Geothermal NCG Abatement: H2S Capture & Parasitic Power Loss

Steam & Gas Feed

Separator steam flow 60 kg/s

Non-condensable gas fraction 1.0%

H₂S share of NCG 6%

Catalytic abatement efficiency 90%

Live Readouts

NCG flow

— kg/hr

H₂S generated

— kg/hr

H₂S emitted

— kg/hr

Sulfur captured

0.0 kg

Parasitic loss

— MW

Net plant power

— MW

How it works

Geothermal steam always carries a slice of non-condensable gas (NCG) — mostly CO₂ with a smaller H₂S fraction — that separates from the condensate and must be pulled off the condenser with steam-jet ejectors, then scrubbed before venting. This model tracks that gas train end to end:

NCG flow    = steam flow × NCG fraction
H2S flow    = NCG flow × H2S share
H2S emitted = H2S flow × (1 − abatement efficiency)
S captured  = 0.94 × H2S flow × abatement efficiency  (mass ratio S/H2S)

Parasitic steam = NCG flow × 3  (motive steam per kg NCG, typical ejector train)
Parasitic power = parasitic steam × 700 kJ/kg / 1000
Net power       = steam flow × 700 kJ/kg / 1000 − parasitic power

Separator steam flow — total mass flow reaching the turbine train; scales both the useful power and the NCG carried with it.
NCG fraction — how gassy the resource is; high-NCG fields (e.g. parts of The Geysers) can exceed 1–2% by mass.
H₂S share of NCG — the rest is mostly CO₂; H₂S is the regulated, odorous component that abatement targets.
Abatement efficiency — conversion rate of a catalytic/liquid-redox unit (e.g. Stretford- or LO-CAT-type) that oxidizes H₂S to elemental sulfur before the residual gas is vented from the stack.
Yellow particles are NCG parcels leaving the separator; a fraction turn dark and settle onto the catalyst bed (captured as sulfur), the rest ride the ejector to the stack and disperse as plume — visually proportional to the efficiency slider, exactly as the readouts compute it.
The ejector's motive steam is diverted from the turbine, which is why higher NCG (more gas to remove) quietly costs net power even though it never touches the turbine blades.

NCG / H₂S parcel Captured sulfur Vented plume

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Geothermal NCG Abatement: H₂S Capture & Parasitic Power Loss