Methanol Injection Inline Gasheater

[Pulpeng]

We are trying to take out of service an inline gas heater to our plant for a really overdue inspection without shutting down the plant. We tried injecting methanol to prevent the freezing of control valves etc but to no avail.

Does anyone have suggestions - maybe we didn't inject enough, what calc would you use?


Incoming natural gas is about 7900 KPA (1150 PSI) at a controllable max flowrate during servicing of about 120 m3/min with our peak being above 600 m3/min although we should be able to negate the high flows.

Reduced to 1714 (250 PSI)
Second reduction to 354 (50 PSI)

Is there something else injected to prevent freezing? Does anyone know a better calculation to predict methanol amounts? We were just injecting before the first let down - maybe we should inject after? Any suggestions would be appreciated.

Thanks

 

[dcasto]

The GPSA databook has a goo section on the use of methanol and ethylene glycol as hydrate inhibitors. For your case it looks like you need to add the same mass of methanol as you have of water in the gas.

You can rent portable heaters of the size you own.

 

[Unotec]

See if this helps:

http://www.nugentec.com/FAQ/Freezing Point Flash Points.htm

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[dcasto]

pulpeng, the table from unotec is for a complete homogenious mixture and does not take into account mixing rates ect. The GPSA book has emperical formulas taken from real data.

 

[wmarais]

It seems like you have Hydrate problems, TEG, MEG, Methanol are the most common used hydrate inhibitors. Methanol is by far the most effective one, the only problem is that you will have to inject a lot of it. Rule of thumb for this is about 25% by weight of the total water production of the line. There are other hydrate inhibitors available (kinetic, anti agglomeration chemicals) but I wouldn't go into those right away.

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