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How does an aspirator(destoner) work?

by gogulashanth
Tags: aspirator, destoner, oil mill, zig zag
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gogulashanth
#1
Jul19-13, 12:00 PM
P: 1
good day,
I am having trouble designing a destoner with an intergrated aspirator. hence I would like to know about the inner structure of a zig zag aspirator. thanks in advance.
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Baluncore
#2
Aug1-13, 03:53 AM
Sci Advisor
Thanks
P: 1,924
What are you trying to sort? Are you removing a few stones from many seed. If so, they are separated based on aerodynamic drag and density. The use of a pair of sieves to select only particles with the size range of the seed will reduce the problem to one of density alone. Adjustment of the duct size or airflow can then be made to separate the densities.

Google; “zig zag aspirator”,
Or ask a more specific question.
drragonx
#3
Aug1-13, 12:39 PM
P: 1
I need to remove dust from sesame seeds so i decided to make a zigzag aspirator. I have searched the net and found a bigger version but I need to make a smaller version. I have attached the picture. I need to know the inner layout of the top part (aspirator) A small sketch would be adequate. Btw thx for taking ur time to reply.
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Baluncore
#4
Aug2-13, 11:44 PM
Sci Advisor
Thanks
P: 1,924
How does an aspirator(destoner) work?

Here is an example sectional drawing of a zig-zag aspirator, (on page 3).
http://www.kimseed.com.au/Seed%20Pro...0Aspirator.pdf
Notice that it has a clear side so the operator can see the process in action and adjust the air vents precisely.

Stock is fed in at a controlled rate from a vibrating table at the top. You can make that table from a rubber mounted, gently sloping tray, with a small electric motor attached. The motor has a slightly unbalanced flywheel that gently vibrates the table and so stock creeps or walks into the zigzag column. The table and vibrator are mounted in a sealed cavity at the top of the machine to prevent loss of air at the top of the column.

Air is introduced near the bottom of the column at a calibrated volumetric flow rate. It flows up the zigzag column but some air escapes at each level so the volume is reduced progressively. The section of the zigzag column remains the same so the velocity of the airflow reduces up the column. At each zig or zag there is a mixing due to slight turbulence at the bend. That mixing tumbles the stock and so prevents clustering or clumping.

Now as stock falls down the column the free falling speed = terminal velocity of the particles is effectively compared with the speed of the rising airflow. If the particle is falling slower than the airflow in the zig below, it will stay at that level and eventually moves sideways into the hopper at that level.

Each hopper has a large section upper part with an adjustable air vent. Material will fall down into the bottom of the hopper because the air velocity in the upper part is slower than that in the column needed to reach that level.

By adjusting the individual hopper vents you divide the airflow to select various terminal velocities in the separator column that are close to optimum for your stock. That makes it possible to select a different component of the stock at each zag. It is possible that a clean separation may not be achieved. In that case the heavy and light hoppers will be clean but the intermediate will still be a mix. The intermediate mix can be reprocessed again several times, possibly with new stock, sorted on a gravity table or maybe discarded.

Now that you have a summary, you can ask more specific questions about the process.


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