Process Controllers and Logic

Documentation for controllers, adjusters, recycles, and process logic in NeqSim.

Table of Contents

Overview

Location: neqsim.process.equipment.util, neqsim.process.controllerdevice, neqsim.process.logic

Classes:

Adjusters

Adjusters modify one variable to achieve a target specification.

Basic Usage

import neqsim.process.equipment.util.Adjuster;

// Adjust heater duty to achieve target outlet temperature
Adjuster tempControl = new Adjuster("TC-100");
tempControl.setAdjustedVariable(heater, "outTemperature");
tempControl.setTargetVariable(stream, "temperature", 80.0, "C");
process.add(tempControl);

Adjustable Variables

Equipment Variable Description
Heater/Cooler "duty" Heat duty
Heater/Cooler "outTemperature" Outlet temperature
Compressor "outletPressure" Discharge pressure
Valve "outletPressure" Outlet pressure
Splitter "splitFactor" Split ratio
Stream "flowRate" Flow rate

Target Variables

Equipment Variable Description
Stream "temperature" Temperature
Stream "pressure" Pressure
Stream "flowRate" Flow rate
Stream "moleFraction" Component mole fraction
Separator "liquidLevel" Liquid level

Example: Dew Point Control

// Adjust cooler to achieve hydrocarbon dew point
Adjuster dewPointControl = new Adjuster("Dew Point Controller");
dewPointControl.setAdjustedVariable(cooler, "outTemperature");
dewPointControl.setTargetPhaseCondition(stream, "dewpoint", 50.0, "bara");
process.add(dewPointControl);

Solver Settings

adjuster.setMaximumIterations(50);
adjuster.setTolerance(1e-6);
adjuster.setMinimumValue(-1e6);  // Duty lower bound
adjuster.setMaximumValue(1e6);   // Duty upper bound

Recycles

Handle recycle streams in process flowsheets.

Basic Usage

import neqsim.process.equipment.util.Recycle;

// Define recycle
Recycle recycle = new Recycle("Solvent Recycle");
recycle.addStream(recycleStream);
recycle.setOutletStream(inletMixer);
recycle.setTolerance(1e-6);
process.add(recycle);

Recycle Placement

ProcessSystem process = new ProcessSystem();

// Feed
process.add(feed);

// Mixer (combines feed and recycle)
Mixer mixer = new Mixer("M-100");
mixer.addStream(feed);
process.add(mixer);

// Process equipment
process.add(reactor);
process.add(separator);

// Splitter for recycle
Splitter splitter = new Splitter("Splitter", separator.getLiquidOutStream());
splitter.setSplitFactors(new double[]{0.9, 0.1});  // 10% recycle
process.add(splitter);

// Recycle stream
Recycle recycle = new Recycle("Recycle");
recycle.addStream(splitter.getSplitStream(1));
recycle.setOutletStream(mixer);
process.add(recycle);

// Connect mixer to recycle
mixer.addStream(recycle.getOutletStream());

process.run();

Convergence Settings

recycle.setTolerance(1e-6);
recycle.setMaximumIterations(100);

// Acceleration methods
recycle.setAccelerationMethod("wegstein");
// Options: "direct", "wegstein", "broyden"

Setters

Set variable values directly.

Basic Usage

import neqsim.process.equipment.util.Setter;

// Set flow rate
Setter flowSetter = new Setter("Flow Setter", stream);
flowSetter.setVariable("flowRate", 1000.0, "kg/hr");
process.add(flowSetter);

Mole Fraction Setter

import neqsim.process.equipment.util.MoleFractionSetter;

// Set component mole fraction
MoleFractionSetter compSetter = new MoleFractionSetter("CO2 Setter", stream);
compSetter.setMoleFraction("CO2", 0.02);
process.add(compSetter);

Calculators

Perform custom calculations.

Basic Usage

import neqsim.process.equipment.util.Calculator;

Calculator calc = new Calculator("Energy Balance");
calc.addInputVariable(stream1);
calc.addInputVariable(stream2);
calc.setOutputVariable(heater, "duty");

// Custom calculation (override in subclass or use expression)
calc.setExpression("stream1.enthalpy - stream2.enthalpy");
process.add(calc);

PID Controllers

For dynamic simulation with feedback control.

