Aspen Plus & HYSYS Chemical Process (.in, .inp, .bkp)

@modelscript/aspen (languages/aspen) provides zero-regex parsing, vapor-liquid equilibrium (VLE) flash computation, distillation column MESH equations, DAE lowering, and Modelica 3.x projection for Aspen Plus and Aspen HYSYS chemical flowsheet input decks.

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Supported Extensions & Standards

Extension	Format	Description
.in / .inp	Aspen Plus Input File	Keyword-sectioned chemical process flowsheet, unit operations, stream thermodynamics
.bkp	Aspen Backup Deck	Serialized ASCII Aspen model topology and stream definitions

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Key Capabilities

1. Rachford-Rice Vapor-Liquid Equilibrium (VLE) Flash Solver

• Solves isothermal ($T$-$P$) and adiabatic ($P$-$H$) flash equilibrium via the Rachford-Rice equation:$$f(\psi )=\sum _{i=1}^C\frac{z_i(K_i-1)}{1+\psi (K_i-1)}=0$$where $\psi =V/F$ is the vapor fraction, $z_i$ is the feed mole fraction, and $K_i(T,P)$ is the equilibrium ratio:$$K_i=\frac{y_i}{x_i}=\frac{{\gamma }_i{P}_i^{\text{sat}}(T)}{{\varphi }_{i}P}$$
• Uses modified Antoine vapor pressure equations:$$\ln P_i^{\text{sat}}=A_i-\frac{B_i}{T+C_i}$$
• Implements subcooled liquid ($\sum z_i{K}_i<1$) and superheated vapor ($\sum z_i/K_i<1$) state identification with monotonic Newton-Raphson bracket solving.

2. Unit Operations & Distillation Columns

• Mixers & Splitters: Rigorous material balance ($\sum F_{\text{in}}=\sum F_{\text{out}}$) and energy conservation ($\sum {\dot{H}}_{\text{in}}=\sum {\dot{H}}_{\text{out}}$).
• Heaters & Coolers: Specified duty ($Q$) or target outlet temperature/vapor fraction.
• Flash Separators: Multi-component 2-phase and 3-phase phase separation vessels.
• RadFrac Equilibrium Distillation Columns: Rigorous stage-by-stage MESH equations (Material balance, Equilibrium, Summation, Heat/enthalpy balance).

3. Direct Linear-Memory DAE Lowering

• Compiles flowsheet topology, stream molar balances, and component enthalpies directly into @modelscript/runtime's DAEBuilder struct-of-arrays linear memory arena without intermediary AST allocations.
• Emits continuous DAE systems with algebraic stream constraints for joint dynamic simulation with pipeline networks (@modelscript/lps) and multiphase transient pipelines (@modelscript/olga).

4. Bidirectional Modelica 3.x Projection

• Translates unit operations into standardized Modelica.Fluid or OpenIPSL thermal-fluid models with acausal fluid ports (m_flow, p, h, Xi).

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Pre-Flight Diagnostics

The Aspen analyzer inspects flowsheet connectivity, phase equilibria, and thermodynamic consistency:

15 rules12 error3 warning Run with msx aspen lint

All severitieserrorwarning

Code	Rule	Severity	Message
M8101	unconnected-stream-port	error	Stream '<streamName>' connected to block '<blockName>' inlet has no producing source block outlet.
M8102	tear-stream-unconverged	error	Circular flowsheet loop detected involving block '<blockName>' without designated tear stream.
M8103	invalid-eos-parameter	error	Component '<compName>' lacks critical properties for property method '<propertyMethod>'.
M8104	negative-component-fraction	error	Stream '<streamName>' specifies negative component molar fraction for '<compName>' (<val>).
M8105	column-reboiler-heat-deficit	warning	Column '<blockName>' duty results in non-positive reboiler boil-up.
M8106	duplicate-block-id	error	Duplicate block ID '<blockId>' declared in flowsheet.
M8107	duplicate-component-id	error	Duplicate component ID '<compId>' declared in COMPONENTS.
M8108	fractions-sum-invalid	warning	Component mole fractions in stream '<streamName>' sum to <value>, expected 1.0.
M8109	feed-stage-out-of-range	error	Column '<blockName>' feed stage <stage> is out of bounds (1..<nStages>).
M8110	product-stage-out-of-range	error	Column '<blockName>' product stage <stage> is out of bounds (1..<nStages>).
M8111	missing-flowsheet-entry	warning	Block '<blockName>' has parameter declarations but is not connected in FLOWSHEET.
M8112	stream-temperature-negative	error	Stream '<streamName>' specifies non-physical absolute temperature <temp> K.
M8113	stream-pressure-negative	error	Stream '<streamName>' specifies non-positive pressure <pres> bar.
M8114	radfrac-stages-too-few	error	RadFrac column '<blockName>' has fewer than 2 stages (<nStages>).
M8115	reflux-ratio-negative	error	Column '<blockName>' reflux ratio (<rr>) must be non-negative.

Generated from languages/aspen/src/errors.ts. All languages →

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CLI Usage

# Inspect flowsheet components, blocks, and stream properties
msx aspen inspect MethanolWaterPlant.inp

# Run pre-flight semantic diagnostics
msx aspen lint MethanolWaterPlant.inp

# Solve isothermal flash VLE for a feed stream
msx aspen solve-flash MethanolWaterPlant.inp --stream FEED

# Lower flowsheet to ModelScript linear DAE arena
msx aspen to-dae MethanolWaterPlant.inp

# Project into Modelica 3.x acausal fluid stream model
msx aspen to-modelica MethanolWaterPlant.inp -o MethanolPlant.mo