Carbon monoxide (from a syngas cold box outside the boundary) is compressed to 4.6 MPa and absorbed into recycled methanol with 2.5 wt% sodium methoxide in a gas-liquid loop reactor at 353 K; 30 % of the methanol is converted per pass and the CO-rich vent (8 % of the CO fed) is burnt in a thermal oxidiser. Methyl formate is distilled off and hydrolysed at 393 K with water (1.5 mol/mol), autocatalysed by recycled formic acid, to 95 % (assumed) of the equilibrium conversion (28.9 % per pass). Unreacted ester and the methanol formed are distilled off and recycled; the methanol returns dry to the carbonylation, so only losses are made up. The dilute acid (49 wt%) is concentrated by pressure-swing distillation across the maximum-boiling formic acid / water azeotrope: a 203 kPa(a) column takes water overhead (recycled to the hydrolysis) and a 12 kPa(a) column gives the 85 wt% product overhead, its 66 wt% bottoms returning to the hydrolyser as catalyst.
The reactors are conversion models from open patents (US4216339A, EP2747883A1, EP3661904B1, US4299981); separators and columns are specified splits and every duty a shortcut estimate from an independent script (scripts/balance.py), because no property package of core covers this liquid system. See DESIGN.md for every assumption and gated step.