How to simulate two-stage cascade (−100 °c)
Propylene + ethylene cascade: the ethylene loop condenses inside a heat exchanger against the evaporating propylene loop and serves a −100 °C load. Two coupled closed cycles. From the ChemSep casebook (Refrigeration_2-Stage-100C).
- 1Open the ready-made model
Open the "Two-stage cascade (−100 °C)" model in the MaximaLabs workspace — no install, no license. It loads live on the canvas, ready to edit and run.
- 2Confirm the thermodynamics
This process is modeled with the PENG-ROBINSON property package over ethylene, propylene — already selected, so the phase equilibrium and enthalpy are physically consistent from the first run.
- 3Review the flowsheet
The flowsheet chains 2× K1, 2× JT1, 2× Evap1, CX1. Every block is a real, solvable unit op you can reconfigure on the canvas.
- 4Run the simulation
Click Run. The deterministic solver converges the material and energy balances (recycles included) and fills the live stream table — the AI never invents a number.
- 5Read the results and iterate
Inspect the converged streams, tweak a spec, and re-run — or ask the AI copilot to explain a result or diagnose a failed solve in plain English.
- Thermodynamics
- PENG-ROBINSON
- Components
- ethylene, propylene
- Unit operations
- 2× K12× JT12× Evap1CX1
Opens live on the canvas — free, no install.
Explore the model & flowsheetFrequently asked questions
- What does the Two-stage cascade (−100 °C) model simulate?
- Propylene + ethylene cascade: the ethylene loop condenses inside a heat exchanger against the evaporating propylene loop and serves a −100 °C load. Two coupled closed cycles. From the ChemSep casebook (Refrigeration_2-Stage-100C).
- Which thermodynamic method does it use?
- The PENG-ROBINSON property package, over ethylene, propylene — already selected. You can switch the method on the canvas before running.
- Which unit operations are in the flowsheet?
- It chains 2× K1, 2× JT1, 2× Evap1, CX1. Every block is a real, solvable unit operation you can reconfigure, add to, or remove.
- Do I need to install software or buy a license?
- No. Two-stage cascade (−100 °C) runs entirely in your browser on MaximaLabs — free, no install, no license. Open the model to load it live and run the deterministic solver.
More guides like this
Three-stage cascade (−150 °C)
Propylene → ethylene → methane cascade to −150 °C: each colder loop condenses against the next-warmer loop’s evaporator. From the ChemSep casebook (Refrigeration_3-Stage-150C).
Four-stage cascade (≈−190 °C)
Propylene → ethylene → methane → nitrogen cascade reaching ≈81 K — four coupled closed loops, the full ChemSep cascade ladder (Refrigeration_4-Stage-190C). Air-separation-grade cold from stacked vapor-compression cycles.
C3MR LNG liquefaction
A simplified APCI C3MR train: natural gas and the mixed refrigerant are precooled by a closed propane loop, liquefied to 120 K in a multi-stream main cryogenic exchanger against a closed N₂/C₁/C₂/C₃ refrigerant cycle, then let down to storage — LNG at ~115 K. Single-level precool and a single MCHE bundle (a real train uses three propane levels and two bundles); refrigerant charges are set via tear_specs.
TEALARC LNG liquefaction
A simplified Technip TEALARC train: two closed mixed-refrigerant loops — a heavy C₁/C₂/C₃ precool MR that also cools itself in a 4-stream exchanger, and a light N₂/C₁/C₂/C₃ liquefaction MR — bring natural gas to 120 K before letdown to storage (LNG at ~115 K). Both circulations are set via tear_specs; the precool MR runs rich for pinch feasibility (screening fidelity). From the ChemSep casebook (TEALARC).
Snohvit mixed-fluid-cascade LNG liquefaction
A simplified Statoil/Linde MFC train: three independent, cascaded closed refrigerant loops (propane precool, an N₂/methane/ethane liquefaction MR, and an N₂/methane subcooling MR) each condense/precool through the previous stage's cold box before their own JT expansion — the same cross-stage coupling TEALARC uses, one level deeper. Natural gas is cooled 300 K → 255 K → 175 K → 112 K across the three multi-stream exchangers before letdown to LNG storage (~114 K). All three circulations are set via tear_specs. From the ChemSep casebook (Snohvit MFC).
FLNG dual N2-expander liquefaction
A reverse-Brayton (turboexpander, not vapor-compression) liquefaction train — the compact, offshore-friendly FLNG alternative to mixed-refrigerant cycles like C3MR. Natural gas is acid-gas-scrubbed and mol-sieve-dried (fixed-recovery separators, the same simplification the existing carbon-capture example uses for amine treating), then cooled in two cascaded closed nitrogen loops: a warm loop precools the gas and the cold loop's own N₂ charge, and a cold loop finishes the liquefaction to ~113 K in a main cryogenic multi-stream exchanger. Both loops are pure compressor + turboexpander cycles — no phase change in the refrigerant, no JT valves — the real differentiator from every other LNG example here. Single precool level and a single MCHE bundle (a real train uses more); refrigerant charges are set via tear_specs.