6 replies to this topic

[aljabi]

Hello,
could anyone please let me know what type of insulation is used for absorption columns, specifically for Triethylene glycol (TEG) absorption process of water from natural gas.

i know of the following:
calcium silicate
Foam glass
mineral wool
fibreglass

if the material used for insulation is not available on the list above could you please mention its density, or if possible sources where i can find information regarding this matter.

thanks.

[Padmakar Katre]

Dear,
I hope you can get some information by communicating the concern from the link below who are mainly in TEG dehydrators.
http://www.qbjohnson...54/Default.aspx

[Art Montemayor]

aljabi:

Now you have made me curious.

Where have you heard, seen, or read that TEG dehydration contactors (absorbers) need to be insulated when used to dehydrate Natural Gas streams? I have been around these units for many years - both off-shore and on-shore - and I've never seen one insulated. I've also designed them and the TEG process - and I've found no need to do so.

Perhaps you are modifying the process? Perhaps you may need insulation in the manner you are employing the process. I would like to know how you developed a need for insulating a TEG contactor in natural gas service. Or are you thinking of the TEG stripping column? If so, I've never seen one that is taller than 10 feet - and so, the insulation is negligible.

[aljabi]

Thank you both for your help.

Mr. Art Montemayor,

being a petroleum engineering student im not really exposed to much of designing of vessels and what not. I was looking at a book called Coulson and Richardson volume 6, which gives outlines on how to design thin walled vessels under internal pressure, and was wondering whether or not insulation is required. In that case if no inuslation is required, then when calculating the dead weight of the vessel we can ignore the weight of the insulation? is that the case?

We are actually designing a gas dehydration process for an offshore field scenario (Troll Field) as part of our final year group project. we have already designed the process and currently are rechecking everything where we found some inconsistencies in the absorber design.
To your knowledge what would be the standard specifications of an absorber given the following data:

Gas flow rate: 349 MMSCFD
operating pressure: 1000 psi
Temp: 80 F
water content: 30 lbs/MMSCF

Thank you very much for your help!

[Art Montemayor]

Aljabi:

You are demonstrating good engineering “smarts” by checking your preliminary results with others – especially experienced engineers. This is utilizing your common sense and goes together with good engineering judgment – both are characteristics of successful professional engineers. I congratulate you for showing good judgment – up to now.

As I stated, I see no reason for employing any insulation on a normal TEG absorber vessel – especially one located on a platform. The weight factor doesn’t bother me; that is not a real serious cost factor as compared to the amount of platform space you will save upon deleting it. I know you must think that the insulation doesn’t amount to much space, but I can assure you that what you have to design for just to have the vessel insulated will cost a lot of money due to the extra platform space required to accommodate and maintain the insulation. You will save your project a lot of problems and money by deleting this need. However, now that you have furnished more details on your project, read my comments below. You may just need insulation - it depends.

I don’t know what you mean by “what would be the standard specifications of an absorber”. I believe you would have already simulated or calculated the diameter and height of the vessel (the process design) – as well as all the mechanical design details. I also don’t know what you mean by “water content: 30 lbs/MMSCF”. Is that the specifications for the wet gas ENTERING the absorber or the product, dry gas EXITING the absorber? I recommend that you be very specific in your descriptions and definitions in your project report. Your profs should really get very grouchy if you report something like that.

Keep up the good work on your checking your results. Use your common sense – for example, now that you reveal that the absorber will operate at 80 ^oF, you can see that I and anyone else would not consider any insulation being required. HOWEVER, since you now also reveal that your project is for the Troll field – which I believe is in the North Sea – don’t you think that you should be considering insulation for protecting the process from freezing? You know more about your basic data since you have not given us very much to work on, so I would really have a hard look at the worst ambient conditions on your platform. You may require insulation, but not for the normal reasons. You may need Freeze protection insulation and if so, then you may also need heat tracing. These are the details that can really give you a bad mark before the project judges should they suddenly quiz you on whether or not you allowed for climatic forces on your project. Be careful and study ALL the details - especially those locations where you can form hydrates due to low temperatures.

Do you understand now why it is so important to tell ALL of your story from the very beginning?

Good luck!

[aljabi]

Thank you again for the reply! and i thank you for the support.

The design is carried out for an onshore process, since there is already a pipeline and a gas treatment facility operating in that manner. Hydrate formation occurs at a temperature of 59 F and is dealt with inhibitors.
My main worry is the design of the absorber. For example when I was designing a horizontal separator i manged to find standard sizes (length and diameter) of standard horizontal/vertical separators. I haven't been able to find the same for an absorber. The dimensions of the absorber calculated are as follows:

Diameter: 8.8 ft
Height: 16 ft
Thickness: 1.77 in = 45 mm
Ellipsoidal head thickness: 1.67 in = 42.5 mm

so basically i have these values and nothing to compare with to check whether or not this is the most efficient design.

[gvdlans]

Did you check out the Norwegian NORSOK standards, such as P-001, P-100 and R-004?

http://www.standard....704_0/R-004.pdf