mostly new houses with external ss chimenys drolling black liquor at the seems, indicateing inpropper gas temperature and boiler setting.
There are no better moisture capturing capabilities that I know of than in red bricks. You can pour a jug of water on top of a brick in your hand and not a drop will hit the ground.
I’m sure a lot of moisture will get sucked up by the chimney during startup but most will steam off when the chimney warms up. The rule of tumb is that temp should be above dew point one meter down the top of the chimney. Wood heating - no problem. Oil burning - soso. Electric or heat pump (not using the chimney) will shorten it’s life considerably (freeze cracking) + basement moisture problems.
Great replies. LIKE the gain the tarm will hit up in the 90s for efficiency. Mine would leave a gray black soot on the water heat exchanger and in the bottom of the boiler. The exaust comming out of the boiler was typically about 300 F if it got up to 500 f you really needed to take it apart and clean the heat exchanger with a wire brush always a dry powder in the exchanger. There was almost nothing in the chimney at the end of the year. I typically burned 4.5 cord of wood a year and cleaned the boiler every 2 cord of wood.
Te thing I found interesting about the tarm design is there is a lower refractory brick v shaped chamber where the re burn is done that chamber is crazy hot I forget the temperature of that chamber. I just wonder if that section would be hot enough to brake down the CO2. The Tarm depended on stored heat in that chamber to restart the boiler for up to 10 hours when there was a call for heat. I had a 700 gallon hot water tank and in the coldest part of the winter here I would fill the boiler 3 times a day and it would never actually need you to restart the fire. The only time it would go out was when I wanted to clean it. I got all my hot water as well as heated 1800 square feet of open concept salt box house with that boiler and only burned 4.5 cord a year. The house was 70 degrees all the time in New Hampshire where we have pretty cold winters.
Anyway just wanted to put it out there because that boiler was amazing I almost took it when I sold the house.
what part of the country are you in Dan? Does NH stand for New Hampshire?
Yes I am I North Conway New Hampshire