One big tank of chlorine or several small ones? 4

[SrChemE]

Hello,
If possible, can I get your thoughts on if it is better to have one big tank of a toxic material onsite or several small tanks??
Is there any process safety guideline (or standard) that can help me with that?
Thanks in advance!

 

[jari001]

To me, that question is heavily dependent on the location and processes that uses the chlorine. Do you have an actual situation you are analyzing?

 

[SuperSalad]

Please define the better you are looking to reach.

Better for processing, safety, regulatory compliance, cost, all of the above?

- Andrew

 

[SrChemE]

I am editing my previous note: I am mostly interested in regulatory compliance side.
The site I work at is planning to build a new chlor-alkali plant for the production of chlorine, which we use many railcars of every month.
I am trying to find out if from a PSM standpoint there are guidelines on having a big tank of a toxic substance versus several small ones. I was unable to find any codes or other guidance documents available for reference.

 

[TiCl4]

SrChemE,

From a PSM perspective, a single tank of chlorine (assuming liquid chlorine) will present fewer opportunities for failure, and as such is preferred from a risk mitigation standpoint on the probability of something failing. However, having only a single tank will require special considerations for tank inspections, with full clean out and stoppage of whatever process is using that tank. We actually had liquid Cl2 supplied to us as part of the TiO2 process, and we had multiple tanks. Your selection of tank may also be limited by the capabilities of the manufacturer for liquified gas storage tanks.

From an RMP perspective, having smaller tanks will limit impact to local communities due to smaller total quantities released per tank, so it is always preferable to have more and smaller tanks from that perspective.

Overall, from a safety, operability, and feasibility standpoint, I believe you will likely end up with multiple tanks (at least 2), with the choice of 2 vs 3 vs 4 vs more being based on your total storage volume required, balancing RMP/PSM needs, and on manufacturing capability for such tanks.


See the Liquid Chlorine Storage and Handling Guide

https://www.google.com/url?sa=t&rct...et05-eng.pdf&usg=AOvVaw3L0UAs3bK4uVqlphCNDSZQ

Edited for clarity.

 

[georgeverghese]

Also check your existing tank dike containment volume and capacity / limits of emergency recovery equipment in the event of a single tank rupture.

 

[pierreick]

HI,
Consider to read this memo about hazard regarding this material:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4478383/

This may help you .
Pierre

 

[MJCronin]

TiCl4, as always, gives solid advice ....

I believe that this speculative question was asked by someone with too much time on thier hands ... In my opinion ...

The pamphlet from the Chlorine Institute provides important insight and the collective wisdom of decades of Liquid Chlorine handling experience.

What has not been mentioned yet in this discussion is the absolute horror that would exist when resupplying and re-filling your multiple tanks at a process plant site. There would be multiple fill lines, automated valves, tank level safety devices, relief valves, monitoring points etc. etc... etc. Depending on the plant configuration, multiple transfer pumps and tanker offloading points might also be required ... !!!

Let us assume that the multiple tank volumes can be supplied by a tanker truck and NOT a railcar.

The massive increase in CAPEX for the multiple tank scenario - JUST TO PERFORM SAFE TANK FILLING OPERATION ALONE - strongly supports the single chlorine tank concept.

I would like to hear the opinion of others on this topic ..

Anyone out there ?

MJCronin
Sr. Process Engineer

 

[SrChemE]

TiO2, MJCronin and all, thank you!
Yes, this is for the production of liquid chlorine. Currently the chlorine is used directly from railcars, so the idea is to have it coming to us directly piped over. (We are experiencing chlorine availability constrains).
The idea is not to transport it via tanker truck or railcar, but via piping.

MJCronin, your concern (absolute horror of filling multiple tanks) is real and is being considered. To minimize those hazards we are planning to pipe it over to the plant. Above ground piping, minimizing pipe size and the number of flanges.
Thank you, still interested in comments and opinions to come.

 

[SrChemE]

The Chlorine Institute pamphlets are our bible.

 

[TiCl4]

SrChemE,

I can't get into too many details, but having a chlor-alkali plant next door feeding chlorine storage tanks via pipeline is exactly what we had. We also had multiple tanks, but I do not know the driver for the exact number of tanks.

MJCronin's point about each tank adding additional CapEx and complexity should be well taken, although I wouldn't call what we had an absolute horror.

I would suggest talking to a few reputable tank manufacturers to gauge the size of tank they have the capability of manufacturing.

This appears to be initial feasibility review of an idea. Having seen the other end of the "build a chlor-alkali facility to ease Cl2 constraints" idea, I can tell you that the IRR of such a proposal will not be attractive in the slightest as opposed to continuing to bring Cl2 in railcar.

 

[EdStainless]

I have worked with a number of CA plants and large Cl users (for some reason they seem to have corrosion issues).
From my observations I would strongly lean toward 2 or 3 tanks.
Enough to give you some redundancy to allow of maintenance and inspection while keeping the system as simple as possible.
Since you already handle Cl you know that there is no such thing as saving money on the installation.
They only savings comes from buying the best equipment that you can find to reduce costs down the line.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[itsmoked]

Have you considered the costs and ongoing costs and added liability of all this verses stopping your process occasionally? Maybe maintenance can be standing by to effectively use the shutdowns?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Compositepro]

I worked at a PVC plant in Carson, CA that was shut down in 1982. I do not recall that we had any chlorine storage tanks. The plant was just fed from the rail cars that came from Henderson, NV. We used a lot of monel and other nickel alloys. I still have a 4" binder from Inco about their alloys.

 

[georgeverghese]

Dike requirements are in section 6 of the Chlorine Inst. pamphlet 5 (attached in this thread), while emergency response requirements are in Chlorine Inst. pamphlet 11. Also note the impact testing requirements for carbon steel vessels (and piping too by extension) in pamphlet 5, since chlorine boils at -34degC or so.

 

[SrChemE]

Thank you all for all your input. Seams the right number is between 2 and 3 tanks at least for our purposes, all things considered. This was very informative, as always.

 

[georgeverghese]

Use only bone dry air generated from oil free air compressors, and monitor dry air dewpoint frequently with a recently calibrated water dewpoint meter - "dry air" generated from oil lubricated compressors is certainly not acceptable in this service.