5 replies to this topic

[SUPRIYAPRA]

Hi all;

 

We have crude oil storage tank with storage temperature of 72 degree centigrade.

 

In Hysys simulation; the Oil RVP and TVP shows only at 100 degree F.

 

If we want to calculate at TVP and RVP at 72 degree centigrade; how to calculate on HYSYS?

 

If somebody put light; than thankful.

Regards

Dhiren

[fseipel]

Set the vapor fraction to zero for the stream being assessed.  The bubble point pressure calculated will be the true vapor pressure (TVP) at the temperature of interest.

[SUPRIYAPRA]

Thanks. But Oil product stream has already zero vapor fraction. and in Hysys--tools---utilities--cold properties shows same TVP.,

Can you further input?

 

Reg

Dhiren

[PaoloPemi]

as said by fseipel TVP (true vapor pressure) shows the bubble point pressure at specified temperature,

RVP (Reid vapor pressure) shows values which are easier(compared to TVP)  to measure (with instruments),

(you may consider a textbook as Charaterization and properties of petroleum fractions for the difference between True and Reid vapor pressure)

With a simulator TVP and RVP are calculated from mixture composition generated with characterization

and the accuracy of calculated values depend from that.

Generally a software should calculate different values for RVP and TVP but that depends from included procedure.

In your case once the mixture composition has been defined

a simulator (these utilities are avilable in almost all petrochemical simulators) should be able

to calculate bubble point temperature (given a pressure)

or bubble point pressure (given a temperature),

from your comment it seems that you are calculating bubble point temperature (given the operating pressure),

and the calculated value (calculated 100 F vs. operating 72 F) shows that you are

below bubble point temperature (stabilized liquid phase) which is correct.

Is that true ?

Edited by PaoloPemi, 20 August 2013 - 02:36 AM.

[paulhorth]

Dhiren,

 

The method given by fseipel is correct. The other method, given by Propacket in your other thread in the Refining forum, is also correct.

 

In Hysys there is a difference between a stream having zero vapour fraction when the temperature and pressure are both specified - as in your oil storage stream - and having the vapour fraction SPECIFIED  as zero, with the pressure not specified but calculated. This is what fseipel is suggesting, and is what I always do, to find the vapour pressure of any stream at a given temperature. By specifying the vapour fraction as zero, you are telling Hysys to find the exact condition at which vapour starts to form - that is, the bubble point.This is the TVP at the stream temperature.

 

Paul

[SUPRIYAPRA]

Thanks For your support and genuine advise.

 

Dhiren