Air Capture and Basalt Storage

What is modelled

Air passes through a contactor and the sorbent removes a fraction of its CO2. The bed fills until its working capacity is used, then it is heated and stripped, which releases the gas at a higher pressure. The CO2 is injected into basalt, where cations dissolve out of the rock grains, react with the gas and make carbonate. A grain shrinks at a rate set by temperature, so fine grains in a warm reservoir convert fastest.

Equations

• Capture per pass 1 − exp(−NTU); CO₂ in air 420 ppm, 1.2 kg/m³ air density.
• Langmuir loading q = qmax K p / (1 + K p), with K(T) = K0 exp[(ΔH/R)(1/T − 1/298)]; working capacity q(air) − q(strip).
• Heat per tonne: sensible cp ΔT / (qw M) plus desorption ΔH / M; least work R T ln(1/x).
• Grain conversion X = 1 − (1 − t/τ)³, τ by Arrhenius with E_a = 60 kJ/mol.
• Carbonate CO2 + CaO → CaCO3, 44.009 to 100.087 g/mol.

Checks run in the page

• The contactor transfer-unit integral.
• Langmuir kinetics run to rest against the isotherm.
• A shrinking grain against the conversion formula.
• The isothermal compression integral against R T ln(1/x).
• The carbonate mass balance.

Honest simplifications

A single idealised sorbent with made-up isotherm constants, no humidity, no pressure drop beyond a fixed 120 Pa, no heat recovery, one constant grain life, and a flat 25 % storage capacity of the rock. It shows the scale of the energy and the rock needed, not a plant design or a mineral reaction model.

• Press Cooler regeneration and see the heat per tonne fall but the working capacity change too.
• Press Hot, fine basalt to watch the carbonation finish in months instead of years.
• Compare the energy readout with the least possible energy: the gap is the room for better engineering.