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API Separator Sizing Macro-Enabled Excel Spreadsheet Calculator

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API Separator Sizing Macro-Enabled Excel Spreadsheet Calculator

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1. Discussion
2. Nomenclature
3. References
4. Standard Separator Sizes as per API
5. Separator sizing with mist extractor
5A. Two Phase (Gas - Oil) Vertical Separator as per API 12J
5B. Two Phase (Gas - Oil) Horizontal Separator as per API 12J
5C. Three Phase (Gas - Oil - Water) Vertical Separator as per API 12J
5D. Three Phase (Gas - Oil - Water) Horizontal Separator as per API 12J
6. Separator sizing without mist extractor
6A. Two Phase (Gas - Oil) Vertical Separator As per Petroleum and Gas Field Processing
6B. Two Phase (Gas - Oil) Horizontal Separator as per Petroleum and Gas Field Processing
6C. Three Phase (Gas - Oil - Water) Vertical Separator as per Petroleum and Gas Field Processing
6D. Three Phase (Gas - Oil - Water) Horizontal Separator as per Petroleum and Gas Field Processing

This spreadsheet provides an easy and simple approach to (2/3 phase and vertical/horizontal) separator sizing. Formulae and references are also provided for process engineers to edit/duplicate this work (file is NOT password protected).

There is as much art as there is science to properly design a separator. Three main factors should be considered in separator sizing: 1) vapor capacity, 2) Liquid capacity, and 3) operability. The vapor capacity will determine the cross-sectional area necessary for gravitational forces to remove the liquid from the vapor. The liquid capacity is typically set by determining the volume required to provide adequate residence time to “de-gas” the liquid or allow immiscible liquid phases to separate. Operability issues include the separator’s ability to deal with solids if present, unsteady flow/liquid slugs, turndown, etc. Finally, the optimal design will usually result in an aspect ratio that satisfies these requirements in a vessel of reasonable cost. These factors often result in an iterative approach to the calculations.

Two sets of calculations are carried out here. 1. Separators with Mist Extractors and 2. Separators without Mist Extractors

Nomenclature
A total cross sectional area of the separator.
A w cross sectional area of the separator occupied by water, ft 2
A o cross sectional area of the separator occupied by oil, ft 2
A g cross sectional area of the separator occupied by gas, ft 2
C D drag coefficient
d vessel internal diameter, in.
d m bubble or drop diameter, μm
D vessel diameter, ft
h liquid height, in.
h g gas-phase space height, in.
h o oil pad height, in.
h w water pad height, in.
K mesh capacity factor, ft/sec
L eff or L effective length of the vessel where separation occurs, ft
L ss or L s seam-to-seam vessel length, ft
N LL normal liquid level, %
P operating pressure, psia
Q c continuous liquid-phase flow rate, bbl/day
Q g gas flow rate, MMSCFD or ft 3 /s
Q o oil flow rate, bbl/day
W or Q w water flow rate, bbl/day
Re Reynolds number
T operating temperature, °R
V liquid settling volume
V a max. allowable velocity through secondary separation section
V m velocity of the mixture, m/s
Z gas compressibility
μ c continuous phase dynamic viscosity, cp
μ w water dynamic viscosity, cP
ρ density, lbm/ft 3
ρ g gas density, lbm/ft 3
ρ l liquid density, lbm/ft 3
ρ o oil density, lbm/ft 3
ρ m mean density of mixture, kg/m 3
ρ w water density, lbm/ft 3

Credit: Ajay S. Sutpute
M. Tech.
Indian institute of Technology

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