jsc
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Recommendations for drying muds/precipitates?
Hi, looking for suggestions on evaporating precipitates to dryness. I am evaporating masses having several kilograms, perhaps two gallons of mud at a
time. I would like to avoid heavy heat use both because of the energy expense and also some precipitates may be heat sensitive.
I know there is this thing called a rotovap, but it does distillation and stuff which is not needed for what I am doing. I just need to dry out a
precipitate.
I presume there is some thing like a rotary evaporator or something like that. Also, I think there are venturi-like devices. Like I know some chemical
plants use a venturi of some kind to dry powders.
There are also these things called centrifugal dewaterers, but I think they just get you down to a thick mud, they don't actually dry the stuff.
Another idea is maybe there is some contraption you can put inside of a dessicator like an archimedean screw that slowly sifts the material.
(Obviously you can't just stick the mud in a dessicator because only the surface gets dry.)
I have searched Google Patents, haven't really found anything.
Thanks for suggestions.
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Magpie
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I presume that a large (or several) Buchner funnel(s) would not be sufficient?
Here's a page that might give you some ideas:
http://www.charles-thompson.co.uk/filter.html
Here's a document that covers industrial dryers:
http://userpages.umbc.edu/~dfrey1/ench445/apv_dryer.pdf
If you want to dry several kg at a time perhaps a small vacuum pan dryer would do the job.
How much of the construction can you do yourself, ie, metal working, welding, pipe fitting, instrumentation, electrical, etc?
How much time and money are you willing to spend on this dryer?
[Edited on 20-11-2011 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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Panache
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To get the water out you'll need to either pass the mud through a filter that selectively grabs everything but the water, this type of device,
depending on it sophisication will also pass species dissolved in the water.
The alternate route is to allow the water to evaporate or boil off, here however, again depending upon sophistication, volatile non water species
could be lost.
What do you want to do?
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Mr. Wizard
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If you are not in a big hurry, and want a very low tech method, just put the material in wide mouth containers and cover the opening with a piece of
paper towel secured by a rubber band or string. For larger 5gal/20 L buckets you might use a newspaper or a tight cloth. It is slow, but it does work.
The paper keeps dust out of your 'mud' over the weeks it may take to dry out. Obviously humidity and temperature factor in. I used this when growing
crystals from water solutions many years ago, and it has the advantage of keeping out dust, and slowing the evaporation which makes for more uniform
or symmetrical crystals. The disadvantage is sometimes stuff creeps up the inside of the containers.
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jsc
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Thanks for the links.
Letting it sit does not work. I had one mud sitting literally for months and below the surface it was just as wet as when it started. Sitting only
works for crystals and stuff like that, not precipitated mud.
After doing a lot of research I think what I kind of need is a laboratory spin dryer. Unfortunately they cost $3000.
Funnels with filter paper do not work because you can't suck the water out of bucket of mud.
I have been drying with an old fashion method called steam drying which works but uses a lot of energy. Basically you are boiling water for 12 hours
straight to dry maybe a kilogram or so of powder. So, maybe $2.50 cost plus the time annoyance.
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Sedit
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You get an unglazed ceramic plate and use that for drying muds. Easy as pie.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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blogfast25
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A bit harder when it's two gallons of stuff?
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jsc
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Methods like hot plates and microwaves result in spattering and other bad, inefficient things.
I have been learning more about spray drying which has the advantage of being energy efficient. However, some reports say that it can result in
dustiness where you end up with particles of different size, some very small.
One nice thing about the steam drying is that it results in very nice, fluffy product. If spray drying would result in dustiness, then it is $3000
wasted. Rather spend the money steam drying.
Following on from an above post, another option is a "agitated vacuum pan". The problem with this thing is that once again it is $3000 piece of
equipment and it is even more bulky and less efficient than a spray dryer. On the other hand it may result in better quality.
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fledarmus
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How about freeze drying? Rotate a heavy-walled cylinder (or several) full of mud in a dry-ice/acetone bath until the mud is frozen solid, then subject
it to a hard vacuum until all the water has sublimed.
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watson.fawkes
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This sounds fairly practical, actually. Dewatering a slurry
through a porous plate is essentially how slip casting works. The key is that the diffusion rate depends a lot on the layer thickness. So just make
sure there are thin layers of precipitate at any time. Getting surface area isn't even expensive. Use unglazed ceramic tile, sometimes called in trade
"quarry tile". Build up a dam around the perimeter with wood and seal the joint with caulk. Total materials cost in the US would be 2-3 dollars per
square foot of surface area. Then make up a plenum with the plates on top and some lumber for the sides. Blow air through the plenum to drive
evaporation on the bottom surface of the plate. Surface tension gradients through the porous ceramic and the mud will drive the drying process.
