Sulfuric acid, with equilibrium found rather than assumed

SO₂ in excess air oxidized to SO₃ over a vanadium-pentoxide catalyst, solved by Gibbs free-energy minimization, then absorbed to acid.

Gibbs free-energy minimization — the Aspen RGibbs equivalent•Equilibrium from first principles, no conversion typed in•The exotherm/conversion trade the real converter is staged around

Roaster gas (SO₂ + air)

V₂O₅ converter

Absorption tower

Sulfuric acid

Tail gas

The actual dark-mode canvas: roaster gas oxidized over a vanadium-pentoxide catalyst to sulfur trioxide, then absorbed to make acid with the tail gas vented.

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Equilibrium found, not assumed

The converter is solved by minimizing Gibbs free energy over the species present, so the SO₂/SO₃ split comes from thermodynamics rather than a typed-in conversion. That matters because the reaction is exothermic and equilibrium-limited: the bed heats itself out of conversion, which is precisely why real converters are staged with interstage cooling.

2\,\mathrm{SO_2} + \mathrm{O_2} \rightleftharpoons 2\,\mathrm{SO_3} \quad (\Delta H < 0)

\min \sum_i n_i\!\left(\mu_i^\circ + RT\ln \frac{n_i}{\sum_j n_j}\right) \quad \text{(Gibbs minimization — no extent assumed)}

\text{exothermic} \Rightarrow \text{conversion falls as the bed heats — hence interstage cooling}

Unit ops shipped for this vertical

Gibbs reactor

Composition from free-energy minimization — no conversion or extent typed in.

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Separator

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

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Live plant integration

Stream converter bed inlet and outlet temperatures and the tail-gas SO₂ analyser from the plant's OPC-UA server into this flowsheet's twin comparison — catalyst ageing shows as an equilibrium approach the solved Gibbs minimum makes measurable.

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