Mixing with circulationpump

[EvW]

I'm a student on a work placement and I've got the following question. In our company we use a circulationpump to mix a solution, and bring this solution on pH (batch proces without stirring).
I want to know how you calculate the minimal mixingtime to make this homogeneous.
Where can I find this or how to calculate this.

Many thanks

EvW

 

[IronMike]

EvW - Presumably you are mixing a tank with the circulating pump. You can get as detailed or as simple as time allows. If your tank mixing seems fairly turbulent, consider it a stirred-tank and the rule-of-thumb is to wait for three turnovers to get 95% of a step change. A 1000 gallon tank with 200 gpm pump would have a turnover every 5 minutes (1000/200) so that you'd need to wait 15 minutes to sample. If the flow is low, say 50 gpm for a 20 minute turnover, you may need more than three. You can imagine at a low flow that the liquid enters the top of the tank and flows downward at a leisurely pace. A good improvement is to add a mixing eductor fairly cheaply to multiply the effective flow from the pump (usually by a factor of 5). This increases the circulation flow in the tank and reduces the effective turnover time by a similar factor of 5. Hope this helps. - IronMike