Supercritical CO₂ (critical point Tc = 31.1 °C, Pc = 73.8 bar) behaves as a single dense, gas-diffusing phase whose density — and hence its ability to dissolve nonpolar solutes — is tuned continuously by pressure and temperature. This simulator solves the real Van der Waals equation of state for CO₂ at your chosen P, T:
P = RT/(v−b) − a/v²
a = 3.640 L²·bar/mol², b = 0.04267 L/mol (CO₂)
ρ = M / v, M = 44.01 g/mol
Solved numerically (Newton-Raphson) for molar volume v at every slider change, giving a genuine pressure/temperature → density curve, not a lookup table.
Solvating power follows the density dependence of Chrastil-type solubility correlations used in real SFE process design, c ∝ ρk·exp(a/T+b): denser CO₂ packs more solvent molecules per volume around a dissolved solute, so extraction rate is modeled here as increasing with density raised to an illustrative exponent (k≈3). The exact k, a, b constants are compound-specific and measured per solute in practice — this sim uses representative values to show the *shape* of the relationship, not one substance's exact numbers.
- Extractor (left vessel) — a packed bed of solute-laden particles (amber = full, fading as depleted). Rising supercritical CO₂ picks up solute stochastically; the pickup rate scales with the solvating-power index.
- Separator (right vessel) — CO₂ carrying dissolved solute crosses the top pipe and enters a lower-pressure vessel. The pressure drop collapses CO₂ density, solvating power crashes, and the solute falls out of solution — this pressure-swing "let-down" step is exactly how industrial SFE plants (decaffeination, hop/flavor extraction, nutraceuticals) recover product without leaving any solvent residue. Recovered extract accumulates as the amber pool at the base of the separator; the stripped CO₂ recycles back to the extractor through the bottom pipe, matching the closed-loop design of a real plant.
- Note on temperature — at fixed pressure, raising temperature can either help (higher solute vapor pressure) or hurt (lower CO₂ density) extraction — the real "retrograde solubility" crossover seen in SFE literature. This sim isolates the dominant near-critical mechanism, density, to keep the controls legible.