exporting gas from a platform.

[eng9901375]

Why is it essential to dehydrate gas before it is compressed and exported from the platform?

Also, what special considerations must be given to the design and operation of the gas export pipeline if the gas contains substantial amounts of carbon dioxide?

 

[ICman]

1. Water and gas condensate mean you are changing your compressor into a pump. Not a good idea.

2. Liquids will foul small orifices and nozzles and sometimes block gas flow.

3. Biggest reason: CORROSION. Water causes rust. Water and CO2 form carbonic acid - very detrimental to steel and iron. If you keep it dry, you should not have any major corrosion problems. You could also lay stainless steel lines, but you would be foolish to do so (expensive!!!).

You want to dehydrate the gas before it enters the compressor to reduce the amount of corrosion in the compressor and in order to operate the dehy process at a lower pressure (cheaper design).

 

[Fausto]

Hi,

Besides all the reasons given by ICman, there is another
one that I would add to the list: gas hydrates may form in
the line under certain conditions should water condensates
in it.

There are other transportation issues: liquid may condensate
and settle in the "valleys" of a flowline on hilly terrain,
should the gas flow rate is not high enough to keep
carrying/dragging the condensed liquid. That might lead to
undesirable transient phenomema (such as terrain slugging)
and, from the purely "mechanical" point of view, the
accumulation of stagnant liquid is a source for corrosion.

Hope that has helped.

---Fausto

 

[Nosey]

This is the same as

thread470-54484