EmmanuelTop
Chemical
- Sep 28, 2006
- 1,237
Good day to everybody,
1) Equation for terminal velocity in a vertical wiremesh separator contains the square root of (DL-DG)/DG. It means that, as pressure increases, the maximum allowed terminal velocity will decrease, due to increase of gas density with pressure. Again, this means, that for the same actual volumetric flow, the required demister area will be higher at higher operating pressure. Why the efficiency of a demister pad depends on relative density, since the working principle of a demister pad is not gravity separation?
2) K-value. GPSA says that K-value needs to be de-rated for any pressure above 100 psig. Now, the pressure factor has already been taken into account with gas density changes in the terminal velocity equation. Are we actually de-rating the K-value twice this way, if we both include gas density increase with pressure (which reduces the maximum allowed velocity), and in the same tame reduce the K-value itself according to de-rating criteria for higher operating pressure (which reduces the maximum allowed velocity even further)?
I have heard a lot of different thoughts on these subjects. Would appreciate to hear yours.
Best regards
1) Equation for terminal velocity in a vertical wiremesh separator contains the square root of (DL-DG)/DG. It means that, as pressure increases, the maximum allowed terminal velocity will decrease, due to increase of gas density with pressure. Again, this means, that for the same actual volumetric flow, the required demister area will be higher at higher operating pressure. Why the efficiency of a demister pad depends on relative density, since the working principle of a demister pad is not gravity separation?
2) K-value. GPSA says that K-value needs to be de-rated for any pressure above 100 psig. Now, the pressure factor has already been taken into account with gas density changes in the terminal velocity equation. Are we actually de-rating the K-value twice this way, if we both include gas density increase with pressure (which reduces the maximum allowed velocity), and in the same tame reduce the K-value itself according to de-rating criteria for higher operating pressure (which reduces the maximum allowed velocity even further)?
I have heard a lot of different thoughts on these subjects. Would appreciate to hear yours.
Best regards
