help with Mt. Vesuvius coming out the top

[Stamford sugarmaker]

We've got a new 2 X 4 this season and boiled with it twice. The 7" stack is a little more than 10' high. I load the wrist-sized wood in a criss cross pattern as much as possible. I use a small 50cfm blower. During certain times of the burn, flames shoot out the top. An external stack thermometer sometimes gets pegged at 900 F.

During a test boil I had a cap on top but it restricted the flow too much and I removed it. Now it's a straight unrestricted path out the top.

I've read that flames out the top mean unburned gasses in the firebox and reduces efficiency. Although I'm not too concerned with fire danger, partly because the sugarhouse roof is metal, any suggestions as to how to reduce or eliminate the flames?

thanks, Peter

[C.Wilcox]

I get the same thing and use it as a gauge of when I'm firing right. No Mt. Vesuvius? Add more wood. :-)

[oneoldsap]

Let her rip , 900 isn't a bad stack temperature , 1,000 is better though ! You are going to have unburned fuel because your arch can't utilize it all without the ability to reburn the gasses . That technology is available , but it'll cost ya . Check out the LaPierre Force-5 ! Keep your stack temp as high as you can , when it drops 100-150 degrees , put the wood to it . You want to get as close to or exceed the rated evaporation rate for your rig , IMHO !
Mike

[wiam]

The flames are unburned gases. Some say wasted wood. I say I boil a lot of sap in a hurry with my stack around 1200. The day before yesterday I saw it at 1425. This was with a probe thermometer from Condar. In my opinion wood is cheap and time is money.

[Stamford sugarmaker]

The consensus seems to be, "Let 'er rip". Since there doesn't seem to be any opposing views she will be ripped.

Peter

[RollinsOrchards]

Now I don't know for sure, but it seems to me that this "olympic torch" effect as i call it is because the hot "smoke" is finally getting more air when it gets to the top of the chimney. So to my idealistic thinking if you could add more air to the firebox "behind" the flames you could get that same inferno down where it will do some good. If LaPierre can do it, I am sure there is a possibility of doing that on a DIY scale.

[nymapleguy607]

Now I don't know for sure, but it seems to me that this "olympic torch" effect as i call it is because the hot "smoke" is finally getting more air when it gets to the top of the chimney. So to my idealistic thinking if you could add more air to the firebox "behind" the flames you could get that same inferno down where it will do some good. If LaPierre can do it, I am sure there is a possibility of doing that on a DIY scale.

It can be done but you need space for that to happen more space than what is availible in a 2x4. I think you're wasting some wood firing that hard though(wow never thought I'd say that :) ) Are the pans boiling good and hard if you reduce the air from the blower?

[PerryW]

The flames are unburned gases. Some say wasted wood. I say I boil a lot of sap in a hurry with my stack around 1200. The day before yesterday I saw it at 1425. This was with a probe thermometer from Condar. In my opinion wood is cheap and time is money.

I guess if I was boiling concentrate, I would probably not worry so much about how efficiently I burned my wood.

[Amber Gold]

My thought is, if the wood is small and the firebox fueled frequently, the fire stays nice and consistently hot. I like running my stack temps around 1500F and get ~85gph. If I cool things down, my wood consumption goes down accordingly, but so doesn't my evap. rate. You have to figure if your stack temp's at 1500F, the fire in your arch is hotter. Hotter fire = harder boil. My flue pan's rocking and rolling the full length.

[maple2]

i have found that if your stack is too tall, it will suck the heat and gases out of the firebox too quickly. if you have a hole in your base stack, you will suck in fresh air and the unburned gases will reignite. pretty impressive, at night with flames shooting out the chimney!

[maple2]

p. s. i visited a sugarhouse, years ago, the guy worked for the railroad and burned railroad ties. about 12ft of flame! old tires work great,too

[Stamford sugarmaker]

"Are the pans boiling good and hard if you reduce the air from the blower? "

No, if I turn off the blower it doesn't boil nearly as hard.

I can't really reduce the height of the stack. As it is, it only protrudes about a foot above the metal roof.

It sure would be nice, though, to get that inferno at the top of the stack inside the firebox...

Peter

[nymapleguy607]

Hmmm, thats interesting is the blower on a rehostat control. That would allow you to dial in on the optimal speed, but before you add one make sure you know what type of motor it is. I believe if its a shaded pole motor you can use one but if its not it could burn up. other than that maybe try and build a heat dam towards the end of the flue pan to try and cut back on the amount of draft. The only other thing I could think of is maybe your wood is too big and giving off smoke thats not getting burned. For a 2' arch I think they recommend wood 2-3" in diameter.

[Stamford sugarmaker]

The motor says you cannot put a rheostat on it. If anything, I think the 50cfm motor might be a bit too small. Maybe more air blown in would ignite the unburned gasses.