equinor/neqsim

What is NeqSim?

NeqSim (Non-Equilibrium Simulator) is a comprehensive Java library for fluid property estimation, process simulation, and engineering design. It covers the full process engineering workflow — from thermodynamic modeling and PVT analysis through equipment sizing, pipeline flow, safety studies, and field development economics.

Developed at NTNU and maintained by Equinor, NeqSim is used for real-world oil & gas, carbon capture, hydrogen, and energy applications.

Use it from Java, Python, Jupyter notebooks, .NET, MATLAB, or let an AI agent drive it via natural language.

Key capabilities

🚀 Quick Start

Python — try it now

pip install neqsim

from neqsim import jneqsim

# Create a natural gas fluid
fluid = jneqsim.thermo.system.SystemSrkEos(273.15 + 25.0, 60.0)  # 25°C, 60 bara
fluid.addComponent("methane", 0.85)
fluid.addComponent("ethane", 0.10)
fluid.addComponent("propane", 0.05)
fluid.setMixingRule("classic")

# Run a flash calculation
ops = jneqsim.thermodynamicoperations.ThermodynamicOperations(fluid)
ops.TPflash()
fluid.initProperties()

print(f"Gas density:    {fluid.getPhase('gas').getDensity('kg/m3'):.2f} kg/m³")
print(f"Gas viscosity:  {fluid.getPhase('gas').getViscosity('kg/msec'):.6f} kg/(m·s)")
print(f"Z-factor:       {fluid.getPhase('gas').getZ():.4f}")

Java — add to your project

Maven Central (simplest — no authentication needed):

<dependency>
  <groupId>com.equinor.neqsim</groupId>
  <artifactId>neqsim</artifactId>
  <version>3.6.1</version>
</dependency>

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

SystemSrkEos fluid = new SystemSrkEos(273.15 + 25.0, 60.0);
fluid.addComponent("methane", 0.85);
fluid.addComponent("ethane", 0.10);
fluid.addComponent("propane", 0.05);
fluid.setMixingRule("classic");

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

System.out.println("Density: " + fluid.getDensity("kg/m3") + " kg/m³");

AI agent — describe your problem in plain English

@solve.task hydrate formation temperature for wet gas at 100 bara

The agent scopes the task, builds a NeqSim simulation, validates results, and generates a Word + HTML report — no coding required.

🔧 What can you do with NeqSim?

from neqsim import jneqsim

fluid = jneqsim.thermo.system.SystemSrkEos(273.15 + 15.0, 100.0)
fluid.addComponent("methane", 0.90)
fluid.addComponent("CO2", 0.05)
fluid.addComponent("nitrogen", 0.05)
fluid.setMixingRule("classic")

ops = jneqsim.thermodynamicoperations.ThermodynamicOperations(fluid)
ops.TPflash()
fluid.initProperties()

print(f"Density:      {fluid.getDensity('kg/m3'):.2f} kg/m³")
print(f"Molar mass:   {fluid.getMolarMass('kg/mol'):.4f} kg/mol")
print(f"Phases:       {fluid.getNumberOfPhases()}")

from neqsim import jneqsim

fluid = jneqsim.thermo.system.SystemSrkEos(273.15 + 30.0, 80.0)
fluid.addComponent("methane", 0.80)
fluid.addComponent("ethane", 0.12)
fluid.addComponent("propane", 0.05)
fluid.addComponent("n-butane", 0.03)
fluid.setMixingRule("classic")

Stream = jneqsim.process.equipment.stream.Stream
Separator = jneqsim.process.equipment.separator.Separator
Compressor = jneqsim.process.equipment.compressor.Compressor
ProcessSystem = jneqsim.process.processmodel.ProcessSystem

feed = Stream("Feed", fluid)
feed.setFlowRate(50000.0, "kg/hr")

separator = Separator("HP Separator", feed)
compressor = Compressor("Export Compressor", separator.getGasOutStream())
compressor.setOutletPressure(150.0, "bara")

process = ProcessSystem()
process.add(feed)
process.add(separator)
process.add(compressor)
process.run()

print(f"Compressor power: {compressor.getPower('kW'):.0f} kW")
print(f"Gas out temp:     {compressor.getOutletStream().getTemperature() - 273.15:.1f} °C")

from neqsim import jneqsim

fluid = jneqsim.thermo.system.SystemSrkEos(273.15 + 5.0, 80.0)
fluid.addComponent("methane", 0.90)
fluid.addComponent("ethane", 0.06)
fluid.addComponent("propane", 0.03)
fluid.addComponent("water", 0.01)
fluid.setMixingRule("classic")
fluid.setMultiPhaseCheck(True)

ops = jneqsim.thermodynamicoperations.ThermodynamicOperations(fluid)
ops.hydrateFormationTemperature()

print(f"Hydrate T: {fluid.getTemperature() - 273.15:.2f} °C")

from neqsim import jneqsim

fluid = jneqsim.thermo.system.SystemSrkEos(273.15 + 40.0, 120.0)
fluid.addComponent("methane", 0.95)
fluid.addComponent("ethane", 0.05)
fluid.setMixingRule("classic")

Stream = jneqsim.process.equipment.stream.Stream
PipeBeggsAndBrills = jneqsim.process.equipment.pipeline.PipeBeggsAndBrills

feed = Stream("Inlet", fluid)
feed.setFlowRate(200000.0, "kg/hr")

pipe = PipeBeggsAndBrills("Export Pipeline", feed)
pipe.setPipeWallRoughness(5e-5)
pipe.setLength(50000.0)       # 50 km
pipe.setDiameter(0.508)        # 20 inch
pipe.setNumberOfIncrements(20)
pipe.run()

outlet = pipe.getOutletStream()
print(f"Outlet pressure: {outlet.getPressure():.1f} bara")
print(f"Outlet temp:     {outlet.getTemperature() - 273.15:.1f} °C")

