4 replies to this topic

[guoyinyanliner]

The LNG liquefaction cold box may experience freezing and blockage due to the high heavy-hydrocarbon content. Using Aspen HYSYS, we can evaluate whether the natural gas with a given composition will freeze or plug. Thank you, my friend.

[breizh]

Hi,

I don't know what you are asking !

Anyway I post a youtube video about Hydrate formation.

Hydrate Formation Analysis Using Aspen Hysys

 

Breizh

[Fletch]

HYSYS will not predict freezing or plugging of the LNG exchanger or freezing in general as it isn't a solid-liquid equilibrium simulator.

 

Most LNG technology providers or operators have key feed gas specifications for heavy hydrocarbon (C5+) limits to ensure that the potential of tube blockage is avoided.

This would be established on their experience and ensuring they provide good margin to protect their performance guarantee.

 

These heavier hydrocarbons are manged in the scrub column prior to entering the liquefaction system. 

[Pilesar]

Hysys has an inherent calculation method for Hydrate prediction. It is good implementation compared to the other steady state computer programs. Hysys historically was developed toward the natural gas industry as it was originally Canadian. Hydrates are not simple molecules and prediction is tricky. The calculation method estimates the temperature at which hydrates might form if there were a little bit of water available in the stream. It is much easier to avoid hydrate formation than to try to get rid of them once they are formed. 

[Pilesar]

The hydrate calculation method is not the normal solid-liquid equilibrium. Various types of hydrates can form well above the freezing point of pure water and can form in very light hydrocarbon mixtures. Hysys, Pro/II, and AspenPlus each have a different procedure from the others to calculate hydrate temperature. I have also used a fourth method derived from outside research which I converted to spreadsheet code. When designing cryogenic plants, I made sure to always stay at least a few degrees above the predicted hydrate temperature prior to the molecular sieve.