Many modern sulfur recovery unit process waste heat recovery exchangers operate in high-temperature environments. These exchangers are associated with the thermal reactor system where the tube-sheet–tube-ferrule assemblies are exposed to gasses at temperatures approaching 3000°F. Because sulfur compounds are present in the process gas, the carbon steel tube sheet and tubes in the assembly will be deteriorated by sulfidation as the operating metal temperature rises above 600°F. Ferrule systems are used to protect the carbon steel from exposure to excessive temperatures. The temperature distribution in the steel tube-sheet–tube-ferrule system is affected by process gas flow and heat transfer through the assembly. Rather than depend on “assumed” heat transfer coefficients and fluid flow distribution, a computational fluid dynamics investigation was conducted to study the flow fields and heat transfer in the tube-sheet assembly. It was found that the configuration of the ferrule installation has a large influence on the temperature distribution in the steel materials and, therefore, the possible sulfidation of the carbon steel parts.

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