Explore 30+ Jupyter notebooks in examples/notebooks/:

• Phase envelope calculation
• TEG dehydration process
• Vessel depressurization / blowdown
• Heat exchanger thermal-hydraulic design
• Production bottleneck analysis
• Risk simulation and visualization
• Data reconciliation and parameter estimation
• Reservoir-to-export integrated workflows
• Multiphase transient pipe flow

🤖 Agentic Engineering & MCP Server

LLMs are excellent at engineering reasoning but hallucinate physics. NeqSim is exact on thermodynamics but needs context. Together, they form a complete engineering system.

How NeqSim compares for engineering workflows

MCP Server — give any LLM access to rigorous thermodynamics

The NeqSim MCP Server lets any MCP-compatible client (VS Code Copilot, Claude Desktop, Cursor, etc.) run real calculations:

AI task-solving workflow

With VS Code + GitHub Copilot Chat:

@solve.task hydrate formation temperature for wet gas at 100 bara

Without Copilot (script-based):

pip install -e devtools/
python devtools/new_task.py "hydrate formation temperature" --type A

The workflow creates a task folder, researches the topic, builds and runs simulations, validates results, and generates a professional report. See the step-by-step tutorial or the full workflow reference.

☕ Use NeqSim in Java

Add as a Maven dependency

From Maven Central (simplest):

<dependency>
  <groupId>com.equinor.neqsim</groupId>
  <artifactId>neqsim</artifactId>
  <version>3.6.1</version>
</dependency>

From GitHub Packages (latest snapshots):

1. Configure authentication in your Maven settings.xml:

<servers>
  <server>
    <id>github</id>
    <username>YOUR_GITHUB_USERNAME</username>
    <password>${env.GITHUB_TOKEN}</password>
  </server>
</servers>

2. Add to your pom.xml:

<repositories>
  <repository>
    <id>github</id>
    <url>https://maven.pkg.github.com/equinor/neqsim</url>
  </repository>
</repositories>

Java code example — process simulation

import neqsim.thermo.system.SystemSrkEos;
import neqsim.process.equipment.stream.Stream;
import neqsim.process.equipment.separator.Separator;
import neqsim.process.equipment.compressor.Compressor;
import neqsim.process.processmodel.ProcessSystem;

// Define fluid
SystemSrkEos fluid = new SystemSrkEos(273.15 + 30.0, 80.0);
fluid.addComponent("methane", 0.80);
fluid.addComponent("ethane", 0.12);
fluid.addComponent("propane", 0.05);
fluid.addComponent("n-butane", 0.03);
fluid.setMixingRule("classic");

// Build flowsheet
Stream feed = new Stream("Feed", fluid);
feed.setFlowRate(50000.0, "kg/hr");

Separator separator = new Separator("HP Sep", feed);
Compressor compressor = new Compressor("Comp", separator.getGasOutStream());
compressor.setOutletPressure(150.0);

ProcessSystem process = new ProcessSystem();
process.add(feed);
process.add(separator);
process.add(compressor);
process.run();

System.out.println("Power: " + compressor.getPower("kW") + " kW");

Learn more

• Complete Java Getting Started Guide — Prerequisites, IDE setup, EOS selection, flash types, project structure, and contributor conventions
• NeqSim JavaDoc — Full API reference
• Java Wiki & examples — Usage patterns and guides
• NeqSim Colab demo (Java) — Try interactively

🐍 Use NeqSim in Python

pip install neqsim

NeqSim Python gives you direct access to the full Java API via the jneqsim gateway. All Java classes are available — thermodynamics, process equipment, PVT, standards, everything.

from neqsim import jneqsim

# All Java classes accessible through jneqsim
SystemSrkEos = jneqsim.thermo.system.SystemSrkEos
ProcessSystem = jneqsim.process.processmodel.ProcessSystem
Stream = jneqsim.process.equipment.stream.Stream
# ... 200+ classes available

Explore 30+ ready-to-run Jupyter notebooks in examples/notebooks/.

Other language bindings

🏗️ Develop & Contribute

Clone and build

git clone https://github.com/equinor/neqsim.git
cd neqsim
./mvnw install        # Linux/macOS
mvnw.cmd install      # Windows

Run tests

./mvnw test                                    # all tests
./mvnw test -Dtest=SeparatorTest               # single class
./mvnw test -Dtest=SeparatorTest#testTwoPhase  # single method
./mvnw checkstyle:check spotbugs:check pmd:check  # static analysis

Open in VS Code

The repository includes a ready-to-use dev container — just open the repo in VS Code with container support:

git clone https://github.com/equinor/neqsim.git
cd neqsim
code .

Architecture

NeqSim is built on seven modules:

For details see docs/modules.md.

Contributing

We welcome contributions of all kinds — bug fixes, new models, examples, documentation, and notebook recipes.

• CONTRIBUTING.md — Code of conduct and PR process
• Developer setup guide — Build, test, and project structure
• Contributing structure — Where to place code, tests, and resources
• Interactive Colab demo — Getting started as a developer

All tests and ./mvnw checkstyle:check must pass before a PR is merged.

📚 Documentation & Resources

Authors

Even Solbraa (esolbraa@gmail.com), Marlene Louise Lund

NeqSim development was initiated at NTNU. A number of master and PhD students have contributed to its development — we greatly acknowledge their contributions.

License

Apache-2.0