Helium recovery, concentrated by staging
Helium-rich gas let down through a real isentropic turboexpander, then cascaded through two cryogenic flashes as methane and nitrogen condense out.
The actual dark-mode canvas: feed gas expanded through a turboexpander, chilled and flashed twice at 125 K then 105 K so helium concentrates in the vapour while methane and nitrogen drop out as liquid.
Staging is what concentrates a trace component
Helium's K-value at these temperatures is enormous, so it stays in the vapour while everything around it condenses. Two stages in series do what one cannot: the first strips the bulk methane, the second concentrates what is left. Scope note: that near-infinite K-value is numerically awkward, and the example's own description says how it is handled.
Unit ops shipped for this vertical
Isentropic-efficiency expansion — the power-recovery counterpart to the compressor.
Duty- or outlet-condition-specified energy-balance stage.
Single-stage vapor-liquid equilibrium split at a fixed temperature/pressure.
Flash/phase-split unit op — the foundational vapor-liquid calculation.
Stream expander outlet temperature and both flash-stage conditions from the plant's OPC-UA server into this flowsheet's twin comparison — helium recovery is set by how cold the second stage actually gets, and a drifting expander shows there first.
See the Digital Twin platform →Try it yourself
- ✓Real isentropic turboexpander, not an assumed chill
- ✓Two cascaded flash stages concentrating a trace component
- ✓Nitrogen rejection on the same solved flowsheet