Homemade and Engineered Gasification Boiler

[Born2burn]

New to the forum, but have been visiting for some time reading up on gasification boilers.. Thank you for all your post.

Wanted to share my gasification water heater that I built and is running on its second season now. I don't like calling it a boiler because I am not making steam. Anyway I did some simple calculations in my head for the size of the firebox, the secondary chamber and the heat exchanger on the backend. It is a down draft gasser, I have a preheater for the primary air and the secondary air has a second air heater. I have a 2" valve that I can control the secondary air for future o2 controller I would like to install. The water to flue gas heat exchanger is a retired 200 gallon propane tank that I gutted and installed 13 tubes in that are 2" in diameter and 5 feet long. I use some 1/4 in chain for turbulators and welding a some pipe on the end so I could chuck a drill to the end and use the chain as a pipe cleaner also. The heat exchanger is a pressurized one to keep the o2 out of the water. I have two 15 psi relief valve and one temp and pressure relief valves so the unit don't become a bomb in an event of over firing. I also have a 195 degree high water temp cutout to completely shut power down. UPS power backup for the water circulators to keep water moving in an event of power interruption.

I do achieve around 1500 to 1800 secondary flame, the fire box will hold roughly 7 to 10 cubic feet of wood. I get a continued 12 hour plus burn time. I load it at 5 am in the morning and then 6pm at night typically. I never let the water get below 150F and no hotter than 175F. I heat 2600 square foot 1910 fairly good insulated 1 and 1/2 story house using heat coils in the furnace. Also heat a 1200 square foot shop with radiant floor heat, will also be heating 3000 more square feet at 50F when I get my shop floor poured. The wood gasser sits in a 20 by 23 poorly insulated old garage that is about 65F from heat loss from the wood gasser. My flue gas temps range from 225F to 300F.

I will post some pics below, I could write about this thing all day. I learned a lot from the build and had to tweet air flows for about a month before I got it to work properly. Now I just load and go.

 

[warno]

Looks good. Could I see how you hooked up that propane tank into the mix? I'm guessing that's your heat exchange tubes running through it?

 

[hondaracer2oo4]

Well done! Interesting approach with no water around the firebox, only in the self contained hx. Appears to be very efficient at moving the heat into te water if your flue temps are accurate. Are you having issues with the flue gasses collapsing and condensing in the hx at those really low temps? How did you measure them? Where are you located geographically and how much wood do you go through for your season? We love the pictures around here, if you have any more we would love to see them!

 

[Born2burn]

Looks good. Could I see how you hooked up that propane tank into the mix? I'm guessing that's your heat exchange tubes running through it?

Yes it is. The heat exchanger is sitting vertical on the back side of the gasser. The gasses travel through the secondary chamber refractory lined (the bottom door) and then through the 13 tubes and then out the top of the flue which is the belled end that is removable for cleaning. I will dig up a few more pics for you. And thanks for the comments, I was very discouraged at first when everyone said homemade gassers are won't work.

 

[Born2burn]

I did not like 170F water around the fire box because to me it is like burning a fire inside of an ice box. To get temps correct in my opinion the fire box should be over 500F and be easily maintained for pyrolysis to occur. I put 2 inches of plastec 85 refractory around the firebox except the top. The top and the sides preheat my primary and secondary air. My flue temp is measured by a thermocouple at the top of the belled end of the heat exchanger where the gases collect and go out the flue. I believe it is fairly accurate. I use a Rocks BBQ Stoker 2 to remotely monitor my temps. I would really like to invest in a vesta controller for my gasser. As for condensing, it is not a problem until really below about 130F, I play it safe and run minimum water temp at 150F. I do run about 10 to 20 percent moister wood. The water returns com in the top 3/4 of the heat exchanger through an inside pipe to it can pick up heat along the way so the bottom of the heat exchanger does not get to cold. I'm located in the eastern part of Nebraska, winters are not to bad here but just bad enough! I will post more pics when I get some time.

 

[hondaracer2oo4]

I agree with the cold firebox issues. Any creosote build up in the firebox? My G series is surrounded by water which means that even when the boiler is at idle the hot coals are still radiating heat inside the firebox and transferring some of that heat into the water jacket. I have a thin oily layer of creosote on the parts of the firebox that touch the water jacket. I thought that the manufacturers were shooting for around 350 flue temps because of the concern about condensing flue gasses if they went below that number. Maybe I am wrong. How many cords do you go through?

