I've built a lot of alternative energy projects over the years. See my web site at http://www.mdpub.com and my other instructables to see my home-built solar panels, wind turbine, improvised generator, and other projects. I've always wanted to build a wood or biomass gasifier too. Why? Well, the internal combustion engine is really an important part of our society and the basis of a lot of our transportation and portable power technology. It isn't going to be going away any time soon. I've mastered making my own electricity from the sun and wind, but that doesn't help my truck go down the road, power the lawn mower, or run my generator on cloudy, windless days. Those all have internal combustion engines, and they all need fuel to run. I finally decided it was time to master making my own fuel. Why pay the Arabs for it if I can make a working substitute myself?
So what is a biomass gasifier? Basically is a chemical reactor that converts wood, or other biomass substances, into a combustible gas that can be burned for heating, cooking, or for running an internal combustion engine. Gasifiers are an old, but generally overlooked alternative energy technology. Few people these days realize that gasifiers were used extensively by both sides during WWll to power cars, trucks and buses during fuel shortages. Gasifier technology rapidly evolved and matured during the war.
Gasification is achieved by partially combusting the biomass in the reactor, and using the heat generated to pyrolyse or thermally break down the rest of the material into volatile gasses. A well built gasifier will convert wood or other cellulosic biomass into the flammable gases Carbon Monoxide and Hydrogen.
My goals here were to build a gasifier using easy to obtain materials, that would run on readily available fuels, and would produce enough gas to at least run a small generator or other machine powered by an internal combustion engine. In this instructable I am presenting the finished product (so far) that has resulted from many months of experimentation and modification. To see the entire long and winding road I went down to get here, please visit the gasifier section of my web site at http://www.mdpub.com/gasifier/.
So what is a biomass gasifier? Basically is a chemical reactor that converts wood, or other biomass substances, into a combustible gas that can be burned for heating, cooking, or for running an internal combustion engine. Gasifiers are an old, but generally overlooked alternative energy technology. Few people these days realize that gasifiers were used extensively by both sides during WWll to power cars, trucks and buses during fuel shortages. Gasifier technology rapidly evolved and matured during the war.
Gasification is achieved by partially combusting the biomass in the reactor, and using the heat generated to pyrolyse or thermally break down the rest of the material into volatile gasses. A well built gasifier will convert wood or other cellulosic biomass into the flammable gases Carbon Monoxide and Hydrogen.
My goals here were to build a gasifier using easy to obtain materials, that would run on readily available fuels, and would produce enough gas to at least run a small generator or other machine powered by an internal combustion engine. In this instructable I am presenting the finished product (so far) that has resulted from many months of experimentation and modification. To see the entire long and winding road I went down to get here, please visit the gasifier section of my web site at http://www.mdpub.com/gasifier/.
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Signing UpStep 1: How Does The Gasifier Work?
There are no pretty pictures or informative diagrams in this step. This is the stuff you need to read before attempting to build this project. Please don't skip it.
A word of warning here. This project is dangerous. The operation of a biomass gasifier produces lots of heat, also lots of flammable and poisonous gases. Never operate the gasifier indoors. The gases produced are flammable and potentially explosive if allowed to accumulate in an enclosed space, like a building. Also, the Carbon Monoxide the gasifier produces is lethal! Only operate the gasifier outdoors and try to stay up wind of the unit when it is running. Treat the gas coming out of the gasifier with the same respect as you would for the natural gas that you may have piped into your house. It is just as potentially explosive and deadly.
As I said in step 1, a biomass gasifier is a chemical reactor that converts wood, or other biomass substances, into a combustible gas. The formula is simple. Biomass + Heat = Pyrolysis Byproducts. Pyrolysis is a fancy-pants word that chemists use to describe the process of heat breaking down big molecules into smaller ones. In the gasifier we want to break big biomass molecules (mainly cellulose) down into smaller ones like Hydrogen and Carbon Monoxide.
Where does the heat come from? We get heat by partially combusting some of the biomass with a limited supply of Oxygen. The heat produced by the combustion then drives the pyrolysis reaction. A well built reactor will also convert combustion byproducts like CO2 and water vapor into flammable CO and H2 by passing them over a bed of hot charcoal, left over from the partial combustion, where they will get reduced.
