Gas-condensate LNG train: condensate, LPG and LNG

The LNG plant that is also a liquids plant, at real capacity: this is one 4.4 Mtpa train (a two-train plant is two of these), not a scaled-down sketch. A condensate-rich field arrives by trunkline as a two-phase stream: the slug catcher drops ~20 mol% of it out as raw condensate before a single molecule reaches the cold end, and the plant then runs two trains side by side off one feed. Liquids: the raw condensate is let down to an MP flash that strips the dissolved methane (without it the stabilizer's shortcut total condenser tries to condense methane at 8 bar, which is not a real stabilizer overhead), then stabilized to a C5/C6 product. Gas: sweetened and dried, chilled to 245 K to knock out an NGL cut, and the NGL demethanized and split by a deethanizer / depropanizer / debutanizer sequence into commercial propane (~98 mol%) and butane (~98 mol%) LPG plus a natural-gasoline bottoms. LNG: the lean gas goes to the same APCI C3MR cold end as the 'c3mr-lng-liquefaction' showcase — propane precool, mixed-refrigerant MCHE to 120 K, JT letdown to a 1.5 bar end-flash drum. Five sold products come out of one flowsheet, each a stream the solver computed. Watch the end-flash boil-off: it leaves at ~13 mol% nitrogen against 1 mol% in the feed, because the flash drum is where an LNG train actually rejects its nitrogen — nobody specified that, the flash found it. Dehydration is the real molecular-sieve bed, not a stand-in: a 4A sieve sized by length-of-unused-bed, which is what actually takes the gas to the <=0.1 ppmv the cold box needs — 95 t of sieve on a 5.5 x 5.5 m bed, a 17.5 h cycle and 1.4 MW of regeneration duty, with 0.47 bar of Ergun pressure drop. The AGRU spec is checked against the physics rather than assumed: 99.9% CO2 removal leaves 33 ppmv, and at the coldest point in the train (115.9 K) the solid-CO2 solubility limit is 232 ppmv on the measured-data basis — a 7x margin, so the sweetening spec demonstrably clears freeze-out instead of merely looking tight. Honesty notes: (1) the four fractionation columns are distillation nodes solved at fidelity: shortcut — Fenske-Underwood-Gilliland, not rigorous MESH. The dial is real and one param away: set fidelity to rigorous on any of them (with n_stages, feed_stage and reflux_ratio) and that column solves the full stage profile. It is expensive — flipping the deethanizer alone takes the flowsheet from 1.3 s to ~240 s, because a 9-component C1-to-C6 wide-boiling MESH column is the hard case for this solver — so the library ships at shortcut fidelity and leaves the choice to you. (2) Acid-gas removal is a fixed-recovery component separator, which is how a front-end study specifies an AGRU — you set the outlet spec and size the amine unit against it. That is deliberate here rather than a gap: the rigorous Kremser contactor drives the treated gas to exactly zero CO2 at every solvent rate, an equilibrium artifact that would replace a defensible 33 ppmv with a number no gas-treating engineer would accept. For the real solvent chemistry — circulation, loadings, reboiler duty — see 'mixed-amine-acid-gas-treating' and 'barrow-island-lng-co2-injection'; for a contactor that resolves genuine slip, 'rate-based-amine-absorber'. (3) The reservoir fluid is a representative condensate-rich composition, not a published field assay. (4) Single-level propane precool and one MCHE bundle (a real train uses three levels and two bundles); refrigerant charges are set via tear_specs.