Dissolving Sodium Hexa Meta Phosphate

Hello, 

We have an application where we will need to dissolve 1m3 batches of 20% SHMP. I've read that it's quite tough to dissolve, but if anyone has practical experience with this it would be very useful. 

1. Is it worth heating to improve solubility?

2. Any specific recommendations on design of agitator or mixing tank?

3. What is the best loading system? There are some in-line feeding systems that I've seen, but I'm concerned about hopper getting strangled. So possibly better over just over the top - This has safety concerns. 

If someone has information on dissolving this chemical or similar ones, please get in touch. 

Thanks

Taxonomy

• Chemical Treatment
• Inorganic Chemicals
• Chemical Materials
• Chemical Engineering
• Utility Chemicals
• Treatment Chemicals

5 Answers

1. Get ground SHMP, a volumetric feeder and a high shear pump. Introduce the SHMP into the suction side of the pump with a volumetric dry screw feeder. Option 2 buy a 38% solution and dilute it locally.

   Adding large amounts of SHMP into a tank gets you SHMP gunk on the bottom of the tank that takes a long time to dissolve. You want to increase the surface area of the SHMP to the water.

2. Heating is likely  to partially hydrolyze hexametaphosphate to orthophosphate.

3. Warming a little may help, but don't let it get hot (>50 C), or the polyphosphate will start to break down.

4. James thank you for your answer, this is useful information. The dissolving basket is a good idea. Do you know any EU suppliers you can recommend?
   We have a liquid-liquid blending tank and mixer, but don't think this will do the job as rpm might be too slow. Can anyone recommend a mixing tank manufacturer?

   Thanks for the help!

5. 1 M3 of solution at 20% strength = 1000L, In that 1000L there is approximately 1000 Kg water, and 200 Kg SHMP.  Your task will be somewhat laborious.  With medium agitation that moves through the tank volume once per every few minutes, assume for now, 200 L/m, you will add approximately 1 Kg flakes or crystals (with the crystals be sure to disperse these widely over the surface of the water, or you will get clumps that take too long to dissolve). You might want a dissolving basket (made of steel, with holes in it) to hold the solid up from any pump suction involved.  Your addition rate may vary plus or minus, depending on initial experience mixing.

   If you just dump the material in the tank, add the water, and hope for the best, you will have poor results, and it will take days, not minutes or hours to get the solution you want.

   I expect the solution at 20% to have a specific gravity of 1.33, density will be also about 1.33 Kg/L.

   Once you know the solution properties, you can easily calculate your mixing ratio as to how many Kg SHMP to add to how much water.  It should be relatively linear in nature, since the volume of mixing for this is somewhat low.