3 replies to this topic

[Karim kimo]

Hello

 

I am simulating a deethanizer tower with 32 bar operating condition , which is coming from a pump with Discharge pressure of 38 bar 

the feed tray is almost at the top of the tower , and the tower is high ( the feed tray is nearly at 35 m height )

I think this height will affect my simulation results as there is no way in HYSYS to include these tall heights and it is SURE will make a gravitational head against the feed stream pressure 

 

I ask , what Pressure can i put in the feed stream condition in hysys  ( it will be 37>P>32 BAR )  and it is a wide range 

also , Is there a way i can easily enter the feed line dimensions ( including diameter ,height , elbows ) without using pipe segment ??

 

thanks in advance

 

 

 

 

[Pilesar]

Column pressure is not controlled by the pressure of the feed. The feed pump discharge pressure does not affect the pressure at the feed tray of the tower even if the pump has 100 bar discharge pressure. In the real world, the pump discharge pressure will be higher than required by gravity and pipe friction. There will be a feed control valve downstream of the pump to regulate flow. This valve needs the extra pump pressure to be able to control the flow by modulating the restriction through the valve.

[Karim kimo]

Totally agree

But this is not my point

I ask ( which pressure value will i put to the feed stream entering the column (35 ? 33? ... ???? )

 

as the line in real world is about 100 m long "horizontal + vertical + elbows "

and in all case the column pressure i will put 32 bar already 

Column pressure is not controlled by the pressure of the feed. The feed pump discharge pressure does not affect the pressure at the feed tray of the tower even if the pump has 100 bar discharge pressure. In the real world, the pump discharge pressure will be higher than required by gravity and pipe friction. There will be a feed control valve downstream of the pump to regulate flow. This valve needs the extra pump pressure to be able to control the flow by modulating the restriction through the valve.

[Pilesar]

Set your feed stream pressure higher than the column feed stage pressure. It just will not matter at all to the column simulation. You do need to know the energy in the feed stream. For example, does your feed come from the bottom of a demethanizer? If so, then set the feed stream conditions using the pressure at the demethanizer sump and the bubble point temperature. For your deethanizer column simulation, the temperature, pressure, vapor fraction, composition will define the feed stream. For a mixed stream, you can specify only two of temperature, pressure, vapor fraction. After your stream is specified, put it through a pump if you need to get the pressure higher to avoid column warnings. Make the discharge of the pump higher than the column and then get your column converged. Don't be concerned about the hydraulics of the feed if you are just trying to simulate the distillation column. Just connect the outlet of the pump to the distillation column without any pressure drop unit operations. If for some reason you are sizing piping or control valves or designing the pump, then you would put the physical piping details into a model. There is no good reason to have to do the hydraulic calcs in the same model as the distillation column and it would be easier to use a separate model if you want to calc hydraulics.