Sodium Bisulfite Injection in Carbon Steel Line 2

[tknight99]

Hi, we are wanting to dechlorinate potable water prior to feeding it to a water demin plant. Sodium bisulfite injection is the direction we are leaning towards. Wondering about potential corrosion issues we may see as a result of either the sodium bisulfite itself or the HCL produced as part of the neutralization reaction.

The chlorine levels in the water is 1 mg/L max, so there shouldn't be more than 1 mg/L of HCL present in the water based on the stoichiometry. The line we are planning to perform the injection in is carbon steel. 10" line with flow ranging from 100 m3/hr to 350 m3/hr. Temperature 5 - 25C.

Should we expect any corrosion issues in these conditions? Anyone have any experience with sodium bisulfite injection?

 

[btrueblood]

Bisulfite injection?

 

[tknight99]

Yes, it should be bisulfite. Thank you

I've corrected the original post.

 

[hacksaw]

You might consider slaked lime that is properly diluted prior to injection.

 

[Dhurjati Sen]

Scaling (due to formation of iron sulphide) could be a possibility?

DHURJATI SEN
Kolkata, India

 

[TugboatEng]

Water in steel piping will ALWAYS present a corrosion issue. If it's a closed loop you can treat the water with inhibitors that are very effective against corrosion but chemical injection implies this is an open loop system. Do investigate the option of corrosion resistant materials. They allow thinner walls and can reduce fabrication costs.

 

[0707]

Carbon steel is not recommended for bissulfite sodium, continuous use.

 

[bimr]

The amount of HCl generated will have little effect on the water pH or corrosion. The bigger corrosion issue will be in the bisulfite piping and the injection point.

One would think that you already have corrosion issues with the steel piping. Consider changing the steel piping to SS, lined pipe, or FRP. You may have some corrosion issue at the point of injection, but once the chemical is mixed, the corrosion will probably be less than what you are currently experiencing because the bisulfite will also scavenge the oxygen from the water.