Methyl Hydrate Formation in Natural Gas Pipeline

[RPG]

In a natural gas pipeline system, we are taking 1200 psig methane at 40 degrees F and wil be dropping it to 480 psig, which we calculated will be -6 degrees F. Is formation of Methyl Hydrate in the pipeline of any concern? All the literature that I have read on methyl hydrate does not really answer the question, it says that it may happen but gives no information beyond that. Any help will be appreciated.

 

[25362]

There is quite a number of Google sites dealing with methane (not methyl) hydrates. I hope one of them will satisfy your query.

 

[RPG]

Sorry for the error, I meant Methane Hydrate. I have already spent quite some time checking out the sites.

 

[MortenA]

It seems likely that hydrates will form in your gas stream. If you are worried you should carry out a flow assurance study. If you do not have the knowledge your self then find somebody in your company who can or hire a consultant.

Best regards

Morten

 

[RPG]

I guess the biggest question that I have is, how much moisture is necessary to be in the natural gas to get the Methane Hydride to form? The stream is not coming from a well, but coming from a gas distribution header.

 

[MortenA]

RPG

Its a common misuderstanding that hydrates (i assume thats what you refer to when saying methane hydrides) require the presense off free water. Thermodynamically this is not true. It should however be noted that the formation temperature drops radically at low water partial pressures. There may also be large diffirences in the physical properties. The crystals might be small and tend not to stick for "dry" gasses (meaning gasses with some water but significantly warmer that their water dew point).

Best regards

Morten

 

[25362]

To name just two sites that may be helpful:

http://www.feesa.net/pdf/Discussion Papers/010918 - Evaluating Hydrate Inhibitors - Rev A.pdf

http://www.flowcontrolnetwork.com/PastIssues/novdec2000/2.asp

 

[MortenA]

25362

its a nice link. Among the references one should especially note Sloan, E.D.: Clathrate hydrates of natural gases.

Its a very expensive book (200 pounds as far as i remember) but its also THE reference on hydrates.

Best regards

Morten

 

[RPG]

I appreciate everyones responses. I now know more about Methane Hydrate than I ever thought I would. The link to the feesa site was very helpful. Thanks!