Usage Examples

Comprehensive examples demonstrating NeqSim capabilities for thermodynamic calculations and process simulation.

Table of Contents

Thermodynamic Calculations

Basic TP Flash

The most common thermodynamic calculation - determining phase equilibrium at fixed temperature and pressure.

import neqsim.thermo.system.SystemSrkEos;
import neqsim.thermodynamicoperations.ThermodynamicOperations;

// Create a natural gas system
SystemSrkEos gas = new SystemSrkEos(298.15, 50.0);  // 25°C, 50 bar
gas.addComponent("methane", 0.85);
gas.addComponent("ethane", 0.08);
gas.addComponent("propane", 0.04);
gas.addComponent("n-butane", 0.02);
gas.addComponent("n-pentane", 0.01);
gas.setMixingRule("classic");

// Perform TP flash
ThermodynamicOperations ops = new ThermodynamicOperations(gas);
ops.TPflash();

// Print results
System.out.println("Number of phases: " + gas.getNumberOfPhases());
System.out.println("Gas fraction: " + gas.getPhaseFraction("gas", "mole"));
System.out.println("Liquid fraction: " + gas.getPhaseFraction("oil", "mole"));
System.out.println("Gas density: " + gas.getPhase("gas").getDensity("kg/m3") + " kg/m³");

Phase Envelope

Calculate the complete phase envelope (bubble and dew point curves).

import neqsim.thermo.system.SystemSrkEos;
import neqsim.thermodynamicoperations.ThermodynamicOperations;

SystemSrkEos fluid = new SystemSrkEos(298.15, 50.0);
fluid.addComponent("methane", 0.80);
fluid.addComponent("ethane", 0.10);
fluid.addComponent("propane", 0.07);
fluid.addComponent("n-heptane", 0.03);
fluid.setMixingRule("classic");

ThermodynamicOperations ops = new ThermodynamicOperations(fluid);
ops.calcPTphaseEnvelope();

// Get cricondenbar (maximum pressure point)
double cricondenbarP = ops.get("cricondenbar")[0];
double cricondenbarT = ops.get("cricondenbar")[1];
System.out.println("Cricondenbar: " + cricondenbarP + " bar at " + cricondenbarT + " K");

// Get cricondentherm (maximum temperature point)
double cricondentT = ops.get("cricondentherm")[1];
double cricondentP = ops.get("cricondentherm")[0];
System.out.println("Cricondentherm: " + cricondentT + " K at " + cricondentP + " bar");

Dew Point Calculations

Calculate hydrocarbon and water dew points.

import neqsim.thermo.system.SystemSrkCPAstatoil;
import neqsim.thermodynamicoperations.ThermodynamicOperations;

// Use CPA for accurate water modeling
SystemSrkCPAstatoil gas = new SystemSrkCPAstatoil(298.15, 70.0);
gas.addComponent("methane", 0.90);
gas.addComponent("ethane", 0.05);
gas.addComponent("propane", 0.03);
gas.addComponent("water", 0.02);
gas.setMixingRule(10);  // CPA mixing rule

ThermodynamicOperations ops = new ThermodynamicOperations(gas);

// Hydrocarbon dew point at fixed pressure
ops.dewPointTemperatureFlash();
System.out.println("HC Dew Point at 70 bar: " + (gas.getTemperature() - 273.15) + " °C");

// Water dew point
ops.waterDewPointTemperatureFlash();
System.out.println("Water Dew Point: " + (gas.getTemperature() - 273.15) + " °C");

Physical Properties

Calculate comprehensive physical properties after flash.

import neqsim.thermo.system.SystemSrkEos;
import neqsim.thermodynamicoperations.ThermodynamicOperations;

SystemSrkEos fluid = new SystemSrkEos(300.0, 30.0);
fluid.addComponent("methane", 0.95);
fluid.addComponent("CO2", 0.05);
fluid.setMixingRule("classic");

ThermodynamicOperations ops = new ThermodynamicOperations(fluid);
ops.TPflash();

// Gas phase properties
System.out.println("=== Gas Phase Properties ===");
System.out.println("Density: " + fluid.getPhase("gas").getDensity("kg/m3") + " kg/m³");
System.out.println("Viscosity: " + fluid.getPhase("gas").getViscosity("cP") + " cP");
System.out.println("Thermal Conductivity: " + fluid.getPhase("gas").getThermalConductivity("W/mK") + " W/m·K");
System.out.println("Cp: " + fluid.getPhase("gas").getCp("kJ/kgK") + " kJ/kg·K");
System.out.println("Cv: " + fluid.getPhase("gas").getCv("kJ/kgK") + " kJ/kg·K");
System.out.println("Z-factor: " + fluid.getPhase("gas").getZ());
System.out.println("Speed of Sound: " + fluid.getPhase("gas").getSoundSpeed() + " m/s");
System.out.println("Molecular Weight: " + fluid.getPhase("gas").getMolarMass() * 1000 + " g/mol");
System.out.println("Enthalpy: " + fluid.getPhase("gas").getEnthalpy("kJ/kg") + " kJ/kg");
System.out.println("Entropy: " + fluid.getPhase("gas").getEntropy("kJ/kgK") + " kJ/kg·K");

