Synthetic heating reduction
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Why is ammonia introduced during the heating and reduction steps in synthesis?
Water is highly soluble in ammonia; using ammonia helps to reduce the vapor concentration of water entering the tower, lower the freezing point of water, and prevent freezing in the pipes
1. Reduce ice formation and prevent freezing. 2 Reduce the concentration of synthetic incoming water vapor. 3 Can remove CO2 from the recycle gas
I think it’s mainly to lower the freezing point and prevent freezing that could block the pipes
A large amount of water is generated during the reduction process in the synthesis tower, and water is also a poison for ammonia synthesis catalysts; therefore, it is necessary to control the vapor concentration at the inlet of the synthesis tower. The purpose of introducing ammonia is primarily to reduce the vapor concentration at the inlet of the synthesis tower and to separate the water produced as a result of reduction； The second reason is to lower the freezing point and prevent icing from blocking the pipelines, which is the main reason for introducing ammonia.
During the reduction process in the synthesis tower, a large amount of water is generated, and water is toxic to the ammonia synthesis catalyst; therefore, it is necessary to control the vapor concentration at the inlet of the synthesis tower. The key to controlling this vapor concentration is to lower the temperature of the circulating gas, bringing it below zero degrees Celsius. At temperatures below zero degrees Celsius, water freezes and can block equipment and pipelines. By adding ammonia, water is converted into ammonia water, which raises the freezing point. Hence, ammonia must be introduced before heating the synthesis catalyst for reduction and startup.
I believe that ammonia is introduced to lower the ammonia separation temperature, making it easier to separate ammonia in the later stages of reduction and reducing the ammonia content entering the tower.
If the synthesis system consists of multiple units, the method of using air release after the tower in combination with pressure supplementation can be employed as an alternative to filling the system with liquid ammonia, thereby reducing the risks and uncertainties associated with such filling. This approach proves to be effective; I welcome any feedback from experts.
Ammonia is added to prevent the formation of water during temperature rise; due to the high freezing point of water, it tends to crystallize and block the pipes during heat exchange in the ammonia cooling system. By adding ammonia, the water is converted into ammonia water, and when a certain concentration is reached, its freezing point becomes very low, reducing the likelihood of crystallization and thus preventing pipe blockages that could affect the reduction process.