Water Treatment Equipment

Documentation for produced water treatment equipment in NeqSim.

Table of Contents

Overview

Package: neqsim.process.equipment.watertreatment

Produced water treatment is critical for offshore oil and gas operations. NeqSim provides equipment models for simulating oil-in-water separation processes, helping engineers design systems that meet discharge regulations.

Key Classes

Class Description
Hydrocyclone Centrifugal oil-water separator
ProducedWaterTreatmentTrain Multi-stage treatment system

Hydrocyclone

Overview

Hydrocyclones use centrifugal force to separate oil droplets from water. The swirling flow creates centrifugal acceleration many times greater than gravity, causing lighter oil droplets to migrate to the center and exit through the reject stream.

Performance Characteristics

Parameter Typical Value Range
d50 cut size 10-15 μm 8-20 μm
d100 removal 20-30 μm 15-40 μm
Reject ratio 1-3% 0.5-5%
Pressure drop 1-3 bar 0.5-5 bar
Oil removal efficiency 90-98% 85-99%

Separation Efficiency Model

The grade efficiency is modeled using:

\[\eta(d) = 1 - \exp\left(-A \cdot \left(\frac{d}{d_{50}}\right)^n\right)\]

where:

Basic Usage

import neqsim.process.equipment.watertreatment.Hydrocyclone;
import neqsim.process.equipment.stream.Stream;
import neqsim.thermo.system.SystemSrkEos;

// Create produced water stream
SystemSrkEos water = new SystemSrkEos(323.15, 10.0);
water.addComponent("water", 0.995);
water.addComponent("n-heptane", 0.005);  // Oil phase
water.setMixingRule("classic");

Stream producedWater = new Stream("Produced Water", water);
producedWater.setFlowRate(500.0, "m3/hr");
producedWater.run();

// Create hydrocyclone
Hydrocyclone cyclone = new Hydrocyclone("HP Hydrocyclone", producedWater);
cyclone.setD50Microns(12.0);
cyclone.setRejectRatio(0.02);
cyclone.setPressureDrop(2.0);
cyclone.setOilRemovalEfficiency(0.95);
cyclone.run();

// Get results
System.out.println("Outlet OIW: " + cyclone.getOutletOilConcentrationMgL() + " mg/L");
System.out.println("Recovered oil: " + cyclone.getRecoveredOilM3h() + " m³/h");

Configuration Methods

// Set d50 cut size in microns
cyclone.setD50Microns(12.0);

// Set reject ratio (oil-rich stream / feed)
cyclone.setRejectRatio(0.02);

// Set pressure drop across cyclone
cyclone.setPressureDrop(2.0);

// Set target oil removal efficiency
cyclone.setOilRemovalEfficiency(0.95);

// Set inlet oil concentration
cyclone.setInletOilConcentration(1000.0);  // mg/L

Output Streams

// Treated water (underflow) - main outlet
Stream treatedWater = (Stream) cyclone.getOutletStream();

// Rejected oil-rich stream (overflow)
Stream oilReject = (Stream) cyclone.getOilOutStream();

Produced Water Treatment Train

Overview

The ProducedWaterTreatmentTrain models a complete multi-stage treatment system typically used on offshore platforms. It combines multiple treatment technologies to achieve discharge compliance.

Typical Treatment Stages

Stage Equipment Target Droplets Efficiency
Primary Hydrocyclone >20 μm 90-98%
Secondary IGF/DGF >5 μm 80-95%
Polishing Skim Tank >50 μm 60-80%

Basic Usage

import neqsim.process.equipment.watertreatment.ProducedWaterTreatmentTrain;
import neqsim.process.equipment.stream.Stream;

// Create treatment train
ProducedWaterTreatmentTrain train = new ProducedWaterTreatmentTrain(
    "PW Treatment", 
    producedWater
);

// Configure inlet conditions
train.setInletOilConcentration(1000.0);  // mg/L from separator
train.setWaterFlowRate(200.0);  // m³/h

// Run simulation
train.run();

// Check compliance
System.out.println("Outlet OIW: " + train.getOutletOilConcentration() + " mg/L");
System.out.println("Compliant: " + train.isCompliant());
System.out.println("Overall efficiency: " + (train.getOverallEfficiency() * 100) + "%");

