Wood Boiler Secondary Burn

[ramboiavzl]

ramboiavzl,
I have done something similar to what you are trying to do in my box in box boiler and have a fair amount of success, still not perfect but way better than just a box in box. PM and I will pass along my phone number its easier for me because I only get on the web once in a while at work. you might search my posts too for a little background info on my project.
Jason

I'm from Portugal.We can talk by other away like Skype for example

 

[ramboiavzl]

Today I made the modifications that BoiledOver suggested. I didn't get much secondary burn in the tube.I don't if it's because of insufficient oxygen(Only tested with 1 tube with 1'' and my combustion chamber is big). By the way I notice that it seems that the flames by themselves are burning the gases because of my boiler design, but probably I'm wrong, I don't know.

 

[BoiledOver]

Today I made the modifications that BoiledOver suggested. I didn't get much secondary burn in the tube.I don't if it's because of insufficient oxygen(Only tested with 1 tube with 1'' and my combustion chamber is big). By the way I notice that it seems that the flames by themselves are burning the gases because of my boiler design, but probably I'm wrong, I don't know.

The design of this unit will make it difficult to see any actual secondary combustion. Once an access door is opened, it brings oxygen into the firebox and exchange tube area both. Do you think you will be able to control the air mixture between the firebox and the secondary inlet (the pipe you added)? Gasification occurs when there is not sufficient oxygen to create total combustion (smokey fire). Introduction of oxygen into the escaping gasses (smoke) creates the secondary combustion.

Perhaps a baffle with a nozzle for the exhaust route between the firebox and exchange tube area would help. This is how most gasification boilers are designed, upside down to your boiler. The EKO for instance has the firebox above for gasification with a slotted opening in the floor, approximately 1"x6". The gasified fuel (smoke) travels down through the slot which has air channels built into the sides. The result is a secondary flame expanding downwards into the secondary chamber.

Would like to hear from @cumminstinkerer concerning this theory. And anyone else too. If I have offered erroneous info, please advise.

 

[cumminstinkerer]

mine is not a perfect gasser for sure but it is way cleaner and hotter than a box in box. I am now running two draft fans off of HE furnaces for my intakes, primary and secondary. I have them both regulated by homemade butterfly valves ( throttle blades). I have the box lined with brick and a baffle of brick that the secondary tubes are under basically right against the baffle. I tried with one fan but just could not get enough air to it. When I added the second fan it works way better. I am sure its not as efficient as a downdraft gasser but i cut my wood use in about half. I run about 600*F surface temps on the outlet to my flue Gas HX, 10GA mild steel cover, no probe but my best guess is I am running 1200+ in the actual gas stream. If/when i move and go to do another setup I am going to build a dd gasser for sure, when I first built this one I really had no idea about clean burning and hadn't found this site, after I found Hearth and started learning things I started trying to improve what I had, way cheaper than a new build for sure. I get a pretty darn clean burn, it still idles though but cleans up quick after it calls for fire.my avatar is of it about five minutes after a fresh load so pretty clean. ramboiavzl I am not really very computer savy, I do not even have one at home, I have a smart phone but i am to dumb to run it. PM and we can maybe use Facebook messenger. I am just a farm boy that likes to tinker and learn, if its got pistons and fuel injectors, and prefer a turbo or two watch out I can make it wicked, thus my screenname. I actually was pondering using an old TO40 borg warner turbo for a draft fan but have yet to figure out how to get the needed RPMs and keep it lubed. I have a 5/8 hole drilled in my loading that I use for viewing the fire, and it appears that it also aids in the secondary flame, if i close it I lose a bit flue temp. I wont say i am an expert by any means and I visit and learn stuff from a couple real good guys on here and we trade ideas, Thanks to warno and born2burn. I will certainly help as much as I can though.

 

[cumminstinkerer]

BoiledOver, your theory is pretty much how I modified mine, I don't think I have any pictures on here and my phone camera is....well fried from trying to video the secondary flame through my viewing port lol. My flue gas HX was added a fair bit later than the other mods, just put it on last year, think I have a thread here on it. I welcome any and all suggestions and input. I will see if I have a couple sketches I made of the basic design, if i don't I will redo them and add them here.

 

[ramboiavzl]

The design of this unit will make it difficult to see any actual secondary combustion. Once an access door is opened, it brings oxygen into the firebox and exchange tube area both. Do you think you will be able to control the air mixture between the firebox and the secondary inlet (the pipe you added)? Gasification occurs when there is not sufficient oxygen to create total combustion (smokey fire). Introduction of oxygen into the escaping gasses (smoke) creates the secondary combustion.

One of my problems is that.I need to open the door to see what is happening inside of the firebox.I also have a damper in my chimney and I can control the speed of the flue gas.

cumminstinkerer, do you think I need a fan to create secondary combustion?

Give me your facebook account by private message by the way.

Thank you

 

[BoiledOver]

One of my problems is that.I need to open the door to see what is happening inside of the firebox.I also have a damper in my chimney and I can control the speed of the flue gas.

The flue gas control is good, but the introduction of air (oxygen), to divided areas is better. The main exhaust (primary and secondary) can remain wide open as you control between primary and secondary in oxygen input flow. A division of combustion chambers may be essential, something to consider.

