3 replies to this topic

[jimmason]

Greg Manning in Canada has built the most impressive DIY wood chipper and sorter i've seen to date.  Here's his photoset on the woodgas forum which shows the set up. http://groups.yahoo....ount=20&dir=asc  Maybe Greg might pass through here at some point and comment on his most impressive work.

Greg's setup is based on the common low cost chinese disk chipper, and a rotating mesh cylinder to size separate the resulting chips.  These chinese disk chippers are available for around $1200 new and are commonly driven off tractor pto's or 20hp and above engines.  A disk chipper will produce a more chunky chip than a drum chipper.  Drum chipper make long slice chips which will not work in a downdraft.  Common garden scale disk chippers, like the Troybuilt chippers, will not work.  They produce more of a shredder fuel, not of adequate chunkiness.

We all need to come up with some "known to work" fuel preparation methods.   The varied experiences people have with the GEK and other gasifiers on first run follows directly from the specifics of their fuel and preparations of it.  Thus we need to have clear and easy solutions to offer here.

jim

[jimmason]

here's a picture from greg manning of what good screened wood chip fuel looks like.  this is about the best you can get with a disk chipper.  fortunately, it is good enough.  this is what we typically run in the gek and power pallet these days.

[treeclimber]

Hi I am a newbie to gasification but very enthrawled. I have owned and operated a vermeer 12 inch wood chipper for the past ten years. (I wish I would have of been pumping power into the grid and getting paid all this time) And I know a little about chips. There seem to be a few things that will effect chip size and what may work on one chipper may not on another.
The biggest thing for my chipper (80 hp 4 cylinder cummins diesel drum) is blade sharpness. As soon as blades get a little dull the chips get longer.

Next wood be the size of the log I am trying to chip. If the drum slows a little due to it having to work harder it starts to cut/smash its way through and chips get longer

Next would be size of the timber being chipped.
It cant be too fine or it just get sucked through the machine practicallly uncut and come out as a stick on the other end, also if you are chipping chunks of wood instead of long branches (which are held by an infeed roller or have ineria by virtue of there weight), there is nothing holding the wood as it is being cut so again the blade tends to cut /smash through instead of slicing (Have you ever tried to whittle a piece of wood without holding it in one hand while slicing with the other? I doesn't work)

The next big factor  is "Tree Species" Trees have variable density and physical properties that not only relate to species but also to where they have grown and in what conditions but certain tree species lend themselves better to producing uniform chip sizes Deodar Cedar is excellant through my chipper and it seems to be quite waxy so I would expect it would feed quite well.


I would recommend that if you are chipping and your chips are too long
it is possible to wood is too hard and needs to be fed into the machine slower, the same goes for larger branches if the motor is working harder this means the blades are now hitting the wood with less velosity and thus not cutting as effectively. Simple really

Having a constant large supply of mulch always available I wish to investigate how much money I can make putting power into the grid.

This a great forum. I was/still am a biodieseler and built a 1200litre batch processer but my commercial scale fat supply dried up. I cant believe wod gas never occurred to me. There must only be room in my brain for one alternative energy at a time.... duh!

[jimmason]

treeclimber said:

Hi I am a newbie to gasification but very enthrawled.

This a great forum. I was/still am a biodieseler and built a 1200litre batch processer but my commercial scale fat supply dried up. I cant believe wod gas never occurred to me. There must only be room in my brain for one alternative energy at a time.... duh!

hi treeclimber.

yes, most of us arrive at wood gas after a tour through biodiesel.  at some point in the veg oil war you realize that there is not a great deal of waste veg oil to be had in the world.  that most waste HCs are solid.

once you realize that all the biomass lying around us is actually fuel, just in the wrong state, the potentials for meaningful alt fuels expand exponentially.  one's interest in biodiesel begins to fade about that point (and beware of what follows).

the problem of course is the transition from solid biomass to gaseous fuels is not a no brainer.  it is harder than biodiesel to start, and is less forgiving to error in the engine.  but it is solvable.  i continue to be amazed how many routes of fixing have been ignored to date.  we're trying to fix that as fast as we can, and showing that it can be done, to regular use ends.

as for woodchips, you didn't mention the biggest determinant of chip shape-- chipper type.  in general i've found drum chippers to make a much longer and thinner chip.  i've never seen a product out of them that will work in a regular downdraft gasifier.

a disk chipper on the other hand can produce something that is tolerable.  not fabulous, not perfect, but good enough to work with.  thus most of our work has been to get the gasifier internals optimized for working with this reasonably accessible fuel.

requiring a laimet type spiral chipper makes the bar for gasification too high to be of much relevance.  

gasifiers in wwII only really worked because the fuel was purpose made and perfectly controlled into proper shaped chunks.  without this fuel control the gasifiers would have all the problems newbies currently have.  but requiring such a fuel is usually too high a bar for contemporary users.  

yes, some of the more zealous among us hand cut small branches to perfect cylindrical chunks.  but such a solution can't scale very well.  regular wood chips seem more doable for general use.  regular wood chips are everywhere.

jim