Refractory Mass Natural Draft - refire rates

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ISeeDeadBTUs

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A thread from a WG user got me to thinking . . .

One of the claims I think of the GW and presumably other RMND units, were that the fuel would reignite from the heat held in the refractory. The pyrotechnics of that could be debated for hours. BUT . . . I do not think I have EVER had the fire go out because of long off-cycling. As long as I don't use SFW (crap 4 wood) I have never had the fire go out with wood in the CC.

If I over-remove ashes, or I put uglies in (root balls), then sometimes the fire will burn up, away from the floor of the CC and go out. But other than that, when the flap opens, the fire re-ignites and will continue to do so until the fuel is gone.

Is there a possibility that the WG really does shut the air off so much that it kills the fire? whereas the GW and others let more air through, thus keeping the embers alive??

Jimbo
 
From what I see there are only 2 ways for fresh air to get into the CC(assuming the door is closed of course!). Either air enters thru the fresh air intake or somehow air enters backwards from the chimney(I'm not even sure if that is physically possible?).

So, presuming that the fresh air intake tube is the only way to bring air to the fire.....If the fresh air intake tube rim is fairly clean and if the silicone gasket part of the fesh air intake "flap" is also fairly clean...and based on the pressure of the arm that holds the flap to the air intake tube rim I would have to say that there is NO air getting to the coals/fire in the CC.

Now, with that siad I am at a loss as to how the coals will refire after 1+ hours of no air. Can red hot coals maintain themslf with no air for that long a period...seems so....unless air is backflowing into the CC from the piping into the chimney and I would have to guess it must be a very windy day for that to happen?
 
ISeeDeadBTUs said:
A thread from a WG user got me to thinking . . .

One of the claims I think of the GW and presumably other RMND units, were that the fuel would reignite from the heat held in the refractory. The pyrotechnics of that could be debated for hours. BUT . . . I do not think I have EVER had the fire go out because of long off-cycling. As long as I don't use SFW (crap 4 wood) I have never had the fire go out with wood in the CC.

If I over-remove ashes, or I put uglies in (root balls), then sometimes the fire will burn up, away from the floor of the CC and go out. But other than that, when the flap opens, the fire re-ignites and will continue to do so until the fuel is gone.

Is there a possibility that the WG really does shut the air off so much that it kills the fire? whereas the GW and others let more air through, thus keeping the embers alive??

Jimbo

Jimbo,
A couple questions.
Are you running a GW?
What size is it?
How much do you usually leave for ashes in the bottom of the CC?
 
muncybob said:
From what I see there are only 2 ways for fresh air to get into the CC(assuming the door is closed of course!). Either air enters thru the fresh air intake or somehow air enters backwards from the chimney(I'm not even sure if that is physically possible?).

So, presuming that the fresh air intake tube is the only way to bring air to the fire.....If the fresh air intake tube rim is fairly clean and if the silicone gasket part of the fesh air intake "flap" is also fairly clean...and based on the pressure of the arm that holds the flap to the air intake tube rim I would have to say that there is NO air getting to the coals/fire in the CC.

Now, with that siad I am at a loss as to how the coals will refire after 1+ hours of no air. Can red hot coals maintain themslf with no air for that long a period...seems so....unless air is backflowing into the CC from the piping into the chimney and I would have to guess it must be a very windy day for that to happen?
Bob. I wondered the same thing before I got mu Gun. What conviced me was.... on my farm I was burning junk wood and other brush in a big (Machine loaded) fire. It burnt out and over the next month or so I continued to clean up this pc. of woods I was working on and I had, prolly a 8' high pile X about 14X20 area. Now by then at least 5 weeks had pased with the normal rains (it was fall in MD). Well first thing one morning while walking down the hall to the #1 room, I saw this orange reflection bouncing off the glass on a wall picture and ran to the other side of the house to see a full blown roaring fire (my pile)! We had a skiff of snow that night and I was so convinced that somebody lit it that I got the 4 wheeler and drove all around the fire looking for foot prints! There were none, but the day before ad that day was VERY windy. I spoke to the firemen (my neighbors) and they said that with enough wind........ I became a believer.
 
