Practical Exercise on Purification Technology Version [053]
Thread Content
Why is steam added during the reduction of medium-temperature catalysts? How much is appropriate to add? Because using dry gas for reduction causes the medium-temperature catalyst to be over-reduced. The reduced catalyst (Fe3O4) is over-reduced to form ferrous oxide and metallic iron, as well as iron carbide, which causes changes in the catalyst’s structure, leading to deactivation, pulverization, and increased resistance. The most effective way to prevent excessive reduction is to introduce a certain amount of water vapor from the beginning of the reduction process. Generally not less than 10%. As the transformation reaction increases, the proportion of water vapor can increase accordingly.
The purpose is to prevent excessive reduction of the catalyst; generally, 10% is added
Because using dry gas for reduction causes the medium-temperature catalyst to be over-reduced. The reduced catalyst (Fe3O4) is over-reduced to form ferrous oxide and metallic iron, as well as iron carbide, which causes changes in the catalyst’s structure, leading to deactivation, pulverization, and increased resistance. The most effective way to prevent excessive reduction is to introduce a certain amount of water vapor from the beginning of the reduction process. Generally not less than 10%. As the transformation reaction increases, the proportion of water vapor can increase accordingly.
Natural gas first reacts with steam to produce carbon monoxide, hydrogen, and carbon dioxide； It then enters the medium-pressure reactor, where carbon monoxide reacts with water vapor to produce hydrogen and carbon dioxide ； This can increase hydrogen production ； Subsequent decarburization can then yield hydrogen ； Nitrogen can be obtained through air separation ； Then hydrogen and nitrogen can react to produce ammonia.
Because using dry gas for reduction causes the medium-temperature catalyst to be over-reduced. The reduced catalyst (Fe3O4) is over-reduced to form ferrous oxide and metallic iron, as well as iron carbide, which causes changes in the catalyst’s structure, leading to deactivation, pulverization, and increased resistance. The most effective way to prevent excessive reduction is to introduce a certain amount of water vapor from the beginning of the reduction process. Generally not less than 10%. As the transformation reaction increases, the proportion of water vapor can increase accordingly.
If it is in a sulfided state, air and water vapor must be added during regeneration; without water vapor, it will directly oxidize to iron oxide.
Because the medium-temperature catalyst exists in the form of Fe2O3 during transportation and storage, whereas the main active component for converting CO in our production process is Fe3O4. To convert Fe2O3 into Fe3O4 with transformation activity, it must be reduced before use. Since the catalyst contains a small amount of moisture during manufacturing, transportation, and storage, the moisture is evaporated by raising the temperature before use. During the reduction process, the reduction reaction can occur only at a temperature of 180°C; above 250°C, the reaction becomes more pronounced and intense. Therefore, the medium-temperature catalyst needs to be heated and reduced before use.
During the temperature-raising reduction of medium-temperature catalysts, maintaining a constant temperature of 120°C is intended to evaporate all the moisture inside the catalyst, thereby increasing its durability； Maintaining a constant temperature of 200°C is intended to eliminate the temperature difference between the upper and lower sections, thereby ensuring uniform bed temperature. During the temperature rise of the medium-temperature catalyst, during the steam displacement phase, it is necessary to ensure that the bed temperature is at least 20 degrees higher than the steam temperature
Reduction using dry gas will cause excessive reduction of the medium-temperature catalyst. The reduced catalyst (Fe3O4) is over-reduced to form ferrous oxide and metallic iron, as well as iron carbide, which causes changes in the catalyst’s structure, leading to deactivation, pulverization, and increased resistance. The most effective way to prevent excessive reduction is to introduce a certain amount of water vapor from the beginning of the reduction process. Generally not less than 10%. As the transformation reaction increases, the proportion of water vapor can increase accordingly.
Because using dry gas for reduction causes the medium-temperature catalyst to be over-reduced. The reduced catalyst (Fe3O4) is over-reduced to form ferrous oxide and metallic iron, as well as iron carbide, which causes changes in the catalyst’s structure, leading to deactivation, pulverization, and increased resistance. The most effective way to prevent excessive reduction is to introduce a certain amount of water vapor from the beginning of the reduction process. Generally not less than 10%. As the transformation reaction increases, the proportion of water vapor can increase accordingly.
Because using dry gas for reduction causes the medium-temperature catalyst to be over-reduced. The reduced catalyst (Fe3O4) is over-reduced to form ferrous oxide and metallic iron, as well as iron carbide, which causes changes in the catalyst’s structure, leading to deactivation, pulverization, and increased resistance. The most effective way to prevent excessive reduction is to introduce a certain amount of water vapor from the beginning of the reduction process. Generally not less than 10%. As the transformation reaction increases, the proportion of water vapor can increase accordingly.