Industrial SO3 gas recycle

Outotec s LUREC process uses an SO3 gas recycle step to treat up to 25 volume% SO2 feed gas (Daum, 2009 Storch, 2J009). The LURECT process was first installed in 2007 at the Yanggu Xiangguang copper smelter acid plant which treats high SO2 concentration feed gas produced by a flash smelting and flash converting furnace. 

The acid plant has five catalyst beds arranged in a 3-2 configuration (Section 20.3). A portion of the cooled third catalyst bed exit gas is recycled at 553 K to the inlet of the first catalyst bed. Additirmal design information is provided in Tables 27.1 and 27.2 (Daum, 2009). 

The amount of cool recycle gas to the first catalyst bed inlet can be determined using the calculations shown in Section 27.2. 

2 Comparison between first and third catalyst bed exit gas recycle 

Returning to the example used throughout this chapter, Fig. 27.8 provides a comparison between recycling first catalyst bed exit gas and third catalyst bed exit gas using 13.0% SO2 gas. It shows less recycle is required when using third catalyst bed exit gas. 

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