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- What is your experience with gasification?
- None yet; former millwright, Maine State Masters license in solid fuel, Licensed solar installer, degree in heating/air conditioning.
Ron Harwood's Blog
Great info!
Hey, thanks John/Rush- great info, very pertinent. I need to spend some time at Ben's page, to get myself updated. I agree, the physical size of the tank holding the material seems to be a little arbitrary; however, based on the horsepower of the motor being operated, the size of the 'orifice' at the combustion chamber will vary, so bridging of the material feeding it must be avoided. Otherwise, the simple amount of material held in the tank may just represent how often you are willing to refill… Continue
Posted on March 8, 2009 at 2:40pm —
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There is definately a relationship between the size of the motor you are trying to run and the size of the orifice in the chamber. It seems like the bridging effect could be drastically different depending on the size and shape of the feed stock being used. That is why you need to give it a jiggle every few minutes to get fuel to fall down into it. With the imbert design it seems like the height of the fuel stock waiting to fall into the chamber is less relavent than with the stratified FEMA style design where the air for the reaction needs to permeate down through the feed stock, where as with the imbert design the air tubes bring the air directly to the reaction area. I don't yet have a good feel for how long of a run time you can get with a certain feed stock volume.
I actually lit mine for the first time a few days ago. I was so excited to lite if off that I tried to use an old shop vac to create the downdraft. I barely got the thing lit and smoked the the vac in about 2 seconds - bad idea.... I was going to try to find some kind of a steel impeller and housing blower to create vacuum, but Ben has turned me onto the idea of using an ejector instead. It makes so much more sense to me and avoids sucking superheated gas into a rotating impeller - which can't be good for it. I cobbled together a working ejector with some pieces of pipe and was able to get my gasifier to burn through a load of wood chunks. The problem with the ejector is that it introduces fresh air to the output gas stream and changes the fuel/air mixture. So with my hodge podge 5 minute ejector I am getting too much air to create a combustible mixture to flare off. I need to fine-tune the ejector design to get enough suction on the gasifier, but limit the amount of fresh air being introduced. There are some guys on you tube that are using a 1-1/2" pipe tee and supposedly a 1/4" air nozzle with about .5 psi pressure on it ( must be the blow side of a shop vac). That arrangement seems to be a good enough match of fresh air and ejector parameters to create a combustible mixture at the output of the ejector. If you notice on Ben's new vids of starting up Woody, he has incorporated a similiar type design and done away with the blower. Seems like an upgrade to me....
Take care
Rush
I was trying to send this comment back to you, but somehow I ended up commenting to myself. Anyway, I cut and pasted it here to your blog......
Ben has made some recent updates to the Imbert design page that is helpful for sizing the hearth and nozzle. He also added a note about how much gas per hour is needed per horse power of engine you want to run. 2 cubic meters per horse power per hour ( I assume this is at atmospheric pressure (~14.7psi).
So in my case, if I want to run a 10 Hp motor, I will need 20 cubic meters per hour. So as for gas storage, we can work out how big a tank we need to run for a specified period of time. According to my calculations, 20 cubic meters corresponds to 5283 gallons of storage for 1 hour of run time!!!. If you were to compress it ten fold to about 147 psi, you could bring the storage volume down by a factor of 10, which is about 528 gallons (still quite a big tank for 1 hour of run time). At least now I have a feel for how much volume is needed to run a 10 hp motor. For me it seems impractical to achieve the kind of storage needed to run a motor for any appreciable amount of time.
How big is the motor on your chipper?
I got an answer from Ben the other day regarding use of syngas in a propone or nat gas burner. According to him, he has heard of it being done in the past, but he is not currently doing it and he doesn't know of anyone first hand that is currently doing.
I would imagine that nozzle would need to seriously hogged out to allow the amount of gas flow through it, and even then I would imagine that the overall BTU output of the burner would be significantly derated.
As for my build, I am going to use the published Imbert design parameters for the smallest gasifier on the list.
I wonder if the height of the fuel tank is really that important. By looking at the various sizes of gasifiers and the height of the tank for each, it almost seems like abitrary changes in tank height that simply get larger as the size of the gasifier increases. I think a larger tank height would yield a longer run time of the gasifier.
Take care!!!
John
do you have any pics of your project so far? I am finding it hard to settle on a specific detailed design for hearth and grate system that will generate enough gas to run a 10hp gas motor. It seems like the grate system is where alot of reliability problems could occur.
You should check out the Monorator for burning your chips wet/green.
http://victorygasworks.ning.com/profiles/blogs/monorator-1
Another tribute to Ben -
This thing is amazing - it just pulls the water out.
Not alot of details on the specifics of construction - Perhaps more research on the Monorator would yield more.
As for storage anyway you slice it, it is not going to be easy. Even under high pressure the energy density of the gas is so low that a large propane tank won't hold much energy.
It seems like for use in motors you need to burn as you go. But for home heating, I would like to see a large gasifer batch, run the gas in a propane/nat gas boiler to heat water and store the heat in a large insulated tank. That way you could use some solar collectors to help heat the large tank too for shoulder season heat and year round domestic HW.
I noticed you are a solar installer - what is your favorite solar collector?
Noticed you are from Maine. Where abouts? Would be interested in seeing your gasifier when you it get it going. I am building my first gasifier now and should have it ready to light in a few weeks. It would be great to have a fellow gasifier to bounce ideas off.
Seems like you should be able to get your chipper to run off your wood chips, but I think the might need to be dried - None the less you should be able to run off chips from a previous day and not use diesel.