Tank mixers are a fairly common product, so I would contact a few vendors, give them the density and viscosity of the solution along with the tank dimensions, and let them go from there. If the grit wears the prop too much, consider a rubber coating.

In addition to #1↑ there is a whole raft of tank mixing stuff in Perry, "The Chemical Engineer's Handbook". Digesting it might save a few false starts. Try and get access to a copy.

Steel grit you say...

A magnetic agitator external to the tank would work a treat.

This arrangement is commonly found in jewelry polishing applications were steel pins(aka needles) are agitated to peen and polish product bathed in a tank. A prop in the bath would get in the way and mangle product....or in your case possibly erode the prop leading to high maintenance and/or undesirable alteration to the bath chemistry.

Just had a whimsical thought...wouldn't a laundry washing machine with its agitator work?

Please add another idea:(magnetic stirring-is very good professional solution)

Purging with neutral gas (if air is oxidizing the grit too much...)

Purging with Nitrogen is quite available today

We had the same problem using water and pumice for blasting. We assisted the mixing with compressed air. We made a square of 1/2 pvc pipe with holes about every 1/2" that fits the bottom of the tank.

Think of something like a gas oven burner faced downwards. this loosens the solids and aids in mixing.

First, I would like to say thank you to everyone's comments. Each has added something to my knowledge base.

To Mike, especially thanks for the input and questions. They do cause me to think and have even more questions.

For a foundation and reason for the initial questions let me explain the purpose to begin with. The goal is to make cement copper. Which by simple definition is: A precipitate of copper from copper sulfate solution by the addition of iron.

In this case we have a Pregnant Leach Solution (PLS) derived from leaching copper oxide ore with a dilute sulfuric (less then 1%) solution. After leaching the PLS is stored in a tank to be pumped to the mixing tank.

To answer question 1) the grit is cast steel with 98% Fe iron.

Question 2) it is consumed in the process. When the solution touches the iron there is an ion exchange where the iron that is in contact with the solution becomes copper. This falls away exposing a new iron surface to again contact the solution and continue the process until the iron has completely dissipated. This reaction is nearly instantaneous and is the reason for the agitation. The greater the agitation the faster the process.

Question 3) What is decanted from the top is the spent or striped solution. There are two tanks in this setup. One inside the other. Both tanks are cone shaped at the bottom. The precipitated copper goes through a 100 mesh SS screen that is placed between the two tanks. It goes from the top of the inner tank to about a foot below the top of the outer tank at a 45 degree angle. (Not sure how to insert a drawing like yours, but it would certainly convey better understanding as yours did.)

The process I am trying to create is to keep the iron low in the inner tank with the precipitated copper moving up and dropping through the screen before reaching the top and going out with the spent solution.

An earlier try was to have the solution pumped into the bottom of the inner tank. This through 3 pvc pipes attached to 3 equally spaced baffles on the inside of the inner tank. Holes in the pipes were aligned to create a swirling motion for agitation.

It turned out that the holes plugged and stopped any flow when the inflow was slowed enough to allow the PLS to be fully stripped.

This is why I've gone to the propeller for agitation. While I am not yet sure of the exact flow rate I need, I am now metering the solution into the top of the tanks with a simple ball valve from a gravity flow tank.

From your explanation I can see that the main propeller needs to be low and vertical but not sure of the others to keep the grit down until it can go through the screen when it becomes copper?

I am thinking (or perhaps hoping) that the copper will be both forced up the sides and have enough weight to go to and through the screen instead of up and out the top of the outer tank.

Thanks again,

David

Hi David,

I somehow missed seeing the notification of your reply to my post. I need a bit of time to digest the gist of your process. However, I do plan on returning with some constructive input once I have done so.

Mike

No worries, just got in from the mine for a rare visit home during the week, back early tomorrow. Generally I stay at the mine during the week and home on the weekends.

Your previous comments were very constructive and I do look forward to hearing from you again.

Thanks

Thanks for the word picture....

If you can't sort out a sketch of the setup can you post some photos of the existing setup please?

Here are some pics of the original setup.

1 Inner Tank & Screen Supports

2 SS 100 Mesh Screen

Tank with Return in Place

4 Side Inflow to inner tank & bottom discharge of outer tank

Dear AZ Miner

Understand that this surroundings-isn't supporting any purging with Nitrogen gas...

But a suggestion ; could you elevate the feeder several metrs high,and thus enhance

mixing?

When you talk about the "propeller" I take it the right term would be a "Screw Conveyor".

Keep the screw conveyor a right handed pitch. The flight pitch should be equal to the depth the thread. The Vat should be tapered, with the small diameter at the bottom. The diameter of the screw should be slightly smaller than the diameter of the tapered Vat at the bottom. The screw when rotated clockwise direction ( Looking from the top) would bring the grit to the top and drop it again to the bottom. The process would go on till the chemical reaction completes.

The propeller is, I believe; a regular propeller not a "Screw Conveyor." It is attached to a motor by a single shaft which turns clockwise when viewed from the top. The front of the single blades are lower then the top part of the blade. In other words turning clockwise (viewed from the motor at the top of the vat) the lower or front of the blade is going "into" the solution first. Is this a "right handed" blade?

Thanks

Yes. (Analogous to screw threads and ship props.)

Got it, Thanks

This is the screw which I meant. In case you want it to be used vertically, make the Vat in a tapered fashion. In case you want it horizontally, you can use it to rotate both ways. However, the other parameters like the density of the slurry and the quantity to be agitated or mixed has to be arrived at, to have the right design of the screw.
See if the photo below is useful for you. Use two screws rotating in the opposite direction and substitute the paddles with the screws as shown below in the photograph.As you rotate the screw in one direction the slurry would collect at one end. Reverse the direction bring back the slurry to the other end. The operation would go on back and forth.

Makes since, I do understand it better, Thanks