[Gasification] Gasification of briquettes

[jim mason]

On Sat, Feb 12, 2011 at 6:06 AM, john blount <johnblount448 at hotmail.com> wrote:
> I have a gasifier (Fluidyne design) that works excellently with two inch
> chunks of wood, but when we switched to burning briquettes (compressed
> shavings and sawdust) everything changed so much that we no longer can
> sustain gas production, plus have extreme amounts of slipped char and
> cyclone particulates.
> Has anyone experience in gasifying such fuel?
> The swelling from steam in the hopper causes bridging that did not occur
> with the chunks, but that should be easily overcome, perhaps with a
> monorator hopper?


john, this is a hard problem, but there are some partial fixes that
might get things to tolerable.  it can likely be solved without a 50k
extruder or giving up.

the monorator will still keep your hopper with steam in it, so decomp
will still start.  not much win here.

the biggest fix would be to move your hopper off the top of your
reactor.  go to an L type arrangement, with an auger, chain drag, or
belt between them.  this gets the raw fuel off the top of the heat,
and keeps the steam out of the reactor.  this is somewhat like a
pellet stove, taht only feeds the compressed pellet fuel in as it is
burned.  if a pellet stove was straight gravity feed from an overhead
hopper, they'd have the same problem you currently have.

this "hopper off the reactor" architecture also prevents channels from
the hopper to the coals, which is how one gets puff/explosions. once
you get the hopper off the reactor the puff problem goes away.
however, now you have a fuel transport problem, which is its own set
of annoyances.

the other two possible solutions are to stay with the over reactor
hopper, but try to purge the steam.  you can do this the russian
method with a fan to pull it off, or the leak method where you all in
a controlled amount of air into the hopper, which is pulled through
tot he reactor, pulling the steam with it.  this is the partial
stratified downdraft scheme.  or the tar flare idea, which i think you
are running anyways, so maybe this isn't enough.

of course not shutting down with briquettes still inside is helpful.
the bad decomp happens when they site in the steam during shutdown.
you are likely already doing this.

or, you might consider adding a binder to the briquetting process.
latex paint is seemingly a cheap and safe option.  richard stanley of
legacy foundation will have many others.

still, of all these, i think the offsetting of the hopper from the top
of the reactor will do the most.  if you can keep the briquettes in
good form until the hearth, they will behave much better in the
hearth.  but then again, if not lignin bonded, they might still decomp
there.

isn't gasification fun?

what happened to the high resin block fuels?

jim







> Thanks,
> John Blount
>
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