From the original LNG Plant synoptic
Change the conditions.
Follow the process.
Explore the cold train, expansion and storage. Each control changes a coupled mass-and-energy balance. Click any of the eight learning sections to revisit the full plant.
Pure methane learning model
Approximate steady states, recalculated instantly. Real natural gas is a mixture. The refrigerant loop, plant controls and equipment limits are not simulated.
Never use this tool to operate, set, size or protect real equipment.Coupled calculation zone
Cold train → expansion → storage
Functional paths only. On narrow screens, pan the diagram sideways. Moving particles show direction, not velocity. Tank fill illustrates mass yield, not tank level.Mass balance: —
Temperature profile
Actual temperaturesThe let-down outlet follows enthalpy and phase equilibrium. Its temperature is not an independent setpoint.
What changed?
Compared with reference lessonShow stream conditions and balance checks
| Stream | Temperature °C | Pressure bara | Flow kg/s | State / interpretation |
|---|
The complete plant, retained from your source
Explore all eight process sections
Retained narratives and equipment descriptions with new conceptual diagrams. Published reference cases are separate from the calculated lesson.
Scientific basis · traceable implementation
Thermodynamic references
The calculation engine implements published thermodynamic relationships and identified methane data. The register below connects each equation or constant to its source, then identifies the simplifying choices used for this educational model.
Scientific basis and educational scope
This is a source-referenced, steady-state demonstration for pure methane. Published equations provide the physical basis; the complete simulator has not been validated against an LNG plant or a reference property package. Use it to explore relationships, never to operate, set, size or protect real equipment.
1 · Peng–Robinson equation of state
Implemented form: p = RT/(v − b) − a(T)/(v² + 2bv − b²). The original alpha function uses a(T) = 0.45724 R²Tc²/Pc × [1 + κ(1 − √(T/Tc))]²; b = 0.0778 RTc/Pc; κ = 0.37464 + 1.54226ω − 0.26992ω².
The same coefficient form is available in the NIST ThermoData Engine documentation. This app applies the pure-component case. p is absolute pressure, T is kelvin and v is molar volume; calculations use SI units internally. The source establishes the equation, not this app’s accuracy for an LNG installation.
2 · Enthalpy and cooling demand
The code derives the real-fluid enthalpy correction from the Peng–Robinson equation above, then adds an ideal-gas heat-capacity term. It does not call NIST, CoolProp, Aspen or HYSYS to generate the results.
Show the implemented molar enthalpy expression
H = Cp₀(T − 298.15) + RT(Z − 1) + [(T da/dT − a)/(2√2 b)] × ln[(Z + (1 + √2)B)/(Z + (1 − √2)B)].
Z = pv/(RT); B = bp/(RT). H is J/mol; h = H/(1000M) is kJ/kg when M is kg/mol. The 298.15 K reference is an arbitrary enthalpy datum that cancels in energy differences. Cp₀ = 35 J/(mol·K) is the fixed approximation explicitly listed under model assumptions, not a sourced constant valid at every temperature.
The code solves the cubic for physically admissible roots. It selects the minimum-fugacity root for single-phase states and the liquid/vapour roots for the approximate flash endpoints. Enthalpy-to-temperature conversion uses a bounded numerical search.
3 · Methane saturation temperature
NIST Chemistry WebBook, SRD 69: methane, Antoine equation parameters. The selected row attributes the underlying data to Prydz, R. & Goodwin, R. D. (1972), “Experimental Melting and Vapor Pressures of Methane,” Journal of Chemical Thermodynamics, 4(1), 127–133. DOI: 10.1016/S0021-9614(72)80016-8. NIST fitted the Antoine coefficients from the authors’ data.
log10(P) = A − B/(T + C), with A = 3.9895, B = 443.028 and C = −0.49. P is vapour pressure in bar absolute and T is kelvin. Thus T_sat = 443.028/(3.9895 − log10(P)) + 0.49.
Published coefficient range: 90.99–189.99 K. The app uses this correlation only at the selected tank pressure of 1.05–1.50 bara, corresponding to about 112.13–116.67 K. This is a methane correlation, not a real-LNG mixture bubble/dew-point calculation.
4 · Methane constants and gas constant
- M = 0.0160425 kg/mol (16.0425 g/mol): NIST Chemistry WebBook methane molecular weight.
- Tc = 190.564 K; Pc = 4,599,200 Pa; ω = 0.01142: CoolProp v7.1.0, Methane.json, the version-pinned methane data file. These three constants are used; the CoolProp property engine is not included.