Basic Usage

import neqsim.process.controllerdevice.PIDController;

PIDController levelControl = new PIDController("LC-100");
levelControl.setMeasuredVariable(separator, "liquidLevel");
levelControl.setControlledVariable(valve, "opening");
levelControl.setSetPoint(0.5);  // 50% level

// Tuning parameters
levelControl.setKp(2.0);    // Proportional gain
levelControl.setKi(0.1);    // Integral gain (1/s)
levelControl.setKd(0.0);    // Derivative gain (s)

process.add(levelControl);

Tuning

// Action
levelControl.setReverseAction(true);  // Increase output decreases PV

// Output limits
levelControl.setOutputMin(0.0);
levelControl.setOutputMax(100.0);

// Anti-windup
levelControl.setAntiWindup(true);

Dynamic Execution

// Run transient with controllers
for (double t = 0; t < 3600; t += 1.0) {
    process.runTransient();
    
    double pv = levelControl.getProcessVariable();
    double sp = levelControl.getSetPoint();
    double out = levelControl.getOutput();
    
    System.out.printf("%.1f, %.3f, %.3f, %.1f%n", t, pv, sp, out);
}

Process Logic

Conditional logic for process decisions.

Basic Usage

import neqsim.process.logic.ProcessLogicController;

ProcessLogicController logic = new ProcessLogicController("Emergency Logic");

// Define condition
logic.setCondition(pressure, ">", 100.0, "bara");

// Define action
logic.setAction(shutoffValve, "close");

process.add(logic);

Complex Conditions

// AND condition
logic.addCondition(pressure, ">", 100.0, "bara", "AND");
logic.addCondition(temperature, ">", 150.0, "C", "AND");

// OR condition
logic.addCondition(level, "<", 0.1, "ratio", "OR");
logic.addCondition(level, ">", 0.9, "ratio", "OR");

Alarm Integration

import neqsim.process.alarm.ProcessAlarmManager;

ProcessAlarmManager alarms = process.getAlarmManager();

// High pressure alarm
alarms.addAlarm(separator, "pressure", 95.0, "high", "bara");
alarms.addAlarm(separator, "pressure", 100.0, "highHigh", "bara");

// Low level alarm
alarms.addAlarm(separator, "liquidLevel", 0.2, "low", "ratio");

Example: Complete Control System

ProcessSystem process = new ProcessSystem();

// Feed stream
Stream feed = new Stream("Feed", feedFluid);
feed.setFlowRate(1000.0, "kg/hr");
process.add(feed);

// Heater with temperature control
Heater heater = new Heater("E-100", feed);
process.add(heater);

Adjuster tempControl = new Adjuster("TC-100");
tempControl.setAdjustedVariable(heater, "duty");
tempControl.setTargetVariable(heater.getOutletStream(), "temperature", 80.0, "C");
process.add(tempControl);

// Separator with level control
Separator separator = new Separator("V-100", heater.getOutletStream());
process.add(separator);

ThrottlingValve liquidValve = new ThrottlingValve("LV-100", separator.getLiquidOutStream());
liquidValve.setOutletPressure(5.0, "bara");
process.add(liquidValve);

// Level controller (for dynamic)
PIDController levelControl = new PIDController("LC-100");
levelControl.setMeasuredVariable(separator, "liquidLevel");
levelControl.setControlledVariable(liquidValve, "opening");
levelControl.setSetPoint(0.5);
levelControl.setKp(5.0);
levelControl.setKi(0.5);
process.add(levelControl);

// Pressure control
ThrottlingValve gasValve = new ThrottlingValve("PV-100", separator.getGasOutStream());
process.add(gasValve);

Adjuster pressControl = new Adjuster("PC-100");
pressControl.setAdjustedVariable(gasValve, "outletPressure");
pressControl.setTargetVariable(separator, "pressure", 20.0, "bara");
process.add(pressControl);

// Run steady state
process.run();

// Run dynamic
for (double t = 0; t < 3600; t += 1.0) {
    // Disturbance at t=600
    if (Math.abs(t - 600) < 0.5) {
        feed.setFlowRate(1200.0, "kg/hr");
    }
    
    process.runTransient();
}