Thus the gasifier converts most of the mass of the wood (or other biomass feedstock) into flammable gases with only some ash and unburned charcoal (bio-char) residue. That is the theory anyway. This is an extreme over-simplification of how the gasifier really works. Wood and other biomass is made of incredibly complex macro-molecules like Cellulose and Lignin that break down into hundreds or thousands of different smaller molecules as the reaction proceeds. There are thousands of different complex chemical reactions going on inside the reactor. The overall result though, if the gasifier is working well, is lots of clean, flammable gas.
Ideally, the gasifier would break down biomass into nothing but Hydrogen and Carbon Monoxide. Here in the real world though, things rarely work ideally. The dirty (literally) little secret about biomass gasification is tar production. Above I said that the macro-molecules that make up biomass get broken down into smaller molecules. Some of those smaller molecules are still pretty big though. If the gasifier is working well, these big breakdown by-products will be further "cracked" into smaller molecules. If the gasifier isn't working so well, these big molecules will wind up in the gas being produced. They will condense out of the gas as a thick, sticky, black, semi-liquid that very closely resembles roofing or road tar, but is even stinkier. Even a well-built gasifier produces a small amount of tar. Most real-world applications (like engines) can't handle much, or even any, tar. My struggle to design and build a working biomass gasifier could actually be accurately described as an ongoing battle to reduce tar production. The first few iterations of this gasifier produced more tar than gas. The complete history of this design can be found on my web site at http://www.mdpub.com/gasifier/. Below is the most important of all chemical reactions a novice gasifier builder needs to know.
Biomass + Poorly Designed Gasifier = Tar!
I strongly recommend that anyone interested in gasifier technology do some research and read up on it. There is a lot more to this technology than I can present in an instructable.
A word of warning here. This project is dangerous. The operation of a biomass gasifier produces lots of heat, also lots of flammable and poisonous gases. Never operate the gasifier indoors. The gases produced are flammable and potentially explosive if allowed to accumulate in an enclosed space, like a building. Also, the Carbon Monoxide the gasifier produces is lethal! Only operate the gasifier outdoors and try to stay up wind of the unit when it is running. Treat the gas coming out of the gasifier with the same respect as you would for the natural gas that you may have piped into your house. It is just as potentially explosive and deadly.
As I said in step 1, a biomass gasifier is a chemical reactor that converts wood, or other biomass substances, into a combustible gas. The formula is simple. Biomass + Heat = Pyrolysis Byproducts. Pyrolysis is a fancy-pants word that chemists use to describe the process of heat breaking down big molecules into smaller ones. In the gasifier we want to break big biomass molecules (mainly cellulose) down into smaller ones like Hydrogen and Carbon Monoxide.
Where does the heat come from? We get heat by partially combusting some of the biomass with a limited supply of Oxygen. The heat produced by the combustion then drives the pyrolysis reaction. A well built reactor will also convert combustion byproducts like CO2 and water vapor into flammable CO and H2 by passing them over a bed of hot charcoal, left over from the partial combustion, where they will get reduced.
Thus the gasifier converts most of the mass of the wood (or other biomass feedstock) into flammable gases with only some ash and unburned charcoal (bio-char) residue. That is the theory anyway. This is an extreme over-simplification of how the gasifier really works. Wood and other biomass is made of incredibly complex macro-molecules like Cellulose and Lignin that break down into hundreds or thousands of different smaller molecules as the reaction proceeds. There are thousands of different complex chemical reactions going on inside the reactor. The overall result though, if the gasifier is working well, is lots of clean, flammable gas.
Ideally, the gasifier would break down biomass into nothing but Hydrogen and Carbon Monoxide. Here in the real world though, things rarely work ideally. The dirty (literally) little secret about biomass gasification is tar production. Above I said that the macro-molecules that make up biomass get broken down into smaller molecules. Some of those smaller molecules are still pretty big though. If the gasifier is working well, these big breakdown by-products will be further "cracked" into smaller molecules. If the gasifier isn't working so well, these big molecules will wind up in the gas being produced. They will condense out of the gas as a thick, sticky, black, semi-liquid that very closely resembles roofing or road tar, but is even stinkier. Even a well-built gasifier produces a small amount of tar. Most real-world applications (like engines) can't handle much, or even any, tar. My struggle to design and build a working biomass gasifier could actually be accurately described as an ongoing battle to reduce tar production. The first few iterations of this gasifier produced more tar than gas. The complete history of this design can be found on my web site at http://www.mdpub.com/gasifier/. Below is the most important of all chemical reactions a novice gasifier builder needs to know.
