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[binfordw]

Hi,  New here, been reading what I can.

I'm set to build a Gasifier boiler this year, and believe I have the basics figured. 

What are some of the key elements that I need to focus on for a successful build?  Anything I need to make sure I give extra thought?

[vpd66]

Nozzle size, nozzle target refractory material, correct sizing of the heat exchanger, amount of primary intake air, and the amount of secondary intake air. Those are just a few perimeters that need to be engineered correctly. I think the biggest thing is that the technology is so new that there isn't that much engineering info out there for us DIYers to figure out some these things. If I was to build a Gasification boiler, I would find a factory built one sized to your needs and take some measurements and reverse engineer it. Just my 2 cents.

[binfordw]

Nozzle being the port/ports in the bottom of burn chamber correct?   If so these could be changed fairly easily after build was complete if they turned out to be too big/too small.

Airflow, primary (burn chamber air/pressure?)  Secondary, (the airflow to mix with "smoke" to help re-burn right?)  These could be adjustable and tweaked after build as well.

Size of heat exchanger- This is for airflow concerns?   I agree this would need to be done pretty close to right the first time.  Although, should be easy enough to copy a working stoves tube sizes. 

What about the Target area refractory material?  Just so it holds up to the heat?

Thanks so much for your input and suggestions.  Hopefully I can get 99% of the questionable sections of this build figured out before I start, I'm feeling better about it the more and more I read for sure.

[vpd66]

Nozzle size could be made large and reduced if needed along with primary and secondary intake air. On most Gasification boilers the main heat exchange is off the exhaust after the the secondary burn has occurred. So sizing of the exhaust heat exchange would be critical. Another thing to remember is the secondary burn chamber is exposed to over 2000 degrees. This is where the correct refractory comes into play. Most commercial Gasification boilers have replaceable refractory nozzles and targets. These are wear items that have to be replaced. Back around 2008 there was a guy about 60 miles from me that attempted to build a Gasification boiler and got it up and running but he only ran it for a couple months and then gave up on it because it kept burning itself up. Have you looked into a "Garn" style boiler? Its much larger but it is very simple compared to some of the modern Gasification boilers. I know there has been quite a few home built Garn style boilers and there very successful.

[binfordw]

No I haven't heard about Garn type boilers.

It doesn't sound like a mystery to install the correct refractory to me.  As long as one is aware of the temps and wear it will need to withstand, it shouldn't be an issue I wouldn't think. 

When you say sizing of the heat exchange is critical- in what manner- just mainly speaking for efficiency?  I realize it would need to be sized to handle the amount of exhaust/gases that need to pass through it of course.  I also understand too big would not strip heat from it as well/ much at all. 

I've read several postings that comment that gasifiers are too complex, high maintenance and possibly dangerous, but I have not yet really found out why.   For instance, one post commented that he had made several boilers, and that one suffered a catastrophic meltdown when the owner tried to load it while drunk. 

[vpd66]

Please do research the Garn style boiler. A guy on here that goes by "petemoss" built a nice Garn style. There is almost a picture by picture build of a Gasification boiler by a member named "jackel440" that he built and got up and running but seems to have not been around since 2012 so I don't know how it worked out. Also do a Google search of Professor Dick Hill's stick wood furnace. It seems to be the very first gasification wood boiler designed on a government grant back in the late seventies. A company in Canada made it and sold if for a few years ,but the concept just didn't catch on. There are a few people that still have and run them and there have been a few that have built a couple.
   Refractory isn't has simple has it sounds. There are many different types and molding,designing, and curing refractory is a art in itself. Refractory/firebrick wears or erodes almost everywhere it is used. Its just the nature of the beast. Also refractory doesn't like to be heated and cooled. This heating and cooling seems to take a lot of the durability out of it.
   Sounds like you have a lot of research to do before you start to build. Don't worry I've been researching and lurking around since 2007 and still not ready to build yet.

[mlappin]

Refractory can be had that has a high abrasion resistance, can also be had with a high resistance to thermal shock. It will cost more, but if it lasts longer is cost really a consideration then?

