Hydrates in de-ethanizer

[MortenA]

Im looking at a conceptual project involving a de-ethanizer to lean out a rich gas.

Are hydrates in the gas a problem following the cooling of the gas?.

If the gas e.g. have a water dew point of -8ºC and the inlet stream gets cooled to -20ºC - would the water that is freed and the hydrates that may form actually cause problems or would they tend to stay in the liquid phase and "melt" in the hotter zones of the collumn? I havent checked the theoretical hydrate formation temperature at the actual operating pressure but i think that we are within the regio whre hydrate will form

Best regards

Morten

 

[dcasto]

If you continue to cool a gas stream below the water dew poit, Water will condense and freeze. You either need to add inhibitor or dry the gas more.

The inhibitor of choice is ethylene glycol that will absorb the water and can be decanted, regenerated, and reused. On very small systems, methanol can be injected and lost to the system.

Some water does get by and can end up in deethanizers. If this is a normal refluxed deethanizer, the water will end up in the reflux drum and will freeze. Most dethanizers have spray nozzels on the overhead condensors to spray methanol to remove hydrates that build up overtime.

 

[MortenA]

So the best solution would be to make sure that the water dew point was e.g. below -25 or whatever low temperature predicted? A TEG unit should be able to do this - but the spec allows high dew point.

Best regards

Morten

 

[dcasto]

The only way the get that low of dew point with TEG is either a stahl column or the Drizo process.

 

[gosooners]

MortenA,

dcasto is right, you required Drizo process to dehydrate the gas and to recover 99.99% TEG purity. We have drizo process and able to achieve -70 F dewpoint measured at std condition condition.