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Q: Drying/levitation of very small particles ( No Answer,   4 Comments )
Subject: Drying/levitation of very small particles
Category: Science > Technology
Asked by: aaniil-ga
List Price: $15.00
Posted: 17 May 2006 14:16 PDT
Expires: 28 May 2006 00:05 PDT
Question ID: 729853
This is a question related to research in food technology. I want to
know references and related work from people who have done anything
similar. Even if you can not provide exact information, I will
appreciate your effort to provide any related information that can
help. Any intuitive but feasible ideas are welcome.

We have a technology that can produce very small and uniform-size
particles. For this specific topic, we make very uniform particles of
sugars (sucrose, glucose, maltose, etc.) of size 300 to 800
micrometers (i.e. any size in between but all the particles will be
almost that size). The problem we face is how to dry those particles
and remove the water to a minimal level (20% or lower water
content)where they do not agglomerate. Note that sugars have very good
affinity to water.

We use initial solution of 40% (weight/volume) of sugar in water.
Generally, the problem is solved if you could reduce the water content
to 20% or low. From our work so far, we know that at appreciably high
temperatures (150-200 degree Celcius or so), drying up to 8-10 seconds
can give reasonably dry particles. The problem with achieving this
residence time in any system is that it is hard to keep the particles
stay up in air without touching anything for this long. We have not
done any modelling but we have tried several drying mechanisms
including a spray dryer of length 30 feet. We were never able to
achieve residence time above 2 seconds. (Most of our work has been on
intuitive designs and the only proven method that we tried is the
spray dryer).

There are several intuitive ideas to help levitate the particles in
air. For example, a ping pong ball can stay in air for long time if
you precisely put it over an air orifice. But it is very hard to
achieve that with a large number of particles in continuous random
motion. This random motion leads to several problems: sticking to
walls, disappearance from the system, agglomeration, etc.

We feel there might be industrial processes already available that can
help us solve the problems. For example, spray dryers and fluidized
beds. There might be horizontal dryers that can keep particles in air
for long. But none are known to us so far. You are welcome to provide
details about their use, feasibility, past experiments, producer
names, etc.

I can provide more details if necessary.

Request for Question Clarification by denco-ga on 17 May 2006 15:40 PDT
Howdy aaniil-ga,

Visualize a "cyclonic silo" of sorts, with a hot air flow.

The "cyclonic" part would be similar to that of a Dyson vacuum cleaner.

The sugar particles would be dropped down a vertical tube (a "silo"),
perhaps a few feet in diameter, with ducts introducing hot air to the
silo so as to introduce a circular flow of heated air.

This circular flow could be designed to provide a general upward flow
of hot air as well so as to increase "hang" time.

In addition there would be holes on the sides of the silo through
which heated air would also flow, so as to create an "air curtain"
to prevent the impact of the particles on the sides of the silo.

The silo shouldn't have to be very high to accomplish the task, maybe
20 to 30 feet depending on the flow of particles.

Looking Forward, denco-ga - Google Answers Researcher

Request for Question Clarification by sublime1-ga on 17 May 2006 19:56 PDT
I just saw a documentary on TV the other day where a frog was 
levitated inside of a diamagnetic field. How? Due to its water
content. This raises the possibility that your 'wet' particles
could be levitated inside such a field in a heated space. When
the particles dried sufficiently, they would fall to the bottom.
I'm sure no such device exists already, so you'd have to build
it, and I don't know if the cost would be feasible.

Here's a link which talks about the frog levitation:

There is no answer at this time.

Subject: Re: Drying/levitation of very small particles
From: elids-ga on 17 May 2006 14:41 PDT
This may be more expensive than you would like. However, a simple
solution would be to create your particles inside an airplane in a
free fall a  ?zero gravity? parabolic descent. As I understand it you
could easily have 30 seconds at a time, then the airplane regains
altitude and the cycle starts again.

You can read more about it and a commercial outfit you could use here
(google cached page)

Although the link for Zero Gravity Corp seems to be stuck on a loop. 

Good luck
Subject: Re: Drying/levitation of very small particles
From: sonoritygenius-ga on 17 May 2006 15:43 PDT
If water is a byproduct of a reaction.. why not add reagents that can
hydrolyze water to minute particles..
Subject: Re: Drying/levitation of very small particles
From: xaviergisz-ga on 17 May 2006 23:30 PDT
you could use electrostatics to levitate the particles. Charge all the
droplets negatively and (carefully) spray onto a negatively charged
Subject: Re: Drying/levitation of very small particles
From: knickers-ga on 25 May 2006 05:59 PDT
There is already well proven industrial processes which handle the
drying of very fine filler particles. You need to look at the
processes or companies that handles such fillers as Clay, Alumina,
Chalks, Talcs etc. These particles range from 0.5 micron to larger and
typically contain large amounts of water. Most processes will use a
calcining oven, a fluidized bed, spray drier or cyclone system. the
cyclone (depending on size) allows particles to be fully airborn and
you can control the time aloft by speed and cyclone size. the input
air can be heated to give the required drying. If you need more help
check out They specialise in Materials technology
and this sort of problem is their field.

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