Fluid Creation

Simple Gas Mixture

import neqsim.thermo.system.SystemSrkEos;

// Standard SRK for natural gas
SystemSrkEos gas = new SystemSrkEos(298.15, 50.0);
gas.addComponent("nitrogen", 0.02);
gas.addComponent("CO2", 0.03);
gas.addComponent("methane", 0.85);
gas.addComponent("ethane", 0.06);
gas.addComponent("propane", 0.03);
gas.addComponent("i-butane", 0.005);
gas.addComponent("n-butane", 0.005);
gas.setMixingRule("classic");

Oil with Heavy Fractions

import neqsim.thermo.system.SystemSrkEos;

SystemSrkEos oil = new SystemSrkEos(350.0, 100.0);

// Light components
oil.addComponent("methane", 10.0);
oil.addComponent("ethane", 5.0);
oil.addComponent("propane", 4.0);
oil.addComponent("n-butane", 3.0);
oil.addComponent("n-pentane", 2.0);
oil.addComponent("n-hexane", 2.0);

// Heavy fractions (TBP cuts)
// addTBPfraction(name, moles, molarMass_kg/mol, density_kg/m3)
oil.addTBPfraction("C7", 5.0, 0.092, 730.0);
oil.addTBPfraction("C8", 4.0, 0.104, 750.0);
oil.addTBPfraction("C9", 3.0, 0.117, 770.0);

// Plus fraction
oil.addPlusFraction("C10+", 20.0, 0.200, 820.0);

// Set mixing rule and characterize
oil.setMixingRule("classic");

// Run characterization to split plus fraction
oil.getCharacterization().setTBPModel("PedersenSRK");
oil.getCharacterization().setPlusFractionModel("Pedersen");
oil.getCharacterization().characterisePlusFraction();

Aqueous Systems with CPA

For systems with water, glycols, or alcohols, use CPA equation of state.

import neqsim.thermo.system.SystemSrkCPAstatoil;

// Gas with MEG injection for hydrate inhibition
SystemSrkCPAstatoil fluid = new SystemSrkCPAstatoil(280.0, 100.0);
fluid.addComponent("methane", 0.85);
fluid.addComponent("ethane", 0.08);
fluid.addComponent("propane", 0.04);
fluid.addComponent("water", 0.02);
fluid.addComponent("MEG", 0.01);
fluid.setMixingRule(10);  // CPA mixing rule

// Calculate hydrate equilibrium
ThermodynamicOperations ops = new ThermodynamicOperations(fluid);
ops.hydrateFormationTemperature();
System.out.println("Hydrate formation temperature: " + (fluid.getTemperature() - 273.15) + " °C");

Process Simulation

Simple Separation

Two-stage separation with pressure reduction.

import neqsim.process.equipment.stream.Stream;
import neqsim.process.equipment.valve.ThrottlingValve;
import neqsim.process.equipment.separator.Separator;
import neqsim.process.processmodel.ProcessSystem;
import neqsim.thermo.system.SystemSrkEos;

// Create feed fluid
SystemSrkEos fluid = new SystemSrkEos(350.0, 150.0);
fluid.addComponent("methane", 70.0);
fluid.addComponent("ethane", 10.0);
fluid.addComponent("propane", 8.0);
fluid.addComponent("n-butane", 5.0);
fluid.addComponent("n-pentane", 4.0);
fluid.addComponent("n-heptane", 3.0);
fluid.setMixingRule("classic");

// Create feed stream
Stream wellStream = new Stream("Well Stream", fluid);
wellStream.setFlowRate(10000.0, "kg/hr");
wellStream.setTemperature(80.0, "C");
wellStream.setPressure(150.0, "bara");

// First stage separation
ThrottlingValve chokeValve = new ThrottlingValve("Choke Valve", wellStream);
chokeValve.setOutletPressure(50.0, "bara");

Separator hpSeparator = new Separator("HP Separator", chokeValve.getOutletStream());

// Second stage separation
ThrottlingValve lpValve = new ThrottlingValve("LP Valve", hpSeparator.getLiquidOutStream());
lpValve.setOutletPressure(5.0, "bara");

Separator lpSeparator = new Separator("LP Separator", lpValve.getOutletStream());

// Build and run process
ProcessSystem process = new ProcessSystem();
process.add(wellStream);
process.add(chokeValve);
process.add(hpSeparator);
process.add(lpValve);
process.add(lpSeparator);
process.run();

