Ion Exchange vessel

[shahyar]

One dumb question:
In Ion Exchange vesels, whole vessel is full of water during normal operation and during regeneration, or we have sort of "water level" in the vessel?

Thanks

 

[quark]

Ok, some hints.

What is the flow direction of water during normal operation and during regeneration. If any one is upwards, which way is possible, either full vessel or partially empty?

When you are pumping water into the vessel, at higher pressures than atmospheric, can you be able to establish this if you have a partially empty vessel, irrespective of flow direction?

 

[siretb]

Should be full of liquid.

 

[Zoobie]

Does this pertain to water purification or some sort of process application? I agree that the vessel should be full. In some applications I have seen where due to the compositions of the process fluid and poor water displacement before regen that you can get some gas generated in the vessel when acid is introduced. Obviously this is not 'normal'.

As a side note, there have been documented incidents where vessels have ruptured/exploded due to a severe manifestation of this problem.

 

[kenvlach]

Full.

Zoobie, can you give some more details on the incidents you mentioned -- crossplumbing between caustic anion regen. & acidic cation regen?

 

[Zoobie]

kenvlach:

No this wasn't a plumbing issue. A specific example is in a sodium chlorate purification process to remove Ca and Mg. If the sodium chlorate solution (typically crystallizer mother liquor) is not fully displaced then when strong acid (hydrochloric) is introduced there is the potential for chlorine dioxide gas to be generated in the vessel. I know of at least one incident where this resulted in an explosion. Even if displacement is nearly complete, residual chlorate and acid will do a good job of smashing the resin beads to bits. Obviously this is not something that most people will encounter (especially considering the size of the sodium chlorate industry).

While I have never confirmed this, I wonder if any reaction with brine with excess soda ash could result in some CO2 generation by the same mechanism (this wouldn't be a severe reaction but it probably would create some gases in the vessel).

 

[sbush]

During normal operation the ion exchange vessel should be completely full of water. An automatic air vent should be installed at the highest point of the vessel and piping to ensure that air is completely removed when the vessel is pressurized. Otherwise, hydraulic ram and/or flow surge can occur.

During regeneration, the vessel should also be full of water (unless mixed-bed ion exchange vessel during air-mix stage). Some equipment manufacturers have the regeneration waste lines below the vessel. This causes a syphon action which causes the water level in the vessel to drop over the course of regeneration. This can result in poor chemical distribution and other hydraulic problems. To maintain a constant water level in the vessel during regeneration, all drain lines should be plumbed to an elevation higher than the vessel and then brought back down to the discharge drain (i.e., like an inverted "U" tube). This "trap" will keep the water level constant within the vessel. This piping method should be used with mixed-bed deionizers also, provided that pressurized air is used to "blowdown" or draindown the vessel prior to the air-mix stage.

S. Bush

http://www.water-eg.com

 

[shahyar]

thank you, you guys.