Size refinery Claus Sulfur Recovery Units (SRU) and thermal reaction furnaces. Calculate stoichiometric combustion air demand, adiabatic flame temperature, thermal stage conversion, waste heat boiler steam generation, and overall sulfur recovery efficiency.
Acid Gas Feed & Burner Parameters
SRU Sizing & Sulfur Yield Outputs
Live Claus Sulfur Recovery Unit (SRU) Process Flow Simulator
Process flow schematic featuring thermal reaction furnace, waste heat boiler steam drum, catalytic converter bed, and liquid sulfur collection pit.
Fatal Traps & Engineering Pitfalls in Claus SRU Design
1. Flame Temperature Dropping Below 1050°C (BTEX Soot Poisoning)
When treating lean acid gas (<45% H2S), adiabatic flame temperature can collapse below 980°C. Heavy aromatics (BTEX) do not thermally combust; instead, they pyrolyze into black graphitic soot. The soot travels into the first Claus converter, coating spherical alumina catalyst in an impervious carbon jacket and destroying recovery within 72 hours.
2. The 2:1 H2S to SO2 Ratio Control Hunting Trap
The catalytic Claus reaction is strictly bound by 2 H2S + SO2 <-> 3 S + 2 H2O. A minor 2% error in combustion air flow upsets this exact 2:1 ratio. Operating with ratio swings drops overall sulfur recovery from 96.5% down to under 88%, massively overloading the downstream Tail Gas Treating Unit (TGTU) and flaring SO2 into violation territory.
3. Waste Heat Boiler Tube Sheet Sulfidation Catastrophe
Gases entering the WHB at 1200°C contain corrosive elemental sulfur and H2S. If ceramic inlet ferrules fail to insulate the carbon steel tubesheet, localized metal temperatures exceed 370°C (700°F). At this temperature, high-temperature sulfur corrosion thins tubesheet welds at up to 10 mm/year, leading to explosive high-pressure boiler tube ruptures.
4. Sub-Dew-Point Sulfur Condensation in Catalytic Beds
While lower catalyst bed temperatures thermodynamically favor the exothermic Claus reaction, operating bed inlet temperatures below the sulfur dew point (~180°C to 210°C) condenses liquid sulfur directly inside catalyst pores. Capillary condensation plugs the active micropores completely, causing instantaneous 90% loss of catalytic activity.
5. Solid Ammonium Salt Plugging in Sour Gas Stripping
If sour water stripper (SWS) gas containing ammonia is co-fed into an acid gas burner without achieving high-intensity mixing (>1300°C core flame), NH3 slips past the furnace. Downstream in the second or third sulfur condenser (<140°C), NH3 reacts with SO2 and moisture to precipitate solid ammonium salts that choke condenser tubes completely.
Thermodynamic Derivations & Sizing Equations
The modified Claus reaction furnace balances stoichiometry, adiabatic combustion enthalpy, and thermal sulfur vapor equilibrium.
O₂_demand = Q_feed · [ (y_H2S / 3) · 1.5 + (y_HC · 2.0) ] [Nm³/h O₂]
Air_demand = O₂_demand / (y_O2_air / 100) [Nm³/h air]
2. Daily Elemental Sulfur Production (M_sulfur):
M_sulfur = Q_feed · (y_H2S / 100) · (32.065 / 22.414) · (η_recovery / 100) · (24 / 1000) [metric tons/day]
3. Reaction Furnace Adiabatic Flame Temperature (T_flame):
ΔH_comb = Q_H2S_comb · 518,000 kJ/kmol + Q_HC · 802,000 kJ/kmol
T_flame = T_inlet + [ ΔH_comb / (Q_total_flue · Cp_flue) ] (typically 1050°C to 1350°C)
4. Waste Heat Boiler HP Steam Generation:
Q_WHB = Q_total_flue · Cp_flue · (T_flame - 315°C)
Steam_rate = Q_WHB / Δh_vap(P_steam) [ton/hour 40 barg steam]
5. Firebox Volume & Diameter:
V_firebox = Q_total_flue_actual · t_residence [m³]
D_furnace = √[ V_firebox / (2.8 · π / 4) ]