Claus Sulfur Recovery Unit (SRU) Thermal Stage & Tail Gas Reactor Screener

Achieving a high adiabatic flame temperature ($T_{\text{flame}}$) inside the thermal reactor is critical to destroying trace feed contaminants: * **$\text{BTX}$ Destruction:** Aromatic hydrocarbons (benzene, toluene, xylene) require $T_{\text{flame}} \ge 1050^\circ\text{C}$ to avoid catalyst coking and black sulfur discoloration. * **Ammonia ($\text{NH}_3$) Destruction:** Ammonia requires $T_{\text{flame}} \ge 1250^\circ\text{C}$ to prevent ammonium bisulfite/chloride deposition and downstream condenser plugging. For lean acid gas feeds ($< 40\%\ \text{H}_2\text{S}$), combustion air preheating, fuel gas co-firing, or oxygen enrichment ($28\%\text{--}45\%\ \text{O}_2$) is mandatory to sustain adequate flame temperatures.

Following the thermal stage, process gas passes through 2 or 3 catalytic reactors packed with activated alumina or titania catalysts: * **Thermal Stage:** $65\text{--}72\%$ recovery * **+ Bed 1 ($280\text{--}320^\circ\text{C}$):** $88\text{--}92\%$ cumulative recovery * **+ Bed 2 ($220\text{--}240^\circ\text{C}$):** $95\text{--}97\%$ cumulative recovery * **+ Bed 3 ($200\text{--}210^\circ\text{C}$):** $97\text{--}98.5\%$ cumulative recovery Because EPA NSPS Subpart Ja and international clean air regulations mandate **$\ge 99.8\%$ overall sulfur recovery**, Claus alone is insufficient; a **Tail Gas Treating Unit (TGTU)** (catalytic hydrogenation followed by selective MDEA amine absorption) is **mandatory**.