Conditions for the ammonia synthesis reaction
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At what pressure does the ammonia synthesis reaction system in the Kellogg process stop? Our plant has been shut down; in order to save time on startup, we are not performing any purging of the synthesis tower, but instead plan to reduce the pressure to a certain level to bring the reaction to an end. I would like to ask everyone: at what pressure level does the reaction stop automatically?
The question posed by the original poster isn’t quite accurate; in fact, it’s possible to park the vehicle without reducing the pressure at all. Of course, for safety reasons, the system pressure is usually reduced to 8 MPa.
In fact, in the synthesis reaction, our unit is designed to allow the reaction to take place at 150 kilograms and 200°; it’s just that high pressure and low temperature facilitate the shift in chemical equilibrium. Of course, in case of a shutdown during production, to save time on starting up and shutting down, it is possible to maintain the temperature and pressure temporarily.
In fact, the ammonia synthesis reaction can take place only under certain conditions: for instance, when the catalyst is in an active state, the reaction occurs at temperatures between 280 and 300 degrees. The higher the pressure, the more intense the reaction; below a certain pressure, no reaction occurs even at active temperatures. This characteristic can be utilized to control the rate of temperature increase during startup. Whether it is a short-term or long-term shutdown, there is always an issue of temperature redistribution during startup. Therefore, there is no need to avoid reducing pressure in order to shorten the startup time, as suggested by the original poster.
If you just want it to not react, increase the cold shock value; when the temperature is below the catalyst’s active temperature, no reaction occurs, and there is no need to apply pressure during operation. However, high pressure can lead to leaks, and the pressure must be higher than that of the boiler water, though this also depends on the pressure retention capability of your synthesis system
Increasing the cooling line flow can lower the bed temperature, thereby suppressing the reaction!