git:20260406.0a42c84 to git:20260418.a3c26d6

1 added, 0 removed. Audit A to A.

---

name: neqsim-ccs-hydrogen

description: "CO2 capture, transport, storage (CCS) and hydrogen systems patterns for NeqSim. USE WHEN: modeling CO2 pipelines, injection wells, impurity effects on phase behavior, CO2 dense phase transport, hydrogen blending, electrolysis, or any CCS/H2 value chain analysis. Covers CO2 phase behavior, impurity management, well integrity, and hydrogen systems."

+ last_verified: "2026-07-04"

---

# CCS and Hydrogen Systems with NeqSim

Guide for modeling carbon capture and storage (CCS) value chains and hydrogen

systems, including CO2 transport, injection wells, impurity effects, and H2 blending.

## When to Use This Skill

- CO2 pipeline design and phase behavior

- CO2 injection well analysis and safety

- Impurity effects on CO2 phase envelope (H2, N2, O2, H2S, CH4)

- Dense phase CO2 transport conditions

- CO2 dehydration requirements

- Hydrogen blending with natural gas

- Water electrolysis and green hydrogen

- Blue hydrogen (SMR/ATR + CCS)

- Hydrogen pipeline transport

## Applicable Standards

| Domain | Standards | Key Requirements |

|--------|-----------|-----------------|

| CO2 pipeline | DNV-RP-F104, ISO 27913 | CO2 pipeline design, impurity limits |

| CO2 storage | ISO 27914, EU CCS Directive | Storage site characterization |

| CO2 transport | ISO 27913 | Composition specs, phase management |

| CO2 quality | ISO 27916 | CO2 stream specification |

| Hydrogen pipeline | ASME B31.12 | H2 piping and pipelines |

| Hydrogen quality | ISO 14687 (fuel cell), EN 16726 (grid) | Purity requirements |

## 1. CO2 Phase Behavior

### CO2 Critical Point and Phase Envelope

CO2 critical point: 31.1°C, 73.8 bara. Most CO2 pipelines operate in dense phase

(above critical pressure) to avoid two-phase flow.

```java

// Pure CO2 phase behavior

SystemInterface co2 = new SystemSrkEos(273.15 + 25, 80.0);

co2.addComponent("CO2", 1.0);

co2.setMixingRule("classic");

ThermodynamicOperations ops = new ThermodynamicOperations(co2);

ops.calcPTphaseEnvelope();

// CO2 is in dense/supercritical phase at typical pipeline conditions (>80 bara, 4-40°C)

```

### Impurity Effects on CO2 Phase Envelope

Impurities widen the phase envelope and raise the cricondenbar, creating risk

of two-phase flow in pipelines designed for dense phase operation.

```java

// CO2 with typical impurities from post-combustion capture

SystemInterface co2Mix = new SystemSrkEos(273.15 + 10, 110.0);

co2Mix.addComponent("CO2", 0.95);

co2Mix.addComponent("nitrogen", 0.02);

co2Mix.addComponent("oxygen", 0.005);

co2Mix.addComponent("water", 0.005);

co2Mix.addComponent("H2S", 0.001);

co2Mix.addComponent("hydrogen", 0.005);

co2Mix.addComponent("methane", 0.014);

co2Mix.setMixingRule("classic");

co2Mix.setMultiPhaseCheck(true);

ThermodynamicOperations ops = new ThermodynamicOperations(co2Mix);

ops.calcPTphaseEnvelope();

// Compare cricondenbar with pure CO2 — impurities raise it significantly

// N2, H2, O2 have the largest effect on raising cricondenbar

```

### Impurity Impact Ranking (on phase envelope)

|----------|----------------------|-------------------|----------------|

| H2O | Minimal on vapor | — | Corrosion with CO2 |

## 2. CO2 Pipeline Design

### Dense Phase Transport

```java

// Typical CO2 pipeline: 110 bara inlet, 80 bara min, 4-40°C

Stream co2Feed = new Stream("CO2 Feed", co2Mix);

co2Feed.setFlowRate(1000000.0, "kg/hr"); // ~1 Mt/yr

co2Feed.setTemperature(25.0, "C");

co2Feed.setPressure(110.0, "bara");

PipeBeggsAndBrills pipeline = new PipeBeggsAndBrills("CO2 Pipeline", co2Feed);

pipeline.setLength(150000.0); // 150 km

pipeline.setDiameter(0.508); // 20 inch

pipeline.setPipeWallRoughness(5e-5);

pipeline.setOuterTemperature(277.15); // 4°C seabed

pipeline.run();

double outP = pipeline.getOutletStream().getPressure();

double outT = pipeline.getOutletStream().getTemperature() - 273.15;

// Verify: outlet P > cricondenbar to stay in dense phase

