TEG Gas Dehydration Tutorial

This tutorial demonstrates how to model a complete triethylene glycol (TEG) gas dehydration system in NeqSim, including the absorption contactor, flash drum, and regeneration system.

Overview

TEG dehydration is the most common method for removing water from natural gas to meet pipeline specifications (typically < 7 lb/MMscf or 112 mg/Sm³).

Process Flow

Wet Gas → Inlet Separator → TEG Contactor → Dry Gas
                                ↓
                           Rich TEG
                                ↓
                           Flash Drum → Flash Gas
                                ↓
                           Regenerator → Water Vapor
                                ↓
                           Lean TEG (recycle)

Quick Start Example

Java

import neqsim.process.processmodel.ProcessSystem;
import neqsim.process.equipment.absorber.SimpleTEGAbsorber;
import neqsim.process.equipment.stream.Stream;
import neqsim.thermo.system.SystemSrkCPAstatoil;

// Create wet gas feed
SystemSrkCPAstatoil fluid = new SystemSrkCPAstatoil(303.15, 70.0);
fluid.addComponent("methane", 0.90);
fluid.addComponent("ethane", 0.05);
fluid.addComponent("propane", 0.02);
fluid.addComponent("CO2", 0.02);
fluid.addComponent("water", 0.01);  // Saturated with water
fluid.setMixingRule(10);  // CPA mixing rule
fluid.setMultiPhaseCheck(true);

// Create process
ProcessSystem process = new ProcessSystem();

// Wet gas feed
Stream wetGas = new Stream("Wet Gas", fluid);
wetGas.setFlowRate(10.0, "MSm3/day");
wetGas.setTemperature(30.0, "C");
wetGas.setPressure(70.0, "bara");
process.add(wetGas);

// Lean TEG stream
SystemSrkCPAstatoil tegFluid = new SystemSrkCPAstatoil(303.15, 70.0);
tegFluid.addComponent("TEG", 0.99);
tegFluid.addComponent("water", 0.01);  // 99% lean TEG
tegFluid.setMixingRule(10);

Stream leanTEG = new Stream("Lean TEG", tegFluid);
leanTEG.setFlowRate(3000.0, "kg/hr");  // TEG circulation rate
leanTEG.setTemperature(35.0, "C");
leanTEG.setPressure(70.0, "bara");
process.add(leanTEG);

// TEG Contactor (absorber)
SimpleTEGAbsorber contactor = new SimpleTEGAbsorber("TEG Contactor");
contactor.addGasInStream(wetGas);
contactor.addSolventInStream(leanTEG);
contactor.setNumberOfStages(6);
process.add(contactor);

// Run simulation
process.run();

// Get results
Stream dryGas = contactor.getGasOutStream();
System.out.println("Dry gas water content: " + 
    dryGas.getFluid().getComponent("water").getx() * 1e6 + " ppm");

Python

from neqsim import jneqsim

# Classes
SystemSrkCPAstatoil = jneqsim.thermo.system.SystemSrkCPAstatoil
ProcessSystem = jneqsim.process.processmodel.ProcessSystem
Stream = jneqsim.process.equipment.stream.Stream
SimpleTEGAbsorber = jneqsim.process.equipment.absorber.SimpleTEGAbsorber

# Create wet gas
fluid = SystemSrkCPAstatoil(273.15 + 30.0, 70.0)
fluid.addComponent("methane", 0.90)
fluid.addComponent("ethane", 0.05)
fluid.addComponent("propane", 0.02)
fluid.addComponent("CO2", 0.02)
fluid.addComponent("water", 0.01)
fluid.setMixingRule(10)
fluid.setMultiPhaseCheck(True)

# Process setup
process = ProcessSystem()

wet_gas = Stream("Wet Gas", fluid)
wet_gas.setFlowRate(10.0, "MSm3/day")
wet_gas.setTemperature(30.0, "C")
wet_gas.setPressure(70.0, "bara")
process.add(wet_gas)

# Lean TEG
teg_fluid = SystemSrkCPAstatoil(273.15 + 35.0, 70.0)
teg_fluid.addComponent("TEG", 0.99)
teg_fluid.addComponent("water", 0.01)
teg_fluid.setMixingRule(10)

lean_teg = Stream("Lean TEG", teg_fluid)
lean_teg.setFlowRate(3000.0, "kg/hr")
lean_teg.setTemperature(35.0, "C")
lean_teg.setPressure(70.0, "bara")
process.add(lean_teg)

# Contactor
contactor = SimpleTEGAbsorber("TEG Contactor")
contactor.addGasInStream(wet_gas)
contactor.addSolventInStream(lean_teg)
contactor.setNumberOfStages(6)
process.add(contactor)

# Run
process.run()

# Results
dry_gas = contactor.getGasOutStream()
print(f"Dry gas water content: {dry_gas.getFluid().getComponent('water').getx() * 1e6:.1f} ppm")

