Fire case - Latent heat for multicomponent system

[sheiko]

Hello,

Im currently sizins RVs for fire case. Last but not least thing that is missing is the latent heat of vaporization.
Unfortunately i have a multicomponent systems: acid gas condensates (H20, H2S at 9wt% max, NH3 at 12 wt% max), lean MDEA with 30wt% water, rich MDEA at max 0.6 mol% namely.

1/ Generally what is the most rigorous methodology to determinate the latent heat of vaporization for multicomponent systems?

2/ How can i simplify this specific problem?


"We don't believe things because they are true, things are true because we believe them."
"Small people talk about others, average people talk about things, smart people talk about ideas and legends never talk."

 

[sheiko]

3/ In addition, i have read that the methodology used to calculate the latent heat differs depending if the HC mixture is narrow boiling range or high boiling-point range: How to know in which category i am? what is the temperature criteria or where to find it?

"We don't believe things because they are true, things are true because we believe them."
"Small people talk about others, average people talk about things, smart people talk about ideas and legends never talk."

 

[SeanB]

The easiest thing to do is to input your compostion into a simulator such as HYSYS.

 

[sheiko]

What about item 3/?

"We don't believe things because they are true, things are true because we believe them."
"Small people talk about others, average people talk about things, smart people talk about ideas and legends never talk."

 

[Bill3752]

A couple of options you may want to consider:
1. Choose the component with the lowest Hvap.
2. Run a flash calculation. Flash a small amount (1%) and determine the Hvap of that fraction.
3. Someone a while back suggested calculating the RV area for each component independently, and use the most conservative area.
4. At close to the critical point (i.e. Hvap approaches zero, use 50 Btu/lb.
Good luck.

 

[CHD01]

The latent heat of a mixture is equal to the sum of each component latent heat multiplied by its mass fraction.

The more you learn, the less you are certain of.

 

[JoeWong88]

One of the difficult issue here is using a correct thermodynamic model to predict correctly the mixtures properties.

If you have found a "good" thermodynamic model then you adopt the princinple suggested in "Determine Latent Heat for Multi-Component and Relieving Area Using Rigorous Method in HYSYS" to size the PSV.

Point to highlight "the maximum relieving area for PSV may not occur at the beginning of flashing although majority fluid are".



JoeWong
Chemical & Process Technology

 

[CHD01]

Joe is correct that first you must understand the mixture and whether seperation will occur for lower boiling components for example.

The more you learn, the less you are certain of.