```

### CO2 Dehydration Requirement

```java

// Water content must be below ~50 ppmv to prevent hydrate and corrosion

// Use CPA for accurate water in CO2 modeling

SystemInterface wetCO2 = new SystemSrkCPAstatoil(273.15 + 25, 110.0);

wetCO2.addComponent("CO2", 0.99);

wetCO2.addComponent("water", 0.01);

wetCO2.setMixingRule(10);

wetCO2.setMultiPhaseCheck(true);

ThermodynamicOperations ops = new ThermodynamicOperations(wetCO2);

ops.TPflash();

wetCO2.initProperties();

// Check water content in CO2-rich phase

double waterInCO2 = wetCO2.getPhase("gas").getComponent("water").getx();

// Convert to ppmv and compare with spec (typically <50 ppmv)

```

## 3. CO2 Injection Well Analysis

### Full-Stack Well Analysis

```java

CO2InjectionWellAnalyzer analyzer = new CO2InjectionWellAnalyzer("InjWell-1");

analyzer.setFluid(co2Fluid);

analyzer.setWellGeometry(1300.0, 0.1571, 5e-5); // depth, ID, roughness

analyzer.setOperatingConditions(90.0, 25.0, 150000.0); // P, T, flow

analyzer.setFormationTemperature(4.0, 43.0); // surface T, bottomhole T

analyzer.addTrackedComponent("hydrogen", 0.10); // impurity limit

analyzer.runFullAnalysis();

boolean safe = analyzer.isSafeToOperate();

// Checks: phase transitions in wellbore, impurity enrichment, thermal stress

```

### Wellbore Temperature Profile

```java

PipeBeggsAndBrills wellbore = new PipeBeggsAndBrills("CO2 Injector", co2Feed);

wellbore.setLength(1300.0);

wellbore.setElevation(-1300.0); // vertical injection well

wellbore.setDiameter(0.1571); // 6-5/8 inch tubing

wellbore.setPipeWallRoughness(5e-5);

wellbore.setFormationTemperatureGradient(4.0, -0.03, "C");

wellbore.run();

double bhp = wellbore.getOutletStream().getPressure();

double bht = wellbore.getOutletStream().getTemperature() - 273.15;

```

### Impurity Enrichment Monitoring

During phase transitions in the wellbore, light impurities (H2, N2) concentrate

in the gas phase, potentially exceeding well material limits.

```java

ImpurityMonitor monitor = new ImpurityMonitor("H2-Monitor", stream);

monitor.addTrackedComponent("hydrogen", 0.10); // 10 mol% limit

monitor.addTrackedComponent("H2S", 0.001); // 0.1% limit

monitor.addTrackedComponent("oxygen", 0.005); // 0.5% limit

double h2Enrichment = monitor.getEnrichmentFactor("hydrogen");

boolean h2Safe = !monitor.exceedsLimit("hydrogen");

```

### Shutdown Transient Analysis

```java

TransientWellbore wellbore = new TransientWellbore("Shutdown", co2Feed);

wellbore.setWellDepth(1300.0);

wellbore.setFormationTemperature(277.15, 316.15); // surface, bottom (K)

wellbore.setShutdownCoolingRate(6.0); // °C/hr cooling rate

wellbore.runShutdownSimulation(48.0, 1.0); // 48 hours, 1 hr timestep

// Check for phase transition during cooldown

// Risk: CO2 may transition to two-phase, causing pressure surges

```

### CO2 Flow Corrections

```java

// Static utility for CO2-specific flow adjustments

boolean dense = CO2FlowCorrections.isDensePhase(system);

double holdupCorr = CO2FlowCorrections.getLiquidHoldupCorrectionFactor(system);

// Dense phase CO2 requires modified correlations for pressure drop

```

## 4. Hydrogen Systems

### Hydrogen Blending with Natural Gas

```java

// Evaluate H2 blending impact on existing gas network

SystemInterface blendedGas = new SystemSrkEos(273.15 + 15, 70.0);

blendedGas.addComponent("hydrogen", 0.10); // 10% H2 blend

blendedGas.addComponent("methane", 0.81);

blendedGas.addComponent("ethane", 0.05);

blendedGas.addComponent("propane", 0.02);

blendedGas.addComponent("nitrogen", 0.02);

blendedGas.setMixingRule("classic");

ThermodynamicOperations ops = new ThermodynamicOperations(blendedGas);

ops.TPflash();

blendedGas.initProperties();

// Key impacts of H2 blending:

double density = blendedGas.getDensity("kg/m3"); // Decreases with H2

double gcv = blendedGas.getPhase("gas").getCp("J/kgK"); // Changes energy content

double z = blendedGas.getZ(); // Compressibility changes

// For Wobbe index and calorific value:

Standard_ISO6976 iso = new Standard_ISO6976(blendedGas);

iso.calculate();

double wobbe = iso.getValue("SuperiorWobbeIndex");

// H2 reduces Wobbe index — check against pipeline spec limits

