MODELING REACTION QUENCH TIMES IN THE WASTE HEAT BOILER OF A CLAUS PLANT

At the high temperatures found in the modified Claus reaction furnace, the thermal decomposition and oxidation of H2S yields large quantitie s of desirable products, gaseous hydrogen (H-2) and sulfur (S2). Howev er, as the temperature of the gas stream is lowered in the waste heat boiler (WHB) located downstream of the furnace, the reverse reaction o ccurs leading to reassociation of H2 and S2 molecules. To examine the reaction quenching capabilities of the WHB, a rigorous computer model was developed incorporating recently published intrinsic kinetic data. A sensitivity study performed with the model demonstrated that WHBs h ave a wide range of operation with gas mass flux in the tubes from 4 t o 24 kg/(m2.s). Most important, the model showed that it was possible to operate WHBs such that quench times could be decreased to 40 ms, wh ich is a reduction by 60 % compared to a base case scenario. Furthermo re, hydrogen production could be increased by over 20% simply by recon figuring the WHB tubes.