SGERG-mod-H2 Details
SGERG-mod-H2 is a modification of SGERG-88 (ISO 12213-3) for hydrogen-blended natural gas, developed by DVGW and DBI Gastechnologisches Institut. It removes the historical CO coupling (where CO content was derived from H₂ via the Stadtgas relationship X_CO = 0.0964·X_H₂) and extends the validity range to accommodate gases with up to 30 mol% hydrogen and a relative density as low as 0.06.

SGERG-mod-H2 is mandated by DVGW Arbeitsblatt G 685-6 (A) August 2024 for the calculation of the billing compressibility factor (Abrechnungszustandszahl K) when the hydrogen content exceeds 10 mol%.

SGERG-mod-H2 Application Restrictions (DVGW G 685-6, Tabelle B.4):
Pressure: 0 MPa to 12 MPa (0 to 120 bar; > 2.6 MPa no longer state of the art)
Temperature: 263 K to 338 K (−10 °C to 65 °C)
Superior Calorific Value: 6 MJ/m³ to 45 MJ/m³ (≈ 1.7 to 12.5 kWh/m³)
Relative Density: 0.06 to 0.80
H₂ content: 0 to 0.30 mol/mol
CO₂ content: 0 to 0.20 mol/mol (extended to 0.30*)

SGERG-mod-H2 References:
DVGW Arbeitsblatt G 685-6 (A) August 2024 — Abrechnungsbrennwert und Abrechnungszustandszahl
DVGW Research Report DBI GUT 0083H — SGERG-88-mod-H2 (English)
ISO 12213-3:1997 Natural gas — Calculation of compression factor — Part 3 (base standard, paid)