As an alternate porous material, you could just make a large flat surface up out of slip casting plaster. In the US, the ordinary product is US Gypsum
No. 1 Pottery Plaster, which should be available at any ceramics supplier. If you can't find that, plaster of paris works, but not quite as well. This
technique would require more construction (heavier, needs reinforcement) but work better for larger batches. With a single bag of plaster you could
make a plate that could easily absorb two gallons of water. The plate would have to dry out between batch runs, though.
This should work assuming your particle sizes aren't really tiny. If they are, it should still work with ever thinner layers and more batches. It will
also compact all the particles and you may need to mill the result afterwards to your desired particle size.
Regardless, if you don't want to spend the money on the expensive gear that does it quickly, you're going to be exchanging that for longer wait times.
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Sedit
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You added the part I meant to add Watson, If it still seems to take time its because the tile has become saturated and a quick hit with a hair dryer
will quickly clear up that issue and allow capillary suction to finish doing its job. Even if it is a super fine particle that is no problem as it
will fill in gaps quickly and make its own pores so to speak. This will dry your mud quicker then you can imagine with only minor losses.
Plaster as well as has been mentioned and believe it or not is sort of more efficient due to the bulk of the plaster but it can contaminate your
material with Calcium and this may not be desired in some cases.
I highly suggest reading some on the early day chemistry text like Antoine Lavoisier as he will give you ever getto way possible to perform any
advance form of chemistry you can think of(available at that time mind you).
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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watson.fawkes
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Quote: Originally posted by Sedit  | | Plaster as well as has been mentioned and believe it or not is sort of more efficient due to the bulk of the plaster but it can contaminate your
material with Calcium and this may not be desired in some cases. |
I was thinking about the contamination
problem before. Plaster will contaminate more, but even tile will yield some amount. If it's an issue, I'd say that some kind of cloth or paper
between the mud and the porous plate would do dandy. You're really just shifting the contamination from inorganic to organic, but that's just fine
depending on the kind of impurity you need to get rid of.
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Magpie
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Here's another drying mode, one which I have personal industrial experience: thin film drying. See the LCI website below to see how it is done:
http://www.lcicorp.com/evap/thin_film_drying.html
I have done some slip casting myself using pottery plaster and can vouch for its effectiveness. However, the feed slurry for pottery is normally
about 70% solids.
If you could tell us a little more about the character of your feed and the feed rate it would help us advise you better. What are the solid
particles, particle type, particle size range, % solids, viscosity, stickiness, temperature limitations, etc. And most importantly what is your feed
rate requirement? Also, how much money can you allow for this equipment?
[Edited on 21-11-2011 by Magpie]
[Edited on 21-11-2011 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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phlogiston
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Do you need the fluid to be water-based?If not, you can resuspend the mud in a much more volatile solvent to replace/dilute the water and speed up the
drying rate greatly.
By this method, I used to dry sephadex G-50 that got contaminated with radioactive compounds this way to reduce the volume of radioactive waste. When
wet with water it took 'forever' (months) to dry, but after washing with acetone it was dry in a few days at the most.
-----
"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
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Ozone
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For actual mud dewatering, e.g. clarifier mud from a sugar mill, we use lime to pH 7-7.5, boil, treat with about 5 ppm of a HMW anionic polyacrylamide
and settle. The settled muds are mixed with a filter aid (bagacillo, in out case) and dewatered using a rotary vacuum drum filter (think screen on a
drum). This can be emulated in the lab using a (big) buchner with a fine screen...NOT a paper (which almost never works without either a screen
pre-filter or high pressure, say a yarn-filter).
Cheers,
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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Panache
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sry quoted your first post however i'm referring to the link you provided for thin film drying magpie,
so what ensures the dried solid doesn't, for want of a better expression, 'glue', to the dryer walls, ie the hot zone? Surely its not just because the
blades pass closely?
or is it forced forward by new material entering the drier, in which case what happens when you have no more slurry?
[Edited on 22-11-2011 by Panache]
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Magpie
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| Quote: Originally posted by Panache |
sry quoted your first post however i'm referring to the link you provided for thin film drying magpie,
so what ensures the dried solid doesn't, for want of a better expression, 'glue', to the dryer walls, ie the hot zone? Surely its not just because the
blades pass closely?
or is it forced forward by new material entering the drier, in which case what happens when you have no more slurry?
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The solids are scraped or knocked off the hot wall by wiper blades. The blades are hinged to the rotor and are thrown to the wall by centrifugal
force.
Periodically the dryer is shutdown for a washout. Here the dryer is flooded with water (or a solvent), the wall heated, and the rotor turned on for
an hour or so.
The single most important condition for a successful synthesis is good mixing - Nicodem
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