C F Braun Description of Ammonia Synthesis

CH4 + H20 <——> CO + 3H2

C0 + H20 <——> CO2 + H2

The reforming is furnaced by fuel, and escapes from the top as the flue gas. In the C F Braun process for ammonia production, excess air is introduced in the secondary reformer. The gas stream is sent to an absorber, where a solvent, primarily methyl diethanol amine (MDEA), is used to absorb the CO2 from the solution, and sent to a stripper where it is regenerated and the CO2 is released. At the same time that the excess nitrogen is condensed and removed, the remaining traces of CO, CH4 and most of the argon is removed. The gas is cooled and most of the excess steam is condensed before it enters the CO2 removal system. The excess nitrogen must then be removed prior to the synthesis to avoid loss of hydrogen. The exothermic reaction that takes place is:

N2 + 3H2 <——-> 2NH3

The equilibrium concentration favoring ammonia is at lower temperatures, but at lower temperatures a slow rate of reaction is observed. The ammonia that is formed is condenses and removed to an absorber, where the vaporized ammonia used as a refrigerant in the previous separator is recompressed to liquid ammonia. The process gas from the low-temperature shift converter contains mainly H2, N2, CO2 and the excess process steam. Therefore, two reactors are placed in parallel, and a recycle stream is introduced to help the single-pass conversion of approximately 25%. The gas first enters a high-temperature shift reactor along with steam to speed up the reaction rate.

Due to lower temperatures within the primary reactor, low conversion is accomplished. The gases that did not react are purged and sent back to the primary reformer.