// Results
System.out.println("=== HP Separator ===");
System.out.println("Gas rate: " + hpSeparator.getGasOutStream().getFlowRate("kg/hr") + " kg/hr");
System.out.println("Oil rate: " + hpSeparator.getLiquidOutStream().getFlowRate("kg/hr") + " kg/hr");

System.out.println("=== LP Separator ===");
System.out.println("Flash gas: " + lpSeparator.getGasOutStream().getFlowRate("kg/hr") + " kg/hr");
System.out.println("Stabilized oil: " + lpSeparator.getLiquidOutStream().getFlowRate("kg/hr") + " kg/hr");

Compression System

Distillation column

Simulate a deethanizer column with six available solver algorithms. See distillation column docs for full mathematical details.

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

SystemSrkEos feed = new SystemSrkEos(216.0, 30.0);
feed.addComponent("methane", 0.5);
feed.addComponent("ethane", 0.2);
feed.addComponent("propane", 0.15);
feed.addComponent("n-butane", 0.05);
feed.addComponent("n-pentane", 0.05);
feed.addComponent("n-hexane", 0.03);
feed.addComponent("n-heptane", 0.02);
feed.setMixingRule("classic");

Stream feedStream = new Stream("feed", feed);
feedStream.setFlowRate(100.0, "kg/hr");
feedStream.run();

DistillationColumn column = new DistillationColumn("Deethanizer", 5, true, false);
column.addFeedStream(feedStream, 5);
column.getReboiler().setOutTemperature(378.15);
column.setTopPressure(30.0);
column.setBottomPressure(32.0);
column.setSolverType(DistillationColumn.SolverType.INSIDE_OUT);
column.run();

System.out.println("Gas:    " + column.getGasOutStream().getFlowRate("kg/hr") + " kg/hr");
System.out.println("Liquid: " + column.getLiquidOutStream().getFlowRate("kg/hr") + " kg/hr");

Wind turbine

The WindTurbine unit converts kinetic energy in wind into electrical power using a simple actuator-disk formulation. Air density is assumed constant at 1.225 kg/m³ and all inefficiencies are lumped into the power coefficient.

import neqsim.process.equipment.powergeneration.WindTurbine;

WindTurbine turbine = new WindTurbine("turbine");
turbine.setWindSpeed(12.0);    // m/s
turbine.setRotorArea(50.0);    // m²
turbine.setPowerCoefficient(0.4);
turbine.run();

System.out.println("Power produced: " + turbine.getPower() + " W");

Electrolyzer

Water electrolysis for hydrogen production.

import neqsim.process.equipment.electrolyzer.Electrolyzer;
import neqsim.process.equipment.stream.Stream;
import neqsim.thermo.system.SystemSrkEos;

// Water feed
SystemSrkEos water = new SystemSrkEos(298.15, 1.0);
water.addComponent("water", 1.0);
water.setMixingRule("classic");

Stream waterFeed = new Stream("Water Feed", water);
waterFeed.setFlowRate(100.0, "kg/hr");

Electrolyzer electrolyzer = new Electrolyzer("PEM Electrolyzer", waterFeed);
electrolyzer.setEfficiency(0.70);
electrolyzer.run();

System.out.println("H2 production rate: " + electrolyzer.getHydrogenOutStream().getFlowRate("kg/hr") + " kg/hr");
System.out.println("O2 production rate: " + electrolyzer.getOxygenOutStream().getFlowRate("kg/hr") + " kg/hr");
System.out.println("Power consumption: " + electrolyzer.getPower("kW") + " kW");

Membrane Separator

Gas separation using membrane technology.

import neqsim.process.equipment.separator.MembraneSeparator;
import neqsim.process.equipment.stream.Stream;
import neqsim.thermo.system.SystemSrkEos;

SystemSrkEos gas = new SystemSrkEos(298.15, 50.0);
gas.addComponent("CO2", 0.30);
gas.addComponent("methane", 0.70);
gas.setMixingRule("classic");

Stream feed = new Stream("Feed", gas);
feed.setFlowRate(1000.0, "Sm3/hr");

MembraneSeparator membrane = new MembraneSeparator("CO2 Membrane", feed);
membrane.setRelativePermability("CO2", 20.0);
membrane.setRelativePermability("methane", 1.0);
membrane.setMembranePressureDrop(30.0, "bara");
membrane.run();

System.out.println("Permeate CO2: " + membrane.getPermeateStream().getFluid().getComponent("CO2").getx() * 100 + " mol%");
System.out.println("Retentate CO2: " + membrane.getRetentateStream().getFluid().getComponent("CO2").getx() * 100 + " mol%");

Additional Resources

For more examples, see: