Distillation Equipment

Documentation for distillation column equipment in NeqSim process simulation.

Table of Contents

• Overview
• Column Types
• Configuration
• Builder Pattern
• Solver Options
• Column Specifications
• Usage Examples

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Overview

Location: neqsim.process.equipment.distillation

Classes:

• DistillationColumn - Main distillation column
• SimpleTray - Individual tray
• Condenser - Column condenser
• Reboiler - Column reboiler

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Basic Usage

import neqsim.process.equipment.distillation.DistillationColumn;

// Create column with 10 trays, condenser, and reboiler
DistillationColumn column = new DistillationColumn("Deethanizer", 10, true, true);
column.addFeedStream(feedStream, 5);  // Feed on tray 5
column.setCondenserTemperature(40.0, "C");
column.setReboilerTemperature(120.0, "C");
column.run();

// Get products
Stream overhead = column.getGasOutStream();
Stream bottoms = column.getLiquidOutStream();

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Builder Pattern

For complex column configurations, use the fluent Builder API:

import neqsim.process.equipment.distillation.DistillationColumn;
import neqsim.process.equipment.distillation.DistillationColumn.SolverType;

// Build column with fluent API
DistillationColumn column = DistillationColumn.builder("Deethanizer")
    .numberOfTrays(15)
    .withCondenserAndReboiler()
    .topPressure(25.0, "bara")
    .bottomPressure(26.0, "bara")
    .temperatureTolerance(0.001)
    .massBalanceTolerance(0.01)
    .maxIterations(100)
    .solverType(SolverType.INSIDE_OUT)
    .internalDiameter(2.5)
    .addFeedStream(feedStream, 8)
    .build();

column.run();

Builder Methods

Method	Description
numberOfTrays(int)	Set number of simple trays (excluding condenser/reboiler)
withCondenser()	Add condenser at top
withReboiler()	Add reboiler at bottom
withCondenserAndReboiler()	Add both
topPressure(double, String)	Set top pressure with unit
bottomPressure(double, String)	Set bottom pressure with unit
pressure(double, String)	Set same pressure top and bottom
temperatureTolerance(double)	Convergence tolerance for temperature
massBalanceTolerance(double)	Convergence tolerance for mass balance
tolerance(double)	Set all tolerances at once
maxIterations(int)	Maximum solver iterations
solverType(SolverType)	Set solver algorithm
directSubstitution()	Use direct substitution solver
dampedSubstitution()	Use damped substitution solver
insideOut()	Use inside-out solver
relaxationFactor(double)	Damping factor for solver
internalDiameter(double)	Column internal diameter (meters)
multiPhaseCheck(boolean)	Enable/disable multi-phase check
addFeedStream(Stream, int)	Add feed stream to specified tray
topSpecification(ColumnSpecification)	Set top product specification
bottomSpecification(ColumnSpecification)	Set bottom product specification
topProductPurity(String, double)	Shortcut: top product purity for named component
bottomProductPurity(String, double)	Shortcut: bottom product purity for named component
build()	Build the configured column

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Column Configuration

Number of Trays

// Constructor: (name, numTrays, hasCondenser, hasReboiler)
DistillationColumn column = new DistillationColumn("T-100", 20, true, true);

Feed Location

// Single feed
column.addFeedStream(feed, 10);  // Tray 10 from bottom

// Multiple feeds
column.addFeedStream(feed1, 8);
column.addFeedStream(feed2, 12);

Condenser Type

// Total condenser
column.setCondenserType("total");

// Partial condenser (vapor overhead)
column.setCondenserType("partial");

Side Draws

// Liquid side draw
column.addSideDraw(7, "liquid", 100.0, "kg/hr");

// Vapor side draw
column.addSideDraw(15, "vapor", 50.0, "kg/hr");

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Operating Specifications

Temperature Specifications

// Condenser temperature
column.setCondenserTemperature(40.0, "C");

// Reboiler temperature
column.setReboilerTemperature(120.0, "C");

Pressure Profile

// Top pressure
column.setTopPressure(15.0, "bara");

// Bottom pressure (or pressure drop)
column.setBottomPressure(16.0, "bara");

// Or specify pressure drop per tray
column.setPressureDropPerTray(0.05, "bar");

Reflux Specifications

// Reflux ratio
column.setRefluxRatio(3.0);

// Condenser duty
column.setCondenserDuty(-5000000.0);  // W (negative = cooling)

Reboiler Specifications

// Reboiler duty
column.setReboilerDuty(6000000.0);  // W

// Boilup ratio
column.setBoilupRatio(2.5);

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Column Specifications

NeqSim supports flexible column specifications through the ColumnSpecification class. Instead of specifying condenser/reboiler temperatures or duties directly, you can specify desired product quality targets and NeqSim will adjust operating conditions automatically using a secant-method outer loop.

Specification Types

Type	Description	Example
PRODUCT_PURITY	Mole-fraction purity of a component in a product stream	95 mol% ethane overhead
REFLUX_RATIO	Condenser reflux ratio (L/D)	Reflux ratio of 3.5
COMPONENT_RECOVERY	Fraction of feed component recovered in a product (0–1)	99% ethane recovery overhead
PRODUCT_FLOW_RATE	Total molar flow rate of a product stream (kmol/h)	100 kmol/h overhead
DUTY	Condenser or reboiler duty (W)	Reboiler duty 5 MW

Product Purity Specification

// Specify top and bottom product purities
column.setTopProductPurity("ethane", 0.95);      // 95 mol% ethane overhead
column.setBottomProductPurity("propane", 0.98);   // 98 mol% propane in bottoms
column.run();  // Outer loop adjusts condenser/reboiler temperatures

Component Recovery Specification

// Recover 99% of feed ethane in the overhead product
column.setTopComponentRecovery("ethane", 0.99);
column.run();

Reflux and Boilup Ratio

// Set reflux ratio (applied directly, no outer loop needed)
column.setCondenserRefluxRatio(3.5);

// Set boilup ratio
column.setReboilerBoilupRatio(2.0);
column.run();

Product Flow Rate Specification

// Set overhead flow rate target
column.setTopProductFlowRate(100.0);   // kmol/h
column.run();

Using ColumnSpecification Directly

import neqsim.process.equipment.distillation.ColumnSpecification;
import neqsim.process.equipment.distillation.ColumnSpecification.SpecificationType;
import neqsim.process.equipment.distillation.ColumnSpecification.ProductLocation;

// Create a custom specification
ColumnSpecification topSpec = new ColumnSpecification(
    SpecificationType.PRODUCT_PURITY,
    ProductLocation.TOP,
    0.95,        // target value
    "ethane"     // component name
);
topSpec.setTolerance(1e-3);      // convergence tolerance
topSpec.setMaxIterations(30);    // max outer-loop iterations

column.setTopSpecification(topSpec);
column.run();

Builder Pattern with Specifications

DistillationColumn column = DistillationColumn.builder("Deethanizer")
    .numberOfTrays(25)
    .withCondenserAndReboiler()
    .topPressure(25.0, "bara")
    .insideOut()
    .addFeedStream(feed, 12)
    .topProductPurity("ethane", 0.95)
    .bottomProductPurity("propane", 0.98)
    .build();
column.run();

How It Works

For direct specifications (reflux ratio, duty), the values are applied on the condenser or reboiler before the inner column solver runs.

For iterative specifications (product purity, component recovery, product flow rate), NeqSim wraps the inner solver in a secant-method outer loop that:

1. Runs the column with initial temperature guesses
2. Evaluates the specification error (current − target)
3. Adjusts condenser or reboiler temperature using the secant update
4. Repeats until the error is within tolerance (default 1e-4)

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Solver Options

Available Solvers

// Standard sequential solver
column.setSolverType(DistillationColumn.SolverType.STANDARD);

// Damped solver (more robust)
column.setSolverType(DistillationColumn.SolverType.DAMPED);

// Inside-out solver (fastest for converged cases)
column.setSolverType(DistillationColumn.SolverType.INSIDE_OUT);

Convergence Settings

// Maximum iterations
column.setMaxIterations(100);

// Tolerance
column.setTolerance(1e-6);

// Damping factor
column.setDampingFactor(0.5);

Initialization

// Linear temperature profile initialization
column.setInitialTemperatureProfile("linear");

// Custom initialization
double[] initTemps = {120, 115, 110, 105, 100, 95, 90, 85, 80, 75, 70};
column.setInitialTemperatures(initTemps);

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Column Results

Tray-by-Tray Profiles

column.run();