Complete TEG Loop with Regeneration

For a complete TEG loop including regeneration:

import neqsim.process.processmodel.ProcessSystem;
import neqsim.process.equipment.absorber.SimpleTEGAbsorber;
import neqsim.process.equipment.distillation.Reboiler;
import neqsim.process.equipment.heatexchanger.HeatExchanger;
import neqsim.process.equipment.heatexchanger.Cooler;
import neqsim.process.equipment.pump.Pump;
import neqsim.process.equipment.separator.Separator;
import neqsim.process.equipment.stream.Stream;
import neqsim.process.equipment.valve.ThrottlingValve;
import neqsim.thermo.system.SystemSrkCPAstatoil;

public class TEGDehydrationProcess {
    public static void main(String[] args) {
        
        // === FEED STREAMS ===
        
        // Wet natural gas
        SystemSrkCPAstatoil wetGasFluid = new SystemSrkCPAstatoil(303.15, 70.0);
        wetGasFluid.addComponent("methane", 0.85);
        wetGasFluid.addComponent("ethane", 0.06);
        wetGasFluid.addComponent("propane", 0.03);
        wetGasFluid.addComponent("i-butane", 0.01);
        wetGasFluid.addComponent("n-butane", 0.01);
        wetGasFluid.addComponent("CO2", 0.02);
        wetGasFluid.addComponent("nitrogen", 0.01);
        wetGasFluid.addComponent("water", 0.01);  // Water saturated
        wetGasFluid.setMixingRule(10);
        wetGasFluid.setMultiPhaseCheck(true);
        
        ProcessSystem process = new ProcessSystem();
        
        Stream wetGas = new Stream("Wet Gas Feed", wetGasFluid);
        wetGas.setFlowRate(5.0, "MSm3/day");
        wetGas.setTemperature(35.0, "C");
        wetGas.setPressure(70.0, "bara");
        process.add(wetGas);
        
        // Lean TEG makeup (99.5% purity)
        SystemSrkCPAstatoil leanTEGFluid = new SystemSrkCPAstatoil(303.15, 70.0);
        leanTEGFluid.addComponent("TEG", 0.995);
        leanTEGFluid.addComponent("water", 0.005);
        leanTEGFluid.setMixingRule(10);
        
        Stream leanTEG = new Stream("Lean TEG", leanTEGFluid);
        leanTEG.setFlowRate(2500.0, "kg/hr");
        leanTEG.setTemperature(40.0, "C");
        leanTEG.setPressure(70.0, "bara");
        process.add(leanTEG);
        
        // === ABSORPTION SECTION ===
        
        // TEG Contactor (6 trays typical)
        SimpleTEGAbsorber contactor = new SimpleTEGAbsorber("TEG Contactor");
        contactor.addGasInStream(wetGas);
        contactor.addSolventInStream(leanTEG);
        contactor.setNumberOfStages(6);
        process.add(contactor);
        
        // Dry gas product
        Stream dryGas = contactor.getGasOutStream();
        dryGas.setName("Dry Gas Product");
        process.add(dryGas);
        
        // Rich TEG to regeneration
        Stream richTEG = contactor.getLiquidOutStream();
        richTEG.setName("Rich TEG");
        process.add(richTEG);
        
        // === REGENERATION SECTION ===
        
        // Rich TEG pressure letdown
        ThrottlingValve tegValve = new ThrottlingValve("TEG Letdown Valve", richTEG);
        tegValve.setOutletPressure(5.0);  // 5 bara flash pressure
        process.add(tegValve);
        
        // Flash drum to remove dissolved gas
        Separator flashDrum = new Separator("Flash Drum", tegValve.getOutletStream());
        process.add(flashDrum);
        
        Stream flashGas = flashDrum.getGasOutStream();
        flashGas.setName("Flash Gas");
        process.add(flashGas);
        
        Stream flashedTEG = flashDrum.getLiquidOutStream();
        flashedTEG.setName("Flashed TEG");
        process.add(flashedTEG);
        
        // Lean/Rich TEG heat exchanger
        HeatExchanger tegExchanger = new HeatExchanger("Lean/Rich Exchanger");
        tegExchanger.setFeedStream(0, flashedTEG);
        // Hot side would be lean TEG from reboiler (simplified here)
        process.add(tegExchanger);
        
        // TEG Regenerator (reboiler)
        // Temperature: 200-204°C for 99%+ purity
        // Note: Full regenerator would use DistillationColumn
        
        // === RUN SIMULATION ===
        process.run();
        
        // === RESULTS ===
        System.out.println("=== TEG Dehydration Results ===");
        System.out.println();
        
        // Wet gas water content
        double wetWaterMoleFrac = wetGas.getFluid().getComponent("water").getx();
        System.out.printf("Wet gas water content: %.0f ppm (mole)%n", 
            wetWaterMoleFrac * 1e6);
        
        // Dry gas water content
        double dryWaterMoleFrac = dryGas.getFluid().getComponent("water").getx();
        System.out.printf("Dry gas water content: %.1f ppm (mole)%n", 
            dryWaterMoleFrac * 1e6);
        
        // Water removal efficiency
        double efficiency = (1.0 - dryWaterMoleFrac / wetWaterMoleFrac) * 100;
        System.out.printf("Water removal efficiency: %.2f%%%n", efficiency);
        
