Cold, and what it costs
Coupled cascade loops down to −190 °C, hydrogen liquefaction with the catalytic conversion step that decides whether the liquid survives storage, turboexpander helium recovery and cold-box separation — closed loops solved as closed loops.
Process modules
Propylene, ethylene and methane loops in series to −150 °C, each condensing against the next one's evaporator.
Open process page →A Linde-Hampson recycle with catalytic ortho-para conversion — the step whose absence boils a hydrogen tank empty.
Open process page →A real isentropic turboexpander and two cryogenic flash stages concentrating helium as methane and nitrogen condense out.
Open process page →Propane dehydrogenated to propylene, then recovered cryogenically from the hydrogen-rich off-gas.
Open process page →The dominant world LNG process — a closed propane precool loop and a mixed-refrigerant loop in a multi-stream exchanger.
Open process page →Every cascade here is solved as coupled loops rather than as independent textbook cycles added together, because cold-end duty propagates upward through every stage above it — which is exactly the part a single-loop calculation gets wrong. Where a refrigeration loop is represented as a net duty instead of being modelled (the PDH cold box), the page says so.