// Temperature profile
for (int i = 0; i < column.getNumberOfTrays(); i++) {
    double T = column.getTray(i).getTemperature("C");
    System.out.println("Tray " + i + ": " + T + " °C");
}

// Composition profile
for (int i = 0; i < column.getNumberOfTrays(); i++) {
    double[] x = column.getTray(i).getLiquidComposition();
    double[] y = column.getTray(i).getVaporComposition();
}

Duties

double Qcond = column.getCondenserDuty();  // W
double Qreb = column.getReboilerDuty();    // W

System.out.println("Condenser duty: " + (-Qcond/1e6) + " MW");
System.out.println("Reboiler duty: " + (Qreb/1e6) + " MW");

Separation Performance

// Product purities
double overheadPurity = overhead.getFluid().getComponent("ethane").getx();
double bottomsRecovery = 1.0 - (overhead.getFluid().getComponent("propane").getNumberOfmable() /
    feedStream.getFluid().getComponent("propane").getNumberOfmable());

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Example: NGL Fractionation

Deethanizer

// Feed: NGL from gas plant
SystemInterface ngl = new SystemSrkEos(273.15 + 30, 25.0);
ngl.addComponent("methane", 0.02);
ngl.addComponent("ethane", 0.25);
ngl.addComponent("propane", 0.35);
ngl.addComponent("i-butane", 0.10);
ngl.addComponent("n-butane", 0.18);
ngl.addComponent("n-pentane", 0.10);
ngl.setMixingRule("classic");

Stream feed = new Stream("NGL Feed", ngl);
feed.setFlowRate(5000.0, "kg/hr");

ProcessSystem process = new ProcessSystem();
process.add(feed);

// Deethanizer column
DistillationColumn deethanizer = new DistillationColumn("Deethanizer", 25, true, true);
deethanizer.addFeedStream(feed, 12);
deethanizer.setTopPressure(25.0, "bara");
deethanizer.setCondenserTemperature(-10.0, "C");
deethanizer.setReboilerTemperature(100.0, "C");
deethanizer.setSolverType(DistillationColumn.SolverType.INSIDE_OUT);
process.add(deethanizer);

process.run();

// Results
Stream ethaneProduct = deethanizer.getGasOutStream();
Stream c3plusProduct = deethanizer.getLiquidOutStream();

System.out.println("Ethane product:");
System.out.println("  Flow: " + ethaneProduct.getFlowRate("kg/hr") + " kg/hr");
System.out.println("  C2 purity: " +
    ethaneProduct.getFluid().getComponent("ethane").getx() * 100 + " mol%");

System.out.println("C3+ product:");
System.out.println("  Flow: " + c3plusProduct.getFlowRate("kg/hr") + " kg/hr");
System.out.println("  C2 content: " +
    c3plusProduct.getFluid().getComponent("ethane").getx() * 100 + " mol%");

Depropanizer

// Feed from deethanizer bottoms
DistillationColumn depropanizer = new DistillationColumn("Depropanizer", 30, true, true);
depropanizer.addFeedStream(c3plusProduct, 15);
depropanizer.setTopPressure(18.0, "bara");
depropanizer.setCondenserTemperature(45.0, "C");
depropanizer.setReboilerTemperature(110.0, "C");
process.add(depropanizer);

process.run();

Stream propaneProduct = depropanizer.getGasOutStream();
Stream c4plusProduct = depropanizer.getLiquidOutStream();

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Absorber Column

For absorption without reboiler:

DistillationColumn absorber = new DistillationColumn("Absorber", 10, false, false);
absorber.addFeedStream(gasStream, 1);      // Gas at bottom
absorber.addFeedStream(leanSolvent, 10);   // Solvent at top
absorber.run();

Stream richSolvent = absorber.getLiquidOutStream();
Stream sweetGas = absorber.getGasOutStream();

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Stripper Column

For stripping without condenser:

DistillationColumn stripper = new DistillationColumn("Stripper", 8, false, true);
stripper.addFeedStream(richSolvent, 1);
stripper.setReboilerTemperature(120.0, "C");
stripper.run();

Stream acidGas = stripper.getGasOutStream();
Stream leanSolvent = stripper.getLiquidOutStream();

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Related Documentation

• Process Package - Package overview
• Heat Exchangers - Condensers and reboilers
• Absorbers - Absorption columns