```

### Hydrogen Pipeline Transport

```java

// H2 has very low density — requires higher velocities or larger diameters

Stream h2Feed = new Stream("H2 Feed", h2Fluid);

h2Feed.setFlowRate(10000.0, "kg/hr");

h2Feed.setPressure(70.0, "bara");

PipeBeggsAndBrills h2Pipe = new PipeBeggsAndBrills("H2 Pipeline", h2Feed);

h2Pipe.setLength(100000.0); // 100 km

h2Pipe.setDiameter(0.508); // 20 inch

h2Pipe.setPipeWallRoughness(5e-5);

h2Pipe.run();

// H2 pressure drop is lower per unit mass but energy density is much lower

// Consider: material compatibility (H2 embrittlement), safety zones

```

### Blue Hydrogen (SMR + CCS)

```java

// Steam Methane Reforming produces H2 + CO2

// CH4 + H2O -> CO + 3H2 (reforming)

// CO + H2O -> CO2 + H2 (water-gas shift)

// Model with GibbsReactor for equilibrium

SystemInterface syngasFluid = new SystemSrkEos(273.15 + 850, 30.0);

syngasFluid.addComponent("methane", 0.25);

syngasFluid.addComponent("water", 0.75);

syngasFluid.setMixingRule("classic");

GibbsReactor reformer = new GibbsReactor("SMR", syngasFeed);

reformer.run();

// Outlet: H2, CO, CO2, H2O, unconverted CH4

```

## 5. CCS Value Chain Integration

### Capture → Transport → Storage Workflow

```java

// 1. Post-combustion capture outlet (after amine scrubbing)

SystemInterface capturedCO2 = new SystemSrkEos(273.15 + 40, 2.0);

capturedCO2.addComponent("CO2", 0.995);

capturedCO2.addComponent("nitrogen", 0.003);

capturedCO2.addComponent("water", 0.002);

capturedCO2.setMixingRule("classic");

// 2. Compression to pipeline pressure

Stream co2Stream = new Stream("Captured CO2", capturedCO2);

co2Stream.setFlowRate(500000.0, "kg/hr");

// Multi-stage compression with intercooling

Compressor comp1 = new Compressor("Stage 1", co2Stream);

comp1.setOutletPressure(5.0);

Cooler cooler1 = new Cooler("IC 1", comp1.getOutletStream());

cooler1.setOutTemperature(273.15 + 30);

Compressor comp2 = new Compressor("Stage 2", cooler1.getOutletStream());

comp2.setOutletPressure(20.0);

Cooler cooler2 = new Cooler("IC 2", comp2.getOutletStream());

cooler2.setOutTemperature(273.15 + 30);

Compressor comp3 = new Compressor("Stage 3", cooler2.getOutletStream());

comp3.setOutletPressure(80.0);

Cooler cooler3 = new Cooler("IC 3", comp3.getOutletStream());

cooler3.setOutTemperature(273.15 + 30);

// 3. Pump to pipeline pressure (above critical — dense phase)

// CO2 is liquid above ~65 bara at 30°C, pump is more efficient than compressor

Compressor pump = new Compressor("Pump", cooler3.getOutletStream());

pump.setOutletPressure(150.0);

// 4. Pipeline transport

PipeBeggsAndBrills pipeline = new PipeBeggsAndBrills("CO2 Export", pump.getOutletStream());

pipeline.setLength(200000.0); // 200 km

pipeline.setDiameter(0.508);

pipeline.setOuterTemperature(277.15);

// 5. Injection well

// See CO2InjectionWellAnalyzer above

ProcessSystem ccsProcess = new ProcessSystem();

ccsProcess.add(co2Stream);

ccsProcess.add(comp1); ccsProcess.add(cooler1);

ccsProcess.add(comp2); ccsProcess.add(cooler2);

ccsProcess.add(comp3); ccsProcess.add(cooler3);

ccsProcess.add(pump);

ccsProcess.add(pipeline);

ccsProcess.run();

double totalPower = comp1.getPower("kW") + comp2.getPower("kW")

+ comp3.getPower("kW") + pump.getPower("kW");

```

## 6. Common Pitfalls

| Pitfall | Solution |

|---------|----------|

| CO2 two-phase in pipeline | Ensure P > cricondenbar (account for impurities) |

| Using SRK for CO2+water | Use CPA (`SystemSrkCPAstatoil`) for accurate water solubility |

| Ignoring impurity effect on phase envelope | Always calculate phase envelope with impurities included |

| H2 density too high | Verify EOS handles low-density H2 correctly at high P |

| CO2 injection below fracture P | Check bottomhole P vs formation fracture gradient |

| Ignoring JT cooling in CO2 expansion | CO2 expands significantly — can cause solid CO2 below -56.6°C |

| Hydrogen embrittlement not flagged | Use ASME B31.12 for H2 service; flag H2 partial pressure > limits |