Separator Equipment

Documentation for separator equipment in NeqSim process simulation.

Table of Contents

Overview

Location: neqsim.process.equipment.separator

Classes:

Separator Types

Two-Phase Separator

import neqsim.process.equipment.separator.Separator;

Separator separator = new Separator("V-100", inletStream);
separator.run();

// Get outlet streams
Stream gasOut = separator.getGasOutStream();
Stream liquidOut = separator.getLiquidOutStream();

// Properties
double gasRate = gasOut.getFlowRate("kg/hr");
double liquidRate = liquidOut.getFlowRate("kg/hr");
double liquidLevel = separator.getLiquidLevel();

Three-Phase Separator

import neqsim.process.equipment.separator.ThreePhaseSeparator;

ThreePhaseSeparator separator = new ThreePhaseSeparator("V-200", inletStream);
separator.run();

// Get outlet streams
Stream gasOut = separator.getGasOutStream();
Stream oilOut = separator.getOilOutStream();
Stream waterOut = separator.getWaterOutStream();

// Water cut
double waterCut = separator.getWaterCut();

Gas Scrubber

import neqsim.process.equipment.separator.GasScrubber;

GasScrubber scrubber = new GasScrubber("Inlet Scrubber", gasStream);
scrubber.run();

// Dry gas output
Stream dryGas = scrubber.getGasOutStream();

// Condensate removal
Stream condensate = scrubber.getLiquidOutStream();

Note: Gas scrubbers automatically use K-value only constraints (useGasScrubberConstraints()). This is appropriate since scrubbers focus on gas-phase separation efficiency rather than liquid retention time.

Horizontal Separator Design Parameters

Horizontal separators have specific geometry parameters for sizing and level calculations.

Vessel Geometry

Parameter Method Description Unit
Internal Diameter setInternalDiameter(value, unit) Vessel ID m
Length setLength(value, unit) Tan-to-tan length m
L/D Ratio getLengthDiameterRatio() Length to diameter ratio (design target: 3-5) -

Liquid Levels (Horizontal Separators)

Liquid levels are defined as percentages of internal diameter (ID). The mechanical design calculates absolute heights.

Level Method Description Default % of ID
HHLL getHHLL() High-High Liquid Level (alarm/shutdown) 75%
HLL getHLL() High Liquid Level (K-value reference) 70%
NLL getNLL() Normal Liquid Level (design point) 50%
LLL getLLL() Low Liquid Level (control warning) 30%
LLLL getLLLL() Low-Low Liquid Level (alarm/shutdown) 25% 
// Configure liquid levels (percentage of internal diameter)
SeparatorMechanicalDesign design = (SeparatorMechanicalDesign) separator.getMechanicalDesign();
design.setHHLLFraction(0.75);  // 75% of ID
design.setHLLFraction(0.70);   // 70% of ID  
design.setNLLFraction(0.50);   // 50% of ID
design.setLLLFraction(0.30);   // 30% of ID
design.setLLLLFraction(0.25);  // 25% of ID

// Calculate and retrieve absolute levels
design.calcDesign();
double hhlAbsolute = design.getHHLL();  // in meters
double hllAbsolute = design.getHLL();

Effective Lengths

For horizontal separators, effective lengths define zones for gas-liquid separation.

Parameter Method Description
Gas Effective Length getGasEffectiveLength() Length for gas separation (inlet to outlet nozzle)
Liquid Effective Length getLiquidEffectiveLength() Length for liquid settling 
// Get effective lengths for capacity calculations
double Leff_gas = separator.getMechanicalDesign().getGasEffectiveLength();
double Leff_liquid = separator.getMechanicalDesign().getLiquidEffectiveLength();

Pre-Designed Separator Setup

For existing/pre-designed separators, use the convenience methods:

// Option 1: Set from existing design
separator.setFromExistingDesign(
    2.5,    // internal diameter [m]
    10.0,   // length (tan-to-tan) [m]
    0.70,   // HLL fraction (% of ID)
    0.50,   // NLL fraction (% of ID)
    8.0,    // liquid effective length [m]
    9.0     // gas effective length [m]
);

// Option 2: Alternative design specification
separator.setFromDesignSpec(
    2.5,    // internal diameter [m]
    10.0,   // length [m]
    0.70,   // HLL fraction
    0.50    // NLL fraction
);
// Effective lengths default to 80% and 90% of total length

Three-Phase Separator Design Parameters

Three-phase separators have additional interface level parameters for oil-water separation.

