6 replies to this topic

[Mazfar]

I am working in a large petrochemical complex.
There are several cooling systems like direct sea cooling , cooling towers and close loop cooling waters system using sea cooling water etc.
We are facing problems with close loop cooling water corrossion on process heat exchangers and results in premature replacement of exchangers.
The close loop system is a 10000 m3 system volume and circulation rate is about 500 kMTPD.System uses sodium nitrite as corrossion inhibitor with a non oxidising biocide intermittantly.
Make up used is potable water.The close loop cooling water is freely vented.Maximum cooling water return temperature is 55 C in summer.

I would like to get views on typical industry practice for a close loop cooling system in relation to the following.
1. Are the tanks normally N2 blanketed.Our other systems are N2 blanketed.
2. Use of potable v/s demin for close loop system with nitrite inhibition.

[Art Montemayor]

Mazfar:

I would not expect any corrosion problem steming from a closed loop, water system that is inerted with nitrogen. I have designed and operated various sizes of these systems and never had a corrosion problem. I have used both deminieralized water and potable, tap water as well. I would use the demineralized water supply if it were available, but I have never found it was a pre-requisite. I wouldn't use just any potable water; I would deaerate it first and make sure that the solids contents wouldn't cause any problems in my process.

Without free oxygen in the circulated water, I have found negligible corrosion in all the carbon steel systems I have used in this application. And all the materials of construction I used was carbon steel and bronze - with a few copper parts.

I think your "free" vent is what may be causing you problems by introducing atmospheric oxygen into the water system.

[Mazfar]

Thanks for the reply and sharing very good experience.

[Mazfar]

Is it possible to get literature reference for close loop cooling systems tanks n2 blanketing requirement.

Dear All;
I am a new member (i.e. a newbie); both in this forum and the chemical industry as well. So, pardon me if the question seems trivial =).
I am working in a oleo-chemical multi-complex where we have quite a number of plants producing different products from palm oil feedstock.
We are facing shortage of water, and since our cooling water system is an open loop (where evaporation is there); it doesn't really help, does it?

Therefore, we are looking into close loop cooling system, where the evaporation risk is lower (hence water saving).

I have several questions; which I hope to learn from your experience:
1. We are looking into liquid to liquid close loop cooling water; where sea water is the primary cooling medium.
a. I suppose we need some exotic material on the sea water side of the heat exchanger? any recommendation?
b. The choice between shell and tube vs. large plate heat exchanger? what's the deciding factors?

2. Since we have multiple plants, is it more recommended to have a global system (where one master unit supplies cooling water to all plants) or local systems ?

Thanks a lot in advance.

[fallah]

1a-What do you mean by "exotic" material?

1b-PHE is better because of relatively low design temperature/pressure and also higher efficiency

2-It depends to distance between plants and number/range of cooling levels,but many complexes now are provided by central utility (such as cooling system)

Hope this helps out

[Art Montemayor]

chan_alexander:

Please stop "sky jacking" this 2-1/2 year old thread that belongs to Mazfar, the original OP. Create your own, original thread and you will have 100% response to your specific topic.

By resorting to laziness and not starting your own thread, you make it impossible to organize and sort out the responses to this thread. Members will be responding to Mazfar and you - and any other "sky jacker" that decides to also post THEIR personal topic as well. This converts the thread into a Tower of Babel and utter confusion as to who is responding to whom.

I currently am unable to delete your post, but I will do so as soon as I can. Please start your own thread on this, your topic.

Thank you.