NeqSim

Open-source process engineering toolkit — thermodynamics, process simulation, and AI-assisted design in one library.

Quick Start · Use Cases · Java · Python · AI / MCP · Docs · Community

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

Domain	What NeqSim provides
Thermodynamics	60+ equation-of-state models (SRK, PR, CPA, GERG-2008, …), flash calculations (TP, PH, PS, dew, bubble), phase envelopes
Physical properties	Density, viscosity, thermal conductivity, surface tension, diffusion coefficients
Process simulation	33+ equipment types — separators, compressors, heat exchangers, valves, distillation columns, pumps, reactors
Pipeline & flow	Steady-state and transient multiphase pipe flow (Beggs & Brill, two-fluid model), pipe networks
PVT simulation	CME, CVD, differential liberation, separator tests, swelling tests, saturation pressure
Safety	Depressurization/blowdown, PSV sizing (API 520/521), source term generation, safety envelopes
Standards	ISO 6976 (gas quality), NORSOK, DNV, API, ASME compliance checks
Mechanical design	Wall thickness, weight estimation, cost analysis for pipelines, vessels, wells (SURF)
Field development	Production forecasting, concept screening, NPV/IRR economics, Monte Carlo uncertainty

🚀 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?

Calculate fluid properties

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()}")

Simulate a process flowsheet

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")

Predict hydrate formation temperature

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")

Run pipeline pressure-drop calculations

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")

More examples

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

Aspect	Manual Coding	Commercial Simulators	Agentic NeqSim
Learning curve	Steep (learn API)	Moderate (learn GUI)	Low (natural language)
Standards compliance	Manual lookup	Some built-in	Agent loads applicable standards
Reproducibility	Good (code)	Poor (GUI state lost)	Excellent (notebook + task folder)
Report generation	Manual	Manual export	Automated Word + HTML
Physics rigor	Full control	Vendor-validated	Full (same NeqSim engine)

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:

Ask the LLM	What happens
"Dew point of 85% methane, 10% ethane, 5% propane at 50 bara?"	Flash calculation via NeqSim
"Get density, viscosity, and thermal conductivity at 25°C, 80 bara"	Physical property lookup
"Simulate gas through a separator then compressor to 120 bara"	Full process simulation

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):

Show GitHub Packages setup

Configure authentication in your Maven settings.xml:

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

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

Language	Repository
Python	`pip install neqsim`
MATLAB	equinor/neqsimmatlab
.NET (C#)	equinor/neqsimcapeopen

🏗️ 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:

Module	Package	Purpose
Thermodynamics	`thermo/`	60+ EOS implementations, flash calculations, phase equilibria
Physical properties	`physicalproperties/`	Density, viscosity, thermal conductivity, surface tension
Fluid mechanics	`fluidmechanics/`	Single- and multiphase pipe flow, pipeline networks
Process equipment	`process/equipment/`	33+ unit operations (separators, compressors, HX, valves, ...)
Chemical reactions	`chemicalreactions/`	Equilibrium and kinetic reaction models
Parameter fitting	`statistics/`	Regression, parameter estimation, Monte Carlo
Process simulation	`process/`	Flowsheet assembly, dynamic simulation, recycle/adjuster coordination

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

Resource	Link
User documentation	equinor.github.io/neqsim
Reference manual index	REFERENCE_MANUAL_INDEX.md (350+ pages)
JavaDoc API	JavaDoc
Jupyter notebooks	examples/notebooks/ (30+ examples)
Discussion forum	GitHub Discussions
Releases	GitHub Releases
NeqSim homepage	equinor.github.io/neqsimhome

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

Name		Name	Last commit message	Last commit date
Latest commit History 2,827 Commits
.config		.config
.devcontainer		.devcontainer
.gemini		.gemini
.github		.github
.mvn/wrapper		.mvn/wrapper
.openapi		.openapi
.vscode		.vscode
devtools		devtools
docs		docs
examples		examples
neqsim-mcp-server		neqsim-mcp-server
src		src
.gitattributes		.gitattributes
.gitignore		.gitignore
AGENTS.md		AGENTS.md
CHANGELOG_AGENT_NOTES.md		CHANGELOG_AGENT_NOTES.md
CODEOWNERS		CODEOWNERS
CODE_OF_CONDUCT.md		CODE_OF_CONDUCT.md
CONTEXT.md		CONTEXT.md
CONTRIBUTING.md		CONTRIBUTING.md
LICENSE		LICENSE
PR_DESCRIPTION.md		PR_DESCRIPTION.md
README.md		README.md
SECURITY.md		SECURITY.md
azure-pipelines.yml		azure-pipelines.yml
mvnw		mvnw
mvnw.cmd		mvnw.cmd
pom.xml		pom.xml
pomJava21.xml		pomJava21.xml
pomJava8.xml		pomJava8.xml

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NeqSim

What is NeqSim?

Key capabilities

🚀 Quick Start

Python — try it now

Java — add to your project

AI agent — describe your problem in plain English

🔧 What can you do with NeqSim?

🤖 Agentic Engineering & MCP Server

How NeqSim compares for engineering workflows

MCP Server — give any LLM access to rigorous thermodynamics

AI task-solving workflow

☕ Use NeqSim in Java

Add as a Maven dependency

Java code example — process simulation

Learn more

🐍 Use NeqSim in Python

Other language bindings

🏗️ Develop & Contribute

Clone and build

Run tests

Open in VS Code

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Contributing

📚 Documentation & Resources

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NeqSim

What is NeqSim?

Key capabilities

🚀 Quick Start

Python — try it now

Java — add to your project

AI agent — describe your problem in plain English

🔧 What can you do with NeqSim?

🤖 Agentic Engineering & MCP Server

How NeqSim compares for engineering workflows

MCP Server — give any LLM access to rigorous thermodynamics

AI task-solving workflow

☕ Use NeqSim in Java

Add as a Maven dependency

Java code example — process simulation

Learn more

🐍 Use NeqSim in Python

Other language bindings

🏗️ Develop & Contribute

Clone and build

Run tests

Open in VS Code

Architecture

Contributing

📚 Documentation & Resources

Authors

License

About

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License

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