Sand Separator Calculations

[amarks]

Hello,

Does anybody have any experience with sizing sand separators (a.k.a. Sand Knockouts or desanders) and what calculations are needed?

Assuming a well flowing back at 10,000 psi, 100 deg F, 75 MMSCFD, 7 lbs/hr sand. These are arbitrary numbers, just trying to get an idea of what we need.

 

[1503-44]

Typical design method attached



--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[amarks]

1503-44 - Fantastic paper, thank you for sharing.

Was working down through the equations and was curious when finding Vgmax is it safe to say the gas and liquid densities are their Specific Gravities?

Also when solving for Dmin what units are qa - gas flow in?

Thanks again for the references.

Alex

 

[1503-44]

Density of the gas at STP = SG of the gas x Density of Air at STP

Density of the gas in these calculations are at actual flowing pressure and temperature at any point of interest inside the pipe. So you use an equation of state to convert densities from STP conditions to actual conditions.

VP = nRT/z

https://en.m.wikipedia.org/wiki/Equation_of_state

Units must be consistent. Put your units into the calculation along with the numbers and the diameter will be whatever unit is left (does not cancel out). Normally they will be ...
If you have a gas flow in m3/s, velocity should be m/s, thus diameter will be in m
If gas is MMSCFD, then convert to ft3/day , velocity is ft/day and d is ft.
If gas flow is ft3/s, v is ft/s then diameters will be in feet.


--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."