CO₂ Flow Measurement for Carbon Capture & Storage (CCS)

Carbon capture, utilisation, and storage (CCUS) is central to global net-zero pathways. The EU, UK, and US are committing billions to CCUS infrastructure. Accurate CO₂ flow measurement is critical for operational optimisation, regulatory compliance, and emissions trading. But CO₂ measurement presents unique challenges across the CCUS value chain.

CCUS Measurement Points

Capture (10–100 bar, variable composition)

• Point source (cement, steel, power generation): 20–40°C, 1–5 bar (flue gas)
• Direct air capture (DAC): 30–40°C, 1 bar (atmospheric air with CO₂)
• Challenge: Flue gas contains water vapour, NOx, SOx; DAC contains trace gases

Dehydration and Compression (40–150 bar, near-pure CO₂)

• Compressed to 40–150 bar for pipeline transport
• Temperature: 15–40°C (cooled from compression)
• Measurement critical for flow rate and energy optimisation

Pipeline Transport (80–150 bar, ambient temperature)

• Long-distance pipelines: 50–300 km
• Accuracy requirement: ±0.5% (financial custody transfer)
• Challenge: CO₂ density changes with pressure/temperature variation along pipeline

Injection and Storage (100–400 bar, supercritical conditions)

• Geological storage: Deep underground at >31.1°C and >73.8 bar (supercritical state)
• Measurement ensures specified injection rate; regulatory monitoring

CO₂ Physical Properties and Challenges

Density Variation (Supercritical Region)

• Gaseous CO₂ (1 bar, 20°C): 1.98 kg/m³
• Liquid CO₂ (15 bar, 20°C): 771 kg/m³
• Supercritical CO₂ (100 bar, 35°C): 764 kg/m³ (nearly liquid-like density)
• Supercritical CO₂ (200 bar, 35°C): 855 kg/m³
• Implication: Density changes 15–20% across typical pipeline pressure variation (80–150 bar); volumetric metres must be compensated

Critical Point

• CO₂ critical point: 31.1°C, 73.8 bar
• Above this point: no liquid-gas phase boundary; supercritical fluid
• Challenge: Measurement equations differ for supercritical vs liquid/gas

Recommended Measurement Technologies

Coriolis Metres (Custody Transfer, High Accuracy)

• Principle: Direct mass flow measurement (density-independent)
• Accuracy: ±0.2–0.5% (suitable for financial custody transfer)
• Cost: £8,000–£25,000 (depending on line size and pressure rating)
• Applications: Pipeline entry/exit metering, injection well flow control
• Advantage: Handles supercritical region without compensation

Ultrasonic Metres (Pipeline Transport)

• Principle: Measure velocity (volumetric); require P/T compensation for mass
• Accuracy: ±1% (with accurate pressure/temperature measurement)
• Cost: £4,000–£12,000
• Applications: Long-distance pipeline metering
• Limitation: Accuracy sensitive to CO₂ property tables in supercritical region

Differential Pressure (DP) Metres (Large Pipelines)

• Principle: Measure pressure drop across orifice plate; infer volumetric flow
• Accuracy: ±2–3% (moderate)
• Cost: £1,500–£3,000 (economical for large diameters)
• Applications: Trunk pipeline, where modest accuracy acceptable

Regulatory and Compliance Requirements

Emissions Trading System (ETS)

• EU ETS requires ±2.5% accuracy for CO₂ emissions reporting
• Verified measurements qualify for carbon credits
• Non-compliance penalties: €100/tonne CO₂ under-reported

CCUS Standards (Emerging)

• ISO 27912 (draft): CO₂ measurement for CCUS systems
• API RP 78 (American Petroleum Institute): CO₂ pipelines measurement guidance

Permanent Storage Certification

• Geological storage sites require lifetime monitoring of injected CO₂ mass
• Accurate metres essential for regulatory compliance and liability proof

Cost and Market Growth

CCUS Market Outlook:

• 2026: First commercial CO₂ pipelines operational; measurement infrastructure critical
• 2030: EU target 280 Mt/year CCUS capacity; UK 10 Mt/year by 2030
• Investment: UK CCUS hubs (Acorn, East Coast Cluster) worth £billions; measurement equipment essential component

Typical Project Cost Breakdown (100 km pipeline):

• Pipeline construction: £500–£1,000/metre = £50–£100M
• Measurement equipment: £500k–£2M (0.5–2% of capital)
• Custody transfer metres: 3–5 Coriolis metres @ £15k each = £45–£75k
• Inline monitoring: 10–15 ultrasonic metres @ £8k each = £80–£120k

Summary

CO₂ flow measurement for CCUS requires accuracy suitable for custody transfer and regulatory compliance. Coriolis metres are optimal for high-accuracy applications (pipelines, injection wells); ultrasonic with proper P/T compensation for long-distance transport. As CCUS infrastructure scales globally, measurement technology becomes increasingly central to operational excellence and regulatory accountability. UK and EU CCUS hubs creating immediate demand for high-quality CO₂ metres.