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Q: Drying/levitation of very small particles ( No Answer,   4 Comments )
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 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. http://www.dyson.com/nav/inpageframe.asp?id=TECH/DYSONCYCLONE/MENU/MENU&sinavtype=menu 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: http://www.hfml.ru.nl/froglev.html sublime1-ga```
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 ```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) http://72.14.207.104/search?q=cache:HHs8ohIPWGkJ:www.msnbc.msn.com/id/5992077/+zero+gravity++airplane+company&hl=en&gl=us&ct=clnk&cd=1 Although the link for Zero Gravity Corp seems to be stuck on a loop. Good luck```
 ```If water is a byproduct of a reaction.. why not add reagents that can hydrolyze water to minute particles..```
 ```you could use electrostatics to levitate the particles. Charge all the droplets negatively and (carefully) spray onto a negatively charged plate.```
 ```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 www.mtechltd.co.uk They specialise in Materials technology and this sort of problem is their field.```