Even in piping with properly-designed insulation and tracing systems, certain combinations of tail gas streams can lead to severe corrosion and fouling. One such pitfall is when hot sulfur-laden gases from sulfur pits, liquid sulfur degassing units, and other sources are mixed with large volumes of cooler gas such as from the absorbers in the tail gas treating units. This combination leads to condensation of sulfur, water and/or sulfuric acid, which can quickly result in corrosion and equipment damage. A second pitfall resulted from the recent trend of sizing-up to extremely large units - tail gas lines are sometimes as large as NPS 84 diameter! Like past designs, these units used steam-traced piping up to the last elbow which entered the incinerator, and then this elbow was internally refractory-lined. Because of the sizable diameters of the pipes, the elbows are very large resulting in the refractory-lining extends much further from the incinerator. This leads to the gases getting cool enough for condensation and acid attack on the piping and equipment. Other lessons learned affecting corrosion and fouling involve the piping layout and the incinerator inlet nozzle positions. Avoiding corrosion is even more critical in today's ultra-large units as the economic impacts of process losses and maintenance costs are also amplified. This paper discusses the pitfalls that can lead to corrosion and fouling in the SRU tail gas lines and the lessons learned on how these pitfalls can be mitigated.
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