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What Is The Best Injection Point?


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#1 rikakose


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Posted 30 July 2018 - 04:43 AM

Please refer to the sketch. 


PH in the product tank has to be kept at 9. Caustic needs to inject to product tank regularly. What would be the best point to inject caustic?


Suction side of the circulating tank or the discharge side?


I normally make it at discharge side. Flow always goes to the lower resistance direction. Injecting while circulating. 

Recently I saw someone make it at the suction side. 


There is another option is to make the injection on the top of the product tank. splash load. this option will have no contamination concern but we need a 11m long vertical pipe.


Making the connection on the pump circulation lines, there has to be a double block bleed valve and a check valve on the caustic discharge line to prevent contamination. 



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  • Attached File  Sk1.docx   27.56KB   12 downloads

Edited by rikakose, 30 July 2018 - 04:47 AM.

#2 breizh


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Posted 30 July 2018 - 06:59 AM

hi ,

you may consider a static mixture , it will improve the mixing !

A lot of literature can be found using your favorite engine , you can contact manufacturer like Sulzer .

Hope this is helping you.


#3 thorium90


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Posted 30 July 2018 - 07:30 AM

Pumps are very good mixing devices, even better than a static mixer, I would put it at the pump suction actually, let the pump do the mixing. Its a centrifugal pump right?

If you think there is a need to prevent backflow of product into the chemical tank when the pump is not running or for some other reason, put a check valve then a pressure regulating valve at the dosing point. The check valve can prevent the backflow and the pressure regulating valve will ensure consistent dosing by maintaining the pressure just before the dosing point.

Don't put it at the top of the mixing tank, it will indeed splash and at pH 9, maybe even foaming.

Edited by thorium90, 30 July 2018 - 07:31 AM.

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