PSA Biogas Upgrading Sizing

Engineering Basis

• Cycle-based sizing: M_bed = (CO₂_load_per_min × t_ads_step) / WC; one bed adsorbing at all times in N-bed synchronous PSA.
• Recovery vs slip: 2-bed 80% / 4-bed 93% / 6-bed 96.5% / 8-bed 98.5% — bed count drives recovery via pressure-equalization opportunities.
• Working capacities: CMS 0.10 / 13X 0.15 / 4A 0.08 / AC 0.12 kg CO₂/kg at 6–7 bar adsorption.
• Methane slip CO₂e: (1−η_recovery) × CH₄_feed × (1−CE_offgas) × GWP_CH4 — major CARB LCFS pathway CI driver.
• Compression: isentropic W = c_p·T·[(P₂/P₁)^((γ−1)/γ) − 1] for γ=1.30 biogas; η_comp × η_motor losses.
• Off-gas combustion: flare 95% / RTO 99.5% / RNG engine 98.5% / vent 0%.
• Standards: Yang/Ruthven PSA, GPSA 14e §17, 40 CFR 80.1426 (RFS2 D3), CARB LCFS §95488, IPCC AR6.