[Gasification] Bob's system, and general comments about making gas

[drew]

Hi Rex,

I don't have a lot of time these days to post, but would like the list 
to get back to gas, as opposed to the hot air we have seen so much of.

    I think their are a number of ways this could be accomplished.   I 
have a process in mind I want to try out before I discuss it, but let's 
start with Bob's suggestion.   Using an auger to drop pellets into a 
reaction chamber.    Bob didn't get into the details of his suggestion, 
so I have used my imagination to flesh it out.   If the list makes 
enough suggestions perhaps I will even put one together, though these 
days I don't feel like I have much time, in a month or two who knows.

    If  we configure say a 24" tall piece of 2" pipe, with a 90 elbow at 
the top, and a pellet auger and fuel bin attached to the upper elbow.  
The auger and fuel bin can act as air dams for the upper end, (this 
would require a sensor to monitor a minimum bin level for safety).   A 
small amount of pilot air can be forced into the pipe for startup, with 
a check valve allowing unlimited air into the chamber on demand from 
engine vacuum.   The vertical pipe could have a long rod or pipe passing 
through a gland (cool enough here for tight fit) at the upper end of the 
tube with a mechanical ossolator that would turn on as demanded by the 
program (perhaps time delimited, or gas volume/rate, or perhaps 
constantly for a mechanically fluidized bed).     This rod might be a 
good place to have a thermocouple or two for monitoring bed temp, and 
perhaps fuel stack height, to control fuel feed,  Perhaps the air feed 
could happen through this tube to cool the pipe and inject the air lower 
into the fuel stack, or secondary air further down the stack?   At the 
bottom of the tube a simple elbow with a sliding collar could allow the 
char to be forced out, with the sliding collar allowing for adjustment 
of pressure required to force the char (semi fluidized by oss) around 
the corner.  It is interesting to me that the idea of 2 stage air 
introduction is so common place in stoves, and yet so rare in 
gasifiers.   It seems like the tar content of gas could possibly be 
reduced by extending the "hot zone" in a reduction tube and adding a 
tiny bit of secondary air to boost the temp for cracking.   At the lower 
end of the tube a second elbow could be added, this by the use of a 
sliding sleeve, or a few different length pipes could allow for char to 
exit the bottom end of the pipe, with the exit rate being determined by 
the ossolation and the length of the horizontal exit pipe.    This could 
end in a large bin that the gas is collected from, and that stores the 
char to be cleaned out when the setup is not operating.  

    Perhaps if people want to make contributions to the list, they can 
criticize/suggest changes to this idea, rather than hopping on their off 
topic horses and posting irrelevant to list crap.   Remember taking 
seriously anybody (read this as "replying to the list") who posts 
ridiculous stuff only gives them a soap box, reply to them directly,  I 
bet they will shut up much faster than if you reply to the list.

Always full of hot air,,
Drew

Zietsman, Rex wrote:
> >From an automation point of view, I agree that gravity feeding is
> madness due to the bridging likelihood: 
most especially when you use any type of mixed size fuel, or fuel like 
pellets that can expand rapidly when heated.
> you cannot afford not to tend to
> the gasifier all day. So, how does one control a gasifier? This is not a
> trivial question. Let me put it this way: let us say you are off grid
> and run a power generation system that must deliver power in a manner
> similar to an on grid system ie you can switch on equipment or power
> using devices (fridges come on automatically) and need to balance the
> power requirement with an engine. 
It seems to me that maintaining a full reduction tube, is the control 
required.   As the fuel stack height in the reduction tube declines, 
perhaps as measured by a feather switch or ?? more fuel is added.   The 
rest seems like standard imbert technology?   The nice thing it seems to 
me is that coarse mixed chips would be usable with a bit tougher auger 
than a pellet stove.  Once carbonized the chips would break and flow 
much easier I think?

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