MaximaLabs

Nitric acid, run deliberately away from equilibrium

Ammonia burned over a platinum-rhodium gauze to nitric oxide, oxidized onward to NO₂, then absorbed in water as acid.

Three stages, three genuinely different regimesThe burner is kinetically selective — thermodynamics favours N₂Absorption closing the balance to acid liquor
Air
Ammonia
Mix
Pt-Rh burner
Cooler
NO oxidizer
Absorption tower
Nitric acid
Tail gas

The actual dark-mode canvas: ammonia burned in air over a platinum-rhodium gauze to nitric oxide, cooled and oxidized onward to NO₂, then absorbed in water as nitric acid with the tail gas vented.

A reaction run deliberately away from equilibrium

Thermodynamics favours burning ammonia to nitrogen; the platinum gauze exists to win the kinetic race to NO instead, on a millisecond contact time. Treating that stage as an equilibrium reactor would predict the wrong product entirely — which is why the three stages are modelled as three different regimes rather than one convenient one.

4NH3+5O24NO+6H2O(kinetically selective, not equilibrium)4\,\mathrm{NH_3} + 5\,\mathrm{O_2} \longrightarrow 4\,\mathrm{NO} + 6\,\mathrm{H_2O} \quad \text{(kinetically selective, not equilibrium)}
2NO+O22NO2(rare third-order gas-phase step, favoured by cold)2\,\mathrm{NO} + \mathrm{O_2} \longrightarrow 2\,\mathrm{NO_2} \quad \text{(rare third-order gas-phase step, favoured by cold)}
3NO2+H2O2HNO3+NO(absorption, recycling NO internally)3\,\mathrm{NO_2} + \mathrm{H_2O} \longrightarrow 2\,\mathrm{HNO_3} + \mathrm{NO} \quad \text{(absorption, recycling NO internally)}

Unit ops shipped for this vertical

Mixer

Combines multiple streams into one, closing the mass and energy balance.

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Fixed-conversion reactor

A specified per-pass conversion on a key component — the shortcut counterpart to the equilibrium and kinetic reactors.

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Heater / cooler

Duty- or outlet-condition-specified energy-balance stage.

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Separator

Flash/phase-split unit op — the foundational vapor-liquid calculation.

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Live plant integration

Stream burner gauze temperature, oxidizer outlet and absorber acid strength from the plant's OPC-UA server into this flowsheet's twin comparison — gauze selectivity decays over a campaign, and the loss appears as a gap from the solved NO yield.

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Try it yourself

  • Three stages in three genuinely different regimes
  • The burner is kinetically selective — equilibrium favours N₂
  • Absorption closing the balance to real acid liquor

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