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Soil Extraction Tank

Soil Extraction Tank

(OP)
I am employed by a company that is producing a tank to be used to remove mud from water in food processing plants in areas where they wash the product after it comes from the cellar or field. The tank capacity is around 1700 gallons. The concept is that the bottom of the tank is conical and has an auger with scrapers that push the "dry" mud out the bottom onto a conveyor belt. Due to the size and flowrates, the tank really only gets out large mud particles like sand. We use a sensor to tell when the mud has reached the appropriate level, and then a pinch valve opens and the auger turns on. We usually hold about 60" of mud in the tank to prevent water from escaping when the valve opens. We have been asked to scale up in order to accommodate a higher flow rate. I was hoping to keep the mud level the same in order to keep the auger motor the same as it has been difficult to predict the required torque. My boss wants to proportionally increase the mud level height in order to maintain the quality or dryness of mud coming out. His reasoning was that if we have a larger tank, we will be producing more mud, so we will also be emptying mud at a higher rate. So, in order to not have soupy mud coming out, his solution is to also increase the mud height, which will require more paddles on the auger shaft and a larger motor/gearbox combination.

So here is my question - Should time in the tank matter for how "dry" the mud will be at the bottom, or would 5' of mud be just as dry at the bottom regardless of how long its been in the tank? Does having more water pressure above the mud make the mud at the bottom drier?

Some side questions - I am making the first attempts to quantify the effectiveness of the tank. I would like to measure the soil content coming in and leaving the tank. Is there any suggestions on how to do this? I have thought of trying to dry out the mud in a sample of say a 5 gallon bucket and then weigh it and compare that to the weight of the full 5 gallon bucket.

We sometimes run this in a closed loop where the "clean" water is reused in a product washer and then reintroduced into the tank. Because of the size and flowrates, I know we are not getting out silts and clays. What will happen if the water eventually saturates with clay? Will it also eventually start to settle out faster due to the high concentration?

I am not a soil or a water treatment expert, just a mechanical engineer thrown in charge of a crazy project. All thoughts and comments are welcome.

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