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

See the NeqSim Java Wiki for how to use the NeqSim API. Additional pages are available in the local wiki, including the distillation column solver guide with six algorithms, mathematical formulations, and usage examples. NeqSim can be built using the Maven build system (https://maven.apache.org/). All NeqSim build dependencies are given in the pom.xml file. Learn and ask questions in Discussions for use and development of NeqSim.

🚀 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.

✨ Hero Demos

Demo 1 — Natural-language dew point via MCP

You: "What is the dew point temperature of 85% methane, 10% ethane, 5% propane at 50 bara?"

The LLM calls NeqSim's runFlash tool and responds with a rigorous answer:

LLM: "The dew point temperature is -42.3°C at 50 bara (SRK equation of state, converged in 12 iterations). Below this temperature, liquid will begin to condense."

No coding. No GUI. Just a question and a physics-backed answer with provenance.

Demo 2 — JSON flowsheet → results with provenance

Send a 10-line JSON process definition to the runProcess MCP tool:

{
  "fluid": { "model": "SRK", "temperature": 303.15, "pressure": 80.0,
             "mixingRule": "classic",
             "components": { "methane": 0.80, "ethane": 0.12, "propane": 0.05, "n-butane": 0.03 } },
  "process": [
    { "type": "Stream", "name": "feed", "properties": { "flowRate": [50000.0, "kg/hr"] } },
    { "type": "Separator", "name": "HP Sep", "inlet": "feed" },
    { "type": "Compressor", "name": "Comp", "inlet": "HP Sep.gasOut",
      "properties": { "outletPressure": [150.0, "bara"] } }
  ]
}

Get back compressor power, outlet temperature, phase compositions — plus EOS model, convergence status, and warnings.

Demo 3 — Engineering study → professional report

@solve.task TEG dehydration sizing for 50 MMSCFD wet gas

The agent creates a task folder, runs NeqSim simulations, generates matplotlib figures, validates against standards, and produces a Word + HTML report — complete with uncertainty analysis and risk evaluation.

🔧 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:

Install in seconds — pick jar or Docker:

# Jar (requires Java 17+) — replace VERSION with the latest release, e.g. 3.7.0
curl -fLO "https://github.com/equinor/neqsim/releases/download/v${VERSION}/neqsim-mcp-server-${VERSION}-runner.jar"

# Docker (no Java needed)
docker pull ghcr.io/equinor/neqsim-mcp-server:latest

Then point your LLM client at java -jar neqsim-mcp-server-*.jar or docker run -i --rm ghcr.io/equinor/neqsim-mcp-server:latest. See full setup guide.

Ask the LLM	What happens	MCP Tool
"Dew point of 85% methane, 10% ethane, 5% propane at 50 bara?"	Flash calculation via NeqSim	`runFlash`
"How does density change from 0 to 50 °C at 80 bara?"	Multi-point sensitivity sweep	`runBatch`
"Get density, viscosity, and Cp from 10 to 100 bara"	Property table across a range	`getPropertyTable`
"Phase envelope for this natural gas"	Bubble/dew point curve	`getPhaseEnvelope`
"Simulate gas through a separator then compressor to 120 bara"	Full process simulation	`runProcess`
"What can NeqSim calculate?"	Capabilities discovery	`getCapabilities`

Quick path (no flowsheet needed): For single properties, sensitivity studies, and phase boundaries, use runFlash, runBatch, getPropertyTable, or getPhaseEnvelope. These return results directly with provenance metadata (EOS model, assumptions, limitations).

Full simulation path: For multi-equipment flowsheets, use runProcess with a JSON process definition. See the MCP Server docs or the getting-started tutorial.

Why trust this answer? — every result includes provenance

Unlike generic LLM guesses, every NeqSim MCP response tells you why you should trust it:

{
  "status": "success",
  "provenance": {
    "model": "SRK",
    "flashType": "TP",
    "convergence": { "converged": true, "iterations": 8 },
    "assumptions": ["Classic van der Waals mixing rule"],
    "limitations": ["SRK may underpredict liquid density by 5-15%"],
    "recommendedCrossChecks": ["Compare with GERG-2008 for high-pressure gas"]
  },
  "fluid": {
    "properties": {
      "gas": {
        "density": { "value": 62.3, "unit": "kg/m3" },
        "compressibilityFactor": { "value": 0.88 }
      }
    }
  }
}

The LLM reasons. NeqSim computes. Provenance proves it.

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

graph TB
    subgraph core["NeqSim Core (Java 8+)"]
        THERMO["Thermodynamics<br/>60+ EOS models"]
        PROCESS["Process Simulation<br/>33+ equipment types"]
        PVT["PVT Simulation"]
        MECH["Mechanical Design<br/>& Standards"]
    end

    subgraph access["Access Layers"]
        PYTHON["Python / Jupyter<br/>pip install neqsim"]
        JAVA["Java / Maven<br/>Direct API"]
        MCP["MCP Server (Java 17+)<br/>LLM integration"]
        AGENTS["AI Agents<br/>VS Code Copilot"]
    end

    PYTHON --> THERMO
    PYTHON --> PROCESS
    JAVA --> THERMO
    JAVA --> PROCESS
    MCP --> THERMO
    MCP --> PROCESS
    AGENTS --> MCP
    AGENTS --> PYTHON

Which entry point should I use?

I want to…	Use	Requires
Quick property lookup via LLM	MCP Server + any LLM client	Java 17+ (or Docker)
Python scripting / Jupyter notebooks	`pip install neqsim`	Python 3.8+, JVM
Embed in a Java application	Maven dependency	Java 8+
Full engineering study with reports	`@solve.task` agent in VS Code	VS Code + GitHub Copilot
.NET / MATLAB integration	Language bindings	See linked repos

Java version matrix

Component	Java Version	Notes
NeqSim core library	8+	All thermodynamics, process equipment, PVT
MCP server	17+	Quarkus-based; thin wrapper around core
Python users	No Java coding	JVM bundled via jpype
Running prebuilt MCP jar	17+	Download from releases

Core 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

Where to start

#	First Contribution	Difficulty	What to do
1	Add a NIST validation benchmark	Easy	Compare NeqSim flash results to NIST data in `docs/benchmarks/`
2	Create a Jupyter notebook example	Medium	Add a worked example to `examples/notebooks/`
3	Add an MCP example to the catalog	Easy	Add a new entry in `ExampleCatalog.java`
4	Fix a broken doc link	Easy	Search `docs/*/.md` for dead links and fix them
5	Add a unit test for existing equipment	Medium	Add tests under `src/test/java/neqsim/`

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

📚 Documentation & Resources

Resource	Link
User documentation	equinor.github.io/neqsim
Benchmark gallery	docs/benchmarks/ — validation against NIST, published data
Reference manual index	REFERENCE_MANUAL_INDEX.md (350+ pages)
MCP tool contract	MCP_CONTRACT.md — stable API for agent builders
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 2,954 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
neqsim-paperlab		neqsim-paperlab
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

Folders and files

Latest commit

History

Repository files navigation

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

✨ Hero Demos

Demo 1 — Natural-language dew point via MCP

Demo 2 — JSON flowsheet → results with provenance

Demo 3 — Engineering study → professional report

🔧 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

Why trust this answer? — every result includes provenance

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

Which entry point should I use?

Java version matrix

Core modules

Contributing

Where to start

📚 Documentation & Resources

Authors

License

About

Topics

Resources

License

Code of conduct

Contributing

Security policy

Uh oh!

Stars

Watchers

Forks

Releases 121

Packages 0

Uh oh!

Uh oh!

Contributors

Uh oh!

Languages

Packages