Stage Types

import neqsim.process.equipment.watertreatment.ProducedWaterTreatmentTrain.StageType;

// Available stage types
StageType.HYDROCYCLONE    // Centrifugal separation
StageType.FLOTATION       // IGF/DGF units
StageType.SKIM_TANK       // Gravity separation
StageType.FILTER          // Filtration
StageType.MEMBRANE        // Membrane separation

Custom Stage Configuration

// Clear default stages
train.clearStages();

// Add custom stages
train.addStage("Primary Cyclone", StageType.HYDROCYCLONE, 0.95);
train.addStage("Compact Floatation", StageType.FLOTATION, 0.92);
train.addStage("Final Polish", StageType.SKIM_TANK, 0.75);

// Run with custom configuration
train.run();

Detailed Results

// Get stage-by-stage results
for (WaterTreatmentStage stage : train.getStages()) {
    System.out.println(stage.getName() + ":");
    System.out.println("  Inlet OIW: " + stage.getInletOilMgL() + " mg/L");
    System.out.println("  Outlet OIW: " + stage.getOutletOilMgL() + " mg/L");
    System.out.println("  Efficiency: " + (stage.getEfficiency() * 100) + "%");
}

// Get treated water and oil streams
Stream treatedWater = train.getTreatedWaterStream();
Stream recoveredOil = train.getRecoveredOilStream();

Design Considerations

Droplet Size Distribution

The performance of water treatment equipment depends heavily on the oil droplet size distribution in the feed:

Source Typical d50 Comments
HP Separator 100-300 μm Large droplets, easy separation
LP Separator 30-100 μm Moderate separation
Degasser 10-30 μm Fine droplets, challenging
Direct discharge <10 μm Very fine, requires flotation

Sizing Guidelines

// Hydrocyclone sizing (typical)
double feedFlowM3h = 200.0;
int numberOfLiners = (int) Math.ceil(feedFlowM3h / 35.0);  // ~35 m³/h per liner
double cycloneDP = 1.5 + 0.02 * feedFlowM3h / numberOfLiners;

// Flotation unit sizing
double retentionTime = 3.0;  // minutes
double flotationVolume = feedFlowM3h * retentionTime / 60.0;

Temperature Effects

Oil-water separation efficiency varies with temperature:

Regulatory Compliance

Norwegian Continental Shelf (NCS)

Requirement Limit Monitoring
Monthly average OIW 30 mg/L Weighted average
Dispersed oil Monitored Daily sampling
Zero discharge target Best available technology Continuous improvement

OSPAR Convention

Region OIW Limit Notes
North Sea 30 mg/L Monthly average
Atlantic 30 mg/L Monthly average

Compliance Checking

// Check against NCS requirements
boolean ncsCompliant = train.getOutletOilConcentration() 
    <= ProducedWaterTreatmentTrain.NCS_OIW_LIMIT_MGL;

// Check against OSPAR
boolean osparCompliant = train.getOutletOilConcentration() 
    <= ProducedWaterTreatmentTrain.OSPAR_OIW_LIMIT_MGL;

// Get compliance report
String report = train.getComplianceReport();
System.out.println(report);

Integration with Process Systems

Complete Process Example

import neqsim.process.processmodel.ProcessSystem;
import neqsim.process.equipment.separator.ThreePhaseSeparator;
import neqsim.process.equipment.watertreatment.ProducedWaterTreatmentTrain;

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

// Add production separator
ThreePhaseSeparator prodSep = new ThreePhaseSeparator("Production Separator", wellStream);
process.add(prodSep);

// Add water treatment train
ProducedWaterTreatmentTrain pwTrain = new ProducedWaterTreatmentTrain(
    "PW Treatment",
    prodSep.getWaterOutStream()
);
pwTrain.setInletOilConcentration(800.0);
process.add(pwTrain);

// Run process
process.run();

// Check results
System.out.println("Water cut: " + (prodSep.getWaterCut() * 100) + "%");
System.out.println("OIW to discharge: " + pwTrain.getOutletOilConcentration() + " mg/L");
System.out.println("Compliant: " + pwTrain.isCompliant());

See Also