Decarbonization›CO₂ Pipeline Depressurization
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CO₂ Pipeline Depressurization

Decarbonization · J-T cooling · Brittle-fracture risk · Emergency blowdown

Emergency Blowdown — J-T Cooling Screen
Estimates pipeline inventory, blowdown time, and minimum metal temperature reached during emergency depressurization. The severe Joule-Thomson cooling on dense-phase CO₂ expansion can drop temperatures below standard carbon-steel MAT (-29 °C), driving requirement for low-temperature carbon steel (LTCS).

Pipeline Inventory

mm
km
bara
°C

Blowdown System

mm
—
bara

Steel Selection

°C

Typical: standard carbon steel −29 °C; LTCS −46 °C; cryo grade −100 °C.

📚 Learn the Theory

Emergency blowdown of CO₂ pipelines: J-T cooling, sublimation floor, brittle-fracture risk, and steel grade selection (LTCS vs cryogenic).

Read Engineering Guide →

Engineering Basis

  • Inventory from PR-Peneloux dense-phase density × pipe volume.
  • Blowdown time from sonic-choked orifice flow (k=1.30, Z=0.85), τ = m / m_dot, full blowdown ≈ 4·τ.
  • Minimum metal T from isentropic expansion T₂ = T₁·(P₂/P₁)^((k-1)/k), floored at sublimation T at outlet pressure (-78.5 °C @ 1 bara), with environmental warming correction (5–10 °C).
  • Brittle-fracture criterion: T_min ≥ MAT of selected steel grade.
  • Standards: DNV-RP-J202 §11, ISO 12747, API 521, ASME B31.4, BS 7910.
  • Screening only — final design requires dynamic blowdown simulation (BLOW3, OLGA, K-Spice, Aspen HYSYS Dynamics).

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