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[mubby]

Dear all,

I am a new process engineer at designing and fabrication company. I try to simulate knockout vessel and 3-phase separator in hysys but i am confused in some matters.
1- when I give the compostion of natural gas then should I add water in separate stream? or i give the composition of water in natural gas stream?
2-When I give the required compostion on outlet streams then hysys give consistency errors?
3- By changing the size of the separator there is no effect on the outlet stream compostion?

I really appreciate any help, Thanx in advance.
Mubby

[Zauberberg]

Hysys assumes ideal separation in 2-phase and 3-phase vessels, where only equilibrium concentrations of light liquid phase in heavy liquid phase (and vice versa) exist. It is not possible to predict actual carryover and carry-under by using simulators. To model any existing vessel where the amounts of carryover and carry-under are known, you can use the CO option in the vessel window and specify any values you want.

1. It all depends on whether you have any free liquid (water) in the gas stream, or not. If it is liquid-free, water-saturated gas at process conditions, you don't need to add any extra liquid stream. But make sure that you have properly specified the amount of water vapor in the gas.

2. If the feed gas stream composition is specified, you cannot specify composition of the outlet streams. It is automatically calculated by Hysys.

3. As said above, Hysys assumes ideal separation between phases in all cases. You don't use Hysys for vessel sizing. You should use some other tools, and all of them are based on Souders-Brown equation.