Pre-sulfiding of hydrogenation catalysts
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Catalysts in hydrogenation units need to be presulfurized before operation, but this process leads to very high H2S levels in the equipment and pipelines. Since the temperature of the equipment used for presulfurization does not reach the temperature required for normal operation of such equipment and pipelines, it is possible that devices which are not subject to wet H2S corrosion under normal operating conditions end up in an environment prone to wet H2S corrosion during presulfurization. Moreover, since the presulfurization procedure only specifies the temperature for the catalysts and not those of other equipment, it is difficult to determine which devices are exposed to wet H2S corrosion. (According to the appendix of SH3075, in a wet H2S corrosion environment the temperature must not exceed 150°C; if the temperature exceeds 150°C, wet H2S corrosion need not be considered.) The main issue is the lack of information regarding temperatures. So what should I do to address this problem? How can I determine which devices are in a wet H2S corrosion environment during the sulfurization process?
You can check the temperature; the pre-vulcanization temperature is generally around 210–320 degrees. The temperature before reaction air cooling is usually above 150°C. In equipment subject to wet hydrogen sulfide corrosion, reaction air cooling and cold high-pressure treatment are employed
Our company’s vulcanization process also goes through many devices such as hydrogen sulfide stripping towers and distillation towers
During the presulfiding process, water is present and dissolves hydrogen sulfide, creating an acidic environment free of ammonia; corrosion and cracking occur in welds with a hardness above 200 in many factories (as no carbon sulfide protective layer is formed on the surface of the metal in new installations). In particular, the high-pressure air-cooling design requires stress relief, but manufacturers generally fail to carry this out, resulting in plant shutdowns for repairs; there are also numerous cases of cracks in other pipelines, valves, bolts, hydrogen compressors, and instrument pipelines. The design institute and catalyst suppliers have no specific measures for this. It is a new area of concern regarding corrosion.
Technical modifications can be used to increase the flow of hot light fractions into the crude oil pipeline
First of all, there is no need to worry about corrosion in the reaction system, as its materials are resistant to sulfur. There’s no need to worry about the hydrogen sulfide stripping tower; its material is also sulfur-resistant. The main concern is corrosion at the top of the distillation tower; we have modified the top of the distillation tower here by injecting a slow-release agent during sulfidation as a precaution. Actually, the distillation tower should be fine as well; corrosion margin should be built into its design.