3 replies to this topic

[SUPRIYAPRA]

Oil shall be stabilized based on RVP or TVP?

 

Which is important in oil stablization?

 

TVP includes air and CO2 while RVP gives only vapour pressure of hydrocarbons.

But in stablization project specification which is important one?

RVP or TVP?

 

Specification

Unit

Value

TVP

bara

0.76

RVP, max

bara

0.69

BS&W, max

vol%

0.5

Salinity, max

PTB

25

Can somebody put the light of knowledge please?

 

Regards

Dhiren Shah

[paulhorth]

Dhiren,

TVP means True Vapour Pressure, and it shoul be quoted at a stated temperature. Like any liquid, the vapour pressure of crude oil depends on its temperature. So the TVP at 50 C will be higher than that at 25 C, just like for water. You say the TVP "includes air and CO2". I don't know what you mean by this. Crude oil leaving the bottom of a stabilising column will not contain any CO2 and certainly no air. So the TVP is the true vapour pressure of the hydrocarbons in the oil. It is an ABSOLUTE pressure not a gauge pressure.

 

RVP is something different. It means Reid Vapour Pressure, and it is the result of a standard test procedure carried out, always, at 100 F (37.8 C) . This test starts with a vessel containing the sample and air, so the reading on the test gauge after heating and agitation is a GAUGE pressure, that is, above atmospheric. The reading is taken as an approximate measure of the vapour pressure of the sample at 100 F, added to the air which was at one atmosphere.

 

The two values are not the same, even at the same temperature, because the RVP procedure is different from the rigorous lab measurement for TVP. The RVP value is used as a standard for shipping and storage of stabilised crude because it is a simple test to carry out without a lab and uses standard repeatable conditions.

 

So to answer your question - both RVP and TVP are important for specifying crude quality, but RVP is at 100 F while TVP can be at any temperature (usually the relevant temperature is the maximum storage temperature which can be as high as 50 C).

 

Paul

[SUPRIYAPRA]

Hi Paul;

 

Thanks for your reply.

 

If we carry out simulation on Hysys; it show RVP and TVP at 100 degree F; but our actual storage system is at 72 degree centigrade.

 

So how we can exptrapolate this TVP to get at 72 degree centigrade.

 

Request to put light on this.

Regards

Dhiren Shah

[Propacket]

If you have access to Hysys, generate a new stream using Balance unit operation. Apply molar balance, put your desired temperature and make the vapor fraction equal to "zero". This will give TVP at your desired temperature.