I am designing a simple centrifuge to separate soil by particle size (as well as decanting water). My goal is to be able to continuously funnel in 500 $cm^3$ of soil and 1.25 liters of water and have the components of the soil (clay, silt, sand) separated from each other and funneled into individual containers for each component. Water will be easily decanted and I know how to do so.
The problem is that I am having difficulties trying to figure out how to easily and continuously extract the soil layers without remixing them together. It is important that the machine is able to sort the soil layers while the centrifuge is still spinning. This is due to waiting for the centrifuge to stop spinning/restart spinning adding large time wastes over many kilograms of soil processed.
I was thinking about adding opening/closing dividers to attempt to keep the layers separate while funneled out, however, there are two problems with this:
- The ratio/amount of soil components (again, clay, silt, and sand) is unknown. Installing opening/closing dividers will have to be at fixed positions and as the soil components are unknown, dividing along these fixed positions will cause some remixing of the soil.
- I am hesitant to introduce moving parts on a spinning part spinning at 2,500 RPM (the inner drum of the centrifuge). This seems like an unnecessary safety risk that I would like to avoid, if possible.
What is supposed to be happening in the centrifuge is similar to if you grabbed some soil, mixed it with water, and let it set, but exceptionally faster. If I wait for it to settle naturally, I have to wait 4-5 days for a small 500g sample to fully settle, whereas with a continuously flowing/separating centrifuge (and additional mechanisms), I can expect to sort hundreds of kilograms within a day. This, along with it automatically sorting soil components, drastically improves my workflow.
Short explanation of expected sorting behavior:
- Sand particles (defined as particles with diameters from 0.05 mm to 2 mm) should separate closest to the wall of the centrifuge due to being the densest particles in the soil.
- Silt particles (defined as particles with diameters from 0.002 mm to 0.05 mm) should separate and collect in the "middle" of the soil solids due to it being the moderately dense particles in the soil.
- Clay particles (defined as particles with diameters less than 0.002 mm) should separate closest to the water layer due to it being the least dense particles in the soil. I also expect organic matter to collect close to this layer, but I know of some ways of eliminating the organic matter.
- Water, of course, would be the furthest away from the wall due to it being much less dense than any of the soil solids.
It is not required for the sorting to be perfect. For instance, I do not expect perfectly sized particles that are perfectly sorted. I do expect some silt to be mixed with clay, sand with silt, etc. However, I would prefer this to be minimal with a reasonable setup.
I greatly look forward to your suggestions. Additionally, if I have missed any oversights, I appreciate pointing them out as well. Thank you very much.