Application Characteristics of High-Pressure Reactors for Nickel and Nickel-Based Alloys (Part 1)

　　High-pressure reactors made of nickel and nickel alloys exhibit superior corrosion resistance to strong acids, strong bases, and other highly corrosive media compared to those made of stainless steel and other non-ferrous metals. They also operate at higher temperatures, making them one of the most important types of high-pressure reactors currently available.

　　When using high-pressure reactors made of nickel materials and nickel-based alloys, attention should be paid to the following issues regarding their allowable temperatures:

　　1. When the reactor vessel is made of a nickel alloy whose primary alloying elements are chromium or molybdenum, and the service conditions of the vessel’s process medium could potentially induce intergranular corrosion in these nickel alloys, the upper limit of the equipment’s allowable operating temperature should not exceed the lower limit of the long-term aging temperature that sensitizes these nickel alloys to increased intergranular corrosion susceptibility (e.g., exceeding 104 hours)—a sensitization temperature distinct from the typical short-term sensitization temperature observed over just a few hours. This lower limit of the long-term aging sensitization temperature generally ranges from 300 to 400 degrees Celsius.

　　2. The service temperature of nickel materials and nickel-based alloys in sulfur-containing media should be limited. In oxidizing sulfur-containing atmospheres (such as those containing sulfur dioxide), the service temperature of pure nickel and nickel-copper alloys should not exceed 315°C, while that of nickel-chromium-iron alloys and nickel-iron-chromium alloys should not exceed 815°C. In reducing sulfur-containing environments, the service temperature of pure nickel and nickel-copper alloys should not exceed 260°C, and that of nickel-chromium-iron and iron-chromium alloys should not exceed 540°C.