Hi Jim and Colleagues,
This is certainly a rare glimpse of the past, even if it is glamorised just
a tad.
http://www.youtube.com/user/bioenergyken
there are some interesting things to see in the video. in particular,
between 2 and 3 minutes, there is a quick shot of how the imbert did
its grate shaking. bear and i are currently rather interested in this
question and doing lots of testing to characterize the impacts of
different shaking mode types and different grate hole sizes.
In my visits to Germany where I had a chance to talk to old men users, the
shaker was important for start-up to have fresh porous char in the reduction
zone, and to refresh this grate char bed support on each refilling.
as we all know, bell packing is a major challenge for long untended
running. needing to poke a rod down the rig every once in awhile is
unacceptable for untended genset operation. expert operators of car
rigs tend to do this regularly, and don't think much of it. for a
newbie or a regular run situation, you need to eliminate the knowledge
dependency that only the expert has so they know when and why to do
this.
The Imbert design, and any other that draws the gas up around the sides, is
prone to plugging in the central core, and channelling down the sides of the
reduction zone bed as the gas takes the shortest route out towards the
source of suction. A pyramid of solidified char and fines form on the grate
quickly after start-up, then all the gas forces it's way out down the sides
often resulting in channels.
the imbert apparently had the side shake design via a pivot point
going through a gimble ball. this is a mode i was playing with in the
phillipines given challenging fuel there. now we're trying to
formalize the performance of this vs vibrator, vs in/out shake vs
rotary. oddly, we're finding up and down motion to potentially be more
effective than side to side or rotary motion. i thought such would
contribute to packing above. but so far it seems to do the opposite.
The up and down shake we have used since 1977, but the issue of any shaking
is that it disturbs the char evolution right through the bed from top to
bottom. Any shake should only be used to clear a stray stone or clinker, as
actual bed disturbance can results in a total loss of CO2 reduction., and of
course a slug of tar coming through. Engine vibration
is good, but can cause packing of the bed, if the motion is vertical rather
than horizontal. Our experience has shown over many trials of fuels, that
shaking is not going to give you a good quality gas with any high ash fuel
that needs shaking to keep the gas flowing.
Hope this is of some assistance,
Doug Williams,
Fluidyne Gasification.
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