Effective way of slurry sampling

[Rachit]

I have ~50% slurry mass in a reactor with (4 PBT + 4PBT) agitator. Agitator is rotating at 94 RPM.
To analyze reaction mass we are sending two samples at a time from bottom of the reactor. There is significant analysis deviations in these two samples. I feel that the sample is not representative of the reaction mass.
Is there any way to get representative sample in slurry mass or any advanced sampling technique that can help?
Also is there any calculation/ relations to check if sample is representative of the slurry mass or not?

 

[Lnewqban]

Welcome, Rachit!

Are the agitators effectively reaching and moving the whole volume contained in the tank?
If not reaching the bottom, could you stop the rotating parts and take samples from a higher and mid-radius point?
Can you precisely calculate the original mass of pure water in the mix?

Just a few ideas.

 

[Rachit]

Welcome, Rachit!

Are the agitators effectively reaching and moving the whole volume contained in the tank?
If not reaching the bottom, could you stop the rotating parts and take samples from a higher and mid-radius point?
Can you precisely calculate the original mass of pure water in the mix?

Just a few ideas.

You can say that the agitator reaches upto 96% of the reactor height( or depth).

Sampling from different points of the mix is not possible due to safety concerns.

The original mass of pure water is known (precisely).

Now, is there any correlation or formula to check settling velocity in a pipe placed at an angle from vertical

 

[jrmichler]

There are so many variables involved in slurry settling that formulas are impractical. For example, precipitated calcium carbonate settles completely differently than ground calcium carbonate with the same particle size. A lesson that a certain agitator manufacturer learned the hard (expensive) way.

An agitator sized for complete mixing is more powerful than an agitator sized for off bottom suspension. If your agitation system (agitator, impeller, tank shape, baffles) is sized for anything less than complete mixing, there will be variations in concentration. Those variations would show as concentration differences between successive samples.

Does your sample system allow the slurry to settle in the pipe immediately before the sample valve? If so, are you letting it flow before capturing the sample?