[renoman]

Built a gasification boiler based on the design of the p&m opt 250. One thing I can say is have your plans well laid out before you start and prepared to spend a lot of hours on your build. Took myself and my welder about three months of weekends and some evenings to complete this build but well worth the time.
My unit heats about 3000sq.' home and a 36 x 50 shop. The unit recovers very quickly, never smokes. and stack temps run 240 to 260 under full burn as long as the unit is clean. My firebox is lined with a double layer of firebrick on the floor and one row upright against the wall(9"). The slot in the bottom of the primary is about 3/4" wide by 8" long. The secondary burn chamber is the most difficult part to line.
My chamber being 18"w and 10" h x 40"deep was a challenge to line as I placed a double layer on the bottom, single layer on top,(underside of primary), and single layer on sides and mortar all in with high heat mortar. Burn chamber and heat exchangers were all fabbed together and pressure tested before inserting in to water jacket and then welded front of jacket on. Burn chambers and heat exchange completely surrounded on all sides by water. Double return and supply extend 3/4 and 1/4 into tank respectively. Unit has been running 13 months now successfully and wish I had done this many years ago.
(previous 5 yr average was $4000yr on propane) ran unit thru summer as well to heat hot water and pool burning poplar and whatever lo btu wood I had around.
 One change I would make if I had to do it again would be to feed the air introduction tubes through a bigger pipe sleeve so they wouldn't be in direct contact with the water jacket. Think this may help with creosote issue in the airtubes in higher idle times. As of late I have not had this issue with higher burn times and probably drier wood supply.
Any questions or specifics you may want to know about just ask and I will try to help you out

[slimjim]

Nice job with thinking before building Renoman, you hit the nail right on the head, let me ask you a question, starting from the idea on a napkin to where you are now, labor included how much do you think you have invested

[hondaracer2oo4]

Renoman, how about some pics of this beast?

[binfordw]

labor included how much do you think you have invested

Oh you never include labor!! 

[binfordw]

Can anyone elaborate on the importance of proper heat exchanger size? 

As for refractory, I will do some searching.  As long as I design the secondary chamber to allow access to change the target area out, I think that will take care of any concerns there.

I plan on modeling my boiler in CAD, and just CNC cutting the panel and parts from the model.

[Dragfluid]

"allow access to change the target area out"

Hey,,,,,,, how about putting the whole secondary on a slide out?  Just like an ash pan?

[renoman]

Nice job with thinking before building Renoman, you hit the nail right on the head, let me ask you a question, starting from the idea on a napkin to where you are now, labor included how much do you think you have invested

Well I guess if I would include labour I would probably have as much invested as a new unit. But that being said
I am the type of person who enjoys the challenge and really enjoy building stuff. Most of my days are spent either at work or at work in the shop working on different projects so I didn't track hours persay for expensing them but just as rough project time.
All said and done I have $9600 into all the materials to build the boiler, the slab (9' x 13" x 8"), the underground lines, the trench, the water hx, the furnace hx, sidearm in shop and the circ pumps. Also enclosed the boiler in a small enclosure plus some wood storage.
My payback should be fairly quick as my propane average use before was $4000 a yr.  May  have been $5000 or better this year with as cold as it has been!

[renoman]

Can anyone elaborate on the importance of proper heat exchanger size? 

Not sure what the engineering is on that exactly but I know you don t want to restrict your air flow back too much.
As the air moves through the chambers and around corners it naturally loses velocity so you would want enough tubes to allow the heat to travel thru easily enough but many tubes of smaller sizes increase surface area contact to the water jacket thus allowing maximum heat extraction. Mine has six 2" tubes off of the secondary chamber about 30" long and ten 2" tubes travelling horizontally 36" back to front and then 10 more front to back then exits out 6" stack. That gives a total of 75' of tube immersed in the water jacket to extract the heat from.
I run the boiler at 195 with 8* dif and when it is clean my stack temp 1" above where it exits the water jacket will be 240* so I think it is pretty much extracting every btu it can. On cold days I have icicles hanging off my chimney cap!!