A PDH cold box, where the propylene is actually lost
Propane dehydrogenated to propylene over a Pt/Cr catalyst, then recovered cryogenically from the hydrogen-rich reactor off-gas.
The actual dark-mode canvas: propane dehydrogenated over a Pt/Cr catalyst, then the reactor effluent chilled in a cold box so propylene condenses out and the hydrogen leaves as off-gas.
Where the propylene is actually lost
Dehydrogenation is equilibrium-limited, so per-pass conversion is modest and the recovery step decides the economics — every degree the cold box misses sends propylene out with the hydrogen. Scope note: the refrigeration loop itself is not modelled here; the cold box is represented as the net cooling duty required, which the example's description states plainly.
Unit ops shipped for this vertical
A specified per-pass conversion on a key component — the shortcut counterpart to the equilibrium and kinetic reactors.
Duty- or outlet-condition-specified energy-balance stage.
Single-stage vapor-liquid equilibrium split at a fixed temperature/pressure.
Stream reactor conversion and cold-box outlet temperature from the unit's OPC-UA server into this flowsheet's twin comparison — propylene recovery is a steep function of that temperature, so a small drift is a large loss.
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- ✓Reaction and cryogenic recovery on one flowsheet
- ✓After US Patent 6,333,445 (Chart Inc., 2002)
- ✓Cold box as a net duty — stated plainly, not disguised