Jet loop reactor: nitrobenzene to aniline

A circulating loop reactor of the kind BASF and Buss built for strongly exothermic three-phase hydrogenations -- here nitrobenzene to aniline (C6H5NO2 + 3 H2 -> C6H5NH2 + 2 H2O, -443 kJ/mol). Fresh nitrobenzene and hydrogen are injected into a large circulating liquid stream; the reactor itself runs adiabatic and the reaction heat is taken out by a heat exchanger in the EXTERNAL loop, which is the whole architectural point -- the exchanger area is set independently of the reactor, and the circulation rate, not a cooling jacket, is what holds the temperature. A gas separator vents the excess hydrogen, 5% of the liquid is taken off as crude aniline, and the rest is pumped back. What it computes: a 19:1 recycle-to-product ratio holds the adiabatic reactor to 429.7 K in / 494.3 K out, a 64.6 K rise, with the loop cooler removing 4.66 MW; overall nitrobenzene conversion is 99.98% (99.70% per pass) and the crude leaves at 34.7% aniline / 64.9% water. Counting the vent as well as the crude, one aniline is made per two water, which is the stoichiometric mass-balance check on the whole loop -- the crude by itself runs slightly water-lean because the vent carries water vapour off with the excess hydrogen. The acid test is what happens without the loop: the same feed in one adiabatic once-through reactor is already at 627 K by 30% conversion and runs off the top of the model's temperature range well before full conversion. That gap is the reason the architecture exists. Honesty notes: (1) the rate constants are illustrative, chosen for a realistic per-pass conversion, not fitted plant or catalyst data -- the kinetic reactor requires the user to supply them and none ship with it; (2) the jet nozzle is not modeled hydraulically -- gas induction and entrainment by the motive jet, the loop pressure drop, and the gas hold-up and mass-transfer intensification a real jet loop is chosen for are all represented only as a circulation pump plus a mixer, so this captures the loop's THERMAL behaviour, not its mass-transfer behaviour; (3) an ideal CSTR with one lumped reaction -- no nitrosobenzene / phenylhydroxylamine / azo intermediates and no condensation by-products, so selectivity is assumed, not predicted; (4) Peng-Robinson on a strongly polar aniline/water mixture is screening-grade, and the 1.5 mol% aniline carried out in the vent is a real consequence of that (a plant condenses and recovers it); (5) this is the reactor class, not a reproduction of any licensor's design. Loop balances closed to this tolerance are the precondition for an acceptance test under VDI 2048.