Super-Claus process

In the second section, unconverted hydrogen sulfide reacts with the produced sulfur dioxide over a bauxite catalyst in the Claus reactor. Normally more than one reactor is available. In the Super-Claus process (Figure 4-3), three reactors are used. The last reactor contains a selective oxidation catalyst of high efficiency. The reaction is slightly exothermic ... 

Figure 4-3. The Super Claus process for producing sulfur (1) main burner, (2,4, 6,8) condensers, (3,5) Claus reactors, (7) reactor with selective oxidation catalyst.

The combustion reaction is realized in the firebox of the waste heat boiler within the Claus unit, while the Claus reaction and hydrolysis reactions take place in the Claus reactor filled with a catalyst. This process requires two or three Claus reactors. The sulfur recovery is 90%-96% in the first two reactors and is 95%-98% in the third reactors. Recently, super-Claus process has emerged. In the super-Claus process, the sulfur recovery can reach up to 99% and 99.5%, respectively, after adding a selective oxidation step or a hydrogenation reactor followed by a selective oxidation reactor on the basis of Claus. For the purpose of meeting the atmospheric emission standard, acidic gas in the outlet of reactor should be combusted at 1,200°C to transform the remaining H2S into SO2. 

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