5 replies to this topic

[go-fish]

I am trying to estimate latent heat of vaporization for a crude assay for the purpose of relief load calculation in external fire scenario.

Since, crude assays do not have a fixed boiling point, I am trying to solve the problem using Pro II simulation. I am modelling a simple HE with inlet cold stream at atmospheric pressure and initial boiling point (assuming IBP as saturated liquid temperature). On HE specification, I am increasing my cold fluid outlet temperature in small increments until I get a mixed phase at the outlet. I am dividing the heater duty thus obtained by inlet mass flow to get latent heat.

Is my approach correct?

[Zauberberg]

The actual latent heat will vary by time/heat input since the crude oil consists of thousands of different components. I would suggest you to play with the model and see at what temperature the crude oil will have the same mixed phase density (at relief pressure) as it is at bubble point (at atmospheric pressure). You will obtain the relief temperature that way as well.

See attached file - some other interesting information can be found there.

Attached Files

•  Thermo - Guide against Misconceptions.pdf   461.01KB   306 downloads

[deltaChe]

You may use two flash drum to simulate to get the result, The first flash drum with vapor \ liquid outlet , and in liquid outlet, assue 5% water vaporized and enter to the second flash drum.
And, then find out the enthalpy of the vapor stream in the second flash drum, minus that enthply to the
the enthalpy of the liquid stream will get the latnet heat.

[Padmakar Katre]

Hi,
Hi where you want to caluclate the relief load? Please specify the equipment where you have the PSV for fire case. In case of column I would suggest you to run the column at the PSV set pressure or column design pressure with an additional dummy energy stream with the heat flow equal to the calculated by the API-520/521. It will give you the PSV relieve load. The analysis of the system can be done for fire case scenario based on detailed information given to users here, which is lacking in your post. Please give us the background of the system so that we can make you understand better.

[ChemDare]

Hi,
Hi where you want to caluclate the relief load? Please specify the equipment where you have the PSV for fire case. In case of column I would suggest you to run the column at the PSV set pressure or column design pressure with an additional dummy energy stream with the heat flow equal to the calculated by the API-520/521. It will give you the PSV relieve load. The analysis of the system can be done for fire case scenario based on detailed information given to users here, which is lacking in your post. Please give us the background of the system so that we can make you understand better.

What If the PSV is on 3-phase separator (HC condensate/HC Gas and water) or on a vessel ?

[ChemDare]

I am trying to estimate latent heat of vaporization for a crude assay for the purpose of relief load calculation in external fire scenario.

Since, crude assays do not have a fixed boiling point, I am trying to solve the problem using Pro II simulation. I am modelling a simple HE with inlet cold stream at atmospheric pressure and initial boiling point (assuming IBP as saturated liquid temperature). On HE specification, I am increasing my cold fluid outlet temperature in small increments until I get a mixed phase at the outlet. I am dividing the heater duty thus obtained by inlet mass flow to get latent heat.

Is my approach correct?

i m also estimating the latent heat in a similar way in HYSYS, but my approach is to consider a HE with inlet stream at relieving pressure and normal operating temp and I am increasing my cold fluid outlet temperature in small increments until I get a mixed phase at the outlet (having 3 to 4 % vapor in the outlet on conservative side) and then I am dividing the heater duty thus obtained by inlet mass flow to get latent heat.

is this approach ok?