 

[Born2burn]

I agree with the cold firebox issues. Any creosote build up in the firebox? My G series is surrounded by water which means that even when the boiler is at idle the hot coals are still radiating heat inside the firebox and transferring some of that heat into the water jacket. I have a thin oily layer of creosote on the parts of the firebox that touch the water jacket. I thought that the manufacturers were shooting for around 350 flue temps because of the concern about condensing flue gasses if they went below that number. Maybe I am wrong. How many cords do you go through?

I believe last year I went through a lot, for sure 20 cords plus. But I had about 25 to 30 on moisture for would. I did condense out a little last year because my secondary combustion was hindered by the moisture. The other day I did weigh the wood and out of 125lbs I got 13 hours plus still had a lot of charcoal in the bed.
Attached are some pics of the tubes and the flue where I take the temperature. There is starting to have al little build up from some condensing. I have only had about 4 startups so far this year from October 25. So far I burned about 1.2 cords roughly. I has only been in the 40F and now with snow it is 20F. I forgot to mention I do heat all my hot water for the house, I have 6 in the family, lots of endless showering.
The firebox pic is what I loaded last night around 7pm and this is what was left about 8:30am this morning.
Oh and yes I do have the back side of the firebox is the heat exchanger wall. I gets a nice shiny creosote on it and is does condense out during burns. I work in a coal fired power plant and are flue temps are from 300F to 325F. We burn 35 percent moisture coal too. Never have anything condense.

 

[Vinced]

Nice build. Any pictures of the back before insulation? I'm curious how you joined the propane tank heat exchanger to the firebox/secondary burn tunnel?

 

[warno]

I'm interested in that connection as well.

More pitchers please!

 

[hondaracer2oo4]

20 full cords or face cords?!?! If that is 20 full cords I think you may have a problem somewhere. If your flue temps are that low that means you are getting the heat into the water so you are losing your btus somewhere else. What do you have for underground lines? Have you measured your temp loss from the boiler to the house?

 

[Born2burn]

This is what it looked like last year, I was in a hurry with winter on my door step. I had tremendous heat loss from it radiating into the garage. It was 80 or 90 in there when it was -5f outside and it was just a tin pole shed I uninsulated at the time. I have about 1 degree heat loss with the variable speed bumblebee pump running at minimum and 0 degree loss at full speed, on a 100ft run. According to my heat gun! I do not have any of the pipes insulated in the garage and the house yet. The pipes underground the hots are separate from the cold ones, in a different housing pipe. I have my own insulating material (proprietary) and an air space between the material and the housing pipe which is buried 8' in the ground that is 55F.

 

[Born2burn]

20 full cords or face cords?!?! If that is 20 full cords I think you may have a problem somewhere. If your flue temps are that low that means you are getting the heat into the water so you are losing your btus somewhere else. What do you have for underground lines? Have you measured your temp loss from the boiler to the house?

Oh and for the 20 full cords, it is pretty much a guess, I know I burned 10 for sure that was in my wood shed but the res was cut as I went and blended, so I'm not sure exactly what I all burned! I will try to keep a better record this year. I have lot and lots of wood at my dispose, I burn anything from pine to walnut.

 

[hondaracer2oo4]

Well it sounds like your not losing your btus into the ground. Just don't know how you managed to go through 20 cords with a gasser with low flue temps, it doesn't make sense to me. What were you heating with before and how much were you going through?

 

[Born2burn]

Well it sounds like your not losing your btus into the ground. Just don't know how you managed to go through 20 cords with a gasser with low flue temps, it doesn't make sense to me. What were you heating with before and how much were you going through?

I have a englander box stove I use to go through 7 cords a year with it. That heated the 2600sq ft house! That's all I used and maybe burned 100 gallon of propane for supplement when gone! I believe I lost lots to inside the garage, because the sides of the gasser where not insulated. That takes lot of btus to heat a 20x 23 drafty garage! Plus I heat a 1200sq ft shop 12' sidewalls with one wall adjoining the 3000sq ft shop that is uninsulated yet. So some more heat loss!

 

[Born2burn]

How much wood do other gassers use?