Interface Levels

Level Method Description Default % of ID
HIL getHIL() High Interface Level 45%
NIL getNIL() Normal Interface Level (design point) 40%
LIL getLIL() Low Interface Level 35% 
// Configure interface levels
SeparatorMechanicalDesign design = (SeparatorMechanicalDesign) separator.getMechanicalDesign();
design.setHILFraction(0.45);  // 45% of ID
design.setNILFraction(0.40);  // 40% of ID
design.setLILFraction(0.35);  // 35% of ID

// Calculate designs
design.calcDesign();

// Get absolute interface levels
double nilAbsolute = design.getNIL();  // in meters

Weir Configuration

Three-phase separators typically use a weir to maintain the oil-water interface.

// Set weir height (typically at or slightly above NIL)
design.setWeirHeight(design.getNIL() * 1.05);  // 5% above NIL

Three-Phase Specific Calculations

ThreePhaseSeparator separator = new ThreePhaseSeparator("V-200", inletStream);
separator.setInternalDiameter(2.5, "m");
separator.setLength(12.0, "m");
separator.run();

// Oil retention time (from NLL to NIL)
double oilRetention = separator.calcOilRetentionTime();  // minutes

// Water retention time (from NIL to vessel bottom)
double waterRetention = separator.calcWaterRetentionTime();  // minutes

// Interface settling time
double settlingTime = separator.calcInterfaceSettlingTime();  // minutes

Gas Scrubber Design Parameters

Gas scrubbers (vertical separators) focus on gas phase quality with minimal liquid holdup.

Key Parameters

Parameter Method Description
Internal Diameter setInternalDiameter(value, unit) Vessel ID
Height setLength(value, unit) Tan-to-tan height
K-value calcKValueAtHLL() Souders-Brown coefficient

Automatic Constraint Configuration

Gas scrubbers automatically configure for K-value only constraints:

// GasScrubber constructor automatically calls useGasScrubberConstraints()
GasScrubber scrubber = new GasScrubber("Inlet Scrubber", gasStream);

// Only K-value constraint is active
// Droplet cut size, inlet momentum, and retention times are disabled

To verify or manually configure:

// Check active constraints
scrubber.getConstraints().forEach((type, constraint) -> {
    System.out.println(type + ": enabled=" + constraint.isEnabled());
});

// Manual configuration if needed
scrubber.useGasScrubberConstraints();  // Only K-value

Performance Constraints

NeqSim separators include a constraint system for performance monitoring and capacity analysis. Constraints are based on industry standards including Equinor TR3500 and API 12J.

⚠️ Important: All separator constraints are disabled by default for backward compatibility with the optimizer. Use the constraint selection methods (useEquinorConstraints(), useAPIConstraints(), useAllConstraints(), or enableConstraints()) to enable constraints for capacity analysis. The optimizer automatically falls back to traditional capacity methods when no enabled constraints exist.

For detailed information on how the optimizer handles constraints, see Capacity Constraint Framework - Constraints Disabled by Default.

Available Constraints

Constraint Type Parameter Limit Standard Reference
K-value (Souders-Brown) Gas load factor at HLL < 0.15 m/s Equinor TR3500, API 12J
Droplet Cut Size Minimum removed droplet < 150 µm Industry practice
Inlet Momentum Flux ρv² at inlet nozzle < 16,000 Pa Equinor revamp criteria
Oil Retention Time Oil phase residence ≥ 3 min API 12J
Water Retention Time Water phase residence ≥ 3 min API 12J

Performance Calculation Methods

// After running separator
separator.run();

// Calculate performance parameters
double kValue = separator.calcKValueAtHLL();           // m/s
double dropletSize = separator.calcDropletCutSizeAtHLL(); // µm  
double momentum = separator.calcInletMomentumFlux();   // Pa
double oilRetention = separator.calcOilRetentionTime();    // min
double waterRetention = separator.calcWaterRetentionTime(); // min

// Check against limits
boolean kOk = separator.isKValueWithinLimit();
boolean dropletOk = separator.isDropletCutSizeWithinLimit();
boolean momentumOk = separator.isInletMomentumWithinLimit();
boolean oilTimeOk = separator.isOilRetentionTimeAboveMinimum();
boolean waterTimeOk = separator.isWaterRetentionTimeAboveMinimum();

// Check all active constraints
boolean allOk = separator.isWithinAllLimits();

Performance Summary

Get a comprehensive performance summary with all metrics:

Map<String, Object> summary = separator.getPerformanceSummary();

