What is the Strategies to Prevent Catalyst Sulfur Poisoning?
Strategies to Prevent Poisoning:
In the steam reforming feed, the permissible limits for sulfur and chlorine content are as follows: sulfur content should not exceed 0.5 ppm, and chlorine content should not exceed 0.3 ppm. To prevent chlorine poisoning, it is crucial to ensure clean feedstock and maintain steam quality. The chlorine content in the steam introduced into the conversion process should always be below 0.1 ppm.
Mechanism and Countermeasures for Sulfur Poisoning in Steam Reforming Catalysts:
After sulfur poisoning in steam reforming catalysts, partial activity can be gradually restored by using clean raw materials and optimizing operational conditions. However, this process is slow, making steam regeneration the most effective method for sulfur poisoning recovery. In practical operations, the regeneration of sulfur-poisoned catalysts in conversion reactors is incomplete, indicating that sulfur poisoning is partially reversible.
Mechanism of Sulfur Poisoning in Steam Reforming Catalysts:
3Ni+2H2S→Ni3S2+2H2
Mechanism of Steam Regeneration in Steam Reforming Catalysts:
Ni-S+→NiO+
H2S+H2O→SO2+H2
Ni+H2O→NiO+H2
Sulfur poisoning insteam reforming catalysts is generally considered irreversible below 700°C but reversible above 700°C. To meet this condition, regeneration of steam reforming catalysts is possible after sulfur poisoning. From a reaction equilibrium perspective, the presence of hydrogen gas impedes sulfur removal. Therefore, it is advisable to perform sulfur poisoning regeneration of steam reforming catalysts under complete gas atmosphere. It is crucial to ensure that the temperature during catalyst reduction after sulfur poisoning reaches the corresponding temperature during steam desulfurization and preferably exceeds the corresponding temperature. This ensures excellent reducibility of steam reforming catalysts.
End Indicator: Regeneration concludes when H2S outlet decreases and stabilizes at a minimum value.
Operating Parameters for Steam Regeneration of Sulfur-Poisoned Steam Reforming Catalysts:
System Pressure: Approximately 1 MPa
Outlet Temperature: 800±20°C
Steam Quantity: 40% of normal production
Circulating Medium: N2, steam
Regeneration Time: 8~12 hours
