Xylene Addition Effects in Thermal Stage of Claus Reactors

Experimental results are presented on the effect of xylene addition to H₂S/O₂ flames at equivalence ratio of 3.0 (Claus Condition) with respect to H₂S and complete combustion of xylene. The results from the combustion of H₂S/xylene mixture is compared with the baseline case of 100% H₂S combustion to isolate the role of xylene addition in the Claus reactor. Combustion of H₂S alone showed a decrease in its mole until it reached to an asymptotic minimum mole fraction value. This resulted in the formation of SO₂ to a maximum mole fraction which subsequently decomposed from the formation of elemental sulfur through its reaction with H₂S. Addition of small amount of xylene (0.5% and 1%) increased the asymptotic minimum value of H₂S as well as the formation of H₂ which provided oxidation competition between the formed H₂ and H₂S. Presence of xylene also triggered the formation of CH₄ and CO which provided pathway on the formation of COS and CS₂. The oxidation of CH₄ and CO by SO₂ and other sulfur radicals reduced the maximum mole fraction of SO₂ but increased the subsequent rate of SO₂ decomposition to increase the formation rate of elemental sulfur. These results show the direct impact of trace amounts of xylene in the feed stream on sulfur formation to reveal direct impact on the Claus reactor performance for sulfur capture.