Caustic injection into tank for pH control
Caustic injection into tank for pH control
(OP)
We are having issues with caustic injection into 30,000 gallon pH adjust waste tanks. The "injection" is done with a control valve feeding a 1" PVC line into the top of the tank. The issue we are experiencing is crytallization of the casutic in and around the 1" pipe. The pipe ends ~5 feet above water line. The tank is closed but does have exhaust.
1. What causes the crystallization?
2. What is the best method to inject cuastic soda into a water solution?
Thanks in advance,
Andy
1. What causes the crystallization?
2. What is the best method to inject cuastic soda into a water solution?
Thanks in advance,
Andy





RE: Caustic injection into tank for pH control
A better injection point would be on a circulating pumps suction line. Assuming you have enough caustic pressure to overcome the head pressure.
RE: Caustic injection into tank for pH control
Pouring it in from 5 feet above is, as you have found, a little messy, and caustic poses a personnel hazard, too.
If you have a continuous flow into the tank you could tee into that line and the flow would help mix the caustic, or dip your pipe in below the normal waterline and squirt the additive in there. Look for a spot with turbulence and do not inject it where the unmixed plume of caustic will drift over the outlet of the vessel. Frequently it is appropriate to use a mechanical (Lightnin') mixer to homogenize the solution.
RE: Caustic injection into tank for pH control
RE: Caustic injection into tank for pH control
why dribble caustic into a tank, you have little or no control of the mixing, dilution, and or contact time.
there are common injection methods that involve circulation and mixing tees.
of greater concern is that by injecting in the top of the tank how are you planning to control pH? where is your analyzer point located?
are you batching or continually treating your waste water?
RE: Caustic injection into tank for pH control
RE: Caustic injection into tank for pH control
RE: Caustic injection into tank for pH control
if it is still crystallizing see if you can somehow heat your solution besides diluting like some hot stream you have nearby.
Now if you say you have crystallization around the pipe and that the tank is closed I would think of leaks, give it a look since Soda is a very dangerous chemical, and all the time wear googles, the soda diffuses very fast in the retine.
RE: Caustic injection into tank for pH control
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RE: Caustic injection into tank for pH control
Ash Fenn
www.cdrpumps.co.uk