I believe the refractory holds temps over combustion levels which allows the fire to be maintained. I don't believe I've ever found unburned wood in the CC, even wet elm burns down.
 
Tigermaple sums up what I was told about the GW refractory holding enough heat to reignite the fire when the call came. ONLY I was told it would hold the heat for up to 24 hours. The GW's were more expensive than the EKO and WG was not close enough to view. I believed what I read about the EKO and went that way and it has lived up to the brag or at least it did until I had to pull it of line.
 
Cave2k said:
Tigermaple sums up what I was told about the GW refractory holding enough heat to reignite the fire when the call came. ONLY I was told it would hold the heat for up to 24 hours. The GW's were more expensive than the EKO and WG was not close enough to view. I believed what I read about the EKO and went that way and it has lived up to the brag or at least it did until I had to pull it of line.

Cave2k

Can you explain what you meant here. Tigermaple? 24 hours sounds like a long time. Until you had to pull it off line? What happened to your EKO? How long did you run it? What do you have to do to fix it?
 
tigermaple said:
I believe the refractory holds temps over combustion levels which allows the fire to be maintained. I don't believe I've ever found unburned wood in the CC, even wet elm burns down.

I have never seen any other gasification boiler in person except for the Wood Gun.
The WG refractory is a HUGE half round block of cement that the wood lays on. there are 2 ports on either side of the gasification tube(the center tube with the white block with handle) that are part of the refractory as well.
Is that what other units have as well?
FYI the center port in the steel has the induction fan on the other end and the port just up off on the right is where the oil chamber would let heat pass in from.

1002953i.jpg


What i'm told is the air vent completely seals not allowing O2 in and as long as the refractory doesn't go below 640* ( the temp to ignite wood) when O2 is introduced it will "relight"

Isn't that what gasification is kinda all about any way? Igniting a fuel(that normally would float up the flue) because you introduced O2 and had a high enough temp?

Remember this all comes from a guy who's never burned a stick of wood or even seen any other units in person.
 
Gasifier said:
Cave2k said:
Tigermaple sums up what I was told about the GW refractory holding enough heat to reignite the fire when the call came. ONLY I was told it would hold the heat for up to 24 hours. The GW's were more expensive than the EKO and WG was not close enough to view. I believed what I read about the EKO and went that way and it has lived up to the brag or at least it did until I had to pull it of line.

Cave2k

Can you explain what you meant here. Tigermaple? 24 hours sounds like a long time. Until you had to pull it off line? What happened to your EKO? How long did you run it? What do you have to do to fix it?

Sales rep for GW said the GW would hold heat in the refractory for up to 24 hrs so idling was no problem.
My EKO sprung a leak on the bottom about the same time I was forced to pull it off line because of a change in posture by the insurance company. It's still off line awaiting a building or conversion to an "outside" model. Meantime I am cutting and stacking wood and stuffing a locally constructed "ceramic" boiler. The ceramic was supposed to be more wood miserly than a standard OWB. I think it is not but it works and the heat season is here and the EKO conversion can take a few steps forward.
 
muncybob said:
From what I see there are only 2 ways for fresh air to get into the CC(assuming the door is closed of course!). Either air enters thru the fresh air intake or somehow air enters backwards from the chimney(I'm not even sure if that is physically possible?).

So, presuming that the fresh air intake tube is the only way to bring air to the fire.....If the fresh air intake tube rim is fairly clean and if the silicone gasket part of the fesh air intake "flap" is also fairly clean...and based on the pressure of the arm that holds the flap to the air intake tube rim I would have to say that there is NO air getting to the coals/fire in the CC.

Now, with that siad I am at a loss as to how the coals will refire after 1+ hours of no air. Can red hot coals maintain themslf with no air for that long a period...seems so....unless air is backflowing into the CC from the piping into the chimney and I would have to guess it must be a very windy day for that to happen?
Bob,
By now you must have experienced an "explosion" caused by short cycling and after a period of time there is no explosion upon re-light. To me that indicates that the gasses went somewhere, presumably up the stack. They has to be replaced by something which I assume would be air from some source. I suspect the firebox is not totally devoid of oxygen. It has to have some leaks. I think with mine it was usually one of the door gaskets.
 
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