Bypass reheat exchanger

While this type of "indirect reheat" exchanger is a fine way to expedite sulfur plant start-ups, it does very little to improve conversion of H2S/SO2 to liquid sulfur. For the 50-T/D Claus unit, a bypass to direct reheat gas to the first fixed bed reactor was installed. Figure 5-5 illustrates the location of the bypass. 

The partial bypassing of both the reheat exchanger and the first stage condenser reduced the Claus train front-end pressure from 10.2 psi to 9.2 psi. This reduction in front-end pressure expanded capacity by 5%. 

The use of oxygen-enriched air and the partial bypassing of the first stage condenser and reheat exchanger resulted in a combined capacity increase of 24%. However, these two operating parameters were only used during periods of limited sulfur recovery capacity. 

There are several methods of reheating the vapor, including hot gas exchange, in-line burners, hot gas bypass, or indirect steam reheat. Each has advantages and disadvantages generally indirect steam reheat is most expensive but yields higher recoveries. 

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