How to protect catalysts when the system is shut down

This post was last edited by 654262293 on 2010-9-2 at 13:56. For short-term parking, nitrogen filling for protection is sufficient, along with a slight positive pressure. If it is no longer needed or if the catalyst needs to be removed, the synthetic ammonia catalysts, including those for low-temperature conversion, high-temperature conversion, transformation, and methanation, must be oxidized. Oxygen is added to the steam for slow oxidation; ultimately, no temperature rise should occur. The desulfurization catalyst can be removed directly.

Reply 1# Chemical gas purification: Fill with nitrogen to maintain positive pressure

This post was last edited by 654262293 on 2010-9-2 at 13:56. For short-term parking and when there are no maintenance tasks required, the system can maintain its pressure; if the parking period is longer, the system pressure can be released and nitrogen can be used to keep the system at a slight positive pressure.

This post was last edited by 654262293 on 2010-9-2 at 13:56. Nitrogen should be used to maintain positive pressure; air must not get in.

The last edit to this post was made by 654262293 on 2010-9-2 at 13:57. What was said on floor 4 is correct: for short-term parking, and when there are no maintenance tasks required for the system, it is possible to maintain pressure in the system. If the parking period is longer, the system pressure can be released, and nitrogen can be used to keep the system at a slight positive pressure.

For short-term parking, nitrogen filling is used for protection; for long-term parking, the inlet and outlet of the tower must be sealed with blind flanges before nitrogen filling is applied for protection. In the case of long-term parking where the catalyst is no longer in use, cooling and passivation measures must be taken.

Thank you all for your support and assistance.

(1) During parking and operation, air and water should be prevented from entering the catalyst bed to avoid the condensation of water vapor in the bed. (2) After the low-temperature converter is shut down and depressurized, it should be purged and cooled using dry gas or nitrogen. A blind flange should be used to isolate the low-temperature converter from the system, and an inert gas should be used to maintain a slight positive pressure inside the converter (100–200 Pa). The inert gas used for pressure holding must be dry, with an oxygen content of less than 0.5%. (3) When performing hot work in a low-temperature converter, the catalyst bed temperature should be reduced to 200°C, after which it should be displaced with superheated steam. Immediately after the hot work, it is replaced with dry gas, and a slight positive pressure is maintained inside the low-temperature converter throughout the process. (4) When starting up after shutdown, the temperatures of the pipes and equipment are low; the gas in the cold pipes (equipment) causes water vapor to condense, thereby introducing water into the lower conversion furnace bed. To address this, an electric heater can be turned on to raise the temperature using dry gas, and venting should be carried out at the inlet of the lower conversion furnace. Operation can be resumed once the temperature reaches normal levels (at least above the dew point temperature).

Blind flanges are installed at the inlet and outlet, connected to a U-tube manometer, and a slight positive pressure is maintained using high-purity nitrogen.

This post was last edited by Chemical Gas Purification on 2010-9-7 at 14:05: Positive slight pressure protection during nitrogen filling when the synthesis tower is shut down!