My homemade gasifier

[Mellowyelloe]

Hi fellow members. This is my first post. I joined this community to share my boiler project with everyone in hopes maybe others can learn and hopefully I can learn from others.

Last summer I started building my boiler because I was tired of the inefficiency of my insert in my fireplace. Plus the mess of bringing the wood inside and the ashes.... I'm sure you all know how it is.

I started the research found our about gasification and decided to have an adventure.

Anyways I've got the firebox finished and working great, I believe at least(there's no smoke at least).

I have pictures of the build if any wants to see them. I will post a few links to videos of it running.

First run after making the airflow to the upper chamber.

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Second run start-up.

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Second run after full gasification started.

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Oh yeah, the upper chamber is an old hot water heater. Lower chamber is three freon bottles welded together. The outer water jacket is a 300 gallon disel fuel tank. I know none of this is conducive to rust inhibition dut this is just a test. My next booiler will be stainless or aluminum.

Any suggestions comments or ideas would be great.

 

[maple1]

Is your lower chamber insulated? Refractory down there?

 

[peakbagger]

If you haven't looked over the Dick Hill Gasifier designs it would be worth looking

Nothing really come close except for the later refinements by Jetstream and Dumont.

Here is link http://www.hotandcold.tv/stick_wood_furnace.html

 

[stee6043]

Do you plan to run this outside, exposed or perhaps in a shed of some sort? Will be be insulating the bejesus out of that thing?

One thought/suggestion - you're going to need access to your exhaust tubes. That's a tight turn coming out of your lower chamber and those buggers are going to have a tendency to collect stuff. Best case is fly-ash. Worst case is creasote.

Cool project. Someone else should be along shortly to ask about how you plan to store/move/manage the hot water

 

[Mellowyelloe]

I don't have any refractory in the lower or upper. I'm Thinking once it's incased in water I will need some insulation.

I plan on having it insulated in the corner of my garage. On the top where all the pipes meet I'm building a box that will have a door so I can use the flexible rods and round brush for pellet stoves and I should be able to go from the bottom also. Any creosote build up will only be on start up and will burn up throughout the cycle.

As far as water movement I have a hot water pump for it and a heat exchanger in my air handler. For domestic hot water I'm going to wrap the top with pex and let my he supply run through it. Then my tankless won't be using nearly as much energy in the winter, if any.

 

[maple1]

From my experience, once you get a bit of creosote in your tubes, you will need to brush or scrape to remove it. A good hot fire might get rid of some in the lower part next to the secondary chamber but it won't get rid of stuff higher up.

 

[Mellowyelloe]

I understand that. Which gasifiers resistance creosote build up due to fully burning the wood and gases, is one of the main reason for me choosing to build a gasifier.

I'm new to this still so someone please correct me if I'm wrong.

 

[maple1]

No I think you're on track. Pretty well all of any creosote build up you get will be from startup, before it gets up to good gasifying conditions. Without the secondary chamber being insulated, that will likely take quite a bit longer, and will likely give a narrower window in which full gasification will occur. Very much especially with a water jacket around it - that will really damper things. I get very little buildup with mine, almost 100% fly ash. But the odd time I get a slow startup or gasification gets interrupted say by bridging, it will leave some deposit on the tops of my tubes that I see next time I brush. It comes off easy though likely since there was fly ash under it. Not sure how long it takes you to get decent gasification going so far, but with mine its almost right away - usually 5 minutes at most.

 

[stee6043]

I understand that. Which gasifiers resistance creosote build up due to fully burning the wood and gases, is one of the main reason for me choosing to build a gasifier.

I'm new to this still so someone please correct me if I'm wrong.

The lack of creasote is as much a function of the wood you burn as it is the type of boiler. With limited access to your tubes you're going to need to be uber picky about your wood. 2 years+ on the pile, only hardwood, only the good stuff.

How will you regulate the fan speed compared to water temp? Another way you'll get build up in your tubes is if your water temps hover near the high range consistently creating extended periods of idle.

 

[Mellowyelloe]

Yes maple I agree once once incased in water the startup will probably be much slower I just wanted to see if I could get it to work before I spent a bunch of extra time and materials on it. Everything but the outer fuel tank has been free so far.

Stee, I guess I don't see how tube design has anything to do with what wood I need to use. And as far as hovering at high temps, figure that would be a learning curve as to how much wood to burn to get x amount of water temp increase.

I will have a high temp shut off however. Which if it shuts off mid burn I know that would cause some creosote build up also.

 

[stee6043]

Stee, I guess I don't see how tube design has anything to do with what wood I need to use.

I'm not an expert, to be sure. But I'd be willing to bet that you could clog those tubes with just a few loads of punky wood. That's all...

 

[maple1]

Stee, I guess I don't see how tube design has anything to do with what wood I need to use.

If your wood isn't good, your tubes will get dirtier easier. In which case, tube & boiler design to allow for easy frequent cleaning will come into play & be of more importance.

And as far as hovering at high temps, figure that would be a learning curve as to how much wood to burn to get x amount of water temp increase. I will have a high temp shut off however. Which if it shuts off mid burn I know that would cause some creosote build up also.

That would likely be where most of your buildup will happen - far far more than the startup stuff. Return temperature protection (keeping return above 140°) is also important - have you considered that as well?

 

[salecker]

I am picky about my wood,and have storage.
I should clean my boiler tubes more,and probably will now that i can do it with a lot more ease with tools that i have made for the job.
Now i clean them in the fall before startup,and usually twice during the burn season.At first it was a 4-5 hr job and now i have it down to about half that.
I have seen the result of burning sub-par wood.Burn crappy wood and you will be cleaning your flue tubes,or dumping BTU's into the sky.

 

[Mellowyelloe]

Yes I understand, you burn junk you get junk. I just don't see how a tight bend is going to cause creosote to appear. I also understand that IF it happens it will be more difficult to clean out. Ideally this boiler will only be in operation for one season, if even that.

That would likely be where most of your buildup will happen - far far more than the startup stuff. Return temperature protection (keeping return above 140°) is also important - have you considered that as well?

I figured if I put the inlet from the top and ran a pipe to the bottom would help increase the return temp.

However, I'm really toying with the idea of making a furnace out of it. Figured I could insulate the bejesus out of both chambers with refractory. I'd have to lower the air flow. I'm not sure but I think I'd have to put a constrictor plate in the connecting tube. See if I can get gasification to occur slow enough.

Any thoughts on that. Anyone every seen a downdraft gasification furnace?

 

[Fred61]

Burning super dry wood over the years and burning one hot fire per day without idling has always kept creosote from depositing in the tubes but several times I have had a cement like deposit on the tube surfaces. Most likely from the sugars in the wood. It probably won't plug the tubes but will severely affect the heat transfer. Having said that, I would build the tubes so they are accessible with a wire brush.

 

[maple1]

Yes I understand, you burn junk you get junk. I just don't see how a tight bend is going to cause creosote to appear.

That isn't what was said. I believe the point was, bad wood will make increased creosote to appear. I don't think I read anything about bends making creosote.

If the tubes aren't designed for quick easy cleaning - then that usually becomes a real big problem.

It's very important to be able to easily clean tubes regardless - even fly ash deposit can reduce heat transfer efficiency. Let alone creosote.