Nonideal Two-Wax Multisolid Equilibrium Calculator
Minimize Gibbs energy for one regular-solution liquid and separate C18/C20 crystals with material balance, convexity and solid-stability checks.
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.
Calculation sequence
- Supply mole fractions of a liquid solvent and the two specified pure waxes, with at least half the feed as solvent. Volumes and Hildebrand parameters are user-supplied constant liquid properties. The default values illustrate a calculation and are not claimed as measured solvent/crude characterization. Pressure must maintain the solvent as liquid over the whole interval.
- At 31 temperatures minimize one liquid plus two independently permitted pure crystals. Check species conservation and chemical-potential complementarity, including stability of an absent crystal. Enforce a sufficient global liquid convexity bound so a locally converged single-liquid result is not mislabeled as stable when the chosen regular-solution parameters could demix.
- C18 uses the matched 301.5 K / 61.500 kJ/mol row and C20 the 309.6 K / 69.000 kJ/mol row in NIST, both attributed to Barbillon et al. The constant-fusion-enthalpy approximation neglects heat-capacity differences. Separate crystal amounts are moles per original feed mole, while reported liquid compositions are normalized within the remaining liquid, not per feed.
- Calculations remain local in a dedicated WebAssembly worker. The existing self-hosted scientific engine is about 33 MB raw on first use; the envelope additionally loads the pinned CoolProp engine and eccentric flow loads a 178 KB FEM package. Nothing is downloaded until calculation. No composition, heat history or measurements are sent to a calculation server. Save retains canonical input values; file backup can be shared with colleagues, while CSV/PDF retain samples, assumptions and sources. Browser storage alone can be lost.
Worked check
At 275 K the illustrative 0.60/0.20/0.20 feed and default supplied properties gives 0.313892178 mol total solid per initial mole: 0.136655479 C18 and 0.177236698 C20. Both crystals dissolve as temperature increases; the model checks each phase's disappearance instead of retaining a negative solid inventory.
Synthetic examples for reproducibility, not measured field results.
Assumptions and limitations
- 250-330 K, increasing interval no wider than 60 K. The sufficient convexity gate deliberately rejects some potentially solvable cases; it is not an LLE solver.
- Two pure crystals, not a mixed solid solution. No asphaltenes, crude-oil assay fitting, solid polymorphs, fusion-Cp corrections, pressure effects, deposition kinetics or transport.
- No vapor or joint VLLS equilibrium. The liquid-only solvent assumption and supplied parameters must be justified independently for the actual mixture; a numerical equilibrium is not a measured wax appearance temperature.
Implemented equations
Pure-solid / nonideal-liquid chemical potential
Sources and maintenance
Published by PetroCalcHub Team. Implementation and source checks: . This does not claim independent expert review.
- Thermo: regular-solution excess Gibbs energy and activity coefficients (runtime 0.6.0)
- NIST: C18 fusion enthalpy and temperature, matched Barbillon et al. 1991 row
- NIST: C20 fusion enthalpy and temperature, matched Barbillon et al. 1991 row
- SciPy: bounded roots, optimization and numerical linear algebra