// Summary includes:
// - kValue, kValueLimit, kValueWithinLimit
// - dropletCutSize, dropletCutSizeLimit, dropletCutSizeWithinLimit
// - inletMomentum, inletMomentumLimit, inletMomentumWithinLimit
// - oilRetentionTime, minOilRetentionTime, oilRetentionTimeOk
// - waterRetentionTime, minWaterRetentionTime, waterRetentionTimeOk
// - allConstraintsMet

Constraint Customization

Adjust constraint limits for specific project requirements:

// Set custom K-value limit (e.g., for high-pressure service)
separator.setKValueLimit(0.12);  // more conservative than default 0.15

// Set custom droplet cut size (e.g., for mist eliminator specification)
separator.setDropletCutSizeLimit(100.0);  // µm, stricter than 150 µm

// Set custom inlet momentum (e.g., for retrofit assessment)
separator.setInletMomentumLimit(12000.0);  // Pa, more conservative

// Set custom retention times (e.g., for emulsion handling)
separator.setMinOilRetentionTime(5.0);  // 5 minutes
separator.setMinWaterRetentionTime(5.0);  // 5 minutes

Constraint Selection Methods

Different separator types and applications require different constraint sets. NeqSim provides methods to select appropriate constraints.

Pre-Configured Constraint Sets

Method Constraints Enabled Use Case
useAllConstraints() All 5 constraints Full process separator analysis
useEquinorConstraints() K-value, Droplet, Momentum, Oil RT, Water RT Equinor TR3500 compliance
useAPIConstraints() K-value, Oil RT, Water RT API 12J compliance
useGasScrubberConstraints() K-value only Gas scrubbers, inlet separators
useGasCapacityConstraints() K-value, Droplet, Momentum Gas-focused analysis
useLiquidCapacityConstraints() Oil RT, Water RT Liquid-focused analysis

Usage Examples

// Scenario 1: Full process separator per Equinor standards
Separator hpSeparator = new Separator("HP Separator", feed);
hpSeparator.useEquinorConstraints();  // All 5 constraints per TR3500
hpSeparator.run();
boolean compliant = hpSeparator.isWithinAllLimits();

// Scenario 2: API 12J compliance check
ThreePhaseSeparator prodSep = new ThreePhaseSeparator("Production Sep", feed);
prodSep.useAPIConstraints();  // K-value + retention times per API 12J
prodSep.run();

// Scenario 3: Gas scrubber (automatic)
GasScrubber scrubber = new GasScrubber("Inlet Scrubber", gasStream);
// K-value only is already configured by constructor
scrubber.run();
double kValue = scrubber.calcKValueAtHLL();

// Scenario 4: Custom constraint selection
Separator testSep = new Separator("Test Sep", feed);
testSep.useConstraints(
    StandardConstraintType.SEPARATOR_K_VALUE,
    StandardConstraintType.SEPARATOR_INLET_MOMENTUM
);
// Only K-value and inlet momentum are checked

Manual Constraint Control

For fine-grained control over individual constraints:

// Disable specific constraints
separator.useAllConstraints();  // Start with all
CapacityConstraint momentumConstraint = 
    separator.getConstraints().get(StandardConstraintType.SEPARATOR_INLET_MOMENTUM);
momentumConstraint.setEnabled(false);  // Disable momentum check

// Enable/disable via Map iteration
separator.getConstraints().forEach((type, constraint) -> {
    if (type.toString().contains("RETENTION")) {
        constraint.setEnabled(false);  // Disable all retention time constraints
    }
});

Separator Sizing

Vertical Separator

// Set dimensions
separator.setInternalDiameter(2.0, "m");
separator.setLiquidVolume(10.0, "m3");

// Or specify residence time
separator.setLiquidResidenceTime(120.0, "sec");

Horizontal Separator

separator.setSeparatorType("horizontal");
separator.setLength(10.0, "m");
separator.setInternalDiameter(2.5, "m");

Dynamic Simulation

// Enable dynamic mode
separator.setCalculateSteadyState(false);

// Set initial conditions
separator.setLiquidLevel(0.5);  // 50% level

// Run transient
for (int i = 0; i < 100; i++) {
    separator.runTransient();
    
    double level = separator.getLiquidLevel();
    double pressure = separator.getPressure();
}

Separation Efficiency

// Set droplet removal efficiency
separator.setGasCarryUnderFraction(0.001);  // 0.1% liquid in gas
separator.setLiquidCarryOverFraction(0.0001); // 0.01% gas in liquid

