neqsim: Skill for Claude Code

Distillation Design Rules

Guide for distillation column modeling and design in NeqSim.

Column Setup Pattern

import neqsim.process.equipment.distillation.DistillationColumn;
import neqsim.process.equipment.stream.Stream;
import neqsim.thermo.system.SystemSrkEos;
import neqsim.thermo.system.SystemInterface;

// Create feed
SystemInterface feed = new SystemSrkEos(273.15 + 50.0, 15.0);
feed.addComponent("methane", 0.10);
feed.addComponent("ethane", 0.25);
feed.addComponent("propane", 0.30);
feed.addComponent("n-butane", 0.20);
feed.addComponent("n-pentane", 0.15);
feed.setMixingRule("classic");

Stream feedStream = new Stream("feed", feed);
feedStream.setFlowRate(10000.0, "kg/hr");
feedStream.setTemperature(50.0, "C");
feedStream.setPressure(15.0, "bara");
feedStream.run();

// Create column (name, stages, hasCondenser, hasReboiler)
DistillationColumn column = new DistillationColumn("Deethanizer", 15, true, true);
column.addFeedStream(feedStream, 8);  // Feed on stage 8

// Specifications
column.setCondenserTemperature(273.15 - 30.0);  // Kelvin
column.getReboiler().setHeatInput(1e6);          // Watts
// OR set reflux ratio:
// column.getCondenser().setRefluxRatio(2.5);

column.run();

Solver Selection

// Direct substitution (default) - robust sequential tray sweeps
column.setSolverType(DistillationColumn.SolverType.DIRECT_SUBSTITUTION);

// Inside-Out — faster for ideal/near-ideal systems
column.setSolverType(DistillationColumn.SolverType.INSIDE_OUT);

// Adaptive matrix inside-out — bypasses matrix setup on small columns,
// tries a component-balance matrix warm start on larger columns, then
// finishes with rigorous inside-out polishing
column.setSolverType(DistillationColumn.SolverType.MATRIX_INSIDE_OUT);

// Damped substitution - for difficult convergence
column.setSolverType(DistillationColumn.SolverType.DAMPED_SUBSTITUTION);

// MESH residual monitor - for residual auditing
column.setSolverType(DistillationColumn.SolverType.MESH_RESIDUAL);

// Naphtali-Sandholm - guarded simultaneous MESH residual Newton solver
column.setSolverType(DistillationColumn.SolverType.NAPHTALI_SANDHOLM);
// Optional: seed stage temperatures as initial guesses only, not fixed specs
column.setSeedTemperature(3, 273.15 + 45.0);
// Adjust max iterations
column.setMaxNumberOfIterations(200);