I have a problem with separating spheres(rather soft particles, around
1mm diameter) that are mixed with water. When these spheres do what
they need to do, they become elongated, like a sausage, but this
sausage's diameter is the same as the original sphere so meshes of
different kinds have not worked as the sausages squeeze through. I
need to separate the spheres from the sausages in an effective and
simple way. Density of water, sausages and spheres is basically the
same. Method should be very very cheap and useful for bulk (tons) amounts. |
Request for Question Clarification by
pafalafa-ga
on
20 Nov 2003 07:26 PST
How fungible are the spheres and sausages?
Separating them one from the other may not be possible if the spheres
are continually changing into sausages or vice versa -- removing some
sausages might just shift the equilibrium, causing the remaining
spheres to change into new sausages.
Are there standard separation methods that you have tried without
success? I'm thinking settling, centrifuge, filtering, coagulation,
etc.
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Request for Question Clarification by
hedgie-ga
on
01 Dec 2003 04:42 PST
You did not give us enough information to work with.
Do the particles have same volume, just changing shape?
Same small cross-section and elongation indicates they did grow?
What are their electophoretical properties
are they protein, PVC, ..
are they conductive,
would you consider evaporation as a feasible step ...
are they all and always same or is there a distibution?
Question like this would benefit from having a page(s) somewhere
with photos, measurements, descriptions of what was done, was was
already tried, what you already know about the problem..
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Clarification of Question by
taca-ga
on
02 Dec 2003 11:25 PST
Sorry if I was not clear. LEt me try to clarify your questions.
Spheres change into sausages permanently. Sausages never revert to
spheres and must be discarded. The growth mechanism is agglomeration -
2 or 3 spheres merge, irreversibly, into a 'sausage'. Since both are
the same density (they are really the same material) we've not tried
settling or centrifuging, we think there would be no driving force for
them to separate. We've tried filtering through wire mesh but a mesh
size big enough for the spheres is also big enough for a lot of
sausages to squeeze through. We've tried two meshes separated by a
short distance and with the holes of one not precisely aligned with
the second. The idea was to prevent sausages from escaping. It was
modelately successful, but some still got through and the filter
fouled permanently in no time. We've not considered evaporation
because that would leave us with dry spheres and sausages, but still
mixed up (also, they don't like being dehydrated, they can break).
Hope this is useful. Promise to clarify, if still questions, more
quickly next time.
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Request for Question Clarification by
pafalafa-ga
on
02 Dec 2003 11:49 PST
Hmmm...that's a tricky one. Have you considered dissolved air
flotation? The tiny air bubbles formed during DAF would adhere to the
particles, and since the spheres and sausages have different surface
area/volume ratios, I expect they would float differentially and could
be separated that way.
There's also an electromagnetic option by applying a charge to the
particles (as is done in particle counting technologies) but I've
never seen this applied to high-volume separations. Could be a
possible option, though.
Also, have you looked into options for preventing agglomeration in the
first place, probably with an appropriate additive (which could be as
simple and as cheap as corn starch?). Seems worth exploring.
Let me know what you think.
pafalafa-ga
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Clarification of Question by
taca-ga
on
03 Dec 2003 09:47 PST
Agglomeration prevention is not possible. it is long to explain, but
spheres ARE suppossed to turn into sausages. The flotation idea is
interesting. I reckon we would need a very small bubble size wrt
sphere/sausage size, to get a significant buoyancy effect from the
relatively small area/volume ratio difference. I am not sure how to
make such small bubbles but will give it a try with sonic transducers.
If that works, you get the question prize. Any further ideas in case
it does not? Any guidance on how to make your idea of the bubble
separation work?
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Request for Question Clarification by
pafalafa-ga
on
03 Dec 2003 10:01 PST
DAF is a well-established technique, widely used in wastewater
treatement to remove particles. I haven't seen it used in the type of
application you are looking for, but it seems as if it could be. You
can get a quick, decent overview of DAF here, but keep in mind the
site focuses on wastewater treatment, so it may look pretty different
from what you're after:
http://www.panamenv.com/dissolved-air-flotation-theory.html
You may want to contact a DAF company to get their opinion of the
possibilities here.
Let me know how things work out.
pafalafa-ga
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Request for Question Clarification by
pafalafa-ga
on
03 Dec 2003 20:04 PST
Actually, on further reflection, I'm beginning to have some serious
doubts about dissolved air flotation as a separation technique. I
think that one of the key dynamics involved in DAF is flocculation --
the individual particles are electromagnetically drawn together into
minute clumps that float to the surface.
If that's so, then the flocculation will defeat any attempts at
separating sausages and spheres, I'm afraid.
I'll keep thinking about this one, and let you know if anything else turns up.
pafalafa-ga
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