Example: HP/LP Separation Train

// HP Separator at 50 bar
Separator hpSep = new Separator("HP Sep", feedStream);
process.add(hpSep);

// Letdown valve
ThrottlingValve lpValve = new ThrottlingValve("LP Valve", hpSep.getLiquidOutStream());
lpValve.setOutletPressure(5.0, "bara");
process.add(lpValve);

// LP Separator at 5 bar
Separator lpSep = new Separator("LP Sep", lpValve.getOutletStream());
process.add(lpSep);

// Run process
process.run();

// Total gas production
double hpGas = hpSep.getGasOutStream().getFlowRate("MSm3/day");
double lpGas = lpSep.getGasOutStream().getFlowRate("MSm3/day");
double totalGas = hpGas + lpGas;

Gas Load Factor (K-Factor)

The gas load factor (Souders-Brown coefficient) is used for separator sizing and capacity analysis:

// Get current gas load factor
double kFactor = separator.getGasLoadFactor();

// Set design K-factor for sizing
separator.setDesignGasLoadFactor(0.10);  // Typical for horizontal separator
separator.setDesignGasLoadFactor(0.07);  // Typical for vertical scrubber

Dry Gas Handling

For dry gas or single-phase systems (e.g., gas scrubbers with no liquid), the gas load factor calculation uses a default liquid density of 1000 kg/m³. This allows capacity calculations to work correctly even when no liquid phase is present:

// Dry gas scrubber - liquid density defaults to 1000 kg/m3
GasScrubber scrubber = new GasScrubber("Inlet Scrubber", dryGasStream);
scrubber.run();
double kFactor = scrubber.getGasLoadFactor();  // Uses 1000 kg/m3 for liquid reference

Auto-Sizing

Separators implement the AutoSizeable interface for automatic sizing based on flow conditions:

// Auto-size with 20% safety factor (default)
separator.autoSize();

// Auto-size with custom safety factor
separator.autoSize(1.3);  // 30% margin

// Auto-size per company standards
separator.autoSize("Equinor", "TR2000");

// Get sizing report
System.out.println(separator.getSizingReport());
System.out.println(separator.getSizingReportJson());

Constraint Utilization and Bottleneck Analysis

Constraints integrate with NeqSim’s bottleneck analysis framework for capacity assessment.

Utilization Calculation

Each constraint calculates utilization as a percentage of its limit:

separator.run();

// Get constraint utilizations
Map<StandardConstraintType, CapacityConstraint> constraints = separator.getConstraints();

for (Map.Entry<StandardConstraintType, CapacityConstraint> entry : constraints.entrySet()) {
    CapacityConstraint c = entry.getValue();
    if (c.isEnabled()) {
        System.out.printf("%s: %.1f%% utilization%n", 
            entry.getKey(), c.getUtilizationPercentage());
    }
}

// Example output:
// SEPARATOR_K_VALUE: 78.5% utilization
// SEPARATOR_DROPLET_CUTSIZE: 92.3% utilization
// SEPARATOR_INLET_MOMENTUM: 45.2% utilization
// SEPARATOR_OIL_RETENTION_TIME: 110.5% utilization (over limit!)
// SEPARATOR_WATER_RETENTION_TIME: 85.0% utilization

Identifying Bottlenecks

// Find limiting constraint
StandardConstraintType bottleneck = null;
double maxUtilization = 0;

for (Map.Entry<StandardConstraintType, CapacityConstraint> entry : 
        separator.getConstraints().entrySet()) {
    CapacityConstraint c = entry.getValue();
    if (c.isEnabled() && c.getUtilizationPercentage() > maxUtilization) {
        maxUtilization = c.getUtilizationPercentage();
        bottleneck = entry.getKey();
    }
}

System.out.println("Bottleneck: " + bottleneck + " at " + maxUtilization + "%");

JSON Output with Performance Metrics

The SeparatorResponse class provides comprehensive JSON output including performance metrics:

// Get JSON report
String json = separator.toJson();

Example JSON output:

