Conventional Boiler Upgrade - DIY

[doco2279]

Good afternoon,

I've been running a Tennessee Outdoor Furnace 300 for two seasons. It has performed satisfactorily, but I'm trying to get the most out of it. I've been doing a lot of reading around the internet and I've got a few questions that maybe you guys can help with.
First of all, adding firebrick to the firebox. I've read both pros and cons. From everything I've read, it looks like I'd get the biggest bang for my buck by lining the floor and possibly half way up the sides, since this is a boiler and I still want good heat transfer to the water.
Secondly, obtaining a secondary burn. I've seen several designs out there for DIY'er like myself. I've done a crude drawing of what I'm thinking of doing based on a design that I saw on this site. That post is several years old so that's why I'm posting a new post about it. My particular model boiler is power draft fed through a tube from the back of the boiler to the front. My though was to run a pipe from the top of the draft tube, tee it off to both sides of the firebox, run the pipe to the front of the unit and make a u-turn to the back of the unit. Than I would have tubes running across the top of the firebox with outlet holes pointing down. I would assume, running the air-flow in this manner would heat the air prior to exhausting onto the fire.
Any thoughts on either of these two would be greatly appreciated.
As an aside, I've been burning both wood and bituminous coal. Lately just bit coal since I can get it a lot cheaper than buying cord wood, since I rarely have time to cut and split my own.

Pic 1: Unadulterated Firebox - Note, this is an older model. My model does not have the tube coming down in the back.
Pic 2: Planned upgrade
Pic 3: Design based off of

Thanks,

 

[Pat32rf]

Can't quote any studies, but I feel that the hotter you can run your fire, the more efficient it will be. This means getting firebrick between the flame and that cold steel.
I bought an old design P&M model ML. The next year they added firebrick similar to your idea...making a pretty good boiler even better.

 

[frc00ny]

Good afternoon,

I've been running a Tennessee Outdoor Furnace 300 for two seasons. It has performed satisfactorily, but I'm trying to get the most out of it. I've been doing a lot of reading around the internet and I've got a few questions that maybe you guys can help with.
First of all, adding firebrick to the firebox. I've read both pros and cons. From everything I've read, it looks like I'd get the biggest bang for my buck by lining the floor and possibly half way up the sides, since this is a boiler and I still want good heat transfer to the water.
Secondly, obtaining a secondary burn. I've seen several designs out there for DIY'er like myself. I've done a crude drawing of what I'm thinking of doing based on a design that I saw on this site. That post is several years old so that's why I'm posting a new post about it. My particular model boiler is power draft fed through a tube from the back of the boiler to the front. My though was to run a pipe from the top of the draft tube, tee it off to both sides of the firebox, run the pipe to the front of the unit and make a u-turn to the back of the unit. Than I would have tubes running across the top of the firebox with outlet holes pointing down. I would assume, running the air-flow in this manner would heat the air prior to exhausting onto the fire.
Any thoughts on either of these two would be greatly appreciated.
As an aside, I've been burning both wood and bituminous coal. Lately just bit coal since I can get it a lot cheaper than buying cord wood, since I rarely have time to cut and split my own.

Pic 1: Unadulterated Firebox - Note, this is an older model. My model does not have the tube coming down in the back.
Pic 2: Planned upgrade
Pic 3: Design based off of

Thanks, View attachment 175204 View attachment 175205 View attachment 175206

would adding the fire brick also help reduce corrosion from the ceosote?
The brick would get pretty hot and stay that way, pretty much like a stove or furnace.
Hopefully some one will chime in because i am thinking of modifying my gassifier with more fire brick to accomplish this same thing.

 

[doco2279]

would adding the fire brick also help reduce corrosion from the ceosote?
The brick would get pretty hot and stay that way, pretty much like a stove or furnace.
Hopefully some one will chime in because i am thinking of modifying my gassifier with more fire brick to accomplish this same thing.

Well, what I was thinking was the fire brick would a) prevent corrosion, b) retain heat instead of letting it go out the stack, c) if I am running my over the air fire tubes next to the brick or on top of it, that will pre-heat the air and maybe help with burning off volitiles. At least that was my thinking. I'm trying to burn coal, so the first upgrade has to be over the air fire (since it is bituminous coal). The firebox is so massive in this thing, it is hard getting the fire hot enough to heat the water. I've been burning coal like crazy and my boiler only gets to 160 max and it is hard as hell to hold it there. My burn times are abysmal and I'm assuming its because of the lack of fire brick and the lack of over the fire air. It burns like crazy when I leave the door cracked open, but when the boiler is shut up, it kind of just smolders and never gets really hot.