Biomass + Poorly Designed Gasifier = Tar!
I strongly recommend that anyone interested in gasifier technology do some research and read up on it. There is a lot more to this technology than I can present in an instructable.
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I am now on my way to attempting methanol creation from bio-gas which requires a fluid bed reactor, and from what I know now, these can be made and simplified just as easy as we can do with these wood gas burners.
Once the gas leaves the unit, you can further purify it by using:
- Filters: several can be placed along the gas process. I know of cyclone, water, fluid bed and fiberglass. ( sorry, only just heard that in the vid )
Clean the gas further by condensing it to a liquid, easier to separate by adding a simple condensing unit.
Peltier or Stirling modules for energy production off the burner.
Download a .pdf book you can google called: Wood Gas As Engine Fuel
It provides an extreme amount of info on our beloved burners. Hope any of this helps.
p.s - unfortunately I became a victim of lack of information and ended up in emergency from Carbon Monoxide poisoning. As you can guess, I stay clear of the smoke these days :(
Thanks again for your great work.
.
What are reasons to not do it like this?
A steam engine to drive a generator would run you 30k + . They are wonderfully efficient but not cheap.
A small steam engine will cost 30 - 40K , there is a reason for it.
They are incredible machines , the speed of an old steam powered wooden launch would amaze you. Internal combustion replaced steam because it was cheaper and safer , not because it was better.
The licences to run a steam engine cost more than the gasifier.
I was more hoping to stir up a little input from the engineers out there than you personally. Once again I would like to commend you on an excellent instructable. I can only hope to someday contribute something of such elegance.
for the creosote/tar, i have seen designs where the gas is percolated through a water reservoir. this would be much simpler than your spray design and potentially more manageable than a cyclone separator, as maintenance would largely consist of changing out the water regularly. of course, the more and smaller holes the gas goes through at the bottom of the percolator, and the more time it's in contact with the water the more effective it will be. you might consider a condenser down circuit from this to remove excess water.
as to the sulfur, the most common method i've seen is running the gas through a column full of steel wool. the steel bonds with the sulfur and provide a surface for it to crystallize, making little yellow florettes. there's a way to remove the sulfur from the steel wool and reuse it a few times before it rusts to bits, but i can't remember how to do that right now. i don't think it takes very much steel wool to remove a significant amount of sulfur but a longer column with more steel wool would probably be more effective and require maintenance less often.
as an added bonus, you might be able to find uses for the creosote and sulfur. they're both flammable and, thus, potentially usable as fuel. they have other uses as well.
The neat thing about gasifiers is that they can almost be as simple or complicated as you want them to be.
http://www.northerntool.com/shop/tools/NTESearch?storeId=6970&N=0&Ntk=All&Ntt=pellet+stoves&Nty=1&D=pellet+stoves&Ntx=mode+matchallpartial&Dx=mode+matchallpartial&cmnosearch=PPC&cm_ven=google_PPC&cm_cat=HeatersStoves&cm_pla=core&cm_ite=pellet%20stoves&mkwid=syIrp4MO6&pcrid=8759532911&mt=e
Also there are off the shelf usable parts for your gassifier......restricter plate and shaker etc.....
Corn ,in some years, goes currently for 643.00 cents per bushel/50lbs bag or better yet grow your own^_^ Gives you something to do with all that 'franken corn' {genetically modified}nobody wants to eat
In the 301s and 40's years, in Brazil has used a very similar system to feed the engines of transport trucks and tractors. You can see something on the links below
http://www.lorenzetti.com.br/historia.asp
http://www.nobresdogrid.com.br/site/images/stories/Nobres_do_Grid/Coluna_Tecnica/Gasogenio/gasogenio_viacao_garcia.jpg
Excuse me my Inglish,ist´s so poor
I think it was used a lot during the 2WW
If you have more infs about to incres the performance ( energy rendiment) PLEASE keep up to date
Regars
Here is the link: http://www.wired.com/magazine/2012/01/ff_trashblaster/
Thanks for sharing, this definitely wants me to look more into this form of trash removal.
I have seen this on your website some time last year. Glad to see it on instructables. I have been debating a gasifier build of my own. It's on the end of the "to do list" if you know what I mean. A mate of mine debated a simple shaker by mounting a motor with an offset flywhel to the outside of the main drum of the gasifier and setting it on a timer. That way its external and easy to get to.