Electrostatic Sorting

[misterT]

Hi, My father needs a system to sort flour (fine flour from coarse flour). We have tried mechanical and air-sorting, but the results have not been good enough. The new idea is to drop (charged?) flour through static electrical field so that the finer particles would deflect more than large particles when they drop.

Is this something that sounds feasible? What would be the easiest/cheapest way to try this idea. How would I safely create this strong electrical field?

Thanks.

 

[jpanhalt]

I believe it is feasible, at least on a small scale. Check out electrostatic filters for incinerators as a model.

John

 

[misterT]

I found a good image about what I'm after:


How should I create that electric field? I have no idea how large and strong it needs to be.

 

[jpanhalt]

A quick search on electrostatic precipitators (another name for filters) for incinerators yields lots of results, but no details. My guess is a few thousand to 20K volts DC. You might rig it as an upside down van de Graff and let the particles carry the charge. Maybe if you go that route, you could use magnetic coils to cause the deflection.

Your original question was whether we thought it was feasible. I have no practical experience in building such separators. Sorry.

Can you do this in an inert atmosphere? Flour dust can be explosive.

Have you considered differential, continuous centrifugation? Places that do lots of particle blasting for cleaning and metal prep have "reclaimers". These are basically centrifugal blowers. The heavy particles settle down and the lighter go out the exhaust. A 2-stage setup would potentially give heavy, medium, small and dust.

John

 

[Mr RB]

CRT TV sets make a pretty good electrostatic field on the front of the picture tube. Maybe you could use a flyback transformer from an old TV and use it to charge up a big glass plate. Be careful as fine flour is not only a fire hazard but an explosion hazard due to the high burn rates.

Personally I would make an air sorter (mass sorted winnower) with multi stages, given that gravity and airflow can both be very constant you should be able to make one very reliable, very safe, and self cleaning. Electrostatic will have some issues with humidity, less so with the air sorter especially if you remove the water from the incoming air it will dry the flour too.

 

[OlPhart]

like a mass spectrometer?

1> inert atmosphere, no grain explosions
2> charge the stream of particles before the threshold
3> threshold has opposite charge... heavier particles carry farther than light ones
4> bin centers could have same charge as threshold: particle flow guide

think waterfall with the water having varying density as dispersed

Just an idea... <<<)))