Synthetic catalyst passivation treatment

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Deactivation schemes for medium and low pressure methanol synthesis catalysts I. Conditions and preparatory work required for oxygenation deactivation 1. Conduct a thorough inspection of the equipment, instruments, valves, and sampling points in the synthesis system. 2. Analyze nitrogen, air, and condensate to ensure they are of qualified standard for use. 3. The circulation pump is in good condition and ready for use. 4. Analytical sampling tools and instruments are in good condition and ready for use. 5. Fill the synthetic bubble level to a minimum of 200–300 mm, and vent it using a safety valve. 6. Have steam ready for fire suppression on site. II. Passivation method: Start the two-in-one unit, control the pressure in the synthesis system at 0.3–0.4 MPa; use a steam injector to keep the outlet temperature at ≤70°C. The acceptable level is when the CO + H2 concentration at the tower outlet is ≤0.3%. The system gas should be circulated, and when air is added, the initial oxygen content in the gas entering the tower should be controlled at ≤0.2%. Samples should be taken at the tower inlet for analysis, and the oxygen concentration in the gas entering the tower should be increased gradually until it reaches 20% at the outlet, with the outlet temperature remaining at ≤60°C – at this point, passivation is complete. III. Specific passivation steps. 1. Purge the system with N2; the result is considered satisfactory if the CO + H2 level at the tower outlet is ≤0.3%. 2. After the system replacement is completed successfully, start the compressor to control the speed of the turbine, maintaining the pressure in the synthesis system at 0.3–0.4 MPa. Slightly open the drain valves of the gas-gas heat exchanger as well as those of the water cooler. Pay close attention to the liquid level in the methanol separator to prevent damage to the compressor due to the presence of liquid. 3. Compare the synthesized bubble level with the on-site value to ensure there are no errors; use a steam injector to raise the temperature of the synthesis process, controlling the rate of temperature increase at 20–30°C, with the exit temperature of the synthesis tower kept at 70°C. 4. The inlet and outlet stop valves of the water cooler’s circulating water are opened to control the flow rate. 5. Slightly open the DN15 ball valve to introduce air into the system, while monitoring changes in tower temperature. Oxygen is started to be introduced, and samples are taken at the tower inlet for analysis every 30 minutes. The initial oxygen concentration is ≤0.2%; while keeping the temperature rise at no more than 25°C, the oxygen content is gradually increased until the oxygen concentrations at the inlet and outlet reach 20%. After that, the passivation process continues for another 5 hours, after which it is completed. Catalyst deactivation schedule: Exit temperature ≤70 ≤70 ≤70 ≤70 ≤70 ≤70; O2% at the inlet to the tower ≤0.2, 1, 2, 5, 10, 21; Required time in hours: 3, 7, 7, 10, 5, 3. The deactivation time can be adjusted accordingly depending on the specific circumstances. IV. Precautions 1. The CO+H2 level at the tower outlet should be ≤0.3%; oxygen supply to the system is permitted only after this condition is met. 2. For oxygen-based passivation, great care must be taken; a dedicated person should be responsible for carrying out the process strictly in accordance with the passivation protocol, to prevent the catalyst from sintering due to too rapid passivation. 3. If the temperature rises suddenly during oxygen supply, the air inlet valve should be closed immediately, and operations should resume only after the temperature returns to normal. 4. The system pressure must be lower than the air pressure. 5. The bubble pressure can be released through a safety valve; if the trend of increase in bubble pressure accelerates and the temperature at the tower outlet rises significantly, oxygen supply should be reduced, the water flow rate increased to lower the temperature, and oxygen supply should be adjusted again once the temperature stabilizes. 6. If it stops operating due to a two-in-one failure, oxygen supply should be stopped immediately, the area behind the tower should be vented, and it should be purged with nitrogen. 7. When starting oxygen supply, due to the high activity of the catalyst, a strong reaction occurs upon contact with oxygen; therefore, the initial oxygen concentration and the rate of oxygen supply must be strictly controlled. 8. Throughout the entire passivation process, the gas released during venting must not be discharged into the flare main pipe; it is necessary to close the isolation valves before and after PIC40024 and PIC40008, and use the on-site vent valve for venting, in order to prevent hazardous gases from entering the venting pipeline and causing an explosion. V. Analysis 1. Before oxygen addition, analyze CO+H2 ≤ 0.3%. 2. During oxygen-passivated treatment, analyze the oxygen content at the inlet every half hour. 3. By increasing the oxygen content, the temperature at the outlet of the synthesis tower no longer rises; the oxygen content in the gas exiting the synthesis tower is analyzed once per hour. 4. Special circumstances will be notified separately.