{
  "name": "HP Separator",
  "type": "Separator",
  "internalDiameter_m": 2.5,
  "length_m": 10.0,
  "pressure_bara": 50.0,
  "temperature_C": 45.0,
  "gasFlowRate_Sm3_hr": 150000.0,
  "liquidFlowRate_m3_hr": 25.0,
  "performanceMetrics": {
    "kValue_m_s": 0.098,
    "kValueLimit_m_s": 0.15,
    "kValueWithinLimit": true,
    "dropletCutSize_um": 125.3,
    "dropletCutSizeLimit_um": 150.0,
    "dropletCutSizeWithinLimit": true,
    "inletMomentum_Pa": 8500.0,
    "inletMomentumLimit_Pa": 16000.0,
    "inletMomentumWithinLimit": true,
    "oilRetentionTime_min": 4.2,
    "minOilRetentionTime_min": 3.0,
    "oilRetentionTimeOk": true,
    "waterRetentionTime_min": 3.8,
    "minWaterRetentionTime_min": 3.0,
    "waterRetentionTimeOk": true,
    "allConstraintsMet": true
  }
}

Design Standards Reference

Equinor TR3500 Requirements

Parameter Requirement Description
K-value ≤ 0.15 m/s Souders-Brown at HLL
Droplet cut size ≤ 150 µm At HLL conditions
Inlet momentum ≤ 16,000 Pa For revamp assessment
Retention time ≥ 3 min For oil and water phases

API 12J Guidelines

Parameter Requirement Description
K-value ≤ 0.107 m/s More conservative for oilfield use
Liquid retention ≥ 3 min Oil and water phases
L/D ratio 3:1 to 5:1 Horizontal separator design

Application by Equipment Type

Equipment Primary Constraints Secondary Constraints
Two-Phase Separator K-value, Oil RT Droplet, Momentum
Three-Phase Separator K-value, Oil RT, Water RT Droplet, Momentum
Gas Scrubber K-value only -
Inlet Separator K-value, Momentum -
Test Separator Oil RT, Water RT K-value

Complete Example: Separator Design and Constraint Check

import neqsim.process.equipment.separator.ThreePhaseSeparator;
import neqsim.process.equipment.stream.Stream;
import neqsim.thermo.system.SystemSrkEos;

// Create feed
SystemSrkEos fluid = new SystemSrkEos(273.15 + 45, 50.0);
fluid.addComponent("methane", 100.0);
fluid.addComponent("n-heptane", 30.0);
fluid.addComponent("water", 10.0);
fluid.setMixingRule("classic");
fluid.setMultiPhaseCheck(true);

Stream feed = new Stream("Feed", fluid);
feed.setFlowRate(100000, "kg/hr");
feed.run();

// Create separator with pre-designed dimensions
ThreePhaseSeparator separator = new ThreePhaseSeparator("Production Sep", feed);
separator.setFromExistingDesign(
    2.5,    // ID [m]
    10.0,   // Length [m]
    0.70,   // HLL fraction
    0.50,   // NLL fraction
    8.0,    // Liquid Leff [m]
    9.0     // Gas Leff [m]
);

// Apply Equinor TR3500 constraints
separator.useEquinorConstraints();

// Customize retention time for heavy crude
separator.setMinOilRetentionTime(5.0);  // 5 min for emulsion
separator.setMinWaterRetentionTime(5.0);

// Run simulation
separator.run();

// Check performance
System.out.println("=== Separator Performance ===");
System.out.printf("K-value: %.3f m/s (limit: %.3f) - %s%n",
    separator.calcKValueAtHLL(),
    separator.getKValueLimit(),
    separator.isKValueWithinLimit() ? "OK" : "EXCEEDED");

System.out.printf("Droplet cut size: %.1f µm (limit: %.1f) - %s%n",
    separator.calcDropletCutSizeAtHLL(),
    separator.getDropletCutSizeLimit(),
    separator.isDropletCutSizeWithinLimit() ? "OK" : "EXCEEDED");

System.out.printf("Inlet momentum: %.0f Pa (limit: %.0f) - %s%n",
    separator.calcInletMomentumFlux(),
    separator.getInletMomentumLimit(),
    separator.isInletMomentumWithinLimit() ? "OK" : "EXCEEDED");

System.out.printf("Oil retention: %.1f min (min: %.1f) - %s%n",
    separator.calcOilRetentionTime(),
    separator.getMinOilRetentionTime(),
    separator.isOilRetentionTimeAboveMinimum() ? "OK" : "INSUFFICIENT");

System.out.printf("Water retention: %.1f min (min: %.1f) - %s%n",
    separator.calcWaterRetentionTime(),
    separator.getMinWaterRetentionTime(),
    separator.isWaterRetentionTimeAboveMinimum() ? "OK" : "INSUFFICIENT");

System.out.println("\nAll constraints met: " + separator.isWithinAllLimits());

// Get full JSON report
System.out.println("\n" + separator.toJson());