GPSA Ch. 22 API Pub. 955 EPA 40 CFR 60

Calculation Mode:

Design Rate

Design: Size SCOT unit from Claus tail gas conditions

Claus Unit Parameters

Claus Catalytic Stages

Claus Sulfur Recovery

Acid Gas H₂S Content

mol%

Acid Gas Flow Rate

MMscfd

Tail Gas Composition

Tail Gas Flow

MMscfd

Enter 0 for auto-calculation from Claus parameters

H₂S in Tail Gas

mol%

SO₂ in Tail Gas

mol%

COS in Tail Gas

mol%

CS₂ in Tail Gas

mol%

Hydrogenation Reactor

Catalyst Type

Gas Hourly Space Velocity (GHSV)

hr¹

Reactor Inlet Temperature

°F

Amine Absorber

Amine Type

Amine Concentration

wt%

Lean Amine Loading

mol/mol

Number of Trays

SO₂ Emissions Limit

ppmv

Typical Claus Recovery by Stages

Configuration	Recovery (%)
2-stage Claus	94–96
3-stage Claus	96–98
2-stage + SCOT	99.8–99.9
3-stage + SCOT	99.9+

Engineering Basis

Overall Sulfur Recovery:

R_overall = R_Claus + (1 − R_Claus) × R_SCOT

Where R_Claus = Claus unit recovery (fraction), R_SCOT = SCOT unit recovery (fraction)

Hydrogenation Reactions:

SO₂ + 3H₂ → H₂S + 2H₂O

COS + H₂O → H₂S + CO₂

CS₂ + 2H₂O → 2H₂S + CO₂

SCOT Process: All sulfur species in Claus tail gas are hydrogenated/hydrolyzed to H₂S over a CoMo or Titania catalyst, then absorbed in a selective amine unit for recycle to the Claus burner.

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Results

Overall Sulfur Recovery

SO₂ Emissions (ppmv) -

SO₂ Emissions (lb/hr) -

Target Recovery -

Meets Target -

Hydrogenation Reactor

Catalyst Type -

Catalyst Volume (ft³) -

Catalyst Weight (lb) -

Inlet Temp (°F) -

Outlet Temp (°F) -

H₂ Required (SCF/hr) -

Amine Absorber

Amine Type -

Circulation (GPM) -

Lean Loading (mol/mol) -

Rich Loading (mol/mol) -

Absorber Diameter (ft) -

Absorber Height (ft) -

H₂S Absorbed (lb/hr) -

Design Guidelines

Reactor Temperature: Must exceed 500°F for CoMo catalyst activation. Titania catalysts may operate at lower temperatures but have shorter service life.

Amine Selection: MDEA is preferred for selective H₂S removal, leaving CO₂ in treated gas. DEA and DGA co-absorb CO₂, increasing regeneration energy.

Emissions: SO₂ emissions from SCOT units typically 10–250 ppmv after incineration. EPA 40 CFR 60, Subpart Ja limits apply to sulfur recovery units.

SCOT Process Calculator

Claus Unit Parameters

Tail Gas Composition

Hydrogenation Reactor

Amine Absorber

Typical Claus Recovery by Stages

Engineering Basis

📚 Learn the Theory

Results

Hydrogenation Reactor

Amine Absorber

Design Guidelines

Related Calculators

Claus Process

Amine Treatment

Combustion & Flammability

Relief Valve Sizing