Mixing Vessel Dimensions

[paulspoon]

For optimum mixing of a powder in a liquid, are there ideal dimensions for the such things as: height of liquid above the impeller, impeller rpm etc. The reason i ask is that we are trying to mix 16kg of a powder with 64kg of a liquid and to be honest the results we are getting are hit and miss. On some occasions the powder does go into solution but on others it just sits on the top of the liquid and no matter what we do (increase rpm etc.) it refuses to go into solution. The 64kgs and 16kgs never change. Charging times, temps etc are always kept constant.Does anyone have any idea on what could be happening?
Thanks

 

[Latexman]

What's the powder? What's the liquid? What's the liquid temperature? How is powder added? What type and diameter of impeller(s)? RPM? HP? Dimensions of tank? Is agitator top center mount, top off-center mount, or side mount? Impeller distance off the bottom? Does tank have baffles?

That's all for now.

Good luck,
Latexman

 

[m777182]

There are some other questions about your powder like size distribution,density etc. as well as about your liquid like density, viscosity...then you can talk further about an efficient mixer.
A good way to input powder into a solution is a system with circulating the solution through an eductor. Look to the thread124-131792.
m777182

 

[Latexman]

paulspoon,

Hopefully you can retrieve data that was collected in the past on each run and determine what parameter(s) are *KEY* to the success of a batch. This is where statistical software like JMP by SAS (God bless you Jim Goodnight!) is just wonderful. Take *every* piece of information available, no matter how little you think it has an impact, and create a database. On each row for a batch, record the powder properties(product code, product batch number, particle size, density, acid number, pH when dissolved in water, any and every parameter you have), liquid properties (pH, composition, hardness, density, viscosity, acid number, again - any and every parameter you have), process procedure (initial liquid temperature, agitator initial RPM, temperature ramp, RPM ramp, final temperature, final RPM, etc.) and conditions (ambient temperature, who the operator was, who the lab person was, was vessel washed prior to run, time of day, etc.), and whether it was successful or not(yes or no).

Then, look at the data and see if you can determine what leads to success. If you can't, start collecting data that may be pertinent on every batch and evaluate the data as you go along. There *is* a parameter(s) that will be important, you just have to find it!

Good luck,
Latexman