MaximaLabs

Sour water stripping, with the speciation that explains it

Ammonia and hydrogen sulfide steam-stripped on a weak-electrolyte package where each suppresses the other's volatility and heat reverses both.

Weak-electrolyte sour-water package — speciation, not a fitted KNH₃ and H₂S genuinely suppress each other's volatilityAmmonia is what sets the steam rate — and the model shows why
Sour water (NH₃ + H₂S)
Stripping steam
Sour water stripper
Sour gas to SRU
Stripped water

The actual dark-mode canvas: sour water counter-currently contacted with live steam over ten equilibrium stages, sending ammonia and hydrogen sulfide overhead as sour gas and returning stripped water fit for reuse.

Why the two removals come out asymmetric

Ammonia raises pH and holds sulfide down as HS⁻; H₂S lowers pH and holds ammonia down as NH₄⁺ — each suppresses the other, and heat reverses both, which is precisely why a stripper works. H₂S strips essentially completely while ammonia, orders of magnitude more soluble, is the duty that sets the steam rate. Scope note: this is the NH₃/H₂S system — real sour water often also carries CO₂, which competes for the ammonia and is out of scope for this package.

NH3+H2ONH4++OH,H2SH++HS\mathrm{NH_3} + \mathrm{H_2O} \rightleftharpoons \mathrm{NH_4^+} + \mathrm{OH^-}, \qquad \mathrm{H_2S} \rightleftharpoons \mathrm{H^+} + \mathrm{HS^-}
Kieff=Kiphyscimolecularcitotal(only the un-ionised fraction is strippable)K_i^{\,\text{eff}} = K_i^{\,\text{phys}}\cdot\frac{c_i^{\,\text{molecular}}}{c_i^{\,\text{total}}} \quad \text{(only the un-ionised fraction is strippable)}
coupling: NH3pHHSKH2Seff(and heat reverses both)\text{coupling: } \mathrm{NH_3}\uparrow \Rightarrow \mathrm{pH}\uparrow \Rightarrow \mathrm{HS^-}\uparrow \Rightarrow K_{\mathrm{H_2S}}^{\,\text{eff}}\downarrow \quad \text{(and heat reverses both)}

Unit ops shipped for this vertical

Absorber (Kremser shortcut)

A specified equilibrium-stage count absorbing or stripping between two contacted streams.

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Live plant integration

Stream stripper overhead H₂S and ammonia analysers plus the steam rate from the plant's OPC-UA server into this flowsheet's twin comparison — a stripped-water spec creeping up is visible against the solved speciation before the biotreater sees it.

See the Digital Twin platform →

Try it yourself

  • Weak-electrolyte sour-water package — real speciation, not a fitted K
  • Only the un-ionised fraction is strippable, and the model shows it
  • Ammonia solubility is what sets the steam rate

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