 

[maple1]

I use maybe around 6 cords per year. That's a 2700 sq.ft. 20 year old two storey, with another 1500 in unfinished basement, where the boiler is.

Interesting having the primary firebox not water jacketed (except for the back where the tank is) and not just the secondary chamber. I don't think I've seen that in a ('factory') downdraft gasser before. That might make return temp protection not so much a concern also.

Nice work!

 

[huffdawg]

I use maybe around 6 cords per year. That's a 2700 sq.ft. 20 year old two storey, with another 1500 in unfinished basement, where the boiler is.

Interesting having the primary firebox not water jacketed (except for the back where the tank is) and not just the secondary chamber. I don't think I've seen that in a ('factory') downdraft gasser before. That might make return temp protection not so much a concern also.

Nice work!

Do u heat your domestic hot water too?

 

[maple1]

Yes. Most of the time.

Last summer I decided not to burn wood for DHW, so turned the electric water heater on. I burned all summer the two summers before that, and when I was doing that I was burning up junk wood. But whenever I'm burning wood, I'm heating DHW.

 

[Tennman]

Seeing your design and fab skills I just wanted to give you a big congrats. Great seeing creativity and perspiration come together solve a problem. I'll bet your pretty successful in your chosen profession. Congrats

 

[maple1]

Not seeing a combustion fan. So this is natural draft? That, I can appreciate.

 

[hondaracer2oo4]

Obviously the amount of wood used by anyone is dependent on heat load. Your house isn't going to be a huge load since you used 7 cords in a wood stove and heated it fine. The shop is a draw but I doubt you heated it at 70 degrees 24x7. You certainly lost a lot to the boiler room if it was 90 degrees in there. I used to go through 12 or more cords with my conventional owb heating 2700 sqft 220 year old decently insulated 2 story colonial and my dhw for two in New Hampshire. This is my first year with the gasser but I should be in the range of 6-7 cords at the end of the season judging by my consumption so far.

 

[Karl_northwind]

I like it! I've seen a lot of boiler designs, and if you're going to have it in a heated space, I think the non-water jacketed option is great for a homebuilt boiler. The HX you built there is a nice setup. I think I'd have gone bigger on the flue tubes, (you can turbulate or not, but you can't make them bigger) but other than that, I have nothing I'd add. I have to wonder if the water jacketed fireboxes on the commercial boilers make shutdown easier (by removing heat from the firebox and helping control the off-gassing of your fuel wood. )
without return protection, the low moisture content wood is critical.
I thought about doing something similar once upon a time, because I can weld a water tight circle, but am not sure about long straight welds. what with warping and such. I though a 100 gal LP tank would be a good starting point.

 

[Born2burn]

Obviously the amount of wood used by anyone is dependent on heat load. Your house isn't going to be a huge load since you used 7 cords in a wood stove and heated it fine. The shop is a draw but I doubt you heated it at 70 degrees 24x7. You certainly lost a lot to the boiler room if it was 90 degrees in there. I used to go through 12 or more cords with my conventional owb heating 2700 sqft 220 year old decently insulated 2 story colonial and my dhw for two in New Hampshire. This is my first year with the gasser but I should be in the range of 6-7 cords at the end of the season judging by my consumption so far.

I use maybe around 6 cords per year. That's a 2700 sq.ft. 20 year old two storey, with another 1500 in unfinished basement, where the boiler is.

Interesting having the primary firebox not water jacketed (except for the back where the tank is) and not just the secondary chamber. I don't think I've seen that in a ('factory') downdraft gasser before. That might make return temp protection not so much a concern also.

Nice work!

Thanks I wanted to do a low psi system and for me and my time it was the best approach without doing a bunch of stay bolts on flat steel!

 

[Born2burn]

T

Seeing your design and fab skills I just wanted to give you a big congrats. Great seeing creativity and perspiration come together solve a problem. I'll bet your pretty successful in your chosen profession. Congrats

Thanks, I do love what I do and I love building things. I like burning wood and wanted a new challenge. Plus It is good exercise which a lot of people pay to do. Now I just have to master controls and make things more efficient.

 

[Born2burn]

My primary air fan uses about 67 watts, hey I was in a pinch I hate to change it just works to well. My actuator is fail closed so it almost eliminates natural draft. I would like a better air cut off if anyone has any ideas!