Gas-quality blending + tariff compliance
Computes blended gas quality (HHV, Specific Gravity, Wobbe Index, Methane Number, inerts) when RNG is injected into a receiving pipeline, then verifies against pipeline tariff envelope per AGA Report 4 / GPA 2145-16 / ASTM D3588 / NGC+ Interchangeability. Pure RNG typically has Wobbe at or below SoCalGas Rule 30 minimum (1290) — blending with higher-Wobbe pipeline gas or propane enrichment is usually required for injection.
Methane Number simplified component-weighted approximation — for engine warranty use vendor AVL/MWM test.
Pipeline tariff: SoCalGas Rule 30 (1290–1385) / El Paso (1330–1475) / typical US interstate (1300–1400).
Pure RNG (96–99% CH₄) has Wobbe ~1285 — typically below SoCalGas minimum without blending or propane enrichment.
Compression: multi-stage, N = ⌈ln r / ln 4⌉ stages (per-stage ratio capped ≈4:1, intercooled to suction T₁), W = N·c_p·T₁·[r_s^((γ−1)/γ) − 1] for CH₄-rich (γ=1.31); per-stage discharge temperature reported and flagged above ~300–350°F.
Standards: AGA Report 4 / 5, GPA 2145-16, ASTM D1945 / D3588, ISO 6976:2016, NGC+ Interchangeability, SAE J1616.