 

[cumminstinkerer]

ramboiavzl,That is the only way i can get mine to work, but I also have a very short chimney. I run on draft inducer fan from a high efficiency LPG furnace supplying air to the bottom right into the main fire, running all but wide open on my homemade throttle. The secondary supply is another draft inducer from another HE furnace, feeding into a tee that branches out to two one inch black iron pipes that pass through the coal be and then rise up to just under the baffle and then exit through a series of holes drilled in the tubes. I did some air adjustments over the past few days and meeting with a fellow from AS that has a downdraft and watching how it burns I have been able to sustain the secondary flame under the baffle and keep the exhaust to no smoke to a very small amount on a fresh load. I am really pretty happy with the results. I will PM with my real name and then we can try Facebook, so we can visit when I am not at work.

 

[ramboiavzl]

The flue gas control is good, but the introduction of air (oxygen), to divided areas is better. The main exhaust (primary and secondary) can remain wide open as you control between primary and secondary in oxygen input flow. A division of combustion chambers may be essential, something to consider

What do you mean with a division of combustion chambers? LIke Primary chamber in one chamber and Secondary in another chamber? If it that for me it's impossible because of the design of my wood boiler.

 

[ramboiavzl]

ramboiavzl,That is the only way i can get mine to work, but I also have a very short chimney. I run on draft inducer fan from a high efficiency LPG furnace supplying air to the bottom right into the main fire, running all but wide open on my homemade throttle. The secondary supply is another draft inducer from another HE furnace, feeding into a tee that branches out to two one inch black iron pipes that pass through the coal be and then rise up to just under the baffle and then exit through a series of holes drilled in the tubes. I did some air adjustments over the past few days and meeting with a fellow from AS that has a downdraft and watching how it burns I have been able to sustain the secondary flame under the baffle and keep the exhaust to no smoke to a very small amount on a fresh load. I am really pretty happy with the results. I will PM with my real name and then we can try Facebook, so we can visit when I am not at work.

Now I'm trying only with one tube with lots of holes in almost 1,20 m of 1'' tube. The tube pass through the coal be and then rise up to just under the baffle and then exit through a series of holes drilled in the tube.My problem is that I can't see what is happening inside of combustion chamber and I open the door oxygen entry in the box. My chimney tube have almost 7m by 26'' diameter so I think I have enough good draft. If put damper in open position in the exhaust gas I have insane fire in combustion chamber

 

[Sword350]

Hey there, I'm not exactly new to wood burning but new to here. I've recently picked up a old indoor wood boiler for cheap and I'm looking into doing something similar. I have a blaze king insert so im pretty familiar with the secondary combustion idea and have done other research on the subject. Im working on getting this boiler set up as a piggy back on my oil boiler and i think i want to do something similar as to whats been mentioned here. Jw if you ever had any luck with getting it set up or anyone on here reading this has had an indoor boiler and achieved at least decent secondary combustion. I'm mostly just looking to keep creosote down and improve on efficiency a little. Some of worries with the secondary though is that theres no control to it, i dont want flames shooting out the exhaust pipe and into my chimney either. Ill post some pics if my boiler here once i get it a little further along. Just got it into the basement yesterday. Thanks for any input.

 

[ramboiavzl]

Hey there, I'm not exactly new to wood burning but new to here. I've recently picked up a old indoor wood boiler for cheap and I'm looking into doing something similar. I have a blaze king insert so im pretty familiar with the secondary combustion idea and have done other research on the subject. Im working on getting this boiler set up as a piggy back on my oil boiler and i think i want to do something similar as to whats been mentioned here. Jw if you ever had any luck with getting it set up or anyone on here reading this has had an indoor boiler and achieved at least decent secondary combustion. I'm mostly just looking to keep creosote down and improve on efficiency a little. Some of worries with the secondary though is that theres no control to it, i dont want flames shooting out the exhaust pipe and into my chimney either. Ill post some pics if my boiler here once i get it a little further along. Just got it into the basement yesterday. Thanks for any input.

Did you had success with secondary burn?

 

[Sword350]

No i never tried got busy with some other stuff this winter. Ended up using the boiler only a month and switched back to my insert cause the boilers too damn inefficient as it sits. Ive gotten fascinated too with the gasification boilers and seeing the ones other people have built i think I'm going to do a major overhaul on my boiler and build it into a gasification one this summer.

 

[warno]

No i never tried got busy with some other stuff this winter. Ended up using the boiler only a month and switched back to my insert cause the boilers too damn inefficient as it sits. Ive gotten fascinated too with the gasification boilers and seeing the ones other people have built i think I'm going to do a major overhaul on my boiler and build it into a gasification one this summer.

Be sure you do test fires through the summer to make sure your modifications work. I failed to do this and it bit me in the butt this winter.

 

[cumminstinkerer]

@Sword350 shoot me a PM I'll give you the run down of mine. ramboiavzl, check out my thread on the heat exchanger here, i have made a bunch more changes and things are really going well, warno is going to send a flue gas analyzer so i can see how clean i've really gotten it