The appropriate equilibrium temperature for ammonia synthesis (presenting personal views on different processes)
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There are many synthesis processes in our country, and the synthesis pressures vary as well. For different processes and at various stages of catalyst use, there is an optimal operating temperature. Meanwhile, for ammonia synthesis, by how much does each 1% increase in net ammonia raise the temperature of the syngas? 》I remember an old Italian telling me it was around 13.3 degrees, but I’m not sure now; I hope everyone will discuss these issues more.
Depending on the composition of the syngas in various synthesis processes, an increase of 1% in the net ammonia content generally results in an increase in the temperature difference between the inlet and outlet by 14.5–15°C; currently, factories typically use 15°C as the value for this calculation.
I’m not sure exactly whether the figure you mentioned is accurate, but we can estimate it by taking into account the unit’s analysis report and the net ammonia amount. Of course, the main difference here is that the process pressures vary, and the components differ as well; consequently, the specific heat values also differ. For high-pressure synthesis, the one-way conversion rate should be relatively high, and the requirements regarding inert gases are not very strict; is that why the temperature increase is different?
The ammonia synthesis reaction is a reversible exothermic reaction, and industrial production can only take place with the aid of a catalyst. Temperature affects both the reaction rate and equilibrium; as the temperature rises, the reaction rate increases, but the equilibrium ammonia concentration decreases. Moreover, a catalyst can exhibit its catalytic activity only within a certain temperature range. The active temperature of catalysts used in industry is generally in the range of 360 to 550 degrees. Every 1% increase in ammonia concentration raises the syngas temperature by about fifteen degrees. Although this figure is not entirely precise, it can still be used to roughly assess the operation of the device. Due to differences in pressure and gas composition, the value of adiabatic specific entropy varies slightly.
For every 1% increase in the net ammonia content in the circulating gas, the heat released is sufficient to raise the gas temperature by about 15 degrees.