1. Hydrocarbon Liquid Potential: Gallons Per MSCF (GPM)
The theoretical liquid recovery potential for any hydrocarbon component \(i\) is evaluated using its ideal gas molar volume and liquid density:
\[ \text{GPM}_i = y_i \times \frac{1,000 \text{ SCF}}{379.482 \text{ SCF/lbmol}} \times \frac{MW_i}{\rho_{L,i} \text{ (lb/gal)}} \]
Where \(y_i\) is the inlet gas mole fraction, \(MW_i\) is molecular weight, and \(\rho_{L,i}\) is liquid density at standard conditions (60°F / 14.696 psia per GPA 2145).
2. Plant Volumetric Shrinkage & Residue Gas Flow
As heavier hydrocarbons are liquefied and recovered into the NGL product, the gaseous sales volume is diminished. The gas equivalent volume of extracted liquid is calculated by converting liquid production back to standard vapor volume:
\[ \Delta Q_{shrink} = \sum_{i} \left[ \dot{n}_{liq,i} \times 379.482 \right] \qquad Q_{residue} = Q_{inlet} - \Delta Q_{shrink} - Q_{fuel} \]
The volumetric shrinkage factor is \(S_f = \frac{Q_{residue}}{Q_{inlet}}\).
3. Residue Gas Energy Derating
Because extracted heavier components have much higher volumetric heating values than methane (e.g., Propane: 2,516 BTU/SCF vs Methane: 1,010 BTU/SCF), residue gas experiences gross calorific value derating:
\[ HHV_{residue} = \sum_{i} y_{res,i} \cdot HHV_i \qquad \Delta HHV\% = \frac{HHV_{in} - HHV_{res}}{HHV_{in}} \times 100\% \]
4. Condensate Stabilizer Column Hydrodynamics
To produce stable condensate with a Reid Vapor Pressure of 9 to 12 psia (safe for floating roof tank storage and marine transport), the stabilizer tower strips methane, ethane, and propane over 20 to 24 valve trays:
\[ T_{reboiler} = f(P_{col}, RVP_{target}) \qquad P_{col} = P_{condenser} + \Delta P_{trays} \]