        // Rich TEG water loading
        double richWaterMoleFrac = richTEG.getFluid().getComponent("water").getx();
        System.out.printf("Rich TEG water content: %.2f%% (mole)%n", 
            richWaterMoleFrac * 100);
        
        // Flash gas rate
        System.out.printf("Flash gas rate: %.2f kg/hr%n", 
            flashGas.getFlowRate("kg/hr"));
    }
}

Design Parameters

Typical Operating Conditions

Parameter	Typical Range	Notes
Contactor pressure	40-100 bara	Higher pressure improves absorption
Contactor temperature	25-40°C	Lower temp improves absorption
Number of trays	4-8	6 trays typical
TEG circulation rate	15-40 L TEG/kg H₂O	Higher rate = drier gas
Lean TEG purity	99.0-99.9%	99.5% typical, >99.9% with stripping gas
Regenerator temperature	200-204°C	Max 204°C to prevent degradation
Regenerator pressure	0.1-0.5 bara	Atmospheric typical

Water Content Specifications

Specification	Limit	Unit
Pipeline spec (typical)	7	lb/MMscf
Pipeline spec (SI)	112	mg/Sm³
Cryogenic processing	1	ppm
LNG feed	0.1	ppm

TEG Circulation Rate Calculation

The TEG circulation rate affects dew point depression:

\[\text{TEG Rate} = \frac{W_{in} \times Q_{gas}}{W_{cap} \times \rho_{TEG}}\]

Where:

$W_{in}$ = inlet water content (kg/Sm³)
$Q_{gas}$ = gas flow rate (Sm³/hr)
$W_{cap}$ = TEG water pickup capacity (kg H₂O/kg TEG)
$\rho_{TEG}$ = TEG density (kg/m³)

Water Dew Point Calculation

To calculate the water dew point of the dry gas:

// After running process
Stream dryGas = contactor.getGasOutStream();
SystemInterface dryGasFluid = dryGas.getFluid();

// Calculate water dew point
ThermodynamicOperations ops = new ThermodynamicOperations(dryGasFluid);
try {
    ops.waterDewPointTemperatureFlash();
    double waterDewPoint = dryGasFluid.getTemperature("C");
    System.out.printf("Water dew point: %.1f °C%n", waterDewPoint);
} catch (Exception e) {
    System.out.println("No water dew point (too dry)");
}

Stripping Gas for Enhanced Regeneration

To achieve >99.5% lean TEG purity, add stripping gas to the regenerator:

// Stripping gas (typically fuel gas or dry product gas)
SystemSrkCPAstatoil stripGasFluid = new SystemSrkCPAstatoil(473.15, 1.0);
stripGasFluid.addComponent("methane", 1.0);
stripGasFluid.setMixingRule(10);

Stream strippingGas = new Stream("Stripping Gas", stripGasFluid);
strippingGas.setFlowRate(50.0, "kg/hr");  // 2-5% of TEG rate
strippingGas.setTemperature(200.0, "C");
strippingGas.setPressure(1.0, "bara");

TEG Quality Monitoring

Key parameters to monitor for TEG health:

Parameter	Normal Range	Problem Indication
pH	6.0-8.0	<6.0 indicates acid contamination
Color	Clear to light yellow	Dark = thermal degradation
Foaming tendency	None	Indicates contamination
Flash point	>177°C	Lower = hydrocarbon contamination
Specific gravity	1.120-1.125	Variation indicates water or contamination

Common Issues and Solutions

Issue	Possible Cause	Solution
High dry gas water content	Low TEG purity	Increase regenerator temperature
	Low circulation rate	Increase TEG rate
	Too few trays	Add trays or packing
TEG losses	High reboiler temperature	Reduce to ≤204°C
	Carry-over in contactor	Add mist eliminator
Foaming	Hydrocarbon contamination	Carbon filter, skim tank
Corrosion	Acid gases, degradation products	Maintain pH, replace TEG

Using the GlycolDehydrationModule

NeqSim provides a pre-built module for TEG dehydration:

import neqsim.process.equipment.util.GlycolDehydrationModule;

// Create module
GlycolDehydrationModule tegModule = new GlycolDehydrationModule("TEG Unit");
tegModule.setGasInStream(wetGas);
tegModule.setNumberOfTheoreticalStages(6);
tegModule.setLeanGlycolPurity(0.995);  // 99.5% TEG
tegModule.setGlycolCirculationRate(3000.0);  // kg/hr

// Run
tegModule.run();

// Get dry gas
Stream dryGas = tegModule.getGasOutStream();

TEG Gas Dehydration Tutorial

Complete tutorial for modeling triethylene glycol (TEG) gas dehydration systems in NeqSim. Covers contactor design, regeneration, water content specifications, and performance optimization.

TEG Gas Dehydration Tutorial

Overview

Process Flow

Quick Start Example

Java

Python

Complete TEG Loop with Regeneration

Design Parameters

Typical Operating Conditions

Water Content Specifications

TEG Circulation Rate Calculation

Water Dew Point Calculation

Stripping Gas for Enhanced Regeneration

TEG Quality Monitoring

Common Issues and Solutions

Using the GlycolDehydrationModule

See Also