Gas capacity of a separator is the maximum volume or flow rate of gas that a separator can effectively handle while performing its primary function: separating gas from liquid (oil, water) in a mixture. This capacity is typically determined by the design and size of the separator, as well as operational conditions like pressure, temperature, and the properties of the gas and liquid involved.
Key Points about Gas Capacity of a Separator
Separator Size and Design - The internal structure (baffles, mist extractors) and dimensions (diameter and length) influence how much gas can be processed without overwhelming the system. Larger separators with features like mist extractors can handle more gas.
Operating Pressure - Higher pressures can compress the gas, allowing more throughput, while lower pressures may limit capacity. Higher pressure compresses gas, increasing capacity; lower pressure reduces it.
Gas Velocity - The speed at which gas moves through the separator must be controlled to avoid carryover (gas carrying liquid droplets out of the separator). This is often tied to a maximum allowable velocity. Must stay below a maximum (set by the Souders-Brown equation) to avoid inefficiencies.
Liquid Load - The amount of liquid in the mixture affects how much gas can be separated efficiently. More liquid in the mix can lower the gas-handling capacity.
Gas Capacity of a Separator Formula |
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\( Q_g \;=\; 67824 \cdot K_g \cdot d^2 \cdot F \cdot \dfrac{ 1 }{ Z } \cdot \dfrac{ P }{ p_b } \cdot \dfrac{ T_b }{ T_a } \cdot \left( \dfrac{ \rho_l - \rho_g }{ \rho_g } \right)^{0.5} \) |
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| Symbol | English | Metric |
| \( Q_g \) = Gas Rate | \( ft^3 \;/\; day \) | \( m^3 \;/\; day \) |
| \( K_s \) = Separator Coefficient | \( ft \;/\; sec \) | \( m \;/\; s \) |
| \( d \) = Total Interior Dia. of Separator | \(ft\) | \(m\) |
| \( F \) = Fraction of Total Area Available to Gas | \(dimensionless\) | \(dimensionless\) |
| \( Z \) = Compressibility Factor | \(dimensionless\) | \(dimensionless\) |
| \( P \) = Separation Pressure (psi) | \(lbf \;/\; in^2\) | \(Pa\) |
| \( p_b \) = Base Pressure (psi) | \(lbf \;/\; in^2\) | \(Pa\) |
| \( T_b \) = Base Temperature | \(F\) | \(K\) |
| \( T_a \) = Absolute Separation Temperature | \(F\) | \(K\) |
| \( \rho_l \) = Liquid Density | \(lbm \;/\; ft^3\) | \(g \;/\; cc\) |
| \( \rho_g \) = Gas Density | \(lbm \;/\; ft^3\) | \(g \;/\; cc\) |