- R = 8.314462618 J/(mol·K): rounded from the 2022 CODATA value published by NIST.
Provenance precision: CoolProp v7.1.0 lists M = 0.0160428 kg/mol and a fluid-model gas constant of 8.31451 J/(mol·K). This app instead uses the separately identified NIST molecular weight and CODATA gas constant above. Its calculations are therefore not a reproduction of the CoolProp methane implementation.
5 · Mass, energy and flash separation
The calculation follows mass conservation and the steady-flow first law. An accessible derivation is given in MIT Unified Engineering, §2.5, “Control volume form of the conservation laws.” Here, changes in kinetic/potential energy and shaft work across the coolers and let-down are neglected.
- Heat removed: Q [MW] = ṁ [kg/s] × (h_in − h_out) [kJ/kg] / 1000.
- Adiabatic let-down without shaft work: h_before = h_after.
- Two-phase balance: h = (1 − x)h_liquid + x h_vapour, giving x = (h − h_liquid)/(h_vapour − h_liquid).
- Mass split: ṁ_liquid = ṁ(1 − x); ṁ_vapour = ṁx. x is bounded to 0–1, with separate temperature solving for subcooled liquid or superheated vapour.
The phase-split expression is derived from these balances; it is not an empirical plant-yield formula. Saturation temperature comes from Antoine, while endpoint enthalpies come from PR. This simplified hybrid does not solve a rigorous mixture flash or enforce full equality of liquid and vapour fugacities at the chosen saturation state.
Model assumptions and chosen lesson settings
These choices are part of this implementation. They are not values prescribed by the references above.
- Composition: 100 mol% methane. Natural-gas composition and contaminants are not represented.
- Heat capacity: ideal-gas Cp₀ fixed at 35 J/(mol·K), rather than a temperature-dependent heat-capacity model.
- Pressure losses: 1 bar through precooling and a further 1 bar through the cold exchanger. These are illustrative assumptions, not hydraulic calculations.
- Refrigeration: the precooler supplies its calculated duty without a capacity cap. Main-exchanger duty is limited by the selected heat-removal budget; if it is insufficient, the actual outlet is warmer than the requested target.
- Heat ingress: heat is added to the continuous incoming stream. Subcooling is consumed before additional vapour forms; tank inventory and time-dependent boil-off are not simulated.
- Boundary conditions: selected pressures are imposed; vapour recovery is assumed unlimited. Pressure accumulation, control loops, relief and shutdown behaviour are not calculated.
- Refrigerant circuit: represented by available thermal duty only. No refrigerant composition, compressor map, shaft power, exchanger pinch or machinery capability is predicted.
- Other plant sections: gas treatment, sulphur recovery, fractionation, nitrogen rejection and utilities remain descriptive learning content.
- Interpretation: each input change produces another steady-state case. Animation conveys flow direction, not physical response time.
Chosen input bounds and reference lesson
Feed: 10–50°C, 50–80 bara, 40–120 kg/s. Precooler target: −40 to −20°C. Cold-end target: −170 to −120°C. Available main-exchanger thermal duty: 20–90 MW. Tank pressure: 1.05–1.50 bara. Heat ingress: 0–1500 kW.
The reference lesson uses 30°C / 60 bara / 80 kg/s feed, −35°C precooling, −155°C cold-end target, 65 MW available main-exchanger duty, 1.15 bara tank pressure and 300 kW heat ingress. These numbers are selected teaching inputs, not an OEM or plant operating case.
The bounds support a stable demonstration; they are not recommended operating ranges, equipment limits or a validated accuracy envelope. Feed-side pressure remains above methane’s critical pressure, and no high-pressure two-phase quality is reported. All controls use absolute pressure (bara); retained historical references preserve their original bara/barg qualifications.
Origin of the plant learning content
The eight-section structure and 51 equipment explanations come from the original JFCF LNG Plant V3 HTML, dated 4 October 2026. Each equipment panel retains its technical reference links and distinguishes published example conditions from calculated states. New schematic visuals replace inherited photographs whose reuse rights were not verified. The original source file is unchanged.
References checked 11 October 2026 · References revision 2. Model equations, constants and numerical results are unchanged in this documentation update. Bibliographic verification and software conservation tests do not establish industrial accuracy or approval by the cited authors or organisations. External reference links require internet access; the simulator itself operates offline.