×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Water Treatment for Closed Boiler System

Water Treatment for Closed Boiler System

Water Treatment for Closed Boiler System

(OP)
We're considering a thermosiphon reboiler, carbon steel construction with an electric element, providing saturated steam at 260-300 C to a coil in a pilot plant process vessel.

The water/steam system is totally closed, and will only be opened if leakage has depleted the water sufficiently.  There are very few joints in the system so it shouldn't be opened often.

Any recommendations on a passivation procedure prior to protracted operation? Any recommendations for water preparation?  Don't direct us to Nalco or the like, because they're not anxious to bother answering questions like this if there's no ongoing need for chemicals.

RE: Water Treatment for Closed Boiler System

Do you have enough heat load to justify a vaporized oil system, such as Therminol or Dowtherm.  This way your could just use the latent heat and and keep a low pressure system.
Our plant operates in this range on a very large scale. Our pilot plant has numerous small systems operating in this range.

RE: Water Treatment for Closed Boiler System

You can use tri-sodium phosphate (TSP) to raise the pH tp ~10.5, and kill the oxygen with a little sodium sulfite.

These chemicals are cheap and have worked well for many years.

RE: Water Treatment for Closed Boiler System

(OP)
Metalguy:  the TSP and sulphite was exactly what I was looking for.  Any worries about the sulphate from the decomp of the sulphite?  And is there any benefit to pre-boiling the thing with phosphate and soap, prior to filling with better-quality water?

Unclesyd:  Good suggestion.  We've considered it, but there's too little space inside the pressure vessel to fit a big enough coil to so we could get away with using hot oil vapour instead of steam- and too much of a problem if (when) the process vessel coil fails if we go that route.  

RE: Water Treatment for Closed Boiler System

I'm not aware of any sulfite-sulfate failures in boilers, but I haven't performed a lit. search.  The amount of sulfite used is very small.  I don't think you need a pretreatment unless the system is dirty/oily, etc.

What can be important is to sterilize the system by heating it up very soon after filling it.  Some of the worst bacteria involved with MIC are the sulfate-reducers (desulfovibrio desulfuricans--try saying THAT fast!), and the don't need oxygen to set up their drill presses on your system.  In fact, oxygen makes they go dormant.

They'll drill thru 304/316 faster than a union worker on group-piecework!

RE: Water Treatment for Closed Boiler System

Suggest that you consider sodium nitrite and borate mixtures.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources