Biomass is gasified with limited O₂ and steam into syngas (CO + H₂). The water-gas-shift reaction sets the H₂:CO ratio via a real equilibrium correlation:
CO + H2O ⇌ CO2 + H2
ln K_wgs = 4577.8 / T(K) − 4.33 (Moe correlation)
K = (H2·CO2) / (CO·H2O) → solved for shift extent x
The syngas then feeds a Fischer-Tropsch reactor, where CO and H₂ polymerize on a catalyst surface one carbon at a time. Each growing chain either adds another CH₂ unit (probability α, the chain-growth probability) or terminates (probability 1−α). That is a geometric process, giving the Anderson-Schulz-Flory (ASF) distribution:
Mole fraction: Xn = (1 − α)·α^(n−1)
Mass fraction: Wn = n·(1 − α)²·α^(n−1)
Mean chain length: n̄ = 1 / (1 − α)
- Gasifier temperature / steam ratio — shift the water-gas equilibrium and change the H₂:CO ratio feeding the FT reactor.
- FT bed temperature — lower temperatures (Co catalyst, ~220 °C) favour a high α and long waxy chains; higher temperatures (Fe catalyst, ~340 °C) favour a low α and short, olefin-rich chains.
- Feed rate — scales how fast new syngas bubbles and product chains are generated.
- Each dot in the product column is one ASF-sampled hydrocarbon chain, settling into the gas/gasoline/diesel/wax band that its carbon number belongs to — exactly the layered product slate a real biomass-to-liquid (BtL) plant separates by distillation.
- This 2D cutaway shows the exact same water-gas-shift and Anderson-Schulz-Flory chemistry as the 3D version, viewed as a side cross-section. Drag the canvas to pan and scroll to zoom.