Java Quickstart

Get NeqSim running in your Java project in under 10 minutes.

Step 1: Add Maven Dependency (2 minutes)

Add to your pom.xml:

<dependency>
    <groupId>com.equinor.neqsim</groupId>
    <artifactId>neqsim</artifactId>
    <version>3.0.0</version>
</dependency>

Or with Gradle (build.gradle):

implementation 'com.equinor.neqsim:neqsim:3.0.0'

Step 2: First Flash Calculation (3 minutes)

Create FirstCalculation.java:

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

public class FirstCalculation {
    public static void main(String[] args) {
        // Create a natural gas at 25°C and 50 bar
        SystemSrkEos fluid = new SystemSrkEos(298.15, 50.0);  // Temperature in Kelvin!
        
        // Add components (mole fractions)
        fluid.addComponent("methane", 0.85);
        fluid.addComponent("ethane", 0.10);
        fluid.addComponent("propane", 0.05);
        
        // IMPORTANT: Always set mixing rule
        fluid.setMixingRule("classic");
        
        // Run flash calculation
        ThermodynamicOperations ops = new ThermodynamicOperations(fluid);
        ops.TPflash();
        
        // Initialize properties (required for most property access)
        fluid.initProperties();
        
        // Print results
        System.out.println("Number of phases: " + fluid.getNumberOfPhases());
        System.out.println("Density: " + fluid.getDensity("kg/m3") + " kg/m³");
        System.out.println("Z-factor: " + fluid.getZ());
        
        // Pretty print full results
        fluid.prettyPrint();
    }
}

Run it:

mvn compile exec:java -Dexec.mainClass="FirstCalculation"

Step 3: First Process Simulation (5 minutes)

Create FirstProcess.java:

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

public class FirstProcess {
    public static void main(String[] args) {
        // 1. Create feed fluid
        SystemSrkEos fluid = new SystemSrkEos(273.15 + 30, 50.0);  // 30°C, 50 bara
        fluid.addComponent("methane", 0.70);
        fluid.addComponent("ethane", 0.10);
        fluid.addComponent("propane", 0.10);
        fluid.addComponent("n-butane", 0.05);
        fluid.addComponent("n-pentane", 0.05);
        fluid.setMixingRule("classic");
        
        // 2. Create process system
        ProcessSystem process = new ProcessSystem();
        
        // 3. Add feed stream
        Stream feed = new Stream("Feed", fluid);
        feed.setFlowRate(10000, "kg/hr");
        process.add(feed);
        
        // 4. Add separator (flash to 20 bar)
        Separator separator = new Separator("HP Separator", feed);
        separator.setInternalDiameter(2.0);  // meters
        process.add(separator);
        
        // 5. Add compressor on gas outlet
        Compressor compressor = new Compressor("Gas Compressor", separator.getGasOutStream());
        compressor.setOutletPressure(80.0);  // bara
        compressor.setIsentropicEfficiency(0.75);
        process.add(compressor);
        
        // 6. Run the process
        process.run();
        
        // 7. Print results
        System.out.println("=== SEPARATOR ===");
        System.out.println("Gas out: " + separator.getGasOutStream().getFlowRate("kg/hr") + " kg/hr");
        System.out.println("Liquid out: " + separator.getLiquidOutStream().getFlowRate("kg/hr") + " kg/hr");
        
        System.out.println("\n=== COMPRESSOR ===");
        System.out.println("Power: " + compressor.getPower("kW") + " kW");
        System.out.println("Outlet T: " + (compressor.getOutletStream().getTemperature() - 273.15) + " °C");
    }
}

Common Gotchas

Issue Solution
NullPointerException on properties Call fluid.initProperties() after flash
Wrong density values Use getDensity("kg/m3") with unit for Peneloux correction
Temperature seems wrong NeqSim uses Kelvin internally. Convert: T_K = T_C + 273.15
Missing mixing rule Always call setMixingRule("classic") after adding components
Flash doesn’t converge Check if T,P are in valid range for your composition

Next Steps

API Quick Reference

Key interfaces to explore in the JavaDoc:

Interface Purpose
SystemInterface Fluid/mixture - composition, properties, flash
PhaseInterface Individual phase properties
ComponentInterface Pure component properties
ProcessEquipmentInterface Base for all equipment
StreamInterface Material streams