Silica Slippage in Demin Water

[aahmed]

Hi everybody
we have two sets of SAC and SBA anion resins.We are using Rohm and Hass Resins.Total silica in our feed water varies ( open surface water) between 5-8 ppm.Now we are facing problem of silica slippage from anions at same throughputs where we used to see normal results.our limit is 0.05 ppm but at 1300 m3 throughput silica breakthrough is seen upto 1.0 ppm.please suggest what tests, checks or any other remedial actions

Best Regards

Best Regards
aahmed

 

[bimr]

1. Check the age of resin. If the anion is older than 7 years, think about replacement.
2. Check the season. Silica concentration may change seasonally.
3. Do you have a mixed bed. If so, it should polish up the anion unit effluent.
4. Check operating logs to determine if regeneration has been performed correctly or has been changed.
5. If all else checks out, you can contact manufacturer of equipment.
6. Try to increase regenerant dosage or double regenerate.

 

[aahmed]

Thanks Bimir for your reply

Check the age of resin. If the anion is older than 7 years, think about replacement.( we replensih 33% resin each year)
2. Check the season. Silica concentration may change seasonally.( yes silica is changing from 5 to max 8.7 ppm. But pl note that at 7 ppm,tranis were giving throughput of 1500 m3 and at 8.3 ppm silica,we had to decrease throughput to 1000m3 beacuse silica started slipping)
3. Do you have a mixed bed. If so, it should polish up the anion unit effluent.( yes we have mixedbed polishers, but you know high silica from anion not only exhaust mixed bed early but daily caustic consumption is also increased. secondly with increased no of regenerations, total demin water production/day also decreases)
4. Check operating logs to determine if regeneration has been performed correctly or has been changed.( as per our understanding,it seems normal)
5. If all else checks out, you can contact manufacturer of equipment.
6. Try to increase regenerant dosage or double regenerate. ( have done double dose regeneration )

Just have asked lab to check if ratio of colloidal silaca is increased in raw water. can you pl tell how anion bed preheating step is done beacuse we dont do this at our plant.or any other checks you want me to do?





Best Regards
aahmed

 

[bimr]

You need a heat exchanger to accomplish heated regeneration.

You might check the raw water supply. If you are using surface water, perhaps the coagulant and/or polymer dosages require adjustment to optimize colloidal silica removal.