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Three-Stage Hydrocarbon Separator Train Calculator

Remove vapor at three prescribed PT stages, carry only liquid forward and check overall component and interstage energy balances.

Inputs

Results

Calculate to view linked results. Default values are examples, not recommended operating inputs.

Learn, compare and practice

Worked explanations, controlled studies and printable exercises connected to this calculation.

Explore separator pressure and phase split on one synthetic feed

Calculation sequence

  1. Enter the original C1-C6 feed and three strictly decreasing absolute pressures with three prescribed equilibrium temperatures. This is a PT separator train, not three adiabatic valves. Stage 1 defines the original equilibrated feed state; its upstream heater/cooler duty is outside the calculation boundary.
  2. Flash stage 1, remove its vapor stream and carry the liquid composition and molar flow to stage 2. Repeat for stage 3. Require a resolved vapor/liquid split at each stage; no all-vapor stream is silently treated as liquid carry. Each stage is checked against its actual changed feed composition.
  3. Compute interstage conditioning heat using each incoming liquid's enthalpy on the common species reference. Compare total released vapor plus final liquid component moles with the original feed. Report heat per original feed mass, not per final liquid mass or per stage feed mass; the sample table states its molar denominators explicitly.
  4. At every returned state independently re-evaluate classical PR pressure, log fugacity and residual enthalpy/entropy. Require component balance <=2e-7, log-fugacity mismatch <=2e-5 and relative pressure residual <=2e-6. Reject vanishing phase fractions below 1e-6 and density separation below 1.1 for ordinary splits. These are numerical checks, not measured-PVT validation.
  5. Calculations run locally in a dedicated WebAssembly worker. The advanced Python/scientific engine is a roughly 33 MB first download, separate from ordinary calculators; it is self-hosted and version pinned. No composition or measurements are sent to a calculation server. Save and file backups retain canonical inputs, while CSV/PDF include returned tables and source notes. The worker is released after idle time and failures never return partial results.

Worked check

For the synthetic default 5/2/0.5 MPa and 330/300/280 K train, total vapor recovery is about 0.809756 mol per original feed mole and final liquid is 0.190244. Interstage conditioning removes about 28.787578 kJ/kg of original feed. Component and energy residuals are checked; this is not an equipment design or measured recovery test.

Synthetic examples for reproducibility, not measured field results.

Assumptions and limitations

  • Six components C1-C6, normal C4-C6, classical PR and all kij=0. No water, isomers, sour gas, heavy fractions, reactions, solids or volume translation. Use the expanded-mixture tools for their explicitly supported alternatives, not by inserting a new species in these fixed feed slots.
  • Every flash trial must remain at 180-450 K and 0.1-10 MPa absolute, with consistent mole fractions summing to one. Near-critical, vanishing-phase or failed closure states are rejected. Single-phase states are not given an invented vapor quality. Independent engine agreement is not experimental validation.
  • Instantaneous equilibrium and the documented steady balance only. No machinery efficiency, transient behavior, separator sizing, phase residence time, mechanical safety approval or claimed field calibration. A rejected or unbracketed root is not extrapolated into an unsupported range.
  • Exactly three once-through prescribed PT equilibrium stages, no recycle, heat-exchanger sizing, droplet carryover or residence-time design. Each must remain two-phase. No water decanter, C7+, gas recompression, upstream stage-1 conditioning duty or assumed separator efficiency.

Implemented equations

Liquid carry and cumulative component recovery

NV,j=NjβjNj+1=Nj(1−βj)zi,0=∑jNV,jyi,j+NL,3xi,3\begin{aligned}N_{V,j}&=N_j\beta_j\\N_{j+1}&=N_j(1-\beta_j)\\z_{i,0}&=\sum_jN_{V,j}y_{i,j}+N_{L,3}x_{i,3}\end{aligned}

Interstage duty and whole-train energy closure

Qj=Nj[hˉj−hˉL,j−1]hˉ1+∑j=23Qj=∑j=13NV,jhˉV,j+NL,3hˉL,3\begin{aligned}Q_j&=N_j[\bar h_j-\bar h_{L,j-1}]\\\bar h_1+\sum_{j=2}^3Q_j&=\sum_{j=1}^3N_{V,j}\bar h_{V,j}+N_{L,3}\bar h_{L,3}\end{aligned}

PR attraction with a disclosed interaction matrix

a=∑i∑jxixjaiaj(1−kij)kij=kji,kii=0\begin{aligned}a&=\sum_i\sum_j x_ix_j\sqrt{a_ia_j}(1-k_{ij})\\k_{ij}&=k_{ji},\quad k_{ii}=0\end{aligned}

Sources and maintenance

Published by PetroCalcHub Team. Implementation